CN108880586B - A kind of broadband weak signal enhancement method and apparatus - Google Patents
A kind of broadband weak signal enhancement method and apparatus Download PDFInfo
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- CN108880586B CN108880586B CN201810689326.8A CN201810689326A CN108880586B CN 108880586 B CN108880586 B CN 108880586B CN 201810689326 A CN201810689326 A CN 201810689326A CN 108880586 B CN108880586 B CN 108880586B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
- H04B1/12—Neutralising, balancing, or compensation arrangements
- H04B1/123—Neutralising, balancing, or compensation arrangements using adaptive balancing or compensation means
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
- H04B7/0842—Weighted combining
- H04B7/086—Weighted combining using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
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Abstract
The present invention relates to a kind of broadband weak signal enhancement method and apparatus, using the space characteristics of broadband signal be equivalent to it is multiple it is adjacent come to narrow-band array signal, the delay vector of each signal is estimated using single source point, further acquire steering vector and interference plus noise covariance matrix of the signal on different frequency modulation points, the airspace filter to broadband desired signal is finally realized using narrow-band beam shaper, the undistorted output of echo signal is realized by multi-angle linear restriction, the enhancing to broadband signal is realized, purer no-manned machine distant control signal is obtained.The present invention effectively reduces system complexity and signal processing dimension, is more advantageous to engineering practice without using tapped delay line.In addition, the present invention is removed desired signal by constructing interference plus noise covariance matrix from original covariance matrix, to improve the robustness of Wave beam forming, and arithmetic speed is better than classical signal Enhancement Method.
Description
Technical field
The invention belongs to weak targets to enhance technical field, and in particular to a kind of broadband weak signal enhancement method and apparatus.
Background technique
In recent years, with the continuous development of stealth technology and frequency modulation technology, to the detection more difficult of Stealthy Target.Its
Main cause is that echo signal is very faint, the operations such as leads to subsequent feature extraction, test the speed, position can not effectively implement.Cause
This, needs to enhance echo signal, realizes that the broadband signal of multi-objective simultaneously enhances technology.
Based on the broadband adaptive beamforming technology of array can interference come to it is unknown under conditions of effectively enhance the phase
It hopes signal and inhibits interference and noise.Classical broad-band EDFA structure is the broadband Frost weak signal enhancement device, structure
As shown in Figure 1.It receives signal and first passes around pre-delay compensation module, compensate propagation delay of the desired signal between different array elements,
So that it is equivalent to 0 ° of direction incidence, is then followed by one group of tapped delay line in each array element, i.e., increases on the basis of Space domain sampling
Add time-domain sampling, the enhancing and interference signal of desired signal are realized finally by the weighting coefficient adjusted on different tapped delay lines
Inhibition.In the broadband Frost on the basis of weak signal enhancement device, it is adaptive that domestic and foreign scholars successively propose a variety of robust widebands
Answer beamforming algorithm, such as diagonal loading algorithm, worst best performance algorithm, constant beam-width algorithm.
Algorithm above is increased using the broadband weak signal based on tapped delay line (Tapped Delay-Lines, TDL)
Intensity device, other than TDL structure, author Ghavami has also been proposed a kind of based on array element delay line (Sensor Delay-
Lines, SDL) broadband weak signal enhancement device, structure as shown in Fig. 2, it utilize propagation delay generation of the signal between array element
For tapped delay, each array element only connects a weight coefficient, and most of beamforming algorithms based on TDL structure can be direct
Applied to the Beam-former based on SDL.Broad-band EDFA algorithm based on above two structure can be in complicated electromagnetism
Desired signal is proposed in environment, obtains good airspace filter effect.However they that there are system structures is complicated, computationally intensive
Problem, signal processing dimension rise to M × J dimension (M indicates that element number of array, J indicate delay line number), adaptive beam by M dimension
It is formed it is generally necessary to which carrying out matrix inversion or iteration, the increase of dimension will lead to calculation amount and steeply rise, to increase system fortune
It calculates burden, reduce operation efficiency.
Summary of the invention
The object of the present invention is to provide a kind of broadband weak signal enhancement method and apparatus, for solving existing broadband weak signal
The computationally intensive of Enhancement Method causes to increase the low problem of computational burden, operation efficiency.
