CN101212259A - Fractional Fourier transform and fuzzy transform based primary function optimization design method for transform domain under complex interference - Google Patents

Fractional Fourier transform and fuzzy transform based primary function optimization design method for transform domain under complex interference Download PDF

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CN101212259A
CN101212259A CNA2006100227256A CN200610022725A CN101212259A CN 101212259 A CN101212259 A CN 101212259A CN A2006100227256 A CNA2006100227256 A CN A2006100227256A CN 200610022725 A CN200610022725 A CN 200610022725A CN 101212259 A CN101212259 A CN 101212259A
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interference
function
subbase
frft
basic function
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王传丹
张忠培
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University of Electronic Science and Technology of China
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Abstract

The invention discloses a method for optimizing and designing a basis function in a transform field communication system based on a RAT+FRFT, which belongs to a wireless communication technology field and relates to a signal design technology in recognition wireless technology. The method can realize the following objects: 1. the precise estimate of environmental disturbance is realized by adopting a successive estimation method of environmental disturbance based on the RAT+FRFT; 2. a subbasis function mutually crossing with every interference components is generated by adopting the precise estimate based on the environmental disturbance parameter and a disturbance spectrum in the basis function is eliminated through the method that a system basis function is generated by cascading with the subbasis function; 3. the bandwidth of the generated basis function and disturbance elimination are optimized to the best by adopting the method of basis function bandwidth optimization and disturbance elimination optimization. The basis function generated by adopting the method ensures that the transform field communication system has good disturbance resistance performance and environmental adoptability.

