JP2009210372A - Distance measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To receive the high frequency signal transmitted from a single transmitter by a single receiver and precisely measure the relative distance between both. <P>SOLUTION: High frequency signals, light signals or ultrasonic signals modulated and/or spectrum-spread by a plurality of measuring signals, which have at least different frequencies, transmitted from a single transmitter are received by a single receiver to be modulated and/or reverse-spread. While the synchronism between a measurement signal having the lowest frequency and a synchronizing oscillator 33 is established and kept, the relative distance between both is precisely measured by detecting a part or whole of the phase and/or frequency of the plurality of the measurement signals with a phase-frequency detector 34 using a clock signal outputted from the synchronizing oscillator 33. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention provides an ultrasonic signal, a high-frequency signal, or an optical signal modulated and / or spread spectrum by at least a plurality of measurement signals having different frequencies from a single transmitter. It is for measuring the relative distance between them with high accuracy.

Conventionally, a system for measuring a distance by using a plurality of radio signals having different frequencies has been proposed. (For example, see Patent Documents 1 and 2)
U.S. Pat. No. 4,087,816 Japanese Patent Application Laid-Open No. 2001-051044

  FIG. 4 shows an example of a conventional “VLF band wireless position detection device” described in Patent Document 1. In FIG. 4, a synthesizer 23 that receives a VLF signal (a radio wave FSK between f0 and f0 + 50 Hz in a period of 20 msec) transmitted from the “US Navy VLF communication station”, amplified by an amplifier 11 and synchronized with a VCXO 22. And the mixer 16 are mixed to generate an intermediate frequency signal, amplified by the intermediate frequency amplifier 12 and limited by the limiter 18, and then the VCXO 22 signal is divided by P by the divider 24. The phase comparator 20 makes a comparison, and the result is input to the loop filter 21, and the oscillation frequency of the VCXO 22 is controlled by the output of the loop filter 21.

On the other hand, the output of the limiter 18 is compared with the output of the frequency divider 24 at the timing when the output of the frequency divider 24 is divided by 20 by the frequency divider 27 by the delay time measuring device 25. The distance from the detected delay time to the communication station can be measured.
In the conventional technique shown in FIG. 11, since it is difficult to accurately detect the timing at which the frequency of the VLF signal changes between (f0 and f0 + 50 Hz) on the receiving side, an approximate measurement is possible over a long distance. However, there is a problem that it is difficult to measure a relatively close distance within 300 m with high accuracy.

In the conventional “distance measuring device” described in Patent Document 2, the transmission device 1a attached to the distance measurement object divides the carrier wave signal from the oscillator 2, mixes it with the carrier wave signal by the mixer 4, and AM This transmission signal includes a carrier signal having a frequency f and two signals having a frequency f ± Δf.
The receiving apparatus 1b separates and detects three signals having frequencies of f−Δf, f, and f + Δf from the received signal by the bandpass filters 8, 9, and 10, and uses the signal having the frequency of f−Δf as a reference to the mixer 14 15, a beat signal of frequency f and a signal of frequency f + Δf is obtained.
The distance calculator 16 detects the phases of the two beat signals and calculates the distance to the distance measurement object based on the phase difference.
However, if the ratio between the frequency of the carrier signal and the frequency of the modulation signal increases, it becomes difficult to make the two orthogonal or synchronize the two, or the timing for detecting the phase of the two beat signals is arbitrary timing. In addition, there is a problem that high-precision distance measurement cannot be performed unless the two orthogonal points are managed strictly.

The present invention provides a single reception of an ultrasonic signal, a high-frequency signal or an optical signal which is modulated and / or spread spectrum by a plurality of measurement signals which are synchronized or orthogonal and which are at least different in frequency and transmitted from a single transmitter. In a system for measuring a relative distance by receiving by a machine, the synchronization oscillator provided in the receiver and the measurement signal having the lowest frequency among the plurality of measurement signals are established and held, and the synchronous oscillator By detecting the phase and / or frequency of some or all of the plurality of measurement signals using the clock signal output from the signal, a distance measuring device that can measure the relative distance between the two with high accuracy is realized at low cost. Is for.