In order to solve the above technical problems, the present invention proposes a kind of broadband weak signal enhancement method, comprising the following steps:
1) using the estimation incident angle compensation desired signal of desired signal in broadband signal in different antenna element
Propagation delay, obtaining incident angle after compensation on each bay is the broadband signal for setting incident angle；
2) by the equivalent superposition to the narrow-band array signal for forming incidence angles degree under same frequency of each broadband signal,
By the equivalent steering vector at narrow-band array signal in incident angle section of the steering vector of broadband signal, the incident angle section
For the angular interval of the incidence angles degree, the steering vector according to the narrow-band array signal in incident angle section is constructed
Narrow-band array signal model；
3) covariance matrix for calculating narrow-band array signal model, calculating incident angle is leading for the setting incident angle
To vector, weight vectors are calculated according to the covariance matrix and steering vector；
4) according to the broadband signal obtained after weight vectors and the compensation, the desired signal in broadband signal is determined.
The invention by it is a certain come to broadband array signal be equivalent to it is multiple it is adjacent come to narrow-band array believe
Number, by the equivalent steering vector at narrow-band array signal in setting incident angle section of the steering vector of broadband signal, accordingly structure
Narrow-band array signal model is built, and weight vectors are sought according to narrow-band array signal model, to realize broad-band EDFA, is dropped
Low operation dimension, calculation amount is small, operation efficiency is high.
In order to enhance the robustness of Wave beam forming, in step 3), when known to the incident angle of interference signal, according to interference
The incident angle of signal and the covariance matrix of narrow-band array signal model calculate the covariance matrix of interference signal, will be described dry
The covariance matrix for disturbing signal is added to obtain interference plus noise covariance matrix with the noise covariance matrix of estimation, according to interference
Weight vectors are calculated in plus noise covariance matrix and steering vector.
When the incident angle of interference signal is unknown, added according to the construction interference of the covariance matrix of narrow-band array signal model
Weight vectors are calculated according to interference plus noise covariance matrix and steering vector in noise covariance matrix, and the interference adds
The formula of noise covariance matrix is as follows:
In formula,For interference plus noise covariance matrix,For the covariance matrix of narrow-band array signal model
Inverse matrix,Come for interference and noise to section,For the incident angle of narrow-band array signal,Indicate that frequency is
fh, incident angle beNarrow-band array signal steering vector,ForAssociate matrix.
It is further limited as to weight vectors, the weight vectors are the guiding arrows according to the setting incident angle
Amount and the narrow-band array signal model covariance matrix or interference plus noise covariance matrix, and using minimum power without
Distortion response method obtains.
Alternatively, the weight vectors are the steering vector and the narrow-band array signal according to the setting incident angle
The covariance matrix or interference plus noise covariance matrix of model, and obtained using multi-angle constrained procedure.
It is further limited as to the undistorted response method of minimum power, utilizes the undistorted responder of the minimum power
Method seeks the formula of weight vectors are as follows:
In formula, w is weight vectors,For the covariance matrix of narrow-band array signal modelInverse matrix, a0To enter
Firing angle degree is the steering vector for setting incident angle.
It is further limited as to multi-angle constrained procedure, the formula of weight vectors w is sought using multi-angle constrained procedure
Are as follows:
In formula, w is weight vectors,For interference plus noise covariance matrixInverse matrix, C is constraint matrix, C
=[a (fh,-Δθ),a0,a(fh, Δ θ)], wherein a0It is the steering vector for setting incident angle, a (f for incident angleh,Δθ)
For the highest frequency f that frequency is the broadband signalh, incident angle be maximum estimated deviation steering vector, a (fh,-Δ θ) be
Frequency is the highest frequency f of the broadband signalh, incident angle be that maximum estimated deviation takes the steering vector of negative value, h is corresponding
Vector,
In order to which broadband signal to be equivalent to the superposition with the narrow-band array signal of identical frequency, incidence angles degree, walk
The equivalent formulation of rapid 2) the described broadband signal are as follows:
In formula,For the broadband signal of moment t,For in moment t, frequency fiOn narrow-band array signal, fi
∈[fl,fh] indicate frequency fiRange the broadband signal low-limit frequency flWith highest frequency fhBetween.
The narrow-band array signal model are as follows:
In formula,The narrow-band array signal of t at the time of being equivalent,For the incident angle area of narrow-band array signal
Between,For according to frequency fh, incident angleNarrow-band array signal in incident angle sectionSteering vector.
Further, the output signal formula of the broad-band EDFA are as follows:
In formula, y (t) is the output signal of the broad-band EDFA, wHFor weight vectors w,Described in carrying out
The broadband signal obtained after compensation.
