A method for determining and suppressing multipath signals

Abstract

The application relates to a multi-path signal judging and suppressing method, and relates to the technical field of electronic reconnaissance.The signal envelope is calculated according to IQ data, and the direct signal and the reflected signal are obviously different in amplitude, so that the envelope of the signal is obviously stepped; the amplitude and the delay of the multi-path signal are estimated, and the sampling IQ data, the data envelope and the time phase curve are taken as an example of a simple pulse signal; the reflected signal is eliminated from the received signal according to the amplitude and the delay of the reflected signal, and the remaining component is the direct signal, the intra-pulse analysis can be carried out, and the intra-pulse modulation type identification error probability is reduced.

Description

Technical Field

[0001] This invention relates to the field of electronic reconnaissance technology, and in particular to a method for multipath signal identification and suppression. Background Technology

[0002] Intra-pulse modulation type identification (IPC) of radar signals is a crucial component of modern electronic reconnaissance systems, and accurate IPC identification is paramount. Currently, due to the deployment environment and the inherent structure of the radar equipment, multipath propagation occurs in the signals received by reconnaissance equipment. In certain situations, the radar's main beam not only directly illuminates the target object but also simultaneously illuminates the receiving antenna. In this case, the receiving antenna receives both the direct main beam signal and the signal reflected from the reflecting object. This dual signal reception complicates signal processing, requiring the differentiation and handling of direct and reflected signals—i.e., multipath signals. Multipath signals affect the pulse width in IPC identification. Furthermore, conventional and FM signals are often misidentified as phase-coded signals; and for phase-coded signals, their coding patterns cannot be correctly identified. Therefore, effectively identifying and suppressing multipath signals is a critical technical problem that needs to be addressed in this case. Summary of the Invention

[0003] To address the above problems, this invention provides a method for accurately and efficiently identifying and suppressing multipath signals.

[0004] The technical solution of this invention is:

[0005] A method for multipath signal identification and suppression, comprising:

[0006] Step 1: Acquire IQ data and calculate the envelope to obtain the signal envelope;

[0007]

[0008] Where a(t) represents the pulse envelope function, I represents the I-axis component of the radar signal, and Q represents the Q-axis component of the radar signal;

[0009] The phase relationship between the reflected signal and the direct signal can be obtained from the rising edge, falling edge, and changes in the amplitude of the obtained signal envelope.

[0010] Step 2: Based on the number and order of rising and falling edges detected by the signal envelope, determine the quadrant and amplitude of the phase of the reflected signal relative to the direct signal; select the appropriate rising or falling edge accordingly, and calculate the coarse estimate of the delay tx of the reflected signal relative to the direct signal.

[0011] Reflected signals include radar signals that are reflected off other objects and reach the receiving antenna of the reconnaissance equipment.

[0012] Direct signals include radar signals that are directly reflected on the receiving antenna of the reconnaissance equipment;

[0013] Coarse estimate of delay t x The calculation includes rising and falling edge detection: if for t r Envelope data at time [t] r / f0,t r +8 / f0】Nine consecutive envelope values ​​greater than [t] r -8 / f0,t r The envelope of ' / f0', then t r The time is the rising edge;

[0014] If for t d Envelope data at time [t] d / f0,t d +8 / f0】Nine consecutive envelope values ​​less than [t] d -8 / f0,t d The envelope of ' / f0', then t d The time is the falling edge;

[0015] t r Indicates the rising edge of the signal, t d f0 represents the falling edge of the signal, and f0 represents the carrier frequency of the signal.

[0016] Step 3: Calculate the estimated delay t of the reflected signal using the enumeration method. z ;

[0017] If the estimated delay value of the reflected signal is t z Located in [t] x -1 / f0,t x When +1 / f0 is reached, the range of values ​​is divided into n segments (n is an integer not less than 1, and 720 segments are used in this case), resulting in n+1 enumerated values; where f0 is the signal carrier frequency.

