JP2004125733A - Apparatus and method for measuring distance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for measuring a distance having a simple structure and improved distance resolution. <P>SOLUTION: A sender generates a first pseudo random signal. The sender also generates a second pseudo random signal, having a chip rate equal to that of the first pseudo random signal and has a low correlation to the first pseudo random signal, at a time delayed by a half chip rate time from the time the first pseudo random signal is generated. A transmission processor 30 superimposes the first pseudo random signal and the second pseudo random signal to make a transmission signal. The sender samples the transmission signal at a time interval equal to the chip rate. A first correlator 70 calculates the correlation between the transmission signal and the first pseudo random signal. A second correlator 80 calculates the correlation between the transmission signal and the second pseudo random signal. A calculator 90 calculates a distance of the target based on the correlation of the first correlator 70 and the correlation of the second correlator 80. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a distance measuring device and a distance measuring method using spread spectrum.
[0002]
[Prior art]
In the distance measuring method using spread spectrum, a pseudo-random signal is transmitted, a correlation value between the received signal reflected back to the target and the pseudo-random signal is obtained, and a distance to the target is calculated based on the correlation value. Is calculated. In a normal distance measurement method using spread spectrum, the unit of measurement of distance is equal to the chip rate of the pseudo-random signal. For this reason, various devices have been conventionally devised in order to increase the resolution of the distance to a chip rate or more. For example, there is a technique for improving the distance resolution by using an interpolation method (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2001-51046 A
[0004]
[Problems to be solved by the invention]
However, in order to increase the distance resolution by the conventional distance measuring method, it is difficult to realize such a method as requiring a plurality of sampling rates. Therefore, realization of a distance measuring device and a distance measuring method capable of improving the distance resolution with a simple configuration is desired.
[0005]
The present invention has been made based on the above circumstances, and an object of the present invention is to provide a distance measuring device and a distance measuring method which can improve a distance resolution with a simple configuration.
[0006]
[Means for Solving the Problems]
To achieve the above object, a distance measuring apparatus according to the invention according to claim 1 is provided on a transmitting side, first transmitting side signal generating means for generating a first pseudo random signal, and provided on a transmitting side. The second pseudo-random signal having the same chip rate as the first pseudo-random signal and having a low correlation with the first pseudo-random signal, The second transmission-side signal generation means and the first pseudo-random signal generated by the first transmission-side signal generation means, which is generated with a delay of half the chip rate than the generation timing of the pseudo-random signal, A transmission processing unit for generating a superimposed signal by superimposing the second pseudo-random signal generated by the second transmission-side signal generation unit and transmitting the superimposed signal to a target; Receiving the superimposed signal returned by reflection, receiving processing means for sampling the received signal at the same time interval as the chip rate, provided on the receiving side, the first pseudo-random signal The first receiving-side signal generating means to be generated and the second pseudo-random signal provided on the receiving side are generated simultaneously with the generation timing of the first pseudo-random signal by the first receiving-side signal generating means. A second reception-side signal generation unit, and a first correlation calculation for calculating a correlation between the reception signal sampled by the reception processing unit and the first pseudo-random signal generated by the first reception-side signal generation unit Means for calculating a correlation between the reception signal sampled by the reception processing means and the second pseudo-random signal generated by the second reception-side signal generation means. Correlation calculating means, and calculating means for calculating a distance to the target based on the correlation value output from the first correlation calculating means and the correlation value output from the second correlation calculating means. It is characterized by the following.
[0007]
According to a second aspect of the present invention, in the distance measuring device according to the first aspect, the calculation means outputs a correlation value output from the first correlation calculation means and a correlation value output from the second correlation calculation means at each correlation position. Find the sum with the correlation value, find the position where the sum is the maximum as the reference position, the delay time from the transmission of the superimposed signal to the reception based on the reference position is the same time unit as the chip rate Comparing the correlation value output from the first correlation calculation means with the correlation value output from the second correlation calculation means at the reference position found by the delay time calculation means. First correction time calculating means for obtaining a first correction time for the delay time based on a comparison result of the two correlation values in a unit of half of the chip rate; and The correlation calculation means having the smaller correlation value is specified based on the comparison result in the interval calculation means, and the specified correlation calculation means calculates the correlation value at the reference position and the correlation value at two correlation positions adjacent to the reference position. Using the larger correlation value of the correlation values, the position of the center of gravity with respect to the intermediate position between the correlation positions taking the two correlation values is calculated, and the second position with respect to the delay time is calculated based on the calculated position of the center of gravity. A second correction time calculation unit for obtaining a correction time; and a distance calculation unit for obtaining a distance to the target based on a time obtained by adding the delay time, the first correction time, and the second correction time. It is characterized by the following.
[0008]
The distance measuring method according to the third aspect of the present invention for achieving the above object, on the transmitting side, generates a first pseudo-random signal and has the same chip rate as the first pseudo-random signal. And a first step of generating a second pseudo-random signal having a low correlation with the first pseudo-random signal by delaying the generation timing of the first pseudo-random signal by half the chip rate. A second step of generating a superimposed signal by superimposing the first pseudo-random signal and the second pseudo-random signal generated in the first step and transmitting the superimposed signal to a target; A third step of receiving the superimposed signal that has returned and returning, and sampling the received signal at the same time interval as the chip rate; On the side, while generating the first pseudo-random signal, the second pseudo-random signal, the fourth step to occur simultaneously with the generation timing of the first pseudo-random signal, and sampled in the third step A fifth step of calculating a correlation between the received signal and the first pseudo-random signal generated in the fourth step, and the received signal sampled in the third step and generated in the fourth step. A sixth step of calculating a correlation with the second pseudo-random signal, and calculating a distance to the target based on the correlation value obtained in the fifth step and the correlation value obtained in the sixth step. And a seventh step.
