JP2009036540A - Radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar system which can perform secondary echo suppression processings, without causing degradation in the target detection performance. <P>SOLUTION: The radar system is provided with a transmitting/receiving section and a signal processing section. The transmitting/receiving section includes a first phase correction section 7 for performing phase correction on a receiving signal to cancel the phase of a transmitted wave transmitted a fixed time earlier from the transmitting/receiving section; a predominant frequency detecting section 10 for detecting the predominant frequency component of power in the reception signal which has been subjected to the phase correction by the first phase correction section 7; a predominant frequency component removing section 11 for removing the detected frequency component; a re-phase-modulation section 13 for performing phase correction, by using a phase correction amount having reversed polarity, with respect to the phase correction amount by the first phase correction section 7 on the receiving signal which has been subjected to the removal of the predominant frequency component; a second phase correction section 14 for performing phase correction to cancel the initial phase of the transmitted wave transmitted from the transmitting/receiving section; and a primary echo detection section 16 for detecting the primary echo component. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a radar apparatus that measures a distance and speed of a target by radiating a wave in space, receiving a reflected wave scattered by an object (target) existing outside, and performing signal processing.

  As a method for measuring the distance and speed of a target that exists remotely, a technique of pulse Doppler radar has been conventionally known. In this conventional method, pulse modulation is performed on a transmission wave, and a distance is calculated from a time difference between transmission and reception of pulses. Furthermore, the target Doppler frequency can be calculated by performing frequency analysis on the received signal sampled at the pulse repetition period.

  In order to measure the target distance without ambiguity, the pulse repetition period needs to be longer than the time difference between the transmission and reception pulses. On the other hand, in order to measure the speed of a target moving at high speed without ambiguity, it is necessary to sample the received signal at high speed, that is, to shorten the pulse repetition period sufficiently.

  Therefore, in order to resolve both the ambiguity of the distance and the ambiguity of the Doppler frequency, it cannot be performed only by adjusting the pulse repetition period. To solve this problem, for example, there is a method of performing pseudo-random code phase modulation on each pulse, extracting a secondary echo component by phase compensation matched to the secondary echo, and removing this (for example, Non-Patent Document 1). reference).

R.J.Doviak and D.S.Zrnic, Doppler Radar and Weather Observations, Second Ed., P.167-170, Academic Press, Inc., 1993.

However, the prior art has the following problems.
Most of the signals removed in the secondary echo removal processing are secondary echo components, but some components of the diffused primary echo are also removed together. Therefore, the phase of the primary echo is disturbed by such removal processing.

  When the phase of the terrain echo component of the primary echo is disturbed, the terrain echo component, which originally has a Doppler frequency of 0, leaks to another Doppler frequency. Therefore, when the Doppler spectrum is calculated by performing phase compensation in accordance with the primary echo after removing the secondary echo, the situation is similar to the case where the noise level of the Doppler spectrum is increased due to the leakage of the terrain echo.

  Since the terrain echo can have a large received power, the detection performance of the weather echo that needs to be finally detected is reduced even if there is a slight leak. That is, there is a problem that the detection probability of the weather echo decreases, or a problem that the probability of erroneous detection of the terrain echo leaking to a non-zero Doppler frequency increases. In other words, the conventional secondary echo removal processing has a problem in that the target detection performance is lowered because the removal performance of the terrain echo included in the primary echo is lowered.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a radar apparatus capable of performing secondary echo suppression processing without degrading target detection performance.

  A radar apparatus according to the present invention radiates a wave as a transmitted wave in space, receives a reflected wave scattered by an object existing outside as a received wave, detects a received wave, and generates a received signal And a signal processing unit that detects a primary echo component for measuring an object by performing signal processing on the reception signal generated by the transmission / reception unit, the signal processing unit A first phase correction unit that performs phase correction on the reception signal generated by the transmission / reception unit so as to cancel the phase of the transmission wave transmitted from the transmission / reception unit a predetermined time ago, and a first phase correction unit In the received signal after the phase correction, the frequency component detected by the dominant frequency detecting unit from the received signal after the phase correction by the first phase correcting unit and the dominant frequency detecting unit that detects the frequency component where the power is excellent. A phase is obtained by using a phase correction amount obtained by inverting the sign of the phase correction amount by the first phase correction unit with respect to the reception signal after removal of the dominant frequency component by the dominant frequency component removal unit and the dominant frequency component removal unit. A re-phase modulation unit that performs correction, and a second phase correction unit that performs phase correction so as to cancel the initial phase of the transmission wave transmitted from the transmission / reception unit with respect to the reception signal after phase correction by the re-phase modulation unit And a primary echo detector that detects a primary echo component based on the received signal after phase correction by the second phase corrector.

  According to the present invention, the first phase correction and the opposite phase correction are performed on the received signal that has been subjected to the first phase correction so as to cancel the phase of the transmission wave before a certain time, after removing the dominant frequency component. In addition, the second phase correction is performed so as to cancel the initial phase of the transmission wave, and the signal processing is performed so as to obtain the reception signal for measurement, thereby performing the secondary echo suppression process without degrading the target detection performance. A radar device that can be performed can be obtained.

  A preferred embodiment of a radar apparatus according to the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a radar apparatus according to Embodiment 1 of the present invention.
First, each component of the radar apparatus shown in FIG. 1 will be described in order.

  The reference signal generator 1 generates a reference signal that is a source of a transmission wave. The phase modulation unit 2 performs phase modulation on the reference signal obtained by the reference signal generation unit 1. Then, the pulse modulation unit 3 pulsates the transmission signal after the phase modulation. Here, the reference signal generation unit 1, the phase modulation unit 2, and the pulse modulation unit 3 constitute a phase modulation wave generation unit.

  Next, the transmission / reception switching unit 4 outputs the transmission wave input from the pulse modulation unit 3 to the antenna 5 described later and inputs the reception wave from the antenna 5. The antenna 5 radiates a transmission wave to the space and receives a radio wave reflected by an object existing in the space as a reception wave. The reception unit 6 receives the signal received by the antenna 5 via the transmission / reception switching unit 4. A reception signal is generated by inputting a wave and detecting the wave.

  The secondary echo phase correction unit 7 generates a secondary echo area reception signal by performing phase correction on the reception signal in accordance with the secondary echo. Here, the secondary echo phase correction unit 7 constitutes a first phase correction unit.

  The secondary echo removal unit 8 detects the secondary echo component from the secondary echo area reception signal, removes this, and calculates the center Doppler frequency of the detected secondary echo component.

