JP2008020221A - Spectrum diffusion type radar device, and pseudo noise code generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems wherein, when using an M-series code, since kinds of the code are few and application of each different code to each radar device is difficult, thereby there is strong possibility of receiving interference from a radar device of the same kind, and when using a Gold-series code, since characteristics of autocorrelation and mutual correlation are deteriorated furthermore than the M-series code, though the kinds are increased, the performance of the radar device is lowered. <P>SOLUTION: In this radar device, a spectrum diffusion system is used, which is constituted of a code generator 10 for transmission, a code generator 20 for reception for generating a code wherein a time is delayed furthermore than a code for transmission, a diffusion modulator 11 for performing diffusion modulation of a signal wave with the code for transmission, a transmission means 12 for transmitting a signal subjected to the diffusion modulation, a reception means 21 for receiving the signal, and a diffusion demodulator 22 for demodulating a received signal by the code for reception. The radar device having excellent safety can be provided, wherein misidentification is hardly generated, even when each code having few kinds is assigned to each radar device by outputting a pseudo noise code with each different phase to each radar device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radar apparatus using a spread spectrum system, and more particularly to a radar apparatus that is not easily misidentified and excellent in safety.

  A spread spectrum (SS) system (hereinafter referred to as a DS-SS system) using a direct sequence (DS) system that modulates a carrier wave with a spreading code transmits a radar signal from itself. And the distance with a target object is measured by receiving the reflected wave from the target object which exists ahead.

  This DS-SS method modulates (spreads) a narrowband signal into a wideband signal using a spreading code and transmits it. On the receiving side, the same spreading code as the transmitting side is used. This is a method for restoring to a signal. To restore the radar signal, the reception side uses the time delayed code to perform a correlation operation (despreading operation) on the received signal, and the delay time of the code is the propagation time of the radar signal (after transmitting the radar signal). The radar signal is restored when it is reflected by the object and coincides with the time until the reflected wave is received (hereinafter referred to as synchronization).

  The DS-SS method is superior in interference resistance and confidentiality because the influence of noise mixed during propagation is spread during despreading, but its performance is greatly affected by the spreading code used. The The spreading code required in the DS-SS system can suppress interference with signals from similar radar devices (good cross-correlation characteristics) and can suppress interference with its own signals (good auto-correlation characteristics) ). As such a spreading code, a pseudo noise (PN) code having a common rule for both transmission and reception is generally used, and typical codes include an M sequence code and a Gold sequence code. The M-sequence code has a simple generation method and the extracted code sequence has properties close to true random numbers. Therefore, the auto-correlation and cross-correlation characteristics are excellent, and the characteristics of the codes used for radar are optimal. .

  However, even if an M-sequence code having excellent autocorrelation and cross-correlation characteristics is used, if there are a plurality of similar radar devices in a predetermined range and the same M-sequence code is used in each radar device, the obstacle is There is a risk of detecting radar signals even though they do not exist.

  FIG. 9 is a diagram illustrating a state in which the radar device A61 receives a radar signal (detection signal) reflected from the object 63 and a state in which a radar signal (interference wave) radiated from the same type radar device B62 is received. FIG. 10 is a graph showing the detection signal and interference wave received by the radar device A61 with respect to the distance.

  That is, in the situation shown in FIG. 9, when the same type of radar apparatus uses the same code, the phase of the reception side code used for the correlation operation during the scan and the detection signal radiated from the other radar apparatus (radar apparatus B62) received. As shown in FIG. 10, an interference wave is observed at a distance different from the detection signal of the object 63 (hereinafter referred to as misidentification). Since this interference wave, that is, the misrecognized signal is determined by the code phase of the radar apparatus B62, the distance from the radar apparatus A61 to the radar apparatus B62 is greater than the distance from the radar apparatus A61 to the object 63, as shown in FIG. Even if the positional relationship is far away, the misidentification signal from the radar device B62 may be observed at a shorter distance than the detection signal from the object 63.

  In order to explain the cause of this misidentification, first (1) the radar detection principle will be explained, and then (2) the cause of misidentification will be described. In order to simplify the description, the description will be made using a code with a period of 1000 bits and a code value appropriately assigned from 1 to 1000, instead of representing a code value as a binary value. Here, it is assumed that scanning is performed with a scanning range of 100 m and a resolution of 1 m as radar operating conditions.

  FIG. 11 is a diagram illustrating a state (phase) of codes used in the radar device A61 and the radar device B62 in the situation of FIG.

  11A shows the code used on the transmission side in the radar apparatus A61, the code in FIG. 11B shows the reception code of the signal reflected from the object 63 in FIG. 9, and FIGS. f) shows the correlation code (despreading code) of the radar device A61, and FIG. 11 (g) shows the transmission code of the radar device B62.

(1) Radar detection principle As shown in FIGS. 11 (a) and 11 (b), there is a time difference between the transmission signal and the reception signal, and the distance is calculated by obtaining this time difference. This is the principle of radar. Specifically, on the receiving side, a correlation operation (despreading operation) between the code delayed in time with respect to the code on the transmitting side and the received signal is performed, and the distance is calculated from the synchronized delay time. This time, for the sake of explanation, the scan range is set to 100 m and the resolution is set to 1 m. Therefore, in order to cover the scan range of 100 m, it is necessary to delay by 1 to 100 bits. After a delay of 100 bits, the process returns to the beginning and the correlation operation is performed again. The state of the time-delayed code used in this reception side correlation is shown in FIGS. FIG. 11C shows a code delayed by 1 bit. After that, the code is delayed bit by bit, and after 100-bit delay (FIG. 11E), the initial state of the correlation operation (despreading operation) again (FIG. 11C). ) Is scanned. As an initial state of the correlation operation, the code state shown in FIG. 11A without delay may be used as the reception code. Here, FIGS. 11 (b) and 11 (d) have the same amount of time delay (phase). That is, when the code of the received signal and the correlation code are synchronized, as shown in FIG. 10, the radar signal (detection signal) from the object 63 is output at a distance corresponding to the delay time.

