JP2018194328A - Propagation distance estimating device - Google Patents

Abstract

To provide a propagation distance estimating device with which it is possible to effectively correct a signal in estimating a propagation distance.SOLUTION: A terminal 2 includes a switching unit 50 for switching between a first state in which a signal received by a reception antenna 12 is outputted to a reception filter and a signal outputted by a transmission filter is transmitted from a transmission antenna 23 and a second state in which a signal outputted by the transmission filter is inputted to the reception filter. A signal processing unit 18, when performing calibration, switches the switching unit 50 to the second state and thereby causes a signal outputted from the signal processing unit 18 to be inputted to the signal processing unit 18 after being passed through the inside of the terminal 2 and compares the outputted signal with the inputted signal to calculate a correction value and, when performing distance measurement communication to estimate a propagation distance, switches the switching unit 50 to the first state and transmits the correction value to a communication device, as well as returns a distance measurement signal transmitted from the communication device. The communication device corrects the distance measurement signal transmitted from the terminal 2 with the correction value transmitted from the terminal 2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a propagation distance estimation apparatus that estimates a propagation distance between a terminal and a communication apparatus.

  2. Description of the Related Art Conventionally, an electronic key system that performs ID verification by wirelessly transmitting a key ID from an electronic key to a vehicle in a vehicle or the like is well known. By the way, in this kind of electronic key system, an illegal act using a repeater (refer to Patent Document 1, etc.) as an illegal act intended to establish ID verification without depending on the user's will. There is. For example, when the electronic key is located at a location far from the vehicle, the repeater use fraudulent act is an act of establishing a communication between these two parties by connecting the electronic key to the vehicle by a plurality of repeaters and relaying radio waves. is there. Therefore, since ID verification is established without the user's knowledge, there is a possibility that the door is unlocked or the engine is illegally operated by a third party.

  Therefore, a propagation distance estimation device that transmits a radio wave from a base station to a terminal, retransmits the radio wave from the terminal that has received the radio wave to the base station, and estimates a propagation time from the signal received by the base station (see Patent Document 2) Is considered to be applied to an electronic key system. The electronic key system can calculate the propagation distance from the vehicle to the electronic key by multiplying the propagation time measured by the propagation distance estimation device with the speed of light. It becomes possible to determine that there is an act.

JP 2006-161545 A JP 2014-159585 A

In the propagation distance estimation apparatus, a delay is generated by a circuit such as a filter in the terminal, which may affect the estimation of the propagation distance, so that signal correction is necessary.
An object of the present invention is to provide a propagation distance estimation apparatus capable of effectively correcting a signal in estimating a propagation distance.

  A propagation distance estimation device that solves the above problem combines a plurality of continuous waves of different frequencies in a communication device, transmits this as a ranging signal from the communication device to the terminal, and transmits the ranging signal from the terminal to the terminal. In the propagation distance estimation device that causes the communication device to return and estimate the propagation distance of the distance measurement signal, the terminal includes a reception antenna that receives the distance measurement signal, a reception filter that filters the received distance measurement signal, An A / D converter that performs A / D conversion on the signal filtered by the reception filter, a signal processing unit that processes a signal that has been A / D converted by the A / D converter, and a signal that is processed by the signal processing unit A D / A converter for A conversion, a transmission filter for filtering a signal D / A converted by the D / A converter, and the transmission filter for filtering A transmission antenna that transmits the transmitted signal; a first state in which a signal received by the reception antenna is output to the reception filter; and a signal that is output from the transmission filter is transmitted from the transmission antenna; and the transmission filter outputs A switching unit that switches between a second state and a second state in which the received signal is input to the reception filter, and the signal processing unit switches the switching unit to the second state when performing calibration, The signal output from the signal processing unit is passed through the terminal and input to the signal processing unit, and the correction value is calculated by comparing the output signal with the input signal, and the propagation distance is estimated. When performing ranging communication, the switching unit is switched to the first state, the correction value is transmitted to the communication device, and the ranging signal transmitted from the communication device is transmitted. The reply, the communication device by the correction value transmitted from the terminal, corrects the ranging signal transmitted from the terminal.

