JP5574907B2 - Radar equipment - Google Patents

Description

  The present invention relates to a radar apparatus for measuring a distance and speed of a target existing remotely.

  Conventionally, a pulse Doppler radar technique is known as a method for measuring the distance and speed of a target existing remotely. In this measurement method, a transmission wave is subjected to pulse modulation, and a distance is calculated from a time difference between transmission and reception of pulses. Further, the target Doppler frequency is calculated by performing frequency analysis on the received signal sampled at the pulse repetition period.

At this time, in order to measure the target distance without ambiguity, it is necessary to set the pulse repetition period 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 (to sufficiently shorten the pulse repetition period).

Therefore, it is not possible to simultaneously realize the disambiguation of the distance and the disambiguation of the Doppler frequency only by adjusting the pulse repetition period.
Therefore, a method has been proposed in which each pulse is subjected to pseudo-random code phase modulation, a secondary echo component is extracted by phase compensation in accordance with the secondary echo, and the secondary echo component is removed (for example, Non-Patent Document 1). reference).

However, the secondary echo removal processing by the above method has the following problems.
In the secondary echo removal process, most of the signal to be removed is a secondary echo component, but a part of the diffused primary echo is also removed.

  Thus, when a part of the primary echo is removed, the phase of the primary echo is disturbed, and when the phase of the topographic echo component of the primary echo is disturbed, the Doppler frequency is originally Terrain echo components that are zero leak to other Doppler frequencies.

  As a result, when the Doppler spectrum is calculated by performing phase compensation in accordance with the primary echo after removing the secondary echo and the noise level of the Doppler spectrum increases due to the leakage of the terrain echo, the situation becomes the same.

  Since the terrain echo can have a large received power, even if it is a little leak, the detection performance of the weather echo that needs to be finally detected deteriorates. That is, there is a problem that the detection probability of meteorological echo is reduced or the probability of erroneous detection of terrain echo leaking to other Doppler frequencies is increased.

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

  The conventional radar apparatus has a problem that the target detection performance is deteriorated because the removal performance of the terrain echo included in the primary echo is deteriorated in the secondary echo removal processing.

  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 realizing secondary echo suppression processing without degrading target detection performance.

  A radar apparatus according to the present invention radiates a pulse wave in space, receives a reflected wave scattered by an object existing in the space, and performs signal processing on the received signal to measure the object A phase-modulated wave generator that generates a pulse wave whose initial phase changes with each transmission, and an antenna that radiates the pulse wave to the space as a transmission wave and acquires a reflected wave arriving from the space as a reception wave; , A receiving unit that generates a received signal by detecting the received wave, and a phase correction that cancels the initial phase of the pulse wave transmitted two or more times before the received signal generated from the receiving unit A first Doppler frequency component having excellent power from a first secondary echo phase correction unit that performs phase correction and a received signal phase-corrected by the first secondary echo phase correction unit A first multi-order echo removal unit that estimates and removes the power of the first Doppler frequency component; a multi-order echo power estimation unit that calculates the power removed by the first multi-order echo removal unit; A first primary echo phase correction unit that performs phase correction on the received signal output from the first multi-order echo removal unit so as to cancel the initial phase of the pulse wave transmitted immediately before; A first primary unnecessary wave component removing unit that removes a second Doppler frequency component in which an unnecessary wave is assumed to be present from the reception signal phase-corrected by the secondary echo phase correcting unit, and a reception generated from the receiving unit. A second primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the signal, and a reception signal that has been phase corrected by the second primary echo phase correction unit From the third, the existence of unnecessary waves is assumed. A second primary unnecessary wave component removing unit that removes the power of the Doppler frequency component; a primary unnecessary wave power estimating unit that calculates the power removed by the second primary unnecessary wave component removing unit; Second multi-order echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted two or more times before the reception signal from which unnecessary waves have been removed by the next unnecessary wave component removal unit And a second multi-order echo that estimates the fourth Doppler frequency component having excellent power from the received signal phase-corrected by the second multi-order echo phase correction unit and removes the fourth Doppler frequency component. And a third primary echo phase correction unit that performs phase correction on the received signal output from the second multi-order echo removal unit so as to cancel the initial phase of the pulse wave transmitted immediately before, 1 estimated by the primary unwanted wave power estimation unit Based on the secondary unnecessary wave power and the multi-order echo power estimated by the multi-order echo power estimation unit, the received signal whose phase is corrected by the third primary echo phase correction unit or the first primary unnecessary wave component removal unit And a reception signal switching unit that selects and outputs any one of the reception signals from which unnecessary waves have been removed.

  According to the present invention, it is possible to realize secondary echo suppression processing without degrading target detection performance.

It is a block diagram which shows the structure of the radar apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the internal structure of the secondary echo removal part in FIG. It is a block diagram which shows the internal structure of the topographic echo removal part in FIG. It is a block diagram which shows the structure of the radar apparatus which concerns on Embodiment 1 of this invention.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention.
In FIG. 1, a radar apparatus according to Embodiment 1 of the present invention radiates a pulse wave in space, receives a reflected wave scattered by an object existing in the space, and performs signal processing on the received signal. Thus, in order to measure an object, a reference signal generation unit 1, a phase modulation unit 2, a pulse modulation unit 3, a transmission / reception switching unit 4, an antenna 5, and a reception unit 6 are provided.

The reference signal generation unit 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, and the pulse modulation unit 3 performs phase modulation. The later transmission signal is pulsed.
The transmission / reception switching unit 4 outputs the transmission wave pulsed by the pulse modulation unit 3 to the antenna and takes in the reception wave from the antenna.

The reference signal generation unit 1, the phase modulation unit 2, and the pulse modulation unit 3 constitute a phase modulation wave generation unit that generates a pulse wave whose initial phase changes every transmission.
The antenna 5 radiates a pulse wave as a transmission wave to the space, and acquires a radio wave (reflected wave) that has been reflected by an object existing in the space as a reception wave.
The reception unit 6 receives a reception wave that is received by the antenna 5 and passes through the transmission / reception switching unit 4, and generates a reception signal by detecting the reception wave.

