JP2009128278A - Pulse compression radar device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a range side lobe while avoiding an effect due to signal distortion in a transmission and reception system without providing a special circuit for shaping a transmission waveform in a pulse compression radar device with a narrow transmission pulse width. <P>SOLUTION: A range side lob removal means is provided, which estimates amplitude of the range side lobe appearing before and after a target signal in a range direction from a pulse compression signal, subtracts the estimated amplitude of the range side lobe from the pulse compression signal, and reduces the range side lobe. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pulse compression radar apparatus that requires a high compression ratio and detects a long distance.

  A pulse compression radar apparatus is a radar apparatus that realizes detection performance equivalent to a high-power radar apparatus while having a small peak power by transmitting a pulse signal that is longer than a normal pulse radar apparatus and frequency-modulated. It is. The pulse compression process is performed by calculating a correlation between the reference signal based on the transmission signal and the reception signal. The correlation calculation is calculated by time axis processing or frequency axis processing.

  Time axis processing is a processing method based on product-sum operation on the time axis of a reference signal and a received signal. The frequency axis processing converts the reference signal and the received signal into frequency axis data by Fourier transform, calculates the product of the Fourier transform results for each frequency component, and returns the result to time axis data by inverse Fourier transform It is a technique. When the transmission pulse becomes longer, the number of product-sum operations is enormous in the time axis processing, but in the frequency axis processing, the Fourier transform can be speeded up by the fast Fourier transform, so the amount of computation is reduced compared to the time axis processing. it can.

  However, in general, when the transmission pulse suddenly rises at the beginning of the pulse and falls suddenly at the end of the pulse so that the envelope of the transmission signal becomes rectangular, the transmission / reception system instantaneously appears at both ends of the transmission pulse. Since high frequency components deviating from the pass band appear, the transmission / reception signal is distorted due to the band limitation when the transmission / reception system passes. The distortion causes range side lobes. The range side lobe has an amplitude of about −40 dB when normalized by the signal amplitude, and in the case of reflection by a huge target, the range side lobe may have an amplitude 20 dB or more larger than noise. In such a case, the range side lobe is also clearly displayed on the indicator of the radar apparatus.

Non-Patent Document 1 describes that the range side lobe is reduced by controlling the amplitude of the transmission signal, paying attention to the cause of such a range side lobe being distortion at both ends of the transmission signal. .
K. Nagagawa, H. Hanado, K. Fukutani, T. Iguchi, “Development of a C-Band Pulse Compression Weather Radar,” 32nd Conference on Radar Meteorology (AMS), No. P12R.11, Oct., 2005.

  However, in the case of a radar apparatus in which the width of the transmission pulse has a short width of about several microseconds, for example, it is difficult to perform a stable window function calculation (amplitude control) with a desired function form.

  Therefore, in the pulse compression processing in the frequency axis processing, instead of directly using the Fourier transform result of the reference signal based on the transmission signal, the range is obtained by using the compression coefficient that is secondarily derived using the Fourier transform result. A pulse compression radar apparatus having a small side lobe has been proposed by the inventors of the present application (Japanese Patent Application No. 2007-006785; hereinafter referred to as the prior application invention).

  In principle, the invention of the prior application can reduce the range side lobe. However, in a realistic pulse compression radar apparatus, the signal is distorted in the transmission / reception path, so that an ideal result may not be obtained. If there is a correlation error in pulse compression processing due to distortion in the transmission / reception path, range side lobes larger than the level assumed before and after the target signal appear when viewed in the range direction (distance direction). End up.

  In view of the above problems, the present invention provides a transmission / reception system in a transmission / reception system without providing a special circuit for shaping a transmission waveform in a pulse compression radar apparatus having a narrow transmission pulse width, for example, several microseconds or less. The object is to reduce the range side lobes while avoiding the influence of signal distortion.

The pulse compression radar apparatus according to claim 1 transmits a modulated pulsed transmission signal to the outside, receives the reflected signal reflected outside as a reception signal, and receives a reference signal based on the transmission signal and the reception In a pulse compression radar apparatus that obtains a pulse-compressed amplitude signal (hereinafter referred to as a pulse compression signal) by performing correlation processing with a signal,
A range side that reduces the range side lobe by predicting the amplitude of the range side lobe that appears before and after the target signal in the range direction based on the pulse compression signal and subtracting the predicted amplitude of the range side lobe from the pulse compression signal. It has a lobe removal means.

