JP2018155725A - Distance measuring device and distance measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable accurate distance calculation to be performed adopting communication type distance measurement that finds the distance between two devices by communication between each device.SOLUTION: A distance measuring device of an embodiment includes a calculation unit for calculating the distance between a first device and a second device at least one of which is movable, on the basis of phase information obtained by the first device and the second device, the first device including a first transmitter-receiver for transmitting three or more first carrier signals using the output of a first reference signal source and receiving three or more second carrier signals, the second device including a second transmitter-receiver for transmitting three or more second carrier signals using the output of a second reference signal source and receiving the three or more first carrier signals, the calculation unit calculating the distance on the basis of the phase detection result obtained by reception of the first and second carrier signals, and correcting the calculated distance on the basis of information pertaining to the amplitude ratio of one of the first carrier signals to the other that have been received by the second transmitter-receiver.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a distance measuring device and a distance measuring method.

  In recent years, keyless entry that facilitates locking and unlocking of vehicles has been adopted in many vehicles. This technology locks and unlocks a door using communication between a car key and the car. Furthermore, in recent years, smart entry systems that can lock / unlock door locks and start engines without touching the keys with smart keys have been adopted.

  However, there are many incidents where attackers infiltrate communication between keys and cars and steal cars. As a defensive measure against the above-described attack (so-called relay attack), a measure for measuring the distance between the key and the vehicle and prohibiting the control of the vehicle by communication when the distance is determined to be equal to or greater than a predetermined distance has been studied.

  There are many ranging techniques such as a two-frequency CW (Continuous Wave) system, an FM (Frequency Modulated) CW system, a Doppler system, and a phase detection system. In general, distance measurement provides a transmitter and a receiver in the same housing of a measuring device, applies radio waves emitted from the transmitter to the object, and detects the reflected wave from the measuring device to the object. To get the distance.

  However, in consideration of the relatively small reflection coefficient of the object and the limitation of output power by the radio wave method, the distance measuring technique using the reflected wave has a relatively small distance that can be measured, and the above-mentioned relay attack is not affected. It is not enough to use for countermeasures.

JP-A-8-166443

  An embodiment aims to provide a distance measuring apparatus and a distance measuring method that can employ communication-type distance measurement that obtains a distance between two devices by communication between the respective devices and enable calculation of an accurate distance. And

  The distance measuring device of the embodiment is a distance measuring device that calculates a distance based on carrier phase detection, and at least one of the first device and the first device based on phase information acquired by a first device and a second device that are movable. A calculation unit that calculates a distance between two devices, wherein the first device transmits a first reference signal source and three or more first carrier signals using outputs of the first reference signal source. And a second transceiver for receiving three or more second carrier signals, wherein the second device comprises a second reference signal source that operates independently of the first reference signal source, and the second A second transceiver that transmits the three or more second carrier signals using the output of the reference signal source and receives the three or more first carrier signals, and the calculating unit includes the second transmitter / receiver. Phase obtained by receiving first and second carrier signals Together on the basis of the output results to calculate the distance, the calculated distance is corrected based on the information of the amplitude ratio of the first carrier signals respectively received by the second transceiver.

1 is a block diagram showing a distance measuring system employing a distance measuring apparatus according to a first embodiment of the present invention. Explanatory drawing for demonstrating the principle of ranging by the phase detection system using a reflected wave, and its problem. Explanatory drawing for demonstrating the principle of ranging by the phase detection system using a reflected wave, and its problem. Explanatory drawing for demonstrating the problem of ranging by a phase detection system. Explanatory drawing for demonstrating the problem of ranging by a phase detection system. FIG. 2 is a circuit diagram illustrating an example of a specific configuration of a transmission unit 14 and a reception unit 15 in FIG. 1. FIG. 2 is a circuit diagram illustrating an example of a specific configuration of a transmission unit 24 and a reception unit 25 in FIG. 1. The flowchart for demonstrating ranging using two waves. Explanatory drawing for demonstrating the calculation method of the distance using a remainder system. Explanatory drawing for demonstrating the calculation method of the distance using a remainder system. Explanatory drawing which shows the example which takes distance on a horizontal axis and takes the phase on a vertical axis | shaft, and transmits the 3rd transmission wave from which angular frequency differs. Explanatory drawing for demonstrating the method of selecting the correct distance by the amplitude observation of the detected signal. The flowchart for demonstrating time series transmission / reception. Explanatory drawing for demonstrating time series transmission / reception. Explanatory drawing for demonstrating time series transmission / reception. Explanatory drawing for demonstrating time series transmission / reception. Explanatory drawing for demonstrating time series transmission / reception. Explanatory drawing for demonstrating time series transmission / reception. Explanatory drawing for demonstrating time series transmission / reception. Explanatory drawing for demonstrating time series transmission / reception. Explanatory drawing for demonstrating the problem by such a multipath environment in distance measurement. A graph showing the relationship between delay time τ ₁ and phase difference difference φ _L −φ _H with time on the horizontal axis and amplitude on the vertical axis. (80) equation, a graph showing the relationship between tau ₁ and (81) and Equation Δsum = ΔA _H0 + ΔA _L0. FIG. 19 is a graph for explaining the τ ₁ dependency of φ _L −φ _{H and} the τ ₁ dependency of Δsum / 4 = (ΔA _H0 + ΔA _L0 ) / 4 by the same display as in FIGS. The graph which shows distance error (DELTA) R without correction | amendment, and distance error (DELTA) R with correction | amendment. The flowchart for demonstrating operation | movement of 1st Embodiment. Explanatory drawing which shows the 2nd Embodiment of this invention. Explanatory drawing which shows the 2nd Embodiment of this invention. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. Explanatory drawing which shows various sequences. The flowchart which shows the operation | movement in the modification which considered multipath. Explanatory drawing which shows the relationship between a transmission sequence and the period which maintains an initial phase. Explanatory drawing which shows the carrier frequency used for ranging. The flowchart which shows a modification. FIG. 3 is an explanatory diagram showing a simplified example of the configuration of an oscillator 13, a transmission unit 14, and a reception unit 15 of the device 1. FIG. 4 is an explanatory diagram showing a simplified example of the configuration of an oscillator 23, a transmission unit 24, and a reception unit 25 of the device 2. FIG. 3 is an explanatory diagram showing a simplified example of the configuration of an oscillator 13, a transmission unit 14, and a reception unit 15 of the device 1. FIG. 4 is an explanatory diagram showing a simplified example of the configuration of an oscillator 23, a transmission unit 24, and a reception unit 25 of the device 2. FIG. 5 is a circuit diagram specifically showing an example of a circuit that generates signals to be supplied to multipliers TM11 and TM12 in FIG. FIG. 6 is a circuit diagram specifically showing an example of a circuit for generating signals to be supplied to multipliers TM21 and TM22 in FIG. FIG. 2 is a circuit diagram illustrating an example of a specific configuration of a transmission unit 14 and a reception unit 15 in FIG. 1. FIG. 2 is a circuit diagram illustrating an example of a specific configuration of a transmission unit 24 and a reception unit 25 in FIG. 1. FIG. 2 is a circuit diagram illustrating an example of a specific configuration of a transmission unit 14 and a reception unit 15 in FIG. 1. FIG. 2 is a circuit diagram illustrating an example of a specific configuration of a transmission unit 24 and a reception unit 25 in FIG. 1. FIG. 11B is a flowchart corresponding to FIG. 11A in which the second device transmits phase information to the first device. 40 is a flowchart showing an example corresponding to FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a block diagram showing a distance measuring system employing a distance measuring apparatus according to a first embodiment of the present invention.

  In this embodiment, an example will be described in which a phase detection method using an unmodulated carrier is employed, and communication-type distance measurement is used to obtain the distance between devices by communication between the devices. In a general phase detection method using a reflected wave, the distance that can be measured is relatively short as described above. Therefore, in the present embodiment, communication type distance measurement that performs communication between apparatuses is adopted. However, since each transmitter of each device operates independently, the initial phase of the transmission radio wave from each transmitter is different from each other, and the conventional phase detection method for obtaining the distance by the phase difference obtains an accurate distance. I can't. Therefore, in this embodiment, as will be described later, by transmitting the phase information obtained by reception of one device to the other device, it is possible to obtain an accurate distance in the other device. is there.

First, with reference to the explanatory diagrams of FIGS. 2A and 2B, the principle of distance measurement by the phase detection method using reflected waves and the problems thereof will be described.
(About the phase detection method)
In the phase detection method, signals of two frequencies shifted by an angular frequency from the central angular frequency ω _C1 are transmitted for distance measurement. In a distance measuring device using a reflected wave, a transmitter and a receiver are provided in the same casing, a transmission signal (radio wave) emitted from the transmitter is reflected on an object, and the reflected wave is received.

  2A and 2B show this state, and show that the radio wave emitted from the transmitter T is reflected by the wall W and received by the receiver S. FIG.

As shown in FIG. 2A, the angular frequency of the radio wave emitted from the transmitter is ω _C1 + ω _B1 and the initial phase is θ _1H . In this case, the transmission signal (transmission wave) tx1 (t) emitted from the transmitter is expressed by the following equation (1).
tx1 (t) = cos {(ω _C1 + ω _B1 ) t + θ _1H } (1)
This transmission signal arrives at an object (wall W) separated from the transmitter by a distance R with a delay time τ ₁ and is reflected and received by the receiver. Since the speed of the radio wave is the speed of light c (= 3 × 10 ⁸ m / s), τ ₁ = (R / c) (seconds). The signal received at the receiver has a delay 2τ ₁ with respect to the emitted signal. Therefore, the received signal (received wave) rx1 (t) of the receiver is expressed by the following equations (2) and (3).
rx1 (t) = cos {(ω _C1 + ω _B1 ) t + θ _1H −θ _{2 × Hτ 1} )} (2)
θ _{2 × Hτ1} = (ω _C1 + ω _B1 ) 2τ ₁ (3)
That is, the transmission signal is phase-shifted by the multiplication result (θ _{2 × Hτ1} ) of the delay time and the transmission angular frequency, and is received by the receiver.

Similarly, as shown in FIG. 2B, the transmission signal tx1 (t) and the reception signal rx1 (t) when the angular frequency ω _C1 −ω _B1 is used, and the initial phase is θ _1L and the following (4) to (6 ).
tx1 (t) = cos {(ω _C1 −ω _B1 ) t + θ _1L } (4)
rx1 (t) = cos {(ω _C1 −ω _B1 ) t + θ _1L −θ _{2 × Lτ 1} } (5)
θ _{2 × Lτ1} = (ω _C1 −ω _B1 ) 2τ ₁ (6)
The phase shift amount generated until the transmission signal of the angular frequency ω _C1 + ω _B1 is received is θ _H1 (t), and the phase shift amount generated until the transmission signal of the angular frequency ω _C1 −ω _B1 is received is θ _L1. Assuming that (t), the phase shift difference between the two received waves is given by the following equation (7) obtained by subtracting equation (6) from equation (3).
θ _H1 (t) −θ _L1 (t) = (θ _{2 × Hτ 1} −θ _{2 × Lτ 1} ) = 2ω _B1 × 2τ ₁ (7)
Here, τ ₁ = R / c. Since the difference frequency ω _B1 is known, if the difference between the phase shift amounts of the two received waves is measured, the distance R can be calculated from the measurement result.
R = c * ([theta] _{2 * H [tau] 1- [} theta] _{2 * L [ tau] 1} ) / (4 [omega] _B1 )
Can be calculated.

In the above description, the distance R is calculated considering only the phase information. Next, consideration is given to the amplitude when a transmission wave having an angular frequency ω _C1 + ω _B1 is used. The transmission wave shown in the above equation (1) is delayed by an amount of delay τ ₁ = R / c when reaching a target distant from the distance R, and the amplitude is attenuated by the attenuation L1 corresponding to the distance R. The reaching wave rx2 (t) shown in the equation (8) is obtained.
rx2 (t) = L ₁ cos {(ω _C1 + ω _B1 ) t + θ _1H − (ω _C1 + ω _B1 ) τ ₁ } (8)
Further, the transmitted wave is attenuated L _RFL when reflected from the object. The reflected wave tx2 (t) on the object is given by the following equation (9).
tx2 (t) = L _RFL L ₁ cos {(ω _C1 + ω _B1 ) t + θ _1H − (ω _C1 + ω _B1 ) τ ₁ } (9)
Since the received signal received by the receiver is rx1 (t) delayed from the object by a delay amount 1 = R / c (s) and the amplitude is attenuated by the attenuation L1 corresponding to the distance R, the following (10) Represented by an expression.
_{rx1 (t) = L 1 ×} L RFL × L 1 cos {(ω C1 + ω B1) t + θ 1H -2 (ω C1 + ω B1) τ 1} ... (10)
Thus, the transmission signal from the transmitter is attenuated by L ₁ × L _RFL × L ₁ before reaching the receiver. The signal amplitude that can be emitted from the transmitter in ranging needs to comply with the Radio Law according to the applied frequency. For example, at a specific frequency in the 920 MHz band, there is a restriction that suppresses transmission signal power to 1 mW or less. From the viewpoint of the signal-to-noise ratio of the received signal, it is necessary to suppress the attenuation received from transmission to reception in order to accurately measure the distance. However, as described above, the distance using the reflected wave has a relatively large attenuation, and therefore the distance that can be accurately measured is short.

Therefore, as described above, in the present embodiment, the attenuation is reduced by L _RFL × L ₁ by transmitting and receiving signals between the two apparatuses without using the reflected wave. The distance that can be accurately measured is expanded.

However, the two devices are separated from each other by a distance R and cannot share the same reference signal, and it is generally difficult to synchronize the transmission signal with a local oscillation signal used for reception. That is, not only does the signal frequency shift between the two devices, but the initial phase is unknown. Hereinafter, a problem in ranging when such an asynchronous transmission wave is used will be described.
(Issue when asynchronous)
In the distance measuring system according to the present embodiment, two devices (a first device and a second device) that emit carrier signals (transmission signals) asynchronously at the positions of the respective objects are arranged at the distance between the two objects. The distance R between these two devices is determined. In the present embodiment, a carrier signal having two frequencies shifted from the central angular frequency ω _C1 by the angular frequency ± ω _B1 is transmitted in the first device, and the angular frequency ± ω _B2 from the central angular frequency ω _C2 in the second device. A carrier signal having two frequencies shifted by a certain amount is transmitted.

3A and 3B are explanatory diagrams for explaining a problem when the above-described phase detection method is simply applied between the two devices A1 and A2. Assume that the device A2 receives the transmission signal of the device A1. The local oscillator of the device A1 generates a signal having a frequency necessary for generating two waves having a carrier angular frequency of the transmission wave of ω _C1 + ω _B1 and ω _C1 −ω _B1 by the heterodyne method, and the device A1 generates the angular frequency. Are transmitted. In addition, the local oscillator of the device A2 generates a signal having a frequency necessary for generating two waves having a transmission wave angular frequency of ω _C2 + ω _B2 and ω _C2 −ω _{B2 in} a heterodyne manner, and the device A2 is a local oscillator. It is assumed that heterodyne reception is performed using a signal from

Here, in order to correspond to the case where the reflected wave is used, the distance between transmission and reception is 2R. The initial phases of the transmission signal of angular frequency ω _C1 + ω _{B1 and} the transmission signal of angular frequency ω _C1 −ω _B1 from the device A1 are assumed to be θ _1H and θ _1L , respectively. Further, the initial phases of the two signals having the angular frequencies of the device A2 of ω _C2 + ω _B2 and ω _C2 −ω _B2 are θ _2H and θ _2L , respectively.

