JP3785178B2 - Distance measuring device - Google Patents

Description

  The present invention relates to a distance measuring device for measuring a distance to a moving body such as an artificial satellite flying in an orbit.

  One method for measuring the distance from an earth station to an artificial satellite is to use a single pulse signal.

In this method, a single pulse signal is transmitted from an earth station to an artificial satellite, and a time (hereinafter referred to as a round trip time) ΔT from when the pulse signal is turned back by the artificial satellite to reach the earth station is measured. The distance from the earth station to the satellite,
1/2 × ΔT × c where c is the speed of light (1)
Is calculated by the following formula.

  However, in the above-described method, distance measurement can be performed only once by transmission / reception of a single pulse signal, and a distance measurement signal in which pulses continuously occur in a predetermined cycle is used for continuous distance measurement. There is a need. That is, as shown in FIG. 6, a distance measurement signal (transmission distance measurement signal) that generates a pulse at an interval of time t is transmitted, and after the pulse is generated in the transmission distance measurement signal, the measurement signal returned and received by the artificial satellite is received. It is necessary to measure the time until a pulse is generated in the distance signal (received distance measurement signal) as the round trip time ΔT.

  At this time, there is no problem if the time required for the distance measurement signal to reciprocate between the earth station and the artificial satellite is smaller than the pulse generation interval t in the transmission distance measurement signal as shown in FIG. As shown in FIG. 7, when the pulse generation interval t in the transmission ranging signal is larger than the correspondence between each pulse generated in the transmission ranging signal and each pulse generated in the reception ranging signal, the round trip time ΔT is set to It becomes difficult to measure accurately.

  This problem can be avoided by setting it sufficiently large so that the pulse generation interval in the distance measurement signal is always longer than the round trip time ΔT. However, if the pulse generation interval t in the distance measurement signal is increased, a new problem such as an increase in the synchronization acquisition time of the receiver that receives the distance measurement signal in the artificial satellite or the earth station occurs. Is limited, and the pulse generation interval in the distance measurement signal may not be set longer than the round trip time ΔT.

  In such a case, conventionally, a predicted value of the round-trip time at each time is obtained in units of multiples of the pulse generation interval in the transmission ranging signal based on the orbit information of the artificial satellite. That is, the predicted value obtained here is represented by A × N (N is an integer), where A is the pulse generation interval in the transmission ranging signal.

Then, the time δt from when the pulse is generated in the transmission ranging signal until the pulse is generated in the reception ranging signal is measured, and the true round trip time ΔT is
ΔT = A × N + δt
It is calculated by the following formula.

  In this way, the process of calculating the true value by calculating A × N is called ambiguity removal.

  However, with this method, it is necessary to calculate in advance the predicted values of distances at all distance measurement data acquisition times, and there is a problem that ambiguity removal is required for all distance measurement data.

  On the other hand, another method for measuring the distance from the earth station to the artificial satellite uses a pseudo random noise (PN) signal as a distance measurement signal.

  As shown in FIG. 8, the PN signal is a PN code that is a repetition of a bit string of a predetermined pattern in which bits of “0” or “1” are arranged, a PN clock synchronized with each bit forming the PN code, and a PN code. It consists of a PN epoch synchronized with the first bit of one sequence.

Thus, when this PN signal is used as a ranging signal, the first counter for counting how many bits the transmission PN code is from the beginning of one sequence and how many bits the reception PN code is from the beginning of one sequence Each of the second counters for counting is prepared. When the count value of the first counter is N1, the count value of the second counter is N2, and the cycle of the transmission PN clock is δT, the round-trip time ΔT of the ranging signal is
ΔT = (N1-N2) × δT (2)
It is calculated by the following formula.

  The distance from the earth station to the artificial satellite can be obtained by substituting ΔT obtained by this equation into the equation (1). The distance calculated here represents the distance between the earth station and the artificial satellite at the time indicated by [T0−ΔT / 2] when the distance measurement start time is T0.

  By the way, when the distance to the artificial satellite is almost constant as shown in FIG. 9, the frequency of the transmission ranging signal and the frequency of the receiving ranging signal are almost the same, and there is no problem. However, in reality, the distance to the artificial satellite varies, and the frequency of the ranging signal received by the artificial satellite differs from the frequency of the ranging signal transmitted from the earth station due to the Doppler effect caused by this. Further, as shown in FIG. 10, the frequency of the reception ranging signal at the ground station is also different from the frequency of the transmission ranging signal.