  The distance measuring apparatus according to the present invention is an ultrasonic signal, a high-frequency signal, or an optical signal that is modulated and / or spectrum-spread by a plurality of measurement signals that are synchronized or orthogonally transmitted from a single transmitter and have at least different frequencies. A receiver for receiving a signal, a demodulator for demodulating and / or despreading the plurality of measurement signals from an output signal of the receiver, and a plurality of the demodulated and / or despread measurement signals A synchronous oscillator for establishing and maintaining synchronization with a measurement signal having the lowest frequency, and a phase and / or a frequency of a part or all of the plurality of measurement signals using a clock signal output from the synchronous oscillator It is composed of a phase / frequency detector.

As the demodulator, a synchronous detector or a delay detector is used, and the synchronous oscillator includes at least a digital phase comparator, a charge pump circuit, an integration circuit or a phase lag filter, and the integration circuit or the phase lag filter. An analog-to-digital converter for converting the output of the signal into a digital signal, a numerically controlled oscillator whose phase and / or frequency is controlled by the data output of the analog-to-digital converter, and synchronization establishment / holding means ing.
The phase / frequency detector separately provides the plurality of measurement signals using a clock signal output from the synchronous oscillator in order to detect a part or all of the frequency and / or phase of the plurality of measurement signals. The analog signal is converted into a digital signal by an analog-digital converter, and 0, 1, 0, -1 is used as the Sin lookup table, and 1, 0, -1, 0 is used as the Cosin lookup table. Performs product-sum operations with digital signals.

The measurement signal having the lowest frequency serving as a reference is synchronized with the synchronization oscillator by the synchronization establishment / holding means of the synchronization oscillator, the synchronization state is maintained, and at least some or all frequencies of measurement signals having different frequencies And / or a phase is detected and the relative distance between the said transmitter and a receiver is measured with high precision from the said detection result.

In the distance measuring device of the present invention, an ultrasonic signal, a high-frequency signal, or an optical signal that is modulated and / or spectrum-spread by a plurality of measurement signals that are synchronized or orthogonally transmitted from a single transmitter and are at least different in frequency is used. By receiving a single receiver and transmitting in one direction from the transmitter to the receiver, the relative distance between the two can be measured with high accuracy and can be realized at low cost. is there.

  The distance measuring apparatus according to the present invention comprises a demodulator 32 for demodulating and / or despreading the output of the limiter 18 of the receiver, as shown in FIG. 1 and claim 1 of the first embodiment of the present invention. The synchronization oscillator 33 and the phase / frequency detector 34, and the synchronization signal 33 is synchronized with the measurement signal having the lowest frequency among the plurality of measurement signals demodulated and / or despread by the demodulator 32. The phase / frequency detector 34 measures the phase and / or frequency of the measurement signal using the clock signal output from the synchronous oscillator 33.

As shown in FIG. 2 and claim 2 or claim 3, the synchronous oscillator 33 includes a phase comparator 103, a phase lag filter 104, a numerically controlled oscillator 105, a division period 106, and synchronization. The holding means 102 is configured.
As the demodulator 32, a synchronous detector or a delay detector is used, and a 0.5 MHz signal having a low internal frequency of the measurement signal demodulated and / or despread by the demodulator 32 is used as the synchronization establishment signal. A 2 MHz signal having a high frequency input to the oscillator 33 is connected to the phase / frequency detector 34 via the band pass filter 101 as a distance measurement signal.

(Embodiment 1)
FIG. 1 is a configuration diagram of a distance measuring apparatus according to a first embodiment of the present invention. In FIG. 1, 10 is an antenna, 11 is a high frequency amplifier, 16 is a mixer, 17 is an intermediate frequency amplifier, 18 is a limiter, 23 is a synthesizer, 31 is a reference oscillator, 32 is a demodulator, 33 is a synchronous oscillator, 34 is a phase oscillator A frequency detector 35 is a connection terminal.
The high frequency signal received by the antenna 10 is amplified by the high frequency amplifier 11, converted into an intermediate frequency signal by the output signal of the synthesizer 23 synchronized with the reference oscillator 31 and the mixer 16, amplified by the intermediate frequency amplifier 17, and then by the limiter 18. The amplitude is suppressed and input to the demodulator 32.

Either a synchronous detector or a delay detector is used as the demodulator 32, and a plurality of measurement signals are demodulated and / or despread from the received high-frequency signal, and either the synchronous oscillator 33 or the phase / frequency detector 34 is used. Is input.
First, when a synchronization establishment signal (0.5 MHz) having a low internal frequency among a plurality of measurement signals is demodulated and / or despread, it is input to the synchronization oscillator 33, and the synchronization oscillator 33 establishes synchronization with the synchronization establishment signal and synchronizes. Hold.
Next, when a distance measurement signal (2 MHz) having a high internal frequency among a plurality of measurement signals is demodulated and / or despread, the signal is input to the phase / frequency detector 34 and output from the synchronous oscillator 33 (8 MHz). As a reference, the phase and / or frequency is detected, and the data output of the phase / frequency detector 34 is output from the connection terminal 35 to the outside.