First, consider the phase of the transmission signal of angular frequency ω _C1 + ω _B1 . The device A1 outputs the transmission signal shown in the above equation (1). The reception signal rx2 (t) in the device A2 is given by the following equation (11).
rx2 (t) = cos {(ω _C1 + ω _B1 ) t + θ _1H −θ _{2 × Hτ 1} } (11)
In the device A2, the two signals cos {(ω _C2 + ω _B2 ) t + θ _2H } and sin {(ω _C2 + ω _B2 ) t + θ _2H } are multiplied by the received wave of the equation (11) to make the received wave in-phase. The component (I signal) and the quadrature component (Q signal) are separated and demodulated. The phase of the received wave (hereinafter referred to as the detection phase or simply the phase) can be easily obtained from the I and Q signals. That is, the detection phase θ _H1 (t) is expressed by the following equation (12). In the following equation (12), the harmonic term near the angular frequency ω _C1 + ω _C2 is omitted because it is removed during demodulation.
θ _H1 (t) = tan ⁻¹ (Q (t) / I (t)) = − {(ω _C1 −ω _C2 ) t + (ω _B1 −ω _B2 ) t + θ _1H −θ _2H −θ _{2 × Hτ 1} } (12)
Similarly, when a transmission signal having an angular frequency ω _C1 −ω _B1 is transmitted from the device A1, the detection phase θ _L1 (t) obtained from the I and Q signals obtained by the device A2 is given by the following equation (13). It is done. In the following equation (13), the harmonic term near the angular frequency ω _C1 + ω _C2 is omitted because it is removed during demodulation.
θ _L1 (t) = tan ⁻¹ (Q (t) / I (t)) = − {(ω _C1 −ω _C2 ) t− (ω _B1 −ω _B2 ) t + θ _1L −θ _2L −θ _{2 × Lτ 1} } ... (13)
A phase difference between these two detection phases (hereinafter referred to as a detection phase difference or simply a phase difference) θ _H1 (t) −θ _L1 (t) is expressed by the following equation (14).
θ _H1 (t) −θ _L1 (t) = − 2 (ω _B1 −ω _B2 ) t + (θ _1H −θ _1L ) − (θ _2H −θ _2L ) + (θ _{2 × Hτ1} −θ _{2 × Lτ1} ) ... (14)
In the conventional distance measuring device using the reflected wave, since the device A1 and the device A2 are the same device and share a local oscillator, the following equations (15) to (17) are satisfied. .
ω _B1 = ω _B2 (15)
θ _1H = θ _2H (16)
θ _1L = θ _2L (17)
When the equations (15) to (17) are established, the equation (14) is equal to the above-described equation (7), and the device is determined by the phase difference obtained by the I and Q demodulation processing on the received signal in the device A2. The distance R between A1 and apparatus A2 can be calculated.

However, since the devices A1 and A2 are provided apart from each other and the local oscillators operate independently of each other, the above equations (15) to (17) are not satisfied. In this case, unknown information such as the initial phase difference is included in the equation (14), and the distance cannot be calculated correctly.
(Basic distance measuring method of embodiment)
The above-mentioned two angular frequency signals transmitted by the first device are received by the second device to determine the phase of each signal, and the above-mentioned two angular frequency signals transmitted by the second device are received by the first device. Thus, the phase of each signal is obtained. Furthermore, phase information is transmitted from one of the first device and the second device to the other. In the present embodiment, as described later, basically, the phase difference between two signals obtained by reception of the first device and the phase difference between two signals obtained by reception of the second device are added. Thus, the distance R between the first device and the second device is obtained. The phase information may be I and Q signals, phase information obtained from the I and Q signals, or phase difference information obtained from two signals having different frequencies. Also good.
(Constitution)
In FIG. 1, the first device 1 (hereinafter also referred to as device 1) and the second device 2 (hereinafter also referred to as device 2) are spaced apart by a distance R. At least one of the apparatus 1 and the apparatus 2 is movable, and the distance R changes with this movement. The apparatus 1 is provided with a control unit 11. The control unit 11 controls each unit of the device 1. The control unit 11 may be configured by a processor using a CPU or the like, and may operate according to a program stored in a memory (not shown) to control each unit.

The oscillator 13 is controlled by the control unit 11 and generates oscillation signals (local signals) having two frequencies based on a built-in reference oscillator. Each oscillation signal from the oscillator 13 is supplied to the transmitter 14 and the receiver 15. The angular frequency of the oscillation signal generated by the oscillator 13 is set to an angular frequency necessary for generating three waves of ω _C1 + ω _B1 , ω _C1 −ω _B1 and ω _C1 as the angular frequency of the transmission wave of the transmission unit 14. The

The transmission unit 14 can be configured by, for example, a quadrature modulator. The transmission unit 14 is controlled by the control unit 11 to output three transmission waves of a transmission signal having an angular frequency of ω _C1 + ω _B1, a transmission signal having an angular frequency of ω _C1 −ω _B1 and an angular frequency of ω _C1. Can be done. A transmission wave from the transmission unit 14 is supplied to the antenna circuit 17.

  The antenna circuit 17 has one or more antennas, and can transmit a transmission wave from the transmission unit 14. The antenna circuit 17 receives a transmission wave from the device 2 to be described later and supplies a reception signal to the reception unit 15.

The receiving unit 15 can be constituted by, for example, an orthogonal demodulator. The receiving unit 15 is controlled by the control unit 11 to receive and demodulate the transmission wave from the device 2 using, for example, signals having the angular frequencies ω _C1 and ω _B1 from the oscillator 13, and the in-phase component of the reception wave (I signal) and quadrature component (Q signal) can be separated and output.

  The configuration of the device 2 is the same as that of the device 1. That is, the control unit 21 is provided in the second device. The control unit 21 controls each unit of the device 20. The control unit 21 may be configured by a processor using a CPU or the like, and may operate according to a program stored in a memory (not shown) to control each unit.

The oscillator 23 is controlled by the control unit 21 and generates an oscillation signal having two frequencies based on a built-in reference oscillator. Each oscillation signal from the oscillator 23 is supplied to the transmission unit 24 and the reception unit 25. The angular frequency of the oscillation signal generated by the oscillator 23 is set to an angular frequency necessary for generating two waves of ω _C2 + ω _B2 and ω _C2 −ω _B2 as the angular frequency of the transmission wave of the transmission unit 24.

The transmission unit 24 can be configured by, for example, a quadrature modulator. The transmission unit 24 is controlled by the control unit 21 to be able to output two transmission waves of a transmission signal having an angular frequency of ω _C2 + ω _{B2 and} a transmission signal having an angular frequency of ω _C2 −ω _B2. Yes. A transmission wave from the transmission unit 24 is supplied to the antenna circuit 27.

  The antenna circuit 27 has one or more antennas, and can transmit a transmission wave from the transmission unit 24. The antenna circuit 27 receives a transmission wave from the device 1 and supplies a reception signal to the reception unit 25.

The receiving unit 25 can be constituted by, for example, a quadrature demodulator. The receiving unit 25 is controlled by the control unit 21 to receive and demodulate the transmission wave from the apparatus 1 using, for example, the signals having the angular frequencies ω _C2 and ω _B2 from the oscillator 23, and the in-phase component of the reception wave (I signal) and quadrature component (Q signal) can be separated and output.

  FIG. 4 is a circuit diagram showing an example of a specific configuration of the transmission unit 14 and the reception unit 15 in FIG. FIG. 5 is a circuit diagram showing an example of a specific configuration of the transmission unit 24 and the reception unit 25 in FIG. 4 and 5 show an image suppression type transceiver, the present invention is not limited to this configuration.

The configuration of the image suppression method is known, and the feature is that when a higher angular frequency band is demodulated around the local angular frequency for high frequency, here ω _C1 or ω _C2 , the lower angular frequency band The signal is attenuated, and when demodulating the lower angular frequency band, the signal in the higher angular frequency band is attenuated. This filtering effect is due to signal processing. The same applies to transmission. When demodulating a higher angular frequency band around ω _C1 or ω _C2 , sin (ω _B1 t + θ _B1 ) or sin (ω _B2 t + θ _B2 ) in FIGS. 4 and 5 is used, and a lower angular frequency band is used. When demodulating, −sin (ω _B1 t + θ _B1 ) or −sin (ω _B2 t + θ _B2 ) is used in FIGS. 4 and 5. This frequency change determines the frequency band to be demodulated.

In the image suppression type receiver, the harmonic term near the angular frequency ω _C1 + ω _C2 is removed at the time of demodulation, so this term is omitted in the following calculation.

The transmission unit 14 includes multipliers TM11 and TM12 and an adder TS11. Multipliers TM11 and TM12 are supplied with oscillation signals from the oscillator 13 with an angular frequency of ω _C1 and phases different from each other by 90 degrees. The multipliers TM11 and TM12 are supplied with oscillation signals having an angular frequency of ω _B1 and phases different from each other by 90 degrees. The multiplier TM12 is also supplied with an inverted signal of the oscillation signal having an angular frequency of ω _B1 from the oscillator 13.

  Multipliers TM11 and TM12 each multiply two inputs and provide the multiplication result to adder TS11. The adder TS11 adds the outputs of the multipliers TM11 and TM12 and outputs the addition result as a transmission wave tx1.

The receiving unit 15 includes multipliers RM11 to RM16 and adders RS11 and RS12. The multipliers RM11 and RM12 receive the transmission wave of the device 2 via the antenna circuit 17 as a reception signal rx1. Multipliers RM11 and RM12 are respectively supplied with oscillation signals from the oscillator 13 whose angular frequency is ω _{C1 and} whose phases are different from each other by 90 degrees. Multiplier RM11 multiplies the two inputs and gives the multiplication result to multipliers RM13 and RM14, and multiplier RM12 multiplies the two inputs and gives the multiplication result to multipliers RM15 and RM16.

Multipliers RM13 and RM15 are supplied with an oscillation signal having an angular frequency (baseband local angular frequency) of ω _B1 from the oscillator 13. The multiplier RM13 multiplies the two inputs and gives the multiplication result to the adder RS11, and the multiplier RM14 multiplies the two inputs and gives the multiplication result to the adder RS12.

The multipliers RM14 and RM16 are supplied from the oscillator 13 with an oscillation signal having an angular frequency of ω _B1 or a signal orthogonal to the oscillation signal of ω _B1 given to the multiplier RM13 by its inverted signal. Multiplier RM14 multiplies the two inputs and gives the multiplication result to adder RS12, and multiplier RM16 multiplies the two inputs and gives the multiplication result to adder RS11.

  The adder RS11 adds the outputs of the multipliers RM13 and RM16 and outputs the subtraction result as an I signal. The adder RS12 adds the outputs of the multipliers RM14 and RM15 and outputs the addition result as a Q signal. The I and Q signals from the receiving unit 15 are supplied to the control unit 11.

4 and 5 show the same circuit. That is, in FIG. 5, the configurations of multipliers TM21, TM22, RM21 to RM26 and adders TS21, RS21, and RS22 are the configurations of multipliers TM11, TM12, RM11 to RM16, and adders TS11, RS11, and RS12 of FIG. It is the same. Since the frequency and phase of the oscillation signal of the oscillator 23 are different from those of the oscillator 13, in FIG. 5, the baseband local angular frequency ω _B2 is input instead of the angular frequency ω _B1 of FIG. 4, and the angular frequency ω of FIG. _The only difference is that ω _C2 is input instead of _C1 . The I and Q signals from the receiving unit 25 are supplied to the control unit 21.

In the present embodiment, the control unit 11 of the apparatus 1 controls the transmission unit 14 to transmit two transmission waves having angular frequencies ω _C1 + ω _B1 and ω _C1 −ω _B1 via the antenna circuit 17. .

On the other hand, the control unit 21 of the apparatus 2 controls the transmission unit 24 to transmit two transmission waves having angular frequencies ω _C2 + ω _B2 and ω _C2 −ω _B2 via the antenna circuit 27.

  The control unit 11 of the device 1 controls the receiving unit 15 to receive two transmission waves from the device 2 and acquire I and Q signals, respectively. The control unit 11 obtains the difference between the two phases obtained from the I and Q signals respectively obtained from the two received signals.

  Similarly, the control unit 21 of the device 2 controls the reception unit 25 to receive two transmission waves from the device 1 and acquire I and Q signals, respectively. The control unit 21 also obtains the difference between the two phases obtained from the I and Q signals obtained from the two received signals.

  In this Embodiment, the control part 11 of the apparatus 1 gives the phase information based on the acquired I and Q signal to the transmission part 14, and makes it transmit. As described above, the phase information may be, for example, a predetermined initial value or an I or Q signal obtained from two received signals, and phase information obtained from these I and Q signals. Or information on the difference between these phases.

For example, the control unit 11 may transmit the phase information by generating I and Q signals based on the phase information of the received signal having the angular frequency ω _B2 and supplying the signals to the multipliers TM11 and TM12, respectively. .

The control unit 11, the time of transmission of the oscillation signal of the angular frequency omega _B1, I the angular frequency obtained by adding the phase information of the received signal of the initial phase to the angular frequency omega _B2 of the oscillation signal of the omega _B1, generating a Q signal Then, the phase information may be transmitted by supplying the multipliers TM11 and TM12 respectively.

The receiving unit 25 of the device 2 receives the phase information transmitted from the transmitting unit 14 via the antenna circuit 27. The receiving unit 25 demodulates the received signal to obtain I and Q signals of phase information. The I and Q signals are supplied to the control unit 21. The control unit 21 obtains a value including the phase difference acquired by the control unit 11 of the apparatus 1 based on the phase information from the reception unit 25. The control unit 21 serving as a calculation unit adds the phase difference obtained from the reception result of the reception unit 25 and the phase difference based on the phase information transmitted from the device 2, whereby the first device 1 and the second device 2. The distance R between is calculated.
(Explanation of distance measurement using two waves)
Next, the operation of such a distance measuring system using two waves will be described with reference to the flowchart of FIG. FIG. 6 shows the operation of the device 1 on the left side and the operation of the device 2 on the right side. In FIG. 6, an arrow connecting the steps of the devices 1 and 2 indicates that communication is performed between the devices 1 and 2. Steps S4, S5, S14, and S15 are executed almost simultaneously.

  In step S1, the control unit 11 of the apparatus 1 determines whether or not there is an instruction to start ranging, and if there is an instruction to start ranging, controls the oscillator 13 to start outputting a necessary oscillation signal. Further, in step S11, the control unit 21 of the apparatus 2 determines whether or not there is an instruction to start ranging, and if there is an instruction to start ranging, controls the oscillator 23 to start outputting a necessary oscillation signal. .

