A decoding method for secondary radar conventional mode reply based on amplitude and phase characteristics

Abstract

The present invention provides a secondary radar conventional mode reply decoding method based on amplitude-phase feature combination, comprising the following steps: S1, reply pulse edge detection step; S2, reply sequence frame detection and pulse position code extraction step; S3, reply frame and pulse bit interleaving judgment step; S4, reply pulse bit amplitude-phase extraction step; S5, interleaved reply sequence pulse amplitude-phase inverse solution step; S6, reply sequence amplitude-phase code extraction step. The present invention can improve the accuracy of reply decoding.

Description

Technical Field

[0001] The present invention relates to the field of radar detection technology, and in particular to a secondary radar conventional mode response decoding method based on the combination of amplitude and phase characteristics. Background Art

[0002] Secondary radar can accurately detect the aircraft's position, altitude, and speed information, and is widely used in air traffic control fields such as military and civil route flight monitoring, daily and military exercise flight support, etc. When the aircraft is too close, the flight traffic is large, and the electromagnetic environment is complex, the secondary radar's detection performance will be significantly reduced, and even code jumps and altitude jumps will cause long-term detection code errors. After analysis, since the secondary radar's reply signal is a sequence of pulses, the root cause of the above problems is the interweaving of reply codes and the interweaving of reply codes and reflection codes, resulting in errors in the aircraft's code and altitude extraction.

[0003] Existing secondary radar conventional mode reply decoding method:

[0004] Only the amplitude signal of the sum channel is used as the only data source for decoding. When the reply pulses received by the sum channel are interleaved and offset, it will directly lead to the loss of reply code element detection and reduce the accuracy of reply decoding.

[0005] Only fixed pulse positions are sampled. When there is interleaving at the pulse sampling positions, the sampling amplitude and phase values ​​of the pulses may be distorted, the sequence consistency detection between pulses cannot pass, and the accuracy of the response decoding is reduced. Summary of the invention

[0006] The present invention aims to provide a secondary radar conventional mode reply decoding method based on the combination of amplitude and phase characteristics, so as to solve the problem that the conventional secondary radar conventional mode reply decoding method reduces the reply decoding accuracy.

[0007] The present invention provides a secondary radar conventional mode response decoding method based on the combination of amplitude and phase characteristics, comprising the following steps:

[0008] S1, the step of detecting the edge of the response pulse;

[0009] S2, the step of reply sequence frame detection and pulse position code extraction;

[0010] S3, a step of determining the response frame and pulse bit interleaving;

[0011] S4, step of extracting the amplitude and phase of the response pulse;

[0012] S5, a step of reversing the pulse amplitude of the interleaved response sequence;

[0013] S6, step of extracting amplitude and phase codes of the response sequence.

[0014] Furthermore, the step of detecting the edge of the response pulse in step S1 includes:

[0015] S11, select the three independent channels of sum channel amplitude, difference channel amplitude, sum / difference channel phase difference to perform response pulse edge detection:

[0016] (1) Using the change of the channel amplitude, the true pulse edge S_ALE of the channel and the false pulse edge S_ELE of the channel are obtained;

[0017] (2) using the change in the difference channel amplitude to determine the difference channel true pulse edge D_ALE and the difference channel false pulse edge D_ELE;

[0018] (3) The phase difference pseudo pulse edge P_ELE is obtained by using the change of the phase difference of the sum / difference channel.

[0019] S12, based on the first detected true pulse edge, removes the pseudo pulse edges that overlap within ±0.1us and the true pulse edges that are within 0.1us after the current edge position, and obtains the final pulse edge PSVEDGE output.