In order to solve the above technical problems, the present invention also proposes a kind of broadband weak signal enhancement device, including it is compensating unit, narrow
Band array signal model construction unit, weight vectors computing unit and output unit, in which:
Compensating unit is used for the estimation incident angle compensating wide band signal using desired signal in broadband signal not on the same day
Propagation delay in linear array member, obtaining incident angle after compensation on each bay is the broadband signal for setting incident angle；
Narrow-band array signal model construction unit is used to enter each broadband signal is equivalent to forming difference under same frequency
The superposition of the narrow-band array signal of firing angle degree, by the steering vector of broadband signal it is equivalent at narrow-band array signal in incident angle area
Between steering vector, the incident angle section be the incidence angles degree angular interval, according to the narrow-band array signal
Steering vector in incident angle section constructs narrow-band array signal model；
Weight vectors computing unit is used to calculate the covariance matrix of narrow-band array signal model, and calculating incident angle is institute
The steering vector for stating setting incident angle calculates weight vectors according to the covariance matrix and steering vector；
Output unit is used to determine the phase in broadband signal according to the broadband signal obtained after weight vectors and the compensation
Hope signal.
Further, the weight vectors computing unit is also used to:
When known to the incident angle of interference signal, according to the incident angle of interference signal and narrow-band array signal model
Covariance matrix calculates the covariance matrix of interference signal, by the noise association side of the covariance matrix of the interference signal and estimation
Poor matrix is added to obtain interference plus noise covariance matrix, is calculated according to interference plus noise covariance matrix and steering vector
Weight vectors.
When the incident angle of interference signal is unknown, added according to the construction interference of the covariance matrix of narrow-band array signal model
Weight vectors are calculated according to interference plus noise covariance matrix and steering vector in noise covariance matrix, and the interference adds
The formula of noise covariance matrix is as follows:
In formula,For interference plus noise covariance matrix,For the covariance matrix of narrow-band array signal model
Inverse matrix,Come for interference and noise to section,For the incident angle of narrow-band array signal,Indicate that frequency is
fh, incident angle beNarrow-band array signal steering vector,ForAssociate matrix.
It is further limited as to weight vectors, the weight vectors are sought using two methods: according to the setting
The covariance matrix or interference plus noise covariance matrix of the steering vector of incident angle and the narrow-band array signal model,
And the weight vectors are obtained using the undistorted response method of minimum power；Alternatively, according to the guiding of the setting incident angle
The covariance matrix or interference plus noise covariance matrix of vector and the narrow-band array signal model, and about using multi-angle
Shu Fangfa obtains the weight vectors.
It is further limited as to the undistorted response method of minimum power, utilizes the undistorted responder of the minimum power
Method seeks the formula of weight vectors are as follows:
In formula, w is weight vectors,For the covariance matrix of narrow-band array signal modelInverse matrix, a0To enter
Firing angle degree is the steering vector for setting incident angle.
It is further limited as to multi-angle constrained procedure, the formula of weight vectors is sought using multi-angle constrained procedure
Are as follows:
In formula, w is weight vectors,For interference plus noise covariance matrixInverse matrix, C is constraint matrix, C
=[a (fh,-Δθ),a0,a(fh, Δ θ)], wherein a0It is the steering vector for setting incident angle, a (f for incident angleh,Δθ)
For the highest frequency f that frequency is the broadband signalh, incident angle be maximum estimated deviation steering vector, a (fh,-Δ θ) be
Frequency is the highest frequency f of the broadband signalh, incident angle be that maximum estimated deviation takes the steering vector of negative value, h is corresponding
Vector,
Further, the equivalent formulation of the broadband signal are as follows:
In formula,For the broadband signal of moment t,For in moment t, frequency fiOn narrow-band array signal, fi
∈[fl,fh] indicate frequency fiRange the broadband signal low-limit frequency flWith highest frequency fhBetween.
The narrow-band array signal model are as follows:
In formula,The narrow-band array signal of t at the time of being equivalent,For the incident angle area of narrow-band array signal
Between,For according to frequency fh, incident angleNarrow-band array signal in incident angle sectionSteering vector.
Further, the desired signal in broadband signal is determined by following formula:
In formula, y (t) is the desired signal in the broadband signal, wHFor the associate matrix of weight vectors w,For
Carry out the broadband signal obtained after the compensation.