  As will be described later, the control unit 11 ends the oscillation in step S9, and the control unit 21 ends the oscillation in step S20. Control of the start and end of oscillation in the control units 11 and 21 indicates that the oscillations of the oscillators 13 and 23 are not stopped during the transmission and reception periods for distance measurement. The end timing is not limited to the flow of FIG. During the period in which the oscillation of the oscillators 13 and 23 continues, the initial phase of each of the oscillators 13 and 23 is not newly set.

  The control unit 11 of the device 1 generates two transmission signals in step S3 and transmits these transmission signals from the antenna circuit 17 as transmission waves (step S4). Moreover, the control part 21 of the apparatus 2 produces | generates two transmission signals in step S13, and transmits these transmission signals from the antenna circuit 27 as a transmission wave (step S14).

It is assumed that the initial phase of the oscillation signal having the frequency ω _C1 output from the oscillator 13 of the apparatus 1 is θ _C1 and the initial phase of the oscillation signal having the frequency ω _B1 is θ _B1 . As described above, these initial phases θ _C1 and θ _B1 are not newly set as long as the oscillation of the oscillator 13 continues.

It is assumed that the initial phase of the oscillation signal having the frequency ω _C2 output from the oscillator 23 of the device 2 is θ _C2 and the initial phase of the oscillation signal having the frequency ω _B2 is θ _B2 . These initial phases θ _C2 and θ _B2 are not newly set as long as the oscillation of the oscillator 23 continues.

When two-frequency simultaneous transmission and simultaneous reception are assumed, the apparatus 1 requires two radio units in FIG. 4 and the apparatus 2 requires two radio units in FIG. Alternatively, a radio such as a superheterodyne method is used. However, the same oscillator is used for each oscillator.
(Transmission / reception of transmission wave with angular frequency ω _C1 + ω _B1 from device 1)
Two transmission waves having angular frequencies ω _C1 + ω _B1 and ω _C1 −ω _B1 are output from the device 1 by the multipliers TM11 and TM12 and the adder TS11 constituting the transmission unit 14. A transmission signal tx1 (t) having an angular frequency of ω _C1 + ω _B1 is expressed by the following equation (18).
tx1 (t) = cos (ω _C1 t + θ _C1 ) cos (ω _B1 t + θ _B1 ) −sin (ω _C1 t + θ _C1 ) sin (ω _B1 t + θ _B1 )
= Cos {(ω _C1 + ω _B1 ) t + θ _C1 + θ _B1 } (18)
When the distance between the devices 1 and 2 is R, and the delay until the transmission wave from the device 1 is received by the device 2 is τ ₁ , the received signal rx2 (t) of the device 2 is expressed by the following (19), It can be shown by the equation (20).
rx2 (t) = cos {(ω _C1 + ω _B1 ) (t−τ ₁ ) + θ _C1 + θ _B1 }
= Cos {(ω _C1 + ω _B1 ) t + θ _C1 + θ _B1 −θ _τH1 } (19)
θ _τH1 = (ω _C1 + ω _B1 ) τ ₁ (20)
The reception signal rx2 (t) is received by the antenna circuit 27 and supplied to the reception unit 25. In the receiver of FIG. 5, the received signal rx2 (t) is input to multipliers RM21 and RM22. Next, the signal at each node of the receiver of FIG. The outputs of the multipliers RM21, RM23, RM24 are I ₁ (t), I ₂ (t), I ₃ (t), respectively, and the outputs of the multipliers RM22, RM26, RM25 are Q ₁ (t), Q ₂ ( t) and Q ₃ (t), and the outputs of the adders RS21 and RS22 are I (t) and Q (t), respectively. These outputs are shown by the following equations (21) to (26).
I ₁ (t) = cos (ω _C2 t + θ _C2 ) × cos {(ω _C1 + ω _B1 ) t + θ _C1 + θ _B1 −θ _τH1 } (21)
Q ₁ (t) = sin (ω _C2 t + θ _C2 ) × cos {(ω _C1 + ω _B1 ) t + θ _C1 + θ _B1 −θ _τH1 } (22)
I ₂ (t) = I ₁ (t) × cos (ω _B2 t + θ _B2 ) (23)
Q ₂ (t) = Q ₁ (t) × sin (ω _B2 t + θ _B2 ) (24)
I ₃ (t) = I ₁ (t) × sin (ω _B2 t + θ _B2 ) (25)
Q ₃ (t) = Q ₁ (t) × cos (ω _B2 t + θ _B2 ) (26)
The output I (t) of the adder RS21 is I (t) = I ₂ (t) + Q ₂ (t), and the output Q (t) of the adder RS22 is Q (t) = I ₃ (t) -Q is a ₃ (t). The phase θ _H1 (t) obtained from these I (t) and Q (t) is expressed by the following (27).
θ _H1 (t) = tan ⁻¹ (Q (t) / I (t)) = − {(ω _C1 −ω _C2 ) t + (ω _B1 −ω _B2 ) t + θ _C1 −θ _C2 + θ _B1 −θ _B2 −θ _τH1 } (27)
(Transmission / reception of transmission wave with angular frequency ω _C2 + ω _B2 from device 2)
Similarly, when the signal tx2 (t) of the angular frequency ω _C2 + ω _B2 transmitted from the device 2 is received by the device 1 after the delay τ ₂ , I (t) and Q (t) detected by the device 1 A phase θ _H2 (t) obtained from the signal is obtained.
tx2 (t) = cos (ω _C2 t + θ _C2 ) cos (ω _B2 t + θ _B2 ) −sin (ω _C2 t + θ _C2 ) sin (ω _B2 t + θ _B2 )
= Cos {(ω _C2 + ω _B2 ) t + θ _C2 + θ _B2 } (28)
rx1 (t) = cos {(ω _C2 + ω _B2 ) (t−τ ₂ ) + θ _C2 + θ _B2 }
= Cos {(ω _C2 + ω _B2 ) t + θ _C2 + θ _B2 −θ _τH2 } (29)
θ _τH2 = (ω _C2 + ω _B2 ) τ ₂ (30)
The reception signal rx1 (t) is received by the antenna circuit 17 and supplied to the reception unit 15. In the receiver of FIG. 4, the received signal rx1 (t) is input to multipliers RM11 and RM12. Next, the signal at each node of the receiver of FIG. 4 is calculated sequentially. The outputs of the multipliers RM11, RM13, RM14 are I ₁ (t), I ₂ (t), I ₃ (t), respectively, and the outputs of the multipliers RM12, RM16, RM15 are Q ₁ (t), Q ₂ ( t) and Q ₃ (t), and the outputs of the adders RS11 and RS12 are I (t) and Q (t), respectively. These outputs are shown by the following equations (31) to (36).
I ₁ (t) = cos (ω _C1 t + θ _C1 ) × cos {(ω _C2 + ω _B2 ) t + θ _C2 + θ _B2 −θ _τH2 } (31)
Q ₁ (t) = sin (ω _C1 t + θ _C1 ) × cos {(ω _C2 + ω _B2 ) t + θ _C2 + θ _B2 −θ _τH2 } (32)
I ₂ (t) = I ₁ (t) × cos (ω _B1 t + θ _B1 ) (33)
Q ₂ (t) = Q ₁ (t) × sin (ω _B1 t + θ _B1 ) (34)
I ₃ (t) = I ₁ (t) × sin (ω _B1 t + θ _B1 ) (35)
Q ₃ (t) = Q ₁ (t) × cos (ω _B1 t + θ _B1 ) (36)
The output I (t) of the adder RS11 is I (t) = I ₂ (t) + Q ₂ (t), and the output Q (t) of the adder RS12 is Q (t) = I ₃ (t) -Q is a ₃ (t). The phase θ _H2 (t) = tan ⁻¹ (Q (t) / I (t)) obtained from these I (t) and Q (t) is expressed by the following (37).
_θH2 (t) = (ω _C1 −ω _C2 ) t + (ω _B1 −ω _B2 ) t + θ _C1 −θ _C2 + θ _B1 −θ _B2 + θ _τH2 (37)
(Transmission / reception of transmission wave with angular frequency ω _C1 −ω _B1 from device 1)
Next, the same calculation is performed on the signal tx1 (t) of the angular frequency ω _C1 −ω _B1 transmitted from the device 1.
tx1 (t) = cos (ω _C1 t + θ _C1 ) cos (ω _B1 t + θ _B1 ) + sin (ω _C1 t + θ _C1 ) sin (ω _B1 t + θ _B1 )
= Cos {(ω _C1 −ω _B1 ) t + θ _C1 −θ _B1 } (38)
It becomes. Since the distance between the devices 1 and 2 is R and the delay time is τ ₁ , the received signal rx2 (t) in the device 2 is given by the following equations (39) and (40).
rx2 (t) = cos {(ω _C1 −ω _B1 ) (t−τ ₁ ) + θ _C1 −θ _B1 }
= Cos {(ω _C1 −ω _B1 ) t + θ _C1 −θ _B1 −θ _τL1 } (39)
θ _τL1 = (ω _C1 −ω _B1 ) τ ₁ (40)
The signal of each node of the apparatus 2 can be expressed by the following equations (43) to (47).
I ₁ (t) = cos (ω _C2 t + θ _C2 ) × cos {(ω _C1 −ω _B1 ) t + θ _C1 −θ _B1 −θ _τL1 } (41)
Q ₁ (t) = sin (ω _C2 t + θ _C2 ) × cos {(ω _C1 −ω _B1 ) t + θ _C1 −θ _B1 −θ _τL1 } (42)
I ₂ (t) = I ₁ (t) × cos (ω _B2 t + θ _B2 ) (43)
Q ₂ (t) = Q ₁ (t) × −sin (ω _B2 t + θ _B2 ) (44)
I ₃ (t) = I ₁ (t) × −sin (ω _B2 t + θ _B2 ) (45)
Q ₃ (t) = Q ₁ (t) × cos (ω _B2 t + θ _B2 ) (46)
Detected by the device 2 from I (t) = I ₂ (t) −Q ₂ (t) obtained from the adder RS21 and Q (t) = I ₃ (t) + Q ₃ (t) obtained from the adder RS22 The phase θ _H1 (t) = tan ⁻¹ (Q (t) / I (t)) is given by the following equation (47).
θ _L1 (t) = tan ⁻¹ (Q (t) / I (t)) = − {(ω _C1 −ω _C2 ) t− (ω _B1 −ω _B2 ) t + θ _C1 −θ _C2 − (θ _B1 −θ _B2 ) −θ _τL1 } (47)
(Transmission / reception of a transmission wave having an angular frequency ω _C2 −ω _B2 from the device 2)
Similarly, when the signal tx2 (t) of the angular frequency ω _C2 −ω _B2 transmitted from the device 2 is received by the device 1 after the delay _τ 2, I (t) and Q (t detected by the device 1 ) _{Determine the} phase θ _L2 (t) obtained from the signal.
tx2 (t) = cos (ω _C2 t + θ _C2 ) cos (ω _B2 t + θ _B2 ) + sin (ω _C2 t + θ _C2 ) sin (ω _B2 t + θ _B2 )
= Cos {(ω _C2 −ω _B2 ) t + θ _C2 −θ _B2 } (48)
rx1 (t) = cos {(ω _C2 −ω _B2 ) (t−τ ₂ ) + θ _C2 −θ _B2 }
= Cos {(ω _C2 −ω _B2 ) t + θ _C2 −θ _B2 −θ _τL2 } (49)
θ _τL2 = (ω _C2 −ω _B2 ) τ ₂ (50)
The signal of each node of the device 1 can be expressed by the following equations (53) to (57).
I ₁ (t) = cos (ω _C1 t + θ _C1 ) × cos {(ω _C2 −ω _B2 ) t + θ _C2 −θ _B2 −θ _τL2 } (51)
Q ₁ (t) = sin (ω _C1 t + θ _C1 ) × cos {(ω _C2 −ω _B2 ) t + θ _C2 −θ _B2 −θ _τL2 } (52)
I ₂ (t) = I ₁ (t) × cos (ω _B1 t + θ _B1 ) (53)
Q ₂ (t) = Q ₁ (t) × −sin (ω _B1 t + θ _B1 ) (54)
I ₃ (t) = I ₁ (t) × −sin (ω _B1 t + θ _B1 ) (55)
Q ₃ (t) = Q ₁ (t) × cos (ω _B1 t + θ _B1 ) (56)
Device 1 detects from I (t) = I ₂ (t) −Q ₂ (t) obtained from adder RS11 and Q (t) = I ₃ (t) + Q ₃ (t) obtained from adder RS12 The phase θ _H1 (t) = tan ⁻¹ (Q (t) / I (t)) to be given is given by the following equation (57).
θ _L2 (t) = (ω _C1 −ω _C2 ) t− (ω _B1 −ω _B2 ) t + θ _C1 −θ _C2 − (θ _B1 −θ _B2 ) + θ _τL2 (57)
The control unit 11 of the apparatus 1 acquires the I and Q signals received by the receiving unit 15 in step S6 of FIG. 6, and in step S7, the phase θ _τH1 (t) shown in the above equations (27) and (47). And θ _τL1 (t) are calculated. Further, the control unit 21 of the apparatus 2 acquires the I and Q signals received by the receiving unit 25 in step S16 of FIG. 6, and in step S17, the phase _θτH2 (shown in the above equations (37) and (57)) is _obtained. t) and θ _τL2 (t) are calculated.

  The control unit 11 gives the acquired phase information to the transmission unit 14 for transmission (step S8). For example, the control unit 11 supplies I and Q signals based on the phase information instead of the oscillation signals supplied to the multipliers TM11 and TM12 in FIG. Note that another transmitter for transmitting phase information may be used.

  The control unit 21 of the device 2 receives the phase information from the device 1 in step S18. As described above, the phase information may be the I and Q signals from the receiving unit 15 of the apparatus 1 or the phase information obtained from the I and Q signals. It may be information on a phase difference.

In step S <b> 19, the control unit 21 calculates the distance by performing the following equation (58). The following equation (58) adds the difference between the equations (27) and (47) and the difference between the equations (37) and (57).
{Θ _H1 (t) −θ _L1 (t)} + {θ _H2 (t) −θ _L2 (t)} = (θ _τH1− θ _τL1 ) + (θ _τH2− θ _τL2 ) (58)
Further, the following formulas (59) and (60) are established.
_{θ τH1 -θ τL1 = (ω C1} + ω B1) τ 1 - (ω C1 -ω B1) τ 1
= 2ω _B1 τ ₁ (59)
_{θ τH2 -θ τL2 = (ω C2} + ω B2) τ 2 - (ω C2 -ω B2) τ 2
= 2ω _B2 τ ₂ (60)
Further, since the radio wave delays τ ₁ and τ 2 between the devices 1 and ₂ are the same regardless of the traveling direction, the following equation (61) is obtained from the equation (58).
{Θ _H1 (t) −θ _L1 (t)} + {θ _H2 (t) −θ _L2 (t)} = (θ _τH1 −θ _τL1 ) + (θ _τH2 −θ _τL2 )
= 2 × (ω _B1 + ω _B2 ) τ ₁ (61)
The above equation (61) is a value proportional to twice the distance R by the addition of the two-frequency phase difference based on the I and Q signals detected by the device 2 and the two-frequency phase difference detected by the device 1 and the I and Q signals. Indicates that is required. The angular frequency ω _B1 due to the oscillator 13 of the device 1 and the angular frequency ω _B2 due to the oscillator 13 of the device 2 can generally be matched with an error of the order of several tens of ppm. Therefore, the calculation of the distance R by the above equation (61) can be obtained with a resolution of at least about 1 m.

