JP4819067B2 - Distance measuring device - Google Patents

Description

  The present invention relates to an apparatus for transmitting and receiving a high frequency between two transceivers and measuring a distance between the two transceivers.

In order to measure the distance to an object that reflects electromagnetic waves, a configuration in which a transceiver forms a phase-locked loop with the object to be reflected is described in Patent Document 1 below.
In addition, the inventor forms a phase-locked loop between two transceivers with a set of two transceivers, and places a rectangular wave of about several MHz on a high-frequency carrier wave of several hundreds to several GHz, which is several megahertz. An application for detecting a phase delay of a rectangular wave of a certain degree has been filed (Japanese Patent Application No. 2006-206352, Japanese Patent Application Laid-Open No. 2007-148797).
JP2004-198306

The present inventors consider application of the above-described distance measuring device as a device that detects the position of a walking worker who is difficult to see from a driver of a transport vehicle such as a forklift in a warehouse, for example. In this case, it is necessary to transmit high frequencies of different frequencies each having a narrow band from a plurality of transport vehicles.
Accordingly, an object of the present invention is to transmit and receive a high frequency between two transmitters / receivers using a transmission wave having a narrow band and measure a distance between the two transmitters / receivers.

The invention according to claim 1 is an apparatus for measuring a distance between the first transceiver and the second transceiver, comprising the first transceiver and the second transceiver.
The first transceiver is
A voltage controlled oscillator that outputs a sine wave;
A first high frequency generator for outputting a sine wave having a preset frequency;
A first modulator that modulates the output of the first high-frequency generator by the output of the voltage-controlled oscillator to generate a double sideband;
A first transmitting antenna for transmitting the output of the first modulator;
A first receiving antenna;
A first synchronous demodulator for demodulating a signal by synchronous demodulation from both sidebands received by the first receiving antenna;
A fixed frequency oscillator that outputs a sine wave of a predetermined frequency,
The second transceiver is
A second receiving antenna;
A second synchronous demodulator that demodulates the signal from the received double sideband waves by synchronous demodulation;
A second high frequency generator for outputting a sine wave having a preset frequency;
A second modulator that modulates the output of the second high-frequency generator by the output of the second synchronous demodulator to generate a double sideband;
A second transmitting antenna for transmitting the output of the second modulator;
The voltage controlled oscillator of the first transmitter / receiver has a phase-locked loop composed of the first transmitter / receiver and the second transmitter / receiver, and the output of the first synchronous demodulator matches the phase of the output of the fixed frequency oscillator. Is controlled to
A distance measuring device that measures a distance between a first transceiver and a second transceiver by comparing a phase of an output of a voltage controlled oscillator and a phase of an output of a fixed frequency oscillator.
In the present invention, the transmitting antenna and the receiving antenna are not necessarily independent antennas. For example, by using a circulator or a duplexer, a configuration may be adopted in which antennas for both transmission and reception are provided one by one in the first transceiver and / or the second transceiver.

  Further, in the invention according to claim 2, two or more first transceivers according to claim 1 are prepared, and a first high frequency generator included in each of the first transceivers. The high-frequency frequencies output from the second transceivers are different from each other, and the high-frequency frequencies output from the second high-frequency generators of the second transceivers are different from each other. The first stage includes a frequency converter composed of a variable high-frequency generator and a mixer, two band-pass filters to which the output of the frequency converter is input, and an adder that adds the outputs of the two band-pass filters. And the center frequency of the two bandpass filters differs by twice the frequency of the sine wave of the voltage controlled oscillator output, and each first transceiver determines whether the other first transceiver is transmitting. Each having a detector, and each first transceiver comprises a detector Therefore, when it is determined that any one of the other first transceivers is transmitting, it is determined that neither of the other first transceivers is transmitting, without transmitting the double sideband. In this case, both sideband waves are transmitted.

  When using a double sideband wave that has been modulated with a sine wave, ideally, two narrowband high frequencies, the sum of the frequency of the carrier wave that is a high frequency and the frequency of the sine wave that is the signal wave, and the difference frequency only. It will be sent and received. This is demodulated synchronously, and a double sideband wave obtained by modulating a high frequency of another frequency with a sine wave as a signal wave is returned. By further synchronously demodulating this, the distance between the two transceivers can be detected as a phase difference of a sine wave that is a signal wave. At this time, if the frequency of the sine wave is set to f, the range of the detectable distance L is 2Lf / c (c is the speed of light).