  Next, the rephase modulation unit 13 performs phase modulation again on the secondary echo area reception signal after the secondary echo removal input from the secondary echo removal unit 8. The primary echo phase correction unit 14 obtains a primary echo area reception signal by performing phase correction on the reception signal output from the rephase modulation unit 13 in accordance with the primary echo. Here, the rephase modulation unit 13 and the primary echo phase correction unit 14 constitute a second phase correction unit.

  The terrain echo suppression unit 15 removes low frequency components in a frequency range that can be regarded as terrain echoes from the reception signal output from the primary echo phase correction unit 14. Further, the primary echo detector 16 detects the target signal from the received signal after the terrain echo suppression obtained by the terrain echo suppressor 15.

  The frequency distribution accumulating unit 17 accumulates the secondary echo Doppler frequency output from the secondary echo removing unit 8. The most frequent frequency extraction unit 18 extracts the distance distribution of the Doppler frequency in the selected direction from the Doppler frequencies accumulated in the frequency distribution accumulation unit 17, and extracts the second-order echo spreader frequency that appears at the highest frequency. Further, the code selection unit 19 selects a phase modulation code to be used in the phase modulation unit 2 based on the mode quadratic encode puller frequency extracted by the mode frequency extraction unit 18.

  In the configuration shown in FIG. 1, the reference signal generation unit 1 to the reception unit 6 correspond to the components of the transmission / reception unit, and the secondary echo phase correction unit 7 to the code selection unit 19 are the configuration of the signal processing unit. Corresponds to the element.

Next, the operation will be described in detail.
The reference signal generator 1 generates a reference signal that is a source of a transmission signal. The phase modulation unit 2 receives a reference signal from the reference signal generation unit 1 and performs phase modulation on the reference signal. A pseudo-random code is used for phase modulation, and the code is selected by the code selection unit 19 by a method described later. The pulse modulation unit 3 performs pulse modulation on the phase-modulated signal output from the phase modulation unit 2. Amplification is also performed.

  The transmission signal after pulse modulation and amplification will be referred to herein as a transmission wave. The phase modulation in the phase modulation unit 2 is performed so that the initial phase changes for each pulse output from the pulse modulation unit 3.

  The reference signal generated by the reference signal generator 1 is a signal having a stable frequency over the time when the pulse modulator 3 outputs a plurality of pulses. For this reason, it is possible to perform signal processing in consideration of the phase, that is, coherent signal processing, on a reception signal obtained in a time interval in which a plurality of pulses are transmitted.

  The pulse width of the transmission wave is set according to the distance resolution required for the radar apparatus. For example, when the pulse width is 1 microsecond, a distance resolution of 150 m can be obtained. On the other hand, the time interval at which the transmission pulse is generated is a parameter that determines the ambiguity of the distance. For example, when a transmission pulse having a pulse repetition frequency of 1 kHz is radiated from an antenna, it is possible to measure the distance without compromising the distance section of 150 km.

  When a reflective object exists at a distance exceeding 150 km and the reflected wave is received, the distance is ambiguity. For example, when a reflective object exists at a distance of 200 km, the distance measured from the delay time of the received wave may be 50 km, 200 km, 350 km,. In order to reduce such ambiguity, phase modulation is performed in the phase modulation unit 2.

  The transmission wave output from the pulse modulation unit 3 is radiated into the space via the transmission / reception switching unit 4 and the antenna. When radiated into space, transmission waves are radiated in a state where power is concentrated only in a specific direction (beam direction) according to the directivity characteristics of the antenna. The observation direction can be changed by changing the beam direction in which the transmission wave is emitted with time.

  For example, when an aperture antenna is used for the antenna 5, beam scanning can be performed by mechanically rotating the antenna 5. Alternatively, when a phased array antenna is used for the antenna 5, electronic beam scanning is performed by controlling the phase of the elements constituting the antenna 5. The beam direction of the antenna 5 is output to the mode frequency extraction unit 18.

  The radio wave radiated to the space is reflected by an object existing in the beam direction. A part of the power of such a reflected wave returns in the direction in which the radar exists. The antenna 5 captures the reflected wave that has reached the radar device as a received wave, and this received wave is input to the receiving unit 6 via the transmission / reception switching unit 4. The reception unit 6 generates a reception signal by performing detection processing on the reception wave.

  Here, in the radar apparatus of the present invention, since it is necessary to extract the phase information of the received signal, the receiving unit 6 performs phase detection processing. In the phase detection process, the received wave input from the transmission / reception switching unit 4 is mixed with the one obtained by extracting a part of the reference signal generated by the reference signal generating unit 1, thereby converting the received wave to a low frequency. Received signal is generated.

  At that time, the receiving unit 6 divides the received reference signal into two, one of which is directly mixed with the received wave, and the other is mixed with the received wave after rotating the phase by 90 degrees. By considering one of the two received signals thus generated as a real part and the other as an imaginary part, a received signal represented by a complex number is obtained. The phase of the received signal has a phase change for each pulse as determined by the Doppler frequency of the reflecting object and the phase modulation by the phase modulation unit 2.

The secondary echo phase correction unit 7 corresponds to the first phase correction unit, and assumes the reception of the secondary echo and restores the phase change accompanying the phase modulation performed by the phase modulation unit 2 to the original state. Perform phase correction processing. Now, let s _i be a received signal received after a fixed time after the i-th pulse transmission and before the i + 1-th pulse transmission. Further, it is assumed that the phase modulation amount of the i-th transmission pulse in the phase modulation unit 2 is φ _i .

By performing phase correction on the signal s _i using the phase modulation amount φ _i-1 in the previous pulse transmission, a signal s _{2nd, i} shown in the following equation (1) is obtained.

  This signal is called a secondary echo area reception signal. The secondary echo area reception signal is input to the secondary echo removal unit 8. The secondary echo removal unit 8 detects a secondary echo by Doppler frequency analysis and performs a process of removing the detected secondary echo.

  FIG. 2 is a block diagram showing an internal configuration of the secondary echo removal unit 8 according to Embodiment 1 of the present invention. The secondary echo removal unit 8 includes a Fourier transform unit 9, a peak detection unit 10, a peak removal unit 11, and an inverse Fourier transform unit 12.

  First, the Fourier transform unit 9 performs a Fourier transform on the reception signal after the secondary echo phase correction, that is, the secondary echo area reception signal. When the secondary echo is present, the amplitude is dominant at the Doppler frequency corresponding to the relative velocity of the reflecting object serving as the secondary echo source.

