JP3590198B2 - Distance measuring device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a distance measuring device for measuring a distance to a moving object such as an artificial satellite flying in orbit.
[0002]
[Prior art]
One method for measuring the distance from an earth station to an artificial satellite is to use a single pulse signal.
According to 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 the return of the pulse signal by the artificial satellite to the earth station is measured. As a result, the distance from the earth station to the satellite
1/2 × ΔT × c where c is the speed of light... (1)
It is calculated by the following equation.
[0003]
However, in the above-described method, the distance can be measured only once by transmitting and receiving a pulse signal only once, and a distance measurement signal in which a pulse is continuously generated at a predetermined cycle is used for continuous distance measurement. There is a need. That is, as shown in FIG. 6, a ranging signal (transmission ranging signal) in which a pulse is generated at an interval of time t is transmitted, and after a pulse is generated in the transmission ranging signal, the ranging signal returned 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.
[0004]
At this time, there is no problem if the time required for the ranging signal to reciprocate between the earth station and the artificial satellite is smaller than the pulse generation interval t in the transmission ranging signal as shown in FIG. As shown in FIG. 7, when the interval is longer than the pulse generation interval t in the transmission distance measurement signal, the correspondence between each pulse generated in the transmission distance measurement signal and each pulse generated in the reception distance measurement signal becomes unknown, and the round trip time ΔT becomes longer. It becomes difficult to measure accurately.
[0005]
This problem can be avoided by setting the pulse generation interval in the distance measurement signal to be sufficiently long so that it is always longer than the round trip time ΔT. However, increasing the pulse generation interval t in the ranging signal causes a new problem such as a longer synchronization acquisition time of a receiver that receives the ranging signal in an artificial satellite or an earth station. There is a limit to the length of the distance measurement signal, and it may not be possible to set the pulse generation interval in the distance measurement signal to be longer than the round trip time ΔT.
[0006]
In such a case, conventionally, a predicted value of the round-trip time at each time is calculated based on the orbit information of the artificial satellite in multiples of the pulse generation interval in the transmission ranging signal. 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.
[0007]
Then, the time δt from the occurrence of a pulse in the transmission ranging signal to the occurrence of a pulse in the reception ranging signal is measured, and the true round trip time ΔT is calculated as follows:
ΔT = A × N + δt
It is calculated by the following equation.
[0008]
As described above, the process of calculating the true value by calculating A × N is called ambiguity removal.
However, in this method, it is necessary to calculate in advance the distance prediction values at all the distance measurement data acquisition times, and there is a problem that ambiguity removal is required for all the distance measurement data.
[0009]
On the other hand, another method for measuring the distance from an earth station to an artificial satellite uses a pseudorandom noise (PN) signal as a ranging signal.
As shown in FIG. 8, the PN signal is a PN code which 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 code. It consists of a PN epoch synchronized with the first bit of one sequence.
[0010]
Thus, when this PN signal is used as a ranging signal, a first counter that counts the number of bits of the transmission PN code from the beginning of one sequence and the number of bits of the reception PN code from the beginning of one sequence Are prepared respectively. If the count value of the first counter is N1, the count value of the second counter is N2, and the period of the transmission PN clock is δT, the round trip time ΔT of the distance measurement signal is
ΔT = (N1−N2) × δT (2)
It is obtained by the following formula.
[0011]
Then, the distance from the earth station to the artificial satellite can be obtained by substituting ΔT obtained by this equation into the above 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], where T0 is the distance measurement start time.
[0012]
By the way, when the distance to the artificial satellite is almost constant as shown in FIG. 9, there is no problem since the frequency of the transmission ranging signal and the frequency of the receiving ranging signal are almost the same. However, in practice, the distance to the satellite fluctuates, and the frequency of the ranging signal received by the satellite differs from the frequency of the ranging signal transmitted from the earth station due to the Doppler effect caused by this. Also, as shown in FIG. 10, the frequency of the received ranging signal at the ground station differs from the frequency of the transmitted ranging signal.
[0013]
Therefore, Doppler compensation for controlling the terrestrial transmission frequency so as to cancel the deviation of the satellite reception frequency generated by the Doppler effect due to the motion of the artificial satellite is often performed.
