JP4687239B2 - Transmission / reception apparatus and transmission / reception method - Google Patents

Description

  The present invention relates to a radio wave transmission / reception technique, and more specifically, an ECM (Electronic Counter Measurement) transmitted to a target, that is, a radio wave for the purpose of so-called jamming (hereinafter referred to as an ECM wave) is reflected on the target and reflected. It is related with the transmitter / receiver used also as a radar by receiving.

  In the conventional transmission / reception apparatus, the ECM function and the radar function are realized simultaneously by transmitting an ECM wave for the purpose of confusing the radar function of the target and detecting the position of the target based on the received reflected wave. . In such a transmission / reception device, the ECM wave is continuously transmitted toward the target, the reflected wave by the target is received, and the time from the ECM wave and the reflected wave is received, from the place where the transmission / reception device is installed. Calculate the distance to the target.

  By the way, in general, a transmission unit and a reception unit in a transmission / reception apparatus operate in an asynchronous state in which timing synchronization is not established. In this case, in order to obtain the time difference, the correlation between the ECM wave and the reflected wave must be obtained. Therefore, a signal whose amplitude and phase change irregularly or an encoded signal is used as the ECM wave so that a correlation peak does not occur except at the timing coincident with the reflected wave (for example, Patent Document 1). ).

JP 2001-296351 A (0002 stages, FIG. 13)

  Under a situation in which the distance to the target is unknown, it is impossible to know in advance how much delay time the reflected wave reflected by the target is received after transmitting the ECM wave. On the other hand, as described above, in the conventional transmission / reception apparatus, the ECM wave must be continuously transmitted, and the reflected wave is also continuously received. Therefore, the correlation has to be calculated over a long time interval in which the correlation peak does not clearly appear, resulting in a wasteful calculation amount. In addition, when a correlation calculation is performed for a long time, there is a possibility of calculating a correlation with a signal of a portion where irregularity is not sufficient. In this case, there is a problem that a correlation value (so-called side lobe) at a time when a peak should not be originally obtained becomes large and the correlation peak is erroneously detected, resulting in an erroneous calculation distance to the target.

  The present invention has been made to solve the above-described problem. Even when the ECM wave is continuously transmitted in a situation where the distance to the target is unknown, a header is provided for each predetermined section of the ECM wave. The purpose is to reduce the amount of calculation by limiting the calculation interval for the correlation calculation. Another object of the present invention is to accurately calculate the distance to the target object by limiting the calculation interval to reduce the probability of occurrence of a high side lobe.

  The transmission / reception device according to the present invention generates an interference transmission wave from a transmission signal including a predetermined known sequence, generates a reference signal including a predetermined transmission header corresponding to the known sequence from the generated interference transmission wave, and outputs the reference signal And transmitting means for detecting the transmission header from the generated reference signal and outputting a first timing signal; transmitting the disturbing transmission wave to the target; and receiving a reflected wave from the target An antenna and a reception means for generating and outputting a reception signal including a predetermined reception header from the received reflected wave, and detecting the reception header from the generated reception signal and outputting a second timing signal; The reference signal and the received signal are accumulated in a storage means, and the second timing is determined from a time that is a predetermined time before the time at which the first timing signal is input. Correlation processing means for generating a correlation value by performing correlation processing between the received signal and the reference signal accumulated up to the time when a ming signal is input, and detection means for detecting a peak of the generated correlation value And calculating the distance to the target based on the time until the peak of the correlation value is detected.

  According to the present invention, since a header is provided for each fixed section of the ECM wave and the inside of the header is limited as a calculation section, even when the ECM wave is continuously transmitted in a situation where the distance to the target is unknown. The amount of calculation can be reduced. Further, by limiting the calculation interval, it is possible to accurately calculate the distance to the target object while suppressing the probability that a high side lobe will occur.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram illustrating a configuration of a transmission / reception device 1 according to the first embodiment. In FIG. 1, a transmission unit 2 that is a transmission unit continuously generates an ECM wave 2 a that is an interfering transmission wave with a transmission header embedded at a predetermined time interval, and transmits the ECM wave 2 a toward the target 4 from the transmission antenna 3. . On the other hand, a digital reference signal 2 b that is a reference signal and a transmission timing signal 2 c that is a first timing signal are passed from the transmission unit 2 to the correlation processing unit 5.

  When the ECM wave 2a reaches the target 4, the radar function of the target 4 is confused. Specifically, for example, when the radar of the target 4 performs distance measurement, an erroneous distance is detected, or the target 4 cannot detect the radar reflected wave by the high-power ECM wave 2a. The ECM wave 2 a is reflected by the target 4, and is received by the receiving antenna 6 when the reflected wave returns to the transmitting / receiving device 1. In the first embodiment, the transmission antenna 3 and the reception antenna 6 are distinguished from each other. However, this is not necessarily a different antenna, and a common antenna can also be used.

  The received reflected wave 7a is transferred to the receiving unit 7 which is a receiving means, and a reception header included in the reflected wave 7a is detected. The reflected wave 7 a is converted by the receiving unit 7, and the digital reception signal 7 b that is the converted reception signal and the reception timing signal 7 c that is the second timing signal that is the timing information of the reception header are correlation processing means. Passed to part 5. The correlation processing unit 5 obtains a correlation value between the digital reference signal 2b and the digital reception signal 7b based on the transmission timing signal 2c and the reception timing signal 7c, and sends the correlation signal 5a that is the correlation value to the peak value detection unit 8 that is a detection means. hand over. The peak value detector 8 detects the peak of the correlation signal 5a, and calculates the distance between the transmission / reception device 1 and the target 4 using the time until the peak appears.

  Next, the operation of the transmission / reception device 1 will be described. FIG. 2 is a configuration diagram illustrating a configuration example of the transmission unit 2. In the transmission unit 2, the transmission signal generation unit 21 creates a transmission signal 2 e having a known sequence 2 d having a predetermined time length Ts every predetermined time interval T. The transmission signal 2e is a digital signal having a value of 0 or 1, and a configuration example is shown in FIG. As shown in FIG. 3A, a known sequence 2d having a time length Ts is inserted into the transmission signal 2e every predetermined time T. For example, the M series is used as the known series 2d, and all the known series 2d are the same M series. On the other hand, the portion other than the known sequence 2d may be any sequence, but an irregular sequence is usually used so that transmission power is distributed over the entire frequency band to be transmitted.