[0009]
According to a fourth aspect of the present invention, in the distance measuring method according to the third aspect, the seventh step calculates a sum of the correlation value obtained in the fifth step and the correlation value obtained in the sixth step at each correlation position. Calculating, finding the position where the sum is the maximum as the reference position, calculating the delay time from the transmission of the superimposed signal to the reception based on the reference position in the same time unit as the chip rate, The correlation value obtained in the fifth step and the correlation value obtained in the sixth step are compared at the reference position, and a first correction time for the delay time is set based on a comparison result of the two correlation values. A step of obtaining a time unit of a half of the chip rate, and identifying a correlation output having a smaller correlation value based on a comparison result of the two correlation values. And using the correlation value at the reference position and the larger one of the correlation values at two correlation positions adjacent to the reference position, using the center of gravity with respect to the intermediate position between the correlation positions taking the two correlation values. Calculating a second correction time for the delay time based on the calculated position of the center of gravity, and a time obtained by adding the delay time, the first correction time, and the second correction time. Obtaining a distance to the target based on the distance.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram of a distance measuring device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining signals output from each section of the distance measuring device, and FIG. 3 is used in the distance measuring device. FIG. 4 is a diagram for explaining output characteristics of a correlator.
[0011]
The distance measuring apparatus according to the present embodiment measures a distance to a target. As shown in FIG. 1, a first transmitting PN (pseudorandom) signal generator 10 and a second transmitting PN signal generator , A transmission processing unit 30, a reception processing unit 40, a first receiving PN signal generator 50, a second receiving PN signal generator 60, a first correlator 70, And a computing unit 90. Here, an example of baseband processing will be described to simplify the description. When the distance measurement device of the present embodiment is applied to, for example, a radar or the like, an RF modulator may be provided in the transmission processing unit 30 and an RF demodulator may be provided in the reception processing unit 40.
[0012]
The first transmitting PN signal generator 10 generates a first pseudo-random signal, and the second transmitting PN signal generator 20 generates a second pseudo-random signal. The chip rate of the first pseudo-random signal is the same as the chip rate of the second pseudo-random signal. The chip rate is the width (time) of a unit signal constituting a pseudo random signal. Further, the first pseudo-random signal and the second pseudo-random signal having low correlation with each other are used. For example, when these pseudorandom signals are both M-sequence signals, a preferred pair or the like can be used as the two pseudorandom signals.
[0013]
The first pseudo-random signal generated by the first transmission-side PN signal generator 10 and the second pseudo-random signal generated by the second transmission-side PN signal generator 20 are output to the transmission processing unit 30. . In the present embodiment, as shown in FIG. 2A, the second transmission-side PN signal generator 20 converts the second pseudo-random signal to a half of the chip rate Tc from the generation timing of the first pseudo-random signal. It is delayed by the time. Therefore, the second pseudo-random signal is output to the transmission processing unit 30 with a delay of half the chip rate Tc as compared with the first pseudo-random signal.
[0014]
The transmission processing unit 30 includes an adder 31 and a transmission unit 32. The adder 31 superimposes the first pseudo-random signal generated by the first transmission-side PN signal generator 10 and the second pseudo-random signal generated by the second transmission-side PN signal generator 20. Thus, a superimposed signal is generated. Since the second pseudo-random signal is generated with a delay of half the chip rate Tc from the generation timing of the first pseudo-random signal, the first pseudo-random signal and the second pseudo-random signal are generated in this superimposed signal. The random signal is superimposed with a time shifted by half the chip rate Tc. The transmitting section 32 transmits the superimposed signal to the target as a transmission signal.
[0015]
The reception processing unit 40 has a reception unit 41 and an A / D converter 42. The receiving unit 41 receives the superimposed signal reflected from the target and returned. The superimposed signal (received signal) received by the receiver 41 is A / D converted by the A / D converter 42. At this time, the sampling time during which the A / D converter 42 samples the received signal is equal to the chip rate Tc of the first pseudo random signal (second pseudo random signal). That is, the A / D converter 42 samples the received signal at the same time interval as the chip rate Tc. The received signal sampled by the A / D converter 42 is output to the first correlator 70 and the second correlator 80.
[0016]
The first receiving-side PN signal generating section 50 generates a first pseudo-random signal and outputs it to the first correlator 70. The second receiving-side PN signal generating section 60 generates a second pseudo-random signal. It generates a random signal and outputs it to the second correlator 80. On the transmission side, as described above, the second pseudo-random signal from the second transmission-side PN signal generator 20 is used to generate the first pseudo-random signal from the first transmission-side PN signal generator 30. It has been delayed by half the chip rate Tc from the timing. On the other hand, on the receiving side, as shown in FIG. 2B, the first pseudo-random signal from the first receiving-side PN signal generator 50 and the second pseudo-random signal from the second receiving-side PN signal generator 70 are used. The second pseudo-random signal is generated at the same time. Therefore, the first pseudo-random signal from the first receiving-side PN signal generator 50 and the second pseudo-random signal from the second receiving-side PN signal generator 60 are generated at the same timing, and The signals are input to one correlator 70 and the second correlator 80 at the same time.