[0014]
When this Doppler compensation is performed, the period δT of the transmission PN clock in the transmission distance measurement signal fluctuates. Therefore, the round trip time ΔT cannot be obtained by the above equation (2), and the distance cannot be measured. Would. That is, the method using the PN signal has a problem that it cannot cope with the case where Doppler compensation is performed.
[0015]
[Problems to be solved by the invention]
As described above, in the conventional distance measuring device, when distance measurement is performed using a distance measurement signal using a single pulse, if the pulse interval cannot be made longer than the round trip time of the distance measurement signal, In this case, it is necessary to obtain a predicted value of the distance related to the distance measurement timing in advance, and to remove the ambiguity at all the distance measurement timings, so that the processing is very complicated.
[0016]
When the distance is measured using the PN signal as the ranging signal, the round trip time of the ranging signal is obtained by counting the PN clock in the transmitted ranging signal. There was a problem that the round trip time of the signal could not be obtained accurately, and the distance measurement could not be performed accurately.
[0017]
The present invention has been made in view of such circumstances, and an object of the present invention is to firstly start distance measurement when a distance measurement is performed using a distance measurement signal using a single pulse. Distance elimination device that eliminates the need for ambiguity removal using the predicted value of the distance obtained in advance only at the time of initial distance measurement at the time, and can easily perform distance measurement at subsequent timings Is to provide.
[0019]
[Means for Solving the Problems]
In order to achieve the first object, the present invention provides a distance measuring signal transmitting unit which transmits a distance measuring signal in which a pulse is generated at a predetermined cycle, for example, a distance measuring signal generating unit, a transmitting unit and an antenna; Receiving the ranging signal returned from the body, for example, a ranging signal receiving unit including an antenna and a receiving unit, and the ranging signal after a pulse is generated in the ranging signal transmitted by the ranging signal transmitting unit; The distance measurement signal between the moving object such as an artificial satellite and a time measurement unit such as a time difference timer that repeatedly measures the time until a pulse is generated in the distance measurement signal received by the reception unit at a predetermined cycle. A distance estimating means such as a trajectory estimating unit for estimating a predicted value of a time required for the vehicle to make a round trip at the start of ranging based on the moving route information of the moving body, Is compared with the time measured at the timing one cycle before by the time measuring means, for example, a comparing means such as a time difference comparing means, and the comparing means determines that the time measured by the time measuring means has increased by a predetermined value or more. When the predicted value is a value obtained by subtracting a predetermined value from the previous value, and when it is determined by the comparing means that the time measured by the time measuring means has decreased by a predetermined value or more, the predicted value is set to the value obtained up to that time. Predicted value correcting means for increasing a predetermined value from a value, and distance calculating means for calculating a distance to the moving object based on a time obtained by adding the predicted value to the time measured by the time measuring means. And with.
[0020]
By taking such measures, the distance to the moving object is determined by a time difference between the generation of a pulse in the transmission ranging signal and the generation of a pulse in the reception ranging signal, and a prediction value, which is similar to ambiguity removal. The predicted value is predicted based on the moving route information of the moving object only at the start of the ranging operation, and thereafter, the time difference between the pulse generation in the transmission ranging signal and the pulse generation in the receiving ranging signal is changed. Is corrected to an appropriate value.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
(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.
[0024]
As shown in this figure, the earth station apparatus of the present embodiment has a ranging signal generating unit 1, a transmitting unit 2, an antenna 3, a receiving unit 4, a time difference timer 5, a calculating unit 6, and an orbit predicting unit 7. I have.
[0025]
The ranging signal generator 1 generates a ranging signal in which a single pulse is generated at a predetermined cycle (an interval of a predetermined time A). The ranging signal generated by the ranging signal generator 1 is supplied to the antenna 3 via the transmitter 2 and transmitted to the artificial satellite S as a transmission ranging signal.
[0026]
The return ranging signal returned by the artificial satellite S is provided to the receiving unit 4 via the antenna 3 and received here.
The time difference timer 5 measures the time difference δt from when a pulse is generated in the ranging signal generated by the ranging signal generator 1 to when a pulse is generated in the ranging signal received by the receiver 4. Notify 6.