  The peak detection unit 10 corresponds to a dominant frequency detection unit, and detects a portion having such an amplitude, that is, a peak. The detected Doppler frequency is input to the peak removing unit 11 and also input to the frequency distribution accumulating unit 17.

  The peak removal unit 11 corresponds to a dominant frequency component removal unit, and includes a Doppler frequency peak-detected by the peak detection unit 10 with respect to a secondary echo area reception signal after Fourier transform input from the Fourier transform unit 9. The process which removes the signal of a frequency domain is performed. That is, the amplitude in such a frequency region is set to zero.

  Further, the inverse Fourier transform unit 12 performs inverse Fourier transform on the signal after removing the secondary echo, and returns it to the received signal in the time domain.

Here, s ′ _{2nd, i} is a time-domain received signal output from the secondary echo removing unit 8 after removing the secondary echo. The signals s ′ _{2nd and i} are input to the rephase modulation unit 13. Then, the re-phase modulation unit 13 performs processing for returning the phase correction in accordance with the secondary echo performed by the secondary echo phase correction unit 7 as shown in the following equation (2).

That is, the phase added by the phase modulation unit 2 is performed on the signal s ′ _{2nd, i} by performing phase correction processing of an amount obtained by inverting the sign of the phase correction amount corrected by the secondary echo phase correction unit 7. The change is reproduced.

Next, the primary echo phase correction unit 14 corresponds to a second phase correction unit and performs phase correction processing in accordance with the primary echo. That is, the primary echo phase correction unit 14 receives the received signal s ′ _1st after being subjected to phase correction processing that cancels the phase change changed by the phase modulation unit 2 by processing such as the following equation (3). _{, I} is obtained.

  Thereby, for the primary echo, only the phase change caused by the motion of the reflecting object remains in the received signal. This signal is called a primary echo area reception signal.

  The terrain echo suppression unit 15 removes terrain echoes by removing components whose Doppler frequency is near zero. Further, the primary echo detector 16 detects a primary echo component that becomes a target signal from the signal from which the terrain echo is removed.

  The secondary echo Doppler frequency output from the secondary echo removal unit 8 is input to the frequency distribution storage unit 17. The frequency distribution accumulating unit 17 accumulates the Doppler frequency of the secondary echo whenever the observation direction, that is, the antenna beam direction changes. For one observation direction, Doppler frequencies at a plurality of distances are accumulated in the frequency distribution accumulation unit 17.

  The most frequent frequency extraction unit 18 inputs the beam direction of the current antenna from the antenna 5, selects the secondary echo spreader frequency distance distribution in that direction, and extracts the secondary echo puller frequency from the frequency distribution storage unit 17. . Although the secondary echo Doppler frequency varies depending on the distance, the mode frequency extraction unit 18 outputs the most frequent Doppler frequency to the code selection unit 19.

  In the Doppler frequency accumulating process in the frequency distribution accumulating unit 17, the Doppler frequency having elapsed is discarded and updated to a new Doppler frequency. However, in order to improve the Doppler frequency accuracy by the time averaging process, past data of a certain time interval may be accumulated and the Doppler frequency averaged may be output to the mode frequency extraction unit 18.

  When the code selection unit 19 removes the Doppler frequency component equal to the mode frequency by the secondary echo removal unit 8, the code selection unit 19 has the least influence on the terrain echo included in the primary echo, that is, the primary echo component is Doppler. A pseudo-random code that minimizes the amount of spreading to a level other than frequency 0 is selected from a plurality of pseudo-random codes. Further, the code selection unit 19 outputs the selected pseudo-random code to the phase modulation unit 2. The phase modulation unit 2 performs phase modulation in the next observation using the pseudo random code.

  A method for obtaining a plurality of pseudo-random codes having equivalent characteristics is described in, for example, the following document (Nobuya Matsufuji, `` Spread sequence with low periodic correlation used in spread spectrum communication, '' IEICE Technical Report SST91-2, 1991 ).

  The characteristics of the plurality of pseudo-random codes obtained in this way may be evaluated in advance by computer simulation or the like, and the code selection unit 19 may perform code selection using the result.

The characteristic evaluation of a plurality of pseudo-random codes can be performed, for example, by performing a simulation of the following procedure.
Procedure 1) A signal including only frequency 0, that is, a DC signal sequence is prepared. This assumes a terrain echo included in the primary echo.

Procedure 2) Phase modulation is performed on the DC signal sequence using the selected pseudo-random code.
Procedure 3) Phase correction assuming a secondary echo is performed on the signal after phase modulation.
Procedure 4) A secondary echo Fourier transform is obtained by applying a Fourier transform to the signal after phase correction. Actually, the first assumed pseudo signal includes only the primary terrain echo. Therefore, in the secondary echo Fourier transform, the primary terrain echo is spread to all frequencies.

  Procedure 5) In the secondary echo Fourier transform, one frequency point or a plurality of frequency points included in a frequency section having a certain width are selected, and the signal at that frequency point is removed. That is, the amplitude is set to zero. This simulates a situation in which when the secondary echo is detected at the frequency point and the processing for removing it is performed, the diffused primary terrain echo component is also removed at the same time.

Procedure 6) By performing inverse Fourier transform on the secondary echo Fourier transform subjected to the removal processing in procedure 5), the received signal is returned to the time domain signal.
Procedure 7) Re-phase modulation is performed so that the phase correction assuming the secondary echo is returned to the state where the phase modulation is performed, and the phase correction assuming the primary echo is performed.

Procedure 8) The received signal obtained in the procedure 7) is subjected to the terrain echo suppression process, that is, the process of removing the component near the frequency 0.
Procedure 9) Calculate the power of the received signal after the terrain echo suppression obtained in the procedure 8).

Step 10) The processing of step 5) to step 9) is repeated while changing the frequency point or frequency section. If the processing is completed at all frequency points or all frequency intervals, the process proceeds to step 11).
Step 11) The processing of step 2) to step 10) is repeated while changing the pseudo random code to be selected. When the processes for all the pseudo-random codes prepared in advance are completed, the entire process is terminated.

  By the above procedure 1) to procedure 11), the residual power value calculated in procedure 9) is obtained for each frequency point or frequency section for which each pseudo-random code and secondary echo cancellation processing is performed. Save as a table. As a simulation result, a low residual power value means that the erasure echo remains small.

  The code selection unit 19 selects a pseudo-random code having the lowest residual power value from the residual power value table for the frequency input from the mode frequency extraction unit 18 and sets it as a phase modulation code used in the phase modulation unit 2.