  From the transmission signal generation unit 21, the known sequence 2 d is passed to the transmission header detection unit 22. The transmission signal 2e is sent from the transmission signal generator 21 to the D / A converter 23 and converted into an analog transmission signal 2f. The converted analog transmission signal 2f is transferred to the high frequency converter 24, and is converted to a high frequency in the gigahertz band to create an ECM wave 2a. The ECM wave 2 a is passed to the transmission antenna 3 as described above and transmitted toward the target 4.

  On the other hand, the ECM wave 2 a is passed to the transmission antenna 3, branched at the output of the high frequency converter 24, and passed to the low frequency converter 25. The low-frequency conversion unit 25 converts the frequency of the ECM wave 2a in the gigahertz band into the baseband, and creates an analog reference signal 2g. The analog reference signal 2g is transferred to the A / D converter 26 and converted into a digital reference signal 2b. The digital reference signal 2b is passed to the correlation processing unit 5 and is also passed to the transmission header detection unit 22 to detect a transmission header corresponding to the known sequence 2d.

  FIG. 4A shows a block diagram of the transmission header detection unit 22. In FIG. 4A, the known sequence 2 d passed from the transmission signal generation unit 21 is passed to the header creation unit 221. The header creation unit 221 creates a digital signal corresponding to an ideal envelope when the known sequence 2d is received, that is, the header 2h, and passes it to the correlation unit 222. On the other hand, the digital reference signal 2 b passed from the A / D conversion unit 26 is passed to the correlation unit 222. The correlation unit 222 performs correlation calculation between the digital reference signal 2b and the header 2h, and the correlation value 2i is passed to the peak detection unit 223. Here, since the header 2h is a digital signal corresponding to an ideal envelope when the known sequence 2d is received, if the internal noise in the transmission unit 2 is ignored, the header 2h becomes the known sequence 2d included in the digital reference signal 2b. It is the same sequence as the corresponding part, that is, the transmission header.

  (A) of FIG. 5 is a graph which shows the time change of the correlation value 2i which the correlation part 222 outputs. When the correlation calculation between the digital reference signal 2b and the header 2h is performed by the correlator 222, the correlation value 2i becomes a high correlation value 2i at time Tm0 when the transmission header and the header 2h match as shown in FIG. Output. On the other hand, since the digital reference signal 2b and the header 2h do not match except for the time Tm0, only a low correlation value can be obtained. That is, in the portion other than the transmission header in the digital reference signal 2b, an irregular sequence is used as described above. Therefore, the side lobe that is a correlation value other than the time Tm0 in FIG. 5A is compared with the peak value. Can be kept low.

  The correlation value 2i is passed to the peak detector 223. The peak detector 223 outputs a transmission timing signal 2c, assuming that a correlation peak is detected when the correlation value 2i exceeds a predetermined threshold value. Specifically, when the correlation value 2i increases beyond the threshold value TH0 in FIG. 5A, it is determined that a correlation peak has been detected, and the transmission timing as shown in FIG. The signal 2c is output. The transmission timing signal 2c is a digital logic signal, which is normally L logic. However, when the correlation value 2i exceeds TH0, the transition to H logic is detected for one period of the operation clock and a correlation peak is detected The correlation processing unit 5 is notified. Therefore, in the example shown in FIG. 5, the correlation processing unit 5 determines that a transmission header has been detected at a position corresponding to the time Tm0 of the digital reference signal 2b.

  Next, the operation of the receiving unit 7 will be described. FIG. 6 is a configuration diagram illustrating a configuration example of the receiving unit 7. In the receiving unit 7, the reflected wave 7 a passed from the receiving antenna 6 is passed to the low frequency converting unit 71. Similarly to the low frequency conversion unit 25 of the transmission unit 2, the low frequency conversion unit 71 performs frequency conversion of the reflected wave 7a in the gigahertz band to the baseband, and creates an analog reception signal 7d. The analog reception signal 7d is transferred to the A / D converter 72 and converted into a digital reception signal 7b. The digital reception signal 7b is passed to the correlation processing unit 5 and also to the reception header detection unit 73 to detect the reception header. Also, the known sequence 2 d passed from the transmission unit 2 is passed to the reception header detection unit 73.

  FIG. 4B shows a block diagram of the reception header detection unit 73. In FIG. 4B, the known sequence 2 d passed from the transmission unit 2 is passed to the header creation unit 731. The header creation unit 731 creates a digital signal corresponding to an ideal envelope when the known sequence 2 d is received, that is, a header 7 e, and passes it to the correlation unit 732. The header 7e is equivalent to the header 2h in the transmission unit 2. On the other hand, the digital reception signal 7 b passed from the A / D conversion unit 72 is passed to the correlation unit 732. The correlation unit 732 performs correlation calculation between the digital reception signal 7 b and the header 7 e, and the correlation value 7 f is passed to the peak detection unit 733. Here, since the header 7e is a digital signal corresponding to an ideal envelope when the known sequence 2d is received, the internal noise in the transmission / reception device 1 and the noise added during the round trip to the target 4 are ignored. The portion corresponding to the known sequence 2d included in the digital reception signal 7b, that is, the same sequence as the reception header.

  FIG. 7A is a graph showing the temporal change of the correlation value 7 f output from the correlation unit 732. When the correlation operation between the digital reception signal 7b and the header 7e is performed by the correlation unit 732, the correlation value 7f is a high correlation value 7f at time Tm1 when the reception header and the header 7e match as shown in FIG. Output. On the other hand, since the digital received signal 7b and the header 7e do not match at times other than the time Tm1, only a low correlation value can be obtained. That is, since the irregular sequence is used as described above in the portion other than the reception header in the digital reception signal 7b, the side lobe that is a correlation value other than the time Tm1 in FIG. 7A is compared with the peak value. Can be kept low. However, since irregularity is disturbed by internal noise of the transmission / reception device 1 or noise added during a round trip between the transmission / reception device 1 and the target 4, when compared with the correlation value 2 i in FIG. The height of the side lobe at the correlation value 7f is generally high.

  The correlation value 7f is passed to the peak detector 733. The peak detector 733 outputs a reception timing signal 7c, assuming that a correlation peak is detected when the correlation value 7f exceeds a predetermined threshold value. Specifically, when the correlation value 7f increases beyond the threshold value TH1 in FIG. 7A, it is determined that a correlation peak has been detected, and the reception timing as shown in FIG. The signal 7c is output. The reception timing signal 7c is a digital logic signal and is usually L logic. However, when the correlation value 7f exceeds TH1, the transition to H logic is detected for one period of the operation clock, and a correlation peak is detected. The correlation processing unit 5 is notified. Accordingly, in the case of the example shown in FIG. 7, the correlation processing unit 5 determines that a reception header has been detected at a position corresponding to the time Tm1 of the digital reception signal 7b.