  According to the above configuration, the delay of the signal in the terminal is calculated as a correction value by switching the switching unit of the terminal between the first state and the second state, and the communication device corrects the distance measurement signal using this correction value. Therefore, correction can be performed effectively.

  Regarding the propagation distance estimation apparatus, the first state is a state in which the reception antenna and the reception filter are connected, and the transmission antenna and the transmission filter are connected, and the second state is: It is preferable that the reception filter and the transmission filter are connected.

  According to the above configuration, the reception antenna receives the ranging signal transmitted from the communication device by connecting the reception antenna and the reception filter and setting the transmission antenna and the transmission filter in the first state. Thus, the ranging signal can be transmitted from the transmission antenna via the reception filter and the transmission filter. Further, by connecting the reception filter and the transmission filter, it is possible to make a circuit in which the terminal is closed, and it is possible to calculate the communication time of a signal that makes one round in the circuit.

  For the propagation distance estimation apparatus, the switching unit includes a first switch that switches between the reception antenna and the transmission filter connected to the reception filter, the transmission antenna connected to the transmission filter, and the transmission filter. It is preferable to include a second switch that switches between the receiving antenna and the receiving antenna.

According to the above configuration, the first state and the second state can be switched by switching the first switch and the second switch.
In the propagation distance estimation apparatus, the switching unit includes a connection line that connects the first switch and the second switch, and the first switch connects the reception filter and the transmission filter. Preferably, the reception filter and the connection line are connected, and the second switch connects the connection line and the transmission filter when connecting the reception filter and the transmission filter.

  According to the above configuration, by connecting the first switch and the second switch with the connection line, for example, the first switch and the second switch can be spaced apart, so that the first switch is placed near the receiving antenna. Once installed, the second switch can be installed in the vicinity of the transmitting antenna.

  According to the present invention, it is possible to effectively correct a signal in estimating a propagation distance.

The block diagram which shows schematic structure of a propagation distance estimation apparatus. The block diagram which shows the terminal of a propagation distance estimation apparatus. The block diagram which shows the terminal of a propagation distance estimation apparatus.

Hereinafter, an embodiment of a propagation distance estimation apparatus will be described with reference to FIGS.
As shown in FIG. 1, the communication device 1 and the terminal 2 are provided with a propagation distance estimation device 3 that estimates a distance (propagation distance d) required for radio wave transmission between the two parties. The propagation distance estimation device 3 is mounted, for example, in an electronic key system that performs key collation of electronic keys wirelessly. In this case, even if ID verification is established between the communication device 1 and the terminal 2, if the propagation distance d obtained by the propagation distance estimation device 3 is equal to or greater than the threshold value, the electronic key system has a possibility of unauthorized communication. If it is high, ID verification establishment is not permitted.

The communication device 1 includes a plurality of oscillators 4 (for example, N) that output complex signals f _n (p) as unmodulated continuous waves (CW waves) each having a different frequency. The complex signal f _n (p) of each frequency has “n” ranging from “1” to “N”, and has a real part and an imaginary part as signal components. Note that “n” is a number indicating what number frequency, “N” is the total number of frequencies to be used, and “p” is discrete time.

The communication device 1 includes a real number extraction unit 5 that extracts a real part from each complex signal f _n (p) input from the oscillator 4. The real number extraction unit 5 outputs a signal real (f _n (p)) by extracting the real part from the complex signal f _n (p). Note that real (·) indicates a function that extracts a real number from a complex number.

The communication device 1 adds the signal real (f _n (p)) output from the real number extraction unit 5 and the synthesized signal real (F (p)) output from the adder 6 to the D / A. And a D / A converter 7 for conversion. The communication device 1 includes a mixer 9 that multiplies the synthesized signal real (F (t)) after D / A conversion and an oscillation signal input from the local oscillator 8, a bandpass filter 10 that filters the signal after multiplication, A transmission antenna 11 is provided that transmits the combined signal that has passed through the bandpass filter 10 as a ranging signal real (F (t)) cos (ωt). “F (p)” and “F (t)” are synthesized complex signals, and “t” is a continuous time.