  In the received signal output from the primary echo phase correction unit 14, the phase modulation code is set so that the terrain echo component having excellent power has the minimum disturbance due to the removal of the secondary echo. Therefore, the amount of terrain echo components concentrated near the frequency 0 leaks to other frequencies is reduced. As a result, the terrain echo power remaining after the terrain echo suppression processing in the terrain echo suppression unit 15 is reduced, and the detection performance in the primary echo detection unit 16 is not deteriorated.

  As described above, according to the first embodiment, after the dominant frequency component is removed from the received signal that has been subjected to the first phase correction so as to cancel the phase of the transmission wave before a certain time, the first phase Correction and reverse phase correction are performed, and second phase correction is performed so as to cancel the initial phase of the transmission wave, and signal processing is performed so as to obtain a reception signal for measurement. As a result, it is possible to obtain a radar apparatus that can perform secondary echo suppression processing without degrading target detection performance.

  Furthermore, by selecting the phase modulation code used for generating the transmission wave according to the dominant frequency component, a phase modulation code that minimizes the disturbance due to the secondary echo removal can be set. As a result, the terrain echo power remaining after the terrain echo suppression process is reduced, and a decrease in primary echo detection performance can be suppressed.

Embodiment 2. FIG.
In the first embodiment, the case where the phase modulation code is selected in consideration of only the Doppler frequency of the secondary echo has been described. On the other hand, in the second embodiment, a case will be described in which, in addition to this, a phase modulation code is selected in consideration of the distribution of topographic echoes.

  FIG. 3 is a block diagram showing the configuration of the radar apparatus according to Embodiment 2 of the present invention. Compared with the configuration of FIG. 1 in the first embodiment, the configuration of FIG. 3 is a terrain echo intensity calculation unit 21 that calculates the intensity of the terrain echo, and the terrain echo intensity calculated by the terrain echo intensity calculation unit 21. The difference is that an intensity distribution accumulating unit 22 is further provided. The topographic echo intensity calculation unit 21 and the intensity distribution accumulation unit 22 are included in the components of the signal processing unit, and the intensity distribution accumulation unit 22 corresponds to a clutter map unit.

Next, the operation will be described in detail.
The transmission wave modulated in phase by the phase modulation unit 2 is radiated to space, and the received signal obtained by the reception unit 6 is subjected to secondary echo removal processing. Up to the point where the combined phase correction is performed, the operation is the same as that of the first embodiment.

  The terrain echo intensity calculation unit 21 calculates the intensity of the terrain echo from the reception signal output from the primary echo phase correction unit 14. Specifically, if the average power of the output signal is calculated by passing the received signal input to the filter that extracts only the signal component of the frequency band that can be regarded as the terrain echo, the power of the terrain echo is obtained.

  Or if the power of only the component whose frequency is exactly 0 is obtained, the input received signal is averaged as a complex number, and if the square of the amplitude is calculated, it becomes the terrain echo power. The calculated topographic echo intensity is stored in the intensity distribution storage unit 22.

  The process of accumulating the secondary echo frequency in the frequency distribution accumulating unit 17 is the same operation as in the first embodiment. However, unlike the first embodiment, the mode frequency extraction unit 18 uses both the secondary echo frequency of the frequency distribution storage unit 17 and the topographic echo intensity of the intensity distribution storage unit 22 to use the mode frequency. To extract.

  For example, at the observation point where the primary terrain echo is not received or is received, the secondary echo removal unit 8 is not affected by the secondary echo removal. Therefore, the secondary echo frequency superimposed on this observation point need not be used for code selection in the code selection unit 19.

  On the other hand, for observation points with high terrain echo intensity, there is a high possibility that the power remaining after terrain echo disappears in the processing of the terrain echo suppression unit 15 due to the effect of secondary echo removal by the secondary echo removal unit 8. . Therefore, the frequency of the Doppler frequency is calculated by giving a weight to the frequency of the secondary echo appearing at a distance where the terrain echo power is high among the Doppler frequencies stored in the frequency distribution storage unit 17.

  Thereby, the code selection unit 19 can perform the code selection by giving priority to the distance at which the disappearance of the terrain echo suppression process may become large because the terrain echo power is high.

  As described above, according to the second embodiment, the phase modulation code used for generating the transmission wave is selected in consideration of the terrain echo power together with the dominant frequency component. As a result, in addition to the effect of the first embodiment, the code selection can be performed by giving priority to the distance where the disappearance of the terrain echo suppression process may become large, and the primary echo detection performance deteriorates. Can be further suppressed.

Embodiment 3 FIG.
In the first and second embodiments, the case where the pseudo-random code used for the phase modulation is changed according to the frequency of the secondary echo has been described. On the other hand, in this Embodiment 3, the case where the presence or absence of a secondary echo removal process is changed according to the frequency of a secondary echo is demonstrated instead of fixing the pseudorandom code used for phase modulation.

  FIG. 4 is a block diagram showing the configuration of the radar apparatus according to Embodiment 3 of the present invention. Among the components in FIG. 4, primary echo phase correction units 14a and 14b, Fourier transform unit 31a to background level calculation unit 34a, Fourier transform unit 31b to background level calculation unit 34b, background level comparison unit 35 to code recording unit. 38 is included in the components of the signal processing unit.

  The reception signal is input by the receiving unit 6, and the secondary echo phase correction unit 7, the secondary echo removal unit 8, the rephase modulation unit 13, and the primary echo phase correction unit 14 a process to remove the secondary echo and the primary echo. The portion for performing phase correction assuming the above is the same operation as in the first embodiment. Here, the secondary echo phase correction unit 7 corresponds to a first phase correction unit, and the primary echo phase correction unit 14a corresponds to a second phase correction unit.

  However, in the configuration of FIG. 4, the pseudo-random code used in the phase modulation unit 2 or the like is one that is fixedly recorded in the code recording unit 38, and the code is not changed during observation. This is different from the first and second embodiments.

  The received signal subjected to phase correction assuming a primary echo is input to the Fourier transform unit 31a and subjected to Fourier transform. Then, the terrain echo removing unit 32a performs a process of removing terrain echoes near the frequency 0 on the signal after the Fourier transform. The removal process may be a process of setting the amplitude to 0, or a process of interpolating the removal section using the amplitude of the frequency component outside the removal section.

  The spectrum peak detection unit 33a detects a frequency component having an excellent amplitude for a signal from which the terrain echo is removed after the Fourier transform. The background level calculation unit 34a extracts only the components in the frequency domain that can be regarded as background noise by removing the signal around the peak detected by the spectrum peak detection unit 33a from the signal from which the terrain echo has been removed after the Fourier transform. To do. Furthermore, the background level calculation unit 34a calculates the average power of the extracted components and outputs this as the background level.