The pulse compression radar apparatus according to claim 2 is the pulse compression radar apparatus according to claim 1, wherein the range side lobe removing means is
One target cell in the center, a first predetermined number (Ng / 2) of guard cells on each side of the target cell, and a second predetermined number (Nr / 2) on the opposite side of the target cell of the guard cell group ) With a reference cell group,
An input / shift means for inputting a pulse compression signal at an input timing synchronized with a sampling clock from one direction to the shift register, and shifting the input pulse compression signal from the upstream side to the downstream side in the shift register;
A sum calculating means for calculating a sum of pulse compression signals existing in each cell of the reference cell group in synchronization with each input timing;
Multiplication means for multiplying the sum of pulse compression signals of the sum calculation means by a preset coefficient to obtain a predicted sidelobe amplitude;
Subtracting means for obtaining a subtraction value by subtracting the predicted sidelobe amplitude of the multiplication means from a pulse compression signal existing in the cell of interest in synchronization with the sampling clock.

  The pulse compression radar apparatus according to a third aspect of the present invention is the pulse compression radar apparatus according to the second aspect, wherein if the subtraction value from the subtraction means is a positive value, the subtraction value is output and a negative value is output. In some cases, there is a selection output means for outputting a zero value instead of the subtraction value.

The pulse compression radar apparatus according to claim 4 is the pulse compression radar apparatus according to claim 2, wherein the sum calculation means includes:
A first adder that adds the pulse compression signal of the reference cell closest to the one-direction side of the reference cell group upstream of the shift register to the target cell and the sum value stored in the sum register; A second adder for subtracting the pulse compression signal of the guard cell closest to the one-way side of the guard cell group upstream of the shift register from the addition value of one adder, and the addition of the second adder A third adder for adding the value and the pulse compression signal of the reference cell closest to the one-direction side of the reference cell group downstream of the shift register to the target cell, and the addition value of the third adder A fourth adder for subtracting a pulse compression signal that has passed through a reference cell that is most opposite to the one direction of the reference cell group on the downstream side of the shift register from the target cell;
The pulse compression signal sum which is the addition value of the fourth adder is output and stored as a sum value in the sum register.

  According to the pulse compression radar apparatus of the present invention, it is possible to eliminate the range side lobe amplitude generated when the received signal having a large reflected power is subjected to pulse compression while predicting. As a result, blurring of a large ship or a short-distance coastline can be eliminated, and a radar device image with a clear outline can be obtained.

  In addition, the range side lobe can be corrected and a clear radar device image can be obtained without using a circuit for controlling the amplitude of the transmission signal. Even in a pulse compression radar device with amplitude control, if the target amplitude after pulse compression is much larger than the noise, the same problem will occur because the range side lobe cannot be suppressed. In contrast, a clear radar apparatus image can be obtained by the present invention.

  The present invention transmits a modulated pulsed transmission signal to the outside, receives the reflected signal reflected outside as a reception signal, and performs correlation processing between the reference signal and the reception signal based on the transmission signal. In a pulse compression radar device that obtains a pulse-compressed amplitude signal (hereinafter referred to as a pulse compression signal), the amplitude of a range sidelobe that appears before and after the target signal in the range direction is predicted based on the pulse compression signal. The range side lobe is reduced by subtracting the amplitude of the range side lobe from the pulse compression signal.

  First, the properties known about the range side lobe include where the range side lobe appears and its length, and the amplitude of the range side lobe. When viewed in the range direction, the range side lobe appears before and after the target signal, and appears over a distance corresponding to a time substantially equal to the pulse width. The amplitude of the range side lobe depends on the pulse width. The range sidelobe amplitude normalized by the amplitude of the target signal increases when the pulse width is short, and decreases when the pulse width is increased. For example, when the envelope of the transmission signal is rectangular, a range side lobe of −35 to −40 dB appears with a pulse width of about 5 microseconds, and a range side lobe of −40 to −45 dB with a pulse width of about 10 microseconds. Appears. This corresponds to the fact that the contribution rate of distortion at both ends of the transmission pulse becomes small when the pulse width is long. Further, the position, length, and amplitude of the range side lobe basically do not depend on the frequency shift width of the transmission signal.