Data output from the connection terminal 35 is transferred to an external PDA or the like via an interface such as RS232C, the relative distance is calculated by the PDA, and the calculation result is displayed.
When the synchronization establishment signal is 0.5 MHz and the distance measurement signal is 2 MHz, the difference in frequency is 1.5 MHz. Therefore, the phase difference is 360 ° when the distance is 200 m. Relative distance can be measured with high accuracy.
Since the measurement accuracy of the phase difference can be easily realized about ± 0.5 °, the measurement error of the relative distance is about ± 30 cm or less.

(Embodiment 2)
FIG. 2 is a block diagram of a distance measuring apparatus according to the second embodiment of the present invention. In FIG. 2, 18 is a limiter, 32 is a demodulator, 33 is a synchronous oscillator, 34 is a phase / frequency detector, 35 is a connection terminal, 101 is a band-pass filter, 102 is synchronization holding means, 103 is a phase comparator, 104 Is an integrating circuit or phase lag filter, 105 is a numerically controlled oscillator, 106 is a fractional period, and 111 to 114 are connection terminals.
As the demodulator 32, either a synchronous detector or a delay detector is used. The synchronous detector has a better signal-to-noise ratio of the demodulated signal, but the circuit is more complicated. It has been.
Of the plurality of measurement signals demodulated and / or despread by the demodulator 32, a synchronization establishment signal (0.5 MHz) having a low frequency is input to the synchronization holding means 102 via the connection terminal 111 and held in synchronization. The output of the means 102 is input to one input terminal of the phase comparator 103.
On the other hand, the output of the numerically controlled oscillator 105 is frequency-divided by 16 by the dividing period 106 and input to the other input terminal of the phase comparator 103 via the synchronization holding means 102.

The output signal of the phase comparator 103 is connected to an integrating circuit or a phase lag filter 104 via a charge pump circuit and integrated into a DC voltage, converted into a digital signal by an analog / digital converter, and input to the numerically controlled oscillator 105. The phase and / or frequency of the numerically controlled oscillator 105 is controlled.
First, there is a frequency difference and / or phase difference between the signal input to the phase comparator 103 and the signal output of the division period 106, and a pulse signal corresponding to the frequency difference and / or phase difference is transferred to the charge. It is output from the pump circuit, integrated by the integrating circuit or the phase lag filter 104, and converted into a DC voltage.

On the other hand, when the frequency when the clock signal output from the numerically controlled oscillator 105 is divided by 16 by the dividing period 106 is higher than the frequency of the synchronization establishment signal, the DC voltage changes in a direction to decrease the frequency of the numerically controlled oscillator 105. On the contrary, when the frequency is low, it changes in the opposite direction.
When synchronization is established, a synchronization establishment signal is output from the connection terminal 113, so that synchronization is maintained by inputting a synchronization hold signal to the connection terminal 112.
When the distance measurement signal having a frequency of 2 MHz is demodulated and / or despread by the demodulator 32 in a state where synchronization is maintained, the signal is input to the phase / frequency detector 34 via the band-pass filter 101, and the numerical control is performed. The phase and / or frequency of the distance measurement signal is detected using the clock signal output from the oscillator 105 and output to the outside as a data signal via the connection terminal 35.

The phase / frequency detector 34 includes, for example, an analog / digital converter and a product-sum calculator, and an 8-MHz clock signal having a frequency four times as high as the 2-MHz distance measurement signal output from the synchronous oscillator 33. Is converted into a digital signal by the analog / digital converter, and 0, 1, 0, -1 is used as the Sin lookup table, and 1, 0, -1, 0 is used as the Cosin lookup table. The frequency and / or phase of the distance measurement signal is detected by performing a product-sum operation with the digital signal converted by the analog / digital converter.
The analog-to-digital converter usually has a scale of 8 bits to 10 bits.