[0020] Furthermore, the steps of response sequence frame detection and pulse position code extraction in step S2 include:

[0021] A sliding window method is adopted, with the pulse edge PSVEDGE as the judgment basis, and the F1 / F2 frame pulse pair of the response sequence is detected at a spacing of 20.3±0.1us. Then, the F1 pulse edge is used as the starting position to determine whether there is a pulse edge PSVEDGE at the corresponding (1.45×N±0.1us) position, and the position code {C1, A1, C2, A2, C4, A4, B1, D1, B2, D2, B4, D4, SPI} of the response sequence is extracted, N=1~6, 8~13, 17, and the type of the pulse edge at the corresponding position is obtained; wherein, each response sequence includes the sum channel true pulse edge S_ALE, the difference channel true pulse edge D_ALE, the sum channel pseudo pulse edge S_ELE, the difference channel pseudo pulse edge D_ELE and the phase difference pseudo pulse edge P_ELE.

[0022] Furthermore, the validity judgment criteria of the F1 / F2 frame pulse pair are as follows:

[0023] (a) The type of F1 pulse edge is the channel true pulse edge S_ALE;

[0024] (b) The type of the F1 pulse edge is the difference channel true pulse edge D_ALE;

[0025] (c) The type of the pulse edge of F1 satisfies two of the three pseudo pulse edges: the channel pseudo pulse edge S_ELE / the difference channel pseudo pulse edge D_ELE / the phase difference pseudo pulse edge P_ELE;

[0026] (d) The type of the F2 pulse edge is the channel true pulse edge S_ALE;

[0027] (e) The type of the F2 pulse edge is the difference channel true pulse edge D_ALE;

[0028] (f) The type of the F2 pulse edge satisfies one of the three types of pseudo pulse edges: the channel pseudo pulse edge S_ELE / the difference channel pseudo pulse edge D_ELE / the phase difference pseudo pulse edge P_ELE.

[0029] Furthermore, the step of determining the response frame and pulse bit interleaving in step S3 includes:

[0030] The relative relationship between the response frames is used to determine the interleaving of the response sequences and the specific response pulse positions:

[0031] When the triggering time interval of two response frames is within 25.1us, and the leading edge interval of the interleaving pulse is within ±0.45us, it is considered that the two response frames are interleaved;

[0032] When two response frames are interleaved, it is determined whether each response pulse position is interleaved, and the depth of response pulse interleaving when the response pulse positions are interleaved.

[0033] Furthermore, the step of extracting the amplitude and phase of the response pulse in step S4 includes:

[0034] S41, a sub-step of extracting response sequence pulse information;

[0035] S42, a sub-step of extracting the reference amplitude and phase of the response sequence.

[0036] Furthermore, the sub-step of extracting the response sequence pulse information in step S41 includes:

[0037] Taking the trigger position of the F1 / F2 frame pulse pair of the response sequence as the reference, determine the leading edge of each pulse position in the response sequence, corresponding to a total of 15 pulse positions {F1, C1, A1, C2, A2, C4, A4, B1, D1, B2, D2, B4, D4, F2, SPI}; then make a judgment based on the interleaving of the current response sequence and the previous and next response sequences, and calculate the sampling position of the response sequence pulse information, that is, the time interval between the sampling point and the leading edge of the response pulse position; wherein, the sampling point range is: 0.1~0.35us;

[0038] The sampling point selection criteria are:

[0039] When there are only two interleaved response sequences, and the interleaved part is ≤ 0.25us, the center position of the non-interleaved part is selected for sampling;

[0040] When there are multiple pulse sequences interleaved, if the pre-pulse interleaving position interval + post-pulse interleaving position interval of the current response sequence is greater than 0.45us, and the pre-pulse / post-pulse interleaving width is less than 0.35us, it means that there is a non-interleaved part in the pulse of the current response sequence, and the non-interleaved part is within the range of 0.1 to 0.35us of the current pulse, and the center position of the non-interleaved part is selected for sampling;

[0041] When there are only two response sequence interleavings, and the interleaving part is greater than 0.25us, the position 0.35us from the leading edge of the current pulse is selected for sampling during pre-pulse interleaving, and the position 0.1us from the leading edge of the current pulse is selected for sampling during post-pulse interleaving;

[0042] In other cases, the current pulse center position is selected for sampling;

[0043] After selecting the sampling point position, the amplitude and phase values ​​of the pulse sum / difference channel are sampled simultaneously to obtain the sampling data of each response pulse position of the current response sequence, which is used for amplitude and phase inversion solution of the interleaved response sequence sum / difference channel.