(2) Cause of misidentification As shown in FIG. 9, when the transmission signal of the same type of radar device B62 using the same reference numeral as that of the radar device A61 is received in the state of FIG. As shown in FIG. 11 (f), consider a case where the correlation code of the radar device A61 is synchronized with the code of FIG. 11 (g). In this case, a radar signal (misidentification signal) as shown in FIG. 10 is observed at a distance corresponding to the delay time of the correlation code. For this reason, it misidentifies as if another target 63 exists. This is a cause of misunderstanding. Further, when the code phase of the radar apparatus B62 shown in FIG. 11 (g) changes, the misidentification signal is displayed at different distances accordingly. That is, in FIG. 10, a misidentification signal is observed farther than the detection signal, but when the signal of the radar device B62 is received in a state as shown in FIG. 11 (c), the misidentification signal is closer to the detection signal. Is observed.

  In order to avoid the above-described misidentification, it is desirable that the pseudo-noise code used in the radar apparatus can be changed to an arbitrary code. As a prior art for avoiding this misidentification, for example, there is one disclosed in Patent Document 1.

  FIG. 12 is a block diagram showing a configuration of an in-vehicle radar device capable of avoiding misidentification caused by the same type of radar device disclosed in Patent Document 1, and includes an autocorrelator on the receiver side, and before the radar signal is transmitted. Based on the reception output of the receiver, it is determined whether or not the spread code scheduled to be used is used.

  Interference can be avoided because the radar detection operation is performed after confirming that the spreading code is unused. For this reason, misidentification can be avoided by assigning several types of M-sequence codes to each radar device.

  However, the types of M-sequence codes are limited, and it is difficult to allocate an M-sequence code for each radar device. This is because the M-sequence code generator using the shift register shown in FIG. 13 uses a circuit composed of a shift register of an appropriate length, and excludes the logical value of the final stage and the logical value of the intermediate stage. The PN code is generated while inputting the logical OR (EX-OR) in the first stage, but the position where the EX-OR in the middle stage is inserted (hereinafter referred to as the tap position) cannot be set to an arbitrary position. In order to generate an M-sequence code, the tap position needs to be inserted according to a primitive polynomial, so the type is limited.

  The primitive polynomial that determines the tap position of the M-sequence code is described in Non-Patent Document 1, and even when 10 stages of shift registers are used, there are only 60 types, and it is difficult to assign the M-sequence code to each radar device. It is.

  On the other hand, since the Gold sequence code generates two codes by preparing two M sequences having the same code length and adding them, the number of types increases compared to the M sequence code. However, the Gold sequence code has a lower autocorrelation and cross-correlation characteristics than the M sequence code, so that it is vulnerable to interference, and the performance of the radar apparatus is reduced, which may cause a malfunction. For this reason, in order to realize a highly reliable radar apparatus, it is necessary to use an M-sequence code, so that the number of types of M-sequence codes can be increased apparently so that it can be used in each radar apparatus. A sequence code generator is required.

In general, a DS-SS radar apparatus using a spreading code uses a code having a longer period than the detection range. For example, as in the case described above, when scanning with a scan range of 100 m and resolution of 1 m, it is possible to scan if a code having a period of at least 100 bits is adopted. In order to improve the autocorrelation characteristics, a code having a period sufficiently larger than 100 bits is adopted (the actual period of the M-sequence code is determined by the number of stages of the shift register and the tap position shown in FIG. 13, and the number of stages of the shift register. Where n is n, the maximum code period is 2 ⁿ -1 bits).

  When a radar signal is transmitted after being spread with an M-sequence code and despread on the receiving side, it is necessary to delay the code on the receiving side in order to obtain a correlation. A delay amount is required. The correlation operation is performed until the receiving side code has a delay of 1 bit or 1 bit or less, and the correlation operation is performed until a delay of 100 bits corresponding to the scan range occurs, and then returns to the initial state. Here, in order to increase the types of M-sequence codes, a case will be considered in which only 100 bits (corresponding to the scan range) of a code having a code cycle of 1000 bits are used in the DS-SS system.

However, in this case, 10 types of 100-bit cycle codes can be generated from 1000-bit cycle codes, but the autocorrelation and cross-correlation characteristics that are characteristic of M-sequence codes are significantly impaired. It is impossible to use.
JP-A-6-160519 "CDMA and next-generation mobile systems", page 98, Table 1 (Kawachi, Trikeps, 1996)

  Thus, in the M-sequence code, since there are few types of codes and it is difficult to assign a different code for each radar device, there is a high possibility of causing misidentification due to a signal from the same type of radar device. When the code is used, the autocorrelation and cross-correlation characteristics are deteriorated compared to the M-sequence code, so that the performance of the radar apparatus is deteriorated and there is a problem that deviates from the purpose of improving the safety.

  The present invention relates to a pseudo-noise code generator and a spread spectrum radar apparatus using codes having excellent autocorrelation and cross-correlation characteristics to solve the above-described conventional problems, and an object of the present invention is to provide a radar apparatus with a low misidentification probability. And

In order to achieve the above object, the code generator of the present invention comprises:
A code generator constituting a spread spectrum radar apparatus,
When a misidentification determination signal is input to the spread spectrum radar apparatus, the phase of the pseudo noise code is shifted to generate a pseudo noise code,
When no false positive determination signal is input to the spread spectrum radar apparatus, a pseudo noise code is generated without shifting the phase of the pseudo noise code.

Furthermore, the code generator comprises:
A code phase detection circuit for detecting a code phase;
A code phase control circuit for controlling a phase for starting a pseudo-noise code from the code phase detected by the code phase detection circuit;
An initial value setting circuit for setting an initial value based on a signal from the code phase control circuit;
An n-stage (n is an integer) shift register that generates a pseudo-noise code based on the initial value, and
Calculate the exclusive OR of the logical value of the nth stage of the shift register and the logical value of the mth stage (1 ≦ m ≦ n, m is an integer), and output the calculated exclusive OR An exclusive logical operation circuit that inputs the first stage of the shift register,
A code generator having a code generation rate control circuit for controlling a code generation rate of the code generator,
When the misidentification determination signal is input, the misidentification determination signal is input to the code phase detection circuit or the code phase control circuit,
The phase may be controlled by the code phase control circuit at the timing when the misidentification determination signal is input, and the phase of the pseudo noise code may be shifted.

