CN108134649B - Satellite-borne ADS-B signal burst detection method and system - Google Patents
Satellite-borne ADS-B signal burst detection method and system Download PDFInfo
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Abstract
The invention discloses a satellite-borne ADS-B signal burst detection method and a satellite-borne ADS-B signal burst detection system. The detection system includes: the device comprises an N symbol length integration module, a correlation peak judgment module and a front leader judgment output module. The N symbol length integration module completes the correlation operation function of the received signal and the local standard pulse; the correlation peak judging module judges whether a correlation peak exists according to monotonicity at two sides of the correlation peak; the leading head judging and outputting module analyzes the power and position relation of the judged and received correlation peak, and finally judges whether a frame of signal is received. The invention does not need to estimate the receiving power of the signal in the burst detection process of the ADS-B signal, increases the related peak detection of a signal-free area, and greatly improves the burst detection accuracy of the ADS-B signal.
Description
Technical Field
The invention discloses a satellite-borne ADS-B signal burst detection method and system, and belongs to the field of communication signal processing.
Background
Broadcast automatic dependent surveillance (ADS-B) is the future major surveillance technology determined by the international civil aviation organization. The ADS-B technology combines the satellite navigation technology, the communication technology, the airborne equipment, the ground equipment and other advanced technologies, provides a safer and more efficient air traffic monitoring means, can effectively improve the operation situation perception capability of controllers and pilots, expands the monitoring coverage range, and improves the air traffic safety level, the airspace capacity and the operation efficiency. The ADS-B signal is a signal which is broadcasted by an air aircraft and contains information data such as the height, position, speed, model and the like of the signal, and the signal adopts a pulse code modulation (PPM) modulation mode of 1090MHz S mode. Because the ADS-B signal is a discontinuous broadcast signal, the burst detection of the signal is a precondition for signal demodulation, and is also a key technology for ensuring the satellite to effectively observe the aircraft within the coverage area.
The method compares the level of the received over-sampling signal with a set threshold, judges to receive a pulse when a plurality of continuous sampling points exceed the threshold, and judges the rising edge and the falling edge of the pulse by judging the magnitude relation of the levels of the adjacent sampling points. The main disadvantages of this method are: 1. the pulse judgment is greatly influenced by the threshold, and the threshold needs to be determined by estimating the power of the received signal, so that the judgment complexity is increased; 2. the signals are not received in a matching way, and the anti-noise performance is poor.
The other is a correlation method, which is mainly different from the first method in that the received signal is correlated with a local standard pulse and then processed. Compared with the first method, the method has certain improvement on the anti-noise performance, but the judgment of the correlation peak value still needs to be compared with a set threshold, the judgment complexity is still higher, and after the judgment of the position and the power of the correlation peak is completed, the judgment accuracy of the preamble head is improved by further not utilizing the pulse-free signal data from the 4 th pulse to the data bit.
The existing background technology needs to estimate signal estimation so as to set an estimation threshold; meanwhile, in the correlation method, the comparison of the power and position relation of the correlation peak is relatively complex, and the accuracy and the complexity of the front leader judgment are improved.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the invention overcomes the defects of the prior art, provides a satellite-borne ADS-B signal burst detection method and a satellite-borne ADS-B signal burst detection system according to the signal characteristics of the ADS-B preamble, reduces the complexity of the preamble judgment, improves the accuracy of the preamble judgment to the maximum extent and has good engineering realizability.
The technical solution of the invention is as follows: a satellite-borne ADS-B signal burst detection method comprises the following steps:
the method comprises the following steps: receiving I-way data aiAnd Q data biSetting the length of the sliding window to be N, and calculating to obtain a correlation value x after the correlation of N symbol data and the local standard pulsej：
Wherein the content of the first and second substances,
sums are accumulated for the I-way data within the sliding window,
1,2, …, N, j 1,2, …, N-N + 1; n and N are respectively positive integers;
step two: receiving the output correlation value x of the first stepjJudging whether a correlation peak is detected according to monotonicity of two sides of the correlation peak;
step three: when 3 correlation peaks are detected, comparing the relative positions of the 3 correlation peaks with a standard signal, if the position comparison is successful, the preliminary judgment of the front leader is successful, and entering the fourth step; otherwise, the relative position relation of the two latter correlation peaks is kept, the step two is returned, and the next correlation peak is continuously searched;
step four: and after the preliminary judgment of the front guide head is successful, continuously carrying out related peak detection in the signal-free area, if the related peak is still detected, failing to judge the front guide head, otherwise, successfully judging the front guide head, and judging that a frame of effective ADS-B signal is received.