  In addition, the radar apparatus of FIG. 1 includes a first secondary echo phase correction unit 7, a first secondary echo removal unit 8 (first multi-order echo removal unit), and a secondary echo power estimation unit 16 ( A multi-order echo power estimation unit), a first primary echo phase correction unit 9, and a first topographic echo removal unit 10 (first primary unwanted wave component removal unit).

The first secondary echo phase correction unit 7 matches the secondary echo so as to cancel the initial phase of the pulse wave transmitted two or more times before the reception signal generated from the reception unit 6. By performing phase correction, a secondary echo area reception signal is generated.
The first secondary echo removal unit 8 obtains a secondary echo component (first Doppler frequency component having excellent power) from the secondary echo reception signal phase-corrected by the first secondary echo phase correction unit 7. Is removed by estimation, and the center Doppler frequency of the detected secondary echo component is calculated.

  The secondary echo power estimation unit 16 calculates the secondary echo intensity (the power removed by the first secondary echo removal unit 8) from the difference in the received signal power before and after the first secondary echo removal unit 8. Calculate by estimation.

The first primary echo phase correction unit 9 outputs the initial pulse wave transmitted immediately before the secondary echo area reception signal after the secondary echo removal output from the first secondary echo removal unit 8. A primary echo area reception signal is obtained by performing phase correction in accordance with the primary echo so as to cancel the phase.
The first terrain echo removal unit 10 uses a low-frequency component (a second wave in which an unnecessary wave is assumed to exist) in a frequency range that can be regarded as a terrain echo from the reception signal phase-corrected by the first primary echo phase correction unit 9. The Doppler frequency component) is removed.

  Further, the radar apparatus of FIG. 1 includes a second primary echo phase correction unit 11, a second topographic echo removal unit 12 (second primary unnecessary wave component removal unit), and a primary topographic echo power estimation unit. 17 (primary unwanted wave power estimation unit), a second secondary echo phase correction unit 13 (second multi-order echo phase correction unit), and a second secondary echo removal unit 14 (second multi-order) An echo removal unit), a third primary echo phase correction unit 15, a reception signal switching unit 19, and a target detection unit 20.

The second primary echo phase correction unit 11 performs phase correction on the reception signal generated from the reception unit 6 in accordance with the primary echo so as to cancel the initial phase of the pulse wave transmitted immediately before. Thus, a primary echo area reception signal is obtained.
The second terrain echo removing unit 12 applies the terrain echo (the power of the third Doppler frequency component in which an unnecessary wave is assumed to exist) to the reception signal phase-corrected by the second primary echo phase correcting unit 11. ) Is removed.

  The primary terrain echo power estimation unit 17 estimates the terrain echo intensity (power removed by the second primary unwanted wave component removal unit) from the difference in received signal power before and after the second terrain echo removal unit 12. Calculated by

  The second secondary echo phase correction unit 13 generates a pulse wave transmitted two or more times before the received signal in the primary echo area from which the unwanted waves have been removed by the second topographic echo removal unit 12. A secondary echo area reception signal is obtained by performing phase correction in accordance with the secondary echo so as to cancel the initial phase.

The second secondary echo removal unit 14 estimates a secondary echo (fourth Doppler frequency component having excellent power) from the reception signal phase-corrected by the second secondary echo phase correction unit 13, Secondary echo removal processing is performed.
The third primary echo phase correction unit 15 converts the received signal output from the second secondary echo removal unit 14 into the primary echo so as to cancel the initial phase of the pulse wave transmitted immediately before. A primary echo area reception signal is obtained by performing phase correction together.

  The reception signal switching unit 19 includes an intensity comparison unit 18 that functions as a processing selection determination unit, and primary unnecessary wave power estimated by the primary terrain echo power estimation unit 17 (primary unnecessary wave power estimation unit), or Based on the secondary echo power estimated by the secondary echo power estimation unit 16 (multi-order echo power estimation unit), the received signal phase-corrected by the third primary echo phase correction unit 15 or the first terrain echo One of the reception signals from which unnecessary waves are removed by the removing unit 10 (first primary unnecessary wave component removing unit) is selected and output.

The intensity comparison unit 18 compares the secondary echo intensity estimated by the secondary echo power estimation unit 16 with the terrain echo intensity estimated by the primary terrain echo power estimation unit 17 and indicates information indicating the magnitude relationship between the two. Is output.
The reception signal switching unit 19 selects a reception signal from either the first topographic echo removal unit 10 or the third primary echo phase correction unit 15 based on the output information from the intensity comparison unit 18. Output.
The target detection unit 20 detects a target signal corresponding to an object existing in the space based on the reception signal output from the reception signal switching unit 19.

Here, since the unnecessary wave in the primary echo area is a “terrain echo”, the first and second terrain echo removal units 10 and 12 need the first and second primary unnecessary. The primary terrain echo power estimation unit 17 is a primary unnecessary wave power estimation unit.
In addition, since the “secondary echo” is taken as an example of the multi-order echo, the first and second secondary echo removal units 8 and 14 become the first and second multi-order echo removal units, and the first and second The second secondary echo phase correction units 7 and 13 are first and second multi-order echo phase correction units, and the secondary echo power estimation unit 16 is a multi-order echo power estimation unit.

Next, a specific operation according to the first embodiment of the present invention shown in FIG. 1 will be described.
First, the reference signal generation unit 1 generates a reference signal that is a source of a transmission signal, and the phase modulation unit 2 performs phase modulation on the reference signal. At this time, a pseudo-random code is used in the phase modulation, and the pseudo-random code is selected by a known code selection unit.