Further, the code generator includes:
A code phase control circuit for controlling the phase at which the pseudo-noise code is started;
A read address control circuit for setting a read address based on a signal from the code phase control circuit;
A code generator having a storage element storing a pseudo-noise code,
The code phase control circuit includes a code generation rate control circuit that controls a code generation rate of the code generator;
When the misidentification determination signal is input, the misidentification determination signal is input to the code phase control circuit,
The phase may be controlled by the code phase control circuit at the timing when the misidentification determination signal is input, and the phase of the pseudo noise code may be shifted.

Furthermore, the code generator comprises:
The storage element that outputs parallel data with a first bit width of a pseudo-noise code based on a signal from an address control circuit;
A code selection circuit for converting the parallel data of the first bit width into parallel data of the second bit width;
A parallel / serial converter that converts the parallel data of the second bit width into serial data may be included.

  By providing these code generators in the spread spectrum radar apparatus, it is possible to provide a highly reliable radar apparatus with improved interference resistance, low misperception probability, excellent safety, and high reliability.

  Further, when the misidentification determination signal is input, the phase of the pseudo noise code may be shifted by at least a bit corresponding to the scan range.

  By providing the code generator in the spread spectrum radar apparatus, it is possible to effectively reduce the misidentification probability of the spread spectrum radar apparatus.

  Furthermore, the pseudo-noise code used in the code generator may be characterized in that at least one period is 500 bits or more.

  By providing this code generator in the spread spectrum radar apparatus, an autocorrelation suppression ratio (20 log (code period)) related to the detection probability of the radar can be obtained by 50 dB or more, and the accuracy of the radar apparatus can be improved. .

  Furthermore, the code phase control circuit may control the code phase to be started according to the identification information when the misidentification determination signal is input.

  By providing this code generator in the spread spectrum radar apparatus, it is possible to efficiently reduce the misidentification probability of the spread spectrum radar apparatus.

  Furthermore, the code phase control circuit may change the pseudo-noise code according to the identification information when the misidentification determination signal is input.

  By providing this code generator in the spread spectrum radar apparatus, it is possible to efficiently reduce the misidentification probability of the spread spectrum radar apparatus.

Furthermore, when the misidentification determination signal is input, the shift is performed by 1/10 of the code period,
The number of bits corresponding to the scan range may be 1/10 or less of the code period.

  By providing this code generator in the spread spectrum radar apparatus, it is possible to more efficiently reduce the misidentification probability of the spread spectrum radar apparatus.

  If the number of bits corresponding to the scan range is greater than one-tenth of the code period, a phase shift by one-tenth of the code period results in a phase shift that is less than the number of bits corresponding to the scan range. Since the misperception cannot be effectively avoided, the number of bits corresponding to the scan range is set to 1/10 or less of the code period.

Further, when the misidentification determination signal is input, the misidentification determination signal is input to the code generation rate control circuit,
The code generation rate of the code generator may be changed by the code generation rate control circuit at the timing when the misidentification determination signal is input to the code generation rate control circuit.

  By providing the code generator in the spread spectrum radar apparatus, it is possible to effectively reduce the misidentification probability of the spread spectrum radar apparatus.

  Furthermore, the code generation rate may be changed by 1 bit or more per code cycle.

  By providing the code generator in the spread spectrum radar apparatus, it is possible to effectively reduce the misidentification probability of the spread spectrum radar apparatus.

In addition, the spread spectrum radar apparatus of the present invention,
A transmission code generator for generating a first pseudo-noise code;
A reception code generator for generating a second pseudo-noise code that is time-delayed with respect to the first pseudo-noise code;
A spreading modulator that spreads and modulates a signal generated from a signal source by the transmission code generator;
Transmitting means for transmitting a signal subjected to spread modulation by the spread modulator;
Receiving means for receiving a signal transmitted by the transmitting means;
A spread spectrum radar apparatus having a spread demodulator that spreads and demodulates a signal received by the receiving means by the reception code generator,
The number of bits by which the phase of the first pseudo-noise code and the second pseudo-noise code is shifted is the same,
The transmission code generator and the reception code generator are either of the code generators.

  As a result, it is possible to provide a highly reliable radar apparatus with improved interference resistance, low misperception probability, excellent safety, and high reliability.

  Further, in the spread spectrum radar apparatus, the number of bits per cycle in which the code generation rates of the first pseudo noise code and the second pseudo noise code are changed by the code generation rate control circuit is the same. It is also good.

  This can effectively reduce the misperception probability of the spread spectrum radar apparatus.

The code generator of the present invention is
A code generator constituting a spread spectrum radar apparatus,
When a misidentification determination signal is input to the spread spectrum radar apparatus, the code generation rate of the code generator is changed to generate a pseudo noise code,
When no misidentification determination signal is input to the spread spectrum radar apparatus, a pseudo noise code may be generated without changing the code generation rate of the code generator.

  According to the spread spectrum radar apparatus using the code generator of the present invention, the pseudo-noise code can be output with a different phase for each radar apparatus, and a small number of types of codes are assigned to each radar apparatus. However, it is possible to provide a radar device that is not misidentified and that is excellent in safety.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram for explaining a spread spectrum radar apparatus of the present invention. The radar apparatus of the present invention includes a transmission code generator 10 that generates a first pseudo-noise code, and a reception code generator that generates a second pseudo-noise code that is time-delayed with respect to the transmission code generator 10. , Spreader modulator 11 for spreading and modulating the signal generated from the signal source by transmission code generator 10, transmitting means 12 for transmitting the spread modulated signal, receiving means 21 for receiving the signal, and received signal And a spreading demodulator 22 that demodulates the signal based on the reception code generator 20, and by outputting the code output from the transmission code generator 10 in a different phase for each radar apparatus, misidentification from the same type of radar apparatus To avoid.

  The following describes how to avoid specific misidentifications.