Description

Under the complicated disturbance based on the Optimization Design of the transform domain communication system basic function of fractional Fourier transform and blurring mapping
Technical field
The invention belongs to wireless communication technology field, particularly basic function (BF) optimal design method in the transform domain communication system (TDCS).
Background technology
TDCS is a kind of New Anti-interference that proposes in recent years, the anti-system of intercepting and capturing.By unite emission, receive the modelled signal waveform, the mode of thoroughly eliminating interference spectrum from signal constitutes realizes anti-interference.TDCS has good anti-interference, the anti-performance of intercepting and capturing.The Waveform Design that transmits in the TDCS system is the key of decision systems performance, directly has influence on anti-interference, the anti-performance of intercepting and capturing of system.The waveform that transmits is by system's basic function decision.Research to system's basic function is one of TDCS key technology.
Summary of the invention
The present invention proposes the TDCS basic function Optimization Design under steady, non-stationary complex environment disturb, adopt this method can make the basic function of design obtain best interference rejecting, optimal working bandwidth.Thereby make basic function have the ability of best anti-environmental interference.
Innovation part of the present invention is: propose to have realized the accurate estimation of transform domain communication system environmental interference based on the environmental interference of blurring mapping+Fourier transform (RAT+FRFT) at random method of estimation one by one; Proposition is based on the accurate estimation of environmental interference parameter, produces and each interference components the subbase function, the method by subbase function cascaded generation system basic function of quadrature mutually.Reject the disturbance spectrum in the basic function; Propose the basic function bandwidth optimization and disturb the method for optimizing of rejecting. make the basic function bandwidth of generation and interference reject best.The basic function that adopts this method to generate makes transform domain communication system have good interference free performance and environmental suitability.
The subbase function, method and the basic function bandwidth optimization that produces system's basic function by the subbase function cascaded of quadrature are formed with interference rejecting optimization method two parts mutually with each interference components by producing in the present invention.
The present invention proposes to produce the subbase function that disturbs quadrature with each linear frequency modulation class based on the environmental interference of RAT+FRFT method of estimation one by one on the basis of TDCS system configuration; Again the environment spectrum of rejecting after the linear frequency modulation class is disturbed is carried out residual interference rejecting optimization: with each subbase function cascaded, obtain system's basic function at last.
1, system configuration
The TDCS system configuration as shown in Figure 1.If during transmitter, synchronous working consistent, finish estimation simultaneously to environmental interference with the operation of receiver environment, obtain identical environment spectrum and estimate sa (t), adopt identical BF generation method just, get the identical BF of sword.B (t) and b (t) are the time-domain representation of BF, conjugation each other.B (u)) and B *(u) be the frequency domain representation of BF, conjugation each other.D (f) is the pick of emission number.S (t) is transmitting behind the BF modulating data.R (t) is a received signal, Be to receive the data valuation, produce by the relevant output of r (t) with local basic function b (t).In the basic function b (t) that is produced, do not comprise environmental interference spectrum composition, i.e. environmental interference and transmission signal in orthogonal.Environmental interference does not exert an influence to the transmission of signal.
2, the generation of basic function
BF determines to transmit waveform and system's interference free performance.System is had a very important role.Environment estimation and BF amplitude generating principle are as shown in Figure 2.
Estimate among the SA (u), in the environment spectrum that obtains with thresholding A TThe amplitude A ' that relatively obtains B (u) (u) surpasses A TThe time put 0, be lower than A TThe time put 1, obtain the basic function B (u) of frequency spectrum and disturbance spectrum quadrature:
Figure A20061002272500051
U is a transform domain, can be frequency domain, score field, wavelet field etc.
Phase place Produce by the random phase reflection method, make B (u) the time-domain representation b (t) of generation have the noise similitude, to improve the anti-interception capability and the reliability of communicating by letter of TDCS.
In the ideal case, environmental interference can estimate accurately all and be to reject fully that therefore, TDCS has good anti-interference from BF.But in fact, environmental interference has diversity, character, the size of interference signal have uncertainty, so, it is impossible will rejecting the environmental interference spectrum fully, make TDCS systematic function the best, must reject the interference component among the BF as far as possible, make BF have the best resistivity that non-rejecting is disturbed simultaneously.
3, optimal base function designing requirement
For making the systematic function optimum, the error rate should be low as far as possible, and basic function should meet the following conditions:
(1) rejecting interference should be more little and few more good more;
(2) the frequency spectrum B of B (u) BFYing Yuekuan is good more.
4, the interference during basic function generates is rejected and bandwidth optimization one by one
According to 3 as can be known, the design of BF should make that the environmental interference spectrum that is comprised is minimum, require contained non-zero bandwidth the wideest simultaneously.Therefore, the present invention considers the optimal design of BF, the i.e. maximization of thorough rejecting of Gan Raoing and BF non-zero bandwidth from two aspects.
(1) disturb rejecting and basic function to generate
The present invention mainly considers following several interference: steadily typical and non-stationary interference such as single-tone, single linear frequency modulation, polyteny frequency modulation.
