JP5600928B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar apparatus, and more particularly to a radar apparatus mounted on a moving body such as an automobile.

  In recent years, a mobile device such as an automobile (hereinafter simply referred to as a mobile body) is equipped with a radar device for measuring a relative distance from a surrounding object (for example, a person, a vehicle, a road installation, etc.). Has been. Among the radar apparatuses mounted on the moving body, there is a radar apparatus that performs correlation processing in order to increase the accuracy of the measurement result.

  A radar apparatus that performs correlation processing transmits a code signal as a transmission signal, and receives a reflection signal obtained by reflecting the transmission signal on an object. Then, a correlation process for calculating a correlation value between the reference signal having the same code as the code signal and the reflected signal is performed, and based on a time from when the transmission signal is transmitted until a correlation value exceeding a predetermined threshold is detected. Measure the relative distance to the object. Thereby, the radar apparatus that performs the correlation processing can reduce the influence of noise superimposed on the reflected signal, and can increase the accuracy of the measurement result of the relative distance.

  An example of a technique applicable to such a radar apparatus is a processing apparatus described in Patent Document 1 (hereinafter referred to as a conventional technique). In the prior art, two processing channels A and B are provided in order to reduce the noise level when performing correlation processing. In the prior art, the noise level is reduced by comparing the results of correlation processing in each of the two processing channels A and B. Therefore, if the above-described conventional technique is applied to a radar apparatus that performs correlation processing, the accuracy of measurement results can be further increased.

JP-A-6-102347

  However, the above prior art has the following problems. In other words, the above-described conventional technique requires two processing channels in order to reduce the noise level generated when performing correlation processing. Therefore, the cost of the radar apparatus that performs correlation processing to which the above-described conventional technology is applied is increased.

  Therefore, an object of the present invention is to provide a radar apparatus that can reduce a noise level generated when performing correlation processing at a low cost.

In order to solve the above problems, the present invention has the following features.
That is, the present invention comprises a transmitting means for continuously transmitting N or more code signals that are encoded signals, and a receiving means for receiving a reflected signal in which the code signal is reflected by an object; Corresponding to the storage means for storing, as a comparison code, the same code as the code for encoding the code signal transmitted from the transmission means, the comparison code, and the code signal transmitted in succession by the N number Measuring means for measuring the object based on a correlation with a code decoded from the reflected signal, wherein the measuring means includes the comparison code and the N consecutively transmitted code signals. The correlation value with the code decoded from the reflected signal corresponding to the (N-1) th code signal is used as the comparison code and the reflection corresponding to the N code signals transmitted continuously. Decoded from signal The correlation value between the items, a radar device. For example, N = 3.
According to another first aspect of the invention, a transmitting means for transmitting an encoded signal as a code signal, a receiving means for receiving a reflected signal of the code signal reflected by an object, and a code signal transmitted from the transmitting means are encoded. A storage means for storing the same code as the code used for the conversion as a comparison code, a comparison code identical to the code, a plurality of consecutive codes of the code decoded from the reflected signal, and the other code Measuring means for measuring the object based on the correlation with the code.

Another second invention is an invention subordinate to the other first invention, wherein the transmitting means transmits a code signal encoded with N consecutive codes, and the measuring means includes N number of codes. The object is measured based on the code decoded from the reflected signal reflected from the object and the code decoded from the N-1th reflected signal and one comparison code among the codes decoded by the continuous code. .

Another third invention is an invention subordinate to the other second invention, wherein the transmitting means transmits a code signal encoded with three consecutive codes, and the measuring means includes three The object is measured based on the code decoded from the second reflected signal and the one comparison code among the codes decoded from the reflected signal reflected from the object by the code signal encoded by the continuous code.

The other fourth invention is an invention subordinate to the other first invention, wherein the measuring means is based on a correlation between one code decoded from the reflected signal and three or more consecutive comparison codes. Measure the object.

Another fifth invention is an invention subordinate to the other fourth invention, wherein the measuring means is a second code among one code decoded from the reflected signal and three or more consecutive comparison codes. The object is measured based on the correlation with the comparison code.

  A radar apparatus capable of reducing the noise level generated when performing correlation processing can be provided at low cost.