The pulse modulation unit 3 performs pulse modulation on the signal phase-modulated by the phase modulation unit 2 and also performs amplification processing. Here, the transmission signal after pulse modulation and amplification will be referred to as “transmission wave”.
The phase modulation in the phase modulation unit 2 is performed so that the initial phase changes for each pulse wave output from the pulse modulation unit 3.

The reference signal generated from the reference signal generator 1 is a signal having a stable frequency over the time when a plurality of pulse waves are output from the pulse modulator 3.
As a result, it is possible to perform signal processing in consideration of the phase, that is, coherent signal processing, with respect to a reception signal obtained in a time interval in which a plurality of pulse waves 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 is 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. It becomes possible to do.

  That is, when there is a reflective object at a distance exceeding 150 km and a reflected wave from the object is received, the distance is ambiguous. For example, when there is a reflective object at a distance of 200 km, the distance measured from the delay time of the received wave from the object may be 50 km, 200 km, 350 km,. Therefore, phase modulation in the phase modulation unit 2 is performed for the purpose of reducing such ambiguity.

The transmission wave pulsed by the pulse modulation unit 3 is radiated into the space via the transmission / reception switching unit 4 and the antenna 5. When radiated into the 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 5.
At this time, 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 as the antenna 5, beam scanning can be performed by mechanically rotating the antenna 5.
Further, when a phased array antenna is used as the antenna 5, electronic beam scanning is performed by controlling the phase of the elements constituting the antenna 5.

The radio wave (wave) radiated to the space is reflected by an object existing in the beam direction, and a part of the power of the reflected wave returns to the direction in which the radar apparatus exists.
The antenna 5 captures the reflected wave that has reached the radar device as a received wave, and inputs the received wave 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.
In the radar apparatus of FIG. 1, since it is necessary to extract phase information of the received signal, the receiving unit 6 performs phase detection processing. In this phase detection process, the received wave input via the transmission / reception switching unit 4 and a part of the reference signal generated from the reference signal generating unit 1 are mixed to reduce the frequency of the received wave to a low frequency. A converted received signal is generated.

  At this time, the receiving unit 6 divides the reference signal input to the receiving unit 6 into two, one is directly mixed with the received wave, and the other is mixed with the received wave after rotating the phase by 90 degrees. By regarding one of the two reception signals thus generated as a real part and the other as an imaginary part, a reception 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 first secondary echo phase correction unit 7 performs phase correction processing to restore the phase change caused by the phase modulation performed by the phase modulation unit 2 assuming reception of the secondary echo.

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, the phase modulation amount of the i-th transmission pulse in the phase modulation unit 2 is assumed to be φ _i .
At this time, by performing phase correction on the received signal s _i using the phase modulation amount φ _i-1 in the previous pulse transmission (the most recent pulse transmission is defined as the previous one), The signal s _{2nd, i} represented by the equation (1) is obtained.

The signal s _{2nd, i} obtained by Expression (1) will be referred to as a “secondary echo area reception signal”. The secondary echo area reception signal s _{2nd, i} is input to the first secondary echo removal unit 8.
The first secondary echo removal unit 8 detects secondary echoes by Doppler frequency analysis and performs processing to remove them.

Here, the first secondary echo removal unit 8 will be described more specifically with reference to FIG. FIG. 2 is a block diagram showing the internal configuration of the first secondary echo removal unit 8.
In FIG. 2, the first secondary echo removal unit 8 includes a Fourier transform unit 101, a peak detection unit 102, a peak removal unit 103, and an inverse Fourier transform unit 104.

In the first secondary echo removal unit 8, first, the Fourier transform unit 101 performs a Fourier transform on the secondary echo area reception signal (the reception signal phase-corrected by the first secondary echo phase correction unit 7).
At this time, 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.

Subsequently, the peak detection unit 102 detects the Doppler frequency component having the above-described excellent power with the amplitude as a peak and inputs it to the peak removal unit 103.
The peak removing unit 103 performs processing for removing a signal in the vicinity of the frequency region including the Doppler frequency peak-detected by the peak detecting unit 102 from the secondary echo region received signal after Fourier transform input from the Fourier transform unit 101. The peak-detected frequency domain amplitude is set to zero.

The received signal after the Fourier transform from which the secondary echo is removed in this way is input to the inverse Fourier transform 104, and the inverse Fourier transform 104 performs the inverse Fourier transform.
Thereby, the secondary echo area reception signal from the first secondary echo phase correction unit 7 is restored to the reception signal in the time domain, and the first primary echo phase correction unit 9 and the secondary echo power estimation unit 16 is input.

The time domain received signal s ′ _{2nd, i} after the secondary echo removal input from the first secondary echo removal unit 8 to the first primary echo phase correction unit 9 is the first primary echo phase correction unit. 9, the following processing is performed.
First, as shown in the following equation (2), processing for returning the phase correction in accordance with the secondary echo in the secondary echo phase correction unit 7 to the original is performed.

By the processing of Expression (2), the phase change added by the phase modulation unit 2 is reproduced.
Next, phase correction processing in accordance with the primary echo is performed. That is, the received signal s _{1st, i} is obtained by the processing of the following equation (3).

By the processing of Expression (3), for the primary echo, only the phase change caused by the motion of the reflecting object remains in the received signal. This received signal s _{1st, i} will be referred to as a “primary echo area received signal”.

Subsequently, the first terrain echo removing unit 10 removes the terrain echo component by removing the Doppler frequency component having a frequency near zero.
Here, the first topographic echo removal unit 10 will be described more specifically with reference to FIG. FIG. 3 is a block diagram showing the internal configuration of the first topographic echo removal unit 10.
In FIG. 3, the first topographic echo removal unit 10 includes a Fourier transform unit 201, a low frequency removal unit 202, and an inverse Fourier transform unit 203.

Here, an example of removing terrain echoes in the frequency domain is shown.
In the first terrain echo removal unit 10, the received signal in the primary echo region input from the first primary echo phase correction unit 9 is first converted into a frequency domain signal by the Fourier transform unit 201.