The method for judging the correlation peak in the step two comprises the following steps:
step 2.1: buffer M2N +1 correlation values xjSorting according to the receiving sequence and recording the sorted related value as the value tkK is 1,2, …, M, from M values tkSelecting N values and finding out the maximum value t of the N valuesmax(ii) a From M number of values tkOf which N values are selectedThe selection method comprises the following steps: when N is an even number, taking N numbers between N/2+1 and 3N/2; when N is an odd number, taking N numbers between (N +3)/2 and (3N + 1)/2;
step 2.2: according to the maximum value tmaxSelecting two values on the left side of the N values selected in step 2.1 and two values on the right side of the N values selected in step 2.1, respectively;
step 2.3: and (3) judging whether the two values on the left side selected in the step 2.2 and the maximum value meet the monotone increasing relationship or not, and whether the two values on the right side selected in the step 2.2 and the maximum value meet the monotone decreasing relationship or not, and if the two conditions are met simultaneously, judging that a correlation peak is detected.
4 values and the maximum value t selected in said step 2.2maxIn the 5 numbers, the absolute value of the difference of the position intervals of every two adjacent numbers is less than 2.
The third step comprises the following specific steps:
step 3.1: comparing the peak power of each correlation peak with the peak power of the detected effective correlation peak when detecting the correlation peak, if the condition that the power difference between every two correlation peaks is larger than 6dB, judging that the correlation peak with small peak power is a non-effective correlation peak, and detecting the correlation peak again;
step 3.2: when 3 effective correlation peaks are detected, comparing the relative positions of the 3 effective correlation peaks with 4 standard position relations of 3 standard pulses of the front of the ADS-B signal, and when the comparison errors of 2 spacing values of the 3 effective correlation peaks and the standard spacing values of the 4 standard position relations are less than or equal to 3, indicating that the position comparison is successful, otherwise, failing to compare.
The concrete method of the fourth step is as follows:
continuously detecting a correlation peak in a signal-free area, and if the correlation peak is detected and the difference value of the peak power of the correlation peak and the maximum peak power of the detected effective correlation peak is within 6dB, determining that the preamble head fails and detecting the correlation peak again; otherwise, the preamble determination is successful.
An on-board ADS-B signal burst detection system comprising: an N symbol length integration module, a correlation peak judgment module and a front leader judgment module;
the N symbol length integration module receives the I path data aiAnd Q data biSetting the length of the sliding window to be N, and calculating to obtain a correlation value x after the correlation of N symbol data and the local standard pulsej(ii) a 1,2, …, N, j 1,2, …, N-N + 1; n and N are respectively positive integers;
the correlation peak judging module receives the output correlation value x of the N symbol length integrating modulejJudging whether a correlation peak is detected according to monotonicity of two sides of the correlation peak;
the leading head judging module counts the detected correlation peaks, simultaneously records the interval of two adjacent correlation peaks, compares the relative positions of the 3 correlation peaks with a standard signal when detecting the 3 correlation peaks, and if the position comparison is successful, the leading head is preliminarily judged to be successful; otherwise, the relative position relation of the two latter correlation peaks is kept, and the correlation peak judgment module is returned to continue to search the next correlation peak;
and after the preliminary judgment of the front guide head is successful, the related peak judgment module continues to carry out related peak detection in the signal-free area, if the related peak is still detected, the front guide head judgment module judges that the front guide head judgment fails, otherwise, the front guide head judgment module judges that the front guide head judgment is successful and judges that a frame of effective ADS-B signal is received.
