CN106814356A - It is a kind of based on Radar Signal Processing System apart from tracing subsystem - Google Patents
It is a kind of based on Radar Signal Processing System apart from tracing subsystem Download PDFInfo
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- CN106814356A CN106814356A CN201710054609.0A CN201710054609A CN106814356A CN 106814356 A CN106814356 A CN 106814356A CN 201710054609 A CN201710054609 A CN 201710054609A CN 106814356 A CN106814356 A CN 106814356A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO 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
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/66—Radar-tracking systems; Analogous systems
- G01S13/70—Radar-tracking systems; Analogous systems for range tracking only
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO 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
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
- G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
- G01S13/18—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein range gates are used
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO 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
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
- G01S7/414—Discriminating targets with respect to background clutter
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- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
- Remote Sensing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Radar Systems Or Details Thereof (AREA)
Abstract
The invention discloses it is a kind of based on Radar Signal Processing System apart from tracing subsystem, including range gate gating module, pulse compression module, correlative accumulation MTD modules, CFAR detection module, tracking gate module, distance centering processing module, range finder module, Kalman filtering module/α β filtration modules.The delay that the present invention passes through command range select gate, with channel signal by detecting target after matched filtering, MTD and CFAR detection, then carried out without fuzzy range finding through tracking gate and apart from centering treatment, range gating ripple door is produced through Kalman filtering or α β filtering, center of tracking gate is set to be directed at the echo signal detected by echo, so as to ensure that ripple door movement automatically tracks target, and then cause that whole Radar Signal Processing System realizes the signal processing flow of intermediate-freuqncy signal detection and distance tracking for the intermediate-freuqncy signal that obtains.
Description
Technical field
The present invention relates to it is a kind of based on Radar Signal Processing System apart from tracing subsystem.
Background technology
Radar, is the transliteration of English Radar, comes from the abbreviation of radio detection and ranging, look like for "
Radio detection and ranging ", i.e., find target and determine their locus with the method for radio.Therefore, radar also by
Referred to as " radio position finding radio directional bearing ".Radar is using the electronic equipment of electromagnetic wave detection target.Radar emission electromagnetic wave is carried out to target
Irradiate and receive its echo, be derived from target to the distance of electromagnetic emission point, range rate (radial velocity), orientation,
The information such as height.
Radar signal processor, control transmission channel produce chirp pulse signal through up-conversion, transmit-receive switch and and
Difference comparator after launched by feed antenna, target reflection echo-signal after feed antenna pass through and differ from comparator formed
With, gun parallax, the road signal of trim three, obtain intermediate-freuqncy signal after carrying out down coversion after transmit-receive switch.At whole radar signal
Reason machine needs to carry out the letter of intermediate-freuqncy signal detection, distance tracking, speed tracing and angleonly tracking for the intermediate-freuqncy signal for obtaining
Number handling process.And distance tracking is then as its critically important part.
The content of the invention
It is an object of the invention to overcome the deficiencies in the prior art, there is provided a kind of distance based on Radar Signal Processing System
Tracing subsystem.
The purpose of the present invention is achieved through the following technical solutions：A kind of distance based on Radar Signal Processing System
Tracing subsystem, including range gate gating module, pulse compression module, correlative accumulation MTD modules, CFAR detection module,
Tracking gate module, distance centering processing module, range finder module, Kalman filtering module/alpha-beta filtration module；Outside two-way I/Q
Tracing subsystem is entered by range gate gating module with channel signal, and sequentially passes through pulse compression module, correlative accumulation
Target is detected after MTD modules, CFAR detection module, is then entered after tracking gate module, distance centering processing module
Range finder module carries out, without fuzzy range finding, range gating ripple door being produced through Kalman filtering/alpha-beta filtration module after range finding, makes distance
Echo signal detected by the center of tracking gate alignment echo of ripple door gating module.
