CN106950545B - Dual-frequency transmitting mode and clutter suppression method based on dual-frequency real-time processing - Google Patents

Dual-frequency transmitting mode and clutter suppression method based on dual-frequency real-time processing Download PDF

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Publication number
CN106950545B
CN106950545B CN201710096532.3A CN201710096532A CN106950545B CN 106950545 B CN106950545 B CN 106950545B CN 201710096532 A CN201710096532 A CN 201710096532A CN 106950545 B CN106950545 B CN 106950545B
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China
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frequency
pulse
signal
short
zero
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CN201710096532.3A
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Chinese (zh)
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CN106950545A (en
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黄志华
史光曜
徐晓
孙玉玺
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武汉滨湖电子有限责任公司
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28Details of pulse systems
    • G01S7/282Transmitters
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/36Means for anti-jamming, e.g. electronic counter-counter measures [ECCM]

Abstract

The invention relates to the field of radar overall design and signal processing, in particular to a double-frequency transmitting mode and a clutter suppression method based on double-frequency real-time processing. The invention increases the number of short-distance pulse echoes, improves clutter suppression capability and solves the problem of contradiction between clutter suppression and time resources in the beam residence time through an effective transmitting mode and a corresponding processing method in the limited beam residence time.

Description

Dual-frequency transmitting mode and clutter suppression method based on dual-frequency real-time processing

Technical Field

The invention relates to a double-frequency transmitting mode and a clutter suppression method based on double-frequency real-time processing in the field of radar overall design and signal processing, in particular to a method for improving clutter suppression capability, which can be widely applied to system design of a pulse radar.

Background

The clutter environment is caused by a large number of scattering elements (such as terrain, ground objects and sea waves) distributed on the earth surface or scattering elements (such as weather reflection and metal foil strips) distributed in a certain space volume, and if no effective measures are taken, the low-altitude detection performance of the ground radar is seriously influenced. The clutter suppression capability refers to the suppression capability of the radar on interference clutter from the ground, sea surface, air and other areas in the detection process, and is an important index for evaluating the performance of the modern radar. When the radar detects low-altitude targets, the ground radar generally suppresses clutter through Doppler filtering measures such as MTD/PD and the like for the ground clutter interference signals.

The suppression effect obtained by using the doppler filtering such as MTD/PD is closely related to the pulse accumulation time, and the longer the accumulation time is, the higher the frequency resolution corresponding to the larger the number of pulses is, and the better the corresponding suppression effect is, but since the radar is to perform the omnidirectional scanning, the beam dwell time in each direction is fixed. In order to have the whole-course detection of long distance and short distance, the working mode of long pulse long distance detection and short pulse short distance detection is usually adopted, and within the beam residence time, the traditional working time sequence generally has two types, namely, the long distance and the short distance alternately emit waveforms with different pulse widths and the same repetition period, and at the moment, the short distance and the long distance have the same pulse number and the maximum accumulation time, and the clutter suppression abilities of the two types are the same; secondly, waveforms with different pulse widths and different repetition periods are independently transmitted in a long distance and a short distance, the number of pulses in the long distance or the short distance can be adjusted according to requirements, the pulse numbers and the corresponding accumulation time of the two in the beam dwell time can be different, and when more time is allocated for generating more pulses in the short distance so as to improve the clutter suppression capability in the short distance, the corresponding accumulation time in the long distance is reduced, so that the radar detection power is reduced.

In the conventional working sequence, the wave beam residence time limits the improvement of the clutter suppression capability, but the wave beam residence time is relatively fixed due to the limitation of basic indexes such as the antenna rotating speed, the wave beam width and the like, and at the moment, the problem of contradiction between clutter suppression and time resources exists.

Disclosure of Invention

The invention provides a double-frequency transmitting mode and a clutter suppression method based on double-frequency real-time processing aiming at the contradiction in the traditional mode. The invention obtains the best accumulation time and pulse number and improves the clutter suppression capability through an effective transmitting mode and a corresponding processing method in the limited beam residence time.

The technical scheme of the invention is as follows: a dual frequency transmission method, characterized by: the long pulse is firstly transmitted, the first short pulse is immediately transmitted after the transmission is finished, the second short pulse is transmitted after the interval of the initial transmission time of the first short pulse is fixed, and then the waveform transmission in the above transmission period is repeated.

The dual frequency transmission method as described above, characterized in that: the first short pulse emission and the second short pulse emission are separated by half of the emission period.