[0044] Furthermore, the sub-step of extracting the reference amplitude and phase of the response sequence in step S42 includes:

[0045] Select one of the pulses in the F1 / F2 frame pulse pair as the reference pulse, according to the following criteria:

[0046] By default, the F1 pulse is selected as the reference pulse;

[0047] When F1 is interleaved with a certain frame and the pulse interleaving position front interval is ≤0.1us, F2 is selected as the reference pulse;

[0048] When F1 is interleaved with multiple frames, and the pre-pulse interleaving position interval + post-pulse interleaving position interval time is ≤ 0.45us, F2 is selected as the reference pulse.

[0049] Furthermore, the step of reversely solving the pulse amplitude of the interleaved response sequence in step S5 includes:

[0050] The sum / difference channels are calculated respectively using the sampled I / Q values ​​of the non-interleaved pulses to obtain the phase change rate of the sum / difference channels of the response pulse sequence;

[0051] Then, according to the pulse interleaving of the current response sequence, taking the reference pulse as the reference, considering the amplitude and phase superposition of the interleaved pulses, the reference amplitude and phase of each pulse position of the current response sequence and / or difference channel are inversely calculated;

[0052] The phase prediction is forward calculated from F1 of the frontmost frame in all detection frames and backward calculated from F2 of the last frame.

[0053] Furthermore, the step of extracting the amplitude and phase code of the response sequence in step S6 includes:

[0054] The amplitude and phase code of the reply sequence is obtained by comparing the sampled amplitude and phase of each pulse of the reply sequence received by the sum / difference channel with the inversely calculated reference amplitude and phase calculated in step S5. The specific criteria are as follows:

[0055] Amplitude condition 1: |sampling amplitude - reference pulse amplitude|≤6db;

[0056] Amplitude condition 2: |Pulse amplitude - back-calculated reference amplitude|≤6db;

[0057] Phase condition 1: |sampling phase - reference pulse phase| ≤ 10°;

[0058] Phase condition 2: |sampling phase - inverse reference phase|≤10°;

[0059] Using the above conditions for the sum / difference channel:

[0060] When the sum channel reference amplitude ≥ difference channel reference amplitude, add the weights in the following table to get the amplitude and phase weights:

[0061]

[0062] When the sum channel reference amplitude is less than the difference channel reference amplitude, the amplitude and phase weight values ​​are obtained by adding the weights in the following table:

[0063]

[0064] When the code element in the pulse position code is 1 and the amplitude-phase weight value is ≥5, the code element at this position in the current response sequence is considered to be 1; or when the amplitude-phase weight value is ≥10, the code element at this position in the current response sequence is considered to be 1. In other cases, the code element at this position in the current response sequence is considered to be 0.

[0065] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0066] In the secondary radar conventional mode reply decoding method based on the combination of amplitude and phase characteristics provided by the present invention, since the probability of the amplitudes of the sum / difference channels being simultaneously superimposed or offset is small in the case of pulse interleaving, the amplitudes of the sum / difference dual channels are respectively used as the basis for pulse detection, which can effectively improve the detection probability of the pulse; for the same reply sequence, there is a fixed rule for the phase change between pulses, and the phases of the sum / difference dual channels can be respectively used as the basis for sequence consistency detection between pulses, thereby improving the accuracy of reply decoding; according to the interleaving of the reply sequence, the sampling position of the pulse is dynamically selected, which can maximize the accuracy of the sampled amplitude and phase values; according to the interleaving of the reply pulse, the amplitude and phase of the reply pulse are calculated in combination with the sampling values ​​of the interleaved pulses of the adjacent sequences, which can maximize the restoration of the amplitude and phase characteristics of the interleaved pulse, which is used as the basis for sequence consistency detection between pulses, thereby improving the accuracy of reply decoding; using multiple amplitude and phase characteristics of the reply pulse, the weight value of the reply code element is calculated in a weight fusion manner, and the weight threshold is set to realize the logical judgment of the reply code element, thereby improving the accuracy of reply decoding. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0068] Figure 1 The present invention is a flowchart of a conventional mode response decoding method of a secondary radar based on the combination of amplitude and phase characteristics in an embodiment of the present invention.