  FIG. 2 is a diagram showing the state (phase) of codes used in the radar device A61 and the radar device B62 in the situation of FIG. Here, as the code condition and the radar operation condition, it is assumed that one cycle of the code is 1000 bits, and a code appropriately given a number from 1 to 1000 is used, and the scan range is 100 m and the resolution is 1 m as the radar operation condition.

  First, the radar device A61 is misidentified by the radar signal of the radar device B62, and (1) the case where the radar device A61 avoids the misidentification is described.Next, (2) both the radar device A61 and the radar device B62 are misidentified. Describe the case to avoid.

  The transmission code of the radar device A61 is shown in FIG. 2 (a), the transmission code of the radar device B62 received by the radar device A61 (hereinafter referred to as the interference signal of the radar device B62) is shown in FIG. 2 (e), and the correlation of the radar device A61. The codes for use (despreading codes) are shown in FIGS. The correlation code of the radar device A61 starts from the code delayed by 1 bit in FIG. 2 (b). Thereafter, the code is delayed by 1 bit or 1 bit or less every one period or arbitrary period, and finally, the code shown in FIG. ), A code delayed by 100 bits corresponding to the scan range of 100 m is used. Here, since the correlation code delayed by 50 bits in FIG. 2 (c) and the transmission code of the radar apparatus B62 in FIG. 2 (e) have the same phase and synchronization is established, the interference wave shown in FIG. Misidentification occurs) by observing (misidentification signal).

(1) When the radar apparatus A61 avoids misperception In order to avoid this misperception, the phase of the transmission code of the radar apparatus A61 shown in FIG. ) And the scan is performed again. This is shown in FIGS. 2 (f) to (h).

  In the present invention, “phase shift” refers to shifting (changing) both the phases at which the pseudo-noise code is started by the transmission code generator 10 and the reception code generator 20 when misidentification occurs. The term “delay” means that the phase of the pseudo noise code by the reception code generator 20 is delayed (changed) with respect to the pseudo noise code by the transmission code generator 10. Also, the number of bits to be “delayed” usually does not become larger than the bit corresponding to the scan range (however, it does not always become larger than the bit corresponding to the scan range).

  FIG. 2 (f) shows the transmission code of the radar apparatus A61 obtained by shifting the transmission code of the radar apparatus A61 shown in FIG. 2 (a) by 100 bits. In FIG. 2 (f), a code starting from "901" that is phase-shifted by 100 bits is used, but a code that is phase-shifted by 100 bits starting from "101" may be used as the code phase. 2 (g) shows a correlation code (despreading code) obtained by delaying the transmission code shown in FIG. 2 (f) by 1 bit, and FIG. 2 (h) shows the transmission code shown in FIG. 2 (f). Represents a correlation code (despreading code) delayed by 100 bits.

  Here, attention is paid to the code phase when the time on the horizontal axis in FIG. 2 is “0”. When the time on the horizontal axis in FIG. 2 is “0”, the phase of the transmission code of the radar apparatus B62 in FIG. 2 (e) is “951”. On the other hand, the phase of the correlation code of the phase-shifted radar apparatus A61 changes from “900” in FIG. 2G to “801” in FIG.

  When the phase is shifted in this way, the correlation code of the radar device A61 does not synchronize with the transmission code of the radar device B62, so that misidentification can be avoided.

  Next, in the initial state of the radar device A61 and the radar device B62 (FIGS. 2 (a) and (e)), not only the radar device A61 but also the radar device B62 is misunderstood by the radar device A61, and both are avoided. Consider the case of 100-bit phase shift.

(2) When both radar device A61 and radar device B62 avoid misidentification For example, when both the transmission codes of radar device A61 and radar device B62 are phase-shifted by 100 bits, the transmission code of radar device A61 is as shown in FIG. ), And the transmission code of the radar device B62 is as shown in FIG. In this case, since both of the radar devices are phase-shifted in the same direction by 100 bits, the correlation code of the radar device A61 is again synchronized with the code of FIG. 2 (i), and misidentification occurs.

  Therefore, in order to avoid this situation, it is effective to assign a code phase shift method for each radar device in advance when a misperception occurs or to assign a code type to each radar device. It is. For example, the type of code to be assigned, the phase at which the code starts, and the phase shift method at the time of misidentification are defined by the identification number (number plate) assigned to the vehicle on which the radar device is mounted.

  FIG. 3 is a diagram showing a code start phase and a code phase shift method according to the identification number. FIG. 3 shows that “when the radar device receives a misidentification signal, if the first digit of the identification number of the radar device is 1, the code is advanced by 100 bits” and “the phase of the first digit according to the first digit of the identification number Even if it is shifted, if the misidentification still occurs, the sign is further advanced by 100 bits when the tenth digit of the identification number of the radar apparatus is 0, for example.

  As shown in FIG. 3, by using the first digit and the tenth digit of an identification number such as a license plate and determining the start phase of the code, the misunderstanding of the initial state is avoided. In this case, a phase shift of that bit (for example, 1/10 of the code period) is performed according to a predetermined rule. In the present embodiment, as an example, the case where the bit corresponding to the scan range is 1/10 of the code period is given.

  For example, when there is a misidentification between the correlation code of the radar device A61 in FIG. 2 (c) and the transmission code of the radar device B62 in FIG. 2 (e), the radar device A61 is mounted as shown in FIG. If the first place of the vehicle identification number is 0 and the first place of the identification number of the vehicle equipped with the radar device B62 is 1, the transmission code of the radar device A61 is 100 bits (10 minutes of the code period). 1) Since the phase is shifted, FIG. 2 (f) is obtained, and since the transmission code of the radar apparatus B62 is advanced by 100 bits (1/10 of the code period), FIG. 2 (j) is obtained. When attention is paid to the code phase at time “0” in FIG. 2 as before, the transmission code of the radar apparatus A61 in FIG. 2 (f) starts from “901”, so the phase of the correlation code is “900”. From "" to "801", the phase of the interference signal (FIG. 2 (j)) of the radar apparatus B62 is "51". For this reason, since the synchronization code of the radar device A61 and the interference signal of the radar device B62 are not established, no misidentification occurs.