  Therefore, in many cases, Doppler compensation is performed to control the transmission frequency on the ground so as to cancel the shift of the satellite reception frequency caused by the Doppler effect caused by the movement of the artificial satellite.

  If this Doppler compensation is performed, the cycle δT of the transmission PN clock in the transmission ranging signal will fluctuate, so that the round trip time ΔT cannot be obtained by the above equation (2), and the distance cannot be measured. End up. That is, the method using the PN signal has a problem that it cannot cope with the case where Doppler compensation is performed.

  As described above, in the conventional distance measuring device, when the distance measurement is performed using the PN signal as the distance measurement signal, the round trip time of the distance measurement signal is obtained by counting the PN clock in the transmission distance measurement signal. If the frequency of the PN clock changes, the round trip time of the distance measurement signal cannot be obtained accurately, and the distance measurement cannot be performed accurately.

  The present invention has been made in consideration of such circumstances, and the object of the present invention is to perform the distance measurement using the PN signal as a distance measurement signal regardless of the frequency of the transmission distance measurement signal. It is an object of the present invention to provide a distance measuring apparatus capable of performing accurate distance measurement and capable of performing accurate distance measurement even when Doppler compensation is performed.

  In order to achieve the above object, the present invention provides a pseudo-random noise epoch indicating a predetermined pseudo-random noise code, a pseudo-random noise clock synchronized with the pseudo-random noise code, and a predetermined bit for each sequence of the pseudo-random noise code. Transmitting a ranging signal each including, for example, a ranging signal transmitting means including a ranging signal generating unit, a transmitting unit, and an antenna; and receiving a ranging signal returned from the moving body, for example, from an antenna and a receiving unit Ranging signal receiving means, and a transmission code such as a transmission PN code position counter for detecting the number of bits from a predetermined bit indicated by the pseudo random noise epoch, the pseudo random noise code transmitted by the transmission means A position detecting means and a pseudo-random noise code received by the receiving means; For example, a received code position detecting means such as a received PN code position counter for detecting the number of bits from a predetermined bit indicated by the pseudo random noise epoch, for example, a reference clock generating section for generating a reference clock having a fixed period, etc. The reference clock generation means and the time from the predetermined distance measurement start time until the reception code position detection means obtains the same detection result as the detection result of the transmission code position detection means at this time is used for the reference clock. For example, the time measured by the time counting means, such as a round-trip time counter and a round-trip time counting control means, and the time measured by the time measuring means as the time required for the distance measurement signal to reciprocate between the moving body Distance calculating means for calculating the distance to the moving body.

  By taking such means, the time until a bit in the PN code is returned via the mobile unit is counted as the round-trip time of the ranging signal, and the distance of the mobile unit is calculated from this time. However, when measuring the round trip time of the distance measurement signal, it is realized by counting the number of periods of the reference clock whose frequency is constant regardless of the frequency of the distance measurement signal. Even if the frequency changes, the round trip time of the distance measurement signal is not affected.

  The present invention provides a ranging signal including a predetermined pseudo-random noise code, a pseudo-random noise clock synchronized with the pseudo-random noise code, and a pseudo-random noise epoch indicating a predetermined bit for each sequence of the pseudo-random noise code. Ranging signal transmitting means for transmitting, for example, a ranging signal generating section, transmitting section and antenna; Ranging signal receiving means for receiving, for example, a ranging signal returned from the mobile body; A transmission code position detection means such as a transmission PN code position counter for detecting the number of bits from a predetermined bit indicated by the pseudo random noise epoch, and the reception of the pseudo random noise code transmitted by the transmission means; The pseudo-random noise code received by the means is pseudo-random noise A received code position detecting means such as a received PN code position counter for detecting the number of bits from a predetermined bit indicated by the pock, and a reference clock generating means such as a reference clock generating section for generating a reference clock having a fixed period. And using the reference clock to measure the time from the predetermined distance measurement start time until the reception code position detection means obtains the same detection result as the detection result of the transmission code position detection means at this time, for example, Distance to the moving body as time required for the distance measurement signal to reciprocate between the time measuring means composed of a reciprocating time counter and a reciprocating time measuring control means and the time measured by the time measuring means. The distance calculation means for calculating the transmission distance measurement signal when the distance measurement is performed using the PN signal as the distance measurement signal. Can make accurate distance measurements regardless of the frequency, the distance measuring apparatus capable of performing an accurate distance measurement even when implementation of the Doppler compensation.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a functional block diagram showing a main configuration of an earth station device configured by applying the distance measuring device according to the present embodiment.