[0017]
The first correlator 70 calculates a correlation value between the reception signal sampled by the reception processing unit 40 and the first pseudo-random signal generated by the first reception-side PN signal generation unit 50. The bi-correlator 80 calculates a correlation value between the reception signal sampled by the reception processing unit 40 and the second pseudo-random signal generated by the second reception-side PN signal generation unit 60. Specifically, each of the correlators 70 and 80 calculates the correlation value while shifting one of the phases of the received signal and the pseudo-random signal by a predetermined phase value corresponding to the chip rate Tc.
[0018]
FIG. 3 shows output characteristics of the correlators 70 and 80 used in the present embodiment. This output characteristic is obtained by using two identical pseudo-random signals and inputting those pseudo-random signals to the correlator at the same timing. In FIG. 3, the vertical axis represents the output of the correlator, and the horizontal axis represents the amount of correlation deviation. The correlation shift amount is an amount corresponding to the phase value shifted when the correlation value is obtained. Here, the time corresponding to the shifted phase value is represented by the chip rate Tc as the correlation shift amount. Use something. In the following, the amount of correlation deviation is also referred to as “correlation position”.
[0019]
As shown in FIG. 3, when the correlation position is 0, the correlation value output from the correlator has a peak. The correlation value decreases substantially linearly as the correlation position gradually moves from 0 toward ± 1. Here, in the range of the correlation position from -1 to +1, the correlation value is substantially symmetric with respect to the vertical axis passing through the origin. When the correlation position is apart from ± 1, the correlation value changes and takes a small value. Note that, as an output characteristic of the correlator, ideally, as shown by a broken line in FIG. 3, the correlation value changes linearly when the correlation position is in the range from 0 to +1 or in the range from 0 to -1. In the range where the correlation position is +1 or more or -1 or less, it is desirable that the correlation value take a minute constant value. The output characteristics of the actual correlator are approximately similar to the ideal output characteristics.
[0020]
Therefore, in the first correlator 70, the phase of the first pseudo-random signal included in the received signal and the phase of the first pseudo-random signal generated by the first receiving-side PN signal generation unit 60 completely match. The maximum peak value is output. If the phases of these two signals are shifted by a value smaller than the phase value corresponding to the chip rate Tc, a peak value smaller than the maximum peak value but somewhat larger is output. This corresponds to the case where the correlation position is in the range from 0 to +1 or in the range from 0 to −1 in FIG. Further, when the phases of these two signals are shifted by a value larger than the phase value corresponding to the chip rate Tc, the correlation value is almost zero. This corresponds to the case where the correlation position is in the range of +1 or more or -1 or less in FIG.
[0021]
Similarly, in the second correlator 80, the phase of the second pseudo-random signal included in the received signal matches the phase of the second pseudo-random signal generated by the second receiving-side PN signal generation unit 70. In this case, the maximum peak value is output. If the phases of these two signals are shifted by a value smaller than the phase value corresponding to the chip rate Tc, a peak value smaller than the maximum peak value but somewhat larger is output. Further, when the phases of these two signals are shifted by a value larger than the phase value corresponding to the chip rate Tc, the correlation value is almost zero.
[0022]
By the way, in the present embodiment, when generating the superimposed signal on the transmitting side, the first pseudo random signal and the second pseudo random signal are shifted by half the chip rate Tc. Therefore, for example, when the time (delay time) from the transmission of the superimposed signal to the reception of the superimposed signal reflected back from the target is exactly a natural number multiple of the chip rate Tc, the first correlator is used. When calculating the correlation value in 70, the phase of the first pseudo-random signal included in the received signal exactly matches the phase of the first pseudo-random signal generated by the first receiving-side PN signal generation unit 50 May be. Then, when the phases of the two signals coincide with each other, the maximum peak value (1) is output from the first correlator 70 as shown in FIG. On the other hand, in this case, in the second correlator 80, the phase of the second pseudo-random signal included in the received signal and the phase of the second pseudo-random signal generated by the second Are not exactly the same, but the phases of those signals are shifted twice by a phase value corresponding to a half of the chip rate Tc. Then, when the phases of these two signals are shifted by a phase value corresponding to half the time of the chip rate Tc, as shown in FIG. 2D, two peak values {2} are output from the second correlator 80. , (3) are output. Here, of the two peak values (2) and (3) in the second correlator 80, the previously output peak value (2) appears simultaneously with the maximum peak value (1) in the first correlator 70. In FIGS. 2 (c) and 2 (d), minute values are output in addition to the peak values (1), (2) and (3). This corresponds to an output value in the case of a range of +1 or more or a range of -1 or less, and is treated as noise.