1 is a block diagram showing a schematic configuration of a radar apparatus according to the present invention. The figure which shows an example of the code | symbol when encoding a reference signal The figure which shows an example of the code | symbol signal produced | generated continuously The figure which shows an example of a comparison code The figure which shows an example of a reflective code and a comparison code when calculating a correlation value The figure which shows an example of a reflective code and a comparison code when calculating a correlation value The figure which shows the relationship between the reflective code which becomes the largest correlation value, and the comparison code The figure which shows the relationship between the reflection code and the comparison code which become the random correlation value The figure which shows an example of the relationship between the reflective code | symbol used as the correlation value of the constant close | similar to zero, and a comparison code | symbol The figure which shows an example of the code signal transmitted toward several objects The figure which shows an example of the reflected signal reflected by the several target object The figure which shows an example of the reflective code decoded from the reflected signal received with a certain time difference The figure which shows an example of the continuous reflective code decoded from the continuous reflected signal received with a certain time difference The figure which shows an example of the time relationship between the code signal transmitted and the reflected signal received The figure which shows an example of the time relationship between the code signal transmitted and the reflected signal received The flowchart which shows the process of the signal processing part which concerns on 1st Embodiment. The figure which shows an example of a continuous comparison code and a reflective code

(First embodiment)
FIG. 1 is a block diagram showing a schematic configuration of a radar apparatus 1 according to the first embodiment of the present invention. The radar apparatus 1 according to the present embodiment includes a reference signal generation unit 101, a code signal generation unit 102, a first amplification unit 103, a transmission antenna 104, a reception antenna 105, a second amplification unit 106, A mixing unit 107, an LPF (Low Path Filter) 108, a matched filter 109, and a signal processing unit 110 are provided.

  The reference signal generation unit 101 is typically a VCO (Voltage Control Oscillator) that generates a sine wave signal having a frequency corresponding to a control voltage. The reference signal generation unit 101 generates a sine wave signal having a predetermined frequency.

The code signal generation unit 102 acquires the reference signal generated by the reference signal generation unit 101. While acquiring the reference signal, the code signal generation unit 102 multiplies the reference signal with a code having a code length n composed of the first chip L ₁ to the n-th chip L _n as shown in FIG. 2 as an example. A code signal S is generated by encoding. Here, the code according to the present embodiment is assumed to be a binary PN (Pseudo Noise) code that takes a value of 0 or 1 as time passes, as shown in FIG. 2 as an example. In addition, it is assumed that the code pattern when the code signal generation unit 102 encodes the reference signal is predetermined.

  The code signal generation unit 102 according to the present embodiment generates three code signals S in succession as shown in FIG. In addition, when the code signal generation unit 102 according to the present embodiment generates three code signals S consecutively, the start timing when the generation of the second code signal S is started (hereinafter referred to as the first start) (Referred to as timing). In addition, when the code signal generation unit 102 according to the present embodiment generates three code signals S consecutively, the start timing when the generation of the third code signal S is started (hereinafter referred to as the second start) (Referred to as timing) is notified to the matched filter 109. Further, the code signal generation unit 102 according to the present embodiment notifies the matched filter 109 and the signal processing unit 110 of the completion timing when the generation of the third code signal S is completed. The code signal S generated by the code signal generation unit 102 is a signal that has been subjected to modulation processing such as frequency conversion so as to be suitable for radiating the code signal S into space.

  The first amplifying unit 103 amplifies the code signal S generated by the code signal generating unit 102 with a predetermined amplification factor.

  The transmission antenna 104 radiates and transmits the code signal S amplified by the first amplification unit 103 to space.

  The receiving antenna 105 receives a reflected signal R obtained by reflecting the code signal S transmitted from the transmitting antenna 104 by an object.

  The second amplifying unit 106 amplifies the reflected signal R received by the receiving antenna 105 with a predetermined amplification factor.

  The mixing unit 107 mixes the reference signal generated by the reference signal generation unit 101 and the reflected signal R amplified by the second amplification unit 106. The mixing unit 107 mixes the reference signal and the reflected signal R, thereby converting the frequency of the reflected signal R amplified by the second amplifying unit 106 into a baseband frequency (frequency of the reference signal).