  On the other hand, in the configuration of FIG. 4 according to the third embodiment, the primary echo phase correction unit 14b, the Fourier transform unit 31b, the terrain echo removal unit 32b, the spectrum peak detection unit 33b, and the background level calculation unit 34b perform primary echo. The background level is calculated in the same manner as the circuit on the a side of the phase correction unit 14a to the background level calculation unit 34a.

  However, the input signal of the primary echo phase correction unit 14 b is not the output signal of the rephase modulation unit 13 but directly input from the reception unit 6. That is, the circuit on the b side of the primary echo phase correction unit 14b to the background level calculation unit 34b calculates the background level using the received signal that has not been subjected to the secondary echo removal process. The primary echo phase correction unit 14b corresponds to a third phase correction unit.

  The background level comparison unit 35 compares the background level calculated by the background level calculation unit 34a with the background level calculated by the background level calculation unit 34b. When the disappearance of the primary terrain echo increases due to the secondary echo removal, the background level calculated by the background level calculation unit 34b that does not perform the secondary echo removal is calculated by the background level calculation unit 34a. Lower than the background level. In this case, the background level comparison unit 35 generates a control signal so that the signal output from the topographic echo removal unit 32b is input to the primary echo detection unit 37, and switches the switching unit 36.

  On the other hand, when the influence of the secondary echo removal on the primary terrain echo is small, the background level calculated by the background level calculation unit 34a is reduced by the effect of the background level reduction by the secondary echo removal. It becomes lower than the background level calculated in 34b. In this case, the background level comparison unit 35 generates a control signal so that the signal output from the terrain echo removal unit 32a is input to the primary echo detection unit 37, and switches the switching unit 36.

  In the configuration of FIG. 4, the target detection by the spectral peak detection units 33a and 33b and the primary echo detection unit 37 for calculating the background level is performed separately. The target detection process may be combined with the process of the spectrum peak detection units 33a and 33b.

  As described above, according to the third embodiment, the presence or absence of the secondary echo removal process is controlled according to the characteristics of the secondary echo. As a result, it is possible to obtain an effect that the target detection performance is not deteriorated due to the side effect of the secondary echo removal processing.

Embodiment 4 FIG.
In the third embodiment described above, the case where both the case where the secondary echo removal process is performed and the case where the secondary echo removal process is not performed is performed and the better characteristic is selected has been described. On the other hand, in the fourth embodiment, a case will be described in which processing is performed with the presence or absence of secondary echo removal processing determined in advance.

  FIG. 5 is a block diagram showing the configuration of the radar apparatus according to Embodiment 4 of the present invention. Among the components in FIG. 5, the switching unit 41 to the terrain echo intensity calculation unit 44 are all included in the components of the signal processing unit.

  The reception signal output from the reception unit 6 is output to the switching unit 41. The switching unit 41 outputs an input signal to either the secondary echo phase correction unit 7 or the switching unit 43 in accordance with an instruction from the secondary echo removal ON / OFF setting unit 42. Here, the secondary echo phase correction unit 7 corresponds to a first phase correction unit.

  When the secondary echo removal ON / OFF setting unit 42 is set to ON, the switching unit 41 outputs a reception signal to the secondary echo phase correction unit 7. Processing such as secondary echo removal processing by the secondary echo phase correction unit 7, secondary echo removal unit 8, and rephase modulation unit 13 with respect to the input received signal is the same operation as in the previous embodiment.

  Similarly to the switching unit 41, the switching unit 43 is also controlled by the secondary echo cancellation ON / OFF setting unit 42. In the case of ON setting, the received signal output from the rephase modulation unit 13 is It operates to input to the primary echo phase correction unit 14. The primary echo phase correction unit 14 in this case corresponds to a second phase correction unit.

  On the other hand, when the secondary echo cancellation ON / OFF setting unit 42 is set to OFF, the received signal input from the receiving unit 6 is directly transmitted to the primary echo phase via the switching unit 41 and the switching unit 43. Input to the correction unit 14. The primary echo phase correction unit 14 performs phase correction assuming a primary echo. The primary echo phase correction unit 14 in this case corresponds to a third phase correction unit.

  The terrain echo intensity calculation unit 44 calculates terrain echo power from the reception signal output from the primary echo phase correction unit 14. The terrain echo intensity calculation unit 44 determines that the terrain echo disappearance may occur due to the side effect of the secondary echo removal process when the calculated terrain echo power is higher than a preset value. The setting of the secondary echo removal ON / OFF setting unit 42 is turned off, and the secondary echo removal processing at the observation point is turned off.

  Conversely, if the calculated terrain echo power is lower than or equal to a preset value, the terrain echo intensity calculation unit 44 determines that no remaining terrain echo disappears due to the side effect of the secondary echo removal process, The setting of the secondary echo removal ON / OFF setting unit 42 is turned on, and the secondary echo removal processing at the observation point is turned on. The setting of the secondary echo removal ON / OFF setting unit 42 is used to control signal processing when the same beam direction is observed next time. If the calculated terrain echo power is equal to a preset value, the terrain echo intensity calculation unit 44 may perform the same processing as when the calculated terrain echo power is higher than a preset value.

  As described above, according to the fourth embodiment, ON / OFF of the secondary echo removal is performed for each beam direction or each distance. Therefore, an appropriate processing method is selected for each observation point. That is, since ON / OFF of the secondary echo cancellation is selected, the performance of unnecessary wave suppression is improved, and as a result, the target detection performance can be improved.

  Furthermore, the configuration of the fourth embodiment is a configuration that performs only one of the processes with or without the secondary echo removal process according to the value of the terrain echo intensity. There is an advantage that the amount of calculation of signal processing is smaller than the configuration.

  In the configuration of FIG. 5, the signal processing method is controlled using the terrain echo intensity calculated from the received signal. However, when it can be considered that the temporal change in the distribution of the terrain echo is small, it is also possible to store the terrain echo intensity in advance as a map and control ON / OFF of the secondary echo removal using this map. In this case, the terrain echo intensity calculation process can be omitted, so that the signal processing can be simplified.

Embodiment 5 FIG.
In the first to fourth embodiments, the case where the phase of the transmission wave is controlled by the phase modulation unit 2 has been described. However, when an oscillation tube such as a magnetron is used to generate a transmission wave, the initial phase changes randomly for each transmission pulse, so phase control using the phase modulator 2 cannot be performed. Therefore, in the fifth embodiment, a case where an oscillation tube such as a magnetron is used to generate a transmission wave will be described.