The control unit 11 stops the oscillator 13 in step S9, and the control unit 21 stops the oscillator 23 in step S20. As described above, the control units 11 and 21 may continue oscillation during the transmission and reception periods in steps S4, S5, S14, and S15, and the oscillation start and end timings of the oscillators 13 and 23 are shown in FIG. It is not limited to examples.
(Calculation of distance by remainder of 2π)
By the way, when the phase difference detected by the apparatus 1 and the apparatus 2 is added, the result may be −π (rad) or less, or may be larger than π (rad). In this case, the correct distance R with respect to the detected phase can be obtained by taking a remainder of 2π.

  7 and 8 are explanatory diagrams for explaining a distance calculation method using a residue system.

For example, when R = 11 m and ω _B1 = ω _B2 = 2π × 5M, the detected phase difference Δθ ₁₂ obtained by the device 1 and the detected phase difference Δθ ₂₁ obtained by the device 2 are expressed by the following equation (62) and (63) It shall be shown to a formula.
Δθ ₁₂ = θ _τH1 −θ _τL1 = −1.88849 (62)
Δθ ₂₁ = θ _τH2 −θ _τL2 = −6.0737 (63)
The following formula (61a) is obtained from the above formula (61).

(1/2) [{Δθ ₁₂ } + {Δθ ₂₁ }] = (ω _B1 + ω _B2 ) (R / c) (61a)
FIG. 7 shows the phase relationship of the above equations (62) and (63). The phase of the sum of Δθ ₂₁ indicated by the innermost arrow that rotates clockwise with reference to the phase of 0 ° and Δθ ₁₂ indicated by the second arrow from the inside is the addition of + Δθ ₂₁ indicated by the third arrow from the inner side. This is shown in the phase (dashed thick line) obtained by adding only the minutes (broken line). The half angle of this phase is the phase of the thick line indicated by the outermost arrow.

From the equation (61a), −0.3993 = (ω _B1 + ω _B2 ) (R / c). When this equation is solved, R = −19 m, and since the detected phase difference is larger than −π (rad), it can be seen that the distance cannot be obtained correctly.

Therefore, in this embodiment, in such a case, as shown in FIG. 8, both Δθ ₁₂ and Δθ ₂₁ are added by 2π for calculation. That is, the phase of the sum of 2π + Δθ ₂₁ indicated by the innermost arrow rotating counterclockwise with respect to the phase 0 degree and 2π + Δθ ₁₂ indicated by the second arrow from the inside is + Δθ indicated by the third arrow from the inner side. _This is shown in a phase (dashed thick line) obtained by adding ₂₁ added parts (broken line). The half angle of this phase is the phase of the thick line indicated by the outermost arrow.

2π + (Δθ ₁₂ + Δθ ₂₁ ) /2=2.3088, and R = 11 m is obtained from the equation (61a).

From the above, in the present embodiment, when adding the detection phase difference, the distance R may be obtained by taking a remainder of 2π. Note that the method of using the remainder of 2π in the phase addition can be similarly applied to other examples described later.
(Select from multiple distance candidates)
By the way, since a detected phase difference exceeding 2π cannot be detected, there are a plurality of distance candidates for the calculated detected phase difference. As a method of selecting a correct distance from a plurality of distance candidates, there are a method of transmitting a third transmission wave having different angular frequencies and a method of determining based on received power.

  FIG. 9 is an explanatory diagram illustrating an example in which a third transmission wave having a different angular frequency is transmitted with the distance on the horizontal axis and the phase on the vertical axis.

From the above equation (61), the following equation (64) is obtained.
(1/2) × {( _{θτH1− θτL1} ) + ( _{θτH2− θτL2} )} = (ω _B1 + ω _B2 ) × (R / c) (64)
When the left-hand side referred to as theta _det, relationship between the distance R and theta _det is as shown in solid line in FIG. However, the sum θ _det of the detection phase differences calculated by the above equation (64) can take a value other than between −π (rad) and π (rad), but the sum θ _det of the detection phase differences is It is converted between −π (rad) and π (rad). This is because the phase angle is generally displayed within the range [−π (rad), π (rad)].

Referring to FIG. 9, there are R ₁ , R ₂ , and R ₃ as distance candidates based on the sum of detected phase differences θ _det . Here, the sum θ _det of detected phase differences is a result of addition / subtraction of phases obtained by transmission / reception of each transmission wave of angular frequencies ω _C1 + ω _B1 , ω _C1 −ω _B1 , ω _C2 + ω _B2 , ω _C2 −ω _B2. However, a phase addition / subtraction result obtained by transmission / reception of transmission waves of angular frequencies ω _C1 + ω _B1 / Q and ω _C2 + ω _B2 / Q is newly considered. However, Q is a rational number that satisfies the following expression (65).
Q> 1 (65)
The relationship between the detected phase at the new angular frequency and the distance R can be shown by the broken line in FIG. In order to select the correct distance from the distance candidates R _{1 to} R _3, the detection phase result obtained at the new angular frequency is referred to. That is, if θ _det 1 is detected, the distance R ₁ is determined, and if θ _det 2 is detected, the distance R ₂ is determined. Note that the inspection by the phase wrapping described above is unnecessary if the radio wave coverage is kept small. In the above description, transmission of three different frequencies has been described, but the same thing can be realized by transmitting three or more different frequencies.

  Next, a method of selecting the correct distance by observing the amplitude of the signal detected with reference to the explanatory diagram of FIG.

In the above equation (8), it has been described that the amplitude is attenuated by the attenuation L ₁ according to the distance R, but propagation attenuation in free space is expressed by the following equation (66).
L ₁ = (λ / 4πR) ² (66)
Here, λ is a wavelength. According to the equation (66), the attenuation L ₁ is large when the distance R is large, and the attenuation L ₁ is small when the distance R is small. FIG. 10 shows this relationship. 1 antenna gain of the transmitting and receiving, is given by assuming the transmission power _{P 0,} respectively received power _{P 2} at the receiving power _{P 1} and the distance _{R 2} at range _{R 1} is the following (67) or (68) below .
P ₁ = (λ / 4πR ₁ )) ² × P ₀ (67)
P ₂ = (λ / 4πR ₂ )) ² × P ₀ (68)
The distances R ₁ and R ₂ can be distinguished from the sum θ _{det of the} received power and the detected phase difference.

  In this case, reliable distance measurement is possible by using a 2π remainder in the phase addition.

As described above, in the present embodiment, basically, two transmission waves are employed in each of the first device and the second device, and signals of two angular frequencies are respectively transmitted from the first device and the second device. While transmitting to the device and the first device, two phases of two received signals having different angular frequencies are obtained in the first and second devices. Then, the obtained phase information is transmitted from one of the first device and the second device to the other. The device that has received the phase information has the oscillator of the first device and the second device based on the addition result of the phase difference between the two received signals received by the first device and the phase difference between the two received signals received by the second device. Regardless of the initial phase, the distance between the first device and the second device is accurately calculated. In this distance measuring system, accurate distance measurement is performed only by direct waves from the first device and the second device without using a reflected wave, and the distance that can be measured can be expanded.
(Problems in time series transmission / reception)
In the above description, assuming that the radio wave delays τ ₁ and τ ₂ are the same in the equation (58), the equation (61) for obtaining the distance from the addition of the detected phase difference is obtained. However, the equation (58) is an example when the transmission and reception processes are simultaneously performed in the devices 1 and 2.

  However, there are frequency bands where simultaneous transmission and reception are not possible due to the regulations of the Domestic Radio Law. For example, the 920 MHz band is an example. When distance measurement is performed in such a frequency band, transmission and reception must be performed in time series.

  FIG. 11A is a flowchart in time-series transmission / reception, and FIGS. 11B to 15 are explanatory diagrams for explaining problems and solutions in such time-series transmission / reception.

  When it is defined that only one wave can be transmitted and received between the devices 1 and 2 at the same time, it is necessary to perform transmission and reception of at least four waves necessary for ranging in time series. However, when time series transmission / reception is performed, a phase corresponding to a delay generated in time series is added to the detection phase, and the phase required for propagation cannot be obtained. The reason for this will be described by modifying the equation (58).

  6 are executed almost at the same time, but when transmitting and receiving one wave at a time, the broken line is as shown in FIG. 11A.

Similarly to the above description, in the devices 1 and 2 that are separated from each other by the distance R, the phase (shift amount) when the signal of the angular frequency ω _C1 + ω _B1 transmitted from the device 1 is detected by the device 2 is θ _H1. The phase when the signal of the angular frequency ω _C1 −ω _B1 transmitted from 1 is detected by the device 2 is θ _L1, and the phase when the signal of the angular frequency ω _C2 + ω _B2 transmitted from the device 2 is detected by the device 1 Let (shift amount) be θ _H2, and let θ _L2 be the phase when the device 1 detects the signal of the angular frequency ω _C2 −ω _B2 transmitted from the device 2.

Now, for example, the phase detection order is θ _H1 , θ _L2 , θ _H2 , θ _L1 . Further, as shown in FIGS. 11B and 11C, the transmission signals are transmitted / received with a time T offset. In this case, the following equation (120) is established by substituting time into (t) in the above equations (27), (37), (47), and (57), and modifying the above equation (58). To do.
{Θ _H1 (t) −θ _L1 (t + 3T)} + {θ _H2 (t + 2T) −θ _L2 (t + T)}
= ( _{ΘτH1− θτL1} ) + ( _{θτH2− θτL2} ) + (ω _C1 −ω _C2 ) 4T (120)
The final term of the above equation (120) is a phase added by time series transmission / reception. This added phase is the result of multiplying the error angular frequency of device 1 and device 2 and the delay 4T for the local angular frequency substantially the same as the angular frequency of the received RF (high frequency) signal. When the local frequency is 920 MHz, the frequency error is 40 ppm, and the delay T is 0.1 ms, the added phase is 360 ° × 14.7, and the error due to the added phase is too large to correctly measure the distance. I understand.

Next, the phase detection order is assumed to be θ _H1 , θ _L1 , θ _H2 , θ _L2 . 12A and 12B show an example of this case. In this case, the following equation (121) is obtained by modifying the following equation (58).
{Θ _H1 (t) −θ _L1 (t + T)} + {θ _H2 (t + 2T) −θ _L2 (t + 3T)}
= ( _{ΘτH1− θτL1} ) + ( _{θτH2− θτL2} ) + (ω _B1 −ω _B2 ) 4T (121)
The final term of the equation (121) is a phase added by time series transmission / reception. This added phase is a result of multiplying the error angular frequency of the devices 1 and 2 by the delay 4T with respect to the local angular frequency for baseband substantially the same as the low angular frequency of the received high-frequency signal. When the local frequency is 5 MHz, the frequency error is 40 ppm, and the delay T is 0.1 ms, 360 ° × 0.08 = 28.8 °, and it can be seen that the distance can be measured more accurately than in the previous example.

However, even in this case, whether or not the error is within an allowable error of the system specification depends on the system. This embodiment presents a time series procedure for reducing a distance error caused by time series transmission / reception. Note that this embodiment shows a procedure in consideration of transmission / reception regulations stipulated by the Radio Law.
(Specific steps)
First, consider the effect of transmission delay.

The above equation (58) is modified to obtain the following equation (122).
{Θ _H1 (t) + θ _H2 (t)} − {θ _L1 (t) + θ _L2 (t)} = (θ _τH1 + θ _τH2 ) − (θ _τL1 + θ _τL2 ) (122)
Where
θ _H1 (t) + θ _H2 (t) = θ _τH1 + θ _τH2 (123)
θ _L1 (t) + θ _L2 (t) = θ _τL1 + θ _τL2 (124)
It is.

In wireless communication, there is a rule that when a signal addressed to itself is received, it can be returned without carrier sense. Accordingly, after the transmission of the signal from the device 1 to the device 2 is completed, the device 2 returns the response to the device 1 immediately. To simplify the analysis, it is assumed that device 2 replies to transmission 1 after t ₀ after transmission by device 1. From the formulas (111) and (112), the following formula (125) is obtained.
θ _H1 (t) + θ _H2 (t + t ₀ ) = θ _τH1 + θ _τH2 + {(ω _B1 −ω _B2 ) + (ω _C1 −ω _C2 )} t ₀ (125)
The delay t ₀ is the shortest time in time series, and includes a time for transmitting a signal of the angular frequency ω _C1 + ω _B1 from the device 1 to the device 2, a transmission / reception timing margin, and a propagation delay. Right side, the third term, the fourth term becomes the phase error due to a delay t _0. The fourth term is particularly problematic due to the high frequency, which will be mentioned later.

Next, a delay T is further added to the left side of the equation (125). FIG. 13 shows such a transmission procedure. As shown in FIG. 13, the added value of the detected phase in this case is the same regardless of the addition of the delay T. Therefore, the following equation (126) is obtained.
θ _H1 (t + T) + θ _H2 (t + t ₀ + T) = θ _τH1 + θ _τH2 + {(ω _B1 −ω _B2 ) + (ω _C1 −ω _C2 )} t ₀ (126)
The right side of the equation (126) and the right side of the equation (125) are the same. That is, if the relative time difference is the same (T in the above example), the addition result of the phase received by the device 2 from the device 1 and the phase received by the device 1 from the device 2 is In spite of the delay T, it does not change. That is, the addition result of these phases is a value that does not depend on the delay T.