[0023]
If the delay time is exactly equal to (natural number + ／) times the chip rate Tc, the second correlator 80 determines the phase of the second pseudo-random signal included in the received signal and the second receiving-side PN. The phase of the second pseudo-random signal generated by the signal generator 50 may be exactly the same. When the phases of the two signals match, the maximum peak value is output from the second correlator 80. On the other hand, in this case, in the first correlator 70, the phase of the first pseudo-random signal included in the received signal and the phase of the first pseudo-random signal generated by the first Are not exactly the same, but the phases of those signals are shifted twice by a phase value corresponding to a half of the chip rate Tc. Then, when the phases of these signals are shifted by a phase value corresponding to half the time of the chip rate Tc, the first correlator 70 outputs two peak values. Here, the peak value output later of the two peak values in the first correlator 70 appears at the same time as the maximum peak value in the second correlator 80.
[0024]
Generally speaking, when a superimposed signal is generated on the transmitting side, the first pseudo-random signal and the second pseudo-random signal are superimposed by being shifted by half the chip rate Tc, so that the first correlation One peak value is output from one of the detector 70 and the second correlator 80, and two peak values are output from the other one. In the present embodiment, as described in detail below, the calculation unit 90 calculates the distance to the target with a resolution equal to or less than the chip rate Tc based on the three peak values.
[0025]
The calculation section 90 calculates the distance to the target based on the first correlation output obtained by the first correlator 70 and the second correlation output obtained by the second correlator 80. As shown in FIG. 1, the calculation unit 90 includes a delay time calculation unit 91, a first correction time calculation unit 92, a second correction time calculation unit 93, and a distance calculation unit 94.
[0026]
The delay time calculation unit 91 finds a position (reference position) where the first correlation output and the second correlation output simultaneously take a large value, and calculates the delay time Td of the superimposed signal based on the reference position. In order to find the reference position, for example, the sum of the first correlation output and the second correlation output is calculated for each position where the correlation is obtained, and the position when the sum is the largest may be obtained. For example, in FIGS. 2C and 2D, the sum of the peak value {circle around (1)} of the first correlator 70 and the peak value {circle around (2)} of the second correlator 80 is the largest. The position at the time when ▼ and 2 are obtained is the reference position. The delay time Td of the superimposed signal is obtained by subtracting the time at which the superimposed signal was transmitted from the time corresponding to the reference position. In the present embodiment, there is provided a counting means for counting the number of output pulse signals having the same cycle as the chip rate Tc since the transmission of the superimposed signal. Thus, assuming that the count value of the counting means at the time corresponding to the reference position is N, the delay time Td of the superimposed signal can be obtained by calculating N × Tc. As described above, the delay time calculation unit 91 calculates the delay time Td in units of the chip rate Tc. The delay time Td calculated by the delay time calculator 91 is a time from when the first pseudo random signal is transmitted on the transmitting side to a time corresponding to the reference position.
[0027]
The first correction time calculation unit 92 compares the peak value of the first correlation output with the peak value of the second correlation output at the reference position found by the delay time calculation unit 91, and based on the comparison result of the peak values, A first correction time Te for the time Td is obtained. In the present embodiment, the second pseudo-random signal is delayed by half the chip rate Tc from the first pseudo-random signal when generating the superimposed signal on the transmitting side. When it is a natural number multiple of Tc, one maximum peak value appears in the first correlation output, and two peak values appear in the second correlation output. At this time, the peak value output first among the two peak values in the second correlation output and the maximum peak value in the first correlation output appear at the reference position. When the delay time is (natural number + ／) times the chip rate Tc, two peak values appear in the first correlation output, and one maximum peak value appears in the second correlation output. At this time, the peak value output later of the two peak values in the first correlation output and the maximum peak value in the second correlation output appear at the reference position. Therefore, when comparing the peak value of the first correlation output with the peak value of the second correlation output at the reference position, if the peak value of the first correlation output is larger than the peak value of the second correlation output, the delay time of the received signal Is close to n times the chip rate Tc. On the other hand, if the peak value of the second correlation output is larger than the peak value of the first correlation output, it can be seen that the delay time of the received signal is close to (natural number +1/2) times the chip rate Tc.
[0028]
Specifically, the first correction time calculation unit 92 determines the first correction time Te for the delay time Td as follows. That is, when the peak value of the first correlation output is larger than the peak value of the second correlation output at the reference position, the first correction time Te is set to zero. If the peak value of the second correlation output is larger than the peak value of the first correlation output at the reference position, the second correction time Te is set to -Tc / 2. Here, the reason why “-” is added is that, in the present embodiment, the second pseudo-random signal is generated on the transmitting side later than the first pseudo-random signal by half the chip rate Tc. Because. As described above, in the first correction time calculation unit 92, the first correction time Te with respect to the delay time Td is obtained in a unit of half of the chip rate Tc. The delay time Td + Te obtained by the correction by the first correction time calculation unit 92 is the same as the pseudorandom signal input to the correlator in the correlator that outputs the two peak values. , And the time from when the two peak values are transmitted to the time corresponding to the intermediate position between the positions where the two peak values are output.
[0029]
The second correction time calculation unit 93 specifies the correlator with the smaller peak value at the reference position based on the comparison result of the peak values in the first correction time calculation unit 92, and in the specified correlator, Using the peak value at and the larger peak value of the peak values at the two positions adjacent to the reference position, calculate the position of the center of gravity with respect to the intermediate position of the position where these two peak values are taken, The second correction time Tf for the delay time Td is obtained based on the calculated position of the center of gravity.