[0069] Figure 2 Schematic diagram of pulse extraction in an embodiment of the present invention.

[0070] Figure 3 This is a schematic diagram of extracting the response framework code in an embodiment of the present invention.

[0071] Figure 4 Schematic diagram of response frame interleaving in an embodiment of the present invention.

[0072] Figure 5 Schematic diagram of response pulse interleaving in an embodiment of the present invention.

[0073] Figure 6 Schematic diagram of the amplitude and phase of the interleaved sequence in an embodiment of the present invention. DETAILED DESCRIPTION

[0074] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0075] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0076] Example

[0077] like Figure 1 As shown, this embodiment proposes a secondary radar conventional mode response decoding method based on the combination of amplitude and phase characteristics, comprising the following steps:

[0078] S1, response pulse edge detection:

[0079] S11, select the three independent channels of sum channel amplitude, difference channel amplitude, sum / difference channel phase difference to perform response pulse edge detection:

[0080] (1) Using the change of the channel amplitude, the true pulse edge S_ALE of the channel and the false pulse edge S_ELE of the channel are obtained;

[0081] (2) using the change in the difference channel amplitude to determine the difference channel true pulse edge D_ALE and the difference channel false pulse edge D_ELE;

[0082] (3) The phase difference pseudo pulse edge P_ELE is obtained by using the change of the phase difference of the sum / difference channel.

[0083] S12, such as Figure 2 As shown, based on the first detected true pulse edge, the false pulse edges with positions overlapping within ±0.1us and the true pulse edges within 0.1us after the current edge position are eliminated to obtain the final pulse edge PSVEDGE output.

[0084] Terminology Introduction:

[0085] S_ALE: Sum channel pulse detection 6dB true leading edge signal;

[0086] D_ALE: difference channel pulse detection 6dB true leading edge signal;

[0087] S_ELE: Sum channel pulse detection amplitude pseudo leading edge signal;

[0088] D_ELE: difference channel pulse detection amplitude pseudo leading edge signal;

[0089] P_ELE: Pulse detection phase difference pseudo leading edge signal;

[0090] PSVEDGE: Pulse detection leading edge signal.

[0091] S2, reply sequence frame detection and pulse position code extraction:

[0092] like Figure 3 As shown, a sliding window method is adopted, and the pulse edge PSVEDGE is used as the judgment basis. The F1 / F2 frame pulse pair of the response sequence is detected according to the interval of 20.3±0.1us, and then the F1 pulse edge is used as the starting position to judge whether there is a pulse edge PSVEDGE at the corresponding (1.45×N±0.1us) position. The position code {C1, A1, C2, A2, C4, A4, B1, D1, B2, D2, B4, D4, SPI} of the response sequence is extracted, N=1~6, 8~13, 17, and the type of the pulse edge at the corresponding position is obtained at the same time; wherein each response sequence includes the sum channel true pulse edge S_ALE, the difference channel true pulse edge D_ALE, the sum channel pseudo pulse edge S_ELE, the difference channel pseudo pulse edge D_ELE and the phase difference pseudo pulse edge P_ELE.