The correlation value xjThe calculation formula of (a) is as follows:
wherein the content of the first and second substances,
sums are accumulated for the I-way data within the sliding window,
The method for judging the correlation peak by the correlation peak judging module comprises the following steps:
step 2.1: buffer M2N +1 correlation values xjSorting according to the receiving sequence and recording the sorted related value as the value tkK is 1,2, …, M, from M values tkSelecting N values and finding out the maximum value t of the N valuesmax(ii) a From M number of values tkThe selection method for selecting N numerical values comprises the following steps: when N is an even number, taking N numbers between N/2+1 and 3N/2; when N is an odd number, taking N numbers between (N +3)/2 and (3N + 1)/2;
step 2.2: according to the maximum value tmaxSelecting two values on the left side of the N values selected in step 2.1 and two values on the right side of the N values selected in step 2.1, respectively;
step 2.3: and (3) judging whether the two values on the left side selected in the step 2.2 and the maximum value meet the monotone increasing relationship or not, and whether the two values on the right side selected in the step 2.2 and the maximum value meet the monotone decreasing relationship or not, and if the two conditions are met simultaneously, judging that a correlation peak is detected.
The specific steps of the leading head judging module for comparing the relative positions of the 3 correlation peaks with the standard signal are as follows:
step 3.1: comparing the peak power of each correlation peak with the peak power of the detected effective correlation peak when detecting the correlation peak, if the condition that the power difference between every two correlation peaks is larger than 6dB, judging that the correlation peak with small peak power is a non-effective correlation peak, and detecting the correlation peak again;
step 3.2: when 3 effective correlation peaks are detected, comparing the relative positions of the 3 effective correlation peaks with 4 standard position relations of 3 standard pulses of the front of the ADS-B signal, and when the comparison errors of 2 spacing values of the 3 effective correlation peaks and the standard spacing values of the 4 standard position relations are less than or equal to 3, indicating that the position comparison is successful, otherwise, failing to compare.
The specific method for judging success of the front leader judgment by the front leader judgment module is as follows:
continuously detecting a correlation peak in a signal-free area, and if the correlation peak is detected and the difference value of the peak power of the correlation peak and the maximum peak power of the detected effective correlation peak is within 6dB, determining that the preamble head fails and detecting the correlation peak again; otherwise, the preamble determination is successful.
Compared with the prior art, the invention has the advantages that:
(1) the search of the correlation peak completely utilizes the characteristics of the correlation peak, does not need to compare and judge with a set threshold, and reduces the judgment complexity;
(2) in the invention, the judgment of the position relation of the correlation peaks fully considers the influence of noise, the power consistency detection is carried out while each correlation peak is detected, and meanwhile, after 3 correlation peaks are detected, the position relation is compared with 4 possible combinations to judge whether the preamble is received, and the judgment method has better fault-tolerant performance;
(3) in the invention, after the judgment of the position and the power of the correlation peak is finished, the correlation peak is continuously searched in the time without pulse signals, if the correlation peak is still searched, the judgment of the front leader fails, the detection needs to be carried out again, otherwise, the judgment is successful. Increase this and judge, greatly promoted the judgement exactness of leading head.
Drawings
FIG. 1 is a schematic diagram of the detection method of the present invention;
FIG. 2 is a schematic diagram of a correlation peak determination process according to the present invention;
fig. 3 is a flow chart of preamble determination according to the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings.
As shown in fig. 1, the system for detecting a satellite-borne ADS-B signal burst according to the present invention includes: the device comprises an N symbol length integration module, a correlation peak judgment module and a front leader judgment module. Wherein:
and the N symbol length integration module completes the correlation operation of the received signal and the local standard pulse. Since ADS-B is a pulse code modulated signal, correlation with the local standard pulse signal is equivalent to cumulative summing of the N received signal sample data. Through signal correlation operation, the influence of noise on signals is reduced to the minimum, and the accuracy of peak value detection is greatly improved.