[0030]
In the second correction time calculation section 93, further fine correction is performed on the delay time Td + Te obtained by the correction in the first correction time calculation section 92. Such correction is performed based on the two peak values in the correlator that outputs the two peak values. Therefore, the second correction time calculator 93 first specifies the correlator with the smaller peak value at the reference position, thereby specifying the correlator that outputs the two peak values. In the examples of FIGS. 2C and 2D, the second correlator 80 is specified by comparing the peak value (1) with the peak value (2). Once the correlator has been identified in this way, the two peak values at the identified correlator are then determined. As the two peak values, the peak value at the reference position and the larger one of the peak values at the two positions adjacent to the reference position may be used.
[0031]
The two peak values in the correlator specified in this manner are, in terms of the output characteristics of FIG. 3, the peak value output when the correlation position is in the range from -1 to 0, and the peak value output from the correlation position from 0 to +1. And a peak value output when the value is within the range. As shown in FIG. 3, in the range of the correlation position, the output of the correlator is symmetric with respect to the position having the maximum peak value (maximum peak position), and the correlation position is 0 except for the vicinity of the correlation position 0 and ± 1. The distance decreases substantially linearly as one moves away from ± 1. Therefore, if the position of the center of gravity with respect to the intermediate position between the correlation positions is obtained using the two peak values in the specified correlator, the position of the center of gravity can be considered to represent the maximum peak position.
[0032]
When two peak values are obtained in the correlator, the second correction time calculation unit 93 calculates the position of the center of gravity with respect to an intermediate position between the correlation positions using the two peak values. Assuming that the position G of the center of gravity is P1, the peak value output earlier is P1, and the peak value output later is P2.
G = {P1 × (− ／) + P2 × １ ／} / (P1 + P2)
Required by Then, by multiplying the obtained position G of the center of gravity by the chip rate Tc, a second correction time Tf = G × Tc is obtained. The second correction time Tf thus obtained is shorter than half the time of the chip rate Tc.
[0033]
The distance calculator 94 calculates the distance to the target based on the total delay time obtained by adding the delay time Td, the first correction time Te, and the second correction time Tf. Specifically, such a distance can be obtained by multiplying the entire delay time Td + Te + Tf by the propagation speed of the superimposed signal, and dividing the multiplied result by two.
[0034]
The present inventors have also verified the validity of obtaining the second correction time Tf based on the position of the center of gravity. Specifically, the simulation of the processing of the present apparatus was performed while variously changing the set value of the second correction time Tf. Then, in such a simulation, the position of the center of gravity was obtained, and the second correction time was calculated based on the position of the center of gravity. FIG. 4 shows the result of the simulation. In FIG. 4, the vertical axis represents the calculated value of the second correction time Tf obtained by calculating the position of the center of gravity, and the horizontal axis represents the set value of the second correction time Tf given in advance by the simulation. However, both the vertical and horizontal axes are expressed in units of the chip rate Tc. As shown in FIG. 4, the respective calculated values of the second correction time Tf are arranged on a straight line passing through the origin, and hardly deviate from a straight line A (ideal value) having a slope of 45 degrees passing through the origin. Therefore, it is considered that the distance to the target can be obtained with sufficiently satisfactory accuracy by using the second correction time Tf calculated based on the position of the center of gravity.
[0035]
Next, a processing procedure for measuring the distance to the target in the distance measuring device of the present embodiment will be described. FIG. 5 is a diagram for explaining a transmission signal. FIGS. 6, 7 and 8 are diagrams for explaining received signals. The waveforms of the respective signals shown in FIGS. 5 to 8 are obtained by the present inventors by performing a simulation on the processing of the present apparatus.
[0036]
When the operation of the distance measurement device starts, the first transmission-side PN signal generation unit 10 generates a first pseudo-random signal, and the second transmission-side PN signal generation unit 20 generates a second pseudo-random signal. The first pseudo-random signal is generated with a delay of half the chip rate Tc from the generation timing of the first pseudo-random signal. FIG. 5A shows an example of the waveform of the first pseudo-random signal generated by the first transmission-side PN signal generation unit 10, and FIG. 5B shows the second transmission-side PN signal generation unit. 2 shows an example of the waveform of a second pseudo-random signal generated at 20. In FIG. 5B, the second pseudo-random signal is delayed by half the chip rate Tc as compared to the first pseudo-random signal. The first pseudo-random signal and the second pseudo-random signal are sent to the adder 31. The adder 31 generates a superimposed signal (transmission signal) by superimposing the first pseudo random signal and the second pseudo random signal. The superimposed signal thus generated is transmitted from the transmission unit 32 to the target. FIG. 5C shows an example of a waveform of a superimposed signal obtained by superimposing the first pseudo random signal shown in FIG. 5A and the pseudo random signal shown in FIG. 5B. In each graph of FIG. 5, the vertical axis represents the signal amplitude. The horizontal axis indicates time, which is expressed in units of the chip rate Tc.