Next, the same applies to transmission / reception of the angular frequency ω _C1 -ω _B1 signal between the devices 1 and 2. That is, the following expressions (127) and (128) are obtained from the expressions (47) and (57).
θ _L1 (t) + θ _L2 (t + t ₀ ) = θ _τL1 + θ _τL2 + {− (ω _B1 −ω _B2 ) + (ω _C1 −ω _C2 )} t ₀ (127)
θ _L1 (t + T) + θ _L2 (t + t ₀ + T) = θ _τL1 + θ _τL2 + {− (ω _B1 −ω _B2 ) + (ω _C1 −ω _C2 )} t ₀ (128)
From the above consideration, consider a sequence in which an angular frequency ω _C1 −ω _B1 signal is transmitted and received after bidirectional transmission and reception of the angular frequency ω _C1 + ω _B1 . With reference to the transmission start time of the angular frequency ω _C1 + ω _B1 signal from the device 1, assuming that the transmission start time of the angular frequency ω _C1 −ω _B1 signal from the device 1 is T, the above formulas (125) and (128) Equation (129) is obtained. However, a _{T> t 0.}
θ _H1 (t) + θ _H2 (t + t ₀ ) − {θ _L1 (t + T) + θ _L2 (t + t ₀ + T)}
= Θ _τH1 −θ _τL1 + θ _τH2 −θ _τL2 +2 (ω _B1 −ω _B2 ) t ₀ (129)
The final term on the left side of the equation (129) is a phase error due to transmission delay. Delay error of a local frequency for the received high frequency is canceled by taking the difference between the angular frequency omega _{C1 +} omega _B1 signal and the angular frequency omega _C1 - [omega] _B1 signal. Therefore, the phase error is a product of the error of the shortest delay time t _{0 in} time series and the local angular frequency for baseband (for example, 2π × 5 MHz). Error if set to a small delay time t ₀ is reduced. Therefore, depending on the value of the delay time t ₀ , it can be said that distance measurement with no problem in accuracy is possible in actual use.

  Next, a method for removing the final term of the above equation (129) that is a factor of distance estimation error will be described.

From the above equations (27) and (37), the following equation (130) is obtained.
θ _H1 (t + t ₀ ) + θ _H2 (t) = θ _τH1 + θ _τH2 − {(ω _B1 −ω _B2 ) + (ω _C1 −ω _C2 )} t ₀ (130)
Even if a predetermined delay D is added to the left side of the expression (130), the value on the right side does not change as described above. Therefore, the following equation (131) is obtained.
θ _H1 (t + t ₀ + D) + θ _H2 (t + D) = θ _τH1 + θ _τH2 − {(ω _B1 −ω _B2 ) + (ω _C1 −ω _C2 )} t ₀ (131)
When the above formulas (125) and (131) are added, the following formula (132) is obtained.
θ _H1 (t) + θ _H2 (t + t ₀ ) + θ _H1 (t + t ₀ + D) + θ _H2 (t + D) = 2 (θ _τH1 + θ _τH2 ) (132)
The left side of FIG. 14 shows the state of the above expression (132). When D = t ₀ in this equation (132), the following equation (133) is obtained.
θ _H1 (t) + 2θ _H2 (t + t ₀ ) + θ _H1 (t + 2t ₀ ) = 2 (θ _τH1 + θ _τH2 ) (133)
The right side of the above equation (133) is only the term of the radio wave propagation delay corresponding to the distance not dependent on time.

From the above equations (47) and (57), the following equation (134) is obtained.
θ _L1 (t + t ₀ ) + θ _L2 (t) = θ _τL1 + θ _τL2 − {− (ω _B1 −ω _B2 ) + (ω _C1 −ω _C2 )} t ₀ (134)
Even if a predetermined delay D is added to the left side of the equation (134), the value on the right side does not change. Therefore, the following equation (135) is obtained.
θ _L1 (t + t ₀ + D) + θ _L2 (t + D) = θ _τL1 + θ _τL2 − {− (ω _B1 −ω _B2 ) + (ω _C1 −ω _C2 )} t ₀ (135)
When the above formula (127) and formula (135) are added, the following formula (136) is obtained.
θ _L1 (t) + θ _L2 (t + t ₀ ) + θ _L1 (t + t ₀ + D) + θ _L2 (t + D) = 2 (θ _τL1 + θ _τL2 ) (136)
In this equation (136), when D = t ₀ , the following equation (137) is obtained.
θ _L1 (t) + 2θ _L2 (t + t ₀ ) + θ _L1 (t + 2t ₀ ) = 2 (θ _τL1 + θ _τL2 (137)
The right side of the above expression (137) is only the term of the radio wave propagation delay corresponding to the distance not dependent on time.

Above (133) and (137) expression system and the phase detection a transmission signal 1 in the apparatus 2, and the phase detection in the transmission signal apparatus 1 of the device 2 after t _0, the transmission signal again device 1 after 2t ₀ Is a sequence for detecting the phase by the apparatus 2. Hereinafter, the transmission of the transmission signal of the apparatus 1 and the phase detection of the apparatus 2 corresponding thereto will be alternated with the transmission of the transmission signal of the apparatus 2 and the phase detection of the apparatus 1 corresponding thereto. The measurement is called “repetitive alternation”.

That is, each of the apparatuses 1 and 2 transmits and receives two carrier signals, and transmits again by repeatedly repeating the transmission and reception of the carrier signal at intervals of t ₀ from the apparatus 1 or 2 to the other apparatus. The order and time are limited, but accurate distance measurement without being time-dependent is possible.

Furthermore, depending on the transmission sequence of the carrier signal, even without repeatedly alternates t ₀ interval of precise distance measurement that is independent of time.

That is, even if a fixed delay T is added to the left side of the above equation (136), the right side is constant.
θ _L1 (t + T) + θ _L2 (t + t ₀ + T) + θ _L1 (t + t ₀ + D + T) + θ _L2 (t + D + T) = 2 (θ _τL1 + θ _τL2 ) (138)
The following equation (139) is obtained from the above equations (132) and (138).
θ _H1 (t) + θ _H2 (t + t ₀ ) + θ _H1 (t + t ₀ + D) + θ _H2 (t + D)
− {Θ _L1 (t + T) + θ _L2 (t + t ₀ + T) + θ _L1 (t + t ₀ + D + T) + θ _L2 (t + D + T)}
= 2 {( _{θτH1− θτL1} ) + ( _{θτH2− θτL2} )} = 4 × (ω _B1 + ω _B2 ) τ ₁ (139)
Above (139) expression After repeated alternating angular frequency omega _C1 + omega _B1, the round trip omega _C2 + omega _B2 at time intervals D, round-trip from the measurement start angular frequency omega _C1 - [omega] _B1 after T, ω _C2 -ω _B2 Shows a sequence that alternates repeatedly at time intervals D, and adopting this sequence eliminates the distance estimation error factor in the last term of the above equation (129) and enables accurate distance measurement. Show.

14 and 15 show this sequence. By measuring the phase in such a sequence, only the propagation delay component can be extracted. That is, the control unit 11 of the device 1 transmits a transmission wave (hereinafter referred to as a transmission wave H1A) having an angular frequency of ω _C1 + ω _B1 at a predetermined timing. The control unit 21 of the device 2 transmits a transmission wave having an angular frequency of ω _C2 + ω _B2 (hereinafter referred to as a transmission wave H2A) immediately after receiving the transmission wave H1A. Further, the control unit 21 of the device 2 transmits again the transmission wave having the angular frequency ω _C2 + ω _B2 (hereinafter referred to as the transmission wave H2B) after the transmission wave H2A is transmitted. After receiving the second transmission wave H2B, the control unit 11 of the apparatus 1 transmits a transmission wave having an angular frequency of ω _C1 + ω _B1 (hereinafter referred to as a transmission wave H1B) again.

Further, the control unit 11 transmits a transmission wave having an angular frequency of ω _C1 −ω _B1 (hereinafter referred to as a transmission wave L1A). The control unit 21 of the device 2 transmits a transmission wave having an angular frequency of ω _C2 −ω _B2 (hereinafter referred to as a transmission wave L2A) immediately after receiving the transmission wave L1A. Further, the control unit 21 of the apparatus 2 transmits again the transmission wave having the angular frequency ω _C2 −ω _B2 (hereinafter referred to as the transmission wave L2B) after the transmission wave L2A is transmitted. After receiving the second transmission wave L2B, the control unit 11 of the apparatus 1 again transmits a transmission wave having an angular frequency ω _C1 −ω _B1 (hereinafter referred to as a transmission wave L1B).

In this way, as shown in FIGS. 14 and 15, the control unit 21 of the device 2 acquires the phase θ _H1 (t) based on the transmission wave H1A from the predetermined reference time 0 to the predetermined time, and the predetermined time from the time t ₀ + D. The phase θ _H1 (t + t ₀ + D) based on the transmission wave H1B is acquired in time, the phase θ _L1 (t + T) based on the transmission wave L1A is acquired from the time T at a predetermined time, and the transmission wave is transmitted from the time t ₀ + D + T at the predetermined time. The phase θ _L1 (t + t ₀ + D + T) based on L1B is acquired.

Further, the control unit 11 of the apparatus 1 acquires the phase θ _H2 (t + t ₀ ) based on the transmission wave H2A from the time t _{0 at a} predetermined time, and the phase θ _H2 (t + D) based on the transmission wave H2B from the time D to the predetermined time. And a phase θ _L2 (t + t ₀ + T) based on the transmission wave L2A at a predetermined time from time t ₀ + T, and a phase θ _L2 (t + D + T) based on the transmission wave L2B at a predetermined time from time D + T.

  At least one of the devices 1 and 2 transmits phase information, that is, the calculated four phases or two phase differences or the calculation result of the above equation (139) to the phase difference to the other. The control unit of the device 1 or 2 that has received the phase information calculates the distance by the calculation of the above equation (139). Note that although steps S7 and S17 in FIG. 6 are described as phase difference calculation, in this case, it is not always necessary to calculate the phase difference in steps S7 and S17, and the phase difference may be calculated during the distance calculation in S19. .

As described above, in the present embodiment, by repeatedly alternating the carrier signals from the first device and the second device, accurate ranging is possible even when the carrier signals cannot be transmitted and received simultaneously. For example, the first device and the second device each transmit two angular frequency signals twice to the second device and the first device, respectively, in a predetermined sequence. Ask. Then, the device that transmits the obtained phase information from one of the first device and the second device to the other and receives the phase information is based on the eight phases obtained by the first device and the second device, A distance between the first device and the first device is calculated. Thereby, the distance between the first device and the second device is accurately calculated regardless of the initial phase of the oscillators of the first device and the second device. Thus, even when signals having angular frequencies are transmitted at the same time without being transmitted at the same time, accurate distance measurement is possible by removing errors in distance estimation.
(Multipath issues)
In the above description, the device 2 receives the two transmission signals of the angular frequencies ω _C1 + ω _B1 and ω _C1 −ω _B1 from the device 1 to detect the phases θ _H1 (t) and θ _L1 (t), and the device 2 By receiving two transmission signals of angular frequencies ω _C2 + ω _B2 and ω _C2 −ω _B2 from the apparatus 1 to detect the phases θ _H2 (t) and θ _L2 (t), and using these four phases It was shown that distance measurement is possible.

  However, there is a problem that the phase of the received wave changes due to the influence of multipath, and the phase corresponding to the propagation delay cannot be extracted accurately. Hereinafter, this problem will be described using a two-wave model that is considered to be a severe condition due to the influence of multipath.

  FIG. 16 is an explanatory diagram for explaining a problem due to such a multipath environment in distance measurement.

As shown in FIG. 16, the sine wave y (t ′) = sinωt ′ transmitted from the automobile C has two paths that propagate directly to the key K by reflecting the path (distance R) that directly propagates to the key K and the wall W. The key K is reached via the route (distance R + ΔR). The propagation delay of the direct wave passing through the path propagating directly from the car C to the key K is τ, and the propagation delay of the delayed wave passing through the path propagating from the car C to the wall W and propagating to the key K is τ + τ ₁ And

It is assumed that the key K receives two waves, a wave propagating on the path propagating to the key K with the propagation delay τ and a wave propagating on the path reflected on the wall and propagating to the key with the propagation delay τ + τ ₁ . In this case, the signal y (t ′) received by the key K is a signal obtained by adding these two waves, and is expressed by the following equation (69).
y (t ′) = sin {ω (t′−τ)} + Asin {ω (t′−τ−τ ₁ ) + θ ₁ } (69)
Here, θ ₁ indicates a phase shift that occurs when reflected by a wall, and A indicates an amplitude that takes into account a loss due to reflection and a propagation loss corresponding to a distance error ΔR. Here, in order to simplify the calculation, a signal at time t at the key K is represented by the following equation (70) where t = t′−τ.
y (t) = sinωt + Asin {ω (t−τ ₁ ) + θ ₁ }
= {1 + Acos (ωτ ₁ −θ ₁ )} sinωt−Asin (ωτ ₁ −θ ₁ ) cosωt (70)
When the equation (70) is transformed using a trigonometric function synthesis formula, the following equations (71) and (72) are obtained.
y (t) = {1 + A ² + 2A cos (ωτ ₁ −θ ₁ )} ^1/2 sin (ωt + φ) (71)
φ = −tan ⁻¹ (Asin (ωτ ₁ −θ ₁ ) / {1 + Acos (ωτ ₁ −θ ₁ )} (72)
Due to the influence of the delayed wave Asin {ω (t−τ ₁ ) + θ ₁ } reflected from the wall W from the equations (71) and (72), the received signal of the key K is obtained when the amplitude and phase are only direct waves. It turns out that it changes compared. A phase change amount corresponding to the phase variation of the angular frequency ω = ω _C1 + ω _B1 and phi _H, the phase variation with respect to the angular frequency ω = ω _C1 -ω _B1 and phi _L. When the difference φ _L −φ _H for this phase change is calculated, the following equation (73) is obtained.
φ _L −φ _H = −tan ⁻¹ [Asin {(ω _C1 −ω _B1 ) τ ₁ −θ ₁ }] / [1 + A cos {(ω _C1 −ω _B1 ) τ ₁ −θ ₁ }] + tan ⁻¹ [Asin {(Ω _C1 + ω _B1 ) τ ₁ −θ ₁ }] / [1 + A cos {(ω _C1 + ω _B1 ) τ ₁ −θ ₁ }] (73)
The above equation (73) indicates a phase detection error caused by the presence of a delayed wave. τ ₁ represents the delay time of the delayed wave with respect to the direct wave, and is a value proportional to the difference in propagation distance. As can be seen from the equation (73), φ _L −φ _H depends on θ ₁ but depends on the reflector and the incident angle, which is not related to the propagation distance.

FIG. 17 is a graph showing the relationship between the delay time τ ₁ and the phase change difference φ _L −φ _H with time on the horizontal axis and amplitude on the vertical axis. In FIG. 17, A = 0.5, θ ₁ = 0 (rad), τ ₁ = 16.8 (ns), ω _C1 = 2π × 900 M (Hz), and ω _B1 = 2π × 5 M (Hz). Shows the relationship.

The phase changes φ _H and φ _L corresponding to the angular frequencies ω _C1 + ω _B1 and ω _C1 −ω _B1 respectively are τ ₁ because the difference in delay time between the direct wave and the delayed wave is τ _1. 75).
φ _H = (ω _C1 + ω _B1 ) τ ₁ (74)
φ _L = (ω _C1 −ω _B1 ) τ ₁ (75)
Since τ ₁ = (φ _H −φ _L ) / 2ωB ₁ from the equations (74) and (75), the distance error ΔR due to the path difference is expressed by the following equation (76).
ΔR = cτ ₁ = c × (φ _H −φ _L ) / (2ω _B1 ) (76)
Here, assuming that ω _B1 = 2π × 5 M (Hz), when τ ₁ is in the vicinity of 16 (ns), −0.8 ≦ φ _H −φ _L ≦ 0.4, so the distance error ΔR is from 1.9 m to 3 It will be about 8m. In other words, when 2 m is required as the distance accuracy in the distance measuring system under such conditions, distance measurement is performed with an unacceptable distance error. Therefore, in this case, it is necessary to compensate for the influence of multipath.
(Specific examples for solving problems)
Therefore, in the present embodiment, the transmission units 14 and 24 transmit a signal having an angular frequency ω = ω _C1 separately from a transmission wave having an angular frequency ω = ω _C1 + ω _B1 and ω = ω _C1 −ω _B1. It is like that.

