CN113223331B - ADS-B signal overlapping reconstruction separation method based on satellite-borne scene - Google Patents

ADS-B signal overlapping reconstruction separation method based on satellite-borne scene Download PDF

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CN113223331B
CN113223331B CN202110445635.2A CN202110445635A CN113223331B CN 113223331 B CN113223331 B CN 113223331B CN 202110445635 A CN202110445635 A CN 202110445635A CN 113223331 B CN113223331 B CN 113223331B
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CN113223331A (en
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刘亮
蔚保国
易卿武
邓志鑫
王振华
叶红军
贾诗雨
郎兴康
杨建雷
赵精博
李硕
秦明峰
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CETC 54 Research Institute
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    • G—PHYSICS
    • G08—SIGNALLING
    • G08G—TRAFFIC CONTROL SYSTEMS
    • G08G5/00—Traffic control systems for aircraft, e.g. air-traffic control [ATC]
    • G08G5/0073—Surveillance aids
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Abstract

The invention discloses an ADS-B signal overlapping reconstruction separation method based on a satellite-borne scene, and belongs to the technical field of signal processing. The method comprises the steps of firstly detecting and judging overlapped signals, respectively completing initial time detection of a strong ADS-B signal and a weak ADS-B signal in double overlapping, intercepting signal sampling points containing two overlapped signal lengths, completing demodulation of the strong ADS-B signal in overlapping, then utilizing the amplitude and information bits of the strong ADS-B signal to perform signal modulation reconstruction, stripping the strong ADS-B signal from an original waveform, and finally demodulating the weak ADS-B signal to obtain all ADS-B information in the overlapped signals. The method can be used in the field of satellite-borne scene ADS-B signal monitoring, realizes ADS-B signal overlapping separation in dense areas, and improves the success rate of information demodulation.