[0093] The validity judgment criteria of the F1 / F2 frame pulse pair are as follows:

[0094] (a) The type of F1 pulse edge is the channel true pulse edge S_ALE;

[0095] (b) The type of the F1 pulse edge is the difference channel true pulse edge D_ALE;

[0096] (c) The type of the pulse edge of F1 satisfies two of the three pseudo pulse edges: the channel pseudo pulse edge S_ELE / the difference channel pseudo pulse edge D_ELE / the phase difference pseudo pulse edge P_ELE;

[0097] (d) The type of the F2 pulse edge is the channel true pulse edge S_ALE;

[0098] (e) The type of the F2 pulse edge is the difference channel true pulse edge D_ALE;

[0099] (f) The type of the F2 pulse edge satisfies one of the three types of pseudo pulse edges: the channel pseudo pulse edge S_ELE / the difference channel pseudo pulse edge D_ELE / the phase difference pseudo pulse edge P_ELE.

[0100] S3, response frame and pulse bit interleaving judgment:

[0101] The relative relationship between the response frames is used to determine the interleaving of the response sequences and the specific response pulse positions:

[0102] When the trigger time interval of two response frames is within 25.1us (considering the SPI pulse bit), and the leading edge interval of the interleaved pulse is within ±0.45us, it is considered that the two response frames are interleaved. Figure 4 As shown, yd1 and yd2, yd1 and yd3 are intertwined respectively.

[0103] When two response frames are interleaved, determine whether each response pulse position is interleaved, and the depth of response pulse interleaving when the response pulse position is interleaved (the spacing between the leading edges of the interleaved pulse positions of the two response sequences, with a value range of ≤±0.45us).

[0104] S4, response pulse amplitude and phase extraction:

[0105] S41, answer sequence pulse information extraction:

[0106] Taking the trigger position of the F1 / F2 frame pulse pair of the response sequence as the reference, determine the leading edge of each pulse position in the response sequence, corresponding to a total of 15 pulse positions {F1, C1, A1, C2, A2, C4, A4, B1, D1, B2, D2, B4, D4, F2, SPI}; then make a judgment based on the interleaving of the current response sequence and the previous and next response sequences, and calculate the sampling position of the response sequence pulse information, that is, the time interval between the sampling point and the leading edge of the response pulse position; wherein, the sampling point range is: 0.1~0.35us;

[0107] like Figure 5 The sampling point selection criteria are as follows:

[0108] When there are only two interleaved response sequences (pre-pulse interleaving or post-pulse interleaving), and the interleaved part is ≤ 0.25us, the center position of the non-interleaved part is selected for sampling;

[0109] When there are multiple pulse sequences interleaved, if the pre-pulse interleaving position interval + post-pulse interleaving position interval of the current response sequence is greater than 0.45us, and the pre-pulse / post-pulse interleaving width is less than 0.35us, it means that there is a non-interleaved part in the pulse of the current response sequence, and the non-interleaved part is within the range of 0.1 to 0.35us of the current pulse, and the center position of the non-interleaved part is selected for sampling;

[0110] When there are only two response sequence interleavings (pre-pulse interleaving or post-pulse interleaving), and the interleaving part is greater than 0.25us, the position 0.35us from the leading edge of the current pulse is selected for sampling when the pre-pulse interleaving is performed, and the position 0.1us from the leading edge of the current pulse is selected for sampling when the post-pulse interleaving is performed;

[0111] In other cases, the current pulse center position is selected for sampling;

[0112] After selecting the sampling point position, the amplitude and phase values ​​of the pulse sum / difference channel are sampled simultaneously to obtain the sampling data of each response pulse position of the current response sequence, which is used for amplitude and phase inversion solution of the interleaved response sequence sum / difference channel.

[0113] S42, response sequence reference amplitude and phase extraction:

[0114] like Figure 5 As shown, one of the pulses in the F1 / F2 frame pulse pair is selected as the reference pulse, with the following specific criteria:

[0115] By default, the F1 pulse is selected as the reference pulse;

[0116] When F1 is interleaved with a certain frame and the pulse (front / back) interleaving position front interval is ≤0.1us, F2 is selected as the reference pulse;

[0117] When F1 is interleaved with multiple frames, and the pre-pulse interleaving position interval + post-pulse interleaving position interval time is ≤ 0.45us, F2 is selected as the reference pulse.