  The LPF 108 filters and passes only signal components in a frequency band equal to or lower than a predetermined frequency in the reflected signal R whose frequency has been converted by the mixing unit 107.

  The matched filter 109 sequentially decodes the code when the reflected signal R is transmitted as the code signal S from the reflected signal R. The matched filter 109 sequentially calculates a correlation value by sequentially decoding a code from the reflected signal R and comparing it with a comparison code stored in advance. Since the code signal generation unit 102 generates the code signal S subjected to the modulation process as described above, the matched filter 109 performs the demodulation process corresponding to the modulation process and then performs the demodulation process from the reflected signal R that has been demodulated. Decode the code.

The comparison code stored in advance in the matched filter 109 is a code having a code length n including the first chip M ₁ to the n-th chip M _n as shown as an example in FIG. That is, the code length of the comparison code is the same as the code length of the code multiplied by the reference signal when the code signal S is generated. Also, the pattern of the comparison code is such that the correlation value exceeds a predetermined threshold only when the reflected signal R of the code signal S reflected by the object is received among the signals received by the receiving antenna 105. The pattern of the code to be multiplied when the code signal S is generated is the same pattern.

  Then, when calculating the correlation value, the matched filter 109 sequentially decodes the reflected signal R, and sequentially shifts the decoded code (hereinafter referred to as “reflected code”) one chip at a time as the comparison code and Are sequentially calculated. 5A and 5B are diagrams showing specific examples of the reflection code and the comparison code when the chip is shifted. FIG. 5A is a diagram showing a chip shift between a reflection code and a comparison code at a certain time, and FIG. 5B is a diagram showing a reflection code and a comparison code obtained by shifting the reflection code shown in FIG. 5A by one chip. is there. As is clear from FIGS. 5A and 5B, the matched filter 109 compares the reflected code, which has been sequentially decoded over time, with the comparison code while sequentially shifting the reflected code one chip at a time. Calculate values sequentially.

  As described above, three code signals S are generated in succession and radiated into space. For this reason, three reflected signals R received by the receiving antenna 105 are received continuously. Therefore, when only one code signal S is generated, as shown in FIGS. 5A and 5B, the reflection codes do not continue, but in the present embodiment, three reflection codes continue.

  The matched filter 109 according to the present embodiment calculates a correlation value between the reflection code decoded from the second reflected signal R among the three consecutively received reflected signals R and the comparison code.

  Here, in order to explain the reason why the matched filter 109 calculates the correlation value between the reflection code decoded from the second reflected signal R of the reflection codes and the comparison code, first, the comparison code, the reflection code, The relationship between the chip deviation and the correlation value will be described with reference to FIGS. 6A to 6C.

  FIG. 6A is a diagram illustrating an example of a case where the chips of the reflection code (the reflection code decoded from one reflection signal R) and the comparison code match without deviation. As shown in FIG. 6A as an example, the correlation value calculated when the first to n-th chips of the reflection code and the comparison code match without deviation is the largest value.

  FIG. 6B is a diagram illustrating an example in which the chips of the reflection code (the reflection code decoded from one reflection signal R) and the comparison code are misaligned. As shown as an example in FIG. 6B, when the chips of the reflection code and the comparison code are shifted, they are received after receiving the reflection signal R encoded by the reflection code in addition to the reflection code. Noise or the like is added to the calculation of the correlation value with the comparison code. For this reason, the correlation value calculated when the chips of the reflection code and the comparison code are shifted is a random correlation value not related to the actual correlation between the reflection code and the comparison code.

  FIG. 6C is a diagram illustrating an example in which the first chip to the nth chip of the comparison code do not match the first chip to the nth chip of the continuous reflection code. As shown in FIG. 6C as an example, when the chips of each of the successive reflection codes and the comparison codes do not match and the mutual codes are PN codes as described above, the calculated correlation value is zero. A close constant.

  Next, correlation values calculated when the code signal S is reflected by a plurality of objects having different relative distances will be described with reference to FIGS. 7A to 7C. 7A to 7C show the case where one code signal S is transmitted instead of the case where three consecutive code signals S are transmitted for convenience of explanation.