  As shown in this figure, the earth station device of the present embodiment has a ranging signal generator 1, a transmitter 2, an antenna 3, a receiver 4, a time difference timer 5, a calculator 6, and a trajectory predictor 7. Yes.

  The ranging signal generator 1 generates a ranging signal in which a single pulse is generated at a predetermined cycle (interval of a predetermined time A). The distance measurement signal generated by the distance signal generator 1 is supplied to the antenna 3 via the transmitter 2 and is transmitted toward the artificial satellite S as a transmission distance signal.

  The return ranging signal returned by the artificial satellite S is given to the receiving unit 4 via the antenna 3 and is received here.

  The time difference timer 5 measures the time difference δt from when a pulse is generated in the distance measurement signal generated by the distance signal generator 1 to when the pulse is generated in the distance signal received by the receiver 4, 6 is notified.

  The calculation unit 6 includes, for example, a microprocessor as a main control circuit, and includes a time difference comparison unit 6a, a predicted value correction unit 6b, and a distance calculation unit 6c, each realized by software processing, for example. Among these, the time difference comparison means 6a performs a comparison process between the difference between the time difference currently output by the time difference timer 5 and the time difference output at the previous timing and a predetermined specified value. The predicted value correcting means 6b corrects the predicted value used by the distance calculating means 6c for calculating the distance, if necessary, based on the comparison result by the time difference comparing means 6a. The distance calculation means 6c performs a process for calculating the distance to the artificial satellite S based on the time difference δt timed by the time difference time measuring unit 5 and the predicted value obtained in advance.

  The orbit prediction unit 7 obtains an initial predicted value when the calculation unit 6 starts the distance measurement based on the orbit information of the artificial satellite S, and gives it to the calculation unit 6.

  Next, the operation of measuring the distance to the artificial satellite S in the earth station apparatus configured as described above will be described according to the processing procedure of the calculation unit 6.

  First, when the calculation unit 6 is activated and starts a distance measurement operation, the calculation unit 6 causes the trajectory prediction unit 7 to predict the current distance. The orbit prediction unit 7 predicts the current distance to the artificial satellite S based on the orbit information of the artificial satellite S, and outputs the value. Here, the trajectory prediction unit 7 predicts the distance with an accuracy that is an integral multiple of the pulse generation interval A in the distance measurement signal generated by the distance signal generation unit 1. That is, the value output by the trajectory prediction unit 7 takes a value of A × N (N is an integer).

  And the calculating part 6 takes in the value which the orbit prediction part 7 outputs as mentioned above as a predicted value (step ST1 in FIG. 2). The calculating unit 6 takes in the time difference δt output by the time difference measuring unit 5 at that time (step ST2).

Next, the calculation unit 6 calculates the distance to the artificial satellite S by the distance calculation means 6c.
1/2 × {(A × N) + δt} × c
It is calculated by the following formula.

  Here, when calculating the first distance after the start of distance measurement, since (A × N) is a value predicted by the trajectory prediction unit 7, a distance calculation process by a method similar to the conventional method for removing ambiguity is performed. Will be performed.

  Now, when a predetermined time (for example, 1 second) has elapsed since the time difference δt output by the time difference time measuring unit 5 was taken in last time, the calculation unit 6 uses the value of the time difference δt used for calculating the distance in step ST3. At the same time as δt ′ (step ST4), the time difference δt currently output by the time difference measuring unit 5 is newly taken in (step ST5). Thus, δt indicates the time difference at the latest distance measurement timing, and δt ′ indicates the time difference at the previous distance measurement timing.

  Then, the arithmetic unit 6 uses the time difference comparison means 6a to determine whether [δt−δt ′] is larger than a predetermined reference value δtx and whether [δt′−δt] is larger than a predetermined reference value δtx. (Step ST6 and step ST7). That is, in step ST6 and step ST7, the calculation unit 6 compares the value of the time difference δt output from the time difference time measuring unit 5 with the value at the previous distance measurement timing, and the difference between the two becomes a predetermined value abnormality. Judgment is made whether or not. More specifically, the value of the time difference δt at the current distance measurement timing has increased to a predetermined value or more from the value at the previous distance measurement timing, or decreased to a predetermined value or more than the value at the previous distance measurement timing. Judging whether or not