The terminal 2 receives the ranging signal real (F (t)) cos (ωt) transmitted from the communication device 1 with a signal delayed by the propagation time t _0, and the received signal real (F (t ( -T ₀ )) A band-pass filter 13 as a reception filter for filtering cos (ωt). The terminal 2 includes a mixer 15 that multiplies the signal that has passed through the bandpass filter 13 and the oscillation signal that is input from the local oscillator 14, a low-pass filter 16 that filters the signal after multiplication, and a received signal real that has passed through the low-pass filter 16. And an A / D converter 17 for A / D converting (F (t−t ₀ )).

The terminal 2 includes a signal processing unit 18 that operates the terminal 2 based on the received signal real (F (p−t ₀ )) input from the A / D converter 17. When receiving the received signal real (F (t−t ₀ )) cos (ωt) from the communication device 1, the signal processing unit 18 communicates the received signal real (F (t−t ₀ )) cos (ωt). The operation of returning to the device 1 is executed.

The terminal 2 includes a D / A converter 19 that D / A converts a signal input from the signal processing unit 18 when a radio wave is returned, and a mixer that multiplies the D / A converted signal and the oscillation signal input from the local oscillator 20. 21. The terminal 2 transmits a bandpass filter 22 as a transmission filter for filtering the signal after multiplication, and a signal that has passed through the bandpass filter 22 as a ranging signal real (F (t−t ₀ )) cos (ωt). A transmission antenna 23;

The communication device 1 includes a receiving antenna 24 that receives the ranging signal real (F (t−t ₀ )) cos (ωt) transmitted from the terminal 2 with a signal delayed by the propagation time t ₀ . The communication device 1 includes a band-pass filter 25, a local oscillator 26, a mixer 27, a low-pass filter 28, and an A / D converter 29 on one path following the receiving antenna 24. The band pass filter 25 filters the ranging signal real (F (t−2t ₀ )) cos (ωt) received by the receiving antenna 24. The mixer 27 multiplies the signal that has passed through the bandpass filter 25 and the oscillation signal input from the local oscillator 26. The low pass filter 28 passes only a low frequency among the signals synthesized by the mixer 27. The A / D converter 29 A / D converts the ranging signal real (F (t−2t ₀ )) that has passed through the low-pass filter 28 and outputs the ranging signal real (F (p−2t ₀ )). .

The communication device 1 includes a band-pass filter 30, a transfer device 31, a mixer 32, a low-pass filter 33, and an A / D converter 34 on the other path following the reception antenna 24. The band pass filter 30 filters the ranging signal real (F (t−2t ₀ )) cos (ωt) received by the receiving antenna 24. The mixer 32 multiplies the signal that has passed through the band-pass filter 30 by the signal obtained by delaying the oscillation signal output from the local oscillator 26 by 90 ° by the transfer device 31. The low-pass filter 33 passes only a low frequency among the signals synthesized by the mixer 32. The A / D converter 34 A / D-converts the signal that has passed through the low-pass filter 33 and outputs a distance measurement signal img (F (p−2t ₀ )). Note that img (•) indicates a function for extracting an imaginary part from a complex number.

The communication device 1 includes a complexing unit 35 that calculates a complex signal from a real part and an imaginary part. The complexing unit 35 receives the ranging signal real (F (p-2t ₀ )) input from the A / D converter 29 and the ranging signal img (F (p-2t ₀ )) input from the A / D converter 34. Based on the above, the complex signal F (p−2t ₀ ) is calculated.

The communication device 1 includes a correlation calculation unit 40 and a distance estimation unit 41 that execute a series of processes for estimating a radio wave propagation distance d between the communication device 1 and the terminal 2. The correlation calculation unit 40 multiplies the ranging signal F (p−2t ₀ ) received by the communication device 1 by the complex conjugate of f _n (p), performs a correlation calculation that takes the average, and calculates F (p Each frequency component of −2t ₀ ) is extracted. The distance estimation unit 41 estimates the propagation distance d from the phase of the frequency component extracted by the correlation calculation unit 40.

Next, the operation and effect of the propagation distance estimation apparatus 3 will be described with reference to FIGS. Note that this example is formulated assuming that no signal processing is performed on the terminal 2 side.
As shown in FIG. 1, each oscillator 4 (total number N) outputs complex signals f ₁ (p) to f _N (p) having different frequencies to the real number extraction unit 5 (n = 1 to N). The real number extraction unit 5 extracts a real part from each of the complex signals f ₁ (p) to f _N (p), and signals real (f ₁ (p)) to real (f _N (p)) constructed from only real numbers. Is output to the adder 6. The adder 6 adds these signals real (f ₁ (p)) to real (f _N (p)) into a composite signal real (F (p)), and outputs this to the D / A converter 7. The synthesized signal real (F (p)) is expressed by the following equation (1).