Amplitude ratio of these three waves, result in particular amplitude ratio .DELTA.A _H0 and the angular frequency omega _C1 + omega _B1 for the angular frequency omega _C1, was determined amplitude ratio .DELTA.A _L0 angular frequency omega _C1 - [omega] _B1 for the angular frequency omega _C1 Is used. Here, the added signal of the angular frequency ω _C1 is an average angular frequency of ω _C1 + ω _B1 and ω _C1 −ω _B1 , but the effect is lost even if the angular frequency of the additional signal slightly deviates from the average value. is not.

In the key K, the signal received at time t, respectively the amplitude _{A H} of the angular frequency ω _C1 + ω _B1, the amplitude _{A 0} of omega _C1, the amplitude _{A L} of omega _C1 - [omega] _B1 from the (71) equation If it calculates | requires, it will become the following (77) Formula-(79) Formula.
A _H = [1 + A ² + 2A cos {(ω _C1 + ω _B1 ) τ ₁ −θ ₁ }] ^1/2 (77)
A ₀ = {1 + A ² + 2A cos (ω _C1 τ ₁ −θ ₁ )} ^1/2 (78)
A _L = [1 + A ² + 2A cos {(ω _C1 −ω _B1 ) τ ₁ −θ ₁ }] ^1/2 (79)
However, the phase shift θ ₁ caused by the wall W during reflection is assumed to be the same value in the frequency range to be applied. From the above equations (77) to (79), the following equations (80) and (81) in which the amplitude ratios ΔA _H0 and ΔA _L0 are displayed in decibels are obtained.
ΔA _H0 = 10 log {1 + A ² + 2A cos {(ω _C1 + ω _B1 ) τ ₁ −θ ₁ )}
−10 log {1 + A ² + 2A cos (ω _C1 τ ₁ −θ ₁ )} (80)
ΔA _L0 = 10 log {1 + A ² + 2A cos {(ω _C1 + ω _B1 ) τ ₁ −θ ₁ )}
−10 log {1 + A ² + 2A cos (ω _C1 τ ₁ −θ ₁ )} (81)
FIG. 18 is a graph showing the relationship between the above equations (80), (81), and Δsum = ΔA _H0 + ΔA _L0 and τ ₁ by the same display as in FIG. FIG. 18 shows the case as θ ₁ = 0 (rad). Note that a change in θ ₁ is equivalent to a shift of the horizontal axis τ ₁ and the shape of each characteristic curve in the graph does not change.

As can be seen from the comparison between FIG. 17 and FIG. 18, the delay time τ ₁ that takes the maximum value of φ _H −φ _L and Δsum = ΔA _H0 + ΔA _L0 is equal. Therefore, in the present embodiment, paying attention to this point, the phase error φ _H −φ _L is corrected using Δsum = ΔA _H0 + ΔA _L0 .

FIG. 19 is a graph for explaining the τ ₁ dependence of φ _L −φ _{H and} the τ ₁ dependence of Δsum / 4 = (ΔA _H0 + ΔA _L0 ) / 4 by the same display as FIG. 17 and FIG. .

As shown in FIG. 19, the characteristic curve of φ _H −φ _{L and} the characteristic curve of Δsum / 4 = (ΔA _H0 + ΔA _L0 ) / 4 are not the same, but show similar changes. If this relationship is used to subtract (ΔA _H0 + ΔA _L0 ) / 4 from the phase detected using two waves, the phase error due to multipath can be greatly reduced. Here, the addition of the amplitude ratio is multiplied by (1/4) times, but (1/4) is not necessarily an optimal value if the target τ ₁ is changed. This multiplication value is a design parameter and may be changed according to circumstances.

When the distance error ΔR is obtained with respect to a value obtained by subtracting (ΔA _H0 + ΔA _L0 ) / 4 from the multipath phase error, the following (82) is obtained.
ΔR = {φ _L −φ _H | in rad− (ΔA _H0 + ΔA _L0 | in dB) / 4} × c / (2ω _B1 ) (82)
FIG. 20 is a graph showing the distance error ΔR without correction and the distance error ΔR with correction by the same display as in FIGS. In addition, the vertical axis | shaft of FIG. 20 is distance error (DELTA) R (m). From the above equation (82), in the range of τ ₁ from 0 (ns) to 20 (ns), the distance error ΔR is set to 1.8 m or less by subtracting (ΔA _H0 + ΔA _L0 ) / 4 from the detected phase. I can see that Further, in the range of τ ₁ from 0 (ns) to 10 (ns), the distance error ΔR can be suppressed to 1.2 m. Thus, in the present embodiment, the distance accuracy can be improved by using the information of the amplitude ratio using the third wave.
(Ranging operation using three waves corresponding to multipath)
Next, the operation of such a distance measuring system will be described with reference to the flowchart of FIG. In FIG. 21, the same steps as those in FIG. FIG. 21 shows the operation of the device 1 on the left side and the operation of the device 2 on the right side. In FIG. 21, an arrow connecting the steps of the devices 1 and 2 indicates that communication is performed between the devices 1 and 2.

The example of FIG. 21 is different from the flow of FIG. 6 in that steps S21 and S22 are added on the device 1 side and steps S31 to S34 are added on the device 2 side. Step S21 is a procedure for generating a single transmission signal (additional signal) having an angular frequency of ω _C1 as an additional signal of the third wave from the device 1, and step S22 is for one wave based on the generated additional signal. This is a procedure for transmitting an additional transmission wave.

  Upon receiving this additional transmission wave in step S31, the device 2 acquires I and Q signals in step S32, and calculates a distance error in step S33. In step S34, the device 2 subtracts the distance error from the distance obtained in step S19 to obtain a corrected distance.

  In the flow of FIG. 21, as in the flow of FIG. 6, it is not always necessary to calculate the phase difference in steps S7 and S17, and the phase difference may be calculated when calculating the distance in S19.

  Other operations are the same as those in FIG.

Incidentally, the calculation of the distance error at the step S33, is based on the above-described (82) equation, the amplitude ratio .DELTA.A _H0 and amplitude ratio .DELTA.A _L0, as shown in the above (80) and (81) below, the time Not affected. Therefore, the additional signal may be transmitted at any time timing. For example, the example of FIG. 21 shows an example in which the additional signal is transmitted after the phase difference is calculated. For example, the additional signal may be transmitted immediately after the transmission of the two transmission waves. Alternatively, an additional signal may be transmitted before.

In the example of FIG. 21, the example in which the device 2 receives the additional signal transmitted by the device 1 and obtains the distance error has been described. However, the device 2 transmits the additional signal having the angular frequency ω _C2 and The distance error may be calculated using the received additional signal and the received two transmission waves, and information on the calculated distance error may be transmitted to the apparatus 2 so that the distance is corrected in the apparatus 2.

  Other operations are the same as when two waves are used.

  As described above, in the present embodiment, the carrier signal from the first device and the second device is transmitted by two waves to each other, and the additional signal is transmitted by one wave, thereby calculating a distance error in multipath, Ranging with reduced multipath effects is possible.

It should be noted that the above multipath processing, 2π residue calculation processing, selection processing from a plurality of distance candidates, time series transmission / reception processing, and the like can be combined as appropriate.
(Second Embodiment)
22 and 23 are explanatory views showing a second embodiment of the present invention. This embodiment shows an example in which each distance measuring system is applied to a smart entry system.

  In FIG. 22, the key 31 can wirelessly transmit a signal that enables unlocking and locking of the door of the automobile 32 and starting of the engine of the automobile 32. That is, the key 31 has a data transmission / reception unit (not shown), and the data transmission / reception unit can transmit encrypted unique data for authentication. Radio waves from the data transmission / reception unit of the key 31 are received by a vehicle control device 35 (not shown) mounted on the automobile 32.

  As shown in FIG. 23, the vehicle control device 35 is provided with a control unit 36. The control unit 36 controls each unit of the vehicle control device 35. The control unit 36 may be configured by a processor using a CPU or the like, and may operate according to a program stored in the memory 38 to control each unit.

  The vehicle control device 35 is provided with a data transmission / reception unit 37. The data transmission / reception unit 37 can perform wireless communication with the data transmission / reception unit of the key 31 via the antenna 35a. The data transmitter / receiver 37 receives the unique data transmitted from the key 31 and transmits predetermined response data to the key 31 to authenticate the key 31 and the automobile 32.

  The data transmission / reception unit 37 can finely set the electric field strength. If the key 31 is not located at a relatively close position where the transmission data of the data transmission / reception unit 37 can be received, that is, in the vicinity of the car 32, authentication is performed. Is not done.

  For example, it is assumed that the key 31 is located sufficiently close to the automobile 32 as indicated by a broken line in FIG. In this case, the data transmission / reception unit 37 can communicate with the key 31. The data transmission / reception unit 37 authenticates the key 31 by collation with the unique data recorded in the memory 37a. The data transmission / reception unit 37 outputs a signal indicating that the key 31 has been authenticated to the control unit 36. Accordingly, the control unit 36 controls the unlocking / locking device 39 to give permission for unlocking and locking.

  In FIG. 22, the relay devices 33 and 34 are possessed by a relay attack attacker. The relay device 33 can communicate with the key 31, the relay device 34 can communicate with the data transmitting / receiving unit 37 in the automobile 32, and the relay devices 33, 34 can transmit / receive data to / from the key 31. The communication with the unit 37 is relayed. Thus, even when the key 31 is sufficiently separated from the car 32 as shown in FIG. 22 and direct communication between the key 31 and the data transmission / reception unit 37 is not possible, data transmission / reception is performed via the relay devices 33 and 34. The unit 37 can authenticate the key 31.

  Therefore, in the present embodiment, the control unit 36 determines whether to permit unlocking and locking, engine starting, and the like based on the authentication result of the data transmitting / receiving unit 37 and the distance measurement result from the second device 2. Is to decide.

  The key 31 incorporates the second device 2 in the first embodiment. On the other hand, the device 1 in the first embodiment is mounted on the vehicle control device 35. A transmission wave from the device 1 is received by the device 2 via the antenna 27a, and a transmission wave from the device 2 is received by the device 1 via the antenna 27a. The transmission wave from the device 1 may be received directly by the antenna 27a, or may be received by the antenna 27a via the relay devices 33 and 34. Similarly, the transmission wave from the second device may be directly received by the device 1 from the antenna 27a, or may be directly received by the device 1 via the relay devices 33 and 34 from the antenna 27a.

  Assuming that the phase of the transmission wave from the devices 1 and 2 does not change in the relay devices 33 and 34, the device 2 calculates the distance to the key 31 based on the phase obtained in the devices 1 and 2. Can do. The device 2 outputs the calculated distance to the control unit 36. The memory 38 stores a distance threshold value that permits authentication of the key 31, and the control unit 36 authenticates the key 31 when the distance calculated by the device 2 is within the distance threshold value read from the memory 38. As a result, unlocking and locking, engine starting, etc. are permitted. Further, when the distance calculated by the device 2 is larger than the distance threshold value read from the memory 38, the control unit 36 does not permit the key 31 to be authenticated. Therefore, in this case, unlocking and locking, engine starting, and the like are not permitted.

  In the relay apparatuses 33 and 34, the phase of the transmission wave from the apparatuses 1 and 2 can be changed. Even in this case, since the initial phases of the devices 1 and 2 are unknown, the amount of phase shift required for the distance calculated by the device 2 to be a value within the distance threshold value read from the memory 38 is determined as a relay device. 33 and 34 cannot be obtained. For this reason, even if the relay devices 33 and 34 are used, the possibility that the authentication of the key 31 is permitted is sufficiently small.

As described above, in the present embodiment, by using the distance measuring system in the first embodiment, it is possible to prevent the vehicle from being unlocked or the like by the relay attack on the smart entry system. .
(Transmission sequence)
24 to 35 are explanatory diagrams showing various sequences that can be adopted in each of the above embodiments.

  FIG. 24 shows a sequence in which carrier sense is performed and there is no response and no repeated alternation. In this sequence example, the presence or absence of a ranging frequency is determined by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 25 shows a sequence in which carrier sense is performed, no response is given, and there are repeated alternations. This sequence example also determines the presence or absence of a ranging frequency by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 26 shows a sequence in which carrier sense is performed, there is a response, and there are repeated alternations. This sequence example also determines the presence or absence of a ranging frequency by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 27 shows a sequence without carrier sense, no response, and no repeated alternation. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 28 shows a sequence with no carrier sense, no response, and repeated alternation. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 29 shows a sequence with no carrier sense, with a response and with repeated alternation.

  FIG. 30 shows a sequence with and without carrier sense, no response, and no repeated alternation. This sequence example also determines the presence or absence of a ranging frequency by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 31 shows a sequence with or without carrier sense, no response, and no repeated alternation. This sequence example also determines the presence or absence of a ranging frequency by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 32 shows a sequence with or without carrier sense, no response, and repeated alternation. This sequence example also determines the presence or absence of a ranging frequency by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 33 shows a sequence with and without a carrier sense, with a response and with a repeated alternation. This sequence example also determines the presence or absence of a ranging frequency by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

  FIG. 34 shows a sequence in which carrier sense is performed, there is a response, and there are repeated alternations. This sequence example also determines the presence or absence of a ranging frequency by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.

FIG. 35 shows a sequence with and without a carrier sense, with a response and with repeated alternation. This sequence example also determines the presence or absence of a ranging frequency by carrier sense. When sensing by carrier sense, (a) a predetermined time (for example, several ms) may be started again from the beginning, or (b) a carrier sense exclusion prescribed sequence may be started. The transmission wave of the center frequency is for obtaining only the amplitude ratio with other transmission waves, and may be measured at any timing after receiving each transmission wave.
(Modifications related to multipath)
FIG. 36 is a flowchart showing the operation in the modified example considering multipath, and corresponds to FIG. In FIG. 36, the same steps as those in FIG.

As shown in FIG. 17, the phase detection error (φ _L −φ _H ) due to the presence of the delayed wave has a maximum value at a predetermined interval on the delay time difference axis. In other words, the value of the phase detection error φ _L −φ _H due to the presence of the delayed wave is small on the delay time difference axis where the maximum value does not occur. As shown in the equation (73) for obtaining the graph of FIG. 17, the value of φ _L −φ _H can be reduced by changing the angular frequencies ω _C1 and ω _B1 . Note that if the frequency difference is enlarged or the frequency is reset so as to shift the center frequency, the waveform of FIG. 18 shifts from the equation (80) and the equation (81) to the horizontal axis. It can be seen that it is possible to avoid the condition of a serious phase deterioration.