Described outside and channel signal is formed by A/D modular converters and Digital Down Converter Module；Described A/D conversions
Module receives outside intermediate frequency echo and signal and A/D samplings is directly carried out to signal in intermediate frequency, and signal sampling formula is as follows：
In formula, f0It is xMHz centre frequencies, B is yMHz bandwidth, and n is natural number；
Described Digital Down Converter Module includes orthogonalization unit, digital controlled oscillator NCO, multiplier, FIR low pass filter
And extracting unit, orthogonalization unit receive the digital medium-frequency signal from A/D modular converters simultaneously be orthogonalized to form orthogonal
I/Q two paths of signals, the orthogonal local oscillation sequence that two paths of signals is formed with digital controlled oscillator NCO respectively is multiplied, and exports respectively to each
The FIR low pass filter on road, low pass filter takes out baseband signal and filters radio-frequency component, and extracting unit is taken out baseband signal
Reduction signal rate is taken, the output end of extracting unit is connected with range gate gating module.
Described pulse compression module is used to realize matched filtering, using Time-Domain Pulse Compression module or frequency-domain impulse pressure
Contracting module；
Described Time-Domain Pulse Compression module includes four FIR matched filters and two adders；Wherein, a FIR
The first input end of matched filter and the 2nd FIR matched filters receives I roads signal, a FIR matched filters and
Second input of two FIR matched filters receives Least square estimation respectively, a FIR matched filters and the 2nd FIR
Exported respectively to the first input of the first input end and second adder of first adder after carrying out convolution algorithm with wave filter
End；The first input end of the 3rd FIR matched filters and the 4th FIR matched filters receives Q roads signal, the 3rd FIR matchings
Second input of wave filter and the 4th FIR matched filters receives Least square estimation respectively, the 3rd FIR matched filters and
4th FIR matched filters export respectively after convolution algorithm to second input and second adder of first adder
Second input；The letter of first adder and second adder after exporting I/Q two-way matched filterings after add operation respectively
Number；
Described frequency-domain impulse compression module include FFT unit, complex multiplication unit, matched filter spectrum unit,
IFFT units, it is S (w) that FFT unit is FFT to the I/Q two ways of digital signals being input into and carry out map function to transform to frequency spectrum respectively
Frequency domain, spectrum H (w) phase of the matched filter that complex multiplication unit exports S (w) with matched filter spectrum unit
Multiply, the achievement for obtaining is carried out the result that IFFT computings obtain pulse compression by IFFT units；Described spectrum H (w) be using
Carry out what FFT was obtained with filter factor.
Also include the range gate reordering module being sequentially connected between pulse compression module and correlative accumulation MTD modules and move
Target shows MTI modules；
Described range gate reordering module uses two-dimentional buffer storage, by radar echo signal according to the pulse repetition period
A two-dimensional matrix is arranged in range cell, wherein, identical pulse repetition period, the echo-signal of different distance unit are by row
Arrangement, i.e., the different range cell of each row correspondence；Different pulse repetition periods, the echo-signal of same distance unit is arranged by row
Row, that is, arrange the correspondence different pulse repetition period；Time difference between i.e. each row adjacent two data is precisely that pulse is repeated
Cycle；During using pulse compression signal, range gate width is taken as the pulse width after pulse compression；
Mutually inspection output work of the described Moveing target indication MTI modules by same range cell within the adjacent repetition period subtracts each other
Computing, completion offsets fixed echo, while clutter at a slow speed of significantly decaying, retains Moving Target Return.
Described Moveing target indication MTI modules realize that the basic element of mti filter is to prolong using mti filter
The slow time is equal to the delay line of repetition period, and the mti filter of zero-frequency clutter/land clutter should be at zero-frequency and its cycle appearance point
Form recess；Described mti filter is two pulse cancellers or three pulse canceller.
Described correlative accumulation MTD modules need to carry out M N points plural number FFT computings, M in N number of accumulation pulse period domestic demand
It is range cell；Correlative accumulation MTD modules are realized using one group of adjacent and partly overlapping arrowband Doppler filter group, described
Arrowband Doppler filter group cover the whole frequency range of target Doppler frequency, realize that moving-target is detected, quite
In carrying out correlative accumulation to different passages；Wherein, N number of adjacent arrowband Doppler filter group is the horizontal stroke by N number of output
To wave filter by each repetition period different weights and realize after suing for peace, the transversal filter of described N number of output includes N number of
Repetition period and N-1 root delay lines.