  The synthesized signal real (F (p)) is D / A converted by the D / A converter 7 and output to the mixer 9 as a synthesized signal real (F (t)). The synthesized signal real (F (t)) input to the mixer 9 is multiplied by the oscillation signal input from the local oscillator 8, and only a signal in a predetermined band is passed by the band pass filter 10. The combined signal real (F (t)) that has passed through the bandpass filter 10 is transmitted from the transmission antenna 11 to the terminal 2 as a distance measurement signal real (F (t)) cos (ωt).

The ranging signal real (F (t)) cos (ωt) transmitted from the transmission antenna 11 of the communication apparatus 1 reaches the terminal 2 after the propagation time t ₀ . The ranging signal real (F (t)) cos (ωt) is a repetitive signal in which a predetermined waveform generated by combining the complex signals f ₁ (p) to f _N (p) repeatedly appears. The transmission signal real (F (t)) cos (ωt) is a wideband signal.

The terminal 2 is a signal delayed by the propagation time t ₀ from the distance measurement signal real (F (t)) cos (ωt) transmitted from the communication device 1, that is, real (F (t−t ₀ )) cos (ωt). Is received by the receiving antenna 12. The received signal real (F (t−t ₀ )) cos (ωt) is output to the mixer 15 after passing through the bandpass filter 13. The reception signal real (F (t−t ₀ )) cos (ωt) input to the mixer 15 is multiplied by the oscillation signal input from the local oscillator 14, and only the low band is passed by the low-pass filter 16. The received signal real (F (t−t ₀ )) that has passed through the low-pass filter 16 is A / D converted by the A / D converter 17 and is received as a received signal real (F (p−t ₀ )) by the signal processing unit 18. Is output.

The signal processing unit 18 reads the signal waveform of the reception signal real (F (p−t ₀ )) input from the A / D converter 17. At this time, if the signal processing unit 18 can normally read the received signal real (F (p−t ₀ )), the signal of the real (F (t−t ₀ )) cos (ωt) is transmitted to the communication device 1. Then, the distance measurement signal real (F (p−t ₀ )) is output to the D / A converter 19.

D / A converter 19 is input to the transmission signal _{real (F (p-t 0} )) is converted into a transmission signal _{real (F (t-t 0} )) by the D / A conversion, it is outputted to the mixer 21 . The transmission signal real (F (t−t ₀ )) input to the mixer 21 is multiplied by the oscillation signal input from the local oscillator 20, and only a predetermined band is passed by the band pass filter 22. Then, the signal that has passed through the bandpass filter 22 is wirelessly transmitted from the transmission antenna 23 toward the communication device 1 as a distance measurement signal real (F (t−t ₀ )) cos (ωt).

The ranging signal real (F (t−t ₀ )) cos (ωt) transmitted from the transmission antenna 23 of the terminal 2 reaches the communication device 1 after the propagation time t ₀ . Here, the distance measurement signal real (F (t−t ₀ )) cos (ωt) transmitted from the terminal 2 is the distance measurement signal real (F (t)) cos transmitted from the communication apparatus 1 to the terminal 2. Although the waveform is the same as (ωt), the signal is a phase delayed by a predetermined time.

The ranging signal real (F (t−t ₀ )) cos (ωt) transmitted from the terminal 2 is communicated as a signal delayed by the propagation time t ₀ , that is, real (F (t−2t ₀ )) cos (ωt). The device 1 is reached. The distance measurement signal real (F (t−2t ₀ )) cos (ωt) is input to each of the bandpass filters 25 and 30. The ranging signal real (F (t−2t ₀ )) cos (ωt) input to the bandpass filter 25 is passed through only a predetermined band and is output to the mixer 27. The ranging signal real (F (t−2t ₀ )) cos (ωt) input to the mixer 27 is multiplied by the oscillation signal input from the local oscillator 26, and passes only in the low band by the low-pass filter 28. The distance measurement signal real (F (t−2t ₀ )) that has passed through the low-pass filter 28 is A / D converted by the A / D converter 29 and is converted into a distance measurement signal real (F (p−2t ₀ )). 35.