  Also, if the code types of both radar devices are the same and the first digit of the identification number takes the same number, the phase shifts by the same amount. If they are different, the phase shift amount determined by the tens place is different, so that misidentification can be avoided.

  It should be noted that these first and tenth identification numbers can be read using an image recognition technique such as a camera and the phase of a code to be transmitted can be determined.

  Further, such a phase shift method at the time of misidentification can be provided to the code phase control circuit 32 (see FIG. 4 and the like).

  In some cases, the first digit and the tenth digit of the identification number may be the same. In addition, different types of codes may be allocated in advance for each radar device depending on the hundredth and thousandth digits of the identification number. For example, it is possible to assign codes to all vehicles with 100 types of M-sequence codes, and it is possible to assign codes to all vehicles by using M-sequence codes (176 types) consisting of 11 stages of shift registers. Become.

  As described above, according to the present invention, it is possible to efficiently avoid the reception of the misidentification signal by the radar apparatus even when using a few types of M-sequence codes, and to reduce the probability of misidentification. Become.

  The misidentification avoidance method described above is merely an example, and is not limited to this method. For example, "Use a license plate pseudonym to pre-allocate different types of codes for each radar device" or "Use identification numbers in the hundreds and thousandss to pre-identify It is also conceivable to allocate the phase shift method for each radar device. In addition, an identification number (identification information) unique to the pseudo-noise code generator may be selected.

  Further, although the above-described phase shift amount is 100 bits, the phase shift may be performed by 100 bits (scan range) or more.

  In this embodiment, at least 100 bits are required for the code period required for the scan range required for the radar. However, in order to improve the accuracy, the number of bits of the code period may be increased.

  In addition, in order to obtain an autocorrelation suppression ratio (20 log (code cycle)) of 50 dB or more related to the detection probability of the radar by shifting the phase at least by the bit of the scan range (100 bits in this embodiment) at the time of misidentification Therefore, an M-sequence code having a code period of at least 500 bits is required.

  In addition, when a long period code is used, the number of times the phase can be shifted to avoid misidentification increases (when the scan range is 100 m and the resolution is 1 m, for example, when the code period is 1000 bits, the phase shift is 10 times. (For example, when 2000 bits, phase shift can be performed 20 times), it is easy to avoid misidentification.

  If a radar device having excellent interference resistance is not required, a pseudo-noise code other than the M-sequence code may be used as the code to be used.

  Next, specific embodiments of the code generator used in the radar apparatus of the present invention will be described below.

  FIG. 4 is a diagram showing the configuration of the M-sequence code generator, which corresponds to the transmission code generator 10 and the reception code generator 20 in FIG.

  The code generator of the present invention shown in FIG. 4 receives a code phase detection circuit 31 for detecting a code phase and a misidentification determination signal from the misidentification determination unit 36, and from the information of the code phase detected by the code phase detection circuit 31. A code phase control circuit 32 that controls the phase at which the M-sequence code is started, an initial value setting circuit 33 that sets an initial value based on a signal from the code phase control circuit 32, and n stages (any initial value can be set) n is an integer), and the exclusive OR of the n-th logic value of the shift register and the m-th logic value (1 ≦ m ≦ n, m is an integer) is calculated and calculated. The exclusive logical operation circuit 35 that inputs the output of the exclusive OR that has been output to the first stage of the shift register 34, and the code generation rate control circuit 37 that controls the generation rate of the pseudo noise code of the shift register 34 .

  The code generation rate control circuit 37 includes a clock signal generator, and the clock signal generated from the clock signal generator is input to the shift register 34. The code generation rate control circuit 37 can change the chip rate (code generation rate) by changing the clock signal.

  Further, the misrecognition determination signal can be input to the code generation rate control circuit 37 via the code phase control circuit 32 (however, although not shown, the misrecognition determination signal is not transmitted through the code phase control circuit 32, the code It may be input to the generation rate control circuit 37).

  The misidentification determiner 36 determines whether there is misidentification. If there is misidentification, it generates a misidentification determination signal having “misidentification” information, and if there is no misidentification, a signal having “misidentification” information. Is generated.

  In addition, the “presence / absence of misidentification” by the misidentification determination unit 36 can be determined, for example, by performing reception only by a receiving unit without transmitting a transmission signal in the radar apparatus. Specifically, by transmitting only the reception means without transmitting a transmission signal, when a code that is synchronized with the transmission code is received, “misidentified (occurrence of misidentification)”, synchronized with the transmission code. When the code to be received is not received, it can be determined that “no misidentification (no misidentification occurs)”. However, this “presence / absence of misidentification” is merely an example, and even when a transmission signal is transmitted, for example, the presence / absence of misidentification is determined by comparing the intensity of the detection signal and the interference wave. It is possible.

  In FIG. 4, the misidentification determination signal by the misidentification determination unit 36 is described as being sent to the code phase detection circuit 31 and the code phase control circuit 32. 1) The case where the operation (detecting the code phase) continues without relying on the misidentification determination signal and the case (2) the operation (detecting the code phase) based on the misidentification determination signal are different.

  Specifically, (1) when the code phase detection circuit 31 continues to operate without relying on the misidentification determination signal, the misidentification determination signal does not need to be sent to the code phase detection circuit 31 and is sent to the code phase control circuit 32. The code phase control circuit 32 controls (determines) the phase at which the M-sequence code starts from the code phase information detected by the code phase detection circuit 31 at the timing when the misidentification determination signal is input to the code phase control circuit 32. The code phase shift is then performed.

  On the other hand, (2) when the code phase detection circuit 31 is operated by the misidentification determination signal, the misidentification determination signal does not need to be sent to the code phase control circuit 32, but is sent to the code phase detection circuit 31 and the misidentification determination signal is input. At the same timing, the code phase detection circuit 31 detects the code phase, the code phase control circuit 32 controls (determines) the phase for starting the M-sequence code from the detected code phase information, and the code phase shift is executed. The

  As described above, the code generator of the present invention shown in FIG. 4 makes it possible to output an M-sequence code at an arbitrary phase, and a phase shift corresponding to the scan range can be executed when it is erroneously recognized. Note that when no misidentification determination signal is input, the phase shift of the radar apparatus is not performed.