Detailed description of the invention
Fig. 1 is the structural schematic diagram of the broadband TDL weak signal enhancement device in the prior art；
Fig. 2 is the structural schematic diagram of the broadband SDL weak signal enhancement device in the prior art；
Fig. 3 is a kind of flow chart of broadband weak signal enhancement method of the invention；
Fig. 4 is a kind of structural schematic diagram of broadband weak signal enhancement device without tapped delay line；
Fig. 5 is the array response schematic diagram under different frequency；
Fig. 6 is the spectrogram of output signal.
Specific embodiment
A specific embodiment of the invention is further described with reference to the accompanying drawing.
A kind of embodiment of broadband weak signal enhancement method of the invention:
Under far field condition, K broadband signal sk(t) (k=0,1 ..., K-1) be incident on be made of M (M >=K) array element and
On the uniform straight line array of delay line, wherein s0It (t) is desired signal, s1(t),s2(t),…,sK-1It (t) is interference signal.Then structure
The wideband array reception model for making no tapped delay line is as follows:
Wherein, x (t)=[x0(t),x1(t),...,xM-1(t)]T, xm(t) (m=0,1 ..., M-1) it is in m array element
Reception signal, ()TIndicate transposition.xk(t)=[sk(t),sk(t-τk,1),...,sk(t-τk,M-1)]TIt is signal sk(t)
Receive vector, τk,m=mdsin (θk)/c is sk(t) propagation delay when reaching array element m relative to reference array element, θk∈[-90°,
90 °] it is incident angle, d is adjacent array element spacing, and c is spread speed.N (t) is system noise vector.
Broadband signal sk(t) superposition of multiple narrow band signals can be equivalent to, it may be assumed that
Wherein,Indicate sk(t) in frequency fiOn narrow-band component, flAnd fhRespectively the low-limit frequency of signal and
Highest frequency.So sk(t) reception vector xk(t) it may be expressed as:
Wherein, a (fi,θk) it is in frequency fiOn steering vector.
In highest frequency fhOn, steering vector are as follows:
In low-limit frequency flOn, steering vector are as follows:
a(fl,θk) can be equivalent are as follows:
Wherein,It indicates equivalent incident angle, meetsObviouslyAnd θkIt is having the same
Positive negativity andSimilarly, for optional frequency fiOn steering vector a (fi,θk) to can be equivalent to frequency be fh
Incident angle isSteering vector MeetAnd(it is assumed that
θk>=0 °, if θk≤ 0 °,).It willIt is denoted as Θk, then formula (3) can transform to:
For formula (7), Wave beam forming mainly utilizes the space characteristics of signal, i.e. steering vector In
Frequency fiOn Wave beam forming without influence, because it has been embodied in the effect of steering vectorTherefore, in the mistake of Wave beam forming
Cheng Zhong, it is believed that all narrow-band component equivalent frequencies having the same, but there is different incident angles.Contrast (3) and formula
(7), can obtain and such as draw a conclusion: a frequency range is [fl,fh] incident angle is θkBroadband array signal can be equivalent to multiple frequencies
Rate is fhIncident angle section is ΘkNarrow-band array signal.So, inhibit a broadband interference to be also just equivalent to and inhibit multiple
The narrowband of adjacent angular interferes, then realizes using narrow-band beam shaper.
In narrowband self-adaption Wave beam forming, weight vectors w can be by according to setting incident angle θ0Steering vector with
And the covariance matrix or interference plus noise covariance matrix of narrow-band array signal model obtain, minimum power is undistorted response
The model of method (Minimum Power Distortionless Response, MPDR) are as follows:
Its solution is
Wherein, Rx=E [x (t) xHIt (t)] is covariance matrix, a (θ0) be desired signal steering vector.Weight vectors w
Desired signal can effectively be enhanced and inhibit steering vector different from a (θ0) interference signal.However, formula (9) not can be used directly in
Broad-band EDFA, because of broadband desired signal s0(t) steering vector a (θ0) change as frequency is different.If by some
Frequency fiOn steering vector a (θ0,fi) formula (9) are substituted into, the weight vectors acquired are only capable of enhancing narrow-band componentAnd its
His narrow-band component will be treated as AF panel and fall.
For this purpose, the present invention takes common pre-delay compensation technology, i.e., a delay cell is added after each array element,
Setting value is followed successively by 0 ,-τ0,1,...,-τ0,M-1, for compensating propagation delay of the desired signal in different array elements, believe expectation
Arrival time number in different array elements is identical, is equivalent to be transformed toIncident direction on,Indicate predelay
Desired signal after compensationIncident angle.So have for optional frequency fBy a0=
[1,1,...,1]TSubstitution formula (9) can obtain:
Wherein,To sample obtained covariance matrix, After pre-delay compensation
It receives signal phasor (i.e. compensated broadband signal),For the covariance matrix of narrow-band array signal modelInverse square
Battle array, a0It is setting incident angle for incident angleSteering vector.The w acquired by above formula can effectively enhanceAll frequencies
The output signal of rate component, Wave beam forming isThe structure of broadband weak signal enhancement device of the invention is as schemed
Shown in 4.