In the present invention, a phase locked loop (PLL) is formed between the two transceivers to detect the phase difference, so that the output is stabilized.
According to the configuration of claim 2, any one of the plurality of first transceivers modulates a carrier wave with a sine wave that is a signal wave and transmits the modulated signal. Each of the plurality of second transceivers returns with a carrier wave having a different frequency. The first transmitter / receiver that performed the transmission demodulates the reply from each second transmitter / receiver in order, for example, by time division, and confirms the phase difference of the signal wave, and the distance from each second transmitter / receiver Can be measured. In the present invention, the frequency setting of the carrier wave of each second transmitter / receiver may be suitably performed by converting each of the double sideband waves into a band filter having a relatively narrow bandwidth after conversion to the intermediate frequency band. . A specific example will be described in the second embodiment.

Hereinafter, specific embodiments of the present invention will be described with reference to block diagrams. As each component described in the block diagram, any available component can be used as long as it has a necessary action. Of course, it is within the scope of the present invention to replace each component or add another component without departing from the spirit of the present invention. For example, a sine wave and a rectangular wave can be exchanged without a phase difference, and such components may be added.
In the following, it is assumed that the low-pass filter (LPF) and the band-pass filter (BPF) are appropriately designed in accordance with the gist of each component at the place where the low-pass filter (LPF) and the band pass filter (BPF) are arranged.
In the configuration of the following embodiment, only a configuration having two independent transmission antennas and reception antennas is shown for convenience of explanation. However, in the implementation of the present invention, the transmission antenna and the reception antenna are not necessarily independent antennas. For example, by using a circulator or a duplexer, a configuration may be adopted in which antennas for both transmission and reception are provided one by one in the first transceiver and / or the second transceiver.

  FIG. 1 is a block diagram showing a specific configuration of a first transceiver 100 and a second transceiver 200 according to a specific embodiment of the present application.

In the configuration of the first transceiver 100 in FIG. 1, the transmission part is as follows.
A sine wave having a fixed frequency f is output from the fixed frequency oscillator 10. The output of the fixed frequency oscillator 10 is input to the phase comparators 11 and 18 and the first high frequency generator 14.

  The phase comparator 11 forms a large phase-locked loop (PLL) that passes through the low-pass filter 12, the voltage-controlled oscillator 13, and the propagation paths of the first transceiver 100 and the second transceiver 200. The output of the bandpass filter 163 is input to the phase comparator 11. In this way, the phase of the sine wave of the frequency f output from the voltage controlled oscillator 13 is advanced so that the phase of the output of the bandpass filter 163 matches the phase of the output of the fixed frequency oscillator 10.

The sine wave of frequency f output from the voltage controlled oscillator 13 is input to the mixer 15 (first modulator). The mixer 15 can be composed of a double balanced mixer. The mixer 15 receives a high frequency having a frequency Nf (N >> 1) from the first high frequency generator 14. Thus, the double sideband wave (DSB (Nf)) only in the vicinity of the frequency Nf is transmitted from the output of the mixer 15 by the band filter 161 and transmitted from the first transmitting antenna A _T1 to the second transceiver 200. The carrier wave with the frequency Nf may be completely suppressed or coexist without being suppressed. Although not shown in detail, the first high frequency generator 14 can be configured by a phase locked loop (PLL) including, for example, a phase comparator, a low-pass filter, a voltage controlled oscillator, and a frequency divider.

The configuration of the second transceiver 200 in FIG. 1 is as follows.
The double sideband wave (DSB (Nf)) near the frequency Nf received by the second receiving antenna A _2R is transmitted only near the frequency Nf by the band filter 262, synchronously demodulated by the second synchronous demodulator 27, and band filtered. The sine wave having the frequency f is demodulated through the filter 263. The demodulated sine wave of frequency f is input to the mixer 25 (second modulator). Although details are not shown as the second synchronous demodulator 27, any known synchronous demodulator can be adopted in addition to the Costas loop.
A sine wave of frequency f is output from the fixed frequency oscillator 20, and a high frequency of frequency Mf (M >> 1 and M ≠ N) is generated by the second high frequency generator 24 and input to the mixer 25. Thus, the output of the mixer 25 is transmitted through the band filter 261 through the double sideband wave (DSB (Mf)) only in the vicinity of the frequency Mf, and transmitted from the second transmitting antenna A _T2 to the first transceiver 100. The carrier wave with the frequency Mf may be completely suppressed or coexist without being suppressed. Although not shown in detail, the second high-frequency generator 24 can be configured by a phase-locked loop (PLL) including, for example, a phase comparator, a low-pass filter, a voltage-controlled oscillator, and a frequency divider.