  The correlation processing unit 5 receives the digital reference signal 2b and the transmission timing signal 2c from the transmission unit 2. On the other hand, a digital reception signal 7b and a reception timing signal 7c are passed from the reception unit 7. FIG. 8 is a configuration diagram showing the configuration of the correlation processing unit 5. In FIG. 8, the digital reference signal 2 b and the digital reception signal 7 b are passed to the determination unit 51. The determination unit 51 determines the code of the digital reference signal 2b and creates the reference sequence 5b. On the other hand, the determination unit 51 determines the code of the digital reception signal 7b and creates a reception sequence 5c. That is, the reference sequence 5b and the reception sequence 5c are sequences for which codes are determined, and are 0 or 1 code strings.

  The reference sequence 5b and the reception sequence 5c are respectively input to the memory 52 that is a storage unit. When the transmission timing signal 2c and the reception timing signal 7c are L logic, the memory 52 is assumed to store the reference sequence 5b and the reception sequence 5c for the past Ts time. That is, if the Ts time corresponds to N bits, the memory 52 always stores the reference sequence 5b and the reception sequence 5c of the past N bits from the present time.

  When the transmission timing signal 2c transitions from the L logic to the H logic, the memory 52 starts accumulating the reference sequence 5b and the reception sequence 5c that are newly passed while storing the accumulated past N bits. Next, when the reception timing signal 7c transitions from the L logic to the H logic, the accumulation of the reference sequence 5b and the reception sequence 5c is stopped. When the accumulation is stopped, the memory 52 passes the accumulated reference sequence 5b and received sequence 5c to the correlation unit 53 as a reference storage sequence 5d and a received storage sequence 5e, respectively. The correlation unit 53 fixes the received storage sequence 5e, slides the reference storage sequence 5d in time, performs correlation processing, and outputs a correlation signal 5a. When the correlation signal 5a is passed to the peak value detection unit 8 and exceeds a predetermined threshold value TH2, it is determined that the reference storage sequence 5d and the reception storage sequence 5e match, and based on the time difference between these sequences, The distance from the transmission / reception device 1 to the target 4 is calculated.

  A method for calculating the distance from the transmission / reception device 1 to the target 4 based on the data stored in the memory 52 will be described below. FIG. 9 is a timing chart showing the reference sequence 5b, the transmission timing signal 2c, the reception sequence 5c, and the reception timing signal 7c. As described above, the memory 52 stores the reference sequence 5b and the reception sequence 5c from the past by N bits corresponding to the Ts time. Therefore, when the transmission timing signal 2c transitions from the L logic to the H logic at time T1 in FIG. 9, the reference sequence 5b and the reception sequence 5c after T0, which is the past time from T1 to Ts, are stored in the memory 52. When the reception timing signal 7c transitions from the L logic to the H logic at time T2, the memory 52 stops storing. Therefore, the reference sequence 5b and the reception sequence 5c from time T0 to time T2 are eventually stored in the memory 52.

  Correlation unit 53 is supplied with reference sequence 5b and reception storage sequence 5e which are reference sequence 5b and reception sequence 5c from time T0 to time T2 in FIG. 9, and performs correlation calculation. FIG. 10 is a diagram for explaining a state of correlation calculation in the correlation unit 53. That is, as shown in FIG. 10A, the reception storage sequence 5e is fixed, and the correlation signal 5a is obtained while sliding the reference storage sequence 5d bit by bit in the backward direction indicated by the arrow. As a result of shifting the reference storage sequence 5d in the direction of the arrow, the portion that does not overlap with the reception storage sequence 5e, that is, the sequence indicated by the broken line in FIG. 10B is indicated by a chain line in FIG. As shown, it is added to the previous part in time so that there is no excess or deficiency of the sequence. When sliding in this way, in the case shown in FIG. 10C, that is, when the position of the portion corresponding to the reception header of the reception storage sequence 5e matches the position of the portion corresponding to the transmission header of the reference storage sequence 5d. A high correlation signal 5a can be obtained.

  FIG. 11 shows the time change of the correlation signal 5a when the correlation signal 5a is obtained while sliding the reference storage sequence 5d as described in FIG. In FIG. 11, the horizontal axis represents the time when the reference memory sequence 5d is shifted, and the vertical axis represents the correlation signal 5a. As shown in FIG. 11, a correlation peak is obtained when the time Td corresponding to (c) in FIG. 10 is shifted. The peak value detector 8 detects the correlation peak of the correlation signal 5a and obtains the time until the correlation peak is obtained. In the case shown in FIG. 11, the peak value detection unit 8 determines that a correlation peak has been detected when the correlation signal 5a increases beyond a predetermined threshold value TH3, and the time Td until the correlation peak is detected. Ask for. Then, the distance D from the transmission / reception device 1 to the target 4 is calculated based on the time Td. Specifically, assuming that the round trip time from when the ECM wave 2a radiated from the transmitting antenna 3 is reflected by the target 4 until the reflected wave 7a is received by the receiving antenna 6 is Td, the electromagnetic wave is applied to Td. Multiplying the propagation velocity v, the distance D is obtained from the equation D = (Td × v) / 2.

  As described above, in the first embodiment, the transmission header detection unit 22 and the reception header detection unit 73 in the transmission unit 2 and the reception unit 7 are respectively transmitted from the ECM wave 2a and the reflected wave 7a including the header at intervals. By detecting the transmission header and the reception header respectively, and by performing the correlation calculation by limiting the interval for performing the correlation calculation based on the detected positions of the transmission header and the reception header, the correlation calculation in the portion where the correlation peak does not appear is avoided. And the effect of reducing the amount of calculation can be obtained. In addition, as a result of avoiding the correlation calculation in the portion where the correlation peak does not appear, the possibility that a high side lobe is generated can be reduced, and the possibility of erroneously calculating the distance to the target 4 by detecting an erroneous correlation peak. Can be obtained.