Now, when the artificial satellite S is approaching, the time difference δt obtained by the time difference timer 5 gradually decreases. However, once the time difference δt reaches “0”, the pulse of the transmission distance measurement signal that is compared with the pulse generated in the reception distance measurement signal in the time difference timer 5 changes, and the time difference δt is a pulse interval A at a stretch. Increase to. Accordingly, when the distance measurement execution interval is T and the maximum possible speed of the artificial satellite S is V, the pulse interval A in the distance measurement signal is
V × T <1/2 × c × A
If the relationship is set so that the following relationship is established, the abrupt change in the value of the time difference δt as described above causes the pulse of the transmission distance measurement signal to be compared with the pulse generated in the reception distance measurement signal in the time difference timer 5. It turns out that it is because it changed. As described above, when the value of the time difference δt increases rapidly, it is when the artificial satellite S is approaching. Therefore, in step ST6, the calculation unit 6 sets [δt−δt ′] to a predetermined reference value δtx. If it is determined that the value is larger than N, N is set to [N-1] by the predicted value correcting means 6b, and the value of the predicted value (A × N) is corrected.

  On the other hand, when the artificial satellite S is moving away, the time difference δt obtained by the time difference timer 5 gradually increases. However, once the time difference δt reaches A, which is the pulse interval, the pulse of the transmission distance measurement signal that is compared with the pulse generated in the reception distance measurement signal in the time difference timer 5 changes, and the time difference δt is “0” at once. Decrease to. Accordingly, if the pulse interval A in the distance measurement signal is set as described above, the abrupt change in the value of the time difference δt as described above is compared with the pulse generated in the received distance measurement signal in the time difference timer 5. It can be seen that this is because the pulse of the transmission ranging signal changes. As described above, when the value of the time difference δt is sharply decreased, it is when the artificial satellite S is approaching. Therefore, in step ST7, the calculation unit 6 sets [δt′−δt] to a predetermined reference value δtx. If it is determined that the value is larger than N, the predicted value correction means 6b corrects the value of the predicted value (A × N) by setting N to [N + 1].

  If calculation unit 6 determines in steps ST6 and ST7 that neither [δt−δt ′] nor [δt′−δt] is greater than a predetermined reference value δtx, the processing of step ST8 and step ST9 is performed. First, keep the predicted value as it is.

  And the calculating part 6 repeats the process after step ST3 using the uncorrected or corrected prediction value.

  Next, the above operation is performed by setting the pulse interval in the distance measurement signal to 100 msec, the distance measurement execution interval to 1 second, and the satellite S is at a distance of 550 msec as the round trip time at the distance measurement start time, corresponding to 1 msec per second. This will be described in detail by taking the case of approaching by distance as an example.

  At this time, at the start of distance measurement, the trajectory prediction unit 7 calculates 500 msec (N = 5) as the predicted value (N × A). Further, the time difference measuring unit 5 calculates 50 msec corresponding to the difference between the round trip time and the predicted value with respect to the true value 550 msec as the time difference δt.

  Thereafter, in the time difference measuring unit 5, the time difference δt every 1 sec is obtained as [49,48,47, ..., 2,1,0,99,98 ...], and the true value of the round trip time is [549,548,547 ... ] Is required.

  Now, when 51 seconds elapse from the start of distance measurement, the time difference δt becomes 99. At this time, if the predicted value is left at 500 ms, the required round-trip time is 599 ms, which changes abruptly from 500 ms one second ago. This proves to be inappropriate because the satellite S has moved a distance corresponding to a round trip time of 99 msec during 1 sec. Therefore, it is possible to obtain 499 ms which is a true value by correcting the predicted value (A × N) to 400 ms by setting N to “4” obtained by subtracting “1” from “5” so far.

  As described above, according to this embodiment, only when the distance measurement is started, the trajectory prediction unit 7 predicts the distance based on the trajectory information, and performs the ambiguity removal using the predicted value calculated thereby. After that, the time difference between the pulse generation in the transmission distance measurement signal and the pulse generation in the reception distance measurement signal is compared with the value at the latest distance measurement timing and the value at the previous distance measurement timing. By correcting the predicted value when a sudden change that exceeds a predetermined specified value δtx occurs, accurate distance measurement can be performed without predicting the distance based on the trajectory information by the trajectory prediction unit 7. The

(Second Embodiment)
Next, a second embodiment of the present invention will be described.

