CN105227400A - A kind of for time become the adaptive estimation method of ADS-B message time delay - Google Patents

Abstract

The invention belongs to Adaptive Signal Processing technical field, provide a kind of ADS based on impulse noise mitigation B message time delay adaptive estimation method.The feature of this method is the radio signal emission source of first supposing to assist near course line, and obtains not by the Doppler frequency shift indicatrix of time delay influence by carrier frequency estimation method; Secondly by ADS the decoding of B message, utilize formulae discovery to obtain the Doppler frequency shift indicatrix being subject to time delay influence; Finally, utilize the adaptive algorithm of impulse noise mitigation estimate instantaneous ADS B message time delay, and provide theoretical foundation for delay compensation.Become when the present invention can realize ADS the estimation of time delay of B message and tracking, and for ADS the delay compensation of B message provide foundation, by compensating, improve ADS the position of B message carrying and the accuracy of velocity information and reliability.

Description

A kind of for time become the adaptive estimation method of ADS-B message time delay

Technical field

The present invention relates to Adaptive Signal Processing technical field, relate to civil aviaton ADS ?the delay time estimation method of B message, be related specifically to the ADS that becomes when utilizing the maximal correlation entropy recurrence adaptive algorithm pair based on expansion ?B message carry out the method for time delay estimation and tracking.

Background technology

Automatic dependent surveillance broadcast ADS ?B (AutomaticDependentSurveillance ?Broadcast) system be the supervisory control system that the data Auto broadcast that Airplane Navigation Equipment and navigation system generate is gone out by broadcast mode data chain by airborne vehicle, compared with conventional radar, all have superiority in all many-sides such as turnover rate, connected mode and load modes, thus the indispensable means of air traffic control (AirTrafficControl, ATC) are become gradually.

But as carrying civil aviaton aircraft state of flight as the ADS of the information such as position and speed ?B message but because the message information collection of this system and message generting machanism, and the random delay become when existing.Such time to postpone a meeting or conference the accuracy of the information such as the position that reduces the carrying of ADS ?B message and speed and reliability.Due to ADS ?B technology be an emerging technology, for ADS ?the delay time estimation method of B message need perfect further.

Summary of the invention

The technical issues that need to address of the present invention be in prior art cannot pair time become ADS ?B message time delay carry out dynamic, real-time estimation and the defect of tracking, there is provided a kind of ADS ?the method of B message time delay dynamic estimation and tracking, the technical scheme of employing be by paired pulses noise have compared with the adaptive filter algorithm of high inhibition ability realize to civil aviaton ADS ?the dynamic estimation of B message time delay and tracking.Used adaptive filter algorithm is the recurrence maximal correlation entropy adaptive algorithm of expansion.

The present invention be based on impulse noise mitigation ADS ?B message time delay adaptive estimation method, first by carrier frequency estimate to obtain carry from aircraft scattered signal not by ADS ?the Doppler frequency shift indicatrix that affects of B message time delay, then utilize Doppler shift formula calculate obtain be subject to ADS ?B message time delay impact Doppler frequency shift indicatrix, become when finally utilizing the adaptive filter algorithm pair of impulse noise mitigation ADS ?the time delay of B message estimate, technical scheme comprises following concrete steps:

The first step, based on auxiliary source utilize carrier frequency estimation method obtain be not subject to ADS ?B message time delay impact Doppler frequency shift time-frequency curve.

(1) near civil air route, launch the modulation signal emission source with carrier component.

(2) zero intermediate frequency is mixed to the modulation signal through aircraft scattering, and carries out sampling and receiving.

(3) segmentation is carried out to the received signal.The data obtained in the first step (2) are carried out the Overlapping Fragment of equal time length, time span shared by every segment data can 0.5 ?choose within the scope of 2 seconds.Except first paragraph and final stage, other sections all with this section before and this section after data overlap, overlap length is the half of this segment length.

(4) Doppler frequency shift corresponding to every one piece of data is estimated.Fast Fourier transform is carried out to one piece of data every in the first step (3), and obtains the frequency spectrum of corresponding data, the Doppler frequency shift corresponding with this segment data according to the location estimation of peak value in frequency spectrum.The formula of Fourier transform is:

$X\left(j\mathrm{\Ω}\right)={\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}x\left(t\right)e^{-j\mathrm{\Ω}t}dt$

Wherein, x (t) represents the signal of t change in time, and X (j Ω) represents the multipair frequency spectrum of answering of signal.