The ranging signal real (F (t−2t ₀ )) cos (ωt) input to the bandpass filter 30 passes only a predetermined band and is output to the mixer 32. The ranging signal real (F (t−2t ₀ )) cos (ωt) input to the mixer 32 is multiplied by the 90 ° phase-delayed oscillation signal input from the local oscillator 26, and only the low band is passed by the low-pass filter 33. Is done. The signal that has passed through the low-pass filter 33 is A / D converted by the A / D converter 34 and input to the complexing unit 35 as a distance measurement signal img (F (p−2t ₀ )).

The complexing unit 35 inputs the ranging signal real (F (p-2t ₀ )) from the A / D converter 29 and the ranging signal img (F (p-2t ₀ )) from the A / D converter 34. Then, a complex signal F (p−2t ₀ ) is calculated by complexing them. The complexing unit 35 outputs the calculated complex signal F (p−2t ₀ ) to the correlation calculation unit 40.

The correlation calculation unit 40 receives the ranging signal real (F (t)) cos (ωt) transmitted from the communication device 1 and the ranging signal real (F (t−t ₀ )) cos (ωt) received from the terminal 2. determining the difference in phase rotation amount in frequency f _n (p) to each other determined per frequency f _n (p), further next phase rotation amount occurring between the. Then, the distance estimation unit 41 calculates the propagation distance d between the communication device 1 and the terminal 2 from the phase rotation amount obtained by the correlation calculation unit 40.

  Note that the propagation distance estimation apparatus needs to correct a signal because a delay may be generated by a filter in the terminal 2 to affect the estimation of the propagation distance. In particular, when a surface acoustic wave filter (SAW filter: Surface Acoustic Wave filter) is used as the bandpass filter 22, the bandwidth is narrow and the characteristics change depending on the temperature, and the bandwidth tends to shift and delay is likely to occur. Note that some delay occurs not only in the surface acoustic wave filter but also in other filters.

  Therefore, as illustrated in FIGS. 2 and 3, the terminal 2 includes a circuit that goes around the terminal 2 in order to calculate the delay of the signal that has passed through the terminal 2. That is, the terminal 2 outputs a signal received by the receiving antenna 12 to the band-pass filter 13 on the receiving side, transmits a signal output from the band-pass filter 22 on the transmitting side from the transmitting antenna 23, The switching part 50 which switches the 2nd state which inputs the signal which the bandpass filter 22 of the side output into the bandpass filter 13 of the receiving side is provided. The first state is a state in which the reception antenna 12 and the reception-side bandpass filter 13 are connected, and the transmission antenna 23 and the transmission-side bandpass filter 22 are connected. The second state is a state in which the band-pass filter 13 on the reception side and the band-pass filter 22 on the transmission side are connected.

  The switching unit 50 is connected to the first switch 51 for switching between the reception antenna 12 connected to the band-pass filter 13 on the reception side and the band-pass filter 22 on the transmission side, and to the band-pass filter 22 on the transmission side. And a second switch 52 for switching between the transmitting antenna 23 and the receiving antenna 12. The switching unit 50 includes a connection line 53 that connects the first switch 51 and the second switch 52. The first switch 51 connects the reception-side bandpass filter 13 and one end of the connection line 53 when connecting the reception-side bandpass filter 13 and the transmission-side bandpass filter 22. The second switch 52 connects the other end of the connection line 53 and the transmission-side bandpass filter 22 when connecting the reception-side bandpass filter 13 and the transmission-side bandpass filter 22. One end of an instruction line 54 for switching the state of the first switch 51 and the second switch 52 is connected to the signal processing unit 18. The other end of the instruction line 54 is connected to the first switch 51 and the second switch 52, respectively.