And the correlation peak judging module completes the detection function of the correlation peak. The conventional method of detecting a correlation peak is to compare the correlation value of a signal with a threshold, and when the peak power exceeds the threshold, a correlation peak is considered to be detected. The method needs to set a threshold through receiving signal power estimation, and obviously increases the detection complexity; meanwhile, the estimation of the received signal power is influenced by noise, so that the threshold setting error is larger, and the detection influence on a correlation peak is larger, so that the method has higher detection complexity and lower detection performance. The invention uses the monotone characteristics of both sides of the correlation peak to complete the detection of the correlation peak, firstly finds a maximum value of a correlation quantity, then performs monotonicity judgment on the left side and the right side of the maximum value, if the left side accords with the monotone increasing characteristic and the right side accords with the monotone decreasing characteristic, the detection is considered to detect a correlation peak, otherwise, the detection is not. The method only compares the magnitude of the adjacent value, does not need to set a comparison threshold, and does not need to estimate the signal power, thereby reducing the detection complexity and greatly reducing the influence of noise on the detection performance.
And the front guide head judging module finishes the final judgment of the front guide head. The module needs to count the detected correlation peaks and record the interval between two adjacent correlation peaks. When the 2 nd correlation peak and the 3 rd correlation peak are detected, the detected correlation peak power is required to be compared with the current correlation peak power, if the power difference between the two correlation peaks is more than 6dB, the correlation peak with a small power value is regarded as a non-effective correlation peak, and the detected correlation peaks are counted again; and when the 3 rd correlation peak is detected and the peak power of the correlation peak meets the conditions, combining the two interval values with the interval value of the standard pulse, comparing successfully, then preliminarily judging successfully by the front leader, otherwise, judging unsuccessfully, and reserving the two latter correlation peaks to detect the correlation peaks again. And finally, when the preliminary judgment of the front leader is successful, detecting a correlation peak in a pulse signal-free area, if the correlation peak is detected and the difference value between the peak power and the maximum peak power of the detected correlation peak is within 6dB, failing to judge the front leader, detecting the correlation peak again, and otherwise, successfully judging the front leader, and outputting the frame signal.
The invention relates to a satellite-borne ADS-B signal burst detection method, which comprises the following specific steps:
the method comprises the following steps: receiving I-way data aiAnd Q data biI is 1,2, …, N, the length of the sliding window is set to be N, and N I-path data accumulation sums in the sliding window are respectively calculated
And Q-way data accumulated sum
At the same time, the accumulated sum of the I path data and the Q path data is squared and then summed, and the correlation value x of N symbol data after being correlated with the local standard pulse is obtainedj，
Step two: receiving the output correlation value x of the first stepjJudging whether a correlation peak is detected according to monotonicity of two sides of the correlation peak;
the method for judging the correlation peak in the step two comprises the following steps:
step 2.1: buffer M2N +1 correlation values xjSorting according to the received sequence and re-recording the values as tkK is 1,2, …, M, when N is even number, taking N numbers between N/2+1 and 3N/2; when N is an odd number, taking N numbers between (N +3)/2 and (3N + 1)/2; finally, finding out the maximum value of the N numbers;
step 2.2: and respectively taking out two values on the left side and the right side except the middle N value according to the position of the maximum value, wherein the distance between the position of the value and the position of the maximum value is as large as possible, and the difference value of the distance values is within 2.
Step 2.3: and judging whether the left two values and the maximum value meet a monotone increasing relationship or not, judging whether the right two values and the maximum value meet a monotone decreasing relationship or not, and if the two conditions are met simultaneously, judging that a correlation peak is detected.