  In such a case, the same effect as the phase control by the phase modulator 2 can be obtained due to the characteristic that the initial phase changes randomly.

  FIG. 6 is a block diagram showing a configuration of a radar apparatus according to Embodiment 5 of the present invention. In the configuration of FIG. 6, the reference signal generation unit 1, the transmission / reception switching unit 4, the antenna 5, the reception unit 6, the oscillation unit 51, the switching unit 52, and the coupler 53 correspond to a transmission / reception unit. On the other hand, other configuration requirements that are not included in the transmission / reception unit, including the switching unit 54 and the initial phase calculation unit 55, correspond to the signal processing unit.

  The oscillating unit 51 can generate a high-power transmission pulse as a transmission wave by using a magnetron. The transmission wave is input to the antenna 5 via the transmission / reception switching unit 4. The antenna 5 radiates the transmission wave to the space and captures the reception wave. The received wave is input to the switching unit 52 via the transmission / reception switching unit 4.

  A part of the transmission wave generated by the oscillating unit 51 is extracted by the coupler 53. The switching unit 52 outputs the transmission wave input from the coupler 53 to the receiving unit 6 during pulse transmission. The transmission wave is mixed with the reference signal input from the reference signal generation unit 1 and output from the reception unit 6 as a transmission signal. The switching unit 54 outputs the transmission signal to the initial phase calculation unit 55. The initial phase calculator 55 calculates and holds the phase value of the transmission signal obtained as a complex signal.

  On the other hand, when transmission of the transmission pulse is finished, the switching unit 52 inputs the received wave from the transmission / reception switching unit 4 and outputs the received wave to the receiving unit 6. The receiving unit 6 generates a received signal by mixing the received wave with a reference signal. The generated reception signal is output to the switching unit 41 via the switching unit 54.

  The received signal processing method is almost the same as in the fourth embodiment. That is, when the secondary echo removal ON / OFF setting unit 42 sets the secondary echo removal to ON, the switching unit 41, the secondary echo phase correction unit 7, the secondary echo removal unit 8, and the rephase modulation unit 13. The processed reception signal is input to the primary echo phase correction unit 14 via the switching unit 43. The primary echo phase correction unit 14 in this case corresponds to a second phase correction unit. The secondary echo phase correction unit 7 corresponds to a first phase correction unit.

  Conversely, when the secondary echo cancellation is set to OFF by the secondary echo cancellation ON / OFF setting unit 42, the received signal is sent to the primary echo phase correction unit 14 via the switching unit 41 and the switching unit 43. Entered. The primary echo phase correction unit 14 in this case corresponds to a third phase correction unit.

  Thereafter, in the same manner as in the fourth embodiment, secondary echo removal ON / OFF is performed by the processing of the primary echo phase correction unit 14, the terrain echo intensity calculation unit 44, and the secondary echo removal ON / OFF setting unit 42. Set OFF.

However, the phase correction amount in the secondary echo phase correction unit 7 is the initial phase amount φ _i−1 of the previous transmission pulse calculated by the initial phase calculation unit 55, and the rephase modulation unit 13 The phase correction amount at is −φ _i−1 . The phase correction amount in the primary echo phase correction unit 14 is the initial phase amount φ _i of the latest transmission pulse calculated by the initial phase calculation unit 55.

  As described above, according to the fifth embodiment, the same effect as in the first to fourth embodiments can be obtained even in a radar apparatus using an inexpensive magnetron as a transmission tube.

  The configuration of FIG. 6 is obtained by replacing the radar apparatus having the configuration of FIG. 5 described in the fourth embodiment with a radar configuration using a magnetron, but the diagram described in the third embodiment. The radar apparatus having the configuration 4 can be changed to a radar configuration using a magnetron. That is, the portion constituted by the reference signal generating unit 1, the phase modulating unit 2, the pulse modulating unit 3, the transmission / reception switching unit 4 and the code recording unit 38 of FIG. If the unit 4, the coupler 53, the switching unit 52, the reference signal generating unit 1, the switching unit 54, and the initial phase calculating unit 55 are replaced, the radar using the magnetron is the same as in the third embodiment. The effect of can be obtained.

It is a block diagram showing the structure of the radar apparatus in Embodiment 1 of this invention. It is a block diagram which shows the internal structure of the secondary echo removal part in Embodiment 1 of this invention. It is a block diagram showing the structure of the radar apparatus in Embodiment 2 of this invention. It is a block diagram showing the structure of the radar apparatus in Embodiment 3 of this invention. It is a block diagram showing the structure of the radar apparatus in Embodiment 4 of this invention. It is a block diagram showing the structure of the radar apparatus in Embodiment 5 of this invention.

Explanation of symbols

  1 reference signal generation unit, 2 phase modulation unit, 3 pulse modulation unit, 4 transmission / reception switching unit, 5 antenna, 6 reception unit, 7 secondary echo phase correction unit, 8 secondary echo removal unit, 9 Fourier transform unit, 10 peak Detection unit, 11 Peak removal unit, 12 Inverse Fourier transform unit, 13 Rephase modulation unit, 14, 14a, 14b Primary echo phase correction unit, 15 Terrain echo suppression unit, 16 Primary echo detection unit, 17 Frequency distribution storage unit , 18 Mode frequency extraction unit, 19 Code selection unit, 21 Terrain echo intensity calculation unit, 22 Intensity distribution accumulation unit, 31, 31a, 31b Fourier transform unit, 32, 32a, 32b Terrain echo removal unit, 33a, 33b Spectrum peak Detection unit, 34a, 34b background level calculation unit, 35 background level comparison unit, 36 switching unit, 37 primary echo detection unit, 38 code recording unit, 41 switching unit, 42 secondary echo removal ON / OFF setting unit, 43 switching unit, 44 terrain echo intensity calculation unit, 51 oscillation unit, 52 switching unit, 53 coupler, 54 switching unit, 55 initial phase calculation unit.