  When calibrating, the signal processing unit 18 switches the switching unit 50 to the second state, thereby allowing the signal output from the signal processing unit 18 to pass through the terminal 2 once and then the signal processing unit 18. The correction value is calculated by comparing the output signal with the input signal. The correction value is calculated as the amount of change in phase and amplitude. The correction value is calculated in the same manner as the distance estimation. That is, the “output signal” is the same as the transmission signal, and the “input signal” is the same as the signal received by the vehicle-mounted device, and the frequency component is extracted by correlation calculation in the same manner as distance measurement. The extracted frequency component becomes the “correction value”. When performing the ranging communication for estimating the propagation distance, the signal processing unit 18 switches the switching unit 50 to the first state, transmits the correction value to the communication device 1, and transmits the measurement value transmitted from the communication device 1. Returns the distance signal.

The communication apparatus 1 corrects the distance measurement signal transmitted from the terminal 2 with the correction value transmitted from the terminal 2 and then estimates the propagation distance d of the distance measurement signal.
With the configuration as described above, the delay of the signal in the terminal 2 is calculated as a correction value by switching the switching unit 50 of the terminal 2 between the first state and the second state. Since the signal can be corrected, the correction can be performed effectively. Further, only the correction is calculated in the terminal 2, and it is not necessary to correct the ranging signal, so that a high-performance arithmetic processing unit is not required.

As described above, according to this embodiment, the following effects can be obtained.
(1) The delay of the signal in the terminal 2 is calculated as a correction value by switching the switching unit 50 of the terminal 2 between the first state and the second state, and the communication device 1 corrects the distance measurement signal based on this correction value. Therefore, signal correction can be performed effectively.

  (2) By connecting the receiving antenna 12 and the band-pass filter 13 on the receiving side to the first state in which the transmitting antenna 23 and the band-pass filter 22 on the transmitting side are connected, the signal is transmitted from the communication device 1. The received ranging signal can be received by the receiving antenna 12, and the ranging signal can be transmitted from the transmitting antenna 23 via the receiving-side bandpass filter 13 and the transmitting-side bandpass filter 22. In addition, by connecting the band-pass filter 13 on the reception side and the band-pass filter 22 on the transmission side, the circuit inside the terminal 2 can be closed, and the communication time of the signal that makes one round in the circuit is calculated. Can do.

(3) By switching the first switch 51 and the second switch 52, the first state and the second state can be switched.
(4) Since the first switch 51 and the second switch 52 are connected by the connection line 53, the first switch 51 and the second switch 52 can be spaced from each other. The second switch 52 can be installed in the vicinity of the transmission antenna 23.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the above embodiment, the switching unit 50 includes the connection line 53 that connects the first switch 51 and the second switch 52, but the connection line 53 is omitted and the first switch 51 and the second switch 52 are directly connected. It is good also as a 2nd state which connected the band-pass filter 13 on the receiving side, and the band-pass filter 22 on the transmitting side by connecting.

  In the above embodiment, the switching unit 50 switches the reception antenna 12 connected to the reception-side bandpass filter 13 and the transmission-side bandpass filter 22, and the transmission-side bandpass filter 22. And a second switch 52 that switches between the transmitting antenna 23 and the receiving antenna 12 connected to each other. However, the first state in which the signal received by the reception antenna 12 is output to the reception-side bandpass filter 13 and the signal output by the transmission-side bandpass filter 22 is transmitted from the transmission antenna 23, and the transmission-side bandpass The configuration of the first switch 51 and the second switch 52 is not limited as long as the switching unit 50 can switch between the second state in which the signal output from the filter 22 is input to the reception-side bandpass filter 13.

  In the above embodiment, the communication apparatus 1 corrects the distance measurement signal transmitted from the terminal 2 with the correction value transmitted from the terminal 2 and then estimates the propagation distance of the distance measurement signal. The propagation distance may be corrected with the correction value transmitted from the terminal 2 after estimating the propagation distance of the signal.

  The circuit configuration of the propagation distance estimation device 3 of the above embodiment, that is, the circuit configuration of the communication device 1 and the terminal 2 is not limited to the configuration described in the embodiment, and can be changed elsewhere. Further, the communication device 1 may be a base station.

In the above-described embodiment, various methods such as the MUSIC method can be used for the calculation for estimating the propagation distance d (propagation time t ₀ ) from the phase of the radio wave.
In the above embodiment, the propagation distance estimation device 3 is not limited to being mounted on the electronic key system, and can be applied to other systems and devices.