Step three: when 3 correlation peaks are detected, comparing the relative positions of the 3 correlation peaks with the standard signal, and entering the fourth step if the comparison is successful; otherwise, the relative position relation of the two latter correlation peaks is kept, and the next correlation peak is continuously searched for judgment;
the preliminary judgment method of the front guide head in the step three comprises the following steps:
step 3.1: comparing the peak power of each correlation peak with the peak power of the detected effective correlation peak when detecting the correlation peak, if the condition that the power difference between every two correlation peaks is larger than 6dB, judging that the correlation peak with small peak power is a non-effective correlation peak, and detecting the correlation peak again;
step 3.2: when 3 valid correlation peaks have been detected, the relative positions of the 3 correlation peaks are compared to the possible 4 standard positional relationships; when the comparison errors of the 2 spacing values of the correlation peak and the standard spacing value are less than or equal to 3, the position comparison is successful, otherwise, the comparison is failed; if the position comparison is successful, the preliminary judgment of the front leader is successful; otherwise, the judgment fails, the two latter correlation peaks are reserved, the next correlation peak is detected again, and the step 2.1 is carried out until the front leader judgment is successful;
step four: after the preliminary judgment of the front guide head is successful, the detection of the related peak is continuously carried out in the signal-free area, if the related peak is still detected, the judgment of the front guide head fails, otherwise, the judgment of the front guide head is successful, and a frame of effective signal is judged to be received;
the method for processing the signal-free area in the fourth step comprises the following steps: continuously detecting a correlation peak in a signal-free area, and if the correlation peak is detected and the difference value of the peak power of the correlation peak and the maximum peak power of the detected effective correlation peak is within 6dB, determining that the preamble head fails and detecting the correlation peak again; otherwise, the front leader judges successfully and outputs the frame signal.
Example (b):
the specific steps of a satellite-borne ADS-B signal burst detection method are as follows:
the method comprises the following steps: receiving I path and Q path data ai,biAnd I is 1,2, …, N, the length of the sliding window is set to be N, the window slides in the data receiving sequence and respectively calculates the accumulated sum of N paths of I and Q data in the window, and the accumulated sum of the I path and Q path data is squared and then summed to obtain the correlation value x of the N symbol data and the local standard pulse after correlationi；
Step two: receiving the output correlation value x of the first stepiBuffering M correlation values xiAnd if the two conditions are simultaneously satisfied, judging that a correlation peak is detected. The process flow is shown in fig. 2. In this embodiment, when N is 8 and M is 17, and M correlation values of the buffers are sequentially sorted, the positions of the left and right samples to be taken correspond to different positions of the maximum value, as shown in the following table.
Step three: the leading head judgment is performed, and a leading head judgment flow chart is shown in fig. 3, and the specific judgment flow is as follows:
1) maximum peak power PmaxInitializing to 0, and initializing a correlation peak search serial number i to 0;
2) searching for a correlation peak if the peak power is greater than Pmax6, judging that a valid correlation peak is received, updating the search sequence number i of the correlation peak to i +1, and otherwise, repeating the step 2); after updating, if the serial number i is 1, the step goes to step 3), if i is 2, the step 4) is gone to, if i is 3, the step 5 is gone to, and if i is 4, the step 7 is gone to);
3) searching the first correlation peak, and recording the peak power P1Will have the maximum peak valuePower PmaxIs updated to P1Starting clock counting by using the clock counting start point;
4) searching a second correlation peak, and marking the power value as P2Recording the clock count as two correlation peak time intervals d1Clearing the clock count; if the peak power is greater than PmaxThen P will bemaxIs updated to P2Otherwise, the updating is not carried out; if P is2>P1+6, the first correlation peak is determined to be a non-significant correlation peak, where P is1Is updated to P2Updating the correlation peak search serial number i to be 1, and repeating the step 2);
5) searching a third correlation peak, and marking the power value as P3Recording the clock count as d2Clearing the clock count; if the peak power is greater than PmaxThen P will bemaxIs updated to P2Otherwise, the updating is not carried out; if P is3>P1+6 and P3>P2+6, the 1 st and 2 nd correlation peaks are judged as non-effective correlation peaks, at this time, the clock count is cleared, the correlation peak search sequence number i is updated to 1, P1Is updated to P3Go to step 2); if P is3>P1+6 and P3≤P2+6, the first correlation peak is determined as the non-effective correlation peak, d1Is updated to d2，P1Is updated to P2，P2Is updated to P3Updating the search sequence number i to be 2, and turning to the step 2); if P is3≤P1+6 and P3>P2+6, the second correlation peak is determined as the non-significant correlation peak, d1Is updated to d1+d2，P2Is updated to P3Updating the search sequence number i to be 2, and turning to the step 2); if P is3≤P1+6 and P3≤P2+6, go to step 6);
6) determining correlation peak time interval d1，d2Whether the standard signal correlation peak interval condition is met or not, and if the standard signal correlation peak interval condition is met, turning to the step 2); if the condition is not satisfied, d is1Is updated to d2，P1Is updated to P2，P2Is updated to P3Updating the search sequence number i to be 2, and turning to the step 2);
7) searching a fourth correlation peak to record a clock count of d3Clearing the clock count; if d is3If the time interval is less than the given time interval, the judgment of the leader is wrong, and P is clearedmaxAnd a correlation peak search serial number i, and turning to the step 2); otherwise, the front leader judges correctly and enters information demodulation.