  FIG. 3 is a functional block diagram showing a main configuration of an earth station device configured by applying the distance measuring device according to the present embodiment.

  As shown in this figure, the earth station device of this embodiment includes a ranging signal generator 11, a transmitter 12, an antenna 13, a receiver 14, a transmission PN code position counter 15, a reception PN code position counter 16, a time signal section. 17, a round-trip time counter 18, a reference clock generation unit 19, and a distance measurement processing unit 20.

  The ranging signal generation unit 11 includes a pseudo random noise (PN) code that is a repetition of a bit string of a predetermined pattern formed by arranging “0” or “1” bits, a PN clock synchronized with each bit forming the PN code, and A PN signal composed of a PN epoch synchronized with the first bit of one sequence of the PN code is generated as a ranging signal. The distance measurement signal generated by the distance signal generation unit 11 is supplied to the antenna 13 via the transmission unit 12 and transmitted toward the artificial satellite S as a transmission distance measurement signal.

  The return ranging signal returned by the artificial satellite S is given to the receiving unit 14 via the antenna 13 and is received here.

  The transmission PN code position counter 15 receives a PN epoch of the ranging signal generated by the ranging signal generator 11 as a reset signal and a PN clock as a clock signal. That is, the transmission PN code position counter 15 counts the PN clock of the transmission ranging signal, and the count value is reset when a pulse is generated in the PN epoch of the transmission ranging signal.

  The reception PN code position counter 16 receives a PN epoch of the distance measurement signal (reception distance measurement signal) received by the reception unit 14 as a reset signal and a PN clock as a clock signal. That is, the reception PN code position counter 16 counts the PN clock of the received ranging signal, and the count value is reset when a pulse is generated in the PN epoch of the received ranging signal.

The time signal unit 17 outputs a distance measurement data acquisition request at a predetermined time or a predetermined time interval.

  The round-trip time counter 18 counts a reference clock having a predetermined frequency generated by the reference clock generation unit 19, and the count value is reset under the control of the distance measurement processing unit 20.

  The distance measurement processing unit 20 includes, for example, a microprocessor as a main control circuit, and includes, for example, a round trip timekeeping control unit 20a and a distance calculation unit 20b realized by software processing, for example. Among these, the round trip timekeeping control means 20a determines how many bits in one sequence the PN code output from the distance measurement signal generator 11 in response to the request for distance data acquisition from the time signal section 17 is given. Checking is performed to measure the time until the same bit is generated in the PN code in the received ranging signal. The distance calculation means 20b calculates the distance to the artificial satellite S based on the time measured by the round-trip time counting control means 20a.

  Next, the operation of measuring the distance to the artificial satellite S in the earth station device configured as described above will be described in accordance with the processing procedure of the distance measurement processing unit 20.

  First, the distance measurement processing unit 20 waits for the arrival of a distance measurement data output request output from the time signal unit 17 (step ST11 in FIG. 4). When the ranging data acquisition request arrives, the ranging processing unit 20 waits for the transmission PN code position counter 15 to next count up, takes in the count value N1 after counting up (step ST12), and reciprocates. The time counter 18 is reset (step ST13).

  Here, the transmission PN code position counter 15 counts the PN signal generated by the ranging signal generator 11, that is, the PN clock in the transmission ranging signal, and is reset when a pulse is generated in the PN epoch. Therefore, the count value N1 indicates how many bits in the PN code one sequence is the PN code currently transmitted as the transmission ranging signal.

  Subsequently, the distance measurement processing unit 20 monitors the count value N2 of the reception PN code position counter 16, and waits for this count value N2 to be the same as the count value N1 captured in step ST12 (step ST14 and step ST15). .

  Here, the reception PN code position counter 16 counts the PN signal received by the reception unit 14, that is, the PN clock in the reception distance measurement signal, and is reset when a pulse is generated in the PN epoch. The count value N2 indicates how many bits of the PN code currently received as the received ranging signal is in one sequence of the PN code.

  Thus, if the count value N2 becomes the same as the count value N1 acquired in step ST12, the bit of the PN code sent in the transmission ranging signal immediately after the ranging data acquisition request arrives is folded back by the artificial satellite S. I'm back. Therefore, the distance measurement processing unit 20 takes in the count value N3 of the round trip time counter 18 (step ST16).

  Here, the round trip time counter 18 counts a reference clock having a predetermined frequency generated by the reference clock generator 19, and is reset in step ST13. Therefore, the round-trip time counter 18 counts the number of reference clock cycles from the time when the count value N1 is taken in response to the distance measurement data acquisition request.

