JPS6134104B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a distance detection method for distance measurement using a PN code, and more specifically, the present invention relates to a distance detection method for distance measurement using a PN code.
The present invention relates to a distance detection method suitable for measuring the distance to a target by detecting a correlation between a received code string and a transmitted code string by reflecting the transmitted code back to the target. When measuring the distance between a satellite and a ground station using a PN code (Pseudo-random noise code), several types of PN code strings are combined on the upper side and sent to the satellite with a certain clock synchronization, and the PN combination code for the satellite return is transmitted. A method is adopted in which the phase delay from the time of transmission is detected for each PN code string. A conventional method of this type is shown and explained in Fig. 1.
In the figure, 1 is a received code string, 2 is a local code string generator, and 3 is a correlation detection that takes as input the code string from the received code string 1 and the code string from the local code string generator 2, and synchronizes the phase of both. In a vessel,
It has a function to detect the maximum correlation and also output the received code string at that time. 4 is a local code string register that stores a local code string that is synchronized with the received code string that inputs the output of the correlation detector 3; 5 is a transmitting PN code generator; and 6 is the output of the local code string register 4 and the transmitting PN code. A matching circuit matches the output of the generator 5, a counter circuit 7 counts the output of the matching circuit 6, and a receiving code clock 8 is synchronized in advance. In the distance measurement method configured in this way,
First, phase synchronization is performed in the correlation detector 3 with each PN code string locally generated by the local code string generator 2 in synchronization with the received code clock 8 with respect to the received code string 1 of the received combination PN code. The synchronized local PN code string is recorded in the local code string register 4. next,
After synchronization is completed for each PN code string, the match circuit 6 detects a match between the contents of the local code string register 4 and the PN code from the transmitting PN code generator 5, and at the same time outputs the match output. Counter circuit 7 by
make it work. Then, by counting each code string in the counter circuit 7 until all matching moments detected by a separate circuit with the same configuration become the same, the count contents of the counter circuit 7 can be transmitted and
The data corresponds to the delay time between receptions. Here, one PN code string is expressed as follows. 11100101110010... In other words, in this example, the code is repeated by 1110010. Considering the correlation between this PN code string and a PN code string that has the same configuration but has a temporal deviation, correlation means that a specific number of bits is targeted. In this code example, the difference between the number of matches and the number of mismatches is divided by the specific number of bits.
If the correlation value when the PN code strings match in time becomes mismatched by 1.1 bit or more,
If the number of correlated bits is large, the correlation value will always be -1/
It becomes 7. Therefore, using this property, the received
A local PN code string that matches the PN code string in time can be reproduced from a received signal via a noisy signal path, and this can be used to determine the delay time of the received code string with respect to the transmitted code string. can. FIG. 2 is a block diagram showing details of the correlation detector 3, in which a counter 31 counts received code clocks 8 separately extracted from the received code string 1, and calculates the number of bits according to the number of bits of the code constituting the repeated code string 1. When the clock 8 is counted, a count-up output is sent out, and the clock 8 is also provided to the local code string generator 2 via the gate circuit 32, and in response, the above-mentioned output is sent. The generator 2 generates a code string consisting of codes and supplies it to a phase comparator 33. The comparator 33 compares the phases of the received code string 1 and the local code string, thereby determining the bit difference between the two code strings, and provides a comparison inverted output corresponding to this to the integrator 34. The integral value corresponding to the bit difference integrated by the circuit 34 is stored in the memory 35.
The integrator 34 is stored by the counter 31
The count-up output from the memory 35 is applied to the reset input R, which resets the memory 35.
ST, and in order to store the integral value, the integral value is updated and stored in the memory 35 for each series of codes, and this is compared with the current integral value by the comparator 36. The comparator 3 stores the larger value in the memory 35.
6 gives a command signal to the strobe input ST of the memory 35, and by doing this every time each code is repeated as code string 1, the memory 35 stores the integrated value of the comparison inversion output of the phase comparator 33. The maximum value of is stored. On the other hand, the code string from the local code string generator 2 is also given to the register 37, and is input to the counter 31.