[0037]
The superimposed signal reflected back from the target is received by the receiver 41 as a received signal. FIG. 6A is an example of a waveform of a reception signal obtained when the superimposed signal shown in FIG. 5C is transmitted as a transmission signal when the delay time is a natural number multiple of the chip rate Tc. FIG. 7A shows a waveform of a reception signal obtained when the superimposed signal shown in FIG. 5C is transmitted as a transmission signal when the delay time is (natural number + ／) times the chip rate Tc. It is an example. FIG. 8A shows the reception signal obtained when the superimposed signal shown in FIG. 5C is transmitted as the transmission signal when the delay time is (natural number + ／) times the chip rate Tc. It is an example of a waveform. Here, in each of these figures, the analog waveform of the band-limited received signal is shown. In each figure, the vertical axis represents the amplitude of the signal, and the horizontal axis represents the time expressed in units of the chip rate Tc. As shown in FIGS. 6 (a), 7 (a), and 8 (a), the analog waveforms of the received signals received by the receiving unit 41 are all the same. Are shifted along the horizontal axis due to differences in delay time.
[0038]
The received signal received by the receiver 41 is sent to the A / D converter 42, and the A / D converter 42 samples the received signal at the same time interval as the chip rate Tc. 6, 7, and 8, (b) shows a waveform of a signal obtained by sampling the received signal of (a) for each chip rate Tc. In each of these figures, the vertical axis represents the amplitude of the signal, and the horizontal axis represents the time expressed in units of the chip rate Tc. As shown in FIGS. 6 (b), 7 (b) and 8 (b), the waveform of each signal obtained by sampling is different due to the difference in delay time.
[0039]
The received signal sampled by the A / D converter 42 is sent to the first correlator 70 and the second correlator 80. The first correlator 70 calculates the correlation between the received signal sampled by the A / D converter 42 and the first pseudo-random signal generated by the first receiving-side PN signal generator 50. On the other hand, the second correlator 80 calculates the correlation between the received signal sampled by the A / D converter 42 and the second pseudo-random signal generated by the second receiving-side PN signal generator 60. Here, the first pseudo-random signal sent to the first correlator 70 and the second pseudo-random signal sent to the second correlator 80 are generated at the same timing. 6, 7, and 8, (c) shows the waveform of the signal output from the first correlator 70, and (d) shows the waveform of the signal output from the second correlator 80. . In each of these figures, the vertical axis represents the amplitude of the signal, and the horizontal axis represents the correlation position, that is, the time represented by the chip rate Tc. In each of these figures, the waveform of the signal is drawn by a polygonal line by connecting the correlation values output from the correlator with a straight line.
[0040]
The correlation value obtained by the first correlator 70 and the correlation value obtained by the second correlator 80 are output to the delay time calculation unit 91 of the calculation unit 90. The delay time calculating unit 91 calculates the sum of the correlation value obtained by the first correlator 70 and the correlation value obtained by the second correlation value 80 at each correlation position, and determines the reference position at which the sum is the maximum. Find out. Then, based on the reference position, a delay time Td from transmission of the transmission signal to reception of the transmission signal is calculated in chip rate Tc units.
[0041]
In the case shown in FIGS. 6C and 6D, that is, when the delay time is a natural number multiple of the chip rate Tc, the first correlator 70 outputs one maximum peak value {circle around (1)}. The two correlators 80 output two peak values (2) and (3). Here, the two peak values (2) and (3) have substantially the same size, and the maximum peak value (1) in the first correlator 70 and the peak value (2) in the second correlator 80 appear at the same time. . In this example, the delay time calculation unit 91 obtains a position where the maximum peak value (1) and the peak value (2) appear as a reference position. 7 (c) and 7 (d), that is, when the delay time is (natural number + 1/2) times the chip rate Tc, the first correlator 70 outputs two peak values {2}. , {Circle around (3)}, and the second correlator 80 outputs one maximum peak value {circle around (1)}. Here, the two peak values (2) and (3) have substantially the same size, and the peak value (3) in the first correlator 70 and the maximum peak value (1) in the second correlator 80 appear at the same time. . In this example, the delay time calculation unit 91 obtains a position where the maximum peak value <1> and the peak value <3> appear as a reference position.
[0042]
As can be seen by comparing FIGS. 6C and 6D with FIGS. 7C and 7D, the case where the delay time is a natural number multiple of the chip rate Tc and the case where the delay time is the chip rate Tc In the case of (natural number +1/2) times, the peak value output from the first correlator 70 and the peak value output from the second correlator 80 are reversed.
[0043]
Furthermore, in the case shown in FIGS. 8C and 8D, that is, when the delay time is (natural number + ／) of the chip rate Tc, one peak value {circle around (2)} from the first correlator 70. Is output from the second correlator 80, and one peak value (1) is output. Here, these peak values (1) and (2) have substantially the same magnitude. In this example, the sum of the correlation values at the position where the peak value {1} is obtained is substantially the same as the sum of the correlation values at the position where the peak value {2} is obtained. In such a case, the delay time calculation unit 91 can determine any one of the position where the peak value {1} is obtained and the position where the peak value {2} is obtained as the reference position. Whichever position you choose as the reference position has no effect on the final result. Here, the position where the peak value (1) output from the second correlator 80 is taken is set as the reference position. In FIG. 8C, the output from the first correlator 70 at the reference position is a peak value (3).