Subsequently, the low frequency removing unit 202 removes a component in the vicinity of the frequency 0 as a Doppler frequency component in which a terrain echo exists.
This is because the terrain echo component exists in the vicinity of the frequency 0 when the radar apparatus is fixed on the ground.

Finally, inverse Fourier transform is performed by the inverse Fourier transform unit 203 to return to the time domain received signal and input to the intensity comparing unit 18 in the received signal switching unit 19.
In addition, although the example of the topographic echo removal process in a frequency domain was shown in FIG. 3, you may perform the process which removes a low frequency component in a time domain.

  As described above, in the processing using the functional blocks of the first secondary echo phase correction unit 7 to the first terrain echo removal unit 10, the primary terrain echo is first removed after the secondary echo is removed. To do.

On the other hand, in parallel with the above processing, in the processing using the functional blocks of the second primary echo phase correction unit 11 to the third primary echo phase correction unit 15, first, after removing the primary terrain echo Remove secondary echo.
Hereinafter, the processing contents by the second primary echo phase correction unit 11 to the third primary echo phase correction unit 15 will be described.

First, the second primary echo phase correction unit 11 performs phase correction on the reception signal generated from the reception unit 6 in accordance with the primary echo.
Specifically, phase correction is performed on the received signal s _i using the phase modulation amount φ _i to obtain a primary echo area received signal s _{1st, j} . That is, the following expression (4) is performed.

Subsequently, the second terrain echo removal unit 12 performs terrain echo removal processing on the primary echo area reception signal s _{1st, j} . This operation is the same as the operation of the first topographic echo removal unit 10 described above except that the input signals are different.
Next, the second secondary echo phase correction unit 13 performs phase correction on the input signal s ′ _{1st, j} from the second topographic echo removal unit 12 according to the secondary echo, and uses the following equation: As in (5), the received signal s ″ _{2nd, j} after phase correction is generated.

In addition, the second secondary echo removal unit 14 performs secondary echo removal processing on the received signal s ″ _{2nd, j} obtained by Equation (5). This operation is different in the input signal. Otherwise, the operation is the same as that of the first secondary echo removal unit 8 described above.

Further, the third primary echo phase correction unit 15 performs phase correction again on the output signal of the second secondary echo removal unit 14 according to the primary echo.
The received signal s ″ _{1st, j} after the second phase correction by the third primary echo phase correction unit 15 is expressed as follows using the output signal s ′ ″ _{2nd, j} of the second secondary echo removal unit 14. It is expressed as equation (6).

  As described above, the reception signal (output signal of the first terrain echo removal unit 10) from which unnecessary waves are removed in the order of removal of the secondary echo and primary terrain echo, the removal of the primary terrain echo, and the secondary Two processing results are obtained: a reception signal from which unnecessary waves have been removed (the output signal of the third primary echo phase correction unit 15) in the order of echo removal.

Which of the above two processing results is adopted depends on the magnitude of the secondary echo power calculated by the secondary echo power estimation unit 16 and the primary terrain echo power calculated by the primary terrain echo power estimation unit 17. Determined by relationship.
For this reason, the secondary echo power estimation unit 16 estimates the power of the secondary echo, and the primary landform echo power estimation unit 17 estimates the power of the primary landform echo.

Specifically, the secondary echo power is estimated from the secondary echo power removed by the first secondary echo removal unit 8, that is, the difference between the input power and the output power.
The primary terrain echo power estimation unit 17 estimates the power of the primary terrain echo from the difference between the input power and the output power of the second terrain echo removal unit 12.

In the reception signal switching unit 19, the intensity comparison unit 18 compares the estimated secondary echo power with the primary terrain echo power.
When the primary terrain echo power is larger in accordance with the comparison result of the intensity comparison unit 18, the reception signal switching unit 19 selects a processing result having no characteristic deterioration of the primary terrain echo removal process, and selects the secondary terrain echo. If the echo power is larger, a processing result that does not deteriorate the characteristics of the secondary echo removal processing is selected.

That is, the received signal switching unit 19 selects and outputs the received signal obtained by the third primary echo phase correcting unit 15 if the primary terrain echo power is larger than the secondary echo power.
As a result, the primary terrain echo removal process can be performed without being affected by the secondary echo removal process, and the performance degradation of the primary terrain echo removal can be prevented.

On the other hand, if the secondary echo power is larger than the primary terrain echo power, the reception signal switching unit 19 selects and outputs the reception signal obtained by the first terrain echo removal unit 10.
As a result, the secondary echo removal process can be performed without being affected by the primary terrain echo removal process, and deterioration of the performance of the secondary echo removal can be prevented.

  Here, the received signal is selected according to the comparison result between the secondary echo power and the primary terrain echo power. However, the received signal is not limited to this. When the next terrain echo power is higher than a preset threshold value, the output signal of the third primary echo phase correction unit 15 is selected, and when it is equal to or less than the threshold value, the output signal of the first terrain echo removal unit 10 May be selected.

  As described above, the method of selecting a received signal by paying attention only to the primary terrain echo power is effective when it is assumed that the power of the primary terrain echo existing at a short distance often becomes particularly high. is there. In this case, the secondary echo power estimation unit 16 can be omitted.

  The third primary echo phase correction unit 15 is inserted to make the input signal to the target detection unit 20 a received signal that has undergone phase correction matched to the primary echo. It is assumed that the target detection unit 20 performs Doppler frequency analysis on the primary echo.

Therefore, for example, when the target detection unit 20 does not perform Doppler frequency analysis and performs only power calculation, the third primary echo phase correction unit 15 becomes unnecessary and can be omitted.
In this case, instead of the output signal of the third primary echo phase correction unit 15, the output signal of the second secondary echo removal unit 14 may be used as an input signal to the reception signal switching unit 19.