  These properties are properties discovered by the inventor during the evaluation process of the pulse compression radar apparatus, and are facts that have been demonstrated in numerical simulations.

  Thus, the appearance position and the amplitude of the range side lobe depend on the transmission signal setting (eg, pulse width) and can be easily predicted. The range side lobe can be removed by subtracting the amplitude value from the amplitude information present at the expected position by the amplitude of the expected range side lobe. Such a process can be realized by the method of FIG. 1 illustrating the concept of range sidelobe removal. The diagram on the left side of FIG. 1 shows the amplitude of the pulse compression signal obtained by pulse compression. In this figure, the horizontal axis represents the range, and the vertical axis represents the reception amplitude corresponding to each range. In this figure, the range side lobe is emphasized, but the actual range side lobe amplitude is 0.03 times or less the target signal amplitude (the average size is, for example, a fraction thereof) To several tens of minutes 1). In the case of a ship radar or the like, in the case of a large target such as a tanker or a structure such as a bank, the side lobe level is higher than the noise floor, so that they are displayed on the screen of the display.

  Regarding processing, a processing window is defined that has one target cell in the center, a plurality of guard cells on both sides thereof, and a plurality of correction cells on both sides thereof. The number of guard cells may be about twice the distance resolution after pulse compression on both sides, and the number of correction cells may be the number of cells corresponding to the pulse width on each side.

  As a specific example, if the pulse width is 8 microseconds, the frequency shift width of chirp (eg, linear frequency modulation) is 8 MHz, and the sampling frequency is 40 MHz, 10 guard cells are corrected on both sides of the target cell. Further, 320 cells are required outside the cell. The correction cell corrects the amplitude value of the corresponding range while moving the processing window one by one from the smaller range to the larger range. Keep the range that the guard cell supports. The amplitude values of all the correction cells are reduced by the product obtained by multiplying the target cell by a specified coefficient (for example, the reciprocal of the number of cells corresponding to the pulse width). If the subtracted result is negative, replace the result with zero. The prescribed coefficient is a value determined by the amplitude of the assumed range side lobe, that is, a value determined by the pulse width to be transmitted. For this reason, the specified value may be fixedly given by the apparatus. The default value may be mounted so that it can be finely adjusted. The result of performing the range side lobe removal processing is shown on the right side of FIG. 1 and shows that the target signal remains and the range side lobe is removed.

  This method corrects the amplitude value of the correction cell without determining whether or not the target cell is a target signal. That is, the amplitude of the target signal is also subtracted by the range side lobe. A range of the processing window in which the amplitude of the target signal is subtracted is schematically shown in FIG. FIG. 2 shows the range of the processing window that affects the target signal. Referring to FIG. 2, the amplitude of the target signal is eventually subtracted by an amount obtained by multiplying the sum of the range side lobe amplitudes by a specified coefficient. This prescribed coefficient may be, for example, the reciprocal of the number of cells corresponding to the pulse width. Actually, the product obtained by multiplying the sum of the range sidelobe amplitudes by a specified value sufficiently smaller than 1 (for example, the reciprocal of the number of cells corresponding to the pulse width) is a value sufficiently smaller than the amplitude of the target signal. It becomes. Eventually, this product is a subtraction amount that scrapes off the amplitude of the pulse compression signal, but since the value is sufficiently small with respect to the amplitude of the target, no particular problem occurs.

  FIG. 3 is a flowchart showing a first embodiment for realizing the range side lobe removal of FIG. The processing of FIG. 3 is data processing for an array as shown in FIG. 4 in which the amplitude of the pulse compression signal after pulse compression is stored in a storage means such as a shift register. The i-th amplitude data that is the cell of interest stored in this array is A [i]. 3 and 4, the length of the amplitude data array is assumed to be L. Symbols in FIG. 3 and FIG. 4 are as follows: A []... Array storing amplitude data for sidelobe removal processing, L... Length of array A [], i. ,...,... Amplitude value (ie, A [i]) stored in the cell of interest, s... Subtraction amount for sidelobe removal, j... Current position of correction cell, Ng ... Number of guard cells (Ng / 2 each for left and right), Nr ... Number of correction cells (Nr / 2 each for left and right).