  In the above description, the correlation processing unit 5 performs the correlation calculation only on one set of transmission header and reception header shown in FIG. 9, but this is not necessarily limited to only one set of transmission header and reception header. This is not always done. Usually, as shown in FIG. 3, since a plurality of transmission headers and reception headers are included in the transmission / reception signal, a correlation calculation is performed for each of the plurality of sets of transmission headers and reception headers to obtain a time Td. The distance d to the object 4 may be obtained. When the correlation calculation is performed for each of a plurality of sets of headers, these sequences are continuously accumulated without stopping the accumulation of the reference sequence 5b and the reception sequence 5c in the memory 52 at T2 shown in FIG. On the other hand, the reference storage sequence 5d and the reception storage sequence 5e from T0 to T2 are passed from the memory 52 to the correlation unit 53 for each of a plurality of sets of headers. As described above, the distance d is obtained for each of a plurality of sets of headers, the distance d is averaged, and the distance D from the transmission / reception device 1 to the target 4 is calculated, thereby obtaining an effect of reducing errors by averaging. .

  In the above description, the known series 2d provided in the transmission signal 2e for each time interval T in the transmission signal generation unit 21 has been described as being the same series, but this is not necessarily the same series. Good. For example, since there is not necessarily one M sequence having the sequence length N, the distance D to the target 4 can be obtained by the same process even when different M sequences are applied. By applying different known sequences 2d, the accurate distance D can be obtained even when the round trip time Td exceeds the time interval T because the target 4 exists at a long distance.

  Further, in the above description, the correlation signal 5a is obtained while the reception storage sequence 5e is fixed by the correlation unit 53 of the correlation processing unit 5 and the reference storage sequence 5d is slid, but the reception storage sequence 5e is not necessarily fixed. Absent. The same effect can be obtained even when the correlation signal 5a is obtained while the reference storage sequence 5d is fixed and the reception storage sequence 5e is slid.

Embodiment 2. FIG.
In the first embodiment, it has been described that the reference sequence 5b and the reception sequence 5c stored in the memory 52 are transferred to the correlation unit 53 in real time based on the transmission timing signal 2c and the reception timing signal 7c to perform correlation processing. Here, since the correlation processing in the correlation unit 53 generally has a large amount of calculation, when the signal speed is high, parallel processing or the like is required and the hardware scale increases.

  In the second embodiment, the memory 52 does not pass the reference storage sequence 5d and the reception storage sequence 5e to the correlation unit 53 in real time. That is, the reference sequence 5b and the reception sequence 5c having a predetermined time length are collectively stored using the large-capacity memory 52, and the reference storage sequence 5d and the reception storage sequence 5e necessary for the correlation processing are stored at a low speed. To pass to

  The configuration of the transmission / reception apparatus 1 in the second embodiment is the same as that in FIG. 1 of the first embodiment, and the configurations of the transmission unit 2 and the reception unit 7 are also the same as those in FIGS. 2 and 6 in the first embodiment. The operation of the transmitting / receiving apparatus 1 according to the second embodiment is as follows: the transmitting antenna 3 radiates the ECM wave 2a, the receiving unit 7 receives the reflected wave 7a, and a predetermined signal is passed to the correlation processing unit 5. Since it is the same as that of Embodiment 1, description is abbreviate | omitted.

  In the second embodiment, the high-speed reference sequence 5b and the reception sequence 5c are stored in the memory 52 of the correlation processing unit 5 in batches by a predetermined length. The memory 52 also stores a transmission timing signal 2 c and a reception timing signal 7 c passed from the transmission unit 2 and the reception unit 7. Then, based on the stored transmission timing signal 2c and reception timing signal 7c, the reference storage sequence 5d and the reception storage sequence 5e necessary for the correlation processing are transferred to the correlation unit 53 at a low speed.

  A timing chart of the reference sequence 5b, the transmission timing signal 2c, the reception sequence 5c, and the reception timing signal 7c stored in the memory 52 is shown in FIG. As shown in FIG. 12, the memory 52 collectively stores these sequences and signals for a predetermined time length TL. First, as in the first embodiment, the reception timing signal 7c changes from the L logic to the H logic from the time T01 which is Ts time before the time T11 when the transmission timing signal 2c changes from the L logic to the H logic. The reference sequence 5b and the reception sequence 5c up to the transition time T21 are passed to the correlation unit 53 as the reference storage sequence 5d and the reception storage sequence 5e. Similarly to the first embodiment, the correlation signal 5a is obtained by the correlation unit 53, and the distance d from the transmission / reception device 1 to the target 4 is obtained based on the correlation signal 5a.

  Next, the reference sequence 5b from the time T02 that is Ts time before the time T12 at which the transmission timing signal 2c changes from the L logic to the H logic and the time T22 at which the reception timing signal 7c changes from the L logic to the H logic, The reception sequence 5c is transferred to the correlation unit 53, and the distance d is obtained based on the correlation signal 5a obtained by the correlation processing. As described above, in the second embodiment, necessary sequences are sequentially sent to the correlation unit 53 based on the reference sequence 5b, the transmission timing signal 2c, the reception sequence 5c, and the reception timing signal 7c that are stored in the memory 52 at once. A distance d is determined. Note that, after obtaining the distance d a plurality of times, the averaging process is performed to calculate the distance D from the transmission / reception device 1 to the target 4 as in the first embodiment.

  As described above, according to the second embodiment, the memory 52 collectively accumulates high-speed sequences and signals, while sending necessary sequences to the correlation unit 53 by sending them at a low speed. The correlation processing speed of 53 is low. For this reason, in addition to the effects of the first embodiment, parallel processing or the like is not necessary, and the hardware scale can be reduced.

Embodiment 3
In the second embodiment, as in the first embodiment, it is assumed that the memory 52 of the correlation processing unit 5 passes the reference sequence 5b and the received sequence 5c between time T01 and time T21 in FIG. explained. However, it is not necessarily limited to between time T01 and time T21. In Embodiment 3, the reference sequence 5b and the reception sequence 5c between successive transmission timing signals 2c shown in FIG. In this case, as in the first embodiment, the correlation unit 53 fixes the received storage sequence 5e and slides the reference storage sequence 5d backward in time to obtain the correlation signal 5a. When the correlation signal 5a exceeds the predetermined threshold value TH3 shown in FIG. 11 of the first embodiment, instead of obtaining the correlation peak after sliding the reference storage sequence 5d to the end, as described using FIG. If a correlation peak is detected at Td, Td may be obtained.