[0027]
The arithmetic unit 6 includes, for example, a microprocessor as a main control circuit, and includes a time difference comparing unit 6a, a predicted value correcting unit 6b, and a distance calculating unit 6c, each of which is realized by, for example, software processing. The time difference comparing means 6a compares the difference between the time difference currently output by the time difference timer 5 and the time difference output at the previous timing with a predetermined specified value. The predicted value correcting means 6b corrects the predicted value used for the distance calculation by the distance calculating means 6c as needed based on the comparison result by the time difference comparing means 6a. The distance calculating means 6c performs a process for calculating the distance to the artificial satellite S based on the time difference δt measured by the time difference timer 5 and a predicted value obtained in advance.
[0028]
The orbit predicting unit 7 obtains an initial predicted value at the time when the arithmetic unit 6 starts ranging based on the orbit information of the artificial satellite S, and gives it to the calculating unit 6.
Next, an 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 arithmetic unit 6.
First, when the arithmetic unit 6 is activated and starts the distance measuring operation, the orbit estimating unit 7 makes the orbit estimating unit 7 estimate 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 measurement 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).
[0029]
Then, the calculation unit 6 takes in the value output by the trajectory prediction unit 7 as a prediction value as described above (step ST1 in FIG. 2). Further, the arithmetic unit 6 captures the time difference δt output from the time difference timer unit 5 at that time (step ST2).
[0030]
Next, the arithmetic unit 6 calculates the distance to the artificial satellite S by the distance calculating means 6c.
1/2 × {(A × N) + δt} × c
It is calculated by the following equation.
[0031]
Here, at the time of the first distance calculation after the start of the distance measurement, (A × N) is a value predicted by the trajectory prediction unit 7, and therefore, the distance calculation processing by the same method as in the related art for removing ambiguity is performed. Will be performed.
[0032]
When a predetermined time (for example, 1 second) has elapsed since the time when the time difference δt output by the time difference timer 5 was previously captured, the calculation unit 6 calculates the value of the time difference δt used for calculating the distance in step ST3. δt ′ (step ST4), and the time difference δt currently output by the time difference timer 5 is newly fetched (step ST5). Thus, δt indicates the time difference at the latest distance measurement timing, and δt 'indicates the time difference at the immediately preceding distance measurement timing.
[0033]
Then, the arithmetic unit 6 uses the time difference comparing unit 6a to set [δt−δt ′] to a predetermined reference value δt. _x And whether [δt′−δt] is greater than a predetermined reference value δt _x It is determined whether or not it is greater than (steps ST6 and ST7). That is, in steps ST6 and ST7, the arithmetic unit 6 compares the value of the time difference δt output by the time difference timer unit 5 with the value at the immediately preceding ranging timing, and the difference between the two becomes a predetermined value abnormality. To determine whether or not. More specifically, the value of the time difference δt at the current ranging timing has increased from a value at the immediately preceding ranging timing to a predetermined value or more, or decreased to a predetermined value or more than the value at the previous ranging timing. Has been determined.
[0034]
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 ranging signal that is compared with the pulse generated in the reception ranging signal in the time difference timer 5 changes, and the time difference δt is the pulse interval A at a stretch. To increase. Therefore, assuming that the distance measurement execution interval is T and the maximum possible speed of the satellite S is V, the pulse interval A in the distance measurement signal is
V × T <1/2 × c × A
If the relationship is established so that the following relationship is established, the abrupt change in the value of the time difference δt as described above will cause the pulse of the transmission ranging signal to be compared with the pulse generated in the reception ranging signal by the time difference timer 5. It turns out that it is because it changed. Then, as described above, when the value of the time difference δt sharply increases, it is when the artificial satellite S is approaching. Therefore, in step ST6, the arithmetic unit 6 sets [δt−δt ′] to the predetermined reference value δt. _x If it is determined that the value is larger than N, the predicted value (A × N) is corrected by the predicted value correcting means 6b, where N is [N−1].
[0035]
Conversely, 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 the pulse interval A, the pulse of the transmission ranging signal compared with the pulse generated in the reception ranging signal in the time difference timer 5 changes, and the time difference δt is “0” at a stroke. To decrease. Therefore, if the pulse interval A in the ranging 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 ranging signal by the time difference timer 5. It can be understood that this is because the pulse of the transmission ranging signal has changed. When the value of the time difference δt is sharply reduced as described above, since the artificial satellite S is approaching, the calculation unit 6 determines in step ST7 that [δt′−δt] is equal to the predetermined reference value δt. _x If it is determined that the value is larger than N, the predicted value (A × N) is corrected by the predicted value correcting means 6b by setting N to [N + 1].