  When there are a plurality of objects in the radiation region of the transmission antenna 104, the code signal S is transmitted from the transmission antenna 104 toward a plurality of objects having different relative distances as shown in FIG. 7A as an example. Will be. The code signals S transmitted to a plurality of objects having different relative distances are reflected at different relative distances as shown in FIG. 7B as an example, and received by the receiving antenna 105 with a time difference corresponding to the difference in relative distances. Received as reflected signal R.

  When two reflected signals R are received at a certain time difference, as shown as an example in FIG. 7C, the reflected codes decoded from these reflected signals R with a time difference equal to the time difference are compared with the comparison codes. FIG. 7C shows a reflection code decoded from each of the reflection signals R received with a time difference of 5 chips as an example of a reflection code to be compared with the comparison code when the two reflection signals R are received with a certain time difference. . In FIG. 7C, the reflection code (hereinafter referred to as the previous reflection code) decoded from the previously received reflection signal R and the comparison code all match from the first chip to the n-th chip. The reflection code decoded from the reflection signal R received later (hereinafter referred to as the subsequent reflection code) indicates a case where the first to n-5th chips are compared with the comparison code.

  As shown in FIG. 7C as an example, when all of the first chip to the n-th chip match, the correlation value between the previous reflection code and the comparison code has been described with reference to FIG. 6A. So that it becomes the largest. On the other hand, in the case shown in FIG. 7C, as described with reference to FIG. 6B, the correlation value between the later reflection code and the comparison code is actually considered in addition to the later reflection code. Therefore, a random correlation value is obtained.

  Since the random correlation value between the subsequent reflection code and the comparison code is added to the correlation value between the previous reflection code and the comparison code, the correlation value between the previous reflection code and the comparison code is a random correlation value. Affected by. Accordingly, the timing for notifying the signal processing unit 110 when the correlation value calculated by the matched filter 109 exceeds the threshold value as described later becomes inaccurate, and the relative distance calculated by the signal processing unit 110 as described later. Will also be inaccurate. This is the same when the time elapsed from the time shown in FIG. 7C and the subsequent reflection code matches the comparison code from the first chip to the n-th chip (the reflection code at the tip of the chip shifted). The random correlation value between the reference code and the comparison code affects the correlation value between the reflection code and the comparison code after the chips match).

  Therefore, in the radar apparatus 1 according to the present embodiment, three code signals S are transmitted in succession as described above, and the matched filter 109 according to the present embodiment selects the second of the three consecutive reflection codes. The correlation value between the reflection code and the comparison code is calculated.

  FIG. 8 is a diagram illustrating an example of reflection codes decoded from three consecutive reflection signals R reflected by objects having different relative distances from three consecutive code signals S. FIG. In FIG. 8, among the three consecutive reflected signals R reflected by different objects, three consecutive reflected codes decoded from the previously received three consecutive reflected signals R are used as the previous reflected codes. The three consecutive reflection codes decoded from the three consecutive reflection signals R received later are shown as the subsequent reflection codes.

  FIG. 8 shows a case where the second reflection code and the comparison code included in the previous reflection code all match from the first chip to the n-th chip. The subsequent reflection code shown in FIG. 8 is shifted by 5 chips from the previous reflection code. As shown in FIG. 8 as an example, when the first to n-th chips of the second reflection code included in the previous reflection code all match the comparison code, the second reflection code As described with reference to FIG. 6A, the correlation value between the reflection code and the comparison code is the largest. On the other hand, in the case shown in FIG. 8, among the subsequent reflection codes, the correlation values with the comparison code are calculated for the first and second reflection codes. However, in the case shown in FIG. 8, the first and second reflection codes respectively included in the subsequent reflection codes are shifted from the comparison code and the chip. For this reason, in the case shown in FIG. 8, the correlation value between the first and second reflection codes and the comparison code included in the later reflection code is zero as described with reference to FIG. 6C. A close constant.