  Further, in this case, the correlation signal 5a may be obtained by sliding the reference storage sequence 5d backward in time rather than sliding backward in time. FIG. 13 shows a configuration diagram of the correlation processing unit 5 in this case. FIG. 13 is a diagram corresponding to FIG. 8 of the first embodiment, and the same parts as those in FIG. FIG. 13 differs from FIG. 8 in that the transmission timing signal 2 c and the reception timing signal 7 c are also passed to the correlation unit 53.

  As described above, the reference sequence 5b and the reception sequence 5c between time T01 and time T02 are passed to the correlation unit 53. The correlator 53 determines which one of the reference storage sequence 5d and the reception storage sequence 5e is fixed according to the temporal relationship between the transmission timing signal 2c and the reception timing signal 7c, and performs correlation processing.

  A method of determining a sequence to be fixed when performing correlation processing will be described with reference to FIG. FIG. 14A is a timing chart showing the transmission timing signal 2c and the reception timing signal 7c. As shown in FIG. 14A, the time T21 at which the reception timing signal 7c transitions from L logic to H logic is greater than the timing T12 at which the transmission timing signal 2c after T21 transitions from L logic to H logic. If the transmission timing signal 2c before T21 is close to the timing T11 at which the transition from the L logic to the H logic is close, the relationship between the reference storage sequence 5d and the reception storage sequence 5e is as shown in (b) of FIG. For this reason, the reference memory sequence 5d and the received storage sequence 5e can be matched in header position as shown in FIG. 14C by shifting the reference memory sequence 5d backward in time as indicated by an arrow. The peak of the signal 5a can be detected and the time Td can be obtained.

  On the other hand, as shown in FIG. 14D, if the time T21 is closer to the time T12 than the time T11, the relationship between the reference storage sequence 5d and the reception storage sequence 5e is as shown in FIG. Yes. For this reason, the reference memory sequence 5d and the received storage sequence 5e can be matched in header position as shown in FIG. 14 (f) by shifting the reference memory sequence 5d forward in time indicated by an arrow. The peak of the signal 5a is detected, the time T-Td is obtained, and Td can be obtained from the known T. With such an operation, in the third embodiment, the time length for sliding the reference memory sequence 5d can be reduced, and the correlation processing time required to obtain the time Td can be shortened.

Embodiment 4 FIG.
In the first embodiment, it has been described that the correlation processing unit 5 determines the codes of the digital reference signal 2b and the digital reception signal 7b by the determination unit 51 and stores them in the memory 52, and then performs the correlation calculation by the correlation unit 53. However, the correlation calculation is not always necessary. In the fourth embodiment, the transmission header and the reception header are detected by the transmission header detection unit 22 in the transmission unit 2 and the reception header detection unit 73 in the reception unit 7, respectively. The distance to the target 4 is calculated from the time interval.

  FIG. 15A shows a configuration diagram of the transmission / reception device 1 according to the fourth embodiment. FIG. 15A is a diagram corresponding to FIG. 1 of the first embodiment. The same parts as those in FIG. 15A differs from FIG. 1 in that a distance calculation unit 9 is provided instead of the correlation processing unit 5 and the peak value detection unit 8 is omitted. The operation of the transmission / reception device 1 in the fourth embodiment is the same as that in the first embodiment until the transmitting antenna 3 radiates the ECM wave 2a and the receiving unit 7 receives the reflected wave 7a, and thus the description thereof is omitted. .

  In the fourth embodiment, only the transmission timing signal 2c is passed from the transmission unit 2 to the distance calculation unit 9, and the digital reference signal 2b is not passed. Further, only the reception timing signal 7c is passed from the receiving unit 7 to the distance calculating unit 9, and the digital received signal 7b is not passed. The distance calculation unit 9 measures the time from when the transmission timing signal 2c is passed to when the reception timing signal 7c is passed. Specifically, as shown in FIG. 15B, when the transmission timing signal 2c transitions from L logic to H logic at time t0, counting by the counter is started. When the reception timing signal 7c transitions from the L logic to the H logic at time t1, the counting ends. If the counted value and the operation clock are used, a time Td from time t0 to time t1 can be obtained. Since Td corresponds to the round trip time until the ECM wave 2a is radiated from the transmitting antenna 3 and the reflected wave 7a is received by the receiving antenna 6, the distance D is obtained based on Td and the propagation speed of the electromagnetic wave.

  As described above, in the second embodiment, the round trip time Td can be obtained only by counting with a simple counter by providing the distance calculation unit 9 instead of the correlation processing unit 5. For this reason, in addition to the effect in Embodiment 1, the effect that a hardware scale is reduced and further power consumption reduction is implement | achieved can be acquired.

Embodiment 5 FIG.
In the first embodiment, the case where the lengths of the reception headers included in the digital reception signal 7b are all constant, that is, the case where the sequence lengths of the known sequences 2d are all equal has been described. By the way, when the ECM wave 2a is reflected by the target 4, the electromagnetic wave is scattered and diffracted due to the size and material of the target 4, and the information contained in the reception header varies due to interference between the electromagnetic waves. However, the received header detection unit 73 may not be able to detect the received header. Therefore, in the fifth embodiment, the length of the known sequence 2d included in the transmission signal 2e is controlled according to the change in information when the ECM wave 2a is reflected by the target 4. Note that the phase of the reception header is taken as an example of information included in the reception header, and will be described below.

  FIG. 16 is a configuration diagram illustrating the configuration of the transmission / reception device 1 according to the fifth embodiment, and corresponds to FIG. 1 according to the first embodiment. In FIG. 16, the same parts as those in FIG. In FIG. 16, unlike FIG. 1, the header non-detection signal 7 g is passed from the reception unit 7 to the transmission unit 2.

  Next, the operation of the transmission / reception device 1 in the fifth embodiment will be described. The operation of the transmission / reception apparatus 1 in the fifth embodiment is the same as that in the first embodiment until the transmitting antenna 3 radiates the ECM wave 2a and the reception unit 7 receives the reflected wave 7a, and thus the description thereof is omitted. . Next, FIG. 17A shows a configuration diagram illustrating the configuration of the receiving unit 7 according to the fifth embodiment. FIG. 17A corresponds to FIG. 6 of the first embodiment. In FIG. 17A, the same parts as those in FIG. 17A, unlike FIG. 6, the header detector 74 outputs a header non-detection signal 7g.