[0118] S5, interleaved response sequence pulse amplitude reverse solution:

[0119] Since the transponder mixer oscillator has a certain frequency jitter, generally around ±200Khz, the frequencies of the reply signals from different aircraft will vary. The frequency difference is directly reflected in the received signal as the phase change rate, such as Figure 6 As shown, the frequency difference of sequence 1 is +100Khz, and the frequency difference of sequence 2 is -100Khz.

[0120] If the current response sequence has multiple non-interleaved pulse code elements, the sampled I / Q values ​​of these non-interleaved pulses can be used to calculate the sum / difference channels respectively to obtain the phase change rate of the sum / difference channels of the response pulse sequence.

[0121] According to the pulse interleaving of the current response sequence, taking the reference pulse (F1 / F2) as the reference and considering the amplitude and phase superposition of the interleaved pulses, the reference amplitude and phase of each pulse position of the current response sequence and / or difference channel is inversely calculated.

[0122] Since the interleaving position is between two frames, the first and last pulses of the signal are not interleaved. Therefore, the phase prediction is forward calculated from F1 (reference pulse) of the first frame in all detection frames and backward calculated from F2 (reference pulse) of the last frame.

[0123] S6, answer sequence amplitude and phase code extraction:

[0124] The amplitude and phase code of the reply sequence is obtained by comparing the sampled amplitude and phase of each pulse of the reply sequence received by the sum / difference channel with the inversely calculated reference amplitude and phase calculated in step S5. The specific criteria are as follows:

[0125] Amplitude condition 1: |sampling amplitude - reference pulse amplitude|≤6db;

[0126] Amplitude condition 2: |Pulse amplitude - back-calculated reference amplitude|≤6db;

[0127] Phase condition 1: |sampling phase - reference pulse phase| ≤ 10°;

[0128] Phase condition 2: |sampling phase - inverse reference phase|≤10°;

[0129] Using the above 8 conditions of the sum / difference channel:

[0130] When the sum channel reference amplitude ≥ the difference channel reference amplitude, the amplitude and phase weight values ​​are obtained by adding the weights in Table 1.

[0131] Table 1:

[0132]

[0133] When the sum channel reference amplitude is less than the difference channel reference amplitude, the amplitude and phase weight values ​​are obtained by adding the weights in Table 2.

[0134] Table 2:

[0135]

[0136] When the code element in the pulse position code is 1 and the amplitude-phase weight value is ≥5, the code element at this position in the current response sequence is considered to be 1; or when the amplitude-phase weight value is ≥10, the code element at this position in the current response sequence is considered to be 1. In other cases, the code element at this position in the current response sequence is considered to be 0.