  FIG. 5 is a diagram illustrating a code generator using a storage element, and corresponds to the transmission code generator 10 and the reception code generator 20 in FIG.

  The code generator of the present invention shown in FIG. 5 includes a code phase control circuit 32 that controls (determines) the phase at which the pseudo-noise code is started at the timing when the misidentification determination signal from the misidentification determination unit 36 is input, and the code phase control A read address control circuit 41 that sets a read address based on a signal from the circuit 32 and a storage element 42 that stores a pseudo noise code are provided. A code other than the M-sequence code may be stored in the memory element, and by storing a plurality of codes, it is possible to reduce the probability of misidentification.

  In FIG. 5, the code phase control circuit 32 has a code generation rate control circuit 37 for controlling the code generation rate, and the clock signal generated from the clock signal generator in the code generation rate control circuit 37 is read out. Input to the address control circuit 41.

  Further, the code generator shown in FIG. 5 does not have the code phase detection circuit 31 unlike the code generator shown in FIG. This is because in the code generator shown in FIG. 5, since the read address control circuit 41 sets all the read addresses, it is clear which phase code is generated without detecting the code. On the other hand, in the code generator shown in FIG. 4, since the code is automatically generated after the initial value is set by the initial value setting circuit 33, the code phase detection circuit 31 does not detect the code phase. This is because it is not known which phase code is being generated.

  Next, a radar device is installed in a place where misidentification is likely to occur and there is a possibility that the misidentification cannot be avoided even if phase shifting is performed (for example, a parking lot of a large shopping center where a large number of cars exist in a narrow range). Consider the case where there is a vehicle that has been used.

  When the radar device is operated under the above-mentioned conditions (code cycle: 1000 bits, scan range: 100 m, resolution: 1 m), if it is misidentified by 10 vehicles, it will be misidentified regardless of which phase it is shifted to, Misidentification cannot be avoided with only one type of code.

  However, by preparing a plurality of codes, it is possible to avoid misidentification by changing to a different code.

  Hereinafter, a method for avoiding misidentification by storing a plurality of codes in the storage element will be described.

  FIG. 6A is a flowchart showing a flow of code output of a code generator using a memory element that can avoid misidentification, and FIG. 6B shows three types of codes A1 to A1000 and B1 to B1000 in the memory element. , C1 to C1000 (1 cycle: 1000 bits) are stored.

  First, when it is determined that there is no “misidentification” by the misidentification determination unit 36, for example, the read address is determined as (R-1, C-1) to (R-1, C-100), and the pseudo-noise code Are sequentially output. Therefore, no phase shift is performed.

  Next, when it is determined by the misidentification determining unit 36 that “there is a misidentification”, it is necessary to perform a phase shift corresponding to at least the scan range. For example, a phase shift of 100 bits corresponding to the scan range of 100 m is performed. .

  That is, the start position of the code shown in FIG. 6B is shifted from A1 (address: R-1, C-1) to A101 (address: R-2, C-1). Here, when it is determined that there is no “misidentification” by the misidentification determination unit 36, the read address is determined as (R-2, C-1) to (R-2, C-100), and the pseudo-noise code Are sequentially output.

  On the other hand, if misperception continues, the code start position is set to A201 (address: R-3, C-1), and phase shift is continued until there is no misperception. Finally, if the code start position is A901 (address: R-10, C-1) and the error occurs, the code start position is changed to B1 (address: R-11, C-1). Then, the code is changed to another code. The operation to change A901 (address: R-10, C-1) to B1 (address: R-11, C-1) is the same as when the code phase is shifted by 100 bits. be able to.

  In this way, misidentification can be avoided by changing from a code that has been misunderstood to another code.

  Also, if misidentification is not avoided even if the same phase shift operation is performed on the codes B1 to B1000, the code is changed to the code C (C1 (address: R-21, C-1)) by the same code change operation. That's fine.

  In addition, it is possible to further reduce the misidentification probability by randomly assigning the code stored in the storage element to each radar device.

  Further, according to the misidentification avoidance method shown in FIGS. 6 (a) and 6 (b), since the code can be changed to another code after the misidentification, the code phase shift method shown in FIG. It is also possible to apply not the phase shift but a sign change method after misrecognition.

  FIG. 7 is a diagram showing a code generator that outputs a code at a high code generation rate (chip rate), and corresponds to the transmission code generator 10 and the reception code generator 20 in FIG.

  The code generator of the present invention shown in FIG. 7 includes a code phase control circuit 32 that determines a phase at which a pseudo noise code starts at a timing when a misidentification determination signal is input by the misidentification determination unit 36, and a code phase control circuit 32 A read address control circuit 41 that sets a read address based on the signal of the above, and a storage element 42 that outputs a pseudo noise code as parallel data having a first bit width (for example, 15 bits) based on the signal from the read address control circuit 41; A code selection circuit 51 that converts parallel data of the first bit width into parallel data of the second bit width (for example, 8 bits), and parallel / serial conversion that converts the parallel data of the second bit width into serial data Device 52.

  In FIG. 7, the code phase control circuit 32 has a code generation rate control circuit 37 for controlling the code generation rate, and the clock signal generated from the clock signal generator in the code generation rate control circuit 37 is read out. This is input to the address control circuit 41 and the parallel / serial converter 52. However, since the code generation rate differs between when the pseudo-noise code is output as parallel data and when it is output as serial data, the clock signal input to the read address control circuit 41 and the parallel / serial converter 52 are input. Clock signals are not the same signal. That is, the clock signal input to the parallel / serial converter 52 is faster than the clock signal input to the read address control circuit 41.

  According to the code generator of FIG. 7, in addition to the code generator of FIG. 5, the code can be output at a higher speed, and the resolution of the radar apparatus is improved. In this way, it can be applied to a short-range radar apparatus that requires high resolution.

  Although not shown, the code generators of the present invention shown in FIGS. 4, 5 and 7 can input not only a misidentification determination signal but also a signal other than the misidentification determination signal. For example, the code generator on the receiving side also receives a signal having information on the transmitting side, and generates a code that is time-delayed with respect to the code by the code generator on the transmitting side. The phase corresponding to this time delay is controlled by the code phase control circuit 32.