  Therefore, in the case shown in FIG. 8, the correlation value calculated by the matched filter 109 is the largest correlation value with the second reflection code included in the previous reflection code and one included in the subsequent reflection code. It is a value obtained by adding a constant correlation value close to zero with the first and second reflection codes. For this reason, the correlation value between the second reflection code and the comparison code included in the previous reflection code is the largest, and the timing at which the threshold value is exceeded is accurate according to the time at which the previous reflection code is received. It's time. This is also the case when the time has elapsed from the time shown in FIG. 8 and the second reflection code and the comparison code included in the subsequent reflection codes all match from the first chip to the n-th chip. (The second correlation code included in the previous reflection code, and the constant correlation value close to zero between the third reflection code and the comparison code match the chip included in the subsequent reflection code. And added to the largest correlation value between the second reflection code and the comparison code).

  The above is the reason why the matched filter 109 according to the present embodiment calculates the correlation value between the code decoded from the second reflected signal R among the three consecutively received reflected signals R and the comparison code. It is an explanation.

  In this embodiment, the matched filter 109 calculates the correlation value between the reflected code decoded from the second reflected signal R among the three consecutively received reflected signals R and the comparison code. As described above, the code signal generation unit 102 notifies the second start timing when the generation of the third code signal S is started and the completion timing when the generation of the third code signal S is completed. In addition, the matched filter 109 according to the present embodiment uses the matched filter 109 to obtain a correlation value between the reflected code and the comparison code decoded from the second reflected signal R among the three consecutively received reflected signals R. In order to calculate, the calculation of the correlation value is started when the notification of the second start timing is received, and the calculation of the correlation value is stopped when the notification of the completion timing is received.

  Here, the propagation speed of the code signal S in the space is sufficiently high, and when generation of the third code signal S is started (substantially the same timing as when transmission from the transmission antenna 104 is started), All the first reflected signals R reflected by all objects in which the first code signal S exists within the measurement range are received by the receiving antenna 105, and these reflected signals R are received almost at the same time. It is assumed that the comparison between the reflection code decoded from 1 and the comparison code has already started from the first chip. FIG. 9A shows, as an example, when there are two objects in the measurement range, transmission of the third code signal S from the transmission antenna 104 is started, and the first one reflected by the two objects, respectively. It is a figure which shows when the reflected signal R of each is received with the receiving antenna 105, respectively.

  Further, the propagation speed of the code signal S in the space is sufficiently high, and when the generation of the third code signal S is completed (substantially the same timing as when the transmission from the transmission antenna 104 is completed), the second Reception of all the second reflected signals R reflected by all the objects existing in the measurement range by the receiving antenna 105 is completed, and from each of these second reflected signals R, respectively. Assume that the calculation of the correlation value when the first chip to the n-th chip of the decoded reflection code are all matched with the first chip to the n-th chip of the comparison code is completed. FIG. 9B shows, as an example, when there are two objects in the measurement range, the transmission of the third code signal S from the transmission antenna 104 is completed, and the second object reflected by the two objects, respectively. It is a figure which shows when the reception of the reflected signal R of has been completed.

  Therefore, as described above, the matched filter 109 according to the present embodiment starts the calculation of the correlation value when the notification of the second start timing is received from the code signal generation unit 102, and By stopping the calculation of the correlation value when the notification is received from the code signal generation unit 102, all the second reflected signals R among the three consecutive reflected signals R reflected by all the objects existing in the measurement range are displayed. It is possible to calculate a correlation value when the first chip to the n-th chip of the reflection code decoded from the reflected signal R are all matched with the first chip to the n-th chip of the comparison code.

  Then, the matched filter 109 notifies the signal processing unit 110 of the timing when the sequentially calculated correlation value exceeds a predetermined threshold value. Here, the threshold value predetermined for the matched filter 109 is the largest correlation value calculated when the first to nth chips of the reflection code and the comparison code all match, It is assumed that the threshold value is determined so as to be distinguishable from the correlation value calculated in the case.

  The signal processing unit 110 calculates the relative distance to the object based on the timing notified from the code signal generation unit 102 and the timing notified from the matched filter 109. More specifically, when receiving the notification of the first start timing, the signal processing unit 110 starts measuring time from zero. That is, the signal processing unit 110 generates the second code signal S among the code signals S generated in succession by the code signal generation unit 102 and transmits the signal from the transmission antenna 104 substantially simultaneously. The elapsed time is counted.

