JP2018194329A - Propagation distance estimating device - Google Patents

Abstract

To provide a propagation distance estimating device with which it is possible to effectively perform corrections on a circuit.SOLUTION: A terminal 2 includes a switching unit 50 for switching between a first state, a second state and a third state. A signal processing unit 18, when performing calibration, switches the switching unit 50 to the second state and the third state and thereby transmits a signal having passed through a reception filter and a signal not having passed through the reception filter from a transmission antenna 23 and, when performing distance measurement communication to estimate a propagation distance, switches the switching unit 50 to the first state and returns a distance measurement signal transmitted from a communication device 1. The communication device 1 compares the signal transmitted in the second state of the switching unit 50 with the signal transmitted in the third state and thereby calculates a correction value and corrects the distance measurement signal transmitted from the terminal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a propagation distance estimation apparatus that measures 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 device, a delay may occur due to a circuit such as a filter, which may affect the estimation of the propagation distance, so that signal correction is necessary and there is room for improvement.
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 returns the communication device to estimate the propagation distance of the distance measurement signal,
The terminal includes a reception antenna that receives the ranging signal, a reception filter that filters the received ranging signal, a transmission filter that filters a signal filtered by the reception filter, and a signal that is filtered by the transmission filter. A transmitting antenna for transmitting, a signal processing unit for processing a signal, a D / A converter for D / A converting the signal processed by the signal processing unit, and outputting a signal received by the receiving antenna to the reception filter A first state in which a signal output from the reception filter is input to the transmission filter; a signal output from the D / A converter is input to the reception filter; and a signal output from the reception filter is input to the transmission filter The second state input to the filter and the signal output from the D / A converter A switching unit that switches between a third state that is input to the transmission filter, and the signal processing unit switches the switching unit between the second state and the third state when performing calibration. Then, when performing distance measurement communication in which a signal that has passed through the reception filter and a signal that has not passed through the reception filter are transmitted from the transmission antenna to estimate a propagation distance, the switching unit is in the first state. The distance measurement signal transmitted from the communication device is returned, and the communication device compares the signal transmitted in the second state of the switching unit with the signal transmitted in the third state. Thus, a correction value is calculated, and the distance measurement signal transmitted from the terminal is corrected.

  According to the above configuration, by switching the switching unit of the terminal between the second state and the third state, the signal delay due to the reception filter in the terminal can be transmitted to the communication apparatus as a different signal. And a communication apparatus calculates a correction value from a different signal, and a communication apparatus can correct | amend a ranging signal by this correction value, and can correct | amend a signal 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 reception filter and the transmission filter are connected, and the second state is: The D / A converter and the reception filter are connected, and the reception filter and the transmission filter are connected, and the third state is that the D / A converter and the transmission filter are The connected state is preferable.

  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, the signal output from the D / A converter passes through the reception filter in the second state in which the signal passes through the reception filter and the third state in which the signal output from the D / A converter does not pass through the reception filter. A signal including a delay and a signal not including a delay can be transmitted from the transmission antenna.

  In the propagation distance estimation apparatus, the switching unit includes a first switch that switches between the reception antenna connected to the reception filter and the D / A converter, and the reception filter connected to the transmission filter. And a second switch for switching between the D / A converter.

  According to the above configuration, the first state, the second state, and the third state can be switched by switching the first switch and the second switch.

  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 (ω ₁ t). “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 (ω ₁ t) 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 (ω ₁ t). 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.

When the terminal 2 receives the received signal real (F (t−t ₀ )) cos (ω ₁ t) from the communication apparatus 1, the received signal real (F (t−t ₀ )) cos (ω ₁ t) Is returned to the communication apparatus 1.
The terminal 2 uses a band-pass filter 22 as a transmission filter for filtering the signal after multiplication by the mixer 15, and a distance measurement signal real (F (t−t ₀ )) cos (ω ₂ t) and a transmission antenna 23 for transmission.

The communication device 1 includes a receiving antenna 24 that receives the distance measurement signal real (F (t−t ₀ )) cos (ω ₂ t) transmitted from the terminal 2 as 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 (ω ₂ t) 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 (ω ₂ t) 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).