Assuming that two measurement signals transmitted from the transmitter (not shown) having different frequencies and orthogonal to each other are ASin (2πf1t) and ASin (2πf2t), the measurement is demodulated and / or despread by the demodulator 32. The signal is represented by BSin {2πf1 (t + t0) + (2πD / λ1) + Φ}, BSin {2πf2 (t + t0) + (2πD / λ2) + Φ}.
Here, t0 = the time difference between the time transmitted from the transmitter and the time demodulated and / or despread by the demodulator 32.
When the two measurement signals are compared, when the time difference t0 does not occur, that is, when the relative distance is D = 0, the time at which the two measurement signals are orthogonal to each other is set so that 2πf1t = 2πf2t = 0 °. When the phase difference is measured, the phase difference ΔΦ = 0 can be measured.

However, since the time difference t0 occurs when the relative distance becomes D> 0, the phase difference ΔΦ = (2πD / λ1) −2πD / λ2 if the control can be performed so that 2πf1 (t + t0) = 2πf2 (t + t0) = 0 °. ) Can be detected, but such control is very difficult.
Therefore, when synchronization establishment / holding means is provided in the synchronous oscillator 33 to synchronize with the measurement signal with the lower frequency of the two measurement signals, {2πf1 (t + t0) between the measurement signal with the lower frequency and the synchronous oscillator 33. ) + (2πD / λ1) + Φ} = 0, the synchronization can be established. Therefore, when the phase of the distance measurement signal is measured with the clock signal output from the synchronous oscillator 33, the phase difference ΔΦ = (2πD / λ1) − (2πD / λ2) can be detected.

Phase difference ΔΦ = (2πD / λ1) − (2πD / λ2) = 2πD {(1 / λ1) − (1 / λ2)} = (D / C) {2π (f1−f2)} The relative distance D (m) to the receiver can be obtained from D = (C × ΔΦ) / {2π (f1−f2)}. Here, C is the speed of light.
For example, assuming that f1-f2 = 1.5 MHz, the phase difference is ΔΦ = 360 ° when the distance between the two is 200 m. Therefore, when the measurement accuracy of the phase difference is ± 0.5 °, the distance is measured. The accuracy is ± 30 cm, and high-precision distance measurement is possible.

Similarly, as an example of transmitting a plurality of measurement signals having different frequencies in parallel, the following three transmission signals generated by amplitude-modulating a carrier signal (frequency f0) from the transmitter with a modulation signal (frequency fm): , Asin (2π (f0−fm) t−φ), Asin (2πf0t), and Asin (2π (f0 + fm) t + φ) are transmitted. Here, f0 = the frequency of the carrier signal, fm = the frequency of the modulation signal, and φ = the phase difference between the carrier signal and the modulation signal.
Therefore, considering two beat signals with the other second and third signals based on a predetermined first signal among the transmission signals, Bsin ((2πfm) t− φ), Bsin (2 ((2πfm) t−φ)) is obtained as a measurement signal having a high frequency.

Since the low frequency measurement signal and the high frequency measurement signal are orthogonal to each other, Bsin ((2πfm) t−φ) = 0 and Bsin (2 ((2πfm) t−φ)) = 0 at the orthogonal point. Therefore, the relationship is ((2πfm) t−φ) = (2 ((2πfm) t−φ)) = 2 (N−1) π. Here, N is a positive integer.
When the receiver receives the measurement signal transmitted from the transmitter at a point D (m) away, the low frequency measurement signal is Bsin ((2πfm) t−φ) + (2πDfm / C)), The high frequency measurement signal is Bsin (2 ((2πfm) t−φ) +2 (2πDfm / C)). Here, C = speed of light.

When the synchronous oscillator 33 and the low frequency measurement signal are synchronized, there is no phase difference between the clock signal of the synchronous oscillator 33 and the low frequency measurement signal, so ((2πfm) t−φ) + ( Since 2πDfm / C)) = 0 °, ((2πfm) t−φ) = − (2πDfm / C).
On the other hand, since the low-frequency measurement signal and the high-frequency measurement signal are orthogonal, ((2πfm) t−φ) = 2 ((2πfm) t−φ) = − (2πDfm / C). .

When the phase of the high frequency measurement signal is measured using the clock signal output from the synchronous oscillator 33 while the synchronization of the synchronous oscillator 33 is maintained, the phase ΔΦ of the high frequency measurement signal is ΔΦ = − (2πDfm / C) +2 (2πDfm / C)) = (2πDfm / C), the difference φ between the phase of the carrier signal and the phase of the modulation signal is eliminated, and therefore the measurement error of the relative distance is reduced. Can be reduced.
This means that the carrier signal (frequency f0) and the modulation signal (frequency fm) do not need to be orthogonal or synchronized.