  Next, when the time has elapsed from the first start timing described above and the notification of the second start timing is received, the matched filter 109 starts calculating the correlation value as described above, and determines it in advance. Every time a correlation value exceeding the threshold value is detected, the detected timing is notified to the signal processing unit 110. When the time elapses from the second start timing and the completion timing notification is received from the code signal generation unit 102, the matched filter 109 completes the calculation of the correlation value as described above. The signal processing unit 110 completes the time measurement. Therefore, the signal processing unit 110 generates a second code signal S among the code signals S generated by the code signal generation unit 102 in succession, and performs matching from the time transmitted from the transmission antenna 104. The time until the correlation value exceeding the threshold value is detected by the filter 109, that is, the second code signal S among the code signals S generated in succession by the code signal generation unit 102 is the measurement range. The time until the correlation value between the reflection code and the comparison code decoded by receiving and decoding the reflection signal R reflected by one or more objects existing in the object is maximized may be measured for each object. it can.

  Since the speed at which the code signal S propagates in the space is known, the signal processing unit 110 calculates the relative distance for each object existing in the measurement range based on the known speed and the time measured. It can be calculated and measured.

  In addition, the code signal generation unit 102 according to the present embodiment repeats the generation of three consecutive code signals S at a predetermined time interval, and repeats the above-described calculation of the relative distance according to this repetition. Thereby, the radar apparatus 1 according to the present embodiment can continue the measurement of the relative distance at a predetermined time interval.

  The above is the description of the radar apparatus 1 according to the present embodiment. Next, the flow of processing of the signal processing unit 110 according to the present embodiment will be described with reference to the flowchart shown in FIG.

  In step S <b> 101, the signal processing unit 110 determines whether or not a notification of the first start timing has been received from the code signal generation unit 102. When the signal processing unit 110 determines in step S101 that the notification of the first start timing has been received, the process proceeds to step S102. On the other hand, when the signal processing unit 110 determines in step S101 that the notification of the first start timing has been received, the process of step S101 is repeated.

  In step S102, the signal processing unit 110 starts counting time from zero. When the process of step S102 is completed, the signal processing unit 110 advances the process to step S103.

  In step S <b> 103, the signal processing unit 110 determines whether a notification of timing (timing when the correlation value exceeds the threshold value) has been received from the matched filter 109. When the signal processing unit 110 determines in step S103 that timing notification has been received from the matched filter 109, the process proceeds to step S104. On the other hand, when the signal processing unit 110 determines in step S103 that it has not received a timing notification from the matched filter 109, the signal processing unit 110 proceeds to step S105.

  In step S104, the signal processing unit 110 calculates the relative distance based on the time being measured and the known speed at which the code signal S propagates in space. Specifically, the signal processing unit 110 sets D = V × t, where t is the time being measured, V is the known speed when the code signal S propagates in space, and D is the relative distance to be obtained. The relative distance D is obtained by the calculation represented by the following formula. When the signal processing unit 110 completes the process of step S104, the process proceeds to step S105.

  In step S <b> 105, the signal processing unit 110 determines whether a completion timing notification has been received from the code signal generation unit 102. When the signal processing unit 110 determines in step S105 that a notification of completion timing has been received, the signal processing unit 110 advances the processing to step S106. On the other hand, when the signal processing unit 110 determines in step S105 that the completion timing notification has not been received, the signal processing unit 110 returns the process to step S103.

  In step S106, the signal processing unit 110 completes time measurement. When completing the process of step S106, the signal processing unit 110 repeats the process from step S101.

  In response to the code signal generation unit 102 that repeats the generation of the code signal S at a predetermined time interval as described above by repeating the processing from step S101 after the signal processing unit 110 completes the process of step S106. The calculation of the relative distance can be repeated and continued at a predetermined time interval. Since the signal processing unit 110 repeats the process shown in the flowchart of FIG. 10 at a predetermined time interval, the signal processing unit 110 performs steps S106 to S101 so that the time until the process is completed is the time interval. A process of delaying the timing to return the process to may be further performed.