[0018] The detection errors of the rising and falling edges are caused by discrete sampling. The actual rising edge lies between two sampling points. Regardless of whether the previous or subsequent sampling point is used, there will be a certain deviation in the rising edge, but it will not exceed one sampling period. Therefore, the calculated delay error will not exceed ±2 times the sampling period. According to the Nyquist sampling theorem, the sampling frequency is generally more than twice the signal frequency. Therefore, the carrier frequency period 1 / f0 is more than twice the sampling period, so t z It should be in the [t] position x -1 / f0,t x The range is +1 / f0.

[0019] A composite signal is a multipath signal that combines the direct and reflected signals detected by radar. To analyze the parameters of the radar signal, the direct and reflected signals need to be separated. If the direct and reflected signals are considered as vectors rotating according to the carrier frequency, the amplitude of the reflected signal is smaller than that of the direct signal. The reflected signal will inevitably lag behind the direct signal in time. The amplitude of the composite signal is the amplitude of the vector sum of the direct and reflected signals when they overlap in time, which is determined by the amplitude of the direct signal, the amplitude of the reflected signal, and the phase difference between them.

[0020] The envelope represents the amplitudes of the direct signal, the composite signal, and the reflected signal at each moment. This case uses the rising and falling edges of the envelope to determine the time periods with only the direct signal, the time periods with both direct and reflected signals (i.e., the composite signal), and the time periods with only the reflected signal. Because the envelope is discrete data, the detection of the rising and falling edges has a certain error; only the lag time t of the reflected signal relative to the direct signal can be roughly calculated. x At this point, the error in the lag time does not exceed one carrier period 1 / f0. Therefore, the accurate reflected signal delay t z It should be in the [t] position x -1 / f0,t x Within the range of +1 / f0, [t] x -1 / f0,t x [+1 / f0] Divide the time range into n segments to obtain n+1 enumerated time t. z .

[0021] Step 4: Use the enumerated values ​​as delay t in sequence. B (The n+1 enumerated values ​​are the delay estimates t) z , in turn as t B Find the (n+1) groups of direct signals I′ containing noise components. A and Q′ A The formula is as follows:

[0022] Where a(t) is the pulse envelope function, k B The amplitude ratio of the reflected signal to the direct signal is given by t, where t is the sampling time, and Ic and Q are also given. C These are the orthogonal components of the synthesized signal.

[0023] H is the delay matrix of the reflected signal relative to the direct signal:

[0024]

[0025] E is the identity matrix:

[0026]

[0027] Step 5, calculate all I′A With Q′ A The mean square error of the envelope and pulse portion;

[0028] Step 6: Compare the mean square errors of n+1 groups. The one with the smallest mean square error is the correct delay t. B I A 'and Q A ', I A 'and Q A The separated direct signal can be used for signal processing such as intrapulse analysis.

[0029] Specifically, step two includes:

[0030] Scenario 1: When two consecutive rising edges are detected first, followed by two consecutive falling edges, resulting in a state where the middle is high and the two sides are low;

[0031] The signal between the first rising edge and the second rising edge is the direct signal, the signal between the second rising edge and the first falling edge is the composite signal, and the signal between the first falling edge and the second falling edge is the reflected signal. Based on this, the amplitudes of the direct signal, the reflected signal, the composite signal, and the time interval tx between the two falling edges can be calculated.

[0032] Specifically, step two includes: Case two:

[0033] First, a rising edge is detected, then three falling edges are detected in succession, presenting three falling steps, and the amplitude value of the third step is greater than half of the first step;

[0034] The signal between the first rising edge and the first falling edge is the direct signal, the signal between the first falling edge and the second falling edge is the composite signal, and the signal between the second falling edge and the third falling edge is the reflected signal. Based on this, the amplitudes of the direct signal, the reflected signal, and the composite signal are calculated. Then, the time interval tx between the second and third falling edges or tx between the first rising edge and the first falling edge is calculated.

[0035] Specifically, step two includes:

[0036] Scenario 3: First a rising edge is detected, then a falling edge is detected, then another rising edge is detected, and finally a falling edge is detected, showing a pattern of high on both sides and low in the middle;

[0037] The signal between the first rising edge and the first falling edge is the direct signal, the signal between the first falling edge and the second rising edge is the composite signal, and the signal between the second rising edge and the second falling edge is the reflected signal. Based on this, the amplitudes of the direct signal, the reflected signal, the composite signal, and the time interval tx between the first rising edge and the first falling edge can be calculated.