As desired signal incident angle θ0And covariance matrixWhen accurately known, the above method can get preferable output
Performance.But in practice, due to the limitation of angle measurement accuracy and number of snapshots, θ0WithOften there is certain deviation, leads to wave beam
Shaper accidentally falls desired signal as AF panel, so that the sharply decline of output performance.In order to enhance Beam-former
Robustness, a kind of effective method are to remove desired signal from covariance matrix, i.e. reconstruct interference-plus-noise covariance square
Battle array.The existing beamforming algorithm based on interference plus noise covariance matrix reconstruct is mostly directed to narrow band signal, needle of the present invention
To the broadband weak signal enhancement device shown in Fig. 4 without tapped delay line.
After pre-delay compensationThe equivalent incident angle section of reception vector sum remember respectively
ForWithAccording to formula (7), have:
Covariance matrix is defined as:
Formula (11) are substituted into formula (12), can be obtained:
Wherein,Expression pairTake conjugation.Due to irrelevant between different narrow-band components, i.e.,Above formula can simplify are as follows:
Wherein,It indicatesPower.It is acquired using following formula:
Formula (15) are substituted into formula (14), can be obtained:
When the incident angle of all interference signals is accurately known, the association of the restructural each interference signal out of formula (16) is utilized
Variance matrix calculates interference signal according to the covariance matrix of the incident angle of interference signal and narrow-band array signal model
Covariance matrix；The interference covariance matrix acquired is added with the noise covariance matrix of estimation again, which can reconstruct interference, adds
Noise covariance matrix.
But under normal conditions, the incident angle of interference signal is unknown, in this case, according to narrow-band array signal mode
The covariance matrix of type constructs interference plus noise covariance matrix, is calculated according to interference plus noise covariance matrix and steering vector
Weight vectors are obtained, interference plus noise covariance matrix can be reconstructed by following formula:
Wherein,For interference plus noise covariance matrix,For the covariance matrix of narrow-band array signal model
Inverse matrix,For the incident angle of narrow-band array signal,Come for interference and noise to section,Δ θ indicates the maximum estimated deviation of desired signal incident angle,It indicates
Frequency is fh, incident angle beNarrow-band array signal steering vector,ForConjugate transposition
Matrix.It utilizesIn substituted (10)The weight vectors with strong robustness can be acquired:
The present invention interference signal come to unknown condition under merely with narrowband Capon spectrum can structural wideband interference plus make an uproar
Sound covariance matrix.
But when there are angular error, the weight vectors that the above method acquires cannot keep frequency invariance, so as to cause
Output signal distortion.It, can be further using polygonal in order to realize there are desired signal is exported under the conditions of angular error without distortions
It spends linear restriction method and forms the corresponding multi-angle linear restriction of flat-top, i.e., it is multiple to be arranged in neighbouring angle in desired signal
Corresponding constraint, it may be assumed that
Wherein,For corresponding vector, angle () expression is taken
Phase, w are weight vectors,For interference plus noise covariance matrixInverse matrix, C is constraint matrix, C=[a
(fh,-Δθ),a0,a(fh, Δ θ)], wherein a0It is the steering vector for setting incident angle, a (f for incident angleh, Δ θ) and it is frequency
Rate is the highest frequency f of broadband signalh, incident angle be maximum estimated deviation steering vector, a (fh,-Δ θ) it be frequency is wide
The highest frequency f of band signalh, incident angle be that maximum estimated deviation takes the steering vector of negative value.Utilize Language multiplier method
(i.e. LCMV method) solves formula (19), can obtain weight vectors finally are as follows:
The present invention is corresponding using the flat-top that multi-angle linear restriction realizes main lobe wave beam, to effectively prevent due to frequency
Distorted signals caused by rate inconsistency realizes airspace filter, achievees the purpose that enhancing it is expected and inhibits interference and noise.