  Therefore, in this modification, it is determined whether or not the phase variation due to the delayed wave is large, and when it is determined that the phase variation is large, control is performed to change the carrier frequency, and when it is determined that the phase variation is small, The distance error is calculated to correct the distance.

For example, in this modification, whether the phase fluctuation is large may be obtained from ΔA _H0 and ΔA _L0 according to the above equations (80) and (81). As is apparent from FIG. 18, when the phase fluctuation due to the path of the delay difference τ1 becomes large, both ΔA _H0 and ΔA _L0 become positive. On the other hand, even when ΔA _H0 and ΔA _L0 are both negative, the phase variation becomes large as is apparent from the comparison of the equations (73) and (80).

Therefore, in this modification, when the amplitude ratios ΔA _H0 and ΔA _L0 are observed and both ΔA _H0 and ΔA _L0 are positive or negative, it is determined that the phase error due to multipath is relatively large, and the frequency Ranging is performed by enlarging the difference, shifting the center frequency, or setting the frequency again. Thereby, it is possible to reduce distance accuracy degradation.

When the addition result of ΔA _H0 + ΔA _L0 is smaller than the first predetermined threshold value (TH1) or larger than the second predetermined threshold value (TH2), it is determined that the phase error due to multipath is large and the same operation is performed. It is also effective to do.

FIG. 36 shows an example in which the distance is calculated in the second device. When the control unit 21 acquires the I and Q signals in step S32, the controller 21 determines the distance error in the next step S41. For example, the control unit 21 determines whether or not TH1 ≦ ΔA _H0 + ΔA _L0 ≦ TH2 is established. If it is established, the control unit 21 determines that the distance error is relatively small, shifts the processing to step S33, and calculates the distance error.

On the other hand, when ΔA _H0 + ΔA _L0 is smaller than the threshold value TH1 or larger than the threshold value TH2 in step S41, the control unit 21 determines that the phase error due to multipath is large, and the process proceeds to step S42. To do. In step S42, the controller 21 resets the carrier frequency and returns the process to steps S3 and S13. Thereafter, the same operation is repeated, and the distance is corrected when it is determined that the distance error is relatively small.

  36, it is not always necessary to calculate the phase difference in steps S7 and S17, and the phase difference may be calculated when calculating the distance in S19.

The correction in step S34 in FIGS. 21 and 36 is obtained by subtracting (ΔA _H0 + ΔA _L0 | in dB) / 4 from the detected phase difference as shown in the above equation (82). For example, (ΔA _H0 + ΔA _L0 | in dB) can be subtracted after intentionally distorting. One example is sin {(ΔA _H0 + ΔA _L0 | in dB) / 4}. Although not shown, in this case, when the delay τ1 is large due to the sine function, the amplitude is compressed and the phase accuracy is improved.
(Modification)
37 to 39 show modifications. This modification explains the period in which the initial phase should be fixed. FIG. 37 is an explanatory diagram showing the relationship between the transmission sequence and the period for maintaining the initial phase. FIG. 38 is an explanatory diagram showing a carrier frequency used for distance measurement, and FIG. 39 is a flowchart showing a modification.

  In the first embodiment, simultaneous transmission and reception of two frequencies from the devices 1 and 2 are assumed. In this transmission / reception period, the oscillators 13 and 23 continue to oscillate so that the initial phase does not change. On the other hand, in the second embodiment, it is defined that only one wave can be transmitted and received at the same time between the devices 1 and 2, and at least four waves necessary for ranging are transmitted and received in time series. At the same time, by repeatedly alternating the carrier signals from the devices 1 and 2, accurate distance measurement is possible even when time series transmission / reception is performed.

For example, as described above, in the example of FIG. 15, transmission / reception of the transmission wave of the angular frequency ω _C1 + ω _B1 from the apparatus 1, transmission / reception of the transmission wave of the angular frequency ω _C2 + ω _B2 from the apparatus 2, apparatus 1 The transmission wave of angular frequency ω _C1 + ω _B1 is transmitted and received from

Furthermore, transmission / reception of the transmission wave of the angular frequency ω _C1 −ω _B1 from the apparatus 1, transmission / reception of the transmission wave of the angular frequency ω _C2 −ω _B2 from the apparatus 2, angular frequency ω _C1 −ω _B1 from the apparatus 1. Transmit / receive the transmitted wave.

The addition result of the phases obtained by the devices 1 and 2 by the transmission and reception of the first four waves in FIG. The addition result of the first to fourth terms is 2 (θ _τH1 + θ _τH2 ) as shown in the above equation (132), and as shown in the above equations (20) and (30), Does not contain terms. That is, since the phase calculation result obtained by transmission / reception of the first four waves in FIG. 15 does not include information on the initial phase, the calculation of the first to fourth terms of the above equation (139) If the initial phase is not changed only during the transmission / reception period, a correct result is obtained.

Similarly, the addition result of the phases obtained by the devices 1 and 2 by the transmission and reception of the last four waves in FIG. The addition result of the fifth to eighth terms is 2 (θ _τL1 + θ _τL2 ) as shown in the above equation (138), and as shown in the above equations (40) and (50), Does not contain terms. That is, since the phase calculation result obtained by transmission / reception of the last four waves in FIG. 15 does not include information on the initial phase, the calculation of the fifth to eighth terms of the above equation (139) If the initial phase is not changed only during the transmission / reception period, a correct result is obtained.

FIG. 37 shows this state, in which the initial phase is kept constant during the distance measurement period using the angular frequencies ω _C1 + ω _B1 and ω _C2 + ω _B2 and the angular frequencies ω _C1 −ω _B1 and ω _C2 −ω _B2. It shows that the initial phase is kept constant during the distance measurement period using.

  That is, for example, when the sequence of FIG. 15 is adopted, the oscillations of the oscillators 13 and 23 are continued so that the initial phase does not change during the first four-wave transmission / reception period, and the last four-wave transmission / reception period. The oscillations of the oscillators 13 and 23 may be continued so that the initial phase does not change in the period of time, and the oscillations of the oscillators 13 and 23 are stopped after the transmission / reception of the fourth wave until the transmission / reception of the fifth wave. Even if changes, an accurate distance can be calculated based on the above equation (139).

In the above embodiments, the two carrier signals transmitted by the devices 1 and 2 are, for example, the sum of relatively high angular frequencies ω _C1 and ω _C2 and, for example, relatively low angular frequencies ω _B1 and ω _B2 , or An example of the difference frequency is shown. The angular frequencies ω _C1 and ω _C2 are set to substantially the same frequency, and the angular frequencies ω _B1 and ω _B2 are set to substantially the same frequency.
(About two carrier signals)
However, in the distance measurement in each of the above embodiments, as described below, the devices 1 and 2 only need to transmit two carrier signals each having a predetermined frequency difference.

The angular frequency ω _C + ω _B and the angular frequency ω _C −ω _B can be modified as follows.
ω _C + ω _B = (ω _C −Δω _C ) + (Δω _C + ω _B ) = ω ′ _C + ω _H (201)
ω _C −ω _B = (ω _C −Δω _C ) + (Δω _C −ω _B ) = ω ′ _C + ω _L (202)
Now, when a transmission wave having an angular frequency of ω _C and an angular frequency of ω _B is indicated as f _C and f _B on the frequency axis, the transmission wave having an angular frequency of ω _C + ω _B and an angular frequency of ω _C −ω _B is illustrated in FIG. 38 is shown on the left side.

The above expressions (201) and (202) are obtained by changing the expression method without changing the frequency. A transmission wave having an angular frequency of ω _C + ω _B has an angular frequency of ω ′ _C and an angular frequency of ω _C + ω _B. A transmission wave having an angular frequency of ω _C −ω _B obtained by the sum of ω _H and an angular frequency of ω ′ _C and an angular frequency of ω _L is obtained.

The center of FIG. 38 shows a transmission wave based on this expression, and transmission waves having angular frequencies ω ′ _C , ω _H, and ω _L are shown as f ′ _C , f _H , and f _L on the frequency axis, respectively. The transmission wave of the frequency f _C -f _{B and} the transmission wave of the frequency f _C + f _B on the left side of FIG. 38 are expressed as a transmission wave of f ′ _C + f _{L and} a transmission wave of f ′ _C + f _H of the same frequency, respectively. It shows what you can do.

  That is, in the above formulas (201) and (202), the two carriers transmitted by the devices 1 and 2 do not have to be obtained by the sum and difference of the two frequencies, and the devices 1 and 2 have a predetermined frequency difference. It shows that it is only necessary to generate and transmit two carriers.

As an example of obtaining a transmission wave having an angular frequency ω _C + ω _B and an angular frequency ω _C −ω _B shown on the left side of FIG. 38, for example, in the oscillators 13 and 23 of FIG. A local signal having an angular frequency ω _{C as} an LO frequency) and a local signal having an angular frequency ω _B as a relatively low local frequency (hereinafter referred to as IF-LO frequency). The sum and difference signals may be generated as transmission signals.

On the other hand, the transmission wave at the center of FIG. 38 generates a local signal having an angular frequency ω ′ _C as an RF-LO frequency and two local signals having angular frequencies ω _L and ω _H as IF-LO frequencies. Generated by the transmitters 14 and 24 to generate a sum signal of these local frequencies as a transmission signal. That is, the center transmission wave in FIG. 38 is obtained by fixing the RF-LO frequency and changing the IF-LO frequency.

Further, the angular frequency ω _C −ω _B can be modified as follows.
ω _C −ω _B = (ω _C −2ω _B ) + (2ω _B −ω _B ) = ω ″ _C + ω _B (203)
The right side of FIG. 38 shows the transmission wave based on the representation of the (203) type, indicating "transmission waves from the _C f on the frequency axis" is the angular frequency ω as _C, the left side of FIG. 38 the frequency f _C - transmission wave f _B indicate that that can be represented as a transmitted wave f "C ₊ f _B of the same frequency.

For example, the transmission wave on the right side of FIG. 38 generates a local signal having an angular frequency ω ′ _{C and} a local signal having an angular frequency ω ″ _C as an RF-LO frequency, and a local signal having an angular frequency ω _B as an IF-LO frequency. 38 is obtained by generating a signal of the sum of these local frequencies as a transmission signal in the transmitters 14 and 24. That is, the transmission wave on the right side of FIG. Obtained by changing the RF-LO frequency.
(Change carrier frequency)
As described above, the devices 1 and 2 only need to transmit two carrier signals each having a predetermined frequency difference in ranging. In addition, when the transmission / reception of the high frequency carrier out of the two carriers is performed alternately as shown in the sequence of FIG. 15, and then the transmission / reception of the low frequency carrier is performed alternately, the high frequency carrier is transmitted. The initial phase may be different between transmission / reception and transmission / reception of a low-frequency carrier.

  Further, only the high frequency carrier is used for the calculation of the above expression (132) obtained by decomposing the above expression (139), and only the low frequency carrier is used for the calculation of the above expression (138). That is, the calculation of the above equation (132) and the calculation of the above equation (138) may be performed independently, and the carrier frequency is changed between the transmission / reception period of the high frequency carrier and the transmission / reception period of the low frequency carrier. Also good.

  If the change of the initial phase and the change of the carrier angular frequency are allowed, the flow of FIG. 39 can be adopted instead of the flow of FIG. 11A.

  In the flow of FIG. 39, the first local (LO) frequency is set before the one-wave transmission signal is generated in the device 1, and the first local is received in the device 2 before the one-wave transmission wave is received from the device 1. (LO) Set the frequency. The device 1 generates a high-frequency carrier using, for example, a single-wave transmission signal using the local signal of the first LO frequency, and the device 2 receives a single-wave transmission wave using this high-frequency carrier to receive I, Get the Q signal.

Further, the device 1 sets the second local (LO) frequency after acquiring the I and Q signals based on the transmission wave from the device 2 and before generating the next one-wave transmission signal. Similarly, the device 2 sets the second local (LO) frequency after transmission of one wave transmission wave to the device 1 and before reception of the next one wave transmission wave. In the apparatus 1, a low frequency carrier is generated as a one-wave transmission signal, for example, using the local signal of the second LO frequency. Further, the device 2 receives the transmission wave of the device 1 using this low frequency carrier and acquires I and Q signals.
(Configuration example of oscillator and transceiver)
In this way, the devices 1 and 2 only need to be able to generate and transmit two carrier signals having a predetermined frequency difference, and the oscillators 13 and 23, transmitters 14 and 24, and receivers 15 and 25 in FIG. A circuit having the following configuration can be employed.

  FIG. 40A is an explanatory diagram showing a simplified example of the configuration of the oscillator 13, the transmission unit 14, and the reception unit 15 of the device 1. 40B is an explanatory diagram showing a simplified example of the configuration of the oscillator 23, the transmission unit 24, and the reception unit 25 of the device 2.

  As shown in FIGS. 40A and 40B, the device 1 and the device 2 include an oscillator that generates an IF-LO frequency and an oscillator that generates an RF-LO frequency. The oscillation frequency of these oscillators is fixed, for example, and two carrier signals having a frequency difference can be generated by adding or subtracting the IF-LO frequency to the RF-LO frequency.

  FIG. 41A is an explanatory diagram illustrating a simplified example of the configuration of the oscillator 13, the transmission unit 14, and the reception unit 15 of the device 1. 41B is an explanatory diagram showing a simplified example of the configuration of the oscillator 23, the transmission unit 24, and the reception unit 25 of the device 2.

  The example of FIGS. 41A and 41B is an example in which two carrier signals having a frequency difference are generated by a frequency variable oscillator and a frequency divider (N-div).

  42 is a circuit diagram specifically showing an example of a circuit for generating signals to be supplied to the multipliers TM11 and TM12 in FIG. 4, and FIG. 43 is a signal to be supplied to the multipliers TM21 and TM22 in FIG. FIG.

In Figure 42, the multiplier TM15 gives the result of multiplying the local signal _{cos (ω B1 t + θ B1} ) from _{I T} signal and the oscillator 13 to the adder TS15, multiplier TM16 is from _{Q T} signal and the oscillator 13 The multiplication result with the local signal ± sin (ω _B1 t + θ _B1 ) is given to the adder TS15. The adder TS15 adds the two inputs and gives the addition result to the multiplier TM11.

Also, the multiplier TM17 gives the result of multiplying the local signal ± sin from _{I T} signal and the oscillator _{13 (ω B1 t + θ B1} ) to the adder TS16, multiplier TM18 is local from _{Q T} signal and the oscillator 13 A multiplication result with the signal cos (ω _B1 t + θ _B1 ) is given to the adder TS16. The adder TS16 subtracts the output of the multiplier TM18 from the output of the multiplier TM17 and gives the subtraction result to the multiplier TM12. Other configurations are the same as those in FIG.

In Figure 43, the multiplier TM25 gives the result of multiplying the local signal _{cos (ω B2 t + θ B2} ) from _{I T} signal and the oscillator 23 to the adder TS25, multiplier TM26 is from _{Q T} signal and the oscillator 23 A multiplication result with the local signal ± sin (ω _B2 t + θ _B2 ) is given to the adder TS25. The adder TS25 adds the two inputs and gives the addition result to the multiplier TM21.