[0044]
Next, the first correction time calculation unit 92 compares the peak value of the first correlator 70 with the peak value of the second correlator 80 at the reference position found by the delay time calculation unit 91, and based on the comparison result. Thus, the first correction time Te for the delay time Td is obtained in units of half the chip rate Tc. In the examples of FIGS. 6C and 6D, the peak value {circle around (1)} is compared with the peak value {circle around (2)}. Since it is larger than 2 ▼, the first correction time calculation unit 92 sets the first correction time Te to zero. 7C and 7D, the peak value {circle around (3)} is compared with the peak value {circle around (1)}, and the peak value {circle around (1)} of the second correlator 80 is the peak value of the first correlator 70. Since it is larger than the value (3), the first correction time Te is set to -Tc / 2. Further, also in the examples of FIGS. 8C and 8D, the first correction time Te is set to −Tc / 2 as in the cases of FIGS. 7C and 7D.
[0045]
Next, the second correction time calculation unit 93 specifies the correlator with the smaller peak value based on the comparison result of the peak values in the first correction time calculation unit 92. Then, in the specified correlator, using the peak value at the reference position and the larger peak value of the two peak values at the two positions adjacent to the reference position, the intermediate position between these two peak positions Is calculated, and a second correction time Tf for the delay time Td is calculated based on the calculated position of the center of gravity. In the examples of FIGS. 6C and 6D, the second correlator 80 is specified as the correlator having the smaller peak value at the reference position. Further, in the second correlator 80, the peak value output after the reference position as the larger peak value among the peak values at the two positions adjacent to the peak value at the reference position. Is chosen. Then, using the peak value (2) and the peak value (3), the position of the center of gravity with respect to the intermediate position between those peak positions is calculated. In the examples of FIGS. 7C and 7D, the first correlator 70 is specified as the correlator having the smaller peak value at the reference position. In the first correlator 70, the peak value {2} output earlier than the reference position is determined as the larger peak value of the peak values at the two positions adjacent to the peak value {3} at the reference position. ▼ is selected. Then, using the peak value (2) and the peak value (3), the position of the center of gravity with respect to the intermediate position between those peak positions is calculated. Further, in the examples of FIGS. 8 (c) and 8 (d), similarly to the cases of FIGS. 7 (c) and 7 (d), the peak positions are used by using the peak values [2] and [3]. The position of the center of gravity with respect to the intermediate position is calculated.
[0046]
Thereafter, the distance calculation unit 94 multiplies the total delay time Td + Te + Tf obtained by adding the delay time Td, the first correction time Te, and the second correction time Tf by the signal propagation speed. Then, the distance to the target is obtained by dividing the obtained result by two.
[0047]
In the distance measuring device of the present embodiment, on the transmitting side, the first pseudo-random signal is generated, and the first pseudo-random signal has the same chip rate as the first pseudo-random signal and has a low correlation with the first pseudo-random signal. The second pseudo-random signal is generated with a delay of half the chip rate from the generation timing of the first pseudo-random signal, and is obtained by superimposing the first pseudo-random signal and the second pseudo-random signal. The superimposed signal is transmitted to the target. On the receiving side, after sampling the received signal at the same time interval as the chip rate, the first correlator calculates the correlation between the received signal and the first pseudo-random signal, and the second correlator compares the received signal with the received signal. A correlation with the second pseudo-random signal is calculated, and a distance to the target is calculated based on the correlation value output from the first correlator and the correlation value output from the second correlator. Specifically, by using one peak value output from one of the first correlator and the second correlator and two peak values output from the other one complementarily, With a simple configuration, the distance to the target can be calculated with a resolution equal to or less than the chip rate.
[0048]
Note that the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist.
[0049]
【The invention's effect】
As described above, according to the distance measuring apparatus of the present invention, the transmitting side generates the first pseudo-random signal, has the same chip rate as the first pseudo-random signal, and has the first pseudo-random signal. A second pseudo-random signal having a low correlation with the signal is generated with a delay of half the chip rate from the generation timing of the first pseudo-random signal, and the first pseudo-random signal and the second pseudo-random signal are generated. A superimposed signal obtained by superimposing the signal is transmitted to the target. On the receiving side, after sampling the received signal at the same time interval as the chip rate, the first correlation calculating means calculates the correlation between the received signal and the first pseudo-random signal, and the second correlation calculating means calculates the received signal. A correlation between the signal and the second pseudo-random signal is calculated, and a distance to the target is calculated based on the correlation value output from the first correlation calculation means and the correlation value output from the second correlation calculation means. Specifically, one peak value output from one of the first correlation calculation means and the second correlation calculation means and two peak values output from the other one are used complementarily. Accordingly, with a simple configuration, the distance to the target can be calculated with a resolution equal to or less than the chip rate.
[0050]
Further, according to the distance measuring method of the present invention, similarly to the above, the distance to the target can be calculated with a simple configuration and a resolution equal to or less than the chip rate.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of a distance measuring device according to an embodiment of the present invention.
FIG. 2 is a diagram for explaining signals output from each unit of the distance measuring device.
FIG. 3 is a diagram for explaining output characteristics of a correlator used in the distance measuring device.
FIG. 4 is a diagram showing the results of a simulation performed to verify the validity of obtaining a second correction time based on the position of the center of gravity.
FIG. 5 is a diagram for explaining a transmission signal.
FIG. 6 is a diagram for explaining a received signal.
FIG. 7 is a diagram for explaining a received signal.
FIG. 8 is a diagram for explaining a received signal.