Described CFAR detection module is controlled by appropriate thresholding, makes the false-alarm probability of detection constant；Described perseverance
False-alarm detection module includes multiple CFAR detection units and a multichannel selects big unit, the number of described CFAR detection unit
Amount is identical with the output way of correlative accumulation MTD modules, and each CFAR detection unit is received from correlative accumulation MTD moulds respectively
The single channel output of each range cell of block, export after CFAR detection judgement to multichannel and selects big unit, and multichannel choosing is big single
Unit carries out the comparing on longitudinal Doppler's passage, selects the maximum of each range cell, obtains multichannel and selects big result.
Respectively there is a sliding window for some range cells of covering in described CFAR detection unit lead and trail edge, utilize
The average of reference sample in sliding window, forms before and after edge partial estimation, then it is average to partial estimation, choosing is big, it is small to select or weighting is flat
, estimated with determining the background clutter mean power of CFAR detection unit.
The beneficial effects of the invention are as follows：The delay that the present invention passes through command range select gate, and channel signal process
With target is detected after filtering, MTD and CFAR detection, then carried out without fuzzy survey through tracking gate and apart from centering treatment
Away from, range gating ripple door is produced through Kalman filtering or alpha-beta filtering, the target for making center of tracking gate be aligned detected by echo is believed
Number, so as to ensure that ripple door movement automatically tracks target.
Brief description of the drawings
Fig. 1 is block diagram of the present invention；
Fig. 2 is Digital Down Converter Module theory diagram；
Fig. 3 is Time-Domain Pulse Compression module principle block diagram；
Fig. 4 is frequency-domain impulse compression module theory diagram；
Fig. 5 is secondary canceller theory diagram；
Fig. 6 is MTD Doppler filter group theory diagrams；
Fig. 7 is average class CFAR module principle block diagram；
Multichannel CFAR module Cleaning Principle block diagram when Fig. 8 is MTD working methods.
Specific embodiment
Technical scheme is described in further detail below in conjunction with the accompanying drawings：
As shown in figure 1, a kind of gate mould based on Radar Signal Processing System apart from tracing subsystem, including range gate
Block, pulse compression module, correlative accumulation MTD modules, CFAR detection module, tracking gate module, distance centering processing module,
Range finder module, Kalman filtering module/alpha-beta filtration module；Outside two-way I/Q and channel signal pass through range gate gating module
Detected into tracing subsystem, and after sequentially passing through pulse compression module, correlative accumulation MTD modules, CFAR detection module
Target, then carries out being found range without fuzzy after tracking gate module, distance centering processing module into range finder module, is passed through after range finding
Kalman filtering/alpha-beta filtration module produces range gating ripple door, the center of tracking gate of range gate gating module is directed at echo institute
The echo signal for detecting.
Specifically, the intermediate-freuqncy signal of the present embodiment is converted to data signal after carrying out analog-to-digital conversion module, then passes through again
Digital Down Convert, converts a signal into I, Q two-way baseband signal, and differ from three road I, Q signal respectively through range gating ripple door shape
Into gating signal, gating signal by exported after pulse compression narrow pulse signal, range gate reset buffer storage by data by
Originally chronological is changed into by range cell arrangement, carries out coherent to target by MTD afterwards and mutually tire out.By empty through perseverance with passage
Alert detection detection echo signal, and the range gating ripple door of subsequent time is formed by Kalman filtering after range finding, obtain energy
Amount.
During target following, in order to improve the interference free performance of system, it is necessary to distance, velocity information to target
Kalman filtering or alpha-beta filtering are carried out, the influence of strong noise jamming is prevented.Kalman filtering is a kind of linear unbiased minimum variance
Best estimate：That is after k-th cycle observation Z (K) is obtained, it is obtained with the estimate linear combination in previous cycle
The estimate in k-th cycleIts performance is optimal.
Further, in the present embodiment, described outside and channel signal pass through A/D modular converters and Digital Down Convert
Module is formed.
Wherein, it is sample frequency f that the major design of A/D converters considerssSelection, fsSelection and IF-FRE and letter
Number bandwidth is relevant, while in order that signal processor has bigger dynamic range, fsHeight should be measured, in order that signal processor to the greatest extent may be used
Energy ground is simple, fsShould be as low as possible, fsSelection be the result for considering these factors, by bandpass signal sample formula：
F in formula0It is 120MHz centre frequencies, B is 40MHz bandwidth, takes fs=160MHz (situation equivalent to n=1), should
Sample frequency can simultaneously take into account dynamic range and realize difficulty.
Direct intermediate frequency (IF) Sampling technology is that signal is directly sampled with A/D in intermediate frequency, after signal sampling, is got in return by becoming
To I, Q simple two-way signal.The uniformity of the orthogonal signalling for so obtaining is good, high precision, and other advantages with digital circuit,
So as to largely improve Radar Signal Processing System performance.
As shown in Fig. 2 described Digital Down Converter Module includes orthogonalization unit, digital controlled oscillator NCO, multiplier, FIR
Low pass filter and extracting unit, orthogonalization unit receive the digital medium-frequency signal from A/D modular converters and are orthogonalized
Form orthogonal I/Q two paths of signals, orthogonal local oscillation sequence (- sin (the 2 π * that two paths of signals is formed with digital controlled oscillator NCO respectively
Fi*n*ts) with cos (2 π * fi*n*ts)) it is multiplied, and export respectively to the FIR low pass filter on each road, low pass filter takes out
Baseband signal filters radio-frequency component, and baseband signal extract by extracting unit reduces signal rate, the output end of extracting unit
It is connected with range gate gating module.
Specifically, the function that digital quadrature down conversion module is completed includes 3 parts：One is orthogonalization, by digital intermediate frequency
Signal obtains orthogonal I, Q two paths of signals by orthogonalization module；Two is down coversion, digital mixer by digital medium-frequency signal and
Orthogonal local oscillation sequence is multiplied, and then takes out baseband signal by low pass filter, filters radio-frequency component；Three is to extract, to reduce
Signal rate.Multiplier and low pass filter are all completed by digital operation in DDC, in the absence of analog multiplier and analog low-pass
Range error and phase quadrature error that wave filter causes because circuit is inconsistent.
Centre frequency f0It is 120MHz, bandwidth B is 40MHz, sampling rate fs=160MHz, therefore NCO centre frequencies are
20MHz, extracting multiple is 2.
FIR low pass filter is designed as 128 ranks, and Out-of-band rejection reaches more than 65dB；Wave filter input data is 14, is
Number is 16, and sampling rate is 80Msps, wave filter output data bit wide 23.
Call special IP kernel to be filtered in ISE, specify the work clock of FIR filtering for 4 times of sampling clock (i.e.
320MHz), then it is 16 to need DSP resources in FPGA, and needs 16*2 (per the orthogonal I/Q of passage after differing from three road signal orthogonalizations
Two-way) * 3 (and difference triple channel)=96 DSP resources.
Described pulse compression module is used to realize matched filtering, using Time-Domain Pulse Compression module or frequency-domain impulse pressure
Contracting module；
Time-Domain Pulse Compression module uses FIR filter structures, by the pulse to echo sequence s (n) and matched filter
Response sequence h (n) seeks convolution to realize, to obtain output result needs to do four groups of related operations, wave filter multiple correlation computing
Amount is dramatically increased with the increase of signal time width, and the chip magnitude needed for completing computing is consequently increased.Process of pulse-compression
Time domain realizes that block diagram is as shown below.Matched filter coefficient is gripped altogether for the mirror image of linear FM signal complex envelope.In advance by institute
The filter coefficient for having waveform is deposited in the ROM of FPGA, during work, is read corresponding coefficient according to different radar waveforms and is entered
Row convolution algorithm.In order to suppress pulse pressure secondary lobe, also tackle matched filter and weighted using Hamming window.
As shown in figure 3, described Time-Domain Pulse Compression module includes four FIR matched filters and two adders；Its
In, the first input end of a FIR matched filters and the 2nd FIR matched filters receives I roads signal, FIR matchings
Second input of wave filter and the 2nd FIR matched filters receives Least square estimation respectively, a FIR matched filters and
2nd FIR matched filters export respectively after convolution algorithm to the first input end and second adder of first adder
First input end；The first input end of the 3rd FIR matched filters and the 4th FIR matched filters receives Q roads signal, the 3rd
Second input of FIR matched filters and the 4th FIR matched filters receives Least square estimation, the 3rd FIR matchings respectively
Wave filter and the 4th FIR matched filters are exported to the second input of first adder and second respectively after carrying out convolution algorithm
Second input of adder；First adder and second adder by exporting the matching filter of I/Q two-way respectively after add operation
Signal after ripple.
It can be seen that Time-Domain Pulse Compression needs 4 FIR filters to realize, required according to Waveform Design, LFM pulses
The most a width of 36us of width, when sampling rate is 80Msps, the coefficient of matched filter is 2880, input data bit wide 23
Position, coefficient bit wide 16, wave filter output data bit wide 32.
As shown in figure 4, frequency-domain impulse compression general principle be first to collect data signal s (n) does FFT,
It is set to transform to frequency domain, its frequency spectrum is S (w), then S (w) (is entered with the spectrum H (w) of matched filter using matched filtering coefficient
Row FFT is obtained) multiplication, the product for obtaining is carried out the result that IFFT computings obtain pulse compression.For frequency domain method, frequency domain
When processing big, its equipment amount increases little to digital pulse-compression during bandwidth signals, and frequency domain is used when big time width Signal for Pulse is processed
Processing system has obvious advantage.
Specifically, described frequency-domain impulse compression module includes FFT unit, complex multiplication unit, matched filter frequency spectrum
Unit, IFFT units, FFT unit are FFT and carry out map function and transforms to frequency spectrum and be respectively to the I/Q two ways of digital signals being input into
The frequency domain of S (w), the spectrum H (w) of the matched filter that complex multiplication unit exports S (w) with matched filter spectrum unit
It is multiplied, the achievement for obtaining is carried out the result that IFFT computings obtain pulse compression by IFFT units；Described spectrum H (w) is utilization
Matched filtering coefficient carries out what FFT was obtained.
Input data bit wide 23, H (k) coefficients are 16, and data bit width is 32 after multiplier output.
For different wave, resource of 3 passages required for time domain and frequency domain carry out pulse compression to 3 passages simultaneously and
Process time such as following table (with selected chip SCKU115 as platform)：
Visible in table, under such condition, frequency domain technique has relative to time-domain processing method in terms of FPGA resource
Obvious advantage, therefore, the present embodiment is intended using frequency-domain impulse compression treatment.
Further, in the present embodiment, also include sequentially connecting between pulse compression module and correlative accumulation MTD modules
The range gate reordering module and Moveing target indication MTI modules for connecing.
Wherein, realizing that range gate is reset needs two-dimentional buffer storage, by radar echo signal according to the pulse repetition period
A two-dimensional matrix is arranged in range cell.The identical pulse repetition period, the echo-signal of different distance unit by rows,
The different range cell of i.e. each row correspondence；Different pulse repetition periods, the echo-signal of same distance unit is arranged by row, that is, arrange
The correspondence different pulse repetition period.It follows that the time difference between each row adjacent two data is precisely pulse repeating
Cycle.
During using pulse compression signal, range gate width is taken as the pulse width after pulse compression.Data are from single distance
Door is read and is sent to follow-up clutter treatment and Doppler filter group, and the data from different distance door are analyzed successively.
After sampled data enters rearrangement according to form above, by the way that to this frame data, the fuzzy of target can be obtained
Distance or fuzzy speed.MTD carries out doppler filtering to the N point datas of each range cell successively, to ensure in whole process
The filtering of each range cell can be completed in N*Tr (coherent processing be spaced CPI), be input into read-out speed (the i.e. wave filter of storage
Processing speed) typically can be more quicker than its writing rate.
Need to design storages of the RAM to realize range gate 2-D data, input data bit wide 32, if needed in FPGA
The target in the range of 375 meters is detected, it is necessary to range gate number M is 100.
For different wave, three passages resource such as following table required in data rearrangement：
When fixed target, land clutter etc. are in same range cell with moving target, the former echo is generally relatively strong, with
Echo as moving target is submerged wherein, therefore must try to make a distinction the two.For moving-target and the difference of clutter
Additive operation is made in doppler characterization, the mutually inspection output by same range cell within the adjacent repetition period, then permanent echo
To be done and offset, clutter also will largely be decayed at a slow speed, and only Moving Target Return is retained.Obviously so just
Fixed target, at a slow speed clutter and moving target can be made a distinction.By Moveing target indication (MTI) technology, using mti filter
Corresponding clutter is filtered, fixed land clutter is suppressed, so as to improve target detection performance.
During pulsed operation state, signal is repeated by repetition period interval, therefore the frequency response of wave filter used also should be
Comb teeth-shaped.The basic element of wave filter is the delay line that time delay is equal to the repetition period, zero-frequency clutter (land clutter)
Mti filter recess should be formed at zero-frequency and its cycle appearance point.
Because clutter spectrum has certain width, and this project objective Doppler frequency is not high, therefore answers reasonable design
Mti filter.
The most frequently used zero-frequency mti filter is binomial wave filter, wherein most typically first-order cancellation device (two pulses
Offset) and secondary canceller (three pulses are offseted).
Shown in theory diagram Fig. 5 of secondary canceller or three pulse canceller, input data is a base band plural number sample
This, these are that same range cell is returned by sequential pulse, form effective sampling interval TrDiscrete time sequence
Row x (n).Domain equation is at that time：Y (n)=x (n) -2*x (n-l)+x (n-2), the transmission function of fixed cancellation device is H (z)
=1-2*Z-1+Z-2。
Cancellation device is offseted relative to once, it will be apparent that improve the null and notch width of zero Technique for Doppler Frequency, is improved
The performance of clutter recognition.
Although cancellation device has suppression recess wider compared with a canceller, clutter suppression capability has strengthened, and leads to
Gain in band is still very big, it is possible to also inhibits transient echo, and the method for improving mti filter pass-band performance is to increase
Feedback branch, designs so-called recursion filter.
In the present embodiment, moving-target detection process are that one kind suppresses various clutters using Doppler filter, to carry
Radar high detects the technology of moving target ability under clutter background.MTD is using one group of adjacent and partly overlapping Doppler's filter
Ripple device group, covers the whole frequency range of target Doppler frequency, and to reach the purpose of moving-target detection, its essence is quite
In carrying out correlative accumulation to different passages.
Because clutter is different with the Doppler frequency shift of target, they will appear in different Doppler filter output ends,
Doppler frequency difference has corresponded to different narrow band filter outputs, thus, MTD can also be defeated according to different narrow band filters
Go out to obtain Doppler frequency shift and then the speed to determine target.
In digitized processing, the method that MTD generally uses digital filtering, as shown in fig. 6, the transverse direction with N number of output
Filtering (N number of repetition period and N-1 roots delay line), by after the different weights of each repetition period and summation, you can realize N number of phase
Adjacent narrow band filter group.The frequency coverage of the wave filter is 0 to fr, and fr rushes repetition rate for radar work time pulse, its
Principle structure block diagram is as illustrated, (Tr is the pulse repetition period).
Because DFT is a kind of special transversal filter, if weighted factor presses DFT definition selections in figure, and using DFT's
Fast algorithm FFT, so that it may realize that the MTD based on FFT is filtered.N number of wave filter that N points FFT is formed is evenly distributed on 0~fr frequencies
In interval, echo signal possibly be present on the diverse location of frequency axis due to the difference of Doppler frequency, it is thus possible to from 0~
N-1 wave filters are exported.Specific practice is
One group of data to the same range cell of each pulse are FFT to obtain equivalent wave filter group.
MTD needs to carry out the secondary N points plural number FFT computings of M (range cell) in N number of accumulation pulse period domestic demand.Assuming that FFT is defeated
Enter data bit width 32, worked under 320MHz treatment clocks, then 1 calculation resources of passage such as following table：
Because process time only has 5.1us, and N number of accumulation pulse period is far longer than process time, so 3 passages
FFT can use flow processing method.
In the present embodiment, echo-signal is permanent by carrying out CFAR detection treatment after doppler filtering and envelope detection
False-alarm (CFAR) detection is controlled by appropriate thresholding, makes the false-alarm probability of detection constant.CFAR treatment can make radar strong
Interference is lower to lose a little detectability but remains to normal work.