Also, the multiplier TM27 gives the result of multiplying the local signal ± sin from _{I T} signal and the oscillator _{23 (ω B2 t + θ B2} ) to the adder TS26, multiplier TM28 is local from _{Q T} signal and the oscillator 23 A multiplication result with the signal cos (ω _B2 t + θ _B2 ) is given to the adder TS26. The adder TS26 subtracts the output of the multiplier TM28 from the output of the multiplier TM27 and gives the subtraction result to the multiplier TM22. Other configurations are the same as those in FIG.

  FIG. 44 is a circuit diagram showing an example of a specific configuration of the transmission unit 14 and the reception unit 15 in FIG. FIG. 45 is a circuit diagram showing an example of a specific configuration of the transmission unit 24 and the reception unit 25 in FIG. 44 and 45 show a transceiver with a heterodyne configuration.

In Figure 44, the multiplier TM1A gives the result of multiplying the local signal _{cos (ω B1 t + θ B1} ) from _{I T} signal and the oscillator 13 to the adder TS1a, multiplier TM1B is from _{Q T} signal and the oscillator 13 The multiplication result with the local signal sin (ω _B1 t + θ _B1 ) is given to the adder TS1A. The adder TS1A subtracts the output of the multiplier TM1B from the output of the multiplier TM1A and gives the subtraction result to the multiplier TM1C. The multiplier TM1C multiplies the output of the adder TS1A and the local signal cos (ω _C1 t + θ _C1 ), and outputs the multiplication result as a transmission signal tx1.

The multiplier RM1A multiplies the received signal rx1 and the local signal cos (ω _C1 t + θ _C1 ) to obtain the I ₁ signal, and outputs it to the multipliers RM1B and RM1C. The multiplier RM1B outputs a multiplication result of the I ₁ signal and the local signal cos (ω _B1 t + θ _B1 ) as an I signal. Further, the multiplier RM1C outputs a multiplication result of the I ₁ signal and the local signal sin (ω _B1 t + θ _B1 ) as a Q signal.

In Figure 45, the multiplier TM2A gives the result of multiplying the local signal _{cos (ω B2 t + θ B2} ) from _{I T} signal and the oscillator 23 to the adder TS2A, multiplier TM2B is from _{Q T} signal and the oscillator 23 The multiplication result with the local signal sin (ω _B2 t + θ _B2 ) is given to the adder TS2A. The adder TS2A subtracts the output of the multiplier TM2B from the output of the multiplier TM2A and gives the subtraction result to the multiplier TM2C. The multiplier TM2C multiplies the output of the adder TS2A and the local signal cos (ω _C2 t + θ _C2 ), and outputs the multiplication result as a transmission signal tx2.

The multiplier RM2A multiplies the received signal rx2 and the local signal cos (ω _C2 t + θ _C2 ) to obtain the I ₁ signal, and outputs it to the multipliers RM2B and RM2C. The multiplier RM2B outputs the multiplication result of the I ₁ signal and the local signal cos (ω _B2 t + θ _B2 ) as an I signal. The multiplier RM2C outputs the multiplication result of the I ₁ signal and the local signal sin (ω _B2 t + θ _B2 ) as a Q signal.

  46 is a circuit diagram showing an example of a specific configuration of the transmission unit 14 and the reception unit 15 in FIG. 47 is a circuit diagram showing an example of a specific configuration of the transmission unit 24 and the reception unit 25 in FIG. 46 and 47 show a transmitter / receiver adopting the direct conversion method.

In Figure 46, the multiplier TM1D gives the result of multiplying the local signal _{cos (ω C1 t + θ C1} ) from _{I T} signal and the oscillator 13 to the adder TS1C, multiplier TM1E is from _{Q T} signal and the oscillator 13 A multiplication result with the local signal sin (ω _C1 t + θ _C1 ) is given to the adder TS1C. The adder TS1C subtracts the output of the multiplier TM1E from the output of the multiplier TM1D and outputs the subtraction result as the transmission signal tx1.

The multiplier RM1D multiplies the received signal rx1 and the local signal cos (ω _C1 t + θ _C1 ) and outputs the multiplication result as an I signal. The multiplier RM1E multiplies the received signal rx1 and the local signal sin (ω _C1 t + θ _C1 ) and outputs the multiplication result as a Q signal.

In Figure 47, the multiplier TM2D gives the result of multiplying the local signal _{cos (ω C2 t + θ C2} ) from _{I T} signal and the oscillator 23 to the adder TS2C, multiplier TM2E is from _{Q T} signal and the oscillator 23 A multiplication result with the local signal sin (ω _C2 t + θ _C2 ) is given to the adder TS2C. The adder TS2C subtracts the output of the multiplier TM2E from the output of the multiplier TM2D and outputs the subtraction result as a transmission signal tx2.

The multiplier RM2D multiplies the received signal rx2 and the local signal cos (ω _C2 t + θ _C2 ) and outputs the multiplication result as an I signal. The multiplier RM2E multiplies the received signal rx2 and the local signal sin (ω _C2 t + θ _C2 ) and outputs the multiplication result as a Q signal.
(Example of phase information transmission)
In each of the above embodiments, phase information is transmitted from one of the first device and the second device to the other. However, as described above, the phase information transmission method is not particularly limited. . For example, the phase information may be transmitted by shifting the phase of the carrier signal to be transmitted by the phase obtained from the received signal.

  For example, in this case, the broken line portion in FIG. 6 can be replaced with the flow in FIG. 48, and a flow in which steps S7, S8, and S18 in FIG. 6 are omitted can be employed.

  FIG. 48 is a flowchart illustrating an example in which the second device transmits phase information to the first device, corresponding to FIG. 11A. FIG. 48 includes a step of adding the reception phase and the initial phase between the acquisition step of the I and Q signals and the one-wave transmission signal generation step in the second apparatus of FIG. 11A. Thereby, a carrier signal in which the phase detected from the received signal is added to the initial phase of the device 2 is generated. The device 1 can obtain the phase information obtained by the device 2 by receiving the carrier signal from the device 2 and obtaining the phase.

  FIG. 49 is a flowchart showing an example corresponding to FIG. 49 includes a step of adding the reception phase and the initial phase between the acquisition step of the I and Q signals and the one-wave transmission signal generation step in the second device of FIG. Thus, even when the carrier frequency is changed during distance measurement, the phase information may be included in the phase information of the carrier signal transmitted for distance measurement.

  In addition, this invention is not limited to the said embodiment, In the implementation stage, it can change variously in the range which does not deviate from the summary. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the column of the effect of the invention Can be obtained as an invention.

    DESCRIPTION OF SYMBOLS 1,2 ... Apparatus, 11,21 ... Control part, 12, 22 ... Memory, 13, 23 ... Oscillator, 14, 24 ... Transmitter, 15, 25 ... Receiver, 17, 27 ... Antenna circuit.

Claims (18)

In a distance measuring device that calculates a distance based on carrier phase detection,
A calculating unit that calculates a distance between the first device and the second device based on phase information acquired by the first device and the second device at least one of which is movable;
The first device includes:
A first reference signal source;
A first transceiver for transmitting three or more first carrier signals using the output of the first reference signal source and receiving three or more second carrier signals;
The second device includes:
A second reference signal source that operates independently of the first reference signal source;
A second transceiver for transmitting the three or more second carrier signals using the output of the second reference signal source and receiving the three or more first carrier signals;
The calculation unit calculates the distance based on a phase detection result obtained by receiving the first and second carrier signals, and calculates the calculated distance from the first carrier received by the second transceiver. A distance measuring device that performs correction based on information on the amplitude ratio between signals. 2. The distance measuring apparatus according to claim 1, wherein the first and second reference signal sources continuously operate during a period in which the first and second carrier signals are transmitted and received by the first and second transceivers. The receiver of the first transceiver comprises a first phase detector for detecting the phase of the two or more second carrier signals;
2. The distance measuring apparatus according to claim 1, wherein a receiver of the second transceiver includes a second phase detector that detects phases of the two or more first carrier signals. The distance measuring device according to claim 3, wherein the first and second phase detectors are configured by quadrature demodulators. The first transceiver transmits three first carrier signals using the output of the first reference signal source and receives two or more second carrier signals;
The second transceiver transmits the two or more second carrier signals using the output of the second reference signal source and receives the three first carrier signals;
The calculation unit calculates the distance based on the four phase detection results obtained by receiving the first and second carrier signals, and calculates one of the three first carrier signals and the other. The distance measuring device according to claim 1, wherein the two amplitude ratios of the two carrier signals are added to obtain a correction value, and the correction value is subtracted from the calculated distance. The calculation unit includes:
A first phase difference between the phases of the two or more second carrier signals obtained by the first transceiver, and a second of each phase of the two or more first carrier signals obtained by the second transceiver. The distance measuring device according to claim 5, wherein the distance is obtained by adding a phase difference. 6. The distance measuring device according to claim 1, wherein a frequency of one of the three first carrier signals is a substantially average value of frequencies of the other two carrier signals. At least one of the first and second devices has the calculation unit,
The distance measuring device according to any one of claims 1 to 7, wherein the first and second devices include a communication unit for transmitting the phase information to the calculation unit. The first and second reference signal sources generate two types of local signals,
9. The distance measuring device according to claim 1, wherein each of the first and second transmitters / receivers includes an image suppression wireless receiver using the two types of local signals. In the distance measuring method for calculating the distance based on the carrier phase detection,
In the first device, three or more first carrier signals are transmitted using the output of the first reference signal source,
In the second device, three or more second carrier signals are transmitted using the output of the second reference signal source,
In the first device, the two or more second carrier signals are received to obtain two or more first phase detection results,
In the second device, the two or more first carrier signals are received to obtain two or more second phase detection results,
Transmitting the first and second phase detection results to a calculation unit;
In the calculation unit, the distance between the first device and the second device is calculated based on the first and second phase detection results, and the calculated distance is received by the second transceiver. A distance measuring method for correcting based on information on an amplitude ratio between first carrier signals. The first transceiver transmits the first wave of the first carrier signal using the output of the first reference signal source, then transmits the second wave, and then transmits the first wave again,
The second transmitter / receiver sequentially receives the first wave, the second wave, and the first wave transmitted from the first transmitter / receiver using the output of the second reference signal source, and then receives the second carrier. Send the first wave of the signal, then send the second wave, then send the first wave again,
The first transmitter / receiver sequentially receives the first wave, the second wave, and the first wave transmitted from the second transmitter / receiver using the output of the first reference signal source, and then receives the first carrier. Send the third wave of the signal,
The second transceiver transmits the third wave of the second carrier signal after receiving the third wave from the first transceiver using the output of the second reference signal source,
2. The distance measuring apparatus according to claim 1, wherein the first transmitter / receiver receives a third wave transmitted from the second transmitter / receiver using an output of the first reference signal source. The first transceiver transmits a first wave of the first carrier signal using an output of the first reference signal source after carrier sensing of the first wave of the first carrier signal,
The second transmitter / receiver transmits the first wave of the second carrier signal after receiving the first wave transmitted from the first transmitter / receiver using the output of the second reference signal source. Then, after the carrier sense of the first wave of the second carrier signal, the first wave of the second carrier signal is transmitted again,
The first transmitter / receiver receives the first wave transmitted from the second transmitter / receiver twice using the output of the first reference signal source, and then receives the first wave of the first carrier signal again. Transmit, then transmit a second wave of the first carrier signal after carrier sense of the second wave of the first carrier signal,
The second transmitter / receiver sequentially receives the first wave and the second wave transmitted from the first transmitter / receiver using the output of the second reference signal source, and then receives the second carrier signal. Transmit a second wave, then transmit a second wave of the second carrier signal again after carrier sensing of the second wave of the second carrier signal,
The first transmitter / receiver receives the second wave transmitted from the second transmitter / receiver twice using the output of the first reference signal source, and then receives the second wave of the first carrier signal. Send it again,
The second transmitter / receiver uses the output of the second reference signal source to receive the second wave transmitted from the first transmitter / receiver for the second time, and then receives the third wave of the second carrier signal. A third wave of the second carrier signal after the carrier sense of
The first transmitter / receiver transmits the third wave of the first carrier signal after receiving the third wave transmitted from the second transmitter / receiver using the output of the first reference signal source. ,
The distance measuring apparatus according to claim 1, wherein the second transmitter / receiver receives the third wave transmitted from the first transmitter / receiver. The first carrier signal is three carrier signals having different frequencies,
The second carrier signal is three carrier signals having frequencies respectively corresponding to the three carrier signals of the first carrier signal,
The first and second transceivers do not change the initial phase and frequency of the first and second carrier signals during a period of transmitting and receiving carrier signals having frequencies corresponding to the first and second carrier signals. The distance measuring device according to claim 1 or 2. The first carrier signal is three carrier signals having different frequencies,
The second carrier signal is three carrier signals having frequencies respectively corresponding to the three carrier signals of the first carrier signal,
The first and second reference signal sources continuously operate during a period in which carrier signals having frequencies corresponding to the first and second carrier signals are transmitted and received by the first and second transceivers. Item 3. A distance measuring device according to item 1 or 2. One of the first and second devices generates a carrier signal by adding the phase detection result obtained by receiving the carrier signal from the other device of the first and second devices to the initial phase. The distance measuring device according to claim 1, wherein the distance measuring device transmits the data to the other device. The first carrier signal is three carrier signals having different frequencies,
The second carrier signal is three carrier signals having frequencies respectively corresponding to the three carrier signals of the first carrier signal,
The first and second reference signal sources generate two types of local signals,
The first and second transceivers are configured by a heterodyne radio transceiver using the two types of local signals, and by changing the frequency of at least one type of local signals of the two types of local signals. The frequency of the first and second carrier signals can be changed;
The first and second reference signal sources continuously generate the two kinds of local signals during a period in which carrier signals having frequencies corresponding to each other of the first and second carrier signals are transmitted and received. The distance measuring apparatus according to 1. The first carrier signal is three carrier signals having different frequencies,
The second carrier signal is three carrier signals having frequencies respectively corresponding to the three carrier signals of the first carrier signal,
The first and second reference signal sources generate one type of local signal;
The first and second transmitters / receivers are configured by direct conversion type radio transmitter / receivers using the one type of local signal, and the first and second types of the first and second transmitters / receivers are changed by changing the frequency of the one type of local signal. The frequency of the carrier signal can be changed,
The first and second reference signal sources continuously generate the one type of local signals during a period in which carrier signals having frequencies corresponding to each other of the first and second carrier signals are transmitted and received. The distance measuring apparatus according to 1. The calculation unit calculates the distance based on the four phase detection results obtained by receiving the first and second carrier signals, and calculates one of the three first carrier signals and the other. When the two amplitude ratios are smaller than a predetermined first threshold or larger than a predetermined second threshold, the first and second carrier signals are calculated. 6. The distance measuring device according to claim 1, wherein the distance measurement is performed again after resetting the frequency.

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