The comparison processing by the intensity comparison unit 18 includes processing from the first secondary echo phase correction unit 7 to the first secondary echo removal unit 8, and processing from the second primary echo phase correction unit 11 to the second. If the processing up to the terrain echo removal unit 12 is completed, it can be executed.
Therefore, processing from the first primary echo phase correction unit 9 to the first topographic echo removal unit 10 and processing from the second secondary echo phase correction unit 13 to the third primary echo phase correction unit 15 Need not be executed in parallel at the same time, and only one of the necessary processes may be executed when the necessity of the process execution is determined based on the comparison result of the intensity comparison unit 18.

In the above description, an example of processing assuming a “secondary echo” as a multi-order echo has been described. However, the present invention is not limited to a secondary echo, and any multi-order (k-th order) of the third order or higher The echo may be removed.
In this case, in order to correct the phase of the k-th order echo, the phase modulation amount φ _{i−1 + k} may be used instead of the above-described phase modulation amount φ _i−1 .

Moreover, although the example which assumed "terrain echo" as an unnecessary wave of a primary echo area was shown, the case where an unnecessary wave is a "weather echo" may be assumed.
In this case, a means for estimating the Doppler frequency of the weather echo (weather clutter) is required, but no particularly new means is required, and a method similar to conventional weather clutter suppression may be used.

  Finally, the target detection unit 20 detects the target signal based on the reception signal output from the reception signal switching unit 19, but the input signal to the target detection unit 20 removes the primary terrain echo and the secondary echo. In addition, since unnecessary wave elimination processing that reduces the disappearance of unwanted waves is selected according to the situation of unwanted waves included in the original received signal, accurate detection with less false detection becomes possible. .

  As described above, the radar apparatus according to Embodiment 1 (FIGS. 1 to 3) of the present invention radiates a pulse wave in the space and receives a reflected wave scattered by an object existing in the space. In order to measure an object by performing signal processing on a received signal, a phase modulation wave generation unit (reference signal generation unit 1 to pulse modulation unit 3) that generates a pulse wave whose initial phase changes with each transmission And an antenna 5 that radiates a pulse wave as a transmission wave to the space and acquires a reflected wave that arrives from the space as a reception wave, and a reception unit 6 that generates a reception signal by detecting the reception wave. .

  Also, a first secondary echo phase correction unit 7 that performs phase correction to cancel the initial phase of the pulse wave transmitted two or more times before the reception signal generated from the reception unit 6; A first multiple that estimates the first Doppler frequency component having excellent power from the reception signal phase-corrected by the first secondary echo phase correction unit 7 and removes the power of the first Doppler frequency component. A secondary echo removing unit (first secondary echo removing unit 8), a multi-order echo power estimating unit (secondary echo power estimating unit 16) for calculating the power removed by the first multi-order echo removing unit, A first primary echo phase correction unit 9 that performs phase correction on the received signal output from the first multi-order echo removal unit so as to cancel the initial phase of the pulse wave transmitted immediately before; The first echo phase correction unit 9 of the receiver From the signal, the presence of the unnecessary wave and a first primary unnecessary wave component removing unit that removes the second Doppler frequency components are assumed (first ground clutter removal unit 10).

  In addition, a second primary echo phase correction unit 11 that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal generated from the reception unit 6, and a second primary A second primary unwanted wave component removing unit (second terrain echo removing unit) that removes the power of the third Doppler frequency component in which the presence of unnecessary waves is assumed from the reception signal phase-corrected by the echo phase correcting unit 11 Unit 12), a primary unwanted wave power estimation unit (primary landform echo power estimation unit 17) that calculates the power removed by the second primary unwanted wave component removal unit, and a second primary unwanted wave component removal A second multi-order echo phase correction unit (second 2) that performs phase correction to cancel the initial phase of the pulse wave transmitted two or more times before the reception signal from which unnecessary waves have been removed by the unit Secondary echo phase correction unit 13) and second multi-order echo position complementation A second Doppler frequency component that estimates the fourth Doppler frequency component having excellent power and removes the fourth Doppler frequency component from the received signal that has been phase-corrected by the second unit (second secondary echo removal) Unit 14) and a third primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal output from the second multi-order echo removal unit 15.

Further, the third primary echo phase correction unit 15 performs phase correction based on the primary unnecessary wave power estimated by the primary unnecessary wave power estimation unit and the multi-order echo power estimated by the multi-order echo power estimation unit. A received signal switching unit 19 that selects and outputs either the received signal or the received signal from which the unnecessary wave is removed by the first primary unwanted wave component removing unit (first terrain echo removing unit 10). ing.
Thereby, it is possible to realize the secondary echo suppression processing without degrading the target detection performance.

  The received signal switching unit 19 selects the received signal phase-corrected by the third primary echo phase correcting unit 15 when the primary unwanted wave power is larger than the multi-order echo power, and the multi-order echo power is If the power is higher than the primary unwanted wave power, the reception signal from which unwanted waves have been removed by the first primary unwanted wave component removal unit (first topographic echo removal unit 10) is selected.

  If attention is paid only to the primary terrain echo power, the multi-order echo power estimation unit (secondary echo power estimation unit 16) can be omitted. In this case, the reception signal switching unit 19 does not require a primary. When the wave power is higher than a preset threshold value, the received signal whose phase is corrected by the third primary echo phase correction unit 15 is selected, and when the primary unnecessary wave power is equal to or lower than the threshold value, the first The reception signal from which unnecessary waves have been removed by the first unnecessary wave component removing unit (first terrain echo removing unit 10) is selected.

  In addition, the third primary echo phase correction unit 15 can be omitted depending on the processing content of the target detection unit 20, and in this case, the reception signal switching unit 19 has multiple primary unwanted wave powers. When it is larger than the echo power, the received signal output from the second multi-order echo removal unit (second secondary echo removal unit 14) is selected, and the multi-order echo power is higher than the primary unwanted wave power. If larger, the received signal from which unnecessary waves have been removed by the first primary unwanted wave component removing unit (first topographic echo removing unit 10) is selected.