The control circuit 38 determines the code that has the largest integral value based on the count-up output and the output of the comparator 36, and selectively designates this code. , send control signal to send out command input SD
This causes a series of bits constituting the code having the maximum integral value to be sent to the local code string register 4 in FIG. Note that the count-up output of the counter 31 is
It is applied to the inhibit input INH of the gate circuit 32, and the clock 8 is blocked one pulse at a time for each code and is applied to the local code string generator 2. Therefore, the local code string is input to the local code string generator 2 for each code. The phase is shifted one bit at a time, and codes with successive phase shifts are generated, which are successively compared in the phase comparator 33, and by the action of the integrator 34 to the control circuit 38,
The code of the local code string that most closely matches the phase of code string 1 and has the maximum mutual correlation value is sent out from the register 37. Therefore, the coincidence moment for each of the transmission code and the synchronization local code occurs every code period, but if you take the moment when all the code strings coincide, it is possible to eliminate the ambiguity of the cycle, while By using transmission code strings of It is possible to reliably detect a time delay between transmission and reception up to a period corresponding to the product of the numbers. Note that distance calculation methods that use PN code strings are described, for example, in the document "Digital Communication" by Solomon Golomb.
It is introduced in detail in Chapter 6 (Applications to Ranging) of the author, Premptice Hall, 1964). However, this method has the inconvenience of having to wait for the sequential shift time of the transmitted code sequence to calculate the distance until the local code synchronized with the received code matches the transmitted code. The drawback was that it was time consuming. Also, for each code string,
A matching detection circuit consisting of a local code string register 4, a transmitting PN code generator 5, and a matching circuit 6, and a counter circuit for counting delay time are required. This has resulted in the drawback that the configuration of the device is complicated and uneconomical. In view of the above points, the present invention has been made to solve such problems, and its purpose is to detect the correlation between a received code string and a local code string.
By simultaneously detecting the phase delay data between the local code string and the transmitted code string, which have the maximum correlation, we provide a distance detection method that eliminates the coincidence counter circuit for distance detection described above and shortens the distance detection time. It's about doing. In order to achieve such an objective, the present invention
A distance measurement method that measures the distance to the target object by transmitting a transmission code string using a PN code and detecting a correlation between the received code string and the transmission code string by returning the transmission code string to the target object. means for generating the transmission code string; a local code string generator inputting the transmission code string obtained by the means; and a local code string from the local code string generator and the received code string. means for performing the correlation detection by phase comparison with the local code sequence and integration of the comparison output; means for counting phase delay data of the local code forming the local code sequence from the transmission code forming the transmission code sequence; means for storing a correlation detection value obtained by correlation detection and phase delay data, and causes the local code string generator to generate the local code by successively changing the phase delay from the transmission code, thereby configuring the PN code. The correlation detection is performed on all the code strings that exist for the same number of bits, and the correlation detection value having a large value during this period and the phase delay data corresponding thereto are sequentially updated and stored in the storage means, and the correlation detection After the completion of the step, only the phase delay data corresponding to the maximum correlation detection value is outputted from the storage means, and this output is used as distance data, and the first invention is characterized in that the distance data is composed of a number of bits each having a relation of prime numbers to each other. different from each other
By transmitting a plurality of transmission code strings using PN codes, and detecting the correlation between each received code string and the corresponding transmission code string by repeating the target object of each transmission code string, the target object is detected. In a distance measurement method for measuring the distance between the two transmitting codes, the distance measuring method includes a means for individually generating each transmitting code string, and a local means for generating each transmitting code string by inputting each transmitting code string obtained by this means. a code string generator; means for individually performing the correlation detection by comparing the phases of each local code string from the local code string generator with the corresponding received code string; and integrating the comparison output; means for individually counting