The configuration of the receiving part of the first transceiver 100 in FIG. 1 is as follows.
The double sideband wave (DSB (Mf)) near the frequency Mf received by the first receiving antenna A _1R is transmitted only in the vicinity of the frequency Mf by the band filter 162, is synchronously demodulated by the first synchronous demodulator 17, and is band filtered. A sine wave having a frequency f is demodulated through the filter 163. The demodulated sine wave of frequency f is input to the phase comparator 11. Although details are not shown as the first synchronous demodulator 17, any known synchronous demodulator such as Costas Loop can be adopted.

Since it is configured as described above, in the first transceiver 100 of FIG. 1, the output of the voltage controlled oscillator 13 so that the phase of the output of the bandpass filter 163 matches the phase of the output of the fixed frequency oscillator 10. The phase of the sine wave having the frequency f is advanced. This phase difference is 4πLf / c (unit: radians) where L is the distance between the first transceiver 100 and the second transceiver 200 and c is the speed of light. Therefore, the phase comparator 18 can detect power corresponding to the phase difference 4πPLf / c (unit: radians) between the output of the fixed frequency oscillator 10 and the output of the voltage controlled oscillator 13. That is, the distance L between the first transceiver 100 and the second transceiver 200 can be accurately measured.
Further, since the double sideband waves (DSB (Nf) and DSB (Mf)) obtained by modulating the high frequency of the frequency Nf or the frequency Mf with the sine wave of the frequency f are used, the occupied band is extremely narrow.

[Modification]
FIG. 2 is a block diagram showing a specific configuration of the first transceiver 110 and the second transceiver 210 according to a modification of the present application, in which the configuration of the embodiment of FIG. 1 is partially changed.
First transceiver 110 of FIG. 2, the first transceiver 100 in FIG. 1, and the fixed frequency f _c to be input to the first RF generator 14, which differs from the output frequency f of the fixed frequency oscillator 10 to order, it is obtained by newly adding a fixed frequency oscillator 101 which outputs a sine wave of fixed frequency f _c. In the second transceiver, the output frequency of the fixed frequency oscillator 20 was f _c. In this way, the high frequency that becomes the carrier does not need to be generated by multiplication or division from the sine wave of the frequency f that becomes the modulation signal. Of course, the first transceiver 110 in FIG. 2 and the second transceiver 200 in FIG. 1 may be combined. In the present invention, the two carrier waves having different frequencies for exchange between the two transceivers are completely independent from the sine wave of the frequency f for detecting the phase according to the distance, and are not related at all. May be generated.

FIG. 3 is a block diagram showing specific configurations of two first transceivers 150-i and second transceivers 250-j according to another specific embodiment of the present application. FIG. 3 shows only one first transmitter / receiver 150-i and one second transmitter / receiver 250-j, but a plurality of these are prepared as described below. The frequency N _i f of the carrier wave generated by the first high frequency generator 14 of the first transceiver 150-i shown in FIG. 3 is different between the first transceivers. In addition, the frequency M _j f of the carrier wave generated by the second high frequency generator 24 of the second transceiver 250-j shown in FIG. 3 differs between the second transceivers.

The second transceiver 250-j has the same configuration _except that the carrier frequencies M _j f generated by the second high-frequency generator 24 are different from each other, and is substantially the same as the first embodiment shown in FIG. There is no difference in configuration from the second transceiver 200.
The first transmitter / receiver 150-i is obtained by adding the following configuration to the configuration of the first transmitter / receiver 100 of the first embodiment shown in FIG.
First, when the carrier wave N _i ′ f (different from its own carrier wave N _i f) transmitted by the other first transceiver 150-i ′ is detected in the high frequency received by the first receiving antenna A _R1. In addition, a detector and controller 15c for turning off the output of the mixer 15 is added.
Further, the signal received by the first receiving antenna A _R1 is transmitted through the band filter 162 and then converted to the intermediate frequency band by the following configuration. That is, the double sideband wave is converted into an intermediate frequency band by the mixer 155 by the output of the variable high frequency generator 145. For example, frequencies (I + 1) f and (I-1) f. These are obtained as a one-side band of frequency (I + 1) f and a one-side band of frequency (I-1) f by two band-pass filters 165U and 165L having a relatively narrow bandwidth. Thereafter, the adder 195 demodulates the signal as a double sideband wave by the synchronous demodulator 175. The synchronous demodulator 175 may have essentially the same configuration as the synchronous demodulator 17 of the first transceiver 100 of the first embodiment shown in FIG. 1, but the first transmission / reception of the first embodiment shown in FIG. The synchronous demodulator 17 of the receiver 100 demodulates the signal when the carrier wave has the frequency Mf, whereas the synchronous demodulator 175 of the first transceiver 150 of the present embodiment shown in FIG. The only difference is that the signal is demodulated.
Here, the outputs of the two bandpass filters 165U and 165L are also output to the detection and control unit 145c, and the high frequency (M _j −I) f output from the variable high frequency generator 145 is controlled by the detection and control unit 145c. Is controlled.
The detector and controller 145c, the variable high frequency generator 145, and the mixer 155 correspond to the frequency converter in the invention according to claim 2. The detector and controller 15c corresponds to the detector in the invention according to claim 2.