Description

ADS-B signal overlapping reconstruction separation method based on satellite-borne scene
Technical Field
The invention belongs to the technical field of signal processing, and particularly relates to an ADS-B signal overlapping reconstruction separation method based on a satellite-borne scene.
Background
With the increasing of the targets of aircrafts in all countries around the world, the satellite-borne ADS-B monitoring method is used for completing the global flight monitoring and becomes the main method. However, due to the wide area characteristic of the satellite-borne scene, unlike the ground ADS-B monitoring which monitors hundreds of frames simultaneously, the low-orbit satellite can monitor the number of targets more than thousands of frames simultaneously. Because the ADS-B signals are transmitted in a random broadcast mode, the ADS-B signals have very serious signal time domain overlapping probability from an aircraft dense area, so that very serious demodulation failure is caused, and a large amount of target monitoring information is lost. Therefore, corresponding measures need to be taken to improve the success rate of signal separation and the monitoring capacity of the system.
However, the conventional blind source signal separation method introduces a large amount of computation overhead in a satellite-borne scene, and is not suitable for being implemented on satellite platform hardware.
Disclosure of Invention
In view of this, the present invention provides an ADS-B signal overlapping reconstruction separation method based on a satellite-borne scene. The method can solve the problem that when the dense region of the receiving airplane is monitored in a satellite-borne scene, ADS-B signal frames are seriously overlapped in the time domain to cause a large amount of monitoring information to be lost.
The purpose of the invention is realized as follows:
an ADS-B signal overlapping reconstruction separation method based on a satellite-borne scene comprises the following steps:
(1) AD quantization is carried out on the received satellite-borne ADS-B signal, the carrier of the AD quantized ADS-B signal is stripped, and an envelope waveform is generated;
(2) performing cyclic correlation on the ADS-B signal by using a correlation sequence, completing frame header detection, completing frame signal demodulation when no other frame header exists in 112 mu s after the frame header is detected, and intercepting complete signal envelopes of two frames if another frame header is found;
(3) detecting signal amplitudes corresponding to the two frames, and determining a strong ADS-B signal and a weak ADS-B signal in double overlapping;
(4) demodulating the strong ADS-B signal to obtain an information bit of the strong ADS-B signal, and reconstructing the modulated ADS-B signal by combining the starting time and the amplitude of the frame header;
(5) and stripping the reconstructed and modulated ADS-B signal from the intercepted signal envelope, filtering chip edge burrs in the stripped signal by using low-pass filtering, demodulating the stripped and filtered signal to obtain information of the weak ADS-B signal, and completing information separation of the overlapped signal.
Further, the specific mode of the step (1) is as follows:
(101) AD quantization is carried out on the received satellite-borne ADS-B signal, the output signal after AD quantization is an ADS-B intermediate frequency signal S (n), the intermediate frequency signal carrier is stripped, and an ADS-B zero intermediate frequency complex signal S is obtained0(n), the stripping method comprises:
Figure BDA0003036725360000021
wherein, FsIs the sampling frequency of the intermediate frequency signal, fcThe central frequency of the intermediate frequency signal is shown, n is the number of sampling points, and j is an imaginary unit;
(102) calculating ADS-B zero intermediate frequency complex signal S0Envelope waveform S of (n)L(n), the calculation method is as follows:
Figure BDA0003036725360000031
where Re () is a real part operation and Im () is an imaginary part operation.
Further, the specific mode of the step (2) is as follows:
(201) performing cyclic correlation detection on the ADS-B signal by using a correlation sequence, wherein a sequence value x (n) before sampling of the correlation sequence is 10100001010000001001010110, sampling the sequence value according to a sampling rate to obtain a sampled correlation sequence y (n), and the calculation method comprises the following steps:
Figure BDA0003036725360000032
wherein the content of the first and second substances,
Figure BDA0003036725360000033
represents rounding down;
(202) performing cyclic correlation processing on the sampled correlation sequence and the envelope signal, and detecting an ADS-B signal when a correlation value W is higher than a threshold value, wherein the calculation method of the correlation value W is as follows:
Figure BDA0003036725360000034
wherein, N is the length of the correlation sequence, k is the sampling point digit of the envelope signal offset, and i is the accumulation variable;
(203) after finding that W is greater than the threshold value, recording k at this time as k1And recording the correlation value W at this time as W1In 120 microseconds time, i.e. from k1To
Figure BDA0003036725360000035
Figure BDA0003036725360000036
Searching another frame header within the signal sampling point sequence number range, if not finding, returning to the step (1), if finding the frame header, recording k at the moment as k2And recording the correlation value W at this time as W2Intercept from k1To
Figure BDA0003036725360000037
Signal envelope S within a range of sequence numbersL(n)。
Further, the specific mode of the step (3) is as follows:
(301) separately calculating the amplitudes A of two detection signals1And A2The calculation method comprises the following steps:
Figure BDA0003036725360000041
(302) compare amplitude value A1And A2The ADS-B frame with large amplitude value ofAnd the ADS-B frame with a strong signal and a small amplitude value is a weak signal.
Further, the specific mode of the step (4) is as follows:
(401) demodulating the strong ADS-B signal to obtain a demodulated information bit d1(n)；
(402) According to the information bit d1(n) start time sample number k, amplitude A and demodulation information bit d1(n) reconstructing the Strong ADS-B Signal waveform S1(n), the reconstruction method comprises the following steps:
Figure BDA0003036725360000042
further, the specific mode of the step (5) is as follows:
(501) and stripping the reconstructed and modulated ADS-B signal from the intercepted signal envelope, wherein the stripping method comprises the following steps:
SQ(n)＝SL(n)-S1(n)
(502) for the stripped signal SQ(n) carrying out low-pass filtering processing to remove chip edge burrs in the signal, wherein the bandwidth of a low-pass filter is selected to be 4 MHz;
(503) demodulating the filtered signal to obtain the information bit d of the weak ADS-B signal2And (n) completing information separation of the overlapped signals.
Compared with the prior art, the invention has the beneficial effects that:
1. in the prior art, only one of the overlapped signals is processed by using a re-triggering mode, and other overlapped signals are processed as noise, so that very serious information loss is caused, and the state of a monitoring target report is not updated timely. The method can greatly improve the demodulation probability under the satellite-borne ADS-B scene and ensure the reliable demodulation of the double-overlapped ADS-B signal.
2. The method can effectively separate and extract the time domain overlapping signals, respectively extract a plurality of information in the overlapping signals, and ensure that the satellite-borne ADS-B monitoring platform has the optimal monitoring performance.
3. The method can be used in the field of satellite-borne scene ADS-B signal monitoring, realizes ADS-B signal overlapping separation in dense areas, and improves the success rate of information demodulation.
Drawings
FIG. 1 is a flowchart of an ADS-B signal overlap reconstruction separation method in an embodiment of the present invention.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
As shown in fig. 1, an ADS-B signal overlapping reconstruction separation method based on a satellite-borne scene includes the following steps:
(1) receiving the satellite-borne ADS-B signal, stripping the carrier of the AD quantized ADS-B signal, and generating an envelope waveform; the concrete mode is as follows:
when ADS-B signal reception is completed, an antenna link is generally adopted to convert the signal into an amplified intermediate frequency signal, an AD analog-to-digital conversion chip quantizes the amplified intermediate frequency signal and outputs an ADS-B digital intermediate frequency signal S (n), and the carrier of the digital intermediate frequency signal is stripped to obtain an ADS-B zero intermediate frequency complex signal S0(n), the stripping method comprises:
Figure BDA0003036725360000051
wherein, FsIs the sampling frequency of the intermediate frequency signal, fcThe central frequency of the intermediate frequency signal is shown, n is the number of sampling points, and j is an imaginary unit;
after the carrier stripping is finished, calculating and generating an envelope waveform S of the signalL(n), the calculation method is as follows:
Figure BDA0003036725360000061
where Re () is a real part operation and Im () is an imaginary part operation.
(2) Performing cyclic correlation on the ADS-B signal by using a correlation sequence, completing frame header detection, completing demodulation of the frame signal when no other frame header exists in 112 mu s after the frame header is detected, and intercepting a complete signal envelope of two frames if another frame header is found; the concrete mode is as follows:
performing cyclic correlation detection on the ADS-B signal by using a correlation sequence, wherein a sequence value x (n) before sampling of the correlation sequence is 10100001010000001001010110, sampling the sequence value according to a sampling rate to obtain a sampled correlation sequence y (n), and the calculation method comprises the following steps:
Figure BDA0003036725360000062
performing cyclic correlation processing on the sampled correlation sequence and the envelope signal, and detecting an ADS-B signal when a correlation value W is higher than a threshold value, wherein the calculation method of the correlation value W is as follows:
Figure BDA0003036725360000063
wherein, N is the length of the correlation sequence, and k is the number of sampling points of the envelope signal offset.
After finding that W is greater than the threshold value, recording k at this time as k1Record the correlation value W at this time as W1In 120 microseconds time, i.e. from k1To
Figure BDA0003036725360000064
Searching another frame header within the signal sampling point sequence number range, if not finding, returning to the step (1), if finding the frame header, recording k at the moment as k2Record the correlation value W at this time as W2Intercept from k1To
Figure BDA0003036725360000065
Signal envelope S within a range of sequence numbersL(n)；
(3) Detecting signal amplitudes corresponding to the two frames, and determining a strong ADS-B signal and a weak ADS-B signal in double overlapping; the concrete mode is as follows:
separately calculating the amplitudes A of two detection signals1And A2A calculation partyThe method comprises the following steps:
Figure BDA0003036725360000071
compare amplitude value A1And A2The ADS-B frame with a large amplitude value is a strong signal, and the ADS-B frame with a small amplitude value is a weak signal.
(4) Demodulating the strong ADS-B signal to obtain an information bit of the strong ADS-B signal, and reconstructing the modulated ADS-B signal by combining the starting time and the amplitude of the frame header; the concrete mode is as follows:
firstly, the information demodulation of the strong ADS-B signal is completed by using the conventional demodulation method to obtain the demodulation information bit d1(n)；
According to the initial time sampling point sequence number k, amplitude A and demodulation information bit d of the strong ADS-B information bit1(n) reconstruction of Strong ADS-B Signal waveform S1(n), namely, reconstructing the information bits according to the modulation format of the ADS-B signal, wherein the adopted method comprises the following steps:
Figure BDA0003036725360000072
(5) and stripping the reconstructed ADS-B signal from the intercepted signal envelope, filtering chip edge burrs in the stripped signal by using low-pass filtering, demodulating the stripped and filtered signal to obtain information of the weak ADS-B signal, and completing information separation of the overlapped signal. The concrete mode is as follows:
firstly, stripping a reconstructed ADS-B signal from an intercepted signal envelope, and finishing strong signal stripping by using a subtraction mode according to the strong ADS-B reconstructed in the previous step, wherein the stripping method comprises the following steps:
SQ(n)＝SL(n)-S1(n)
for the stripped signal SQ(n) only contains ADS-B weak signal, but because the strong signal itself is the reconstructed signal and contains high frequency component in its interior, it has to make low-pass filtering treatment to remove chip edge burr in the signal, and the low-pass filter bandwidth is selectedTaking the frequency as 4 MHz;
demodulating the stripped and filtered signal to obtain the information bit d of the weak ADS-B signal2(n) to complete information separation of the overlapped signals.
The method solves the problem that when the dense region of the receiving airplane is monitored in a satellite-borne scene, ADS-B signal frames are seriously overlapped in the time domain to cause a large amount of monitoring information to be lost. The method comprises the steps of firstly, detecting and judging overlapped signals, respectively completing initial time detection of a strong ADS-B signal and a weak ADS-B signal in double overlapping, intercepting signal sampling points containing two overlapped signal lengths, completing demodulation of the strong ADS-B signal in overlapping, then utilizing the amplitude and information bits of the strong ADS-B signal to perform signal modulation reconstruction, stripping the strong ADS-B signal from an original waveform, and finally demodulating the weak ADS-B signal to obtain all ADS-B information in the overlapped signals.