The invention also discloses a clutter suppression method based on double-frequency real-time processing, which is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps of firstly, generating a dual-frequency transmitting waveform, wherein the dual-frequency transmitting waveform generating method comprises the following steps: the method comprises the steps that a long pulse and two short pulses are included in a transmission period, the time width of the long pulse is more than 10 times of the time width of the short pulses, the center frequency of the long pulse is different from the center frequency of the short pulses, the long pulse is transmitted firstly, the first short pulse is transmitted immediately after the transmission is finished, the second short pulse is transmitted after the interval of the transmission starting time of the first short pulse is fixed, and then the waveform transmission in the transmission period is repeated;

step two, the step of receiving and processing the double-frequency signal specifically comprises the following steps:

a. the radar radio frequency echo signal is subjected to analog down-conversion processing to obtain a broadband analog signal with zero center carrier frequency;

b. after A/D conversion, the broadband analog signal is converted into two paths of digital signals, wherein the passing frequency of one path of digital signal is if1The local oscillation signal is subjected to digital frequency mixing, the center frequency of the long pulse signal is shifted to zero frequency to obtain a long pulse zero intermediate frequency preprocessing signal, and the passing frequency of the other path of digital signal is-if2Carrying out digital frequency mixing on the local oscillation signal, shifting the center frequency of the short pulse signal to zero frequency, and obtaining a short pulse zero intermediate frequency preprocessing signal;

c. setting a low-pass filter with a low-pass bandwidth consistent with the signal bandwidth, performing low-pass filtering processing on the long-pulse zero intermediate frequency preprocessing signal, and filtering out-of-band frequency components to obtain a corresponding long-pulse zero intermediate frequency signal; carrying out low-pass filtering processing on the short-pulse zero intermediate frequency preprocessing signal, and after filtering out-of-band frequency components, obtaining a corresponding short-pulse zero intermediate frequency signal; therein if1And if2Respectively the offset frequency quantity of the long pulse and the short pulse relative to the center frequency of the current working frequency point;

and step three, clutter suppression.

The clutter suppression method based on the dual-frequency real-time processing is characterized in that: the first short pulse emission and the second short pulse emission are separated by half of the emission period.

The invention has the beneficial effects that: in the beam residence time, the number of short-distance pulse echoes is increased, the clutter suppression capability is improved, and the problem of contradiction between clutter suppression and time resources is solved; the long pulse and the short pulse use different carrier frequencies, so that echoes of the short pulse can be received simultaneously in a long pulse receiving interval, and crosstalk is not generated between the long pulse and the short pulse; the number of short pulse transmitting pulses is more than that of long pulses covered by the same azimuth wave position, the number of echo pulses in a short-distance clutter area is increased, the Doppler resolution of short-distance clutter is improved, and the short-distance clutter suppression capability is improved in limited beam residence time.

Drawings

FIG. 1 is a timing diagram of operation;

fig. 2 is a schematic diagram of a dual-band receiving process.

Detailed Description

The noun explains:

MTD: and detecting a moving target.

PD: pulse doppler.

The invention is further described below with reference to the accompanying drawings and specific embodiments.

The double-frequency transmitting method of the present invention includes one long pulse and two short pulses in one transmitting period, the long pulse has time width preferably over 10 times greater than that of the short pulses, the center frequency of the long pulse is different from that of the short pulses, and the long pulse is first transmitted and the first short pulse is then transmitted after the transmission is completed.

In the present invention, the first short pulse transmission and the second short pulse transmission are preferably separated by a half transmission period. Therefore, in a receiving period, the first echo comprises echoes with two frequencies of a long pulse center frequency and a short pulse center frequency, the second echo only comprises a short pulse center frequency echo, any two short pulse center frequencies are separated by a half frequency period, the design of a signal processing and transmitting and receiving system is convenient, double pulse echo quantity is provided, under the condition of meeting the full-distance and full-airspace coverage, the quantity of usable echoes is more, higher visibility of targets in ground clutter can be realized, and the low-altitude detection performance is improved.

The clutter suppression method based on the double-frequency real-time processing comprises the following steps:

step one, generating a dual-frequency transmitting waveform:

generating a dual-frequency transmit waveform suitable for long pulse duration wt as shown in FIG. 11Much greater than the short pulse time width wt2The pulse compression radar of (1) preferably has a long pulse time width of 10 times or more as long as a short pulse time width, for example, the long pulse width is wt1600us, short pulse width wt220 us. First, a transmission center frequency of f1Pulse width of wt1Immediately after the end of the transmission of the long pulse, the transmission center frequency of the long pulse of (2) is f2Pulse width of wt2While waiting for a first short pulse transmission start time Tr2After a time, a second short pulse is sent, after the second short pulse is received, the current repetition period is ended, and then the time Tr of the long pulse transmission starting moment is waited for1After the time, the long and short pulses are repeatedly transmitted according to the above-mentioned period.

With the above timing, one repetition period Tr of the long pulse1The repetition period of the short pulse is Tr2And the repetition period of the short pulse is one half of that of the long pulse, so that in the radar system, the short pulse responsible for detecting the short distance has double pulse echo number relative to the long pulse responsible for detecting the long distance, and under the condition of meeting the full-distance and full-airspace coverage, the number of usable echoes is more, the target visibility in higher ground clutter can be realized, and the low-altitude detection performance is improved.

On the premise of ensuring the close range power coverage of the receiving echo region corresponding to each short pulse, three or more short pulses can be emitted in one period, so that the clutter suppression capability is further improved.

