JPH11142508A - Signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a signal processor of large range-side-lobe suppression effect, using a simple pulse compressor. SOLUTION: A reception signal pulse-compressed at a pulse compressor 10 is outputted to a range-side-lobe suppressor 11, and at an auxiliary reception signal generator 104, multiplied by a multiplier Y which is set by a multiplier factor setting device 103 in advance. At a shift processor 105, the reception signal after the pulse-compression under goes a shift process. The outputs of the shift processor 105 are added together at an adder 106, which is subtracted from the output of the reception signal generator 104 with a subtractor 107, which is taken as the output of the range-side-lobe suppressor 11. The output of the range-side-lobe suppressor 11 is inputted in an amplitude correction device 12, and multiplied by a correction factor W obtained from the attenuation amount of a min lobe in the process with the side-lobe-suppressor 11 at an amplitude value generator 109, for output correction of the range-side-lobe suppressor 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar apparatus and, more particularly, to a signal processing apparatus which performs a correlation process between a reflected reception signal and a reference signal generated based on the transmission signal using a modulated transmission signal. .

[0002]

2. Description of the Related Art In a radar apparatus, there is a pulse compression method as a technique for satisfying both conflicting increases in detection distance and improvement in distance resolution, and a linear frequency modulation method is used in the pulse compression method. And a code modulation method. FIG. 9 is a block diagram showing a conventional pulse compression type radar device using a code modulation method.

[0003] In FIG. 9, a Barker code sequence generated by an encoding pulse modulator 3a is input to a transmitter 4a and a pulse compressor 10a. In the transmitter 4a, the phase of the transmission signal is inverted according to the input code sequence,
The signal is non-inverted, and transmitted from the antenna 1a to the space via the circulator 2a in synchronization with the signal from the COHO oscillator 5a. The signal reflected from the object is received by the antenna 1a and input to the high-frequency amplifier 6a via the circulator 2a. The received signal input to the high-frequency amplifier 6a is amplified here, and phase-detected by the phase detector 7a in synchronization with the signal of the COHO oscillator 5a.

The signals (I and Q signals) subjected to phase detection are input to a signal processing device 18a. The signal input to the signal processing device 18a is converted into a digital signal by the A / D converter 8a, and the Doppler shift of the received signal is corrected by the Doppler corrector 9a. Is entered. The pulse compressor 10a performs coded pulse compression in accordance with the Barker code sequence generated in the coded pulse modulator 3a.

[0005] The received signal after the pulse compression is MTI (Movi).
ng Target Indicator) 13a, MDF (Multi Doppler)
Filter) 14a, LOG / CFAR (Log / Constant Fa)
Unnecessary signals, such as clutter, are removed at an (lseAlarm Rate) 15a, and further, a signal correlation process and the like are performed at a data processor 16a, and input to a display 17a.

[0006]

By the way, in the received signal after the pulse compression, unnecessary range side lobes occur before and after the peak pulse as shown in FIG. 4C or FIG. The reduction of the unnecessary range side lobe has been studied in the past, and as an example of the code modulation method, a journal of the Institute of Electronics, Information and Communication Engineers (B-II Vol.
J80-B-II No. 8 pp. 722-729), "New polyphase pulse compression code sequence and its characteristics" (hereinafter referred to as cited document).

In the technique described in this cited document, the degree of range sidelobe suppression (the ratio of the peak sidelobe to the main peak) is not always sufficient as compared with conventional code sequences such as Barker sequences and Frank sequences. For example, while the side lobe suppression degree of the Barker sequence is 22.2 dB, the side lobe suppression degree of the code sequence shown in the cited document is about -26 dB.

That is, in order to detect a signal having a very small received signal level, it is necessary to further reduce the side lobe, and even the one described in the cited document is not sufficient as the range side lobe suppression degree. . Further, in the technique described in the cited document, since the phase change of the modulated signal is suppressed by making the phase polyphase, various types of phase shifters are required, and the configuration of the pulse compression circuit becomes complicated. There is.