  Although not shown, the code phase control circuit 32 can also input a signal having information of “no misidentification”.

  Finally, FIG. 11 (f): the correlation code of the radar device A61 and FIG. 11 (g): the transmission code of the radar device B62 are synchronized, as shown in FIG. 4, FIG. 5, and FIG. A method for avoiding misidentification by changing the chip rate of the code generator will be described.

  The code generator chip rate (code generation rate) shown in FIGS. 4, 5, and 7 is controlled by the code generation rate control circuit 37. Specifically, when misidentification occurs, the misidentification determination signal is sent to the code generation rate control circuit 37, and the code generation rate control circuit 37 controls (determines) the chip rate at the timing when the misidentification determination signal is input. However, the chip rate of the code generator is changed.

  The code states in which the chip rate is changed from the synchronized state are shown in FIGS. FIGS. 8A to 8C show correlation codes (despreading codes) of the radar apparatus A61. FIG. 8A shows a case where the chip rate is not changed, and FIG. 8C shows a case where the chip rate is lowered, and FIG. 8D shows a pseudo-noise code radiated from the radar apparatus B62 and received by the radar apparatus A61.

  When the chip rate is changed, the chip rates of the transmission code generator 10 and the reception code generator 20 in FIG. 1 are simultaneously changed.

  8 (a) and 8 (d) have the same chip rate, the synchronization state continues and misidentification continues. On the other hand, when the chip rate is increased (Fig. 8 (b)) and when the chip rate is decreased (Fig. 8 (c)), a shift of 1 bit occurs in the 20th bit, and 1 bit is changed every 20 bits thereafter. Deviation occurs. For this reason, since synchronization cannot be obtained after 20 bits, a misidentification signal radiated from the radar apparatus B62 is not observed.

  Thus, if the chip rate is changed for each radar device, it is possible to avoid misidentification. However, the chip rate does not have to be a chip rate determined for each radar device, and may be changed only when misunderstanding is received, or may be periodically changed without being misunderstood. In addition, by changing the amount of change in the chip rate by 1 bit (1 bit / cycle) or more per cycle, the transition from synchronous to asynchronous is made, so that it is possible to reduce the signal strength when it is mistaken. Further, by using a combination of the method of changing the chip rate and the method of outputting the code by shifting the phase described above, the ability to avoid misidentification is further improved.

  The spread spectrum radar apparatus using the M-sequence code generator according to the present invention can use an M-sequence code for each radar device and is excellent in interference resistance, and thus is useful for an on-vehicle radar device.

The block diagram which shows the structure of the spread spectrum radar apparatus of this invention The figure which shows the state (phase) of the code | symbol in a radar apparatus The figure which shows the code start phase according to an identification number, and a code phase shift method The block diagram which shows the structure of the code generator using the shift register used for the radar apparatus of this invention. The block diagram which shows the structure of the code generator using the memory element used for the radar apparatus of this invention. (A) is a flowchart showing a code output of a code generator using a storage element, (b) is a diagram showing a state of a code stored in the storage element The block diagram which shows the structure of the code generator which outputs a code | symbol at the high-speed chip rate used for the radar apparatus of this invention. The figure which shows the state (phase) of the code | symbol at the time of changing the chip rate in the radar apparatus of this invention Diagram showing a situation where misidentification occurs between radar devices Graph showing the detection signal and interference wave received by the radar device with respect to distance The figure which shows the state (phase) of the code | symbol which the principle of a radar and a misidentification produce The figure which shows the structure of the radar apparatus which can avoid the interference from the conventional similar radar apparatus The figure which shows the structure of the M sequence code generator which uses the conventional n stage shift register

Explanation of symbols

10 Transmitter code generator
11 Spread modulator
12 Transmission method
20 Receiving code generator
21 Receiving means
22 Spreading demodulator
31 Code phase detection circuit
32 Code phase control circuit
33 Initial value setting circuit
34 Shift register
35 Exclusive logical operation circuit
36 Misidentification detector
37 Code generation rate control circuit
41 Read address control circuit
42 Memory element
51 Sign selection circuit
52 Parallel / serial converter
61 Radar device A
62 Radar device B
63 Object

Claims (19)