[0038] Specifically, step two includes:

[0039] Case 4: First, a rising edge is detected, followed by three consecutive falling edges, forming three falling steps, and the amplitude of the third step is less than half of the first step.

[0040] The signal between the first rising edge and the first falling edge is the direct signal, the signal between the first falling edge and the second falling edge is the composite signal, and the signal between the second falling edge and the third falling edge is the reflected signal. Based on this, the amplitudes of the direct signal, the reflected signal, and the composite signal are calculated. Then, the time interval tx between the second and third falling edges or the time interval between the first rising edge and the first falling edge is calculated.

[0041] Specifically, in step three:

[0042] If the reflected signal is delayed by t z Located in [t] x -1 / f0,t x +1 / f0】, the range of values ​​is divided into 720 segments, resulting in 721 enumerated values.

[0043] This invention calculates the signal envelope based on IQ data. The direct signal and the reflected signal have significant differences in amplitude, resulting in a distinct stepped shape in the signal envelope. The amplitude and delay of the multipath signal are estimated. Taking a simple pulse signal as an example, IQ data, data envelope, and timing curve are sampled. Based on the amplitude and delay of the reflected signal, it is eliminated from the received signal. The remaining component is the direct signal, which can be used for intra-pulse analysis, thereby reducing the probability of incorrect intra-pulse modulation type identification. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the process of this invention;

[0045] Figure 2 It is a graph of sampled IQ data;

[0046] Figure 3 It is a sampled data envelopment data graph;

[0047] Figure 4 It is the complete pulse portion in the phase curve;

[0048] Figure 5 This is a magnified view of a portion of the phase curve;

[0049] Figure 6 This is a vector diagram of direct and reflected signals in scenario one;

[0050] Figure 7 This is the envelope diagram for case 1;

[0051] Figure 8 This is the vector diagram of direct and reflected signals in scenario two;

[0052] Figure 9 Case 2 envelope Figure 2 ;

[0053] Figure 10 This is the vector diagram of direct and reflected signals in case three;

[0054] Figure 11 This is a case-three envelope diagram;

[0055] Figure 12 This is the vector diagram of direct and reflected signals in case four;

[0056] Figure 13 This is the envelope diagram for case four;

[0057] Figure 14 It is the signal envelope diagram in the actual simulation;

[0058] Figure 15 This is a diagram of transition points in the actual simulation;

[0059] Figure 16 It is a time-frequency curve from the actual simulation;

[0060] Figure 17 It is a variance plot of the pulse portion of the signal after reflection cancellation at different delays in actual simulation;

[0061] Figure 18 It is a phase diagram from an actual simulation. Detailed Implementation

[0062] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0063] The following is for reference. Figure 1-18 Describe the present invention;

[0064] Determining pulse width and phase coding type by analyzing the rising edge, falling edge, and phase curve of a signal is one of the main methods for automatic identification of intra-pulse modulation types in radar signals. When there is no or minimal multipath signal influence, a pulse has only one rising edge and one falling edge. Simple pulse signals and frequency-modulated signals exhibit continuous phase changes without transition points. Phase-coded signals, however, have phase transition points in their phase curves. The amplitude differences of multipath signals result in multiple rising and falling edges. Therefore, these patterns can be used to estimate the amplitude and delay of multipath signals.

[0065] Taking a simple pulse signal as an example, such as Figures 2-5As shown, the AD chip is used to sample IQ data, sample data envelopment, and timing curves; based on the amplitude and delay of the reflected signal, it is eliminated from the received signal, and the remaining component is the direct signal, which can be used for intra-pulse analysis.

[0066] This invention first determines the quadrant and amplitude of the reflected signal relative to the direct signal's phase based on the number and order of rising and falling edges. Appropriate rising and falling edges are then selected to calculate a coarse estimate of the delay. Finally, the accurate delay value is calculated by combining the zero-crossing time difference, the amplitude of each step, and the frequency.