Process of the invention can be summarized as follows:
1) broadband signal s is utilizedk(t) desired signal s in0(t) estimation incident angle(There may be deviations) it mends
Repay desired signal s0(t) propagation delay in different antenna element, obtaining incident angle on each bay after compensation is
Set incident angle θ0Broadband signalBroadband signalIn include compensated desired signal
2) by each broadband signalIt is equivalent to arrive frequency fhThe lower narrow-band array signal for forming incidence angles degree is folded
Add, the equivalent formulation of broadband signal are as follows:
In formula,For the broadband signal of moment t,For in moment t, frequency fiOn narrow-band array signal, fi
∈[fl,fh] indicate frequency fiRange broadband signal low-limit frequency flWith highest frequency fhBetween.
By the steering vector a (f of broadband signali,θk) it is equivalent at narrow-band array signal in incident angle sectionGuiding
VectorThe incident angle sectionFor the angular interval of incidence angles degree, according to narrow-band array signal in incidence
The steering vector of angular interval constructs narrow-band array signal model, narrow-band array signal model are as follows:
In formula,The narrow-band array signal of t at the time of being equivalent,For the incident angle area of narrow-band array signal
Between,For according to frequency fh, incident angleNarrow-band array signal in incident angle sectionSteering vector.
3) covariance matrix of narrow-band array signal model is calculatedCalculating incident angle is setting incident angle θ0's
Steering vector a0, interference-plus-noise covariance square is constructed using the undistorted response method of minimum power or multi-angle constrained procedure
Battle array, and seek weight vectors w.
4) according to the broadband signal obtained after weight vectors w and compensationDetermine the desired signal y in broadband signal
(t)。
Compared to traditional broadband weak signal enhancement device, the structure of broadband weak signal enhancement device of the invention is simple, multiple
Miscellaneous degree is low, and the calculation amount of data processing is small, and still can get preferable output under conditions of angular error and limited sampling point
Performance.
It in order to prove effectiveness of the invention, can be verified by following emulation time delays, it is assumed that array is that 16 array elements are uniform
Line array, three linear FM signal s0、s1、s2The array is incident on from 10 °, -20 °, 40 ° of directions respectively.Wherein s0It is expectation
Signal, signal-to-noise ratio 0dB.s1And s2It is interference signal, it is dry to make an uproar than being 20dB.The frequency range of three be respectively [2.9,
3.95] GHz, [3,4] GHz and [3.1,4] GHz.Reference frequency selects fmax=4GHz.Adjacent array element spacing is Δ d=0.5
λmin, wherein λminFor highest frequency fmaxCorresponding wavelength.Sample rate is 2fmax, number of snapshots 200.Desired signal incident angle
Maximum possible deviation be set as Δ θ=5 °.The estimated value of desired signal incident angle isThere is 3 ° of deviation.
It utilizesAfter carrying out pre-delay compensation, s0、s1And s2Incident angle become -2.94 °, -34.54 ° and 24.7 °.Figure
5 give the array response under different frequency, as seen from the figure each wave beam interference come be upwardly formed null and [- 5 °,
5 °] to form flat-top in range corresponding, illustrate that Beam-former can effectively inhibit interference signal, and output expectation without distortions
Signal.Fig. 6 gives the spectrogram of output signal, it can be seen that under conditions of angular error, strong jamming and low signal-to-noise ratio, this
The method of invention can still recover desired signal without distortions.
The invention firstly uses the space characteristics of broadband signal be equivalent to it is multiple it is adjacent come to narrow-band array signal,
The delay vector of each signal is estimated using single source point, and further acquires steering vector of the desired signal on different frequency modulation points
And interference plus noise covariance matrix, the airspace filter to broadband desired signal finally is realized using narrow-band beam shaper, is led to
The undistorted output of echo signal is realized in excessive angle linear restriction, to realize effective broad-band EDFA, is realized pair
The enhancing of broadband signal obtains purer no-manned machine distant control signal.Wideband array different from the past enhances technology, the present invention
Without using tapped delay line, system complexity and signal processing dimension are effectively reduced, engineering practice is more advantageous to.In addition,
The present invention is removed desired signal by constructing interference plus noise covariance matrix from original covariance matrix, to improve wave
The robustness that beam is formed, and arithmetic speed is better than classical signal Enhancement Method.
Corresponding above-mentioned broadband weak signal enhancement method, the present invention also propose a kind of broadband weak signal enhancement device, the broadband
Weak signal enhancement device includes that compensating unit, narrow-band array signal model construction unit, weight vectors computing unit and output are single
Member, in which:
Compensating unit is used for the estimation incident angle compensating wide band signal using desired signal in broadband signal not on the same day
Propagation delay in linear array member, obtaining incident angle after compensation on each bay is the broadband signal for setting incident angle.