  FIG. 17B shows a configuration diagram of the header detection unit 74. FIG. 17B corresponds to FIG. 4B of the first embodiment. In FIG. 17B, the same parts as those in FIG. 4B are denoted by the same reference numerals, and description thereof is omitted. The operation of the header creation unit 731 creating the header 7e and the correlation unit 732 obtaining the correlation value 7f in FIG. 17B is the same as in the first embodiment, and thus the description thereof is omitted. The peak detector 741 of the header detector 74 outputs the reception timing signal 7c when the correlation value 7f exceeds a predetermined threshold value TH1 as in the first embodiment. On the other hand, if the correlation value 7f does not exceed the threshold value TH1 after the predetermined time interval Tp (Tp> T) has elapsed after the reception timing signal 7c is output once, It is determined that detection of the received header has failed, and a header non-detection signal 7g is output. The header non-detection signal 7g is passed to the transmission unit 2.

  FIG. 18 is a configuration diagram showing the configuration of the transmission unit 2 in the fifth embodiment. FIG. 18 corresponds to FIG. 2 of the first embodiment. In FIG. 18, the same parts as those in FIG. Unlike FIG. 2, FIG. 18 includes a header length correction unit 27. The header non-detection signal 7 g passed from the peak detection unit 741 of the reception unit 7 is passed to the header length correction unit 27. Upon receiving the header non-detection signal 7g, the header length correction unit 27 passes an instruction to increase the length of the known sequence 2d to the transmission signal generation unit 21 by the header length control signal 2j. That is, if the sequence length of the known sequence 2d before the instruction is N, the sequence length of the known sequence 2d in the transmission signal 2e is N + α (α: natural number) when the instruction is given.

  FIG. 19 is a diagram for explaining the effect when the sequence length of the known sequence 2d is changed from N to N + α. Now, it is assumed that the phase of the reflected wave 7a fluctuates as shown in the graph of FIG. In this case, since the phase of the reflected wave 7a rotates in the range R in FIG. 19, when the sequence length of the known sequence 2d is N, the phases of all the received headers indicated by hatching are rotated. In this case, even if the header detection unit 74 performs correlation calculation between the digital reception signal 7b and the header 2h, a high correlation peak cannot be obtained because the phase of the reception header is rotated. Therefore, the header detector 74 outputs the header non-detection signal 7g.

  Next, when the sequence length of the known sequence 2d is increased to N + α by the header non-detection signal 7g, the reception header exists beyond the range R as shown in FIG. . In this case, phase rotation does not occur for reception headers not included in the range R. Therefore, if the header detection unit 74 performs correlation calculation between the digital reception signal 7b and the header 2h, a correlation peak can be obtained. Accordingly, the reception timing signal 7c is output from the header detection unit 74.

  As described above, according to the fifth embodiment, the phase of the reception header in the digital reception signal 7b can be changed by making the sequence length of the known sequence 2d transmitted according to the detection status of the reception header variable. Even if it fluctuates, the amount of information in the received header can be increased, and the detection probability of the received header can be improved.

  In the above description, it has been described that the sequence length of the known sequence 2d is increased when the header non-detection signal 7g is input. Conversely, when the reception header is detected, the sequence length of the known sequence 2d is decreased. Control may be performed. For example, when the reception header is continuously detected a predetermined number of times, an instruction to shorten the sequence length of the known sequence 2d by the header length control signal 2j is passed to the transmission signal generation unit 21. By such an operation, the portion corresponding to the transmission header in the ECM wave 2a is reduced, so that the interference performance of the ECM wave 2a can be improved.

  In the above description, the case where the feature of the reception header is the phase has been described as an example, but this is not necessarily limited to the phase. For example, the amplitude or frequency in the digital reception signal 7b may be considered as a feature of the header. The case where the amplitude and frequency fluctuate is the same as described above. In this case as well, the detection probability of the header can be increased by increasing the length of the known sequence 2d.

Embodiment 6 FIG.
In the fifth embodiment, the case has been described in which only the length of the known sequence 2d to be transmitted is controlled according to the change in information of the reception header when the ECM wave 2a is reflected by the target 4. In the sixth embodiment, the transmission frequency of the part corresponding to the transmission header in the ECM wave 2a is changed to a frequency different from the transmission frequency of the part other than the transmission header. By changing the transmission frequency of the transmission header part, that is, by changing the wavelength of the part, the reflection characteristics of the electromagnetic wave change.

  The reflection characteristics of electromagnetic waves differ depending on, for example, the size and shape of the target, but in general, the wavelength must be the same as or shorter than the size of the target in order to reflect the electromagnetic waves. For example, when an aircraft or the like is considered as a target, if the electromagnetic wave having a wavelength of about several tens of meters is used for a small aircraft of about several meters, the receiver 7 may not be able to detect the header. In the sixth embodiment, as in the fifth embodiment, when the header is not detected within a predetermined time, the ECM wave 2a is reflected by the target 4 by changing the transmission frequency of the header portion.

  The configuration of transmission / reception apparatus 1 in the sixth embodiment is the same as the configuration of transmission / reception apparatus 1 in the fifth embodiment. The operation of the transmission / reception apparatus 1 in the sixth embodiment is the same as that of the transmission / reception apparatus 1 in the fifth embodiment until the transmission antenna 3 radiates the ECM wave 2a and the reception unit 7 receives the reflected wave 7a. Therefore, explanation is omitted. Next, with respect to the receiving unit 7 in the sixth embodiment, as in the fifth embodiment, when the correlation value 7f does not exceed the threshold value TH1, the header non-detection signal 7g is determined as the header detection failure. Output. The header non-detection signal 7g is passed to the transmission unit 2 as in the fifth embodiment.

  FIG. 20 is a configuration diagram showing the configuration of the transmission unit 2 in the sixth embodiment. FIG. 20 corresponds to FIG. 17 of the fifth embodiment and FIG. 2 of the first embodiment. In FIG. 20, the same parts as those in FIG. 2 or FIG. In FIG. 20, unlike FIG. 17, a header wavelength correction unit 28 is provided. The header non-detection signal 7g passed from the receiving unit 7 is passed to the header length correcting unit 27, branched, and also passed to the header wavelength correcting unit 28. When the header wavelength correction unit 28 receives the header non-detection signal 7g, the header wavelength correction unit 28 passes to the high frequency conversion unit 24 an instruction to increase the frequency when the analog transmission signal 2f is converted to the ECM wave 2a by the header wavelength control signal 2k. That is, if the transmission frequency of the header part in the ECM wave 2a before the instruction is f0 (GHz) and the wavelength at this time is λ0 meters, the transmission frequency of the header part in the ECM wave 2a is given by the instruction. Is f1 (GHz) (f0 <f1), and the wavelength is λ1 meter (λ0> λ1).