[0067] The mathematical expression for a multipath signal is:

[0068] in, For the received multipath signal; It is a direct signal component; The reflected signal component; For the sake of analysis, we will use a simple pulse signal as an example, which represents white noise components:

[0069]

[0070] In the above formula, f0 is the signal carrier frequency. Let a(t) be the initial phase of the signal, and a(t) be the pulse envelope function. B where t is the delay time, a is the sampling time, e is the pulse envelope, and j is the imaginary number.

[0071] k B k is the amplitude ratio of the reflected signal to the direct signal. B <1.

[0072] When the pulse envelope is a rectangular pulse: a(t) = a m Rect(t / τ0),

[0073] a m τ is the pulse amplitude, and τ0 is the pulse width.

[0074] and It can be converted into the following expression:

[0075]

[0076]

[0077] Assumption

[0078]

[0079] Among them, I A QA For the orthogonal components of the direct signal; I B and Q B These are the orthogonal components of the reflected signal;

[0080] It can be known

[0081]

[0082] Therefore, we can conclude that:

[0083]

[0084] Where I′ A Q′ A For a direct signal containing orthogonal components of white noise, I w Q w These are the orthogonal components of white noise, and Ic and Qc are the orthogonal components of the synthesized signal;

[0085]

[0086] H is the delay matrix of the reflected signal relative to the direct signal;

[0087] E is the identity matrix;

[0088] Therefore, the amplitude ratio k between the reflected signal and the direct signal can be calculated from the envelope of the received signal. B Delay time t B Pulse width τ0 and pulse amplitude a m Then, the direct signal containing white noise can be obtained according to the above formula. B t B The range of values ​​for k is different. B t B , τ0 and a m The methods are also different.

[0089] I' A Q′ A It is a direct signal containing white noise, but represented by orthogonal signals.

[0090]

[0091] t B It consists of n carrier periods and a non-complete period. For the complete carrier period, its phase can be calculated by n·2π, and the phase of the non-complete period is calculated by... This indicates that the total phase lag of the reflected signal relative to the direct signal is...

[0092] Example 1:

[0093] When it is case one, the vector diagrams of the direct signal and the reflected signal are as follows: Figure 6 As shown;

[0094] The amplitude ratio k of the reflected signal to the direct signal B <1;

[0095]

[0096] It is the angle between the direct signal vector and the reflected signal vector.

[0097] In the diagram, A is the vector of the direct signal; B1 to Bn are vectors of reflected signals with the same amplitude but different phases; C1 to Cn are composite vectors, where |C1 to Cn|>|A|.

[0098]

[0099] Where θ is the angle between vectors A and B, and B∈(B1,...,Bn);

[0100] C1 and Cn are the boundaries, and their amplitudes are equal to the amplitude of A. Within this range, the envelope of the received signal is as follows: Figure 7 As shown;

[0101] In the figure, t1 is the rising edge of the direct signal pulse, t2 is the rising edge of the reflected signal pulse, t3 is the falling edge of the direct signal pulse, and t4 is the falling edge of the reflected signal pulse. AMP a For direct signal amplitude, AMP b For the amplitude of the reflected signal, AMP c The amplitude of the combined signal; the ratio of the amplitude of the reflected signal to the amplitude of the direct signal: Pulse width: τ0 = t3 - t1

[0102] Pulse amplitude a m =AMP a

[0103] t x =t4-t3;

[0104]

[0105] Among them, t x For the delay time, t B A rough estimate, t is an enumerated value for the total phase lag of the reflected signal relative to the direct signal. y For t x With t B The enumerated value of the deviation, t z For t B The enumerated values ​​of the estimated values.

[0106] t y according to The step will have at least 721 t groups z Assigned to t in sequence B Then calculate Find its envelope, then find the sum of variances of the impulse portion (t1 to t3), and compare the 721 sums of variances. The one with the smallest sum of variances is the correct t. B as well as

[0107] Example 2:

[0108] Case 2: Direct and reflected signal vector diagrams as shown below Figure 8 As shown;

[0109] The amplitude ratio k of the reflected signal to the direct signal B >0.5;

[0110]

[0111] Where A is the vector of the direct signal; B1~Bq1, Bn~Bqn are vectors of reflected signals with the same amplitude but different phases; C1~Cq1, Cn~Cqn are composite vectors.