合成信号real(F(p))は、Ｄ／Ａコンバータ７によってＤ／Ａ変換され、合成信号real(F(t))としてミキサ９に出力される。ミキサ９に入力された合成信号real(F(t))は、局部発振器８から入力する発振信号と乗算され、バンドパスフィルタ１０により所定帯域の信号のみが通過される。バンドパスフィルタ１０を通過した合成信号real(F(t))は、測距信号real(F(t))cos(ω₁t)として送信アンテナ１１から端末２に向けて送信される。

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 synthesized signal real (F (t)) that has passed through the bandpass filter 10 is transmitted from the transmitting antenna 11 toward the terminal 2 as a distance measurement signal real (F (t)) cos (ω ₁ t).

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

The terminal 2 receives the distance measurement signal real (F (t)) cos (ω ₁ t) transmitted from the communication device 1 from the signal delayed by the propagation time t ₀ , that is, real (F (t−t ₀ )) cos ( The signal is received by the receiving antenna 12 as ω ₁ t). The received signal real (F (t−t ₀ )) cos (ω ₁ t) is output to the mixer 15 after passing through the band-pass filter 13. The received signal real (F (t−t ₀ )) cos (ω ₁ t) input to the mixer 15 is multiplied by the oscillation signal input from the local oscillator 14, and passes only a predetermined band 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 to the communication device 1 as a distance measurement signal real (F (t−t ₀ )) cos (ω ₂ t).

The ranging signal real (F (t−t ₀ )) cos (ω ₂ t) 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 (ω ₂ t) transmitted from the terminal 2 is the distance measurement signal real (F (t)) transmitted from the communication apparatus 1 to the terminal 2. ) Although the waveform is the same as cos (ω ₁ t), the signals are different in center frequency and delayed in phase by a predetermined time.

The ranging signal real (F (t−t ₀ )) cos (ω ₂ t) transmitted from the terminal 2 is a signal delayed by the propagation time t ₀ , that is, real (F (t−2t ₀ )) cos (ω ₂ The communication device 1 is reached as t). The distance measurement signal real (F (t−2t ₀ )) cos (ω ₂ t) is input to each of the bandpass filters 25 and 30. The ranging signal real (F (t−2t ₀ )) cos (ω ₂ t) input to the band pass 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 (ω ₂ t) 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 (ω ₂ t) input to the band pass filter 30 passes only a predetermined band and is output to the mixer 32. The ranging signal real (F (t−2t ₀ )) cos (ω ₂ t) input to the mixer 32 is multiplied by the 90 ° phase-delayed oscillation signal input from the local oscillator 26, and the low-pass filter 33 reduces the low band. Only passed through. 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 uses the phase rotation amount generated between the ranging signal F (p) transmitted from the communication device 1 and the ranging signal F (p−2t ₀ ) received from the terminal 2 as the frequency f _n. It is obtained every (p), and the difference in the amount of phase rotation at the adjacent frequency f _n (p) is obtained. 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 13, 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.

  Accordingly, as illustrated in FIGS. 1 to 3, the terminal 2 receives the band-pass filter 13 on the reception side in order to calculate the delay of the signal caused by passing through the band-pass filter 13 on the reception side provided in the terminal 2. And a circuit that does not pass through the band-pass filter 13 on the receiving side. That is, the terminal 2 includes a signal processing unit 18 that outputs a signal, a D / A converter 19 that performs D / A conversion on the signal output from the signal processing unit 18, a signal that is input from the D / A converter 19, and a local oscillator 20 is provided with a mixer 21 that multiplies the oscillation signal input from 20. The signal output from the mixer 21 is input via a connection line 53 to a circuit that passes through the reception-side bandpass filter 13 and a circuit that does not pass through the reception-side bandpass filter 13. The terminal 2 outputs the signal received by the receiving antenna 12 to the band-pass filter 13 on the reception side, and outputs the signal output from the band-pass filter 13 on the reception side to the band-pass filter 22 on the transmission side via the mixer 15. The first state to be input and the signal output from the D / A converter 19 are input to the reception-side bandpass filter 13 via the mixer 21 and the signal output from the reception-side bandpass filter 13 is input to the mixer 15. Between the second state that is input to the band-pass filter 22 on the transmission side via the first and the third state that the signal output from the D / A converter 19 is input to the band-pass filter 22 on the transmission side via the mixer 21. And a switching unit 50. The first state is a state in which the reception antenna 12 and the reception-side bandpass filter 13 are connected, and the reception-side bandpass filter 13 and the transmission-side bandpass filter 22 are connected via the mixer 15. is there. In the second state, the D / A converter 19 and the reception-side bandpass filter 13 are connected via the mixer 21, and the reception-side bandpass filter 13 and the transmission-side bandpass filter 22 are connected. State. The third state is a state in which the D / A converter 19 and the transmission-side band pass filter 22 are connected via the mixer 21 and the mixer 15.