The invention is not described in detail and is within the knowledge of a person skilled in the art.
Claims (8)
1. A satellite-borne ADS-B signal burst detection method is characterized by comprising the following steps:
the method comprises the following steps: receiving I-way data aiAnd Q data biSetting the length of the sliding window to be N, and calculating to obtain a correlation value x after the correlation of N symbol data and the local standard pulsej：
Wherein the content of the first and second substances,
sums are accumulated for the I-way data within the sliding window,
1,2, …, N, j 1,2, …, N-N + 1; n and N are respectively positive integers;
step two: receiving the output correlation value x of the first stepjJudging whether a correlation peak is detected according to monotonicity of two sides of the correlation peak;
step three: when 3 correlation peaks are detected, comparing the relative positions of the 3 correlation peaks with a standard signal, if the position comparison is successful, the preliminary judgment of the front leader is successful, and entering the fourth step; otherwise, the relative position relation of the two latter correlation peaks is kept, the step two is returned, and the next correlation peak is continuously searched;
the third step comprises the following specific steps:
step 3.1: comparing the peak power of each correlation peak with the peak power of the detected effective correlation peak when detecting the correlation peak, if the condition that the power difference between every two correlation peaks is larger than 6dB, judging that the correlation peak with small peak power is a non-effective correlation peak, and detecting the correlation peak again;
step 3.2: when 3 effective correlation peaks are detected, comparing the relative positions of the 3 effective correlation peaks with 4 standard position relations of 3 standard pulses of the front of the ADS-B signal, and when the comparison errors of 2 spacing values of the 3 effective correlation peaks and the standard spacing values of the 4 standard position relations are less than or equal to 3, indicating that the position comparison is successful, otherwise, failing to compare;
step four: and after the preliminary judgment of the front guide head is successful, continuously carrying out related peak detection in the signal-free area, if the related peak is still detected, failing to judge the front guide head, otherwise, successfully judging the front guide head, and judging that a frame of effective ADS-B signal is received.
2. The method for detecting the burst of the satellite-borne ADS-B signal according to claim 1, wherein the method for determining the correlation peak in the second step is as follows:
step 2.1: buffer M2N +1 correlation values xjSorting according to the receiving sequence and recording the sorted related value as the value tkK is 1,2, …, M, from M values tkSelecting N values and finding out the maximum value t of the N valuesmax(ii) a From M number of values tkThe selection method for selecting N numerical values comprises the following steps: when N is an even number, taking N numbers between N/2+1 and 3N/2; when N is an odd number, taking N numbers between (N +3)/2 and (3N + 1)/2;
step 2.2: according to the maximum value tmaxSelecting two values on the left side of the N values selected in step 2.1 and two values on the right side of the N values selected in step 2.1, respectively;
step 2.3: and (3) judging whether the two values on the left side selected in the step 2.2 and the maximum value meet the monotone increasing relationship or not, and whether the two values on the right side selected in the step 2.2 and the maximum value meet the monotone decreasing relationship or not, and if the two conditions are met simultaneously, judging that a correlation peak is detected.
3. The method of claim 2, wherein the 4 values and the maximum value t selected in the step 2.2 are selectedmaxIn the 5 numbers, the absolute value of the difference of the position intervals of every two adjacent numbers is less than 2.