[Explanation of symbols]
10 First transmitting PN signal generator
20 Second transmitting side PN signal generator
30 Transmission processing unit
31 Adder
32 transmission unit
40 reception processing unit
41 Receiver
42 A / D converter
50 first receiving-side PN signal generator
60 second receiver PN signal generator
70 First correlator
80 Second correlator
90 Operation unit
91 Delay time calculator
92 First correction time calculator
93 Second correction time calculator
94 Distance calculator

Claims (4)

A first transmitting-side signal generating means for generating a first pseudo-random signal provided on the transmitting side,
A second pseudo-random signal having the same chip rate as that of the first pseudo-random signal and having a low correlation with the first pseudo-random signal, provided on the transmission side; A second transmission-side signal generation means that is generated with a delay of half the chip rate from the generation timing of the first pseudo-random signal according to
A superimposed signal is generated by superimposing the first pseudo-random signal generated by the first transmission-side signal generation unit and the second pseudo-random signal generated by the second transmission-side signal generation unit. , Transmission processing means for transmitting to the target,
Receiving processing means for receiving the superimposed signal reflected back from the target and sampling the received signal at the same time interval as the chip rate,
A first receiving-side signal generating means for generating the first pseudo-random signal provided on the receiving side,
Provided on the receiving side, the second pseudo-random signal, the second receiving-side signal generating means to generate simultaneously with the generation timing of the first pseudo-random signal by the first receiving-side signal generating means,
A first correlation calculation unit that calculates a correlation between the reception signal sampled by the reception processing unit and the first pseudo-random signal generated by the first reception-side signal generation unit,
A second correlation calculation unit that calculates a correlation between the reception signal sampled by the reception processing unit and the second pseudo-random signal generated by the second reception-side signal generation unit,
An arithmetic unit that calculates a distance to the target based on the correlation value output from the first correlation calculation unit and the correlation value output from the second correlation calculation unit,
A distance measuring device comprising: The calculating means includes:
At each correlation position, the sum of the correlation value output from the first correlation calculation means and the correlation value output from the second correlation calculation means is determined, and the position where the sum is maximum is found as a reference position, A delay time calculating unit that calculates a delay time from when the superimposed signal is transmitted to when it is received based on the position in the same time unit as the chip rate,
At the reference position found by the delay time calculating means, the correlation value output from the first correlation calculating means is compared with the correlation value output from the second correlation calculating means, and the comparison result of the two correlation values is compared. First correction time calculation means for obtaining a first correction time for the delay time based on the time unit of half of the chip rate,
A correlation value having a smaller correlation value is specified based on a comparison result in the first correction time calculation means, and the specified correlation calculation means includes a correlation value at the reference position and two correlation values adjacent to the reference position. Using the larger correlation value among the correlation values at the correlation position, the position of the center of gravity with respect to the intermediate position between the correlation positions taking the two correlation values is calculated, and the delay time is calculated based on the calculated position of the center of gravity. Second correction time calculation means for obtaining a second correction time for
The delay time, a distance calculation unit that calculates a distance to the target based on a time obtained by adding the first correction time and the second correction time,
The distance measuring device according to claim 1, further comprising: On the transmitting side, while generating a first pseudo-random signal, the second pseudo-random signal having the same chip rate as the first pseudo-random signal and having a low correlation with the first pseudo-random signal, A first step of generating the first pseudo-random signal with a delay of half the chip rate from the generation timing of the first pseudo-random signal,
A second step of generating a superimposed signal by superimposing the first pseudo-random signal and the second pseudo-random signal generated in the first step, and transmitting to the target,
A third step of receiving the superimposed signal reflected back from the target and sampling the received signal at the same time interval as the chip rate;
On the receiving side, the first pseudo-random signal is generated, and the second pseudo-random signal is generated at the same time as the generation timing of the first pseudo-random signal.
A fifth step of calculating a correlation between the received signal sampled in the third step and the first pseudo-random signal generated in the fourth step,
A sixth step of calculating a correlation between the received signal sampled in the third step and the second pseudo-random signal generated in the fourth step,
A seventh step of calculating a distance to the target based on the correlation value obtained in the fifth step and the correlation value obtained in the sixth step,
A distance measuring method, comprising: The seventh step is
At each correlation position, a sum of the correlation value obtained in the fifth step and the correlation value obtained in the sixth step is obtained, a position where the sum is maximum is found as a reference position, and the superimposition signal is obtained based on the reference position. Calculating the delay time from the transmission to the reception in the same time unit as the chip rate,
The correlation value obtained in the fifth step and the correlation value obtained in the sixth step are compared at the reference position, and a first correction time for the delay time is set based on a comparison result of the two correlation values. A step in which the time is calculated in units of half the chip rate;
A correlation output having a smaller correlation value is specified based on a comparison result of the two correlation values, and in the specified correlation output, a correlation value at the reference position and two correlation positions adjacent to the reference position are calculated. Using the larger correlation value of the correlation values, the position of the center of gravity with respect to the intermediate position between the correlation positions taking the two correlation values is calculated, and the second position with respect to the delay time is calculated based on the calculated position of the center of gravity. Determining a correction time;
Obtaining the distance to the target based on the delay time, the first correction time and the time obtained by adding the second correction time,
The distance measuring method according to claim 3, further comprising:

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