  The switching unit 50 includes a first switch 51 that switches between the reception antenna 12 connected to the band-pass filter 13 on the reception side and the D / A converter 19, and the reception antenna 12 and D connected to the transmission antenna 23. / A converter 19 and a second switch 52 for switching. The connection line 53 branches from the mixer 21 and is connected to the first switch 51 and the second switch 52. 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 between the second state and the third state, so that the signal passing through the reception-side bandpass filter 13 and the reception-side bandpass filter 13 are changed. A signal that has not passed is transmitted from the transmission antenna 23. When performing the ranging communication for estimating the propagation distance, the signal processing unit 18 switches the switching unit 50 to the first state and returns the ranging signal transmitted from the communication device 1.

  The communication device 1 calculates the correction value by comparing the signal transmitted in the second state of the switching unit 50 and the signal transmitted in the third state, and corrects the ranging signal transmitted from the terminal 2 Above, the propagation distance d of the ranging signal is estimated.

Specifically, the output of the D / A converter 19 is F (t−t ₁ ), and the output of the mixer 21 is real {F (t−t ₁ )} cos (ω ₁ t). Here, t ₁ is a time representing a difference in reference time between the communication device 1 and the terminal 2. The D / A converter 19 outputs an IQ signal (complex signal), and the mixer 21 is an IQ mixer.

As shown in FIG. 3, when the signal does not pass through the bandpass filter 13, the signal that has passed through the bandpass filter 22 from the mixer 15 becomes real {F (t−t ₁ )} cos (ω ₂ t). The received signal 1 is real {F (t−t ₀ −t ₁ )} cos (ω ₂ t), and the signal that is complexed by A / D conversion is F (p−t ₀ −t ₁ ). Become. When the distance is measured using the above signal, a distance d ₁ corresponding to the delay time (t ₀ + t ₁ ) is calculated.

As shown in FIG. 2, when the signal passes through the bandpass filter 13, the signal that has passed through the bandpass filter 13 becomes real {F (t−t ₁ −t ₂ )} cos (ω ₁ t), and the mixer 15 The signal that has passed through the band-pass filter 22 is real {F (t−t ₁ −t ₂ )} cos (ω ₂ t), and the received signal of the communication apparatus 1 is real {F (t−t ₀ −t ₁ − t ₂ )} cos (ω ₂ t), and the signal that has been A / D converted and complexed becomes F (p−t ₀ −t ₁ −t ₂ ). Here, t ₂ is a delay time by the band pass filter 13. When the distance is measured using the above signal, a distance d ₂ corresponding to the delay time (t ₀ + t ₁ + t ₂ ) is calculated.

(d ₁ -d ₂ ) is a distance according to the delay time t ₂ by the bandpass filter 13. Therefore, if (d ₁ -d ₂ ) is subtracted during distance measurement, distance measurement can be performed without the influence of the delay of the bandpass filter 13.

  With the configuration as described above, the switching unit 50 of the terminal 2 is switched between the second state and the third state, so that the signal delay caused by the band-pass filter 13 on the receiving side in the terminal 2 is transmitted to the communication device 1 as a different signal. can do. Then, the communication device 1 calculates a correction value from different signals, and the communication device 1 can correct the distance measurement signal based on the correction value, thereby effectively correcting the signal. Further, since the terminal 2 only transmits different signals and does not need to correct the ranging signal, a high-performance arithmetic processing unit is not required.