Claims (5)

1. An ADS-B signal overlapping reconstruction separation method based on a satellite-borne scene is characterized by comprising the following steps:
(1) AD quantization is carried out on the received satellite-borne ADS-B signal, the carrier of the AD quantized ADS-B signal is stripped, and an envelope waveform is generated;
(2) performing cyclic correlation on the ADS-B signal by using a correlation sequence, completing frame header detection, completing frame signal demodulation when no other frame header exists in 112 mu s after the frame header is detected, and intercepting complete signal envelopes of two frames if another frame header is found;
the specific mode of the step (2) is as follows:
(201) performing cyclic correlation detection on the ADS-B signal by using a correlation sequence, wherein a sequence value x (n) before sampling of the correlation sequence is 10100001010000001001010110, sampling the sequence value according to a sampling rate to obtain a sampled correlation sequence y (n), and the calculation method comprises the following steps:
Figure FDA0003537754080000011
wherein the content of the first and second substances,
Figure FDA0003537754080000012
represents rounding down;
(202) performing cyclic correlation processing on the sampled correlation sequence and the envelope signal, and detecting an ADS-B signal when a correlation value W is higher than a threshold value, wherein the calculation method of the correlation value W is as follows:
Figure FDA0003537754080000013
wherein, N is the length of the correlation sequence, k is the sampling point digit of the envelope signal offset, and i is the accumulation variable;
(203) after finding that W is greater than the threshold value, recording k at this time as k1And recording the correlation value W at this time as W1In 120 microseconds time, i.e. from k1To
Figure FDA0003537754080000014
Figure FDA0003537754080000021
Searching another frame header within the signal sampling point sequence number range, if not finding, returning to the step (1), if finding the frame header, recording k at the moment as k2And recording the correlation value W at this time as W2Intercept from k1To
Figure FDA0003537754080000022
Signal envelope S within a range of sequence numbersL(n)；
(3) Detecting signal amplitudes corresponding to the two frames, and determining a strong ADS-B signal and a weak ADS-B signal in double overlapping;
(4) demodulating the strong ADS-B signal to obtain an information bit of the strong ADS-B signal, and reconstructing the modulated ADS-B signal by combining the starting time and the amplitude of the frame header;
(5) and stripping the reconstructed and modulated ADS-B signal from the intercepted signal envelope, filtering chip edge burrs in the stripped signal by using low-pass filtering, demodulating the stripped and filtered signal to obtain information of the weak ADS-B signal, and completing information separation of the overlapped signal.
2. The ADS-B signal overlapping reconstruction separation method based on the spaceborne scene according to claim 1, wherein the specific mode of the step (1) is as follows:
(101) AD quantization is carried out on the received satellite-borne ADS-B signal, the output signal after AD quantization is an ADS-B intermediate frequency signal S (n), the intermediate frequency signal carrier is stripped, and an ADS-B zero intermediate frequency complex signal S0(n) is obtained, and the stripping method comprises the following steps:
Figure FDA0003537754080000023
wherein, FSIs the sampling frequency of the intermediate frequency signal, fCThe central frequency of the intermediate frequency signal is shown, n is the number of sampling points, and j is an imaginary unit;
(102) calculating ADS-B zero intermediate frequency complex signal S0Envelope waveform S of (n)L(n), the calculation method is as follows:
Figure FDA0003537754080000031
where Re () is a real part operation and Im () is an imaginary part operation.
3. The ADS-B signal overlapping reconstruction separation method based on the satellite-borne scene according to claim 2, wherein the step (3) is specifically performed in a manner of:
(301) separately calculating the amplitudes A of two detection signals1And A2The calculation method comprises the following steps:
Figure FDA0003537754080000032
(302) compare amplitude value A1And A2Large and large amplitude value of ADThe S-B frame is a strong signal, and the ADS-B frame with a small amplitude value is a weak signal.
4. The ADS-B signal overlapping reconstruction separation method based on the satellite-borne scene according to claim 3, wherein the specific manner of the step (4) is as follows:
(401) demodulating the strong ADS-B signal to obtain a demodulated information bit d1(n)；
(402) According to the information bit d1(n) start time sample number k, amplitude A and demodulation information bit d1(n) reconstructing the Strong ADS-B Signal waveform S1(n), the reconstruction method comprises the following steps:
Figure FDA0003537754080000033
5. the ADS-B signal overlapping reconstruction separation method based on the spaceborne scene according to claim 4, wherein the specific mode of the step (5) is as follows:
(501) and stripping the reconstructed and modulated ADS-B signal from the intercepted signal envelope, wherein the stripping method comprises the following steps:
SQ(n)=SL(n)-S1(n)
(502) for the stripped signal SQ(n) carrying out low-pass filtering processing to remove chip edge burrs in the signal, wherein the bandwidth of a low-pass filter is selected to be 4 MHz;
(503) demodulating the filtered signal to obtain the information bit d of the weak ADS-B signal2And (n) completing information separation of the overlapped signals.
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CN107959645A (en) * 2017-12-15 2018-04-24 航天恒星科技有限公司 The separation method of ADS-B signals
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