Narrow-band array signal model construction unit is used to enter each broadband signal is equivalent to forming difference under same frequency
The superposition of the narrow-band array signal of firing angle degree, by the steering vector of broadband signal it is equivalent at narrow-band array signal in incident angle area
Between steering vector, the incident angle section be incidence angles degree angular interval, according to narrow-band array signal in incidence angle
The steering vector for spending section constructs narrow-band array signal model.
Weight vectors computing unit is used to calculate the covariance matrix of narrow-band array signal model, and calculating incident angle is to set
The steering vector for determining incident angle calculates weight vectors according to covariance matrix and steering vector；Output unit is used for basis and adds
The broadband signal obtained after weight vector and compensation, determines the desired signal in broadband signal.
The above description is only a preferred embodiment of the present invention, is not intended to restrict the invention, for those skilled in the art
For member, the invention may be variously modified and varied.All within the spirits and principles of the present invention, it is made it is any modification,
Equivalent replacement, improvement etc., should be included within scope of the presently claimed invention.
Claims (12)
1. a kind of broadband weak signal enhancement method, which comprises the following steps:
1) propagation using the estimation incident angle compensation desired signal of desired signal in broadband signal in different antenna element
Time delay, obtaining incident angle after compensation on each bay is the broadband signal for setting incident angle；
It 2), will be wide by the equivalent superposition to the narrow-band array signal of formation incidence angles degree under same frequency of each broadband signal
The equivalent steering vector at narrow-band array signal in incident angle section of the steering vector of band signal, the incident angle section are institute
The angular interval for stating incidence angles degree, the steering vector according to the narrow-band array signal in incident angle section construct narrowband
Array signal model；
3) covariance matrix for calculating narrow-band array signal model calculates the guiding arrow that incident angle is the setting incident angle
Amount calculates weight vectors according to the covariance matrix and steering vector；The weight vectors are according to the setting incidence angle
The covariance matrix or interference plus noise covariance matrix of the steering vector of degree and the narrow-band array signal model, and utilize
Multi-angle constrained procedure obtains；The formula of weight vectors is sought using multi-angle constrained procedure are as follows:
In formula, w is weight vectors,For interference plus noise covariance matrixInverse matrix, C is constraint matrix, C=[a
(fh,-Δθ),a0,a(fh, Δ θ)], wherein a0It is the steering vector for setting incident angle, a (f for incident angleh, Δ θ) and it is frequency
Rate is the highest frequency f of the broadband signalh, incident angle be maximum estimated deviation steering vector, a (fh,-Δ θ) it is frequency
For the highest frequency f of the broadband signalh, incident angle be that maximum estimated deviation takes the steering vector of negative value, h be accordingly to
Amount,
4) according to the broadband signal obtained after weight vectors and the compensation, the desired signal in broadband signal is determined.
2. weak signal enhancement method in broadband according to claim 1, which is characterized in that in step 3), when interference signal
When known to incident angle, interference letter is calculated according to the covariance matrix of the incident angle of interference signal and narrow-band array signal model
Number covariance matrix, the covariance matrix of the interference signal is added with the noise covariance matrix of estimation obtain interference plus
Weight vectors are calculated according to interference plus noise covariance matrix and steering vector in noise covariance matrix.
3. weak signal enhancement method in broadband according to claim 1, which is characterized in that in step 3), when interference signal
When incident angle is unknown, interference plus noise covariance matrix is constructed according to the covariance matrix of narrow-band array signal model, according to
Weight vectors, the formula of the interference plus noise covariance matrix is calculated in interference plus noise covariance matrix and steering vector
It is as follows:
In formula,For interference plus noise covariance matrix,For the covariance matrix of narrow-band array signal modelIt is inverse
Matrix,Come for interference and noise to section,For the incident angle of narrow-band array signal,Expression frequency is fh、
Incident angle isNarrow-band array signal steering vector,ForAssociate matrix.
4. weak signal enhancement method in broadband according to claim 1, which is characterized in that the step 2) broadband signal etc.
Imitate formula are as follows:
In formula,For the broadband signal of moment t,For in moment t, frequency fiOn narrow-band array signal, fi∈
[fl,fh] indicate frequency fiRange the broadband signal low-limit frequency flWith highest frequency fhBetween.
5. weak signal enhancement method in broadband according to claim 4, which is characterized in that the narrow-band array signal model
Are as follows:
In formula,The narrow-band array signal of t at the time of being equivalent,For the incident angle section of narrow-band array signal,For according to frequency fh, incident angleNarrow-band array signal in incident angle sectionSteering vector.