When the two transceivers 150 and 250 of FIG. 3 having such a configuration are arranged, for example, the following operation is performed.
First, in the first transmitter / receiver 150-i of FIG. 3, the detection and controller 15c transmits the carrier wave transmitted by the other first transmitter / receiver 150-i ′ to the high frequency received by the first receiving antenna A _R1. When N _i 'f (different from its own carrier N _i f) is detected, the output of the mixer 15 is turned off, and the carrier of frequency N _i f is modulated by a sine wave of frequency f for distance measurement. The two sidebands are not transmitted.
On the other hand, in the detector / controller 15c, the high frequency received by the first receiving antenna A _R1 is transmitted to the carrier wave N _i ′ f transmitted from the other first transceiver 150-i ′ (what is its own carrier wave N _i f? If no difference is detected, the output of the mixer 15 is turned on, and a double sideband wave modulated by a carrier wave having a frequency N _i f is transmitted by a sine wave having a frequency f for distance measurement.
The function of the detection and control unit 15c is a function of CSMA (Carrier Sense Multiple Access) used in the wireless LAN, and can be easily obtained and adjusted.

In each of the second transceivers 250-j in FIG. 3, almost the same as the second transceiver 200 in FIG. 1, the carrier wave having the frequency N _i f is synchronized from the double sideband wave modulated by the sine wave having the frequency f. A sine wave of frequency f is demodulated by demodulation. At this time, the sine wave of frequency f has a phase delay based on the distance between the first transceiver 150-i and the second transceiver 250-j in FIG. Thus, each second transceiver 250-j modulates and transmits (replies) a carrier wave having a different frequency M _j f.

First, in the first transmitter / receiver 150-i of FIG. 3, the detector / controller 15c transmits the high frequency received by the first receiving antenna A _R1 from the other first transmitter / receiver 150-i ′. The carrier wave N _i 'f (different from its own carrier wave N _i f) is not detected.
The output of the band filter 162 is mixed with the high frequency of the frequency (M _j −I) f output from the variable high frequency generator 145 and output to the band filters 165U and 165L having a relatively narrow bandwidth. In this way, the one sideband wave of frequency (I + 1) f and the one sideband wave of frequency (I-1) f are output from each of the band filters 165U and 165L. These are added by the adder 195 to be double sideband waves, synchronously demodulated by the synchronous demodulator 175, and transmitted through the bandpass filter 163. Then, the first transmitter / receiver 150-i and the second transmitter / receiver 250-j A sine wave having a frequency f having a phase lag based on a double distance between them is output.

Here, in FIG. 3, there is one first transceiver 150-i that is transmitting, but there are a plurality of second transceivers 250-j, so the first transceiver 150 that is transmitting. In -i, both sideband waves having different frequencies of a plurality of carrier waves are received. Therefore, the high frequency (M _j −I) f output from the variable high frequency generator 145 is switched by the number of the carrier frequencies M _j f of the plurality of second transceivers 250-j.
Specifically, for example, the frequency f of the sine wave for distance measurement is 5 MHz, and the carrier frequencies M ₁ f of the three second transceivers 250-1, -2, -3 are 300 MHz, M ₂ f Is 295 MHz, M ₃ f is 270 MHz, and the frequency If is 50 MHz as an intermediate frequency. Further, it is assumed that the center frequencies of the bandpass filters 165U and 165L are 55 MHz and 45 MHz, for example, the bandwidth is about 2 MHz.