Claims (14)

A transmitting / receiving unit that radiates a wave as a transmission wave in space, receives a reflected wave scattered by an object existing outside as a reception wave, detects the reception wave, and generates a reception signal;
A radar apparatus comprising: a signal processing unit that detects a primary echo component for measuring the object by performing signal processing on the reception signal generated by the transmission / reception unit;
The signal processing unit
A first phase correction unit that performs phase correction on the received signal generated by the transmission / reception unit so as to cancel an initial phase of a transmission wave transmitted from the transmission / reception unit a predetermined time before;
In the received signal after the phase correction by the first phase correction unit, a dominant frequency detection unit that detects a frequency component in which power is dominant;
A dominant frequency component removing unit that removes the frequency component detected by the dominant frequency detecting unit from the received signal after phase correction by the first phase correcting unit;
Re-phase modulation unit that performs phase correction on the received signal after removal of the dominant frequency component by the dominant frequency component removal unit using a phase correction amount obtained by inverting the sign of the phase correction amount by the first phase correction unit When,
A second phase correction unit that performs phase correction to cancel the initial phase of the transmission wave transmitted from the transmission / reception unit with respect to the reception signal after the phase correction by the rephase modulation unit;
A radar apparatus comprising: a primary echo detection unit that detects a primary echo component based on a received signal after phase correction by the second phase correction unit. The radar apparatus according to claim 1, wherein
The transceiver unit is
A phase-modulated wave generator that generates a wave whose initial phase changes every certain time; and
An antenna that radiates the wave generated by the phase-modulated wave generation unit to space as a transmission wave and inputs a wave arriving from space as a reception wave;
A reception unit that generates a reception signal by detecting a reception wave input in the antenna unit;
Including
The signal processing unit
A first phase correction unit that performs phase correction on the reception signal generated by the reception unit so as to cancel a phase change that has been changed by the phase modulation wave generation unit a predetermined time ago;
In the received signal after the phase correction by the first phase correction unit, a dominant frequency detection unit that detects a frequency component in which power is dominant;
A code selection unit that selects a phase modulation code according to the frequency component detected by the dominant frequency detection unit, and controls an initial phase that is changed by the phase modulation wave generation unit according to the selected phase modulation code;
A dominant frequency component removing unit that removes the frequency component detected by the dominant frequency detecting unit from the received signal after phase correction by the first phase correcting unit;
Re-phase modulation unit that performs phase correction on the received signal after removal of the dominant frequency component by the dominant frequency component removal unit using a phase correction amount obtained by inverting the sign of the phase correction amount by the first phase correction unit When,
A second phase correction unit that performs phase correction on the received signal after the phase correction by the re-phase modulation unit so as to cancel the phase change changed by the phase modulation wave generation unit;
A radar apparatus, comprising: a primary echo detection unit that detects a primary echo component based on a reception signal after the phase correction by the second phase correction unit. The radar apparatus according to claim 2, wherein
The phase-modulated wave generating unit generates a wave that is pulse-modulated so that the initial phase changes every predetermined time and has a predetermined amplitude or more only in a specific time section within a fixed time,
The receiving unit generates a reception signal for each delay time based on the transmission wave radiation time,
The radar device, wherein the dominant frequency detection unit detects a dominant frequency for each delay time. The radar apparatus according to claim 3, wherein
The radar apparatus according to claim 1, wherein the code selection unit selects a phase modulation code based on a frequency detected with the highest frequency among the dominant frequencies detected by the dominant frequency detection unit. The radar apparatus according to claim 4, wherein
The code selection unit weights the dominant frequency obtained in the delay time superimposed on the terrain clutter received as the primary echo, and calculates the frequency of the dominant frequency detected by the dominant frequency detection unit. A radar device characterized by the above. The radar apparatus according to claim 5, wherein
The code selection unit has a clutter map unit that holds in advance a delay time to be superimposed on the terrain clutter received as the primary echo, and inputs a delay time that is expected to receive the terrain clutter from the clutter map unit And a frequency weighting based on the input delay time. The radar apparatus according to claim 6, wherein
The signal processing unit further includes a terrain echo intensity calculation unit that calculates the terrain echo intensity from the received signal after phase correction by the second phase correction unit and stores the terrain echo intensity distribution in the clutter map unit,
The radar apparatus according to claim 1, wherein the code selection unit performs frequency weighting based on the delay time and the topographic echo intensity distribution. The radar apparatus according to claim 5, wherein
The code selection unit assigns a large weight to the dominant frequency obtained in the delay time superimposed on the terrain clutter received as the primary echo, and increases the weight of the terrain clutter received in the delay time as the strength increases. Radar apparatus that increases the frequency of the dominant frequency detected by the dominant frequency detector. The radar apparatus according to claim 2, wherein
The antenna unit has a function of changing a directivity direction when radiating a transmission wave to the atmosphere, or a directivity direction when inputting a reception wave,
The radar apparatus according to claim 1, wherein the code selection unit selects a phase modulation code for each directivity direction changed by the antenna unit. The radar apparatus according to claim 2, wherein
The code selection unit has the smallest amount of spreading of the primary terrain echo component included in the received signal after the removal of the dominant frequency component by the dominant frequency component removing unit to a frequency band other than the true terrain echo spectrum frequency. Such a pseudo-random code is selected from a plurality of pseudo-random codes. The radar apparatus according to claim 1, wherein
The transceiver unit is
A phase-modulated wave generator that generates a wave whose initial phase changes every certain time; and
An antenna that radiates the wave generated by the phase-modulated wave generation unit to space as a transmission wave and inputs a wave arriving from space as a reception wave;
A reception unit that generates a reception signal by detecting a reception wave input in the antenna unit;
Including
The signal processing unit
A first phase correction unit that performs phase correction on the reception signal generated by the reception unit so as to cancel a phase change that has been changed by the phase modulation wave generation unit a predetermined time ago, and the first phase In the received signal after the phase correction by the correction unit, a dominant frequency detection unit that detects a frequency component in which power is dominant;
A dominant frequency component removing unit that removes the frequency component detected by the dominant frequency detecting unit;
Re-phase modulation unit that performs phase correction on the received signal after removal of the dominant frequency component by the dominant frequency component removal unit using a phase correction amount obtained by inverting the sign of the phase correction amount by the first phase correction unit When,
A second phase correction unit that performs phase correction on the received signal after the phase correction by the re-phase modulation unit so as to cancel the phase change changed by the phase modulation wave generation unit;
A first background power calculating unit that calculates a first background received power obtained by removing a dominant frequency component from the received signal after the phase correction by the second phase correcting unit;
A third phase correction unit that performs phase correction on the reception signal generated by the reception unit so as to cancel the phase change changed by the phase modulation wave generation unit;
A second background power calculation unit that calculates a second background received power obtained by removing a dominant frequency component for the received signal after the phase correction by the third phase correction unit;