  When the wavelength of the header portion in the ECM wave 2a is shortened from λ0 to λ1 by the header non-detection signal 7g, the reflection characteristic at the target 4 changes. That is, the reflected wave 7a can be obtained by using the short wavelength λ1 even for the small target 4 that is not reflected by the electromagnetic wave having the conventional wavelength λ0.

  As described above, according to the sixth embodiment, the wavelength of the header portion can be varied according to the detection status of the header, so that the reflected wave can be reflected even when the size of the target 4 is small. The effect of obtaining 7a is obtained.

Embodiment 7 FIG.
In the first embodiment, the header is detected in both the transmission unit 2 and the reception unit 7, and the correlation processing unit 5 performs correlation processing based on the transmission timing signal 2c and the reception timing signal 7c that are timing information of the detected header. Explained. On the other hand, in Embodiment 7, the reception unit 7 does not detect the header, and the correlation processing unit 5 performs the correlation process based only on the transmission timing signal 2c in the transmission unit 2.

  FIG. 21 shows the configuration of transmitting / receiving apparatus 1 according to the seventh embodiment. FIG. 21 is a diagram corresponding to FIG. 1 of the first embodiment, and the same parts as those in FIG. In FIG. 21, unlike FIG. 1, the reception timing signal 7 c is not passed from the reception unit 7 to the correlation processing unit 5. Further, the known sequence 2 d is not passed from the transmission unit 2 to the reception unit 7. Next, the operation of the transmission / reception device 1 will be described. Since the ECM wave 2a is radiated by the transmitting antenna 3 and the reflected wave 7a is received by the receiving unit 7, the operation is the same as that of the transmission / reception apparatus 1 in the first embodiment, and thus the description thereof is omitted. FIG. 22 is a configuration diagram of the receiving unit 7 in the seventh embodiment, and corresponds to FIG. 6 in the first embodiment. Since the reception unit 7 does not detect the header, the reception header detection unit 73 is not provided in FIG. Therefore, the known sequence 2d is not passed from the transmission unit 2. That is, the receiving unit 7 according to the seventh embodiment passes only the digital reception signal 7 b that is the output of the A / D conversion unit 72 to the correlation processing unit 5.

  FIG. 23 is a configuration diagram showing the configuration of the correlation processing unit 5. FIG. 23 is a diagram corresponding to FIG. 8 of the first embodiment, and the same parts as those in FIG. In FIG. 23, unlike FIG. 8, the reception timing signal 7 c is not passed to the memory 52. In the correlation processing unit 5, the digital reference signal 2 b and the transmission timing signal 2 c are passed from the transmission unit 2 as in the first embodiment. On the other hand, a digital reception signal 7b and a reception timing signal 7c are passed from the reception unit 7.

  As in the first embodiment, in the correlation processing unit 5, the codes of the digital reference signal 2b and the digital reception signal 7b are determined by the determination unit 51, and the determined reference sequence 5b and reception sequence 5c are stored in the memory 52, respectively. Entered. When the transmission timing signal 2c is L logic, the memory 52 stores the reference sequence 5b and the reception sequence 5c for the past Ts time. When the transmission timing signal 2c transitions from the L logic to the H logic, the memory 52 starts accumulating the reference sequence 5b and the reception sequence 5c that are newly passed while storing N bits corresponding to the past Ts time. Next, when the transmission timing signal 2c transitions from the L logic to the H logic, the memory 52 passes the accumulated reference sequence 5b and received sequence 5c to the correlation unit 53 as a reference storage sequence 5d and a received storage sequence 5e, respectively. That is, the memory 52 passes the reference sequence 5b and the reception sequence 5c between two successive pulses in the transmission timing signal 2c to the correlation unit 53 as the reference storage sequence 5d and the reception storage sequence 5e. FIG. 24 shows a timing chart of the reference sequence 5b, the transmission timing signal 2c, and the reception sequence 5c. As shown in FIG. 24, each series between two successive pulses in the transmission timing signal 2c corresponds to each series from time T0 to time T2. That is, the reference sequence 5b and the reception sequence 5c between time T0 and time T2 are passed to the correlation unit 53. As in the first embodiment, the correlation unit 53 performs correlation processing, and the correlation signal 5a obtained as a result of the correlation processing is passed to the peak value detection unit 8 to calculate the distance from the transmission / reception device 1 to the target 4 Is done.

  As described above, according to the seventh embodiment, since the header detection in the receiving unit 7 is omitted, the hardware scale of the receiving unit 7 can be reduced and the power consumption can be reduced. Even in the case where the header cannot be detected in the reflected wave 7a due to the influence of noise or other disturbing radio waves, the correlation processing is performed based only on the transmission timing signal 7c. Even if it is received, the effect that the distance to the target 4 can be calculated can be obtained.

It is a block diagram which shows the structure of the transmission / reception apparatus 1 in Embodiment 1 of this invention. It is a block diagram which shows the structural example of the transmission part 2 used for Embodiment 1 of this invention. It is a figure which shows the structural example of the transmission signal 2e used for Embodiment 1 of this invention. It is a block diagram which shows the transmission header detection part 22 and the reception header detection part 73 which are used for Embodiment 1 of this invention. It is a graph which shows the relationship between the correlation value 2i in Embodiment 1 of this invention, and the transmission timing signal 2c. It is a block diagram which shows the structural example of the receiving part 7 used for Embodiment 1 of this invention. It is a graph which shows the relationship between the correlation value 7f and the reception timing signal 7c in Embodiment 1 of this invention. It is a block diagram which shows the structure of the correlation process part 5 used for Embodiment 1 of this invention. It is a timing chart which shows the relationship of the reference sequence 5b, the transmission timing signal 2c, the reception sequence 5c, and the reception timing signal 7c in Embodiment 1 of this invention. It is a figure explaining the correlation calculation of the correlation part 53 used for Embodiment 1 of this invention. It is a graph which shows the time change of the correlation signal 5a in Embodiment 1 of this invention. It is a timing chart which shows the relationship between the reference sequence 5b, the transmission timing signal 2c, the reception sequence 5c, and the reception timing signal 7c in Embodiment 2 of this invention. It is a block diagram which shows the structure of the correlation process part 5 used for Embodiment 3 of this invention. It is a figure explaining the method of the correlation process in Embodiment 3 of this invention. It is a figure explaining the count by the block diagram which shows the structure of the transmission / reception apparatus 1 in Embodiment 4 of this invention, and a counter. It is a block diagram which shows the structure of the transmission / reception apparatus 1 in Embodiment 5 of this invention. It is the block diagram which shows the block diagram which shows the structural example and the receiving header detection part 73 of the receiving part 7 which are used for Embodiment 5 of this invention. It is a block diagram which shows the structural example of the transmission part 2 used for Embodiment 5 of this invention. It is a figure explaining the effect at the time of lengthening the sequence length of the known series 2d in Embodiment 5 of this invention. It is a block diagram which shows the structural example of the transmission part 2 used for Embodiment 6 of this invention. It is a block diagram which shows the structure of the transmission / reception apparatus 1 in Embodiment 7 of this invention. It is a block diagram which shows the structural example of the receiving part 7 used for Embodiment 7 of this invention. It is a block diagram which shows the structure of the correlation process part 5 used for Embodiment 7 of this invention. It is a timing chart which shows the relationship of the reference sequence 5b, the transmission timing signal 2c, and the receiving sequence 5c in Embodiment 7 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission / reception apparatus 2 Transmission part 2a which is a transmission means ECM wave 2b which is a disturbing transmission wave Digital reference signal 2c which is a reference signal Transmission timing signal 3 which is a first timing signal 3 Transmission antenna 4 Target 5 Correlation processing part 5a Correlation value Correlation signal 52 Memory 6 Receiving antenna 7 Receiving antenna 7 Receiving unit 7b Digital received signal 7c converted reception signal Reception timing signal 8 second timing signal 8 Peak value detection detecting means Part 9 Distance calculation part