It is an object of the present invention that the phase change of the modulated signal is 2
An object of the present invention is to provide a signal processing device capable of sufficiently suppressing range side lobes by using a Barker code sequence as a value and providing a simple processor such as a shift processor and an adder.

[0010]

SUMMARY OF THE INVENTION A signal processing apparatus according to the present invention includes a range side lobe suppressing means for suppressing a range side lobe of a received signal after pulse compression processing, and an amplitude correcting means. By performing shift processing and addition processing on a signal after pulse compression processing by a code modulation method for a plurality of reception signals received by a sensor such as a radar, and subtracting this processing result from the original reception signal, a range side lobe is obtained. It is characterized by suppression.

More specifically, a multiplier setting means for setting an optimum multiplier obtained in advance by simulation or the like to the result of the pulse compression processing, an auxiliary reception signal generating means for multiplying the multiplier, and a signal for the signal after the pulse compression. Shift processing means for shifting to a position where a range side lobe is generated, addition processing means for adding the signal group subjected to the shift processing, and subtraction of the signal after the addition processing from the signal after the generation of the auxiliary reception signal Subtraction processing means, a correction coefficient setting means for setting a previously obtained correction coefficient, and an amplitude value reproduction means for correcting the level of the main lobe attenuated by the subtraction processing means from the correction coefficient.

These series of means realize processing corresponding to suppressing the range side lobe by making the phase change of the modulation signal multi-phase. Also, since the result of shifting the received signal by the optimum multiplier to the range direction for all range sidelobes generated in the original received signal is subtracted, the range sidelobe is subtracted. Can be sufficiently reduced.

[0013]

FIG. 1 is a block diagram of a radar including a signal processing device according to an embodiment of the present invention. FIG. 2 is a pulse compressor which is a component of the signal processing device of the present invention. FIG. 3 is a diagram showing a specific configuration of a range side lobe suppressor and an amplitude corrector.

According to the present invention, a range side lobe suppressor 11 for inputting a received signal subjected to A / D conversion, Doppler correction and coded pulse compression to suppress a range side lobe, and an output of the range side lobe suppressor 11 are input. And an amplitude corrector 12 for correcting the amount of attenuation of the main lobe level.

The operation of the present invention will be described with reference to FIGS. The Barker code sequence generated in the coded pulse modulator 3 is input to a transmitter 4 and a pulse compressor 10. The transmitter 4 performs phase inversion and non-inversion of the transmission signal according to the input code sequence,
The signal is transmitted from the antenna 1 to the space via the circulator 2 in synchronization with the signal from the transmitter 5. The reflected signal from the object is
The signal is received by the antenna 1 and input to the high-frequency amplifier 6 via the circulator 2. The received signal input to the high-frequency amplifier 6 is amplified here, and phase-detected by the phase detector 7 in synchronization with the signal of the COHO oscillator 5.

The phase-detected signals (I and Q signals) are input to a signal processing device 18. The signal input to the signal processing device 18 is converted into a digital signal by the A / D converter 8, the Doppler shifter 9 corrects the Doppler shift of the received signal, and then converts the digital signal to the pulse compressor 10. Is entered. The pulse compressor 10 performs coded pulse compression according to the Barker code sequence generated in the coded pulse modulator 3.

The received signal after the pulse compression is input to the range side lobe suppressor 11, where the range side lobe is suppressed. Further, the main lobe level attenuated by the suppression is corrected by the amplitude corrector 12.
The corrected output signals are MTI13, MDF14, LO
Unnecessary signals such as clutter are removed in the G / CFAR 15, and further, correlation processing and the like of the signals are performed in the data processor 16 and input to the display 17.

Next, the operation of the range side lobe suppressor 11 and the amplitude corrector 12 will be described with reference to FIG. In the pulse compressor 10, the coded pulse modulator 3
Are shifted by the shift processor 101 and correlation processing is performed with the received signal. Further, the adder 102
The result of the correlation processing is added to perform pulse compression processing. The received signal after the pulse compression is output to the range sidelobe suppressor 11, and the multiplier (Y) set in advance by the multiplier setting unit 103 by a simulation or the like in the auxiliary received signal generator 104 is used as the received signal after the pulse compression. Multiply.