  Further, when both the third primary echo phase correction unit 15 and the multi-order echo power estimation unit (secondary echo power estimation unit 16) are omitted, the reception signal switching unit 19 sets the primary unwanted wave power in advance. If the received signal output from the second multi-order echo removing unit (second secondary echo removing unit 14) is selected and the primary unwanted wave power is below the threshold, The reception signal from which unnecessary waves have been removed by the first primary unnecessary wave component removing unit (first topographic echo removing unit 10) is selected.

Embodiment 2. FIG.
In the first embodiment (FIGS. 1 to 3), a process with less deterioration in unnecessary wave removal performance is selected according to the power levels of secondary echoes and primary terrain echoes that are unnecessary waves. Although configured, it is considered that the power of the primary terrain echo is often larger than the power of the secondary echo. Therefore, as shown in FIG. 4, the first secondary echo phase in FIG. The correction unit 7 to the first terrain echo removal unit 10 and the secondary echo power estimation unit 16 to the reception signal switching unit 19 can be omitted.

FIG. 4 is a block diagram showing a configuration of a radar apparatus according to Embodiment 2 of the present invention. Components similar to those described above (see FIG. 1) are denoted by the same reference numerals as those described above or “ Detailed description is omitted with “A”.
In the second embodiment of the present invention, the processing is fixed so as to give priority to the removal performance of the primary terrain echo power.

In FIG. 4, the receiving unit 6 includes a first primary echo phase as a configuration corresponding to the second primary echo phase correction unit 11 to the third primary echo phase correction unit 15 described above (FIG. 1). A correction unit 11A, a terrain echo removal unit 12A, a secondary echo phase correction unit 13A, a secondary echo removal unit 14A, and a second primary echo phase correction unit 15A are connected.
In this case, the output signal of the second primary echo phase correction unit 15A is directly input to the target detection unit 20.

Here, the reason why the power of the primary terrain echo is larger than the power of the secondary echo will be described.
In general, terrain echo is a reflected wave generated in an artificial structure such as a building or an object with high radio wave reflectance such as a mountainous area and generated in the primary echo area. There is little attenuation of radio waves.

  On the other hand, the secondary echo is a reflected wave from a long distance, has a large distance attenuation, and has a low power because the reflection source is rain. In addition, from a long distance, the reflected wave from the vicinity of the ground surface such as an artificial structure or a mountainous region is not often included due to the influence of the curvature of the earth, so that the electric power does not become large.

Next, a specific operation according to the second embodiment of the present invention shown in FIG. 4 will be described.
First, the process from radiating a transmission wave to space and obtaining a reception signal from the received reflected wave by the reception unit 6 is the same as described above.
Thereafter, in FIG. 1 (FIG. 1), two kinds of unnecessary wave removal signal processing are executed, but in FIG. 4, the first primary echo phase correction unit 11A to the second primary echo phase correction unit 15A are included. Only one unnecessary wave elimination process is executed.

4 assumes that the power of the primary terrain echo is often larger than the power of the secondary echo, and removes the primary terrain echo (removal of unnecessary waves with low performance degradation). It means to execute fixedly.
The operations of the first primary echo phase correction unit 11A to the second primary echo phase correction unit 15A are the same as those of the second primary echo phase correction unit 11 to the third primary echo phase correction described above (FIG. 1). The operation is the same as that of the unit 15.

Similarly to the above, the second primary echo phase correction unit 15A is unnecessary and can be omitted when the target detection unit 20 does not perform Doppler frequency analysis.
In this case, the output signal of the secondary echo removal unit 14A may be directly input to the target detection unit 20 instead of the output signal of the second primary echo phase correction unit 15A.

  Here, when the configuration of the second embodiment (FIG. 4) of the present invention is compared with the conventional signal processing configuration described in Non-Patent Document 1 described above, in the conventional signal processing configuration, the second echo is applied. Phase correction is performed to remove secondary echo, and then phase correction to the primary echo is performed to remove primary terrain echo and target detection of the primary echo area is performed. The phase correction to the echo and the phase correction to the primary echo are performed twice.

On the other hand, in the signal processing according to the second embodiment (FIG. 4) of the present invention, in addition to the phase correction to the primary echo and the phase correction to the secondary echo, the phase correction to the primary echo is performed again. 3 phase corrections are required.
Therefore, according to the second embodiment (FIG. 4) of the present invention, the amount of calculation processing increases as the number of times of phase correction is larger than in the conventional processing, but the disappearance of the primary terrain echo, which is a large power, remains. It is possible to obtain an effect of reduction as compared with the case of conventional processing.

  Further, when compared with the first embodiment (FIG. 1), the amount of signal processing is lower than that of the above-described (FIG. 1), so that the hardware cost of signal processing can be reduced. In many cases, unwanted waves disappear less than in the conventional method, and it is possible to obtain good target detection performance.

  As described above, the radar apparatus according to Embodiment 2 (FIG. 4) of the present invention cancels the initial phase of the pulse wave transmitted immediately before the received signal generated from the receiving unit 6. The power of the first Doppler frequency component in which the presence of unnecessary waves is assumed from the first primary echo phase correction unit 11A that performs correction and the received signal that has been phase corrected by the first primary echo phase correction unit 11A Pulse wave transmitted at least twice a predetermined number of times with respect to the received signal from which the unwanted wave is removed by the primary unwanted wave component removing unit (terrain echo removing unit 12A) and the primary unwanted wave component removing unit A second-order echo phase correction unit (secondary echo phase correction unit 13A) that performs phase correction that cancels the initial phase of the second signal, and a second signal that has excellent power from the received signal phase-corrected by the multi-order echo phase correction unit. Doppler frequency generation To estimate, and a multi-order echo removal section for removing the power of the second Doppler frequency components (secondary echo removing portion 14A).