  The above is the description of the processing flow of the signal processing unit 110 according to the present embodiment. According to the radar apparatus 1 according to the present embodiment, since the three code signals S are generated in succession, the relative distance is calculated without calculating the random correlation value described with reference to FIG. 6B as noise. Therefore, it is possible to reduce the influence of the noise on the correlation value. Further, the radar apparatus 1 according to the present embodiment continuously generates the code signal S and calculates a correlation value at a predetermined timing. Since the configuration for this is a simpler configuration as described with reference to FIG. 1, the radar apparatus 1 for reducing the influence of noise can be provided at a low cost.

  In the first embodiment described above, the code signal generation unit 102 generates the code signal S that is three consecutive. However, the number of consecutive code signals S may be two or four or more. Also good.

  In the first embodiment described above, the correlation value between the second reflection code and the comparison code among the three consecutive reflection codes is calculated. However, as described above, when the code signal generation unit 102 continuously generates four or more code signals S, the correlation between the third and subsequent reflection codes and the comparison code is not the second reflection code. The value must be calculated. In other words, in the present invention, only N or more predetermined N code signals S are generated, and a correlation value obtained by comparing the reflected code decoded from the (N-1) th reflected signal R with the comparison code is calculated. The relative distance may be calculated based on the timing when the correlation value exceeding the threshold value occurs. Then, when N is 4 or more, as described in the first embodiment, the timings described as being notified by the code signal generation unit 102 (first start timing, second start timing, And completion timing) need to be adjusted accordingly.

  In the first embodiment described above, three code signals S are generated in succession, and a correlation value with one comparison code is calculated. However, in another embodiment, one code signal S is generated and transmitted without being continuous, and three reflected codes decoded from the reflected signal R reflected by the target signal S are three consecutive. Even when compared with the comparative code, the same effect as the radar apparatus 1 according to the first embodiment can be obtained.

  FIG. 11 shows two reflections in which the code signal S generated by the code signal generation unit 102 at a predetermined time interval one by one is reflected in two objects having different relative distances from each other within the measurement range. It is a figure which shows an example in the case of comparing the reflective code each decoded from the signal R with three continuous comparison codes.

  As in FIG. 7C, as an example of a reflection code to be compared with a comparison code when two reflected signals R are received with a certain time difference, FIG. 11 shows a reflection decoded from the reflected signal R received with a time difference of 5 chips. The code | symbol is shown. In FIG. 11, the second comparison code among the three consecutive comparison codes and the previous reflection code all match from the first chip to the n-th chip, and the subsequent reflection code Shows a case where the first chip to the n-5th chip are compared with the second comparison code among the three consecutive comparison codes.

  As shown in FIG. 11 as an example, when all of the first chip to the n-th chip match, the correlation value between the previous reflection code and the second comparison code is shown in FIG. 6A. Since it is the same as the relationship between the reflection code and the comparison code, it is the largest. On the other hand, in the case shown in FIG. 11, the correlation value between the subsequent reflection code and the second comparison code is the same as the relationship between the reflection code and the comparison code shown in FIG. . Therefore, in the case shown in FIG. 11, the correlation value calculated by the matched filter 109 is close to zero between the largest value of the previous reflection code and the subsequent reflection code, as in the description with reference to FIG. It is a value obtained by adding a constant correlation value. For this reason, the correlation value between the second reflection code and the comparison code included in the previous reflection code is the largest, and the timing at which the threshold value is exceeded is accurate according to the time at which the previous reflection code is received. It's time. This is the same when the time elapsed from the time shown in FIG. 11A and the subsequent reflection code and the second comparison code all match from the first chip to the n-th chip (the previous one). The correlation value of a constant close to zero between the reflection code and the second and third comparison codes, each of which is shifted from the chip, is obtained by comparing the subsequent reflection code with the second comparison code in which all chips match. Added to the largest correlation value).

  In addition, as described with reference to FIG. 11, when the code signal S is generated one by one without being continuous and the relative distance from the object is calculated and measured, The relative distance must be calculated based on the timing of the peaks produced by comparing with the reflection code.