Claims (8)

A predetermined known sequence is inserted every predetermined time interval , and a part other than the predetermined known sequence generates a disturbing transmission wave from a transmission signal that is a repetition of the same sequence ,
A reference signal including a predetermined transmission header corresponding to the known sequence is generated and output from the generated interference transmission wave, and the transmission header is detected from the generated reference signal and a first timing signal is output. A transmission means;
An antenna for transmitting the disturbing transmission wave to a target and receiving a reflected wave from the target;
Reception that generates and outputs a reception signal including a predetermined reception header corresponding to the known sequence from the received reflected wave, and detects the reception header from the generated reception signal and outputs a second timing signal Means,
Storing the reference signal and the received signal in a storage means;
The reference signal accumulated in a predetermined period from a time that is a predetermined time before the time at which the first timing signal is input to a time at which the second timing signal is input and the predetermined period Correlation processing means for generating a correlation value by performing correlation processing with the accumulated received signal;
Detecting means for detecting a peak of the generated correlation value;
A transmission / reception apparatus that calculates a distance to the target based on a time from when the correlation processing is started until a peak of a correlation value is detected.   The transmission / reception apparatus according to claim 1, wherein the transmission signal includes two or more predetermined known sequences with a predetermined time interval.   The transmission / reception apparatus according to claim 2, wherein the storage unit stores a reference signal and a reception signal having a period longer than the predetermined time interval.   The transmission / reception according to claim 3, wherein the correlation processing in the correlation processing unit is performed by shifting one of the reference signal and the received signal to either the front or rear in time. apparatus. The sequence length of the known sequence or the transmission wavelength of the transmission wave of the portion corresponding to the known sequence included in the jammed transmission wave is variable according to the detection status of the reception header. The transmitting / receiving apparatus according to claim 4. Look containing two or more predetermined known sequence extending over a predetermined time interval, the portion other than the predetermined known sequence generates an interference transmission wave from a transmission signal which is a repetition of the same sequence,
A reference signal including a predetermined transmission header corresponding to the known sequence is generated and output from the generated jammed transmission wave, and the transmission header is detected from the generated reference signal, and two or more first timing signals are generated. Transmitting means for outputting
An antenna for transmitting the disturbing transmission wave to a target and receiving a reflected wave from the target;
Receiving means for generating and outputting a reception signal including a predetermined reception header corresponding to the known series from the received reflected wave;
The reference signal and the received signal are accumulated in the storage means, and the time is past a predetermined time from the time at which the first timing signal that is input first among the two consecutive first timing signals is input. Correlation is performed by performing correlation processing between the reference signal accumulated in a predetermined period from the time until the time when the first timing signal inputted later is inputted and the received signal accumulated in the predetermined period Correlation processing means for generating values;
Detecting means for detecting a peak of the generated correlation value;
A transmission / reception apparatus that calculates a distance to the target based on a time from when the correlation processing is started until a peak of a correlation value is detected. A predetermined known sequence is inserted at every predetermined time interval , and a portion other than the predetermined known sequence generates a jammed transmission wave from a transmission signal that is a repetition of the same sequence, and the jammed transmission wave is transmitted to the target. Sending, and
Outputting a reference signal including a predetermined transmission header corresponding to the known sequence from the generated interference transmission wave, and detecting the transmission header from the reference signal and outputting a first timing signal;
A reflected wave from the target is received, a received signal including a predetermined received header corresponding to the known sequence is output from the reflected wave, and the received header is detected from the received signal to detect a second timing signal A step of outputting
The reference signal and the received signal are accumulated, and accumulated for a predetermined period from a time that is a predetermined time before the time when the first timing signal is input to a time when the second timing signal is input. Performing correlation processing between the received reference signal and the received signal accumulated in the predetermined period and outputting a correlation value;
Detecting a peak of the correlation value;
And a step of calculating a distance to the target based on a time from when the correlation processing is started until a correlation value peak is detected. Look containing two or more predetermined known sequence extending over a predetermined time interval, the portion other than the predetermined known sequence generates an interference transmission wave from a transmission signal which is a repetition of the same sequence, target the interfering transmitter waves Sending to the object,
Outputting a reference signal including a predetermined transmission header corresponding to the known sequence from the generated disturbing transmission wave, detecting the transmission header from the reference signal, and outputting two or more first timing signals; ,
Receiving a reflected wave from the target, and outputting a received signal including a predetermined reception header corresponding to the known sequence from the reflected wave;
Accumulating the reference signal and the received signal, from a time that is a predetermined time earlier than the time when the first timing signal that is input first among the two consecutive first timing signals is input, Correlation processing is performed between the reference signal accumulated during a predetermined period until the time when the first timing signal input later is input and the received signal accumulated during the predetermined period, and a correlation value is output. And steps to
Detecting a peak of the correlation value;
And a step of calculating a distance to the target based on a time from when the correlation processing is started until a correlation value peak is detected.

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