  According to the flowchart of FIG. 3, the following processing is performed while shifting the position i of the target cell one by one.

  The value A [i] of the target cell is extracted and set as the target data α. The product s is obtained by multiplying this value α by a specified coefficient (specified value). The product value s becomes the subtraction amount s used for sidelobe removal.

The amplitude is subtracted from all the correction cells j for the target cell position i. That is, all correction cells j; j = i− (Nr + Ng) / 2,..., I−Ng / 2-1 and j = i + Ng / 2 + 1,..., I + (Nr + Ng) / 2
For example, A [k] ← max (A [k] −s, 0) is executed for the correction cell position k. Here, the function max (a, b) outputs the larger value of the two given arguments. That is, in this amplitude subtraction, when the subtraction amount s is subtracted from the original amplitude and the result becomes a negative number, the result is set to 0.

  In executing this processing, when the position i of the target cell is close to the end of the array (that is, when i is a value close to 0 or L−1), the processing cell exceeds the effective range of the array. Naturally, measures are necessary. For example, when the processing cell exceeds the effective range of the array, a condition may be set so that the processing is not performed, and the sidelobe removal processing is performed without a condition if a spare cell is provided as shown in FIG. it can.

  FIG. 5 shows a side lobe removal circuit 100 showing a second embodiment for realizing the range side lobe removal of FIG. In the processing according to the first embodiment shown in FIG. 3, the amplitude data is rewritten many times before the amplitude for one range is determined. In particular, when this is implemented as hardware, it is necessary to form a two-layered loop as shown in the flowchart of FIG.

  The side lobe removal circuit 100 shown in FIG. 5 includes one attention cell 11 in the center, a first predetermined number (Ng / 2) of guard cell groups 12 and 13 on both sides of the attention cell, and the attention cell of the guard cell group. A shift register 10 having a second predetermined number (Nr / 2) of reference cell groups 14 and 15 on the opposite side, and a pulse at an input timing synchronized with the sampling clock from one direction (left side in the figure) to the shift register 10 A compressed signal is input, and the input pulse compression signal is input from the upstream side (reference cell group 14 side when viewed from the target cell 11) to the downstream side (reference cell group 15 side when viewed from the target cell 11). And input / shift means (not shown) for shifting to), and sum calculation means for calculating the sum of pulse compression signals existing in each cell of the reference cell groups 14 and 15 in synchronization with each input timing ( (Sum calculation unit) 20, multiplication means 30 for multiplying the sum of pulse compression signals of sum calculation means 20 by a preset coefficient to obtain a predicted sidelobe amplitude, and a target cell in synchronization with the sampling clock. A subtracting means 40 that obtains a subtraction value by subtracting the predicted sidelobe amplitude of the multiplication means 30 from the pulse compression signal. If the subtraction value from the subtraction means 40 is a positive value, the subtraction value is output, and a negative value is output. In some cases, there is selection output means (max) 50 for outputting a zero value instead of the subtraction value.

  The side lobe removal circuit 100 shown in FIG. 5 includes one target cell 11, Ng / 2 guard cells 12 and 13 on both sides thereof, and Nr / 2 reference cells 14 and 15 on the outside thereof. The shift register 10 is used. An amplitude value corresponding to each range obtained by pulse compression is input to the shift register 19 from the left side of the shift register 10 in synchronization with the sampling clock. The input amplitude value moves one by one from the left (upstream side) to the right (downstream side) cell in synchronization with the sampling clock.