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A secondary radar conventional mode response decoding method based on the combination of amplitude and phase characteristics, characterized in that: The steps include: S1, the step of detecting the edge of the response pulse; S2, the step of reply sequence frame detection and pulse position code extraction; S3, a step of determining the response frame and pulse bit interleaving; S4, step of extracting the amplitude and phase of the response pulse; S5, a step of reversing the pulse amplitude of the interleaved response sequence; S6, step of extracting the amplitude and phase code of the reply sequence: using the sampling amplitude and phase of each pulse of the reply sequence received by the sum / difference channel to compare with the inversely calculated reference amplitude and phase calculated in step S5 to obtain the amplitude and phase code of the reply sequence; The step of detecting the edge of the response pulse in step S1 includes: S11, select the three independent channels of sum channel amplitude, difference channel amplitude, sum / difference channel phase difference to perform response pulse edge detection: (1) Using the change of the channel amplitude, the true pulse edge S_ALE of the channel and the false pulse edge S_ELE of the channel are obtained; (2) using the change in the difference channel amplitude to determine the difference channel true pulse edge D_ALE and the difference channel false pulse edge D_ELE; (3) using the change of the phase difference of the sum / difference channel to determine the phase difference pseudo pulse edge P_ELE; S12, taking the first detected true pulse edge as the reference, removes the pseudo pulse edge whose position overlaps within ±0.1us and the true pulse edge within 0.1us after the current edge position, and obtains the final pulse edge PSVEDGE output; The step of extracting the amplitude and phase of the response pulse in step S4 includes: S41, a sub-step of extracting response sequence pulse information; S42, a sub-step of extracting a reference amplitude and phase of a response sequence; The sub-steps of extracting the response sequence pulse information in step S41 include: Taking the trigger position of the F1 / F2 frame pulse pair of the response sequence as the reference, determine the leading edge of each pulse position in the response sequence, corresponding to a total of 15 pulse positions {F1, C1, A1, C2, A2, C4, A4, B1, D1, B2, D2, B4, D4, F2, SPI}; then make a judgment based on the interleaving of the current response sequence and the previous and next response sequences, and calculate the sampling position of the response sequence pulse information, that is, the time interval between the sampling point and the leading edge of the response pulse position; wherein, the sampling point range is: 0.1~0.35us; The sampling point selection criteria are: When there are only two interleaved response sequences, and the interleaved part is ≤ 0.25us, the center position of the non-interleaved part is selected for sampling; When there are multiple pulse sequences interleaved, if the pre-pulse interleaving position interval + post-pulse interleaving position interval of the current response sequence is greater than 0.45us, and the pre-pulse / post-pulse interleaving width is less than 0.35us, it means that there is a non-interleaved part in the pulse of the current response sequence, and the non-interleaved part is within the range of 0.1 to 0.35us of the current pulse, and the center position of the non-interleaved part is selected for sampling; When there are only two response sequence interleavings, and the interleaving part is greater than 0.25us, the position 0.35us from the leading edge of the current pulse is selected for sampling during pre-pulse interleaving, and the position 0.1us from the leading edge of the current pulse is selected for sampling during post-pulse interleaving; In other cases, the current pulse center position is selected for sampling; After selecting the sampling point position, the amplitude and phase values ​​of the sum / difference channel of the pulse are sampled simultaneously to obtain the sampling data of each response pulse position of the current response sequence, which is used for the amplitude and phase inversion solution of the sum / difference channel of the interleaved response sequence; The sub-steps of extracting the reference amplitude and phase of the response sequence in step S42 include: Select one of the pulses in the F1 / F2 frame pulse pair as the reference pulse, according to the following criteria: By default, the F1 pulse is selected as the reference pulse; When F1 is interleaved with a certain frame and the pulse interleaving position front interval is ≤0.1us, F2 is selected as the reference pulse; When F1 is interleaved with multiple frames, and the pre-pulse interleaving position interval + post-pulse interleaving position interval time is ≤ 0.45us, F2 is selected as the reference pulse.

2. The method for decoding the secondary radar conventional mode response based on the combination of amplitude and phase characteristics according to claim 1 is characterized in that: The steps of response sequence frame detection and pulse position code extraction in step S2 include: A sliding window method is adopted, with the pulse edge PSVEDGE as the judgment basis, and the F1 / F2 frame pulse pair of the response sequence is detected at a spacing of 20.3±0.1us. Then, the F1 pulse edge is used as the starting position to determine whether there is a pulse edge PSVEDGE at the corresponding (1.45×N±0.1us) position, and the position code {C1, A1, C2, A2, C4, A4, B1, D1, B2, D2, B4, D4, SPI} of the response sequence is extracted, N=1~6, 8~13, 17, and the type of the pulse edge at the corresponding position is obtained; wherein, each response sequence includes the sum channel true pulse edge S_ALE, the difference channel true pulse edge D_ALE, the sum channel pseudo pulse edge S_ELE, the difference channel pseudo pulse edge D_ELE and the phase difference pseudo pulse edge P_ELE.