The first background received power calculated by the first background power calculating unit is compared with the second background received power calculated by the second background power calculating unit, and the first background is calculated. When the received power is smaller than the second background received power, the received signal obtained by the second phase correction unit is output, and the second background received power is greater than the first background received power. Is smaller, a switching unit that outputs the reception signal obtained by the third phase correction unit, and a primary echo detection unit that detects a primary echo component based on the reception signal output by the switching unit A radar apparatus comprising: and. The radar apparatus according to claim 1, wherein
The transceiver unit is
A phase-modulated wave generator that generates a wave whose initial phase changes every certain time; and
An antenna that radiates the wave generated by the phase-modulated wave generator as a transmission wave to space, and inputs a wave arriving from space as a reception wave;
A reception unit that generates a reception signal by detecting a reception wave input in the antenna unit;
Including
The signal processing unit
A first phase correction unit that performs phase correction on the reception signal generated by the reception unit so as to cancel a phase change that has been changed by the phase modulation wave generation unit a predetermined time ago;
In the received signal after the phase correction by the first phase correction unit, a dominant frequency detection unit that detects a frequency component in which power is dominant;
A dominant frequency component removing unit that removes the frequency component detected by the dominant frequency detecting unit;
Re-phase modulation unit that performs phase correction on the received signal after removal of the dominant frequency component by the dominant frequency component removal unit using a phase correction amount obtained by inverting the sign of the phase correction amount by the first phase correction unit When,
A second phase correction unit that performs phase correction on the received signal after the phase correction by the re-phase modulation unit so as to cancel the phase change changed by the phase modulation wave generation unit;
A third phase correction unit that performs phase correction on the reception signal generated by the reception unit so as to cancel the phase change changed by the phase modulation wave generation unit;
The received signal after phase correction by the second phase correcting unit and the received signal after phase correction by the third phase correcting unit are input, and either received signal is output according to an external control signal A switching unit to
The terrain echo power is calculated from the reception signal output from the switching unit, and when the calculated terrain echo power is smaller than a predetermined threshold, the reception signal after the phase correction by the second phase correction unit is selected. Generating a control signal, and when the calculated topographic echo power is greater than the predetermined threshold, generate a control signal for selecting a reception signal after phase correction by the third phase correction unit, and A switching control unit to control;
A radar apparatus comprising: a primary echo detection unit that detects a primary echo component based on the reception signal output by the switching unit. The radar apparatus according to claim 1, wherein
The transceiver unit is
A transmission wave generator for generating a wave, and
An antenna that radiates the wave generated by the transmission wave generator to the space as a transmission wave, and inputs the wave that has arrived from the space as a reception wave;
A reception unit that generates a reception signal by detecting a reception wave input in the antenna unit;
Including
The signal processing unit
A transmission wave initial phase extraction unit that takes a part of the transmission wave and measures an initial phase;
Based on the initial phase measured by the transmission wave initial phase extraction unit with respect to the transmission wave transmitted a predetermined time ago, the initial phase is canceled with respect to the reception signal generated by the reception unit. A first phase correction unit for performing phase correction;
In the received signal after the phase correction by the first phase correction unit, a dominant frequency detection unit that detects a frequency component in which power is dominant;
A dominant frequency component removing unit that removes the frequency component detected by the dominant frequency detecting unit;
Re-phase modulation unit that performs phase correction on the received signal after removal of the dominant frequency component by the dominant frequency component removal unit using a phase correction amount obtained by inverting the sign of the phase correction amount by the first phase correction unit When,
Based on the initial phase measured by the transmitted wave initial phase extraction unit for the transmitted wave, phase correction is performed so as to cancel the initial phase with respect to the received signal after phase correction by the rephase modulation unit. A second phase correction unit for applying
A first background power calculating unit that calculates a first background received power obtained by removing a dominant frequency component from the received signal after the phase correction by the second phase correcting unit;
First, phase correction is performed on the transmitted signal based on the initial phase measured by the transmission wave initial phase extraction unit so as to cancel the initial phase with respect to the reception signal generated by the reception unit. Three phase correction units;
A second background power calculation unit that calculates a second background received power obtained by removing a dominant frequency component for the received signal after the phase correction by the third phase correction unit;
The first background received power calculated by the first background power calculating unit is compared with the second background received power calculated by the second background power calculating unit, and the first background is calculated. When the received power is smaller than the second background received power, the received signal obtained by the second phase correction unit is output, and the second background received power is greater than the first background received power. Is smaller, a switching unit that outputs the reception signal obtained by the third phase correction unit, and a primary echo detection unit that detects a primary echo component based on the reception signal output by the switching unit A radar apparatus comprising: and. The radar apparatus according to claim 1, wherein
The transceiver unit is
A transmission wave generator for generating a wave, and
An antenna that radiates the wave generated by the transmission wave generator to the space as a transmission wave, and inputs the wave that has arrived from the space as a reception wave;
A reception unit that generates a reception signal by detecting a reception wave input in the antenna unit;
Including
The signal processing unit
A transmission wave initial phase extraction unit that takes a part of the transmission wave and measures an initial phase;
Based on the initial phase measured by the transmission wave initial phase extraction unit with respect to the transmission wave transmitted a predetermined time ago, the initial phase is canceled with respect to the reception signal generated by the reception unit. A first phase correction unit for performing phase correction;
In the received signal after the phase correction by the first phase correction unit, a dominant frequency detection unit that detects a frequency component in which power is dominant;
A dominant frequency component removing unit that removes the frequency component detected by the dominant frequency detecting unit;
Re-phase modulation unit that performs phase correction on the received signal after removal of the dominant frequency component by the dominant frequency component removal unit using a phase correction amount obtained by inverting the sign of the phase correction amount by the first phase correction unit When,
Based on the initial phase measured by the transmitted wave initial phase extraction unit for the transmitted wave, phase correction is performed so as to cancel the initial phase with respect to the received signal after phase correction by the rephase modulation unit. A second phase correction unit for applying
First, phase correction is performed on the transmitted signal based on the initial phase measured by the transmission wave initial phase extraction unit so as to cancel the initial phase with respect to the reception signal generated by the reception unit. Three phase correction units;
The received signal after phase correction by the second phase correcting unit and the received signal after phase correction by the third phase correcting unit are input, and either received signal is output in accordance with an external control signal A switching unit to
The terrain echo power is calculated from the reception signal output from the switching unit, and when the calculated terrain echo power is smaller than a predetermined threshold, the reception signal after the phase correction by the second phase correction unit is selected. Generating a control signal, and when the calculated topographic echo power is greater than the predetermined threshold, generate a control signal for selecting the received signal after phase correction by the third phase correction unit, and A switching control unit to control;
A radar apparatus comprising: a primary echo detection unit that detects a primary echo component based on a reception signal output by the switching unit.

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