  In the sidelobe removal circuit 100 in FIG. 5, the relationship between the target cell and the correction cell in FIG. The reference cell in FIG. 5 corresponds to the target cell in FIG. 1, and the target cell in FIG. 5 corresponds to the correction cell in FIG. When attention is paid to a specific range, in the method of FIG. 1, the correction cell in the processing window continues to undergo amplitude correction while passing through the range, whereas in the method of FIG. It is corrected only when it passes. Although the number of corrections is one, the correction amount of the target cell 11 in the method of FIG. 5 is obtained from the sum of the values held in all the reference cells, so the method of FIG. It can be seen that this is an algorithm for obtaining

  As a feature of the method of FIG. 5, if the main lobe of the target signal is included somewhere in the reference cell, the sum of the values held in the reference cell becomes large. Get the correction. Conversely, if the main lobe of the target signal is not included in the reference cell, the sum of the values held in the reference cell is small, and the correction amount is sufficiently small. In the method of FIG. 1, the number of correction cells is increased when the transmission pulse width is long. Similarly, the method of FIG. 5 should also increase the number of reference cells when the transmission pulse is long. Specifically, the reference cell number Nr / 2 on one side may be set to the number of cells corresponding to the transmission pulse width. If the transmission pulse width is T and the sampling frequency is fs, Nr / 2 = T * fs. For example, if the pulse width is 8 microseconds and the sampling frequency is 40 MHz, 320 reference cells are required outside the guard cell.

  As for the guard cell, when the target cell is the apex of the main lobe of the target signal, it should be selected so that a part of the main lobe is not included in the reference cell. This is because when the same main lobe extends over the target cell and the reference cell, the main lobe itself is in a state of being largely corrected. When the frequency shift width of the chirp signal to be transmitted is B, the range resolution defined by the 4 dB attenuation width of the main lobe in the pulse compression result is about 1 / B. When the target cell is the apex of the main lobe, in order to prevent a part of the same main lobe from being included in the reference cell, the guard cell on one side may be about twice the range resolution. Therefore, the number of guard cells on one side is Ng / 2 = 2fs / B. For example, when the frequency shift width of the chirp is 8 MHz and the sampling frequency is 40 MHz, the number of guard cells on one side is 10.

  5 can be realized with four adders and one total register, as shown in FIG. That is, the first adder 21 that adds the pulse compression signal of the reference cell on the most unidirectional side of the reference cell group 14 upstream of the shift register 10 and the sum value stored in the sum register 25 to the target cell 11. A second adder 12 for subtracting the pulse compression signal of the guard cell in the most unidirectional side of the guard cell group 12 on the upstream side of the shift register 10 from the added value of the first adder 21; A third adder 23 for adding the added value of the second adder 12 and the pulse compression signal of the reference cell on the most unidirectional side of the reference cell group 15 on the downstream side of the shift register 10 to the target cell 11; A fourth adder that subtracts a pulse compression signal that has passed through a reference cell on the most opposite side of the reference cell group 15 on the downstream side of the shift register 10 from the added value of the third adder 23 with respect to the target cell 11. 2 Has the door, the pulse compression signal sum is the addition value of the fourth adder 24, and outputs and stores the sum value of the sum register 25. Note that a cell 16 for storing the pulse compression signal that has passed through the reference cell that is the most opposite to the one direction of the reference cell group 15 may be added.

  In FIG. 6, the sum of the reference cells is stored in the sum register 25 at any time, the value entering the reference cell is added in synchronization with the sampling clock, and the value going out from the reference cell is subtracted. The sum register 25 is updated. As an initial state when the radar apparatus is turned on, if all the cells 11 to 15 of the shift register 10 and the sum register 25 are initialized to zero, the sum is obtained if there are four adders and one register. Calculation can be realized.

  The range side lobe removal means (range side lobe removal circuit) described above is a technique implemented as signal processing of the pulse compression radar apparatus. The pulse compression radar apparatus of the present invention transmits a pulse having a longer pulse width and frequency modulation than a general pulse radar apparatus, and obtains a correlation between a received signal and a reference signal based on the transmitted signal, thereby reducing transmission power. However, this radar apparatus obtains detection performance equivalent to a high-power pulse radar apparatus. FIG. 7 is a block diagram of a pulse compression radar apparatus incorporating the side lobe removal means of the present invention.