3. The method for decoding the secondary radar conventional mode response based on the combination of amplitude and phase characteristics according to claim 2 is characterized in that: The validity criteria for the F1 / F2 frame pulse pair are as follows: (a) The type of F1 pulse edge is the channel true pulse edge S_ALE; (b) The type of the F1 pulse edge is the difference channel true pulse edge D_ALE; (c) The type of the pulse edge of F1 satisfies two of the three pseudo pulse edges: the channel pseudo pulse edge S_ELE / the difference channel pseudo pulse edge D_ELE / the phase difference pseudo pulse edge P_ELE; (d) The type of the F2 pulse edge is the channel true pulse edge S_ALE; (e) The type of the F2 pulse edge is the difference channel true pulse edge D_ALE; (f) The type of the F2 pulse edge satisfies one of the three types of pseudo pulse edges: the channel pseudo pulse edge S_ELE / the difference channel pseudo pulse edge D_ELE / the phase difference pseudo pulse edge P_ELE.

4. The method for decoding the secondary radar conventional mode response based on the combination of amplitude and phase characteristics according to claim 3 is characterized in that: The step of answering the frame and pulse bit interleaving judgment in step S3 includes: The relative relationship between the response frames is used to determine the interleaving of the response sequences and the specific response pulse positions: When the triggering time interval of two response frames is within 25.1us, and the leading edge interval of the interleaving pulse is within ±0.45us, it is considered that the two response frames are interleaved; When two response frames are interleaved, it is determined whether each response pulse position is interleaved, and the depth of response pulse interleaving when the response pulse positions are interleaved.

5. The method for decoding the secondary radar conventional mode response based on the combination of amplitude and phase characteristics according to claim 4 is characterized in that: The step of reversely calculating the pulse amplitude of the interleaved response sequence in step S5 includes: The sum / difference channels are calculated respectively using the sampled I / Q values ​​of the non-interleaved pulses to obtain the phase change rate of the sum / difference channels of the response pulse sequence; Then, according to the pulse interleaving of the current response sequence, taking the reference pulse as the reference, considering the amplitude and phase superposition of the interleaved pulses, the reference amplitude and phase of each pulse position of the current response sequence and / or difference channel are inversely calculated; The phase prediction is forward calculated from F1 of the frontmost frame in all detection frames and backward calculated from F2 of the last frame.

6. The method for decoding secondary radar conventional mode responses based on the combination of amplitude and phase characteristics according to claim 1 is characterized in that: The step of extracting the amplitude and phase code of the response sequence in step S6 includes: The amplitude and phase code of the reply sequence is obtained by comparing the sampled amplitude and phase of each pulse of the reply sequence received by the sum / difference channel with the inversely calculated reference amplitude and phase calculated in step S5. The specific criteria are as follows: Amplitude condition 1: |sampling amplitude - reference pulse amplitude|≤6db; Amplitude condition 2: |Pulse amplitude - back-calculated reference amplitude|≤6db; Phase condition 1: |sampling phase - reference pulse phase| ≤ 10°; Phase condition 2: |sampling phase - inverse reference phase|≤10°; Using the above conditions for the sum / difference channel: When the sum channel reference amplitude ≥ difference channel reference amplitude, add the weights in the following table to get the amplitude and phase weights: When the sum channel reference amplitude is less than the difference channel reference amplitude, the amplitude and phase weight values ​​are obtained by adding the weights in the following table: When the code element in the pulse position code is 1 and the amplitude-phase weight value is ≥5, the code element at this position in the current response sequence is considered to be 1; or when the amplitude-phase weight value is ≥10, the code element at this position in the current response sequence is considered to be 1. In other cases, the code element at this position in the current response sequence is considered to be 0.

Images