The shift processor 105 performs a shift process on the received signal after the pulse compression. Since the range side lobe caused by the property of the autocorrelation function of the Barker code sequence is 0 or ± 1, it is shifted to the position where the range side lobe is ± 1. That is, the shift amounts are ± 2, ± 4, ± 6, ± 8. Here, since the maximum length of the currently discovered Barker code sequence is 13, the maximum shift amount is ± 12.
A signal group output from the shift processor 105 is added to an adder 106.
Add in.

Next, the signal of the output of the adder 106 is subtracted from the signal of the output of the auxiliary reception signal generator 104 by the subtracter 107 to obtain the output of the range sidelobe suppressor 11.

The output signal of the range side lobe suppressor 11 is input to an amplitude corrector 12. Here, the level of the main lobe attenuated by the range side lobe suppression is corrected. That is, in the amplitude value regenerator 109, a correction coefficient (W) is set by the correction coefficient setting unit 108 based on the amount of attenuation of the main lobe in the processing of the side lobe suppressor 11, and the range side lobe is multiplied by the received signal. The signal of the suppressor 11 is corrected.

[0022]

Next, an embodiment of the present invention when a Barker code sequence having a code length of 13 is employed will be described with reference to FIGS. FIG. 3A shows a transmission signal, in which a transmission pulse width is divided into 13 equal parts in time, and 13 symbols (+,-) are associated with each, and the phase of the carrier of the transmission pulse is 0, π, respectively. The transmission pulse is coded and phase-modulated by shifting. FIG. 3B shows a received signal obtained by reproducing the code sequence signal.

When this received signal is input to the pulse compression circuit of FIG. 4A, the pulse compression circuit of FIG.
As shown in FIG. 4C, a shift process and an addition process as shown in FIG. 4B are performed. Becomes The degree of side lobe suppression at this time is 2 as shown in the autocorrelation function of the Barker code sequence (N ′ = 13) in FIG.
2.2 dB. The autocorrelation function is given by the following equation (1).

[0024]

(Equation 1) Since the nature of the code sequence used for the coded pulse modulation depends on the nature of the autocorrelation of the coded sequence, the range sidelobe suppression degree is compared using the autocorrelation function.

FIG. 5 shows the principle of the range sidelobe suppressor 11. A in FIG. 5 is a code string obtained by multiplying the output signal of the pulse compressor by a multiplier (Y). The multiplier (Y) is calculated in advance by simulation from the relationship between the range side lobe suppression degree and the amount of attenuation of the main lobe level due to suppression. Here, Y = 24. The code string B is obtained by shifting the code string A by −12 in order to suppress the range side lobe a of the code string A. Hereinafter, similarly, the code strings C to M are similarly shifted in order to suppress the range side lobes b to l of the code string A.

The code sequence N is the result of adding the code sequences B to M. Therefore, a code string O is obtained by subtracting the code string N from the code string A. FIG. 7 shows an autocorrelation function of the code string P obtained by dividing the code string O by 24. The range side lobe suppression degree is 33.9 dB, which is 1 to the range side lobe suppression degree 22.2 dB of the code sequence of the barker 13.
It is improved by 1.7 dB.

In FIG. 6, the level of the main lobe is 13, whereas in FIG. 7, it is 12.5, which is attenuated by 0.5. Therefore, a correction coefficient (W) is obtained so that the average amplitude value of the following equation (2) becomes 1, and the obtained coefficient is multiplied by the attenuated main lobe level to perform amplitude correction.

Average amplitude value = (addition value / number of added signals) × W (2) In this embodiment, since the addition value is 12.5 and the number of added signals is 13, the correction coefficient (W) is 1 .04. Therefore, the range side lobe suppression degree after the correction processing is 34.3 dB. FIG. 8 shows the autocorrelation function after the amplitude correction.