As described above, according to this embodiment, the following effects can be obtained.
(1) By switching the switching unit 50 of the terminal 2 between the second state and the third state, the signal delay by the band-pass filter 13 on the receiving side in the terminal 2 can be transmitted to the communication device 1 as a different signal. . Then, the communication device 1 calculates a correction value from different signals, and the communication device 1 can correct the distance measurement signal based on the correction value, thereby effectively correcting the signal.

  (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. Further, the second state where the signal output from the D / A converter 19 passes through the reception-side bandpass filter 13 and the second state where the signal output from the D / A converter 19 does not pass through the reception-side bandpass filter 13. Depending on the three states, a signal including a delay due to passing through the band-pass filter 13 on the reception side and a signal not including the delay can be transmitted from the transmission antenna 23.

(3) By switching the first switch 51 and the second switch 52, it is possible to switch between the first state, the second state, and the third state.
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 switches the reception antenna 12 connected to the reception-side bandpass filter 13 and the D / A converter 19, and the transmission-side bandpass filter 22. And a second switch 52 for switching between the reception-side bandpass filter 13 and the D / A converter 19. However, the first state in which the signal received by the reception antenna 12 is output to the band-pass filter 13 on the reception side and the signal output from the band-pass filter 13 on the reception side is input to the band-pass filter 22 on the transmission side, and D A second state in which the signal output from the / A converter 19 is input to the band-pass filter 13 on the reception side and the signal output from the band-pass filter 13 on the reception side is input to the band-pass filter 22 on the transmission side; If the switching unit 50 can switch between the third state in which the signal output from the D / A converter 19 is input to the band-pass filter 22 on the transmission side, the first switch 51 and the second switch 52 are configured. Not exclusively.

  In the above embodiment, the propagation distance of the distance measurement signal is estimated after correcting the distance measurement signal transmitted from the terminal 2 with the correction value calculated by the communication apparatus 1. And the propagation distance may be corrected by the calculated correction value.

  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, 18 ... Signal processor, 19 ... D / A converter, 20 ... Local oscillator, 21 ... Mixer, 22 ... band pass filter, 23 ... transmitting antenna, 24 ... receiving antenna, 25, 30 ... band pass filter, 26 ... local oscillator, 27, 32 ... mixer, 28, 33 ... low pass filter, 29, 34 ... A / D converter 35 ... complexing unit, 40 ... correlation calculating unit, 41 ... distance estimating unit, 50 ... switching unit, 51 ... first switch, 52 ... second switch, 53 ... connection line, 54 ... indicating line.

Claims (3)

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 reception antenna that receives the ranging signal, a reception filter that filters the received ranging signal, a transmission filter that filters a signal filtered by the reception filter, and a signal that is filtered by the transmission filter. A transmitting antenna for transmitting, a signal processing unit for processing a signal, a D / A converter for D / A converting the signal processed by the signal processing unit, and outputting a signal received by the receiving antenna to the reception filter A first state in which a signal output from the reception filter is input to the transmission filter; a signal output from the D / A converter is input to the reception filter; and a signal output from the reception filter is input to the transmission filter The second state input to the filter and the signal output from the D / A converter And a switching unit for switching, and a third state to be input to the transmission filter,
When the calibration is performed, the signal processing unit switches the switching unit between the second state and the third state, so that a signal that has passed through the reception filter and a signal that has not passed through the reception filter Is transmitted from the transmitting antenna, and when performing ranging communication to estimate the propagation distance, the switching unit is switched to the first state, the ranging signal transmitted from the communication device is returned,
The communication device calculates a correction value by comparing the signal transmitted in the second state of the switching unit with the signal transmitted in the third state, and the distance measurement transmitted from the terminal Propagation distance estimation device that corrects signals. The first state is a state in which the reception antenna and the reception filter are connected, and the reception filter and the transmission filter are connected,
The second state is a state in which the D / A converter and the reception filter are connected, and the reception filter and the transmission filter are connected,
The propagation distance estimation apparatus according to claim 1, wherein the third state is a state in which the D / A converter and the transmission filter are connected. The switching unit includes a first switch that switches between the reception antenna connected to the reception filter and the D / A converter, and the reception filter and D / A converter connected to the transmission filter. The propagation distance estimation apparatus according to claim 2, further comprising: a second switch that switches between the two.

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