-The continuous wave of the said embodiment is not limited to being handled as a complex signal, A various system is employable.
The continuous wave of the above embodiment is not limited to a non-modulated wave but may be a signal subjected to various modulations as long as the frequency bands of the respective f _k (p) do not overlap.

-The continuous wave of the said embodiment does not need to be a continuous signal from the start to the end of transmission, and may be a signal interrupted suitably.
-The signal processing part 18 of the terminal 2 of the said embodiment may implement a signal processing with the communication apparatus 1 by a known method. Thereby, for example, it is possible to prevent a method in which the repeater disguises the propagation distance d (propagation time t ₀ ) by directly transmitting a signal for propagation distance measurement to the communication device 1.

And Propagation distance estimation apparatus 3 in the embodiment above is not limited to the apparatus for estimating the propagation distance d, for example, it may be an apparatus for estimating the propagation time t _0.

  DESCRIPTION OF SYMBOLS 1 ... Communication apparatus, 2 ... Terminal, 3 ... Propagation distance estimation apparatus, 4 ... Oscillator, 5 ... Real number extraction part, 6 ... Adder, 7 ... D / A converter, 8 ... Local oscillator, 9 ... Mixer, 10 ... Band Path filter, 11 ... Transmit antenna, 12 ... Receive antenna, 13 ... Band pass filter, 14 ... Local oscillator, 15 ... Mixer, 16 ... Low pass filter, 17 ... A / D converter, 18 ... Signal processor, 19 ... D / A converter, 20 ... local oscillator, 21 ... mixer, 22 ... bandpass filter, 23 ... transmitting antenna, 24 ... receiving antenna, 25,30 ... bandpass filter, 26 ... local oscillator, 27,32 ... mixer, 28,33 ... Low-pass filter, 29, 34 ... A / D converter, 35 ... Complexation unit, 40 ... Correlation calculation unit, 41 ... Distance estimation unit, 50 ... Switching unit, 51 ... First switch, 5 ... second switch, 53 ... connecting lines 54 ... indicator line.

Claims (4)

A plurality of continuous waves having different frequencies are synthesized in the communication device, and this is transmitted as a ranging signal from the communication device to the terminal, the ranging signal is returned from the terminal to the communication device, and the ranging signal In the propagation distance estimation device for estimating the propagation distance,
The terminal includes a receiving antenna that receives the ranging signal, a receiving filter that filters the received ranging signal, an A / D converter that performs A / D conversion on the signal filtered by the receiving filter, and the A / D A signal processing unit that processes the signal A / D converted by the D converter, a D / A converter that D / A converts the signal processed by the signal processing unit, and a signal that is D / A converted by the D / A converter A transmission filter for filtering, a transmission antenna for transmitting a signal filtered by the transmission filter, a signal received by the reception antenna is output to the reception filter, and a signal output by the transmission filter is transmitted from the transmission antenna. The first state is switched between the second state in which the signal output from the transmission filter is input to the reception filter. Includes a switching unit changing, the,
When performing calibration, the signal processing unit switches the switching unit to the second state, and passes the signal output from the signal processing unit to the signal processing unit after passing through the terminal. When the distance measurement communication for estimating the propagation distance is performed by calculating the correction value by comparing the output signal with the input signal, the switching unit is switched to the first state, A correction value is transmitted to the communication device, and the ranging signal transmitted from the communication device is returned.
The communication apparatus corrects the ranging signal transmitted from the terminal based on the correction value transmitted from the terminal. The first state is a state in which the reception antenna and the reception filter are connected, and the transmission antenna and the transmission filter are connected,
The propagation distance estimation apparatus according to claim 1, wherein the second state is a state in which the reception filter and the transmission filter are connected. The switching unit includes a first switch that switches between the reception antenna and the transmission filter connected to the reception filter, and a second switch that switches between the transmission antenna and the reception antenna connected to the transmission filter. The propagation distance estimation apparatus according to claim 2, comprising: a switch. The switching unit includes a connection line that connects the first switch and the second switch,
The first switch connects the reception filter and the connection line when connecting the reception filter and the transmission filter;
The propagation distance estimation apparatus according to claim 3, wherein the second switch connects the connection line and the transmission filter when connecting the reception filter and the transmission filter.

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