  As a specific method for the matching filter 109 to recognize the timing of comparing the second comparison code and the reflection code, after the code signal generation unit 102 generates one reflection signal R, An example is a method of notifying the matched filter 109 of the timing at which a period necessary to generate one reflected signal R has elapsed (the same timing as the second start timing described in the first embodiment). In this case, the code signal generation unit 102 generates one reflected signal R, then a period necessary to generate the next reflected signal R elapses, and further generates one reflected signal R. The matched filter 109 is also notified of the timing at which the period necessary for this has elapsed (timing equal to the completion timing described in the first embodiment). When the matched filter 109 receives a notification of timing corresponding to the second start timing from the code signal generation unit 102, the matched filter 109 starts calculation of a correlation value and notification of timing when a peak occurs, and the code signal generation unit 102 When the notification of the timing corresponding to the completion timing is received, the calculation of the correlation value and the notification of the timing at which the peak occurs are completed.

  Then, the signal processing unit 110 calculates the relative distance in a period from the timing corresponding to the second start timing to the timing corresponding to the completion timing.

  Thus, even when the code signal S is generated one by one and compared with three consecutive comparison codes, the same effect as that described in the first embodiment can be obtained.

  Further, as described with reference to FIG. 11, when the code signal S is generated one by one and the relative distance from the object is calculated and measured, the number of comparison codes to be continued is two. Or 4 or more.

  In the above description, the description has been made assuming that the type of code is a PN code. However, the types of codes that can be used in the present invention may be other appropriate types such as M-sequence codes and Gold codes. In addition, the Gold code or the like is not a code for which a constant correlation value close to zero is calculated in the case shown in FIG. 6C as an example, but rather than a random correlation value calculated in the case shown in FIG. 6B as an example. Small value. Therefore, as in the case of the Gold code, if the correlation value calculated in the example shown in FIG. 6C is smaller than the random correlation value calculated in the example shown in FIG. Such types of codes may be used.

  In addition, for example, when the radar apparatus 1 according to the present invention is mounted on a moving body such as an automobile, the object in the above description is considered as other vehicles, pedestrians, and road installations existing around the vehicle. Can do.

  In the first embodiment, when N code signals are generated in succession, a code signal generation unit is used to compare the reflection code decoded from the (N-1) th reflection signal with the comparison code. It is assumed that the matched filter 109 and the signal processing unit 110 advance the processing based on the timing notified from 102 (first start timing, second start timing, and completion timing). However, in another embodiment, when N code signals are generated in succession, in order to compare the reflection code decoded from the (N-1) th reflection signal with the comparison code, the matched filter 109, Alternatively, the signal processing unit 110 recognizes the number of decoded reflection codes, recognizes the period for calculating the correlation value by comparing the N-1th reflection code and the comparison code, and uniquely For example, the relative distance may be calculated based on the timing at which the relative value exceeds the threshold in the recognized period.

  ADVANTAGE OF THE INVENTION According to this invention, the relative distance with a target object can be measured accurately, for example, it can utilize for the radar apparatus etc. which are mounted in moving bodies, such as a motor vehicle.

DESCRIPTION OF SYMBOLS 1 Radar apparatus 101 Reference signal generation part 102 Code signal generation part 103 1st amplification part 104 Transmission antenna 105 Reception antenna 106 2nd amplification part 107 Mixing part 108 LPF
109 matched filter 110 signal processing unit

Claims (2)

Transmitting means for continuously transmitting 3 or more N code signals that are encoded signals;
Receiving means for receiving a reflected signal of the code signal reflected by an object;
Storage means for storing, as a comparison code, the same code as the code used when encoding the code signal transmitted from the transmission means;
Wherein comprising a comparing code, and a measuring means for measuring said N only the object based on the correlation between the decoded code from the reflected signal continuously corresponding to the transmitted said code signal,
The measuring means calculates a correlation value between the comparison code and a code decoded from the reflected signal corresponding to the N-1th code signal among the N code signals transmitted continuously. A radar apparatus that takes a correlation value between the comparison code and a code decoded from the reflected signal corresponding to the N number of code signals transmitted continuously . The radar apparatus according to claim 1, wherein N = 3.

Images