Further, in accordance with the processing content of the target detection unit 20, a second correction is performed for the received signal output from the multi-order echo removal unit so as to cancel the initial phase of the pulse wave transmitted immediately before. A next echo phase correction unit 15A is provided.
As a result, the same operational effects as described above can be obtained, and the amount of calculation of signal processing is lower than that of the first embodiment (FIG. 1), so that the hardware cost of signal processing can be reduced.

  1 reference signal generation unit (phase modulation wave generation unit), 2 phase modulation unit (phase modulation wave generation unit), 3 pulse modulation unit (phase modulation wave generation unit), 4 transmission / reception switching unit, 5 antenna, 6 reception unit, 7 1st secondary echo phase correcting unit (first multi-order echo removing unit), 8 1st secondary echo removing unit, 9 1st primary echo phase correcting unit, 10 1st topographic echo removing unit ( 1st primary unwanted wave component removal unit), 11 2nd primary echo phase correction unit, 11A primary echo phase correction unit, 12 second terrain echo removal unit (second primary unwanted wave component removal unit) ), 12A Terrain echo removal unit (primary unwanted wave component removal unit), 13 Second secondary echo phase correction unit (second multi-order echo phase correction unit), 13A Secondary echo phase correction unit (multi-order echo) Phase correction unit), 14 second secondary echo removal unit (second multi-order echo removal unit) , 14A secondary echo removal unit (multi-order echo removal unit), 15 third primary echo phase correction unit, 15A second primary echo phase correction unit, 16 secondary echo power estimation unit (multi-order echo power estimation unit) Part), 17 primary terrain echo power estimation part (primary unnecessary wave power estimation part), 18 intensity comparison part, 19 received signal switching part, 20 target detection part.

Claims (8)