  In FIG. 7, the transmission signal is generated by the signal generator 101. If the signal generator 101 uses a digital synthesizer, the phase can be freely controlled as well as a simple frequency modulation signal. The generated signal is mixed with the oscillation frequency of the local oscillator 103 by the frequency mixer 102 and converted to a high frequency. The frequency-converted high frequency signal is amplified by the power amplifier 104, passes through the circulator 105, and is transmitted from the antenna 106. The transmitted signal is reflected by the target and received by the antenna 106. The received signal passes through the circulator 105, is received by the low noise amplifier 107, is further mixed with the oscillation frequency of the local oscillator 103 by the frequency mixer 108, and is converted into a fundamental frequency band. The frequency-converted received signal is sampled by the AD converter 109 and digital signal processed by the quadrature detector 110 and thereafter.

  First, the quadrature detector 110 separates the received signal into two signals that are 90 degrees out of phase with each other. In the subsequent processing, the two separated signals are treated as one complex signal in which one signal is a real part of a complex number and the other is an imaginary part of the complex number. Of these two, whichever part may be the real part, the part where the phase is advanced is often the real part. In FIG. 7, the complex signal is represented by a double arrowhead arrow. The complex signal subjected to quadrature detection is subjected to pulse compression by the pulse compression circuit 111. The compression coefficient used at that time is a transmission signal generated by the signal generator 101 or a coefficient generated by the compression coefficient generator 112 based on the transmission signal. It is. Further, the pulse compression in the pulse compression circuit 111 may be a product-sum operation on the time axis, or may be a realization method by a term-specific product of Fourier transform on the frequency axis. The result of pulse compression is converted into a reception amplitude corresponding to each range by calculating the square root of the square sum of the real part and the imaginary part by the absolute value conversion circuit 113. Since this reception amplitude has the range side lobe shown in FIG. 1, it is input to the range side lobe removal circuit 100 of the present invention as described above. The signal from which the range side lobe has been removed is logarithmically converted by the logarithmic converter 114, and the result is converted to an analog signal by the DA converter 115 and transmitted to the radar indicator.

  FIG. 8 shows the result [amplitude and subtraction amount after pulse compression] of the received signal when the sea is observed from the ship anchored at the port with the pulse compression radar apparatus of the present invention. The radar specifications of this pulse compression radar are: transmission pulse width: 4.8 microseconds, chirp frequency shift width: 16 MHz, sampling frequency: 40 MHz.

  Looking at the actual radar screen, if the range side lobe removal of the present invention is not performed, the range side lobe is reflected before and after the ship, and the range side lobe also appears before and after the breakwater. Appears and the video appears to blur.

On the other hand, when the range side lobe removal of the present invention is performed, the range side lobe that exists before and after the ship disappears, the range side lobe that exists before and after the breakwater also disappears, and its outline can be clearly confirmed. became. Regarding this processing, the number of guard cells Ng = 16, the number of reference cells Nr = 392, and the coefficient for calculating the subtraction amount was 0.77 × 10 ⁻³ (= 0.3 / Nr).

  FIG. 8A is a diagram showing an example of amplitude when the direction of the breakwater and the ship is seen among the results of signal processing of the received signal, and FIG. 8B is a case where the direction of the target on land is seen. An amplitude example is shown.

  8 (a) and 8 (b), the solid line represents the amplitude by pulse compression (that is, the amplitude when the present invention is not implemented), and the broken line represents the amplitude subtraction amount calculated by the present invention. In the figure, the horizontal axis represents the range, and the vertical axis represents the amplitude expressed in a logarithmic scale.

  First, in FIG. 8A, the peak in the range 730 is a breakwater, and the other three peaks are ships. These peaks are accompanied by a range side lobe 35 dB to 40 dB lower than that. On the other hand, the calculated amplitude subtraction amount is larger than the range side lobe, and in the range where the target exists, the subtraction amount decreases, and the amount by which the target amplitude is reduced is suppressed. . When the side lobe range removal processing of the present invention is performed, a signal smaller than the subtraction amount becomes zero.

  FIG. 8B shows the amplitude of a land target. Due to the nature of the algorithm, the amount of subtraction increases in the vicinity of the prominent peak, so there is a feeling that it is subtracting a little, but in other places the subtraction amount does not increase so much, so the land video is It will not be erased significantly.