6. weak signal enhancement method in broadband according to claim 1, which is characterized in that determine that broadband is believed by following formula
Desired signal in number:
In formula, y (t) is the desired signal in the broadband signal, wHFor the associate matrix of weight vectors w,To carry out
The broadband signal obtained after the compensation.
7. a kind of broadband weak signal enhancement device, which is characterized in that single including compensating unit, the building of narrow-band array signal model
Member, weight vectors computing unit and output unit, in which:
Compensating unit is used for the estimation incident angle compensating wide band signal using desired signal in broadband signal in different antennae battle array
Propagation delay in member, obtaining incident angle after compensation on each bay is the broadband signal for setting incident angle；
Narrow-band array signal model construction unit is used for each broadband signal is equivalent to forming different incidence angles under same frequency
The superposition of the narrow-band array signal of degree, by the steering vector of broadband signal it is equivalent at narrow-band array signal in incident angle section
Steering vector, the incident angle section are the angular interval of the incidence angles degree, are being entered according to the narrow-band array signal
Penetrate the steering vector building narrow-band array signal model of angular interval；
Weight vectors computing unit is used to calculate the covariance matrix of narrow-band array signal model, and calculating incident angle is described set
The steering vector for determining incident angle calculates weight vectors according to the covariance matrix and steering vector；The weight vectors are
According to the covariance matrix or interference of the steering vector of the setting incident angle and the narrow-band array signal model plus make an uproar
Sound covariance matrix, and obtained using multi-angle constrained procedure；The formula of weight vectors is sought using multi-angle constrained procedure are as follows:
In formula, w is weight vectors,For interference plus noise covariance matrixInverse matrix, C is constraint matrix, C=[a
(fh,-Δθ),a0,a(fh, Δ θ)], wherein a0It is the steering vector for setting incident angle, a (f for incident angleh, Δ θ) and it is frequency
Rate is the highest frequency f of the broadband signalh, incident angle be maximum estimated deviation steering vector, a (fh,-Δ θ) it is frequency
For the highest frequency f of the broadband signalh, incident angle be that maximum estimated deviation takes the steering vector of negative value, h be accordingly to
Amount,
Output unit is used to determine the expectation letter in broadband signal after weight vectors and the compensation according to the broadband signal obtained
Number.
8. weak signal enhancement device in broadband according to claim 7, which is characterized in that the weight vectors computing unit is also
For: when known to the incident angle of interference signal, according to the association of the incident angle of interference signal and narrow-band array signal model
Variance matrix calculates the covariance matrix of interference signal, by the noise covariance of the covariance matrix of the interference signal and estimation
Matrix is added to obtain interference plus noise covariance matrix, is calculated and is added according to interference plus noise covariance matrix and steering vector
Weight vector.
9. weak signal enhancement device in broadband according to claim 7, which is characterized in that the weight vectors computing unit is also
For: when the incident angle of interference signal is unknown, according to the interference of the covariance matrix of narrow-band array signal model construction plus make an uproar
Weight vectors are calculated according to interference plus noise covariance matrix and steering vector in sound covariance matrix, and the interference, which adds, makes an uproar
The formula of sound covariance matrix is as follows:
In formula,For interference plus noise covariance matrix,For the covariance matrix of narrow-band array signal modelIt is inverse
Matrix,Come for interference and noise to section,For the incident angle of narrow-band array signal,Expression frequency is fh、
Incident angle isNarrow-band array signal steering vector,ForAssociate matrix.
10. weak signal enhancement device in broadband according to claim 7, which is characterized in that the equivalent public affairs of the broadband signal
Formula are as follows:
In formula,For the broadband signal of moment t,For in moment t, frequency fiOn narrow-band array signal, fi∈
[fl,fh] indicate frequency fiRange the broadband signal low-limit frequency flWith highest frequency fhBetween.
11. weak signal enhancement device in broadband according to claim 10, which is characterized in that the narrow-band array signal model
Are as follows:
In formula,The narrow-band array signal of t at the time of being equivalent,For the incident angle section of narrow-band array signal,For according to frequency fh, incident angleNarrow-band array signal in incident angle sectionSteering vector.
12. weak signal enhancement device in broadband according to claim 7, which is characterized in that determine broadband by following formula
Desired signal in signal:
In formula, y (t) is the desired signal in the broadband signal, wHFor the associate matrix of weight vectors w,To carry out
The broadband signal obtained after the compensation.
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