[0036]
In step ST6 and step ST7, the arithmetic unit 6 sets both [δt−δt ′] and [δt′−δt] to the predetermined reference value δt. _x If it is determined that it is not larger than the above, the processing of steps ST8 and ST9 is not performed, and the predicted value is kept as it is.
[0037]
Then, the calculation unit 6 repeats the processing after step ST3 using the uncorrected or corrected predicted value.
Next, in the above operation, the interval between pulses in the ranging signal is set to 100 msec, the interval for performing ranging is set to 1 sec, and the artificial satellite S is located at a distance of 550 msec as a round trip time at the ranging start time, which corresponds to 1 msec per second. This will be described in detail with an example of a case in which the distance is approaching.
[0038]
At this time, at the start of ranging, the trajectory prediction unit 7 calculates 500 msec (N = 5) as a predicted value (N × A). Further, the time difference timer 5 obtains 50 msec corresponding to the difference between the true value of the round trip time 550 msec and the predicted value as the time difference δt.
[0039]
Thereafter, the time difference timer 5 obtains the time difference δt every 1 sec as [49, 48, 47, ..., 2, 1, 0, 99, 98 ...], and the true value of the round trip time is [549, 548, 547...].
[0040]
When 51 seconds have elapsed since the start of the distance measurement, the time difference δt becomes 99. At this time, if the predicted value is kept at 500 ms, the required reciprocating time is 599 ms, which rapidly changes from 500 ms one second before. This means that the artificial satellite S has moved a distance corresponding to a reciprocation time of 99 msec during 1 sec, and thus it is found to be inappropriate. Therefore, by correcting N to “4” obtained by subtracting “1” from “5” so far and correcting the predicted value (A × N) to 400 ms, it is possible to obtain the true value of 499 ms.
[0041]
As described above, according to the present embodiment, the trajectory prediction unit 7 predicts the distance based on the trajectory information only at the time of starting the distance measurement, and removes the ambiguity using the predicted value calculated thereby. Thereafter, the time difference between the pulse generation in the transmission ranging signal and the pulse generation in the reception ranging signal is compared with the value at the latest ranging timing and the value at the immediately preceding ranging timing, and the difference between the two is compared. Is a predetermined specified value δt _x By correcting the predicted value based on the occurrence of a sudden change exceeding the range, accurate distance measurement can be performed without predicting the distance based on the trajectory information by the trajectory prediction unit 7.
[0042]
(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 to which the distance measuring device according to the present embodiment is applied.
[0043]
As shown in this figure, the earth station device of the present 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, and a time signal unit. 17, a round-trip time counter 18, a reference clock generator 19 and a distance measurement processor 20.
[0044]
The ranging signal generator 11 includes a pseudo random noise (PN) code, which 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 constituting 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 ranging signal generated by the ranging signal generation unit 11 is supplied to the antenna 13 via the transmission unit 12 and transmitted to the artificial satellite S as a transmission ranging signal.
[0045]
The return ranging signal returned by the artificial satellite S is provided to the receiving unit 14 via the antenna 13 and received here.
In the transmission PN code position counter 15, the PN epoch of the ranging signal generated by the ranging signal generator 11 is input as a reset signal, and the PN clock is input 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 by generating a pulse in the PN epoch of the transmission ranging signal.
[0046]
In the reception PN code position counter 16, the PN epoch of the ranging signal (reception ranging signal) received by the receiving unit 14 is input as a reset signal, and the PN clock is input as a clock signal. That is, the reception PN code position counter 16 counts the PN clock of the received distance measurement signal, and the count value is reset by generating a pulse in the PN epoch of the received distance measurement signal.
[0047]
The time signal unit 17 outputs a distance measurement data acquisition request at a predetermined time or at a predetermined time interval.
The round-trip time counter 18 counts a reference clock of a predetermined frequency generated by the reference clock generator 19, and the count value is reset under the control of the distance measurement processor 20.