Step two, double-frequency signal receiving and processing

In the case of dual-frequency operation, the signal receiving process flow chart is shown in fig. 2. The treatment process is as follows:

1. radar radio frequency echo signal SRFIn the method, a radio frequency echo signal simultaneously comprising a long pulse and a short pulse, and a central frequency f corresponding to the long pulse echo signal1=f0-if1The center frequency corresponding to the short pulse echo signal is f2=f0+if2Wherein if1And if2Is long or short pulse relative to the center frequency f of the current working frequency point0The amount of offset frequency of (a).

2. Radar radio frequency echo signal SRFObtaining a broadband analog signal S with zero center carrier frequency after analog down-conversion processingIFThe intermediate frequency information of long and short pulses is included;

3. broadband analog signal SIFAfter A/D conversion, the signal is converted into a digital signal S12Then, in one aspect, S12A passing frequency if1The local oscillator signal is subjected to digital frequency mixing, the center frequency of the long pulse signal is shifted to zero frequency, and a long pulse zero intermediate frequency preprocessing signal S is obtained10The signal comprises a long-pulse zero intermediate frequency signal and has a center frequency if1+if2Of the short pulse signal, on the other hand, S12A passing frequency of-if2The local oscillator signal is subjected to digital frequency mixing, the center frequency of the short pulse signal is shifted to zero frequency, and a short pulse zero intermediate frequency preprocessing signal S is obtained20The signal comprises a short pulse zero intermediate frequency signal and has a center frequency of- (if)1+if2) The long pulse signal of (3); unlike the conventional signal processing method, in this step, the long pulse zero intermediate frequency signal and the short pulse zero intermediate frequency signal are extracted twice.

4. Setting a low-pass filter with the low-pass bandwidth consistent with the signal bandwidth to pre-process the signal S with long pulse and zero intermediate frequency10Low-pass filtering to obtain zero-IF signal S of corresponding long pulse1While, at the same time, the signal S is preprocessed in the form of short pulses at zero intermediate frequency20Low-pass filtering to obtain zero-IF signal S of corresponding short pulse after filtering out-of-band frequency component2

Step three, clutter suppression

The clutter suppression process uses MTD/PD to process due to the short pulse S2The number of pulse echoes of (2) is a long pulse S1The number of pulse echoes is 2 times, and clutter suppression capacity corresponding to short pulses is improved in the subsequent clutter suppression processing processes of MTD/PD and the like.

Claims (1)

1. A clutter suppression method based on double-frequency real-time processing is characterized in that: the method comprises the following steps:
the method comprises the following steps of firstly, generating a dual-frequency transmitting waveform, wherein the dual-frequency transmitting waveform generating method comprises the following steps: the method comprises the steps that a long pulse and two short pulses are included in a transmission period, the time width of the long pulse is more than 10 times of that of the short pulses, the center frequency of the long pulse is different from that of the short pulses, the long pulse is transmitted firstly, the first short pulse is transmitted immediately after the transmission is finished, the second short pulse is transmitted after the interval of the transmission starting time of the first short pulse is fixed, and then waveform transmission in the transmission period is repeated;
step two, the step of receiving and processing the double-frequency signal specifically comprises the following steps:
a. the radar radio frequency echo signal is subjected to analog down-conversion processing to obtain a broadband analog signal with zero center carrier frequency;
b. after A/D conversion, the broadband analog signal is converted into two paths of digital signals, wherein the passing frequency of one path of digital signal is if1The local oscillation signal is subjected to digital frequency mixing, the center frequency of the long pulse signal is shifted to zero frequency to obtain a long pulse zero intermediate frequency preprocessing signal, and the passing frequency of the other path of digital signal is-if2The local oscillator signals are subjected to digital frequency mixing, the center frequency of the short pulse signals is shifted to zero frequency,obtaining a short-pulse zero intermediate frequency preprocessing signal;
c. setting a low-pass filter with a low-pass bandwidth consistent with the signal bandwidth, performing low-pass filtering processing on the long-pulse zero intermediate frequency preprocessing signal, and filtering out-of-band frequency components to obtain a corresponding long-pulse zero intermediate frequency signal; carrying out low-pass filtering processing on the short-pulse zero intermediate frequency preprocessing signal, and after filtering out-of-band frequency components, obtaining a corresponding short-pulse zero intermediate frequency signal; therein if1And if2Respectively the offset frequency quantity of the long pulse and the short pulse relative to the center frequency of the current working frequency point;
step three, clutter suppression; the clutter suppression process uses MTD/PD to process, the first short pulse emission and the second short pulse emission are separated by half of the emission period, and the repetition period of the short pulse is half of that of the long pulse.
CN201710096532.3A 2017-02-22 2017-02-22 Dual-frequency transmitting mode and clutter suppression method based on dual-frequency real-time processing CN106950545B (en)

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CN1157657A (en) * 1994-09-06 1997-08-20 加利福尼亚大学董事会 Range-gated field disturbance sensor with range-sensitivity compensation
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