[0112]

[0113] C1 and Cn are boundaries, and their amplitudes are equal to the amplitude of A; Cq1 and Cqn are boundaries, and their amplitudes are equal to the amplitude of B. The envelope of the received signal within this range is as follows: Figure 9 As shown;

[0114] Figure 9 In the AMP diagram, t1 is the rising edge of the direct signal pulse, t2 is the rising edge of the reflected signal pulse, t3 is the falling edge of the direct signal pulse, and t4 is the falling edge of the reflected signal pulse. a For direct signal amplitude, AMP b For the amplitude of the reflected signal, AMP c Let be the amplitude of the combined signal. And there exist t2<(t1+t4) / 2, t3>(t1+t4) / 2.

[0115]

[0116] a m =AMP a

[0117] When B is close to Bn or B1, AMP c With AMP a The values ​​are relatively close, and the difference is less than the threshold for determining a step change. In this case, t2 cannot be detected normally.

[0118] τ0=t3-t1

[0119] t x =t4-t3

[0120] When B is close to Bqn or Bq1, AMP c With AMP b The values ​​are relatively close, and the difference is less than the threshold for determining a step change. In this case, t3 cannot be detected normally.

[0121] τ0=t4-t2

[0122] t x =t2-t1

[0123] Then we can ask:

[0124]

[0125] t y according to The step will have at least 721 t groups z Assigned to t in sequence B Then calculate Find its envelope, then find the sum of variances of the impulse portion (t1 to t3), and compare the 721 sums of variances. The one with the smallest sum of variances is the correct t. B as well as

[0126] Example 3:

[0127] Case 3: Direct signal and reflected signal vector diagrams, as shown below. Figure 10 As shown;

[0128] k B >0.5; Where A is the vector of the direct signal; Bq1 to Bqn are vectors of reflected signals with the same amplitude but different phases; and Cq1 to Cqn are composite vectors.

[0129]

[0130] Cq1 and Cqn are the boundaries, and their amplitudes are equal to the amplitude of B. Within this range, the envelope of the received signal is as follows: Figure 11 As shown;

[0131] In the diagram, t1 is the rising edge of the direct signal pulse, t2 is the rising edge of the reflected signal pulse, t3 is the falling edge of the direct signal pulse, and t4 is the falling edge of the reflected signal pulse. AMP a For direct signal amplitude, AMP b For the amplitude of the reflected signal, AMP c For the combined signal amplitude,

[0132] τ0=t4-t2

[0133] a m =AMP a

[0134] t x =t2-t1

[0135]

[0136] t y according to The step will have at least 721 t groups z Assigned to t in sequence B Then calculate Find its envelope, then find the sum of variances of the impulse portion (t1 to t3), and compare the 721 sums of variances. The one with the smallest sum of variances is the correct t. B as well as

[0137] Example 4:

[0138] The vector diagrams for direct and reflected signals in case four are as follows: Figure 12 As shown;

[0139] k B <0.5; Where A is the vector of the direct signal; B1 to Bn are vectors of reflected signals with the same amplitude but different phases; C1 to Cn are composite vectors.

[0140]

[0141] C1 and Cn are the boundaries, and their amplitudes are equal to the amplitude of A. Within this range, the envelope of the received signal is as follows: Figure 13 As shown;

[0142] In the diagram, t1 is the rising edge of the direct signal pulse, t2 is the rising edge of the reflected signal pulse, t3 is the falling edge of the direct signal pulse, and t4 is the falling edge of the reflected signal pulse. AMP a For direct signal amplitude, AMP b For the amplitude of the reflected signal, AMP c Let be the amplitude of the combined signal. And there exist t2<(t1+t4) / 2, t3>(t1+t4) / 2.