Now, double sidebands of 305 MHz and 295 MHz from the second transceiver 250-1, double sidebands of 290 MHz and 280 MHz from the second transceiver 250-2, both sides of 275 MHz and 265 MHz from the second transceiver 250-3 Assuming that a band wave is transmitted and received by the first transceiver 150-i, the first transceiver 150-i uses the high-frequency frequency (M _j −I) f output from the variable high-frequency generator 145 as follows: Switching between 250 MHz, 235 MHz, and 220 MHz.
First, the high frequency (M _j −I) f output from the variable high frequency generator 145 is set to 250 MHz by the detection and controller 145c. At this time, both sideband waves of 305 MHz and 295 MHz from the second transceiver 250-1 are generated by the mixer 155 in the intermediate frequency band of 55 MHz and 45 MHz, and the bandpass filters 165U and 165L are respectively set on one side. It passes as a band wave. On the other hand, the double sidebands of 290 MHz and 280 MHz from the second transceiver 250-2, and the double sidebands of 275 MHz and 265 MHz from the second transceiver 250-3, both sidebands of 40 MHz and 30 MHz, Both sideband waves of 25 MHz and 15 MHz are obtained, and neither of the bandpass filters 165U and 165L can pass.

In the same manner, when the high frequency (M _j -I) f output from the variable high frequency generator 145 is 235 MHz, both sidebands of 290 MHz and 280 MHz from the second transceiver 250-2 are mixed. At 155, both sidebands of the intermediate frequency band of 55 MHz and 45 MHz are generated and can pass through the bandpass filters 165U and 165L as single sidebands, respectively. From the two sidebands of 305 MHz and 295 MHz from the second transceiver 250-1 and the two sidebands of 275 MHz and 265 MHz from the second transceiver 250-3, both sidebands of 70 MHz and 60 MHz, 40 MHz A 30 MHz double sideband is generated and cannot pass through either of the bandpass filters 165U and 165L.
In the same manner, when the high frequency (M _j -I) f output from the variable high frequency generator 145 is 220 MHz, the 275 MHz and 265 MHz double sidebands from the second transceiver 250-3 are mixed. At 155, both sidebands of the intermediate frequency band of 55 MHz and 45 MHz are generated and can pass through the bandpass filters 165U and 165L as single sidebands, respectively. From the two sidebands of 305 MHz and 295 MHz from the second transceiver 250-1 and the two sidebands of 290 MHz and 280 MHz from the second transceiver 250-2, both sidebands of 85 MHz and 75 MHz, 70 MHz A 60 MHz double sideband is generated and cannot pass through either of the bandpass filters 165U and 165L.

At this time, among the two sideband waves from the three second transmitters / receivers 250-1, 2 and 3, those having low power are processed as follows, assuming that there is no reply.
First, the high frequency (M _j −I) f output from the variable high frequency generator 145 is set to, for example, 250 MHz by the detection and controller 145c. At this time, if the power of the 305 MHz and 295 MHz double sideband waves from the second transceiver 250-1 is greater than or equal to a predetermined value, the double sideband waves of the intermediate frequency band of 55 MHz and 45 MHz generated by the mixer 155 Each passes through filters 165U and 165L as single sidebands. At this time, the phase difference is detected by the phase shifter 18 as in the first embodiment, and the distance is measured.
After a predetermined short time, the high frequency (M _j -I) f output from the variable high frequency generator 145 is set to, for example, 235 MHz by the detection and controller 145c. At this time, if the power of the 290 MHz and 280 MHz double sideband waves from the second transceiver 250-2 is equal to or greater than a predetermined value, the double sideband waves of the intermediate frequency band of 55 MHz and 45 MHz generated by the mixer 155 Each passes through filters 165U and 165L as single sidebands. At this time, the phase difference is detected by the phase shifter 18 as in the first embodiment, and the distance is measured.
After a predetermined short time, the high frequency (M _j −I) f output from the variable high frequency generator 145 is set to, for example, 220 MHz by the detection and controller 145c. At this time, if the power of the 275 MHz and 265 MHz double sideband waves from the third transceiver 250-3 is greater than or equal to a predetermined value, the double sidebands of the intermediate frequency band of 55 MHz and 45 MHz generated by the mixer 155 Each passes through filters 165U and 165L as single sidebands. At this time, the phase difference is detected by the phase shifter 18 as in the first embodiment, and the distance is measured.