[0048]
The distance measurement processing unit 20 has, for example, a microprocessor as a main control circuit, and has a round-trip time measuring control unit 20a and a distance calculation unit 20b, each of which is realized by, for example, software processing. Among them, the round-trip time counting control means 20a determines which bit in the one sequence the PN code output by the ranging signal generating section 11 in response to the request for obtaining ranging data from the time signal section 17. This is a process for checking and measuring the time until the same bit occurs in the PN code in the received ranging signal. The distance calculating means 20b calculates the distance to the artificial satellite S based on the time measured by the round-trip time measuring control means 20a.
[0049]
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 distance measurement processing unit 20.
First, the ranging processing unit 20 waits for the arrival of the ranging data acquisition request output from the time signal unit 17 (step ST11 in FIG. 4). When the distance measurement data acquisition request arrives, the distance measurement processing section 20 waits for the next transmission PN code position counter 15 to count up, captures the count value N1 after the count up (step ST12), and reciprocates. The time counter 18 is reset (step ST13).
[0050]
Here, the transmission PN code position counter 15 counts a PN signal generated by the distance measurement signal generation unit 11, that is, a PN clock in the transmission distance measurement signal, and is reset when a pulse is generated in the PN epoch. Therefore, the count value N1 indicates the bit number of the PN code currently transmitted as the transmission ranging signal in one sequence of the PN code.
[0051]
Subsequently, the distance measurement processing unit 20 monitors the count value N2 of the reception PN code position counter 16, and waits until the count value N2 becomes equal to the count value N1 captured in step ST12 (steps ST14 and ST15). .
[0052]
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 received distance measurement signal, and is reset by the occurrence of a pulse in the PN epoch. The count value N2 indicates the bit number of the PN code currently received as the received ranging signal in one sequence of the PN code.
[0053]
Thus, when the count value N2 becomes equal to the count value N1 captured in step ST12, the PN code bit transmitted by the transmission ranging signal immediately after the arrival of the ranging data acquisition request arrives at the artificial satellite S. You have returned. Therefore, the distance measurement processing section 20 takes in the count value N3 of the round trip time counter 18 (step ST16).
[0054]
Here, the round-trip time counter 18 counts the reference clock of a predetermined frequency generated by the reference clock generator 19, and has been reset in step ST13. Therefore, the round-trip time counter 18 counts the number of periods of the reference clock from the time when the count value N1 is fetched in response to the distance measurement data acquisition request.
[0055]
Therefore, the distance measurement processing unit 20 calculates the round trip time ΔT by multiplying the count value N3 fetched in step ST16 by the period δT ′ of the reference clock 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).
[0056]
And the distance measurement processing unit 20
1/2 × ΔT × c
The distance is calculated by the following equation. Note that the distance calculated here represents the distance at the time indicated by [T0 + ΔT / 2], where T0 is the distance measurement data acquisition request time.
[0057]
Thereafter, the distance measurement processing unit 20 repeats the processing after step ST11.
Thus, according to the present embodiment, even when the ranging signal generating unit 11 changes the frequency of the ranging signal to perform Doppler compensation, the round trip time ΔT can be accurately measured as shown in FIG. The distance can be accurately calculated.
[0058]
The present invention is not limited to the above embodiments. For example, in each of the above embodiments, the present invention is applied to the earth station device and measures the distance from the earth station to the artificial satellite. However, the device to which the distance measuring device of the present invention is applied is not limited to the earth station device. The moving object is not limited to the artificial satellite, but may be another moving object such as an airplane.
[0059]
In the first embodiment, a sine wave tone may be used as the distance measurement signal, and the phase difference between the transmitted sine wave and the received sine wave may be measured.
In addition, various modifications can be made without departing from the spirit of the present invention.