Therefore, the distance measurement processing unit 20 calculates the round-trip time ΔT by multiplying the count value N3 captured in step ST16 by the reference clock period δT ′ generated by the reference clock generation unit 19. That is,
ΔT = N3 × δT ′
The round trip time ΔT is calculated by the following equation (step ST17).

The distance measurement processing unit 20
1/2 × ΔT × c
The distance is calculated by the following formula. The distance calculated here represents the distance at the time indicated by [T0 + ΔT / 2], where the distance measurement data acquisition request time is T0.

  After that, the distance measurement processing unit 20 repeats the processes after step ST11.

  Thus, according to the present embodiment, even when the ranging signal generator 11 performs the process of changing the frequency of the ranging signal so as to perform Doppler compensation, the round trip time ΔT can be accurately measured as shown in FIG. And the distance can be calculated accurately.

  The present invention is not limited to the above embodiments. For example, in each of the embodiments described above, the distance measuring device is applied to the earth station device and measures the distance from the earth station to the artificial satellite, but the device to which the distance measuring device of the present invention is applied is not limited to the earth station device. Further, the moving body is not limited to an artificial satellite, and may be another moving body such as an airplane.

  In the first embodiment, a sine wave tone may be used as the distance measurement signal, and the phase difference between the transmission sine wave and the reception sine wave may be measured.

  In addition, various modifications can be made without departing from the scope of the present invention.

The functional block diagram which shows the principal part structure of the earth station apparatus comprised by applying the distance measuring device which concerns on 1st Embodiment of this invention. The flowchart which shows the process sequence of the calculating part 6 in FIG. The functional block diagram which shows the principal part structure of the earth station apparatus comprised by applying the distance measuring apparatus which concerns on 2nd Embodiment of this invention. 4 is a flowchart showing a processing procedure of a distance measurement processing unit 20 in FIG. 3. The figure explaining the operation | movement at the time of the round-trip time of the ranging signal in the earth station apparatus shown in FIG. The figure explaining one conventional method for measuring distance using a single pulse signal. The figure explaining the conventional method for measuring distance when the round trip time of a ranging signal is larger than the generation | occurrence | production interval of the pulse in a transmission ranging signal. The figure which shows the structure of a pseudo random noise signal (PN signal). The figure explaining one conventional method for measuring distance using a pseudo random noise signal. The figure explaining the malfunction when measuring a distance using a pseudo random noise signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ranging signal generation part 2,12 ... Transmission part 3,13 ... Antenna 4,14 ... Reception part 5 ... Time difference time measuring part 6 ... Calculation part 6a ... Time difference comparison means 6b ... Predicted value correction means 6c ... Distance calculation means 7 ... orbit prediction unit 11 ... ranging signal generation unit 15 ... transmission PN code position counter 16 ... reception PN code position counter 17 ... time signal unit 18 ... round-trip time counter 19 ... reference clock generation unit 20 ... distance measurement processing unit 20a ... round-trip Time counting control means 20b Distance calculating means

Claims (2)

In a distance measuring device that measures the distance to a moving body that has a function of returning a received signal,
Ranging for transmitting a ranging signal including a predetermined pseudorandom noise code, a pseudorandom noise clock synchronized with the pseudorandom noise code, and a pseudorandom noise epoch indicating a predetermined bit for each sequence of the pseudorandom noise code Signal transmission means;
Ranging signal receiving means for receiving a ranging signal returned from the mobile body;
Transmission code position detection means for detecting how many bits from a predetermined bit indicated by the pseudo random noise epoch the pseudo random noise code transmitted by the transmission means;
Received code position detecting means for detecting how many bits from a predetermined bit indicated by the pseudo random noise epoch the pseudo random noise code received by the receiving means;
A reference clock generating means for generating a reference clock having a fixed period;
Time measuring means for measuring the time from the predetermined distance measurement start time until the reception code position detection means obtains the same detection result as the detection result of the transmission code position detection means at this time, using the reference clock;
Distance calculating means for calculating the distance to the moving body by using the time measured by the time measuring means as the time required for the distance measurement signal to reciprocate between the moving body and the time measuring means; Distance measuring device. 2. The distance measuring apparatus according to claim 1, wherein the ranging signal transmitting means performs Doppler compensation on the transmitted ranging signal.

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