The synchronous oscillator 33 detects one or both of the zero cross point and the orthogonal point of the measurement signal with the lowest frequency among the plurality of measurement signals demodulated and / or despread, and based on the detection result. A similar effect can be obtained by generating a clock signal by controlling the phase and / or frequency of the numerically controlled oscillator.
In addition, the synchronous oscillator 33 includes a DSP, and a clock signal synchronized with one or both of the zero cross point and the orthogonal point of the measurement signal having the lowest frequency among the plurality of demodulated and / or despread measurement signals. The same effect can be obtained by generating.

FIG. 3 is a timing chart of the distance measuring device of the present invention. In FIG. 3, 201 and 202 are orthogonal points of two measurement signals, 203a to 203d are time axes, 204 is a delay time of a low frequency measurement signal, 205 is a synchronization establishment point, 206 is a low frequency measurement signal and a high frequency. , 211a and 211b are low frequency clock signals, 211c and 211d are low frequency clock signals, 212a and 212b are high frequency measurement signals, and 212c and 212d are high frequency clock signals.
On the transmitter side (not shown), it is assumed that the low-frequency measurement signal 211a and the high-frequency measurement signal 212a are orthogonal to each other at orthogonal points 201 and 202.

On the receiving side (not shown), it is assumed that the low-frequency measurement signal 211b is demodulated and / or despread after a delay time 204 from the orthogonal point 201.
The low-frequency clock signal 211c is out of synchronization with the low-frequency measurement signal 211b at the orthogonal point 201, and synchronization establishment control is started after the delay time 204, and synchronization is established and synchronization is maintained at the synchronization establishment time point 205. It is assumed that the low-frequency clock signal 212c is continuously output.

Since the high frequency clock signals 211d and 212d are fully synchronized, a high frequency measurement that is demodulated and / or despread using the high frequency clock signal 212d that establishes synchronization and maintains synchronization. When the phase of the signal 212b is detected using a phase / frequency detector (not shown), the level of the low frequency measurement signal 211b and the high frequency measurement signal 212b demodulated and / or despread is detected. The phase difference 206 is obtained.
At the synchronization establishment point 205, the low frequency clock signal 212c and the low frequency measurement signal 211b can establish synchronization with high accuracy within ± 0.1 °, so that the high frequency synchronized with this can be achieved. By measuring the phase of the high-frequency measurement signal 212b demodulated and / or despread using the clock signal 211d, the phase difference 206 can be detected with high accuracy.

  In the above description, the product and sum calculator using hardware is used to detect the phase and / or frequency. However, FFT calculation is performed using a DSP or microcomputer, or other existing techniques are employed. Can also be realized. However, since FFT processing by software takes a long processing time and real-time processing becomes difficult, processing by hardware is preferable from the viewpoint of processing time, current consumption, and cost.

  Further, an ultrasonic signal is transmitted from the transmitter using an ultrasonic transducer or an ultrasonic transmitter, and an ultrasonic signal is received using an ultrasonic transducer or an ultrasonic receiver in the receiver, Alternatively, a similar effect can be obtained by transmitting an optical signal using a light emitting diode or laser diode in the transmitter and receiving an optical signal using a photodiode in the receiver.

In the transmitter, a modulated signal or baseband signal synchronized or orthogonal to a reference oscillator is generated, and a carrier wave signal or subcarrier wave of an ultrasonic signal, a high frequency signal, or an optical signal is modulated and transmitted. An effect is obtained.
Further, when a plurality of digital signals that are synchronized or orthogonal from the transmitter and at least have different chip rates and / or are modulated or spread by a spread spectrum code, a plurality of frequencies are different in the receiver. It can be converted into a measurement signal.
The same effect can be obtained by transmitting an ultra wide band (UWB) spread spectrum code in the transmitter.

Since the present invention is configured as described above, it becomes possible to measure the relative distance between a single transmitter or a single receiver with high accuracy, and to measure the direction or the direction in which it is heading. In combination with this, the position can be determined with high accuracy.
In addition, when the transmitter and / or the receiver is mounted on a mobile body or carried by a pedestrian, the positional relationship between the transmitter and the receiver can be immediately measured anytime and anywhere, so that it can be applied to a ubiquitous mobile network.
Relative distance measurement and position location can be performed with high accuracy, so when a pedestrian crosses a pedestrian crossing such as an intersection, it is guided not to deviate from the pedestrian crossing, or the pedestrian approaches the driver. It can be used for systems such as warning.
In addition, since the direction and distance can be measured between a single base station and a mobile terminal in the mobile radio system, a highly accurate car navigation system or pedestrian navigation system can be realized.