The present invention adopts the RAT+FRFT conversion, environment sampling sa (t) is carried out iteration Interference Estimation, elimination, and can avoid the screening effect of strong jamming to weak jamming.The generation method of among the present invention the generation of corresponding subbase function and system's basic function are estimated, respectively disturbed to environmental interference is as shown in Figure 3:
As seen from Figure 3, environment sampling sa (t) obtains linear frequency modulation class non-stationary and disturbs J through the RAT conversion iTranslation-angle α J(i) and amplitude A J(i).For avoiding the screening effect of strong jamming, according to A to weak jamming J(i) descending, with α J(i) for angle of transformation sa (t) is carried out the FRFT conversion one by one, obtain SA i(u) and disturb J iAt the relevant position in u territory u (i); According to the estimated result that obtains, only considering J iUnder the prerequisite of rejecting, the requirement according to the generation of basic function " 2, " generates and J iCorresponding subbase function B i(u), and by below the method for the BF bandwidth optimization introduced being optimized.B i(u) after the IFRFT conversion, obtain corresponding time-domain representation b i(t); Through interference eliminated, SA i(u) eliminate J in i, through the IFRFT conversion, obtain sa ' (t) again, upgrade translation-angle α=α J(i+1), sa ' (t) is carried out FRFT again, disturb J to finish next I+1Parameter Estimation; Using such method according to disturbing by strong to weak order, obtains parameter of each interference one by one and generates corresponding time domain subbase function b i(t); b i(t) obtain the time domain basic function b (t) of system after the cascade:
b ( t ) = b 1 ( t ) ⊗ b 2 ( t ) ⊗ . . . b N Jm ( t )
Be that system's basic function is each J iThe convolution of corresponding subbase function.Because b i(t) and J iQuadrature, thus b (t) and J guaranteed i(i=1 ..., N Jm) orthogonality.
Is the data-modulated waveform at transmitting terminal with b (t), and adopting its conjugate form b (t) at receiving terminal is local correlation function.
(2) disturb rejecting to optimize and the basic function bandwidth optimization
In generate corresponding sub-BF process by estimated parameter, can realize disturbing rejecting and optimize and sub-BF bandwidth optimization, the method that the present invention adopts is as follows.Set thresholding, can determine disallowable interference and corresponding sub-BF, and can further reject and disturb according to following method, the adjustment that iterates can obtain disturbing best rejecting and sub-BF optimum bandwidth.
Between average noise power density and interference peak power, initial threshold A is set T, with Δ A TBe step-length, reduce thresholding, Δ A TChoose no specific (special) requirements, its size is relevant with number of times and precision of thresholding adjustment.New thresholding A ' T=A T-Δ A T, as shown in Figure 4, and whether finish by the adjustment of following conditional decision thresholding.
Before reducing decision threshold, the power spectral density W of noise+interference 1For:
W 1＝(N 0B BF1+J u+A T)/B BF1＝N 0+(J u+A T)/B BF1 (2)
B wherein BF1Be the sub-BF bandwidth before thresholding reduces, J uBe not reject interference, or remove J iEquivalence is in addition disturbed, N 0It is Carrier To Noise Power Density.
After reducing decision threshold, the power spectral density W of noise+interference 2For:
W 2＝(N 0B BF2+J u)/B BF2＝N 0+J u/B BF2 (3)
Be after thresholding reduces, A TWith A ' TBetween interference disallowable, subbase function bandwidth becomes B BF2=B BF1-Δ B J (i)=B BF1-(B ' J (i)-B J (i)), B J (i)And B ' J (i)Be respectively J iAt thresholding A TAnd A ' TUnder bandwidth, Δ B J (i)Be J before and after thresholding changes iThe variation of shared frequency bandwidth.Better for making thresholding reduce the back systematic function, must satisfy:
W 1＞W 2 (4)
The power spectral density that is the noise+interference after thresholding reduces must also promptly must satisfy less than the power spectral density of the noise+interference before the thresholding reduction:
A T/ΔB J(i)＞J u/B BF2 (5)
Therefore, require the power spectral density of disallowable interference just can reach by adjusting the purpose that thresholding improves systematic function greater than rejecting the equivalent power spectrum density of back residual interference in subbase function band.
If condition (5) satisfies, then the thresholding adjustment is effective, further reduces thresholding again, carries out new iteration adjustment, when condition does not satisfy till, thereby obtain rejecting and the subbase function of optimum bandwidth corresponding to the Optimal Jamming of this disallowable interference.
By this method, can optimize each one by one and disturb rejecting and corresponding subbase function bandwidth.
Sample sa ' (t) to finishing the environment that disturbs after pursuing-rejecting, can further optimize, reject non-chirp class and disturb by similar approach.As sa ' (t) is carried out the FRFT conversion of suitable angle, the spectrum that obtains is as shown in Figure 5 estimated:
J uBe the interference in signal when transmission or remove J iEquivalent residual interference in addition, J iBe that interference threshold is by A TReduce to A ' TThe interference that Shi Keneng eliminates, bandwidth is B J (i)Bandwidth corresponding before and after thresholding reduces is respectively B BF1, B BF2Can get with identical principle, meet the following conditions, then can reduce thresholding, reject and disturb J i:
J i/B J(i)＞J u/B BF2 (6)
Again by step delta A TFurther reduce thresholding, carry out new iteration adjustment, when condition does not satisfy till, obtain disturbing and reject best and bandwidth optimum, generate corresponding subbase function b R(n).Subbase function after residual interference rejected corresponding subbase function cascade during with each interference components rejecting obtains system's basic function:
b S ( t ) = b ( t ) ⊗ b R ( t ) = b 1 ( t ) ⊗ b 2 ( t ) ⊗ . . . ⊗ b N Jm ( t ) ⊗ b R ( t )
Advantage of the present invention:
(1) adopt RAT+FRFT can realize estimation fast and accurately, rejecting that the linear frequency modulation class is disturbed;
(2) basic function frequency band optimization is rejected, made to the best that can realize non-linear class frequency modulation interference;
(3) by the subbase function cascaded, can obtain the optimizer system basic function.
Description of drawings
Fig. 1 TDCS system configuration
The estimation of Fig. 2 environment spectrum is determined with the basic function amplitude
Fig. 3 system basic function generation method
Fig. 4 disturbs subbase function bandwidth optimization when rejecting one by one
Fig. 5 Chirp disturbs the residual interference after rejecting one by one to reject optimization.

