A foil anti-interference method based on FPGA for LFMCW millimeter wave fuze

Abstract

The present application relates to a kind of foil interference resistance method for LFMCW millimeter wave fuze based on FPGA, to solve the failure mode such as " early explosion " that current millimeter wave fuze can appear under foil interference possibly.The received difference frequency echo signal is first sampled, analog-digital conversion is completed, the two signals collected are synchronously controlled and FIFO buffer by synchronous pulse, then FIR digital filtering is carried out, then the polarization ratio average of output signal is calculated, whether foil interference is detected at this time is judged;If foil interference exists, then one of the signals is processed by oblique projection polarization filtering, then frequency spectrum analysis is completed, and the distance information of effective target is output;If the detection result does not exist foil interference, then directly carry out frequency spectrum analysis, and obtain the distance information of target.Finally, range determination is carried out to distance, when target is in the distance range of fuze detection system, output execution level signal.

Description

Technical Field

[0001] This invention belongs to the field of fuze anti-interference technology, specifically relating to an FPGA-based anti-foