CN113820677A - Secondary peak suppression method for Link16 signal external radiation source radar - Google Patents

Secondary peak suppression method for Link16 signal external radiation source radar Download PDF

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CN113820677A
CN113820677A CN202110882706.5A CN202110882706A CN113820677A CN 113820677 A CN113820677 A CN 113820677A CN 202110882706 A CN202110882706 A CN 202110882706A CN 113820677 A CN113820677 A CN 113820677A
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CN113820677B (en
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王俊
白路阳
严言
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Xidian University
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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
    • 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
    • G01S7/411—Identification of targets based on measurements of radar reflectivity
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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Abstract

The invention discloses a secondary peak suppression method of a Link16 signal external radiation source radar, which is applied to a Link16 external radiation source radar and comprises the following steps: receiving a reference signal sent by a Link16 radiation source through the reference antenna, and receiving an echo signal reflected by a target through the receiving antenna; preprocessing the reference signal and the echo signal to obtain a digital reference signal and a digital echo signal; solving to obtain a target neighborhood mismatched filter factor based on the digital reference signal; according to the time slot structure of the Link16 signal, removing a jitter part and a transmission protection part in a target neighborhood mismatched filter factor corresponding to the reference signal, and removing the jitter part and the transmission protection part of the digital echo signal; and performing two-dimensional coherent processing on the target neighborhood mismatched filter factor and the digital echo signal after the elimination processing to obtain a target fuzzy function. The invention can effectively inhibit the time delay dimension and Doppler dimension secondary peak in the fuzzy function.

Description

Secondary peak suppression method for Link16 signal external radiation source radar
Technical Field
The invention belongs to the technical field of radars, and particularly relates to a secondary peak suppression method for a Link16 signal external radiation source radar.
Background
The external radiation source radar is a dual/multi-base radar with separate receiving and transmitting, carries out passive detection by receiving electromagnetic signals of non-cooperative radiation sources reflected by a target, and has the advantages of strong concealment, low cost, no electromagnetic pollution and the like. The prior art generally realizes detection in environments such as cities based on irradiation sources such as frequency modulation broadcasting, analog television, digital television and mobile communication, but does not have the irradiation sources in environments such as oceans and gobi which are far away from densely populated areas. Thus, in environments away from the oceans, gobi, etc. of densely populated areas, detection may be based on military radiation sources. Typical military radiation sources include Tactical Data Links (TDL) and the like, wherein Link16 Data Link signals, also known as Link16 signals, are included in the Tactical Data Link.
The Link16 data Link signal consists of the J-series message standard, JTIDS waveform, and Time Division Multiple Access (TDMA) protocol. Wherein, the J series message is baseband information transmitted by a Link16 data chain; the JTIDS waveform is a transmission waveform which is suitable for transmission and strong in anti-interference performance and is generated by the JTIDS terminal machine according to J series messages; TDMA protocols are used to control access by users. Specifically, J series messages are subjected to Cyclic Redundancy Check (CRC) coding, RS coding, symbol interleaving, Cyclic Code Shift Keying (CCSK) coding spreading, codeword encryption, Minimum Shift Keying (MSK) modulation, frequency hopping in a JTIDS terminal, and are added with a synchronization transmission symbol and a preamble to generate a strong interference immunity JTIDS waveform suitable for transmission, and are encapsulated according to a Standard Double Pulse (STDP) structure. As shown in fig. 1, the STDP package structure specifies that 1 slot consists of a jitter, coarse synchronization, fine synchronization, header, data and transmission protection part, wherein the jitter and transmission protection part is a signal gap, and the rest is an MSK modulated pulse signal occurring in pairs, i.e. the same set of 32 symbols is transmitted with two pulses.
However, the pulsed slot structure of Link16 signal and the dual pulse information transmission structure specific to STDP package will cause periodicity, which will cause a series of fuzzy secondary peaks in the delay dimension and doppler dimension of its fuzzy function, resulting in the fuzzy function not being ideal pin-shaped.
Further, as shown in fig. 2, the external radiation source radar detects a target by using two pairs of receiving antennas, one pair is used for receiving a direct wave emitted by a non-cooperative radiation source as a reference signal to obtain a transmitted signal sample, the other pair is used for receiving an echo signal reflected by the target, then the reference signal and the echo signal are subjected to range-doppler two-dimensional coherent processing, and the range and doppler information of the target can be obtained by searching a peak value on a delay-doppler two-dimensional plane of a mutual ambiguity function of the reference signal and the echo signal. However, because the periodicity causes the ambiguity function to generate a series of ambiguity sub-peaks, the delay dimension and doppler dimension sub-peaks of the ambiguity function of Link16 signal will generate false alarm and false alarm during target detection, which will seriously affect the detection performance.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a secondary peak suppression method for a Link16 signal external radiation source radar. The technical problem to be solved by the invention is realized by the following technical scheme:
a method for suppressing secondary peaks of Link16 signal external radiation source radar is applied to Link16 external radiation source radar, wherein an antenna is deployed in the external radiation source radar, and the antenna comprises a reference antenna and a receiving antenna, and the method comprises the following steps: step 1: receiving a reference signal sent by a Link16 radiation source through the reference antenna, and receiving an echo signal reflected by a target through the receiving antenna; step 2: preprocessing the reference signal and the echo signal to obtain a digital reference signal and a digital echo signal; and step 3: solving to obtain a target neighborhood mismatched filter factor based on the digital reference signal; and 4, step 4: according to the time slot structure of the Link16 signal, removing a jitter part and a transmission protection part in a target neighborhood mismatched filter factor corresponding to the reference signal, and removing the jitter part and the transmission protection part of the digital echo signal; and 5: and performing two-dimensional coherent processing on the target neighborhood mismatched filter factor and the digital echo signal after the elimination processing to obtain a target fuzzy function.
In one embodiment of the present invention, the step 1 comprises: step 1-1: receiving Link through the reference antennaThe reference signal sent by the 16 radiation sources is represented as: let T be the minimum FSK pulse repetition period of the Link16 signalpPulse width of TpdSymbol width of TB(ii) a The time slot length of the standard double-pulse packaging structure is TsJitter duration of TjEffective part length is TdTransmission guard duration of Tpr(ii) a The reference signal is denoted as s (t), and the received reference signal is:
Figure BDA0003192646710000031
wherein, t1＝nTs+Tj+iTp，t2＝nTs+Tj+Td+iTp+Tpd，fcCarrier frequency, Δ f, of the initial pulsen,iIndicating the offset of the carrier frequency, m, of the ith pulse of the nth time slot from the start pulsen,i(t) is a baseband complex envelope of the symbol of the ith pulse of the nth time slot after minimum frequency shift keying modulation; m isn,i(t), expressed as:
Figure BDA0003192646710000032
wherein the content of the first and second substances,
Figure BDA0003192646710000041
and
Figure BDA0003192646710000042
representing the serial-to-parallel converted symbol, mn,2i-1＝mn,2i；
Step 1-2: receiving, by the receiving antenna, an echo signal reflected by a target, as:
Figure BDA0003192646710000043
wherein s isecho(t) representsEcho signal, alpha representing amplitude factor, tau representing time delay of target, fdRepresenting the doppler frequency of the target.
In one embodiment of the present invention, the preprocessing the reference signal includes: step 2-11: amplifying the reference signal; step 2-12: carrying out orthogonal down-conversion processing on the carrier frequency and the offset of the carrier frequency in the reference signal so as to eliminate the carrier frequency and the offset of the carrier frequency; step 2-13: performing a/D sampling on the reference signal from which the carrier frequency and the offset of the carrier frequency are removed to obtain a digital reference signal, which is expressed as:
Figure BDA0003192646710000044
wherein, s [ l]Representing a digital reference signal, l representing the ith sample point,
Figure BDA0003192646710000045
l1＝(nTs+Tj+iTp)fs，l2＝(nTs+Tj+Td+iTp+Tpd)fs，fsis the sampling rate.
The invention has the beneficial effects that:
the invention can calculate the target neighborhood mismatched filter factor according to the received reference signal so as to inhibit the time delay dimension secondary peak, then eliminates the corresponding jitter and transmission protection parts corresponding to all time slots of the target neighborhood mismatched filter factor, and eliminates the jitter and transmission protection parts corresponding to all time slots of the digital echo signal so as to inhibit the Doppler dimension secondary peak. Therefore, the method can avoid the time delay dimension and Doppler dimension secondary peak of the fuzzy function of the Link16 signal, and can solve the problems of false alarm and false alarm leakage during detection based on the fuzzy function after the distance-Doppler two-dimensional coherent processing is carried out on the digital reference signal and the echo signal.
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Drawings
FIG. 1 is a schematic diagram of a time slot structure in a standard double-pulse package structure provided in the present invention;
FIG. 2 is a schematic diagram of target detection based on an external radiation source radar provided by the invention;
FIG. 3 is a schematic flow chart of a secondary peak suppression method of a Link16 signal external radiation source radar according to an embodiment of the present invention;
fig. 4(a), fig. 4(b) and fig. 4(c) are schematic diagrams of fuzzy functions when the secondary peak suppression is not performed in a simulation experiment of the secondary peak suppression method of the Link16 signal external radiation source radar provided by the embodiment of the present invention;
fig. 5(a) and 5(b) are schematic diagrams of time delay dimensional fuzzy functions after inhibiting time delay dimensional secondary peaks by using a conventional mismatch filtering algorithm and a neighborhood mismatch filtering algorithm in a simulation experiment of a secondary peak inhibition method of a Link16 signal external radiation source radar provided by the embodiment of the present invention;
fig. 6 is a fuzzy function diagram of a secondary peak suppression method for Link16 signal external radiation source radar, which is provided by the embodiment of the present invention, for suppressing a doppler-dimensional secondary peak by removing a jitter and transmission protection part of a time slot in a simulation experiment;
fig. 7 is a schematic diagram of a target fuzzy function after sub-peak suppression processing in a simulation experiment of a sub-peak suppression method for Link16 signal external radiation source radar according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
Examples
Referring to fig. 3, fig. 3 is a schematic flow chart of a method for suppressing secondary peaks of a Link16 signal external radiation source radar according to an embodiment of the present invention.
Due to strong correlation between two adjacent MSK (minimum shift keying) pulses before and after Link16 signal STDP (standard double pulse) packaging, a secondary peak appears in a time delay dimension when distance-Doppler two-dimensional coherent processing is carried out on a reference signal and an echo signal at a position where the sliding time is equal to a pulse repetition period; meanwhile, since the Link16 signal has a pulse-type time slot structure, a secondary peak appears in a doppler dimension when the reference signal and the echo signal are subjected to range-doppler two-dimensional coherent processing at a frequency which is an integral multiple of the reciprocal of the time slot length, and the secondary peak on a delay-doppler two-dimensional plane can seriously affect the target detection performance.
According to the method, the neighborhood mismatch filter factors can be solved according to the reference signals, the correlation between the neighborhood mismatch filter factors and the original signals is weakened, and the time delay dimension secondary peak is restrained; and then, the jitter and transmission protection parts corresponding to the neighborhood mismatch filter factor and the echo signal are removed, so that the pulse structure of the Link16 signal time slot is damaged, the Doppler dimension secondary peak is inhibited, and the target detection performance can be further improved.
The invention is applied to Link16 external radiation source radar, wherein the external radiation source radar is provided with an antenna, the antenna comprises a reference antenna and a receiving antenna, and the method comprises the following steps:
step 1: and receiving a reference signal sent by a Link16 radiation source through the reference antenna, and receiving an echo signal reflected by a target through the receiving antenna.
Wherein the reference antenna is directed towards Link16 radiation source and the receiving antenna is directed towards the observation area.
Optionally, step 1 includes:
step 1-1: receiving, by the reference antenna, a reference signal sent by a Link16 radiation source, where:
let T be the minimum FSK pulse repetition period of the Link16 signalpPulse width of TpdSymbol width of TB(ii) a The time slot length of the standard double-pulse packaging structure is TsJitter duration of TjEffective part length is TdTransmission guard duration of Tpr(ii) a The reference signal is denoted as s (t), and the received reference signal is:
Figure BDA0003192646710000071
wherein, t1＝nTs+Tj+iTp，t2＝nTs+Tj+Td+iTp+Tpd，fcCarrier frequency, Δ f, of the initial pulsen,iIndicating the offset of the carrier frequency, m, of the ith pulse of the nth time slot from the start pulsen,i(t) is a baseband complex envelope of the symbol of the ith pulse of the nth time slot after minimum frequency shift keying modulation;
m isn,i(t), expressed as:
Figure BDA0003192646710000072
wherein the content of the first and second substances,
Figure BDA0003192646710000073
and
Figure BDA0003192646710000074
representing the serial-to-parallel converted symbol, mn,2i-1＝mn,2i。
Since the pulses in the STDP package occur in pairs, i.e. the same set of 32 symbols is transmitted with two pulses at different carrier frequencies, there is mn,2i-1＝mn,2i。
Step 1-2: receiving, by the receiving antenna, an echo signal reflected by a target, as:
Figure BDA0003192646710000075
wherein s isecho(t) represents the echo signal, α represents the amplitude factor, τ represents the time delay of the target, fdRepresenting the doppler frequency of the target.
Step 2: and preprocessing the reference signal and the echo signal to obtain a digital reference signal and a digital echo signal.
Optionally, the preprocessing the reference signal includes:
step 2-11: amplifying the reference signal;
step 2-12: carrying out orthogonal down-conversion processing on the carrier frequency and the offset of the carrier frequency in the reference signal so as to eliminate the carrier frequency and the offset of the carrier frequency;
step 2-13: performing a/D sampling on the reference signal from which the carrier frequency and the offset of the carrier frequency are removed to obtain a digital reference signal, which is expressed as:
Figure BDA0003192646710000081
wherein, s [ l]Representing a digital reference signal, l representing the ith sample point,
Figure BDA0003192646710000082
l1＝(nTs+Tj+iTp)fs，l2＝(nTs+Tj+Td+iTp+Tpd)fs，fsis the sampling rate.
Optionally, the echo signal is preprocessed, including
Step 2-21: amplifying the echo signal;
the Link16 external radiation source radar is provided with a receiver and a signal processor, wherein a preamplifier is arranged in the receiver, and the invention can amplify reference signals and echo signals through the preamplifier.
Step 2-22: carrying out orthogonal down-conversion processing on the carrier frequency and the offset of the carrier frequency in the echo signal so as to eliminate the carrier frequency and the offset of the carrier frequency;
step 2-23: and A/D sampling is carried out on the echo signal after the carrier frequency and the offset of the carrier frequency are eliminated, so as to obtain a digital echo signal, and the digital echo signal is expressed as:
Figure BDA0003192646710000083
wherein s isecho[l]Being digital echo signals, echoesThe signal vector is secho＝[secho[1] secho[2]…secho[l-1]]T。
And step 3: and solving to obtain a target neighborhood mismatched filter factor based on the digital reference signal.
Usually, the secondary peak of the time delay dimension of the Link16 signal fuzzy function is caused by strong correlation caused by the periodic structure of the pulse, so the secondary peak of the time delay dimension can be removed by a neighborhood mismatch filtering algorithm.
Constructing a cost function J to restrain the signal-to-noise ratio loss and the energy sum of the secondary peak of neighborhood mismatch:
Figure BDA0003192646710000084
wherein the content of the first and second substances,
Figure BDA0003192646710000085
for the neighborhood mismatch filter factor to be solved, w ═ s [0 [ ]] s[1]…s[l-1]]TTo match the filter factor, cnWeight > 0, d denotes the position of the secondary peak, U (d, δ) denotes the δ neighborhood of point d, i.e., U (d, δ) { k | d- δ < k < d + δ }, s [ k [, δ [, k ] ]]＝[s[k] s[k+1]…s[k+L-1]]TAnd L is the length of the signal.
The Hessian matrix of the cost function J is:
Figure BDA0003192646710000091
wherein, ILIs an L-order identity matrix, and because the Hessian matrix of the cost function J is a semi-positive definite matrix, the cost function J is a convex function, and the order of the cost function J is a convex function
Figure BDA0003192646710000092
The optimal solution of the neighborhood mismatched filter factor can be obtained, wherein:
Figure BDA0003192646710000093
the optimal solution for the neighborhood mismatched filter factor is then:
Figure BDA0003192646710000094
in order to reduce the operation amount, the neighborhood mismatch filtering factor is subjected to segmentation processing.
Optionally, step 3 includes:
step 3-1: the digital reference signal is processed in segments, which is expressed as: sb[k]Wherein s isb[k]＝[s[k+bLB] s[k+1+bLB]…s[k+LB-1+bLB]]TB represents the total number of segments, and the length of the neighborhood mismatched filter factor of each segment is LBAnd satisfies the relationship L ═ BLBB represents the B-th section, and B is 1, 2 and 3 … B;
step 3-2: solving each segment of digital reference signals based on a neighborhood mismatch filtering optimal solution expression to obtain a neighborhood mismatch filtering factor corresponding to each segment of digital reference signals, wherein the neighborhood mismatch filtering optimal solution expression is expressed as:
Figure BDA0003192646710000101
wherein the content of the first and second substances,
Figure BDA0003192646710000102
Figure BDA0003192646710000103
is LBAn order identity matrix;
in particular, wb＝[s[bLB] s[1+bLB]…s[LB-1+bLB]]T；
Step 3-3: splicing all the neighborhood mismatched filter factors to obtain a target neighborhood mismatched filter factor, which is expressed as:
Figure BDA0003192646710000104
in the step 3 of the invention, through a neighborhood mismatch filtering algorithm, the correlation between adjacent pulses in the Link16 signal STDP package can be destroyed, so that a time delay dimension secondary peak is eliminated.
And 4, step 4: and according to the time slot structure of the Link16 signal, removing a jitter part and a transmission protection part in a target neighborhood mismatched filter factor corresponding to the reference signal, and removing the jitter part and the transmission protection part of the digital echo signal.
In general, the fuzzy function of the Link16 signal can be expressed as:
Figure BDA0003192646710000105
wherein, χs,k(τs,fd) And (k ═ n-m) represents the mutual ambiguity function of the nth time slot and the mth time slot, the doppler dimension of the Link16 signal ambiguity function is:
Figure BDA0003192646710000106
thus, the envelope of the Doppler dimension of the Link16 signal blur function is equal to
Figure BDA0003192646710000107
Is internally provided with
Figure BDA0003192646710000111
Filling with the first sub-peak at
Figure BDA0003192646710000112
The amplitude of the secondary peak is larger than that of the secondary peaks at other positions, which affects the target detection.
Therefore, the secondary peak of the Doppler dimension is caused by the pulse type structure of the Link16 signal time slot, and in order to inhibit the secondary peak of the Doppler dimension, the effective parts of the remaining time slots are spliced by eliminating the jitter and transmission protection part corresponding to the neighborhood mismatch filter factor and the jitter and transmission protection part corresponding to the echo signal which are calculated according to the reference signal.
Optionally, the removing the jitter portion and the transmission protection portion in the target neighborhood mismatched filter factor corresponding to the reference signal includes:
and 4-11: based on a preset first threshold value kappa, carrying out mismatch filtering on the target neighborhood by using a filter factor wmisThe nth time slot in the target neighborhood mismatched filter factor is subjected to pulse rising edge detection to determine the number l of points corresponding to the ith element larger than kappa in the target neighborhood mismatched filter factori,n＝1.2.3.4…；
The step of detecting the rising edge of the pulse is to sequentially detect wmisThe value of the middle element is compared to κ.
And 4-12: calculating the point l corresponding to the ith element larger than kappaiNumber of points l corresponding to i +1 th element larger than ki+1The difference between, expressed as: li+1-li；
Step 4-13: analyzing the difference corresponding to the nth time slot, wherein when li+1-li＞TpfsWhen, determine li+1If the corresponding element does not belong to the current time slot, then wmis[l1],wmis[l1+1],wmis[l1+2],…,wmis[li]Assign values to w 'in order'misAnd w ismis[li+1],wmis[li+2]…, removing to remove the jitter part and transmission protection part of the nth time slot in the target neighborhood mismatched filter factor corresponding to the reference signal;
and 4-14: and repeating the steps 4-11 to 4-14 until the jitter part and the transmission protection part of all time slots in the target neighborhood mismatched filter factor are eliminated.
Optionally, the removing the jitter portion and the transmission protection portion of the digital echo signal includes:
step 4-21: based on a preset second threshold value kechoFor said digital echo signal sechoPerforms pulse rising edge detection to determine that the jth of the digital echo signals is greater than kechoThe number of points l corresponding to the element(s)j，m＝1.2.3.4…；
The step of detecting the rising edge of the pulse is to sequentially detect sechoValue of medium element and kappaechoA comparison is made.
And 4-22: calculate the jth > κechoThe number of points l corresponding to the element(s)jAnd j +1 th is greater than kappaechoThe number of points l corresponding to the element(s)j+1The difference between them, denoted as lj+1-lj；
And 4-23: analyzing the difference corresponding to the mth time slot, wherein when lj+1-lj＞TpfsWhen, determine lj+1If the corresponding element does not belong to the current time slot, s is setecho[l1],secho[l1+1],secho[l1+2],…,secho[lj]Assign values to s 'in order'echoAnd a isecho[lj+1]，secho[lj+2],., removing to remove the jittering part and the transmission protection part of the mth time slot in the digital echo signal;
and 4-24: and repeating the steps 4-21 to 4-24 until the jitter part and the transmission protection part of all time slots in the digital echo signal are eliminated.
The invention can destroy the pulse structure of Link16 signal time slot and eliminate Doppler dimension secondary peak through step 4.
And 5: and performing two-dimensional coherent processing on the target neighborhood mismatched filter factor and the digital echo signal after the elimination processing to obtain a target fuzzy function.
Optionally, the two-dimensional coherent processing is performed on the rejected target neighborhood mismatched filter factor and the digital echo signal to obtain a target fuzzy function, which is represented as:
Figure BDA0003192646710000121
wherein r ═ τ fsDenotes a distance delay unit, d ═ Lfd/fsRepresenting the doppler cell, | ψ (r, d) | representing the target blur function.
In summary, the invention uses the neighborhood mismatch filtering algorithm to destroy the correlation between adjacent pulses in the Link16 signal STDP package, and can solve the problem that the conventional mismatch filtering algorithm cannot effectively destroy the correlation between adjacent pulses, thereby effectively inhibiting the influence of the Link16 signal fuzzy function time delay dimension secondary peak on false alarm and false leakage generated in the target detection process, and then destroying the pulse structure of the Link16 signal time slot to inhibit the doppler dimension secondary peak by eliminating the jitter and transmission protection part corresponding to the neighborhood mismatch filtering factor and the echo signal, which are calculated according to the reference signal. Therefore, the method can avoid the time delay dimension and Doppler dimension secondary peak of the fuzzy function of the Link16 signal, and can solve the problems of false alarm and false alarm leakage during detection based on the fuzzy function after the distance-Doppler two-dimensional coherent processing is carried out on the digital reference signal and the echo signal, thereby improving the accuracy and efficiency of target detection.
Based on simulation experiments, the method of the invention is verified:
1. simulation conditions of the embodiment of the invention are as follows:
MSK pulse repetition period T for setting Link16 signal in experiment of the inventionp13 mus, pulse width Tpd6.4 mus, symbol width TBThe time slot length of the STDP packaging structure is T which is 0.2 mu ss7.8125ms, the jitter duration is Tj2ms, the effective part length is Td3.354ms, the transmission guard duration is Tpr2.4585ms, sample rate fs5MHz, coherent accumulation time T0.125 s, fuzzy function delay range 0 ≤ tau ≤ 0.2ms, and fuzzy function Doppler frequency shift range-2000 Hz ≤ fdLess than or equal to 2000Hz, 2496 segments, and L segmentsB＝250。
2. Simulation result analysis of the experiment of the invention:
fig. 4 is a fuzzy function graph when the Link16 signal is not subjected to sub-peak suppression, in which fig. 4(a) is a three-dimensional fuzzy function graph, fig. 4(b) is a time delay dimension fuzzy function graph, and fig. 4(c) is a doppler dimension fuzzy function graph. It can be seen that the ambiguity function of the Link16 signal consists of one main peak and time delay dimension secondary peaks and doppler dimension secondary peaks spread over the entire time delay-doppler two-dimensional plane. The secondary peak of the time delay dimension is TpThe continuation is carried out with the period of 13 mus, the secondary peak with the maximum amplitude is-5.61 dB at the position of tau 13 mus, and the amplitudes of the secondary peaks of the other delay dimensions are approximately equal to-26.44 dB. Secondary peak in the Doppler dimension of fd＝125Hz≈1/TsContinuation is carried out by taking 128Hz as period, and the secondary peak with maximum amplitude is positioned at fdThe peak amplitude of the other Doppler dimension is reduced in sequence at +/-125 Hz and 128Hz of-4.78 dB. The fuzzy function of the Link16 signal has serious secondary peaks, which can cause the appearance of false targets during target detection.
Fig. 5 is a time delay dimension fuzzy function graph after restraining time delay dimension secondary peaks by using a conventional mismatch filtering algorithm and a neighborhood mismatch filtering algorithm. Fig. 5(a) is a time delay dimension fuzzy function graph after being suppressed by using a conventional mismatch filtering algorithm, and fig. 5(b) is a time delay dimension fuzzy function graph after being suppressed by using a neighborhood mismatch filtering algorithm. It can be seen from the figure that the conventional mismatch filtering algorithm cannot effectively suppress the secondary peak amplitude of the delay dimension, and the secondary peak amplitude of the delay dimension is similar to that before suppression; the amplitude of the secondary peak of the time delay dimension can be effectively inhibited by using a neighborhood mismatch filtering algorithm, the amplitude of the first secondary peak is reduced by 13.69dB, and the amplitudes of the secondary peaks at other positions are all below-24 dB.
Fig. 6 is a graph of the blurring function of the time slot-clipped jitter and transmission guard portion to suppress doppler-dimensional secondary peaks, the amplitude of the first secondary peak is reduced by 20.95dB compared to that before the clipping, and the secondary peaks at the remaining positions are all below-25.72 dB.
Fig. 7 is a Link16 signal fuzzy function graph after sub-peak suppression processing, compared with the original fuzzy function graph of the Link16 signal, the method suppresses the serious sub-peak of the delay dimension and the doppler dimension, and solves the problem that a false target appears during target detection.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples described in this specification can be combined and combined by those skilled in the art.
While the present application has been described in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a review of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, apparatus (device), or computer program product. Accordingly, this application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "module" or "system. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. A computer program stored/distributed on a suitable medium supplied together with or as part of other hardware, may also take other distributed forms, such as via the Internet or other wired or wireless telecommunication systems.
The foregoing is a more detailed description of the invention in connection with specific preferred embodiments and it is not intended that the invention be limited to these specific details. For those skilled in the art to which the invention pertains, several simple deductions or substitutions can be made without departing from the spirit of the invention, and all shall be considered as belonging to the protection scope of the invention.

Claims (8)

1. A method for suppressing secondary peaks of Link16 signal external radiation source radar is applied to Link16 external radiation source radar, wherein an antenna is deployed in the external radiation source radar, and the antenna comprises a reference antenna and a receiving antenna, and the method comprises the following steps:
step 1: receiving a reference signal sent by a Link16 radiation source through the reference antenna, and receiving an echo signal reflected by a target through the receiving antenna;
step 2: preprocessing the reference signal and the echo signal to obtain a digital reference signal and a digital echo signal;
and step 3: solving to obtain a target neighborhood mismatched filter factor based on the digital reference signal;
and 4, step 4: according to the time slot structure of the Link16 signal, removing a jitter part and a transmission protection part in a target neighborhood mismatched filter factor corresponding to the reference signal, and removing the jitter part and the transmission protection part of the digital echo signal;
and 5: and performing two-dimensional coherent processing on the target neighborhood mismatched filter factor and the digital echo signal after the elimination processing to obtain a target fuzzy function.
2. The method of claim 1, wherein step 1 comprises:
step 1-1: receiving, by the reference antenna, a reference signal sent by a Link16 radiation source, where:
let T be the minimum FSK pulse repetition period of the Link16 signalpPulse width of TpdSymbol width of TB(ii) a The time slot length of the standard double-pulse packaging structure is TsJitter duration of TjEffective part length is TdTransmission guard duration of Tpr(ii) a The reference signal is denoted as s (t), and the received reference signal is:
Figure FDA0003192646700000011
wherein, t1＝nTs+Tj+iTp，t2＝nTs+Tj+Td+iTp+Tpd，fcCarrier frequency, Δ f, of the initial pulsen,iIndicating the offset of the carrier frequency, m, of the ith pulse of the nth time slot from the start pulsen,i(t) is a baseband complex envelope of the symbol of the ith pulse of the nth time slot after minimum frequency shift keying modulation;
m isn,i(t), expressed as:
Figure FDA0003192646700000021
wherein the content of the first and second substances,
Figure FDA0003192646700000022
and
Figure FDA0003192646700000023
representing the serial-to-parallel converted symbol, mn,2i-1＝mn,2i；
Step 1-2: receiving, by the receiving antenna, an echo signal reflected by a target, as:
Figure FDA0003192646700000024
wherein s isecho(t) represents the echo signal, α represents the amplitude factor, τ represents the time delay of the target, fdRepresenting the doppler frequency of the target.
3. The method of claim 1, wherein pre-processing the reference signal comprises:
step 2-11: amplifying the reference signal;
step 2-12: carrying out orthogonal down-conversion processing on the carrier frequency and the offset of the carrier frequency in the reference signal so as to eliminate the carrier frequency and the offset of the carrier frequency;
step 2-13: performing a/D sampling on the reference signal from which the carrier frequency and the offset of the carrier frequency are removed to obtain a digital reference signal, which is expressed as:
Figure FDA0003192646700000025
wherein, s [ l]Representing a digital reference signal, l representing the ith sample point,
Figure FDA0003192646700000026
l1＝(nTs+Tj+iTp)fs，l2＝(nTs+Tj+Td+iTp+Tpd)fs，fsis the sampling rate.
4. The method of claim 1, wherein preprocessing the echo signals comprises
Step 2-21: amplifying the echo signal;
step 2-22: carrying out orthogonal down-conversion processing on the carrier frequency and the offset of the carrier frequency in the echo signal so as to eliminate the carrier frequency and the offset of the carrier frequency;
step 2-23: and A/D sampling is carried out on the echo signal after the carrier frequency and the offset of the carrier frequency are eliminated, so as to obtain a digital echo signal, and the digital echo signal is expressed as:
Figure FDA0003192646700000031
wherein s isecho[l]For digital echo signals, the echo signal vector is secho＝[secho[1] secho[2]…secho[l-1]]T。
5. The method of claim 1, wherein step 3 comprises:
step 3-1: the digital reference signal is processed in segments, which is expressed as: sb[k]Wherein s isb[k]＝[s[k+bLB] s[k+1+bLB]…s[k+LB-1+bLB]]TB represents the total number of segments, and the length of the neighborhood mismatched filter factor of each segment is LBAnd satisfies the relationship L ═ BLBB represents the B-th section, and B is 1, 2 and 3 … B;
step 3-2: solving each segment of digital reference signals based on a neighborhood mismatch filtering optimal solution expression to obtain a neighborhood mismatch filtering factor corresponding to each segment of digital reference signals, wherein the neighborhood mismatch filtering optimal solution expression is expressed as:
Figure FDA0003192646700000032
wherein the content of the first and second substances,
Figure FDA0003192646700000033
Figure FDA0003192646700000034
is LBOrder identity matrix, wb＝[s[bLB] s[1+bLB]…s[LB-1+bLB]]T；
Step 3-3: splicing all the neighborhood mismatched filter factors to obtain a target neighborhood mismatched filter factor, which is expressed as:
Figure FDA0003192646700000041
6. the method according to claim 1, wherein the removing the jitter component and the transmission protection component in the target neighborhood mismatched filter factor corresponding to the reference signal comprises:
and 4-11: based on a preset first threshold value kappa, carrying out mismatch filtering on the target neighborhood by using a filter factor wmisThe nth time slot in the target neighborhood mismatched filter factor is subjected to pulse rising edge detection to determine the number l of points corresponding to the ith element larger than kappa in the target neighborhood mismatched filter factori,n＝1.2.3.4…；
And 4-12: calculating the point l corresponding to the ith element larger than kappaiNumber of points l corresponding to i +1 th element larger than ki+1The difference between, expressed as: li+1-li；
Step 4-13: analyzing the difference corresponding to the nth time slot, wherein when li+1-li＞TpfsWhen, determine li+1If the corresponding element does not belong to the current time slot, then wmis[l1],wmis[l1+1],wmis[l1+2],…,wmis[li]Assign values to w 'in order'misAnd w ismis[li+1],wmis[li+2]…, removing to realize the dithering part of the nth time slot in the target neighborhood mismatched filter factor corresponding to the reference signalRemoving the branch and transmission protection part;
and 4-14: and repeating the steps 4-11 to 4-14 until the jitter part and the transmission protection part of all time slots in the target neighborhood mismatched filter factor are eliminated.
7. The method according to claim 1, wherein the removing the jitter part and the transmission protection part of the digital echo signal comprises:
step 4-21: based on a preset second threshold value kechoFor said digital echo signal sechoPerforms pulse rising edge detection to determine that the jth of the digital echo signals is greater than kechoThe number of points l corresponding to the element(s)j，m＝1.2.3.4…；
And 4-22: calculate the jth > κechoThe number of points l corresponding to the element(s)jAnd j +1 th is greater than kappaechoThe number of points l corresponding to the element(s)j+1The difference between them, denoted as lj+1-lj；
And 4-23: analyzing the difference corresponding to the mth time slot, wherein when lj+1-lj＞TpfsWhen, determine lj+1If the corresponding element does not belong to the current time slot, s is setecho[l1],secho[l1+1],secho[l1+2],…,secho[lj]Assign values to s 'in order'echoAnd a isecho[lj+1]，secho[lj+2],., removing to remove the jittering part and the transmission protection part of the mth time slot in the digital echo signal;
and 4-24: and repeating the steps 4-21 to 4-24 until the jitter part and the transmission protection part of all time slots in the digital echo signal are eliminated.
8. The method of claim 1, wherein the two-dimensional coherent processing is performed on the rejected target neighborhood mismatched filter factor and the digital echo signal to obtain a target fuzzy function, which is expressed as:
Figure FDA0003192646700000051
wherein r ═ τ fsDenotes a distance delay unit, d ═ Lfd/fsRepresenting the doppler cell, | ψ (r, d) | representing the target blur function.
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