Suitable for spatially counting stable background, it respectively has a covering to average class CFAR in detection unit before and after edge
The sliding window of some range cells, using the average of reference sample in sliding window, forms before and after edge partial estimation, then to part
Estimate that average, choosing is big, select small or weighted average, estimated with the background clutter mean power for determining detection unit.In view of signal can
In crossing front and rear adjacent unit, detection unit and its close on longitudinal separation unit and be generally not included in average window, such as
Fruit echo signal then finds target more than computing detection threshold, and otherwise target cannot be found.Compare in average class CFAR
Typical several method is that CA-CFAR (CA-CFAR), both sides cell-average select big CFAR (GO-CFAR), both sides
Cell-average selects small CFAR (SO-CFAR) and unit weighted average CFAR (WCA-CFAR).Schematic diagram is as shown with 7.
Radar echo signal by MTD it is filtered output be exactly N number of wave filter output, each data have distance with
Two parameters of frequency, so needing using two-dimentional CFAR detection.CFAR detection is that the output of N number of wave filter needs to be sent to
N number of CFAR detection circuit, the detection threshold of each wave filter can be according to the power of institute's Noise and clutter in the wave filter
And determine in real time.
MTD wave filters have multiple-channel output, so need to be detected using multichannel CFAR, as shown in Figure 8.Individual pulse each away from
After unit detection judgement output, then the comparing on longitudinal direction i.e. Doppler's passage is carried out, selected in each range cell most
Big value, obtains multichannel and selects big result.The MTD results of N number of passage are big by choosing, finally export single channel CFAR results.
FPGA operands：512 plural modulus computings are at most done under each timeticks, approximate data can be used, only
Needs compare to be realized with addition.
Claims (8)
1. it is a kind of based on Radar Signal Processing System apart from tracing subsystem, it is characterised in that：Mould is gated including range gate
Block, pulse compression module, correlative accumulation MTD modules, CFAR detection module, tracking gate module, distance centering processing module,
Range finder module, Kalman filtering module/alpha-beta filtration module；Outside two-way I/Q and channel signal pass through range gate gating module
Detected into tracing subsystem, and after sequentially passing through pulse compression module, correlative accumulation MTD modules, CFAR detection module
Target, then carries out being found range without fuzzy after tracking gate module, distance centering processing module into range finder module, is passed through after range finding
Kalman filtering/alpha-beta filtration module produces range gating ripple door, the center of tracking gate of range gate gating module is directed at echo institute
The echo signal for detecting.
2. it is according to claim 1 it is a kind of based on Radar Signal Processing System apart from tracing subsystem, it is characterised in that：
Described outside and channel signal is formed by A/D modular converters and Digital Down Converter Module；Described A/D modular converters are received
Outside intermediate frequency echo and signal simultaneously directly carry out A/D samplings to signal in intermediate frequency, and signal sampling formula is as follows：
In formula, f0It is xMHz centre frequencies, B is yMHz bandwidth, and n is natural number；
Described Digital Down Converter Module includes orthogonalization unit, digital controlled oscillator NCO, multiplier, FIR low pass filter and takes out
Unit is taken, orthogonalization unit receives the digital medium-frequency signal from A/D modular converters and is orthogonalized to form orthogonal I/Q two
Road signal, the orthogonal local oscillation sequence that two paths of signals is formed with digital controlled oscillator NCO respectively is multiplied, and exports respectively to each road
FIR low pass filter, low pass filter takes out baseband signal and filters radio-frequency component, and baseband signal is carried out extraction drop by extracting unit
Low signal speed, the output end of extracting unit is connected with range gate gating module.
3. it is according to claim 1 it is a kind of based on Radar Signal Processing System apart from tracing subsystem, it is characterised in that：
Described pulse compression module is used to realize matched filtering, using Time-Domain Pulse Compression module or frequency-domain impulse compression module；
Described Time-Domain Pulse Compression module includes four FIR matched filters and two adders；Wherein, FIR matchings
The first input end of wave filter and the 2nd FIR matched filters receives I roads signal, a FIR matched filters and the 2nd FIR
Second input of matched filter receives Least square estimation, a FIR matched filters and the 2nd FIR matched filterings respectively
Device carries out the first input end of the first input end and second adder exported respectively after convolution algorithm to first adder；3rd
The first input end of FIR matched filters and the 4th FIR matched filters receives Q roads signal, the 3rd FIR matched filters and
Second input of the 4th FIR matched filters receives Least square estimation, the 3rd FIR matched filters and the 4th FIR respectively
Matched filter export respectively after convolution algorithm to first adder the second input and second adder it is second defeated
Enter end；The signal of first adder and second adder after exporting I/Q two-way matched filterings after add operation respectively；
Described frequency-domain impulse compression module includes that FFT unit, complex multiplication unit, matched filter spectrum unit, IFFT are mono-
Unit, it is the frequency domain of S (w) that FFT unit is FFT to the I/Q two ways of digital signals being input into and carry out map function to transform to frequency spectrum respectively,
Be multiplied for the spectrum H (w) of the matched filter exported with matched filter spectrum unit of S (w) by complex multiplication unit, and IFFT is mono-
The achievement for obtaining is carried out the result that IFFT computings obtain pulse compression by unit；Described spectrum H (w) is using matched filtering coefficient
Carry out what FFT was obtained.