[0143]

[0144] a m =AMP a

[0145] When B is close to Bn or B1, AMP c With AMP aThe values ​​are relatively close, and the difference is less than the threshold for determining a step change. In this case, t2 cannot be detected normally.

[0146] τ0=t3-t1

[0147] t x =t4-t3

[0148] B is close to π and AMP c With AMP b When the values ​​are close, and the difference is less than the threshold for determining a step, t3 cannot be detected normally. In this case:

[0149] τ0=t4-t2

[0150] t x =t2-t1

[0151] Then we can ask:

[0152]

[0153] t y according to The step will have at least 721 t groups z Assigned to t in sequence B Then calculate Find its envelope, then find the sum of variances of the impulse portion (t1 to t3), and compare the 721 sums of variances. The one with the smallest sum of variances is the correct t. B as well as

[0154] The actual simulation results are presented below:

[0155] This invention uses a simple pulse signal with an intermediate frequency of 10MHz, a pulse width of 5µs, and an amplitude of 10000 for simulation, with a sampling rate of 120MHz. It assumes an amplitude ratio of 0.4 between the reflected and direct signals, a delay of 1.4µs, and a maximum white noise amplitude of 1000. Sampling IQ data, data envelopment curves, and timing curves are shown below. Figure 2-5 As shown.

[0156] The rising and falling edges can be identified from the envelope diagram, such as... Figure 14-15 As shown, the search retrieves regions with a jump variable greater than 1500, with each region corresponding to a rising or falling edge. Peak points are then retrieved within each region.

[0157] Rising edge sampling point number: 300;

[0158] Falling edge sampling point numbers: 901, 1025.

[0159] It can be known

[0160]

[0161] t2 = t1 + t4 - t3 = 3.534us

[0162] Undetected rising edge number: 424.

[0163] AMP a The envelope between t1 and t2, and its average value:

[0164]

[0165] AMP b The envelope between t3 and t4, with its average value:

[0166]

[0167] AMP c The envelope between t2 and t3, and its average value:

[0168]

[0169] It can be seen that this simulation case meets condition four.

[0170] τ0=t3-t1=5us

[0171] t x =t4-t3=1.034us

[0172] The time-frequency curve can be derived from the phase, as follows: Figure 16 As shown; the variance of the pulse portion after eliminating the reflected signal according to different delays is as follows: Figure 17 As shown, the variance is minimized when the delay value is 1.03889 μs. After eliminating the pulse IQ data, the pulse data envelopment and timing curves are obtained. It can be seen that the phase is continuous without abrupt changes, and the method can effectively identify and suppress multipath signals.

[0173] Regarding the information disclosed in this case, the following points need to be clarified:

[0174] (1) The accompanying drawings of the embodiments disclosed in this case only involve the structures involved in the embodiments disclosed in this case. Other structures can be referred to the general design.

[0175] (2) Where there is no conflict, the embodiments and features disclosed in this case can be combined with each other to obtain new embodiments;

[0176] The above are merely specific embodiments disclosed in this case, but the scope of protection of this disclosure is not limited thereto. The scope of protection disclosed in this case shall be determined by the scope of protection of the claims.