phase lag data of local codes constituting the corresponding local code sequence from each transmitted code constituting the sequence; and means for counting the correlation detected value and phase lag data by the correlation detection for each received code sequence means for storing a corresponding local code by the local code string generator by changing the phase delay from each of the transmission codes one after another, The correlation detection is performed for each of the received code strings for all of the code strings, and the correlation detection value having a large value during this period and the phase delay data corresponding thereto are sequentially updated by the storage means for each of the received code strings. After the correlation detection is completed, the storage means outputs only the phase delay data corresponding to the maximum correlation detection value for each received code string, and distance data is determined based on these phase delay data. This is a second invention, and embodiments of the invention will be described in detail below with reference to the drawings. FIG. 3 is a block diagram for explaining one embodiment of the present invention. In the figure, 11 is a transmitting code string generator, 12 is a receiving local code generation register (local code string generator) which inputs the transmitting code string from the transmitting code string generator 11, 13 is a receiving code string, and 14 is a receiving code string. A phase comparator 15 compares the phase of the code string 13 and a local code string from the local code string generator 12, and 15 is an integrator that integrates the inverted output of the phase comparator 14. The counter circuit 17 is configured to be reset by the output of the counter circuit 17. 16 is a clock signal synchronized with the receiving clock;
17 is a first counter circuit that counts the clock signal 16; 18 is a second counter circuit that counts a carry signal when the first counter circuit 17 counts up; 19 is a counter circuit that counts the clock signal 16 and the first counter circuit; This suppressing circuit receives the output of the suppressing circuit 17 as an input, and is configured to delay and control the output phase from the local code string generator 12 using the output of the suppressing circuit 19. A register circuit 20 includes two registers that store the outputs of the first and second counter circuits 17 and 18 and the output of the comparator 21. Here, the comparator 21 has a function of comparing the output of the integrator 15 and the output of the register circuit 20 that stores phase delay data of the local code from the transmission code. Note that N ₁ is the count content from the second counter circuit 18. Note that the details of the integrator 15, register circuit 20, comparator 21, etc. are the same as those of the integrator 34 to the control circuit 38 in FIG. Next, the operation of the embodiment shown in FIG. 3 will be explained. First, in order to explain an embodiment, distance measurement will be explained in order to facilitate understanding of the present invention.Distance measurement begins with synchronization on the transmission side of a clock that determines transmission timing. Correlation detection of each PN code string is performed by setting the transmitting code string from the transmitting code string generator 11 into the receiving local code generation register (local code string generator) 12 at the timing of the clock signal 16 synchronized with the receiving clock. It starts with that. However, in this case, it is assumed that the integrator 15 has been reset and the first and second counter circuits 17 and 19 have been reset to zero. Now, under these conditions, the clock signal 16 synchronized with the reception clock is sent to the local code string generator 12 via the inhibit circuit 19 to generate a local code string. This local code string is phase-compared with the received code string 13 by a phase comparator 14, and the compared and inverted output is integrated by an integrator 15. For example, one code is averaged to indicate a correlation value, and the register circuit 20 is stored. In this case, the phase comparison between the received code string 13 and the local code string from the local code string generator 12 is performed until the first counter circuit 17 counts up, and the time until this count up is equal to the number of code constituent bits. It can be determined from the correlation detection error rate. The carry signal (carry) at the time of count-up of the first counter circuit 17 is not only counted by the second counter circuit 18, but also used for a reset command of the integrator 15. 16 is erased by the inhibit circuit 19 for only one clock.
This corresponds to delaying the local code string from the local code string generator 12 by one clock compared to the previous one, and if the phase comparison between the local code string and the received code string is performed in this state, it will differ from the previous one by one clock.
It is possible to perform a phase comparison that is different (delayed) by the reception clock. However, in this case, it is necessary to reset the integrator 15 and store the correlation value by the register circuit 20 before performing the second phase comparison for each reception. At this time, the register circuit 20
The second counter circuit 1 stores the integrated value indicating the correlation value from the integrator 15 and simultaneously the phase delay data of the local code with respect to the transmitted code.