  In the present invention, the amplitude of the range time sidelobe generated when the received signal having a large reflected power is pulse-compressed can be removed while predicting. As a result, blurring of a large ship or a short-distance coastline can be eliminated, and a radar device image with a clear outline can be obtained.

  If the range side lobe is essentially suppressed, means for controlling the amplitude of the transmission waveform is effective. However, the present invention corrects the range side lobe without using a circuit for controlling the amplitude of the transmission signal. A clear radar device image can be obtained.

  Even with a pulse-compressed radar device with amplitude control, if the target amplitude after pulse compression is much larger than the noise (60 dB or more), the same problem occurs because the range side lobe cannot be suppressed. Even in such a case, a clear radar apparatus image can be obtained by supplementarily using the present invention.

Diagram explaining the concept of range sidelobe removal Diagram explaining the range of the processing window that affects the target signal Sidelobe removal flowchart Example of amplitude data array for sidelobe removal The figure which shows the structure of the range side lobe removal circuit using a shift register The figure which shows the other structure of the range side lobe removal circuit using a shift register. The figure which shows the structure of the pulse compression radar apparatus of this invention The figure which shows the result of having processed the received signal when observing the sea from the ship

Explanation of symbols

100 Range Sidelobe Removal Circuit 10 Shift Register 11 Target Cell 12, 13 Guard Cell 14, 15 Reference Cell 20 Sum Operation Unit 21-24 Adder 25 Sum Register 30 Multiplying Unit 40 Subtracting Unit 50 Selective Output Unit

Claims (4)

A modulated pulsed transmission signal is transmitted to the outside, the reflected signal reflected from the outside is received as a reception signal, and the reference signal based on the transmission signal is correlated with the reception signal to perform pulse compression. In a pulse compression radar apparatus that obtains an amplitude signal (hereinafter referred to as a pulse compression signal),
A range side that reduces the range side lobe by predicting the amplitude of the range side lobe that appears before and after the target signal in the range direction based on the pulse compression signal and subtracting the predicted amplitude of the range side lobe from the pulse compression signal. A pulse compression radar apparatus comprising lobe removal means. The range side lobe removing means includes
A shift register having one target cell in the center, a first predetermined number of guard cell groups on each side of the target cell, and a second predetermined number of reference cell groups on the opposite side of the guard cell group to the target cell; ,
An input / shift means for inputting a pulse compression signal at an input timing synchronized with a sampling clock from one direction to the shift register, and shifting the input pulse compression signal from the upstream side to the downstream side in the shift register;
A sum calculating means for calculating a sum of pulse compression signals existing in each cell of the reference cell group in synchronization with each input timing;
Multiplication means for multiplying the sum of pulse compression signals of the sum calculation means by a preset coefficient to obtain a predicted sidelobe amplitude;
2. Subtracting means for obtaining a subtraction value by subtracting the predicted sidelobe amplitude of the multiplication means from a pulse compression signal present in the cell of interest in synchronization with the sampling clock. The pulse compression radar device according to 1.   Further, when the subtraction value from the subtraction means is a positive value, the subtraction value is output, and when the subtraction value is a negative value, selection output means for outputting a zero value instead of the subtraction value is provided. The pulse compression radar apparatus according to claim 2. The sum calculating means is:
A first adder that adds the pulse compression signal of the reference cell closest to the one-direction side of the reference cell group upstream of the shift register to the target cell and the sum value stored in the sum register; A second adder for subtracting the pulse compression signal of the guard cell closest to the one-way side of the guard cell group upstream of the shift register from the addition value of one adder, and the addition of the second adder A third adder for adding the value and the pulse compression signal of the reference cell closest to the one-direction side of the reference cell group downstream of the shift register to the target cell, and the addition value of the third adder A fourth adder for subtracting a pulse compression signal that has passed through a reference cell that is most opposite to the one direction of the reference cell group on the downstream side of the shift register from the target cell;
The pulse compression radar apparatus according to claim 2, wherein a pulse compression signal sum which is an addition value of the fourth adder is output and stored as a sum value in the sum register.

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