Claims (5)

  1. Environment based on blurring mapping+fractional Fourier transform (RAT+FRFT) estimate in disturbing one by one, produce with each interference components mutually quadrature the subbase function, produce the method for system's basic function by the subbase function cascaded, it is characterized in that described basic function generates and comprises the steps:
    Step 1: Interference Estimation and subbase function generate
    The environmental interference estimation principle is referring to Figure of description 1,2,3,4,5.Specifically comprise the steps:
    The first step: environmental interference sampling.Transmitting-receiving two-end is sampled to the environmental interference signal respectively, obtains environment sampling sa (t).
    Second step: the calculating of interference signal translation-angle.Adopt RAT to estimate the optimal mapping angle [alpha] of different interference signals i, i=1 ..., N Jm(i is the interference signal sequence number, N JmBe the interference signal number), make interference signal concentration of energy degree under the different translation-angles in transform domain the highest, it is the narrowest to take scope.
    The 3rd step: the FRFT conversion of environment sampling.By being sampled, environment carries out translation-angle α iThe FRFT conversion, obtain the conversion SA (u) in the score field u, make interference components present the concentration of energy state at its transform domain.
    The 4th step: the generation of interference components bandwidth optimization and decision threshold.According to the bandwidth optimization requirement, determine scope and the corresponding decision threshold A of interference components in transform domain T
    The 5th step: interference components frequency spectrum mark.The FRFT conversion SA (u) that the 3rd step was produced goes on foot the threshold value A that produces with the 4th TRelatively, surpass threshold value A TComponent be set to 0, other component is set at 1, generates corresponding subbase spectrum of function amplitude sequence A i(u).
    The 6th step: subbase function random phase generates.Adopt the random phase reflection method to generate the random phase sequence
    Figure A2006100227250002C1
    The 7th step: the subbase function generates.With random phase sequence and the spectrum amplitude sequence A that generates i(u) the corresponding element transform domain that obtains the subbase function that multiplies each other is represented:
    To B i(u) carry out the FRFT inverse operation, obtain the time-domain representation of subbase function:
    Figure A2006100227250002C3
    The 8th step: interference components is rejected.The threshold value that the FRFT conversion that second step was produced and the 3rd step produce relatively, the component that surpasses threshold value is set to 0, other component is constant, obtain after interference components is rejected environmental interference estimation SA ' (u):
    SA &prime; ( u ) = 0 , | SA ( u ) | &GreaterEqual; A 7 SA ( u ) , | SA ( u ) | < A 7
    SA ' (u) is carried out the FRFT inverse operation, obtains rejecting the time-domain representation behind the interference components:
    sa′(t)＝IFRFT(SA′(u))
    The 9th step: to the processing of next interference components.I=i+1 repeats second and went on foot for the 8th step, up to i=N JmThe time till.
    The tenth step: residual interference is rejected.Can not concentrate energy at transform domain by RAT+FRFT to interference components in the environmental interference, the residual interference scalping method is adopted in the interference of handling, and rejects and disturbs, and further optimizes the basic function bandwidth, obtains rejecting the subbase function b after the residual interference R(n).
    The 11 step: system's basic function generates.With the subbase function cascade that generates, produce system's basic function:
    b ( n ) = b 1 ( n ) &CircleTimes; b 2 ( n ) &CircleTimes; . . . &CircleTimes; b N J ( n ) &CircleTimes; b R ( n )
    The 12 step: convergent-divergent.In order to keep the energy coincidence of each vector signal sequence, with the scaled C of amplitude times of sequence b (n), promptly the basic function time-domain representation becomes Cb (n);
    The 13 step: storage, storage sequence Cb (n) is as the basic signal of data-modulated and demodulation.
  2. 2. the Optimization Design of a kind of transform domain communication system basic function based on blurring mapping+fractional Fourier transform (RAT+FRFT) according to claim 1 is characterized in that, adopts RAT+FRFT to estimate the environmental interference parameter.
  3. 3. the Optimization Design of a kind of transform domain communication system basic function based on fractional Fourier transform (FRFT) according to claim 1, it is characterized in that, adopt the bandwidth optimization method to obtain interference components and reject thresholding, and obtain rejecting subbase function behind the interference components.
  4. 4. the Optimization Design of a kind of transform domain communication system basic function based on fractional Fourier transform (FRFT) according to claim 1 is characterized in that, adopts the residual interference elimination method to obtain subbase function after residual interference is rejected.
  5. 5. the Optimization Design of a kind of transform domain communication system basic function based on fractional Fourier transform (FRFT) according to claim 1 is characterized in that obtain system's basic function by subbase function cascade, the transmitting-receiving two-end basic function is conjugation each other.
CNA2006100227256A 2006-12-31 2006-12-31 Fractional Fourier transform and fuzzy transform based primary function optimization design method for transform domain under complex interference Pending CN101212259A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101345618B (en) * 2008-08-15 2012-09-19 哈尔滨工业大学 Encryption and decryption method for four-item weight FRFT communication based on variable parameter
CN109714773A (en) * 2019-01-11 2019-05-03 电子科技大学 A kind of sequence sets design method based on optimal clustering algorithm
US20230333149A1 (en) * 2020-01-10 2023-10-19 The Aerospace Corporation Fractional fourier transform-based spectrum analyzer

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101345618B (en) * 2008-08-15 2012-09-19 哈尔滨工业大学 Encryption and decryption method for four-item weight FRFT communication based on variable parameter
CN109714773A (en) * 2019-01-11 2019-05-03 电子科技大学 A kind of sequence sets design method based on optimal clustering algorithm
CN109714773B (en) * 2019-01-11 2021-07-02 电子科技大学 Sequence set design method based on optimal clustering strategy
US20230333149A1 (en) * 2020-01-10 2023-10-19 The Aerospace Corporation Fractional fourier transform-based spectrum analyzer

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