A code generator constituting a spread spectrum radar apparatus,
When a misidentification determination signal is input to the spread spectrum radar apparatus, the phase of the pseudo noise code is shifted to generate a pseudo noise code,
A code generator, which generates a pseudo-noise code without shifting a phase of a pseudo-noise code when a misidentification determination signal is not input to the spread spectrum radar apparatus. The code generator is
A code phase detection circuit for detecting a code phase;
A code phase control circuit for controlling a phase for starting a pseudo-noise code from the code phase detected by the code phase detection circuit;
An initial value setting circuit for setting an initial value based on a signal from the code phase control circuit;
An n-stage (n is an integer) shift register that generates a pseudo-noise code based on the initial value, and
Calculate the exclusive OR of the logical value of the nth stage of the shift register and the logical value of the mth stage (1 ≦ m ≦ n, m is an integer), and output the calculated exclusive OR Is input to the first stage of the shift register,
A code generator having a code generation rate control circuit for controlling a code generation rate of the code generator,
When the misidentification determination signal is input, the misidentification determination signal is input to the code phase detection circuit or the code phase control circuit,
2. The code generator according to claim 1, wherein the phase of the pseudo-noise code is shifted by the phase control by the code phase control circuit at a timing when the misidentification determination signal is input. The code generator is
A code phase control circuit for controlling the phase at which the pseudo-noise code is started;
A read address control circuit for setting a read address based on a signal from the code phase control circuit;
A code generator having a storage element storing a pseudo-noise code,
The code phase control circuit includes a code generation rate control circuit that controls a code generation rate of the code generator;
When the misidentification determination signal is input, the misidentification determination signal is input to the code phase control circuit,
2. The code generator according to claim 1, wherein the phase of the pseudo-noise code is shifted by the phase control by the code phase control circuit at a timing when the misidentification determination signal is input. The code generator is
The storage element that outputs parallel data with a first bit width of a pseudo-noise code based on a signal from an address control circuit;
A code selection circuit for converting the parallel data of the first bit width into parallel data of the second bit width;
4. The code generator according to claim 3, further comprising: a parallel / serial converter that converts the parallel data of the second bit width into serial data. 5. The code generator according to claim 1, wherein when the misidentification signal is input, the phase of the pseudo-noise code is shifted by at least a bit corresponding to the scan range. 6. The code generator according to claim 1, wherein the pseudo-noise code used in the code generator has at least one cycle of 500 bits or more. The code generator according to any one of claims 2 to 6, wherein the code phase control circuit controls a code phase to be started according to identification information when the misidentification determination signal is input. 5. The code generator according to claim 3, wherein the code phase control circuit changes a pseudo noise code according to identification information when the misidentification determination signal is input. When the misidentification determination signal is input, the shift is performed by 1/10 of the code period, and the number of bits corresponding to the scan range is 1/10 or less of the code period. 8. The code generator according to 7. When the misidentification determination signal is input, the misidentification determination signal is input to the code generation rate control circuit,
The code generation rate of the code generator is changed by the code generation rate control circuit at a timing when the misidentification determination signal is input to the code generation rate control circuit. The code generator according to claim 1. The code generator according to claim 10, wherein the code generation rate is changed by 1 bit or more per code cycle. A transmission code generator for generating a first pseudo-noise code;
A reception code generator for generating a second pseudo-noise code that is time-delayed with respect to the first pseudo-noise code;
A spreading modulator that spreads and modulates a signal generated from a signal source by the transmission code generator;
Transmitting means for transmitting a signal subjected to spread modulation by the spread modulator;
Receiving means for receiving a signal transmitted by the transmitting means;
A spread spectrum radar apparatus having a spread demodulator that spreads and demodulates a signal received by the receiving means by the reception code generator,
The number of bits by which the phase of the first pseudo-noise code and the second pseudo-noise code is shifted is the same,
The spread code radar apparatus according to any one of claims 1 to 9, wherein the transmission code generator and the reception code generator are code generators according to any one of claims 1 to 9. A transmission code generator for generating a first pseudo-noise code;
A reception code generator for generating a second pseudo-noise code that is time-delayed with respect to the first pseudo-noise code;
A spreading modulator that spreads and modulates a signal generated from a signal source by the transmission code generator;
Transmitting means for transmitting a signal subjected to spread modulation by the spread modulator;
Receiving means for receiving a signal transmitted by the transmitting means;
A spread spectrum radar apparatus having a spread demodulator that spreads and demodulates a signal received by the receiving means by the reception code generator,
The number of bits by which the phase of the first pseudo-noise code and the second pseudo-noise code is shifted is the same,
The number of bits per cycle in which the code generation rate of the first pseudo noise code and the second pseudo noise code is changed by the code generation rate control circuit is the same,
12. The spread spectrum radar apparatus according to claim 10, wherein the transmission code generator and the reception code generator are code generators according to claim 10. A code generator constituting a spread spectrum radar apparatus,
When a misidentification determination signal is input to the spread spectrum radar apparatus, the code generation rate of the code generator is changed to generate a pseudo noise code,
A code generator that generates a pseudo-noise code without changing a code generation rate of the code generator when a misidentification determination signal is not input to the spread spectrum radar apparatus. The code generator is
A code phase detection circuit for detecting a code phase;
A code phase control circuit for controlling a phase for starting a pseudo-noise code from the code phase detected by the code phase detection circuit;
An initial value setting circuit for setting an initial value based on a signal from the code phase control circuit;
An n-stage (n is an integer) shift register that generates a pseudo-noise code based on the initial value, and
Calculate the exclusive OR of the logical value of the nth stage of the shift register and the logical value of the mth stage (1 ≦ m ≦ n, m is an integer), and output the calculated exclusive OR Is input to the first stage of the shift register,
A code generator having a code generation rate control circuit for controlling a code generation rate of the code generator,
When the misidentification determination signal is input, the misidentification determination signal is input to the code generation rate control circuit,
15. The code generator according to claim 14, wherein the code generation rate is changed by the code generation rate control circuit at a timing when the misidentification determination signal is input to the code generation rate control circuit. The code generator is
A code phase control circuit for controlling the phase at which the pseudo-noise code is started;
A read address control circuit for setting a read address based on a signal from the code phase control circuit;
A code generator having a storage element storing a pseudo-noise code,
The code phase control circuit includes a code generation rate control circuit that controls a code generation rate of the code generator;
When the misidentification determination signal is input, the misidentification determination signal is input to the code generation rate control circuit,
15. The code generator according to claim 14, wherein the code generation rate is changed by the code generation rate control circuit at a timing when the misidentification determination signal is input to the code generation rate control circuit. The code generator is
The storage element that outputs parallel data with a first bit width of a pseudo-noise code based on a signal from an address control circuit;
A code selection circuit for converting the parallel data of the first bit width into parallel data of the second bit width;
17. The code generator according to claim 16, further comprising a parallel / serial converter that converts the parallel data of the second bit width into serial data. The code generator according to any one of claims 14 to 17, wherein the code generation rate is changed by 1 bit or more per code cycle. A transmission code generator for generating a first pseudo-noise code;
A reception code generator for generating a second pseudo-noise code that is time-delayed with respect to the first pseudo-noise code;
A spreading modulator that spreads and modulates a signal generated from a signal source by the transmission code generator;
Transmitting means for transmitting a signal subjected to spread modulation by the spread modulator;
Receiving means for receiving a signal transmitted by the transmitting means;
A spread spectrum radar apparatus having a spread demodulator that spreads and demodulates a signal received by the receiving means by the reception code generator,
The number of bits per cycle in which the code generation rate of the first pseudo noise code and the second pseudo noise code is changed by the code generation rate control circuit is the same,
The spread code radar apparatus according to any one of claims 14 to 18, wherein the transmission code generator and the reception code generator are code generators according to any one of claims 14 to 18.

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