(5) Doppler frequency shift curve is formed.Utilize in the first step (4) obtain Doppler frequency shift composition be not subject to ADS ?the Doppler frequency shift curve of B message time delay impact, because everywhere Doppler frequency shift is all corresponding to not data segment in the same time, therefore this Doppler frequency shift curve is the curve about time variable.

(6) more intensive Doppler frequency shift curve is obtained.Linear interpolation and extraction are carried out to the Doppler frequency shift curve in the first step (5), the time point of Doppler curve is accurate to 0.05 ?a certain moment within the scope of 0.2 second, with obtain more intensive time dependent be not subject to ADS ?the Doppler frequency shift indicatrix of B message time delay impact.

Second step, based on ADS ?the speed message of B and position message calculate the Doppler frequency shift time-frequency curve being subject to time delay influence.

(1) to ADS ?the speed message of B and position message information carry out linear interpolation, obtain position and the velocity information of the aircraft at each whole time precision place.First the time of reception of speed message and position message is rounded to 0.05 ?precision sometime within the scope of 0.2 second, this time precision is identical with the time precision in the first step (6), then carry out interpolation according to this time precision, obtain position and the velocity information of more intensive time dependent aircraft.

(2) position of the aircraft obtained after utilizing interpolation and velocity information, calculate be subject to ADS ?B message time delay impact Doppler frequency shift curve.Because after interpolation, speed message is different with the start/stop time of position message, therefore using positional information and velocity information the longest simultaneous time range as ADS ?scope effective time of B message, and utilize the positional information in this effective range and velocity information, by Doppler shift formula calculate be subject to ADS ?B message time delay impact Doppler frequency shift indicatrix, Doppler shift formula is f _Δ(t)=f _c(1-v _p(t) ^td _pt(t)/c) (1-v _p(t) ^td _pr(t)/c)-f _c, wherein d _ptt () represents the unit direction vector being pointed to aircraft position by the transmitter of auxiliary source, d _prt () represents the unit direction vector being pointed to aircraft position by receiver, v in addition _prepresent the velocity information of aircraft, f _crepresent the carrier frequency transmitted, c represents the speed of light.

3rd step, become when utilizing the adaptive approach pair of impulse noise mitigation ADS ?B message time delay carry out dynamic estimation and tracking.

(1) two the Doppler frequency shift indicatrix scopes of simultaneous maximum time obtained with the first step and second step are as the criterion, and choose the Doppler frequency shift indicatrix in this time range respectively.Using the first step obtain be not subject to ADS ?B message time delay impact Doppler frequency shift curve as the input signal of adaptive algorithm, be denoted as f _p(n).Using second step obtain be subject to ADS ?B message time delay impact Doppler frequency shift curve as the desired signal of adaptive algorithm, be denoted as f _c(n); Wherein, n is integer, represents discrete-time variable.

(2) by initial time to the input signal of current time and desired signal pair in the adaptive algorithm of input constraint impulsive noise, pair time become time delay estimate and follow the tracks of; Wherein, N represents current time.This adaptive algorithm is called the recurrence maximal correlation entropy adaptive algorithm of expansion, and its flow process is:

First, in the n=0 moment, initialization is carried out to signal parameter

w(0)＝0,P(0)＝λ ^-1I，

Wherein w represents the weight coefficient vector of filter, and P represents the inverse matrix of this section of input signal autocorrelation matrix, and λ represents and forgets factor, I representation unit battle array.