[0060]
【The invention's effect】
The present invention transmits a ranging signal in which a pulse is generated in a predetermined cycle, for example, a ranging signal transmitting unit including a ranging signal generating unit, a transmitting unit, and an antenna, and receives a ranging signal returned from the moving body. For example, a ranging signal receiving unit including an antenna and a receiving unit, and a ranging signal received by the ranging signal receiving unit after a pulse is generated in the ranging signal transmitted by the ranging signal transmitting unit. A predicted value of the time required for the distance measurement signal to reciprocate between a time measuring means such as a time difference timer and a moving object such as an artificial satellite which repeatedly measures the time until a pulse is generated at a predetermined cycle. At the start of distance measurement based on the movement route information of the moving body, for example, a distance prediction unit such as a trajectory prediction unit, and the time measured by the time measurement unit is set to one cycle by the time measurement unit. A comparing means such as a time difference comparing means for comparing with the time measured at the timing of, and when it is determined by the comparing means that the time measured by the time measuring means has increased by a predetermined value or more, the predicted value is calculated up to that time. A value obtained by subtracting a predetermined value from the value, and when it is determined by the comparing means that the time measured by the timing means has decreased by a predetermined value or more, the predicted value is a value obtained by increasing the predetermined value from the previous value. Prediction value correction means, and the distance calculation means for calculating the distance to the moving object based on the time obtained by adding the prediction value to the time measured by the time measurement means, so that a single-shot pulse When performing distance measurement using the ranging signal used, the ambiguity using the predicted distance value obtained in advance only at the initial ranging at the start of ranging. By performing the removed by, a distance measuring apparatus capable of easily ranging them as unnecessary in subsequent timing.
[Brief description of the drawings]
FIG. 1 is a functional block diagram illustrating a configuration of a main part of an earth station device configured by applying a distance measuring device according to a first embodiment of the present invention.
FIG. 2 is a flowchart showing a processing procedure of a calculation unit 6 in FIG.
FIG. 3 is a functional block diagram showing a configuration of a main part of an earth station device configured by applying a distance measuring device according to a second embodiment of the present invention.
FIG. 4 is a flowchart showing a processing procedure of a distance measurement processing unit 20 in FIG. 3;
FIG. 5 is a view for explaining the operation of measuring the round trip time of the ranging signal in the earth station apparatus shown in FIG. 3;
FIG. 6 is a diagram illustrating a conventional method for measuring a distance using a single pulse signal.
FIG. 7 is a view for explaining a conventional method for measuring a distance when a round trip time of a ranging signal is longer than a pulse generation interval of a transmission ranging signal.
FIG. 8 is a diagram showing a configuration of a pseudo random noise signal (PN signal).
FIG. 9 is a view for explaining a conventional method for measuring a distance using a pseudo-random noise signal.
FIG. 10 is a diagram illustrating a problem when measuring a distance using a pseudo random noise signal.
[Explanation of symbols]
1: Distance measurement signal generator
2, 12 ... transmission unit
3,13 ... antenna
4,14 ... Receiver
5: Time difference timer
6 arithmetic unit
6a: Time difference comparison means
6b: predicted value correction means
6c distance calculating means
7 orbit prediction unit
11 Distance measuring signal generator
15: Transmission PN code position counter
16 ... Received PN code position counter
17: Time signal section
18 Round trip time counter
19: Reference clock generator
20 Distance measuring unit
20a: Round-trip time counting control means
20b ... Distance calculation means

Claims (1)

In a distance measuring device that measures a distance to a moving object having a function of returning a received signal,
Distance measurement signal transmitting means for transmitting a distance measurement signal in which a pulse is generated at a predetermined cycle;
Distance measurement signal receiving means for receiving a distance measurement signal returned from the moving object,
A timer for repeatedly measuring, at a predetermined cycle, the time from when a pulse is generated in the ranging signal transmitted by the ranging signal transmitting means to when a pulse is generated in the ranging signal received by the ranging signal receiving means. Means,
Distance predicting means for predicting a predicted value of a time required for the distance measurement signal to reciprocate between the moving object and the moving object at the start of ranging based on moving route information of the moving object;
Comparing means for comparing the time measured by the time measuring means with the time measured at a timing one cycle before by the time measuring means;
When it is determined by the comparing means that the time counted by the timing means has increased by a predetermined value or more, the predicted value is set to a value obtained by subtracting a predetermined value from the previous value. When it is determined that the time has decreased by a predetermined value or more, a predicted value correction unit that sets the predicted value to a value obtained by increasing a predetermined value from the previous value,
A distance measuring device, comprising: distance calculating means for calculating a distance to the moving object based on a time obtained by adding the predicted value to the time measured by the time measuring means.

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