4. it is according to claim 1 it is a kind of based on Radar Signal Processing System apart from tracing subsystem, it is characterised in that：
Also include the range gate reordering module and the Moveing target indication that are sequentially connected between pulse compression module and correlative accumulation MTD modules
MTI modules；
Described range gate reordering module using two-dimentional buffer storage, by radar echo signal according to the pulse repetition period and away from
A two-dimensional matrix is arranged in from unit, wherein, identical pulse repetition period, the echo-signal of different distance unit are arranged by row
Row, i.e., the different range cell of each row correspondence；Different pulse repetition periods, the echo-signal of same distance unit is arranged by row,
Arrange the correspondence different pulse repetition period；Time difference between i.e. each row adjacent two data is precisely that pulse repeats week
Phase；During using pulse compression signal, range gate width is taken as the pulse width after pulse compression；
Mutually inspection output work of the described Moveing target indication MTI modules by same range cell within the adjacent repetition period subtracts each other fortune
Calculate, completion offsets fixed echo, while clutter at a slow speed of significantly decaying, retains Moving Target Return.
5. it is according to claim 4 it is a kind of based on Radar Signal Processing System apart from tracing subsystem, it is characterised in that：
Described Moveing target indication MTI modules realize that the basic element of mti filter is time delay etc. using mti filter
In the delay line of repetition period, the mti filter of zero-frequency clutter/land clutter should form recessed at zero-frequency and its cycle appearance point
Mouthful；Described mti filter is two pulse cancellers or three pulse canceller.
6. it is according to claim 1 it is a kind of based on Radar Signal Processing System apart from tracing subsystem, it is characterised in that：
Described correlative accumulation MTD modules need to carry out M N points plural number FFT computing in N number of accumulation pulse period domestic demand, and M is single distance
Unit；Correlative accumulation MTD modules realize that described arrowband is more using one group of adjacent and partly overlapping arrowband Doppler filter group
It is general to strangle the whole frequency range that wave filter group covers target Doppler frequency, realize that moving-target is detected, equivalent to difference
Passage carry out correlative accumulation；Wherein, N number of adjacent arrowband Doppler filter group is the transversal filter by N number of output
Realized by after the different weights of each repetition period and summation, the transversal filter of described N number of output includes N number of repetition period
With N-1 root delay lines.
7. it is according to claim 1 it is a kind of based on Radar Signal Processing System apart from tracing subsystem, it is characterised in that：
Described CFAR detection module is controlled by appropriate thresholding, makes the false-alarm probability of detection constant；Described CFAR detection
Module includes multiple CFAR detection units and a multichannel selects big unit, the quantity and coherent of described CFAR detection unit
The output way for accumulating MTD modules is identical, and each CFAR detection unit receives each from correlative accumulation MTD modules respectively
The single channel output of range cell, export to multichannel after CFAR detection judgement selecting big unit, and multichannel selects big unit to be indulged
To the comparing on Doppler's passage, the maximum of each range cell is selected, obtain multichannel and select big result.
8. it is according to claim 7 it is a kind of based on Radar Signal Processing System apart from tracing subsystem, it is characterised in that：
Respectively there is a sliding window for some range cells of covering in described CFAR detection unit lead and trail edge, using in sliding window
The average of reference sample, forms before and after edge partial estimation, then it is average to partial estimation, choosing is big, small or weighted average is selected, with true
The background clutter mean power for determining CFAR detection unit is estimated.
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