Secondly, when n >=1, the coefficient according to following process recursive resolve filter:

e(n)＝d(n)-u ^T(n)w(n-1)

$k\left(n\right)=\mathrm{\α}P(n-1)u\left(n\right)/\left({\mathrm{\κ}}_{\mathrm{\σ}}^{-1}\right(e\left(n\right))+u^T\left(n\right)P(n-1)u\left(n\right))$

w(n)＝αw(n-1)+e(n)k(n)

P(n)＝α ²P(n-1)-αk(n)u ^T(n)P(n-1)

Wherein, u (n) represents the input vector of adaptive algorithm, f from the 3rd step (1) _pobtain in n data that () comprises, d (n) represents desired signal, by f in second step (1) _pn data that () comprises are formed, and e (n) represents error, and k (n) represents gain.α can choose in [0.9,0.9999] scope, embodies the time range degree of time delay. ${\mathrm{\κ}}_{\mathrm{\σ}}(\·)=\exp (-{(\·)}^2/(2{\mathrm{\σ}}^2))/\sqrt{2\mathrm{\π}}\mathrm{\σ}$ Represent gaussian kernel function.

(3) by the adaptive algorithm in the 3rd step (2), the weight coefficient vector of each moment filter can be obtained, utilize further maximum weight coefficient according to usual adaptive-filtering delay time estimation method to ADS ?B time delay estimate.By above-mentioned adaptive algorithm, not only can to non-time-varying ADS ?B message time delay estimate, can also pair time become ADS ?B message time delay estimate and follow the tracks of.

Become when the present invention can realize ADS ?the estimation of time delay of B message and tracking, and for ADS ?the delay compensation of B message provide foundation, by compensating, improve ADS ?the position of B message carrying and the accuracy of velocity information and reliability.

Accompanying drawing explanation

Accompanying drawing 1 be ADS of the present invention ?the overview flow chart of B message time delay method of estimation.

Accompanying drawing 2 is flow charts of the adaptive algorithm in the present invention with impulse noise mitigation.

Accompanying drawing 3 is T/F spectrums of aircraft scattered signal in the present invention.

Accompanying drawing 4 does not estimate in the present invention and Doppler frequency shift indicatrix comparison diagram during delay compensation.

Accompanying drawing 5 has estimated in the present invention and Doppler frequency shift indicatrix comparison diagram during delay compensation.

Embodiment

Below in conjunction with accompanying drawing and technical scheme describe in detail a kind of for time become ADS ?the adaptive estimation method of B message time delay, overall flow figure as shown in Figure 1:

The first step. the carrier frequency estimation method that utilizes based on auxiliary source obtains the Doppler frequency shift time-frequency curve not being subject to the impact of ADS ?B message time delay.

(1) near civil air route, launch the modulation signal emission source with carrier component.For electromagnetic wave energy space loss rule and transmitter power, the position of auxiliary radio signal emitting-source is selected near course line, dodge civil aviaton's communications band, even if to ensure that transmitting power is less, the signal of the aircraft scattering that still can obtain at receiver place has higher signal to noise ratio.

(2) modulation signal through aircraft scattering is received, and be mixed to zero intermediate frequency.The signal received, as mixing foundation, is mixed to zero intermediate frequency by the carrier frequency transmitted using auxiliary source.

(3) carry out Frequency Estimation to the received signal, and with the estimated result in each moment form be not subject to ADS ?the Doppler frequency shift curve of B message time delay impact.First, in order to ensure the slickness of the Doppler frequency shift indicatrix of estimation and ensure the frequency resolution of 0.5 hertz, the data of acquisition are carried out Overlapping Fragment, the length of every section is 1 second, except first section and the last period, overlapping with the last period 1 second of each section, except latter end, each section with latter one section overlapping 1 second.Then the data being 2 seconds to each segment length are carried out fast Fourier transform and are obtained the frequency spectrum of corresponding data, and estimating Doppler frequency shift features accordingly, then it can be used as this Doppler frequency shift feature corresponding to segment data central instant.

(4) by linear interpolation and extraction, the time point of Doppler curve is accurate to 0.1 second.Is rounded to the precision of 0.1 second the moment corresponding for the data obtained in the first step (3), then according to the density of every 0.1 second 1 data point, carry out linear interpolation, obtain more intensive time dependent be not subject to ADS ?the Doppler frequency shift indicatrix of B message time delay impact.

Second step. calculate based on the speed message of ADS ?B and position message the Doppler frequency shift time-frequency curve being subject to time delay influence.