In a radar apparatus that radiates a pulsed wave in space, receives a reflected wave scattered by an object existing in the space, and measures the object by performing signal processing on a received signal,
A phase-modulated wave generating unit that generates a pulse wave whose initial phase changes with each transmission;
An antenna that radiates the pulse wave to the space as a transmission wave and acquires a reflected wave that has arrived from the space as a reception wave;
A reception unit that generates a reception signal by detecting the reception wave;
A first secondary echo phase correction unit that performs phase correction to cancel the initial phase of a pulse wave transmitted two or more times before the reception signal generated from the reception unit;
A first Doppler frequency component having an excellent power is estimated from the received signal phase-corrected by the first secondary echo phase correction unit, and the first Doppler frequency component power is removed. A multi-order echo removal unit;
A multi-order echo power estimator that calculates the power removed by the first multi-order echo remover;
A first primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal output from the first multi-order echo removal unit;
A first primary unnecessary wave component removing unit that removes a second Doppler frequency component in which an unnecessary wave is assumed to exist from the reception signal phase-corrected by the first primary echo phase correcting unit;
A second primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal generated from the reception unit;
A second primary unwanted wave component removing unit that removes power of a third Doppler frequency component in which the presence of an unwanted wave is assumed from the reception signal phase-corrected by the second primary echo phase correcting unit;
A primary unwanted wave power estimation unit that calculates the power removed by the second primary unwanted wave component removal unit;
A second multi-phase correction that cancels out the initial phase of the pulse wave transmitted two or more times before the received signal from which the unnecessary wave is removed by the second primary unwanted wave component removing unit; A next echo phase correction unit;
A second multi-order echo that estimates a fourth Doppler frequency component having excellent power from the received signal phase-corrected by the second multi-order echo phase correction unit and removes the fourth Doppler frequency component. A removal section;
A third primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal output from the second multi-order echo removal unit;
Based on the primary unwanted wave power estimated by the primary unwanted wave power estimation unit and the multi-order echo power estimated by the multi-order echo power estimation unit, the phase is corrected by the third primary echo phase correction unit. And a received signal switching unit that selects and outputs either the received signal or the received signal from which the unnecessary wave has been removed by the first primary unwanted wave component removing unit. In a radar apparatus that radiates a pulsed wave in space, receives a reflected wave scattered by an object existing in the space, and measures the object by performing signal processing on a received signal,
A phase-modulated wave generating unit that generates a pulse wave whose initial phase changes with each transmission;
An antenna that radiates the pulse wave to the space as a transmission wave and acquires a reflected wave that has arrived from the space as a reception wave;
A reception unit that generates a reception signal by detecting the reception wave;
A first secondary echo phase correction unit that performs phase correction to cancel the initial phase of a pulse wave transmitted two or more times before the reception signal generated from the reception unit;
A first Doppler frequency component having an excellent power is estimated from the received signal phase-corrected by the first secondary echo phase correction unit, and the first Doppler frequency component power is removed. A multi-order echo removal unit;
A multi-order echo power estimator that calculates the power removed by the first multi-order echo remover;
A first primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal output from the first multi-order echo removal unit;
A first primary unnecessary wave component removing unit that removes a second Doppler frequency component in which an unnecessary wave is assumed to exist from the reception signal phase-corrected by the first primary echo phase correcting unit;
A second primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal generated from the reception unit;
A second primary unwanted wave component removing unit that removes power of a third Doppler frequency component in which the presence of an unwanted wave is assumed from the reception signal phase-corrected by the second primary echo phase correcting unit;
A primary unwanted wave power estimation unit that calculates the power removed by the second primary unwanted wave component removal unit;
A second multi-phase correction that cancels out the initial phase of the pulse wave transmitted two or more times before the received signal from which the unnecessary wave is removed by the second primary unwanted wave component removing unit; A next echo phase correction unit;
A second multi-order echo that estimates a fourth Doppler frequency component having excellent power from the received signal phase-corrected by the second multi-order echo phase correction unit and removes the fourth Doppler frequency component. A removal section;
Based on the primary unwanted wave power estimated by the primary unwanted wave power estimation unit and the multi-order echo power estimated by the multi-order echo power estimation unit, the reception output from the second multi-order echo removal unit A radar apparatus comprising: a reception signal switching unit that selects and outputs either a signal or a reception signal from which unnecessary waves have been removed by the first primary unnecessary wave component removal unit. The received signal switching unit is
If the primary unwanted wave power is greater than the multi-order echo power, select the received signal phase-corrected by the third primary echo phase correction unit,
2. The reception signal from which unnecessary waves have been removed by the first primary unwanted wave component removing unit is selected when the multi-order echo power is larger than the primary unwanted wave power. The radar apparatus described. The received signal switching unit is
If the primary unwanted wave power is greater than the multi-order echo power, select the received signal output from the second multi-order echo removal unit,
3. The reception signal from which unnecessary waves have been removed by the first primary unwanted wave component removing unit is selected when the multi-order echo power is larger than the primary unwanted wave power. The radar apparatus described. In a radar apparatus that radiates a pulsed wave in space, receives a reflected wave scattered by an object existing in the space, and measures the object by performing signal processing on a received signal,
A phase-modulated wave generating unit that generates a pulse wave whose initial phase changes with each transmission;
An antenna that radiates the pulse wave to the space as a transmission wave and acquires a reflected wave that has arrived from the space as a reception wave;
A reception unit that generates a reception signal by detecting the reception wave;
A first secondary echo phase correction unit that performs phase correction to cancel the initial phase of a pulse wave transmitted two or more times before the reception signal generated from the reception unit;
A first Doppler frequency component having an excellent power is estimated from the received signal phase-corrected by the first secondary echo phase correction unit, and the first Doppler frequency component power is removed. A multi-order echo removal unit;
A first primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal output from the first multi-order echo removal unit;
A first primary unnecessary wave component removing unit that removes a second Doppler frequency component in which an unnecessary wave is assumed to exist from the reception signal phase-corrected by the first primary echo phase correcting unit;
A second primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal generated from the reception unit;
A second primary unwanted wave component removing unit that removes power of a third Doppler frequency component in which the presence of an unwanted wave is assumed from the reception signal phase-corrected by the second primary echo phase correcting unit;
A primary unwanted wave power estimation unit that calculates the power removed by the second primary unwanted wave component removal unit;
A second multi-phase correction that cancels out the initial phase of the pulse wave transmitted two or more times before the received signal from which the unnecessary wave is removed by the second primary unwanted wave component removing unit; A next echo phase correction unit;
A second multi-order echo that estimates a fourth Doppler frequency component having excellent power from the received signal phase-corrected by the second multi-order echo phase correction unit and removes the fourth Doppler frequency component. A removal section;
A third primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal output from the second multi-order echo removal unit;
Based on the primary unwanted wave power estimated by the primary unwanted wave power estimation unit, the received signal phase-corrected by the third primary echo phase correction unit or the first primary unwanted wave component removal unit A radar apparatus comprising: a reception signal switching unit that selects and outputs any one of reception signals from which unnecessary waves have been removed. In a radar apparatus that radiates a pulsed wave in space, receives a reflected wave scattered by an object existing in the space, and measures the object by performing signal processing on a received signal,
A phase-modulated wave generating unit that generates a pulse wave whose initial phase changes with each transmission;
An antenna that radiates the pulse wave to the space as a transmission wave and acquires a reflected wave that has arrived from the space as a reception wave;
A reception unit that generates a reception signal by detecting the reception wave;
A first secondary echo phase correction unit that performs phase correction to cancel the initial phase of a pulse wave transmitted two or more times before the reception signal generated from the reception unit;
A first Doppler frequency component having an excellent power is estimated from the received signal phase-corrected by the first secondary echo phase correction unit, and the first Doppler frequency component power is removed. A multi-order echo removal unit;
A first primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal output from the first multi-order echo removal unit;
A first primary unnecessary wave component removing unit that removes a second Doppler frequency component in which an unnecessary wave is assumed to exist from the reception signal phase-corrected by the first primary echo phase correcting unit;
A second primary echo phase correction unit that performs phase correction to cancel the initial phase of the pulse wave transmitted immediately before the reception signal generated from the reception unit;
A second primary unwanted wave component removing unit that removes power of a third Doppler frequency component in which the presence of an unwanted wave is assumed from the reception signal phase-corrected by the second primary echo phase correcting unit;
A primary unwanted wave power estimation unit that calculates the power removed by the second primary unwanted wave component removal unit;
A second multi-phase correction that cancels out the initial phase of the pulse wave transmitted two or more times before the received signal from which the unnecessary wave is removed by the second primary unwanted wave component removing unit; A next echo phase correction unit;
A second multi-order echo that estimates a fourth Doppler frequency component having excellent power from the received signal phase-corrected by the second multi-order echo phase correction unit and removes the fourth Doppler frequency component. A removal section;
Based on the primary unwanted wave power estimated by the primary unwanted wave power estimation unit, the received signal output from the second multi-order echo removal unit or the unwanted wave by the first primary unwanted wave component removal unit A radar apparatus comprising: a received signal switching unit that selects and outputs one of the removed received signals. The received signal switching unit is
If the primary unwanted wave power is higher than a preset threshold, select the received signal phase-corrected by the third primary echo phase correction unit,
The radar apparatus according to claim 5, wherein when the primary unnecessary wave power is equal to or less than the threshold value, a reception signal from which unnecessary waves have been removed by the first primary unnecessary wave component removing unit is selected. . The received signal switching unit is
If the primary unwanted wave power is higher than a preset threshold, select the received signal output from the second multi-order echo removal unit,
The radar apparatus according to claim 6, wherein when the primary unwanted wave power is equal to or less than the threshold value, a reception signal from which unwanted waves are removed by the first primary unwanted wave component removal unit is selected. .

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