It is important to the present invention that the count contents of 8 are also stored at the same time. That is, the data stored in the register circuit 20 first includes the integral value and the zero count of the second counter circuit 18 in the first phase comparison. In other words, the local code string has the same phase relationship as the transmitted code string. Next, in the next phase comparison, the comparator 21 compares the second integral value with the first integral value, and if the second integral value is larger, the second integral value and the second integral value are compared. 18 counts 1 are stored in the register circuit 20. Here, a count of 1 indicates that the local code string lags behind the transmitted code string by one clock. Of course, if the integral data of the cut is larger, the contents of the register 20 after the second phase comparison are the same as those of the first time. By repeating this operation, for each PN code string, all code strings as many as the number of code constituent bits are sequentially generated in the local code string generator 12, and the phase of the received code string and each local code string is adjusted for each code. The code string with the maximum integral value, that is, the code string with the best correlation, is selected as the local code string that is in phase with the received code string. However, in this case, instead of finding a local code string that is in phase with the received code string and then newly detecting the phase difference between this local code string and the transmitted code string, this phase difference has already been detected at the time of correlation detection. The main focus of the present invention is simultaneous detection. That is, the phase difference between the local code string that is in phase with the received code string and the received code string is stored in the register circuit 20 as the content from the second counter circuit 18, for example _N1 , and is stored in the register after all correlation detection is completed. Circuit 20 to N ₁
By outputting only the received code string, it can be determined that the received code string 13 lags behind the transmitted code string by _N1 clocks. However, the content from the second counter circuit 18
Since N ₁ is less than or equal to the number of bits constituting the code string,
To detect a phase delay beyond that, it is necessary to use a plurality of PN code strings having different configurations in combination. For this detection, for example, three PN code strings a, b, c (a, b, c
(consisting of bits that have a mutually prime number relationship and using mutually different PN codes), the time delay between transmission and reception due to the combination is R clocks, and the number of bits in each code is A,
When B and C are assumed, the following relationship holds: R=N ₁ +At ₁ =N ₂ +Bt ₂ =N ₃ +Ct ₃ A・B・C ……(1). Here, N ₁ , N ₂ , and N ₃ are outputs obtained by performing correlation detection according to the present invention on each code string a, b, and c, and t ₁ , t ₂ , and t ₃ are not determined by each code string alone. It is assumed to be the period. Therefore, the phase delay between transmitting and receiving can be detected by determining the periodic components t ₁ , t ₂ , and t ₃ from the above equation (1) and deriving the clock component R. Here, above (1)
The formula can be instantaneously solved by a computer or the output N ₁ ,
If necessary, use the combination of N ₂ and N ₃ as data (1)
It is also possible to solve the equation. FIG. 4 is a block diagram showing the entire configuration when three types of code strings are used. Received code string 1 is distributed by a multiplexer 41 to code strings having individual configurations, and the structure of FIG. Based on the output data N ₁ to _{N 3} sequentially provided to each of the correlation detection units 42 to 44 and sent to each of them, the electronic computer 45 performs the arithmetic processing of equation (1), and output data N ₁ to _{N 3} The distance data R is calculated based on the following. Here, the method of calculation using equation (1) is specifically shown as follows. That is, taking code strings a and b as an example, let us assume that the code for a is made up of 3 bits and the code for b is made up of 4 bits, each of which consists of bits that have a prime number relationship with each other, and When a and b use different PN codes,
As shown in Figure 5, the timing of each bit is determined by the cycles 1 to 12 of the common clock CLK.
The relative relationship between a and b changes as the distance to the target changes. However, if A and B are the number of bits of each code, then A=3 and B=4, and naturally N ₁ <A, N ₂
Since the relationship ＜B, R(A・B) holds true,
While N ₁ is determined in the range of 0 to 2 and N ₂ is determined in the range of 0 to 3, the number of cycles t ₁ and t ₂ of each code string shown as 0 to 3 in FIG. If we calculate the number of cycles with matching end points, 12 combinations will occur, as shown in the table below, and R will be determined accordingly.