(1) utilize linear interpolation, obtain position and the velocity information of the aircraft at each 0.1 second place.First is rounded to the precision of 0.1 second the time of reception of message, then according to the density of every 0.1 second 1 data point, carries out interpolation, obtain position and the velocity information curve of more intensive time dependent aircraft.

(2) utilize by ADS ?the flight parameter in each moment that obtains of B message information, calculate be subject to ADS ?the Doppler frequency shift curve of B message time delay impact.Consider that speed message is different with the start/stop time of position message, using positional information after interpolation and the simultaneous maximum duration scope of velocity information as ADS ?scope effective time of B message, and utilize the position in effective range and velocity information, utilize Doppler shift formula calculate be subject to ADS ?B message time delay impact Doppler frequency shift indicatrix.Wherein, Doppler shift formula is f _Δ(t)=f _c(1-v _p(t) ^td _pt(t)/c) (1-v _p(t) ^td _pr(t)/c)-f _c, wherein d _ptt () represents the unit direction vector being pointed to aircraft position by the transmitter of auxiliary source, d _prt () represents the unit direction vector being pointed to aircraft position by receiver, v in addition _prepresent the velocity information of aircraft, f _crepresent the carrier frequency transmitted, c represents the speed of light.

3rd step. utilize the time delay of the ADS ?B message become during the ART network of impulse noise mitigation.

(1) be as the criterion with the simultaneous time range of two kinds of Doppler frequency shift indicatrixes, choose the Doppler frequency shift Characteristic Curve data in this time range respectively.

(2) using be not subject to ADS ?B message time delay impact Doppler frequency shift curve as the input signal of adaptive algorithm, be denoted as f _p(n), as shown in Figure 2.

(3) using be subject to ADS ?B message time delay impact Doppler frequency shift curve as the desired signal of adaptive algorithm, be denoted as f _c(n), as shown in Figure 2.

(4) input signal by current time (n=N) and desired signal pair is utilized the time delay become during adaptive algorithm pair by impulse noise mitigation is estimated and compensates.Due to ADS ?the general range of B message time delay be [0,2] second, according to the time interval of 0.1 second, the exponent number choosing sef-adapting filter was 21 rank, arranged its weight for [h ₀(n), h ₁(n) ..., h ₁₉(n), h ₂₀(n)].Utilize the coefficient of input signal and desired signal training sef-adapting filter, try to achieve the position that filter weight is maximum, namely then utilize m (n) to postpone estimated time at moment n, finally to ADS ?the position in each moment in B message data and velocity information compensate.As shown in Figure 3, two Doppler frequency shift curve comparison figure before estimation compensation and after estimation compensation respectively as shown in Figure 4 and Figure 5 for the time-frequency spectrum of real scattered signal.

Claims (2)

1. for time become the adaptive estimation method of ADS-B message time delay, it is characterized in that, comprise the following steps:

The first step, the carrier frequency estimation method that utilizes based on auxiliary source obtains the Doppler frequency shift time-frequency curve not being subject to the impact of ADS-B message time delay;

(1) near civil air route, launch the modulation signal emission source with carrier component;

(2) zero intermediate frequency is mixed to the modulation signal through aircraft scattering, carries out sampling and receiving;

(3) carry out segmentation to the received signal, the data obtained are carried out the Overlapping Fragment of equal time length in step (2); Except first paragraph and final stage, other sections all with this section before and this section after data overlap, overlap length is the half of this segment length;

(4) estimate the Doppler frequency shift corresponding to every one piece of data, formula is pressed to one piece of data every in step (3) carry out fast Fourier transform, obtain the frequency spectrum of corresponding data, the Doppler frequency shift corresponding with this segment data according to the location estimation of peak value in frequency spectrum;

Wherein, x (t) represents the signal of t change in time, and X (j Ω) represents the multipair frequency spectrum of answering of signal;

(5) utilize in step (4) and obtain the Doppler frequency shift curve that Doppler frequency shift composition is not subject to the impact of ADS-B message time delay;

(6) linear interpolation and extraction are carried out to the Doppler frequency shift curve in step (5), the time point of Doppler curve is accurate to a certain moment, to obtain the more intensive time dependent Doppler frequency shift indicatrix not being subject to the impact of ADS-B message time delay;