4. The method for detecting the burst of the satellite-borne ADS-B signal according to claim 3, wherein the fourth step is specifically:
continuously detecting a correlation peak in a signal-free area, and if the correlation peak is detected and the difference value of the peak power of the correlation peak and the maximum peak power of the detected effective correlation peak is within 6dB, determining that the preamble head fails and detecting the correlation peak again; otherwise, the preamble determination is successful.
5. An ADS-B signal burst detection system on board a satellite, comprising: an N symbol length integration module, a correlation peak judgment module and a front leader judgment module;
the N symbol length integration module receives the I path data aiAnd Q data biSetting the length of the sliding window to be N, and calculating to obtain a correlation value x after the correlation of N symbol data and the local standard pulsej(ii) a 1,2, …, N, j 1,2, …, N-N + 1; n and N are respectively positive integers;
the correlation peak judging module receives the output correlation value x of the N symbol length integrating modulejJudging whether a correlation peak is detected according to monotonicity of two sides of the correlation peak;
the leading head judging module counts the detected correlation peaks, simultaneously records the interval of two adjacent correlation peaks, compares the relative positions of the 3 correlation peaks with a standard signal when detecting the 3 correlation peaks, and if the position comparison is successful, the leading head is preliminarily judged to be successful; otherwise, the relative position relation of the two latter correlation peaks is kept, and the correlation peak judgment module is returned to continue to search the next correlation peak;
the specific steps of the leading head judging module for comparing the relative positions of the 3 correlation peaks with the standard signal are as follows:
step 3.1: comparing the peak power of each correlation peak with the peak power of the detected effective correlation peak when detecting the correlation peak, if the condition that the power difference between every two correlation peaks is larger than 6dB, judging that the correlation peak with small peak power is a non-effective correlation peak, and detecting the correlation peak again;
step 3.2: when 3 effective correlation peaks are detected, comparing the relative positions of the 3 effective correlation peaks with 4 standard position relations of 3 standard pulses of the front of the ADS-B signal, and when the comparison errors of 2 spacing values of the 3 effective correlation peaks and the standard spacing values of the 4 standard position relations are less than or equal to 3, indicating that the position comparison is successful, otherwise, failing to compare;
and after the preliminary judgment of the front guide head is successful, the related peak judgment module continues to carry out related peak detection in the signal-free area, if the related peak is still detected, the front guide head judgment module judges that the front guide head judgment fails, otherwise, the front guide head judgment module judges that the front guide head judgment is successful and judges that a frame of effective ADS-B signal is received.
6. An ADS-B signal burst detection system according to claim 5, wherein the correlation value xjThe calculation formula of (a) is as follows:
wherein the content of the first and second substances,
sums are accumulated for the I-way data within the sliding window,
7. The system of claim 6, wherein the method for determining the correlation peak by the correlation peak determining module is as follows:
step 2.1: buffer M2N +1 correlation values xjSorting according to the receiving sequence and recording the sorted related value as the value tkK is 1,2, …, M, from M values tkSelecting N values and finding out the maximum value t of the N valuesmax(ii) a From M number of values tkThe selection method for selecting N numerical values comprises the following steps: when N is an even number, taking N numbers between N/2+1 and 3N/2; when N is an odd number, taking N numbers between (N +3)/2 and (3N + 1)/2;
step 2.2: according to the maximum value tmaxSelecting two values on the left side of the N values selected in step 2.1 and two values on the right side of the N values selected in step 2.1, respectively;
step 2.3: and (3) judging whether the two values on the left side selected in the step 2.2 and the maximum value meet the monotone increasing relationship or not, and whether the two values on the right side selected in the step 2.2 and the maximum value meet the monotone decreasing relationship or not, and if the two conditions are met simultaneously, judging that a correlation peak is detected.
8. The ADS-B signal burst detection system according to claim 7, wherein the specific method for the preamble decision module to decide the success of the preamble decision is:
continuously detecting a correlation peak in a signal-free area, and if the correlation peak is detected and the difference value of the peak power of the correlation peak and the maximum peak power of the detected effective correlation peak is within 6dB, determining that the preamble head fails and detecting the correlation peak again; otherwise, the preamble determination is successful.
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