In addition, since the active tag can be used as a transmitter and multiple receivers are connected via a network, the exact location of the active tag can be detected. It can be used for physical distribution management for efficient collection or searching for lost children.
In addition, the active tag can be carried by domestic animals or wild animals to detect the exact position, and can be used for biotelemetry.

In addition, by mounting the transceiver on a running vehicle, the relative position between them can be measured with high accuracy, so that it can be used for cooperative driving on a highway.
In addition, the distance and direction between multiple navigating vessels, multiple flying aircraft, or multiple running vehicles can be accurately measured, preventing collisions and maintaining the distance between each other. Can be used in the system.

In addition, since the relative positional relationship with the moving body can be accurately measured by one-to-one communication between the moving body and the pilot, a remote control of the moving body can be realized with an inexpensive device.
Further, the distance measurement technique of the present invention is a basic technique and can be expected to be applied in other fields.

Configuration diagram of distance measuring apparatus according to Embodiment 1 Configuration diagram of distance measuring apparatus according to Embodiment 2 Timing chart of distance measuring apparatus of the present invention Configuration diagram showing a conventional example

Explanation of symbols

10 antenna 11 high frequency amplifier 16 mixer 17 intermediate frequency amplifier 23 synthesizer 31 reference oscillator 32 demodulator 33 synchronous oscillator 34 phase / frequency detector 35 connection terminal

101 Band-pass filter 102 Synchronization holding means 103 Phase comparator 104 Phase lag filter 105 Numerically controlled oscillator 106 Dividers 111 to 114 Connection terminal

201, 202 Orthogonal points 203a to 203d of measurement signal Time axis 204 Delay time 205 Synchronization establishment time point 206 Phase difference 211a, 211b Low frequency measurement signal 211c, 211d Low frequency clock signal 212a, 212b High frequency measurement signal 212c, 212d High frequency clock signal

Claims (5)

In a system that measures distance using ultrasonic signals, high-frequency signals, or optical signals,
A receiver for receiving an ultrasonic signal or a high-frequency signal or an optical signal modulated and / or spread spectrum by a plurality of measurement signals which are synchronized or orthogonal and at least different in frequency; and a plurality of the output signals from the receiver For establishing and maintaining synchronization between a demodulator for demodulating and / or despreading a plurality of measurement signals and a measurement signal having the lowest frequency among the demodulated and / or despread measurement signals A synchronous oscillator, and a phase / frequency detector for detecting a phase and / or a frequency of a part or all of the plurality of measurement signals using a clock signal output from the synchronous oscillator, / Or distance measuring device characterized by measuring relative distance from frequency detection result
The synchronous oscillator includes at least a phase comparator, a charge pump circuit, an integration circuit or a phase lag filter, and an analog / digital converter for converting an output signal from the integration circuit or the phase lag filter into a digital signal. And a numerical control oscillator, a frequency divider for dividing the output frequency of the numerical control oscillator, and synchronization establishment / holding means, and the numerical control using the data output of the analog / digital converter 2. The distance measuring device according to claim 1, wherein the clock signal is generated by controlling the phase and / or frequency of the oscillator.
The synchronous oscillator detects one or both of a zero cross point and an orthogonal point of the measurement signal having the lowest frequency among the plurality of demodulated and / or despread measurement signals, and the numerical value is determined based on the detection result. The distance measuring device according to claim 1, wherein the clock signal is generated by controlling the phase and / or frequency of the controlled oscillator.
The synchronous oscillator includes at least a DSP and generates a clock signal synchronized with one or both of a zero cross point and an orthogonal point of the measurement signal having the lowest frequency among the demodulated and / or despread measurement signals. The distance measuring device according to claim 3, wherein
  In the phase / frequency detector, in order to detect phases and / or frequencies of the plurality of measurement signals, the plurality of measurement signals are digitally converted by an analog / digital converter using a clock signal output from the synchronous oscillator. The signal is converted into a signal, the unit of 0, 1, 0, -1 as the lookup table of Sin, the unit of 1, 0, -1, 0 as the lookup table of Cosin, and the product-sum operation with the digital signal The distance measuring device according to claim 1, wherein

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