Second step, calculates based on the speed message of ADS-B and position message the Doppler frequency shift time-frequency curve being subject to time delay influence;

(1) linear interpolation is carried out to the speed message of ADS-B and position message information, obtain position and the velocity information of the aircraft at each whole time precision place; First the time of reception of speed message and position message is rounded to precision sometime, this time precision is identical with the time precision in the first step (6), then carry out interpolation according to this time precision, obtain position and the velocity information of more intensive time dependent aircraft;

(2) position of the aircraft obtained after utilizing interpolation and velocity information, calculate the Doppler frequency shift curve being subject to the impact of ADS-B message time delay; Because after interpolation, speed message is different with the start/stop time of position message, using positional information and velocity information the longest simultaneous time range as scope effective time of ADS-B message, and utilize the positional information in this effective range and velocity information; The Doppler frequency shift indicatrix being subject to the impact of ADS-B message time delay is calculated by Doppler shift formula;

Doppler shift formula is f _Δ(t)=f _c(1-v _p(t) ^td _pt(t)/c) (1-v _p(t) ^td _pr(t)/c)-f _c, wherein d _ptt () represents the unit direction vector being pointed to aircraft position by the transmitter of auxiliary source, d _prt () represents the unit direction vector being pointed to aircraft position by receiver, v _prepresent the velocity information of aircraft, f _crepresent the carrier frequency transmitted, c represents the speed of light;

3rd step, becomes ADS-B message time delay and carries out dynamic estimation and tracking when utilizing the adaptive approach pair of impulse noise mitigation;

(1) two the Doppler frequency shift indicatrix scopes of simultaneous maximum time obtained with the first step and second step are as the criterion, and choose the Doppler frequency shift indicatrix in this time range respectively; The Doppler frequency shift curve not being subject to the impact of the ADS-B message time delay first step obtained, as the input signal of adaptive algorithm, is denoted as f _p(n); The Doppler frequency shift curve being subject to the impact of ADS-B message time delay obtained by second step, as the desired signal of adaptive algorithm, is denoted as f _c(n); Wherein, n is integer, represents discrete-time variable;

(2) by initial time to the input signal of current time and desired signal to { f _p(n), in the adaptive algorithm of input constraint impulsive noise, pair time become time delay estimate and follow the tracks of; Wherein, N represents current time;

(3) by the adaptive algorithm in the 3rd step (2), the weight coefficient vector of each moment filter can be obtained, utilize maximum weight coefficient to estimate ADS-B time delay according to usual adaptive-filtering delay time estimation method.

2. as claimed in claim 1 a kind of for time become the adaptive estimation method of ADS-B message time delay, it is characterized in that, its flow process of adaptive algorithm in the first step (3) is:

First, in the n=0 moment, initialization is carried out to signal parameter

w(0)＝0,P(0)＝λ ^-1I，

Wherein w represents the weight coefficient vector of filter, and P represents the inverse matrix of this section of input signal autocorrelation matrix, and λ represents and forgets factor, I representation unit battle array;

Secondly, when n >=1, the coefficient according to following process recursive resolve filter:

e(n)＝d(n)-u ^T(n)w(n-1)

$k\left(n\right)=\mathrm{\α}P(n-1)u\left(n\right)/\left({\mathrm{\κ}}_{\mathrm{\σ}}^{-1}\right(e\left(n\right))+u^T(n\left)P\right(n-1\left)u\right(n\left)\right)$

w(n)＝αw(n-1)+e(n)k(n)

P(n)＝α ²P(n-1)-αk(n)u ^T(n)P(n-1)

Wherein, u (n) represents the input vector of adaptive algorithm, f from the 3rd step (1) _pobtain in n data that () comprises, d (n) represents desired signal, by f in second step (1) _pn data that () comprises are formed, and e (n) represents error, and k (n) represents gain; α chooses in [0.9,0.9999] scope, embodies the time range degree of time delay; ${\mathrm{\κ}}_{\mathrm{\σ}}(\·)=\exp (-{(\·)}^2/(2{\mathrm{\σ}}^2\left)\right)/\sqrt{2\mathrm{\π}}\mathrm{\σ}$ Represent gaussian kernel function.