At the time of switching, the detection and controller 145c determines the magnitude of the output of the bandpass filters 165U and 165L, and controls the necessity of distance measurement, the timing of switching, and the like. Further, when only one of the outputs of the bandpass filters 165U and 165L is equal to or greater than the threshold value, the distance measurement is not performed because it is caused by noise that is completely unrelated.
In addition, the first transceiver 150-i performs the high-frequency frequency (M _j -I) f output from the variable high-frequency generator 145 once every predetermined frequency for a predetermined short time, or for a predetermined time. After outputting the number of times and measuring the distance, the output of the mixer 15 is turned off, and the distance measurement is given to the other first transceiver 150-i ′. Each second transmitter / receiver 250-j replies without any difference after demodulating a sine wave of frequency f by synchronous demodulation, regardless of the signal from any first transmitter / receiver 150-i.

  In each of the embodiments described above, the synchronous demodulator is used. However, since it is a double sideband wave, a sine wave of frequency f may be demodulated by envelope detection using a diode, for example.

  The present invention includes a first transceiver having different transmission and reception frequencies in each of a plurality of transport devices in a factory or warehouse, such as a forklift, for example, for a plurality of workers walking in the factory or warehouse. By carrying 2 transceivers, it can be used as a warning device that informs the operator of the transport device of the presence of nearby workers.

The block diagram which shows the structure of the distance measuring apparatus by two transmitter / receivers based on one specific Example of this invention. The block diagram which shows the structure of the distance measuring apparatus by two transmitter / receivers based on a modification. The block diagram which extracted one each from the structure of several 1st transmitter / receiver and several 2nd transmitter / receiver based on the concrete other Example of this invention.

Explanation of symbols

100, 110, 150-i: first transceiver 200, 210, 250-j: second transceiver 10, 101, 20: fixed frequency oscillator 11, 18: phase comparator 12: low-pass filter 13: Voltage controlled oscillator 14: first high frequency generator 145: variable high frequency generator 15: mixer (first modulator)
15c: Detection and controller 155: Mixer 25: Mixer (second modulator)
161, 162, 163, 261, 262, 263: Bandpass filters 165U, 165L: Bandpass filters with narrow transmission bandwidths 17, 175: First synchronous demodulator 145c: Detection and controller 195: Adders 24, 245: Second high frequency generator 27: second synchronous demodulator

Claims (2)

In an apparatus comprising a first transceiver and a second transceiver, and measuring a distance between the first transceiver and the second transceiver,
The first transceiver is
A voltage controlled oscillator that outputs a sine wave;
A first high frequency generator for outputting a sine wave having a preset frequency;
A first modulator that modulates the output of the first high-frequency generator by the output of the voltage-controlled oscillator to generate a double sideband;
A first transmitting antenna for transmitting the output of the first modulator;
A first receiving antenna;
A first synchronous demodulator that demodulates a signal from both sideband waves received by the first receiving antenna by synchronous demodulation;
A fixed frequency oscillator that outputs a sine wave of a predetermined frequency,
The second transceiver is
A second receiving antenna;
A second synchronous demodulator that demodulates the signal from the received double sideband waves by synchronous demodulation;
A second high frequency generator for outputting a sine wave having a preset frequency;
A second modulator that modulates the output of the second high-frequency generator according to the output of the second synchronous demodulator to generate a double sideband;
A second transmitting antenna for transmitting the output of the second modulator;
The voltage controlled oscillator of the first transmitter / receiver is a phase-locked loop composed of the first transmitter / receiver and the second transmitter / receiver, and the output of the first synchronous demodulator is the frequency-fixed oscillator. Is controlled to match the output phase of
A distance measuring device for measuring the distance between the first transceiver and the second transceiver by comparing the phase of the output of the voltage controlled oscillator and the phase of the output of the fixed frequency oscillator. . Two or more each of the first transceiver and the second transceiver are prepared,
The high frequency output from the first high frequency generator of each of the first transceivers is different from each other,
The high frequency output from the second high frequency generator of each of the second transceivers is different from each other,
Before the first synchronous demodulator of each of the first transceivers,
A frequency converter composed of a variable high-frequency generator and a mixer;
Two bandpass filters to which the output of the frequency converter is input;
An adder for adding the outputs of the two bandpass filters;
The center frequency of the two bandpass filters is twice the frequency of the sine wave of the voltage controlled oscillator output,
And each said 1st transceiver has a detector which judges whether other said 1st transceiver is transmitting, respectively,
Each of the first transmitter / receivers does not transmit a double sideband when the detector determines that any one of the other first transmitter / receivers is transmitting. The distance measuring device according to claim 1, wherein when it is determined that none of the first transceivers is transmitting, both sideband waves are transmitted.

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