Claims

1. A method for multipath signal identification and suppression, characterized in that, include: Step 1: Acquire IQ data and calculate the envelope to obtain the signal envelope; ； Where a(t) represents the pulse envelope function, I represents the I-axis component of the radar signal, and Q represents the Q-axis component of the radar signal; Step 2: Based on the number and order of rising and falling edges detected by the signal envelope, determine the quadrant and amplitude of the phase of the reflected signal relative to the direct signal; select the appropriate rising or falling edge accordingly, and calculate the coarse estimate of the delay tx of the reflected signal relative to the direct signal. Step 3: Calculate the estimated delay t of the reflected signal using the enumeration method. z ; If the estimated delay value of the reflected signal is t z Located in [t] x -1 / f0,t x When +1 / f0 is reached, the range of values ​​is divided into n segments, resulting in n+1 enumerated values; where f0 is the signal carrier frequency. Step 4: Use the enumerated values ​​as delay t in sequence. B Find the (n+1) groups of direct signals containing noise components. and The formula is as follows: ; in, For pulse envelope function, The amplitude ratio of the reflected signal to the direct signal is given by Ic, where t is the sampling time. These are the orthogonal components of the synthesized signal; H is the delay matrix of the reflected signal relative to the direct signal: ； E is the identity matrix: ； Step 5, calculate all I A 'With Q A The mean square error of the envelope and pulse portion of '. Step 6: Compare the mean square errors of n+1 groups. The one with the smallest mean square error is the correct delay t. B I A 'and Q A ';I A 'and Q A The separated direct signal can be used for intrapulse analysis signal processing; Step two includes: Scenario 1: When two consecutive rising edges are detected first, followed by two consecutive falling edges, resulting in a state where the middle is high and the two sides are low; The signal between the first rising edge and the second rising edge is the direct signal, the signal between the second rising edge and the first falling edge is the composite signal, and the signal between the first falling edge and the second falling edge is the reflected signal. Based on this, the amplitudes of the direct signal, the reflected signal, the composite signal, and the time interval tx between the two falling edges can be calculated. Scenario 2: First, a rising edge is detected, followed by three consecutive falling edges, forming three falling steps, and the amplitude of the third step is greater than half of the first step. The signal between the first rising edge and the first falling edge is the direct signal, the signal between the first falling edge and the second falling edge is the composite signal, and the signal between the second falling edge and the third falling edge is the reflected signal. Based on this, the amplitudes of the direct signal, the reflected signal, and the composite signal are calculated. Then, the time interval tx between the second and third falling edges or tx between the first rising edge and the first falling edge is calculated. Scenario 3: First a rising edge is detected, then a falling edge is detected, then another rising edge is detected, and finally a falling edge is detected, showing a pattern of high on both sides and low in the middle; The signal between the first rising edge and the first falling edge is the direct signal, the signal between the first falling edge and the second rising edge is the composite signal, and the signal between the second rising edge and the second falling edge is the reflected signal. Based on this, the amplitudes of the direct signal, the reflected signal, the composite signal, and the time interval tx between the first rising edge and the first falling edge can be calculated. Case 4: First, a rising edge is detected, followed by three consecutive falling edges, forming three falling steps, and the amplitude of the third step is less than half of the first step. The signal between the first rising edge and the first falling edge is the direct signal, the signal between the first falling edge and the second falling edge is the composite signal, and the signal between the second falling edge and the third falling edge is the reflected signal. Based on this, the amplitudes of the direct signal, the reflected signal, and the composite signal are calculated. Then, the time interval tx between the second and third falling edges or the time interval between the first rising edge and the first falling edge is calculated.

2. The method for multipath signal judgment and suppression according to claim 1, characterized in that, In step three: If the reflected signal is delayed by t z Located in [t] x -1 / , t x +1 / The range of values ​​is divided into 720 segments, resulting in 721 enumerated values.

3. The method for multipath signal judgment and suppression according to claim 1, characterized in that, The obtained signal envelope includes the phase relationship between the reflected signal and the direct signal obtained from the rising edge, falling edge, and changes in the amplitude of the envelope.

4. The method for multipath signal identification and suppression according to claim 1, characterized in that, Reflected signals include radar signals that are reflected off other objects and reach the receiving antenna of the reconnaissance equipment. Direct signals include radar signals that are directly reflected on the receiving antenna of the reconnaissance equipment.

5. The method for multipath signal identification and suppression according to claim 1, characterized in that, Coarse estimate of delay t x The calculation includes rising and falling edge detection: if for t r Envelope data at time [t] r / f0,t r +8 / f0】Nine consecutive envelope values ​​greater than [t] r -8 / f0,t r The envelope of / f0】, then t r The time is the rising edge; If for t d Envelope data at time [t] d / f0,t d +8 / f0】Nine consecutive envelope values ​​less than [t] d -8 / f0,t d The envelope of ' / f0', then t d The time is the falling edge; t r Indicates the rising edge of the signal, t d f0 represents the falling edge of the signal, and f0 represents the carrier frequency of the signal.

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