[Table] Therefore, when using the code strings a, b, and c, a table similar to the previous table can be created on the computer 45.
By storing the distance data in the memory of , and performing the arithmetic processing of equation (1) using this, the distance data R can be immediately obtained based on the output data N ₁ to _{N 3} . Note that the clock component R does not include the phase delay less than the clock cycle and the dynamic position delay between the satellite and the ground, so at the start of correlation detection for each code string,
The clock fluctuation from the moment the transmission code is set in the local code string must be corrected to the clock R as a precise distance. In this way, not only when using a single code string, but also when using multiple code strings, the more combinations of codes there are, the more registers and matching circuits can be prevented from increasing in proportion to the bit configuration of the code. By simply installing a circuit that counts and stores the phase delay data from the transmission code,
It is extremely effective because distance data can be detected at the same time as correlation detection. As is clear from the above description, according to the present invention, distance can be detected with a simple configuration without using complicated means, and there is a phase lag between a synchronized local code string and a transmitted code string. Since data is also detected at the same time, the distance detection time is shortened compared to conventional methods of this type, and the practical effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining an example of a conventional distance measurement method, FIG. 2 is a block diagram showing details of FIG. 1, and FIG. 3 is for explaining an embodiment of a distance calculation method according to the present invention. FIG. 4 is a block diagram showing the entire configuration when three types of code strings are used, and FIG. 5 is a diagram showing a plurality of PN code strings. 11... Transmission code string generator, 12... Local code string generator, 13... Reception code string, 14
... Phase comparator, 15 ... Integrator, 16 ... Clock signal, 17, 18 ... Counter circuit, 19 ...
...Inhibition circuit, 20...Register circuit, 21...Comparator.

Claims (1)

[Claims] 1. Transmitting a transmission code string using a PN code,
In a distance measurement method that measures the distance to the target by detecting a correlation between the received code string and the transmitted code string by returning the transmitted code string to the target, means for generating the transmitted code string; , a local code string generator inputs the transmitted code string obtained by this means, phase comparison between the local code string from this local code string generator and the received code string, and integration of this comparison output. means for performing the correlation detection; means for counting phase lag data of local codes constituting the local code sequence from transmission codes constituting the transmission code sequence; storing means, for causing the local code string generator to generate the local code by successively changing the phase delay from the transmission code, and for all code strings that exist as many as the number of bits constituting the PN code. The correlation detection is performed, and the correlation detection value having a large value during this period and the phase delay data corresponding thereto are sequentially updated and stored in the storage means, and after the completion of the correlation detection, the maximum correlation detection value is stored in the storage means. A distance detection method characterized in that only the phase delay data corresponding to the phase delay data is outputted, and this output is used as distance data. 2. Transmit a plurality of transmission code strings, each consisting of bits of numbers having a relation of prime numbers to each other and using mutually different PN codes, and correspond to each reception code string by returning each transmission code string to a target object. In the distance measurement method of measuring the distance to the target object by individually detecting the correlation between the transmission code strings, there is provided a means for individually generating each transmission code string; A local code string generator receives each transmitted code string as input and generates a corresponding local code string, and a phase comparison between each local code string from this local code string generator and the corresponding received code string is performed. means for individually performing the correlation detection by integrating the comparison output; and means for individually counting phase delay data of local codes constituting the local code sequence corresponding to each transmission code constituting the respective transmission code sequence. , means for storing correlation detection values and phase delay data obtained by the correlation detection for each of the received code strings, and means for sequentially changing the phase delay from each of the transmission codes to generate the corresponding local data by the local code string generator. The code is generated individually, and the correlation detection is performed for each received code string for all the code strings that exist as many as the number of bits constituting the PN code. The phase lag data is sequentially updated by the storage means and stored for each received code string, and after the correlation detection is completed, the phase lag data corresponding to the maximum correlation detected value for each received code string is stored in the storage means. A distance detection method characterized by outputting only data to each individual and calculating distance data based on each phase delay data.