As a method of setting the correction coefficient, in the embodiment, the correction coefficient is sequentially calculated. However, the correction coefficient calculated by simulation from the relationship between the range side lobe suppression degree and the attenuation of the main lobe level is used as a data. There is also a method of reading a database and then reading an appropriate correction coefficient from the database.

From the above, comparing the range side lobe suppression degree, the side lobe suppression degree of the embodiment according to the present invention is 3
4.3 dB is 12.1 dB from 22.2 dB of the range side lobe suppression degree of the code sequence of the barker 13, and 26 dB is the range side lobe suppression degree of the code sequence described in the cited reference.
Is improved by 8.3 dB.

[0031]

According to the present invention, the Barker sequence is used as it is as the code sequence without performing the phase change of the phase change of the modulation signal, and the range sidelobe can be easily processed by the shift process and the addition process. The suppression can be improved.

[0032]

[Brief description of the drawings]

FIG. 1 is a block diagram of a radar device including a signal processing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a signal processing device according to an embodiment of the present invention.

FIG. 3 is a diagram showing a transmission signal and a reception signal of an encoded pulse.

FIG. 4 is a diagram for explaining an operation of the pulse compression circuit.

FIG. 5 is a diagram for explaining an embodiment of the present invention.

FIG. 6 is a diagram for explaining an embodiment of the present invention.

FIG. 7 is a diagram for explaining an embodiment of the present invention.

FIG. 8 is a diagram for explaining an embodiment of the present invention.

FIG. 9 is a block diagram of a radar device including a signal processing device according to a conventional example.

[Explanation of symbols]

 1, 1a Antenna 2, 2a Circulator 3, 3a Coded modulator 4, 4a Transmitter 5, 5a COHO oscillator 6, 6a High frequency amplifier 7, 7a Phase detector 8, 8a A / D converter 9, 9a Doppler correction Device 10, 10a Pulse compressor 11 Range sidelobe suppressor 12 Amplitude corrector 13, 13a MTI 14, 14a MDF 15, 15a LOG / CFAR 16, 16a Data processor 17, 17a Display 18, 18, a Signal processor 101 shift Processor 102 Addition processor 103 Multiplier setter 104 Auxiliary reception signal generator 105 Shift processor 106 Adder 107 Subtractor 108 Correction coefficient setter 109 Amplitude regenerator

Claims (5)

[Claims] 1. A radar apparatus for performing pulse compression by binary-modulating a transmission pulse with a code sequence, comprising a range sidelobe suppressor for receiving a pulse-compressed reception signal and suppressing the range sidelobe. A signal processing device characterized by the above-mentioned. 2. A radar apparatus for performing pulse compression by binary-modulating a transmission pulse by a code sequence, comprising: a range side lobe suppressor that receives a pulse-compressed reception signal and suppresses a range side lobe thereof; A signal processing apparatus, comprising: an amplitude corrector that receives an output of the range side lobe suppressor and corrects an amplitude of a main lobe level attenuated by the range side lobe suppression process. 3. The range side lobe suppressor includes a multiplier setter for setting a multiplier determined in advance from a relationship between a range side lobe suppression degree and a main lobe attenuation, and an auxiliary reception signal generator for multiplying the multiplier. A shift processor that shifts the pulse-compressed signal in the range direction, an adder that adds the shifted result, and subtracts an output signal of the adder from an output signal of the auxiliary reception signal generator. 3. The signal processing device according to claim 1, wherein the signal processing device comprises a subtractor. 4. The side lobe suppressor according to claim 1, wherein the amplitude corrector is configured to multiply the output signal of the range side lobe suppressor by a correction coefficient setter for setting a correction coefficient obtained in advance, and the correction coefficient. 3. The signal processing apparatus according to claim 2, further comprising an amplitude value regenerator that corrects an amount of attenuation of the main lobe level attenuated by the processing. 5. The signal according to claim 1, wherein an encoded phase modulation pulse in which the phase of a carrier is shifted by 0 and π by a Barker code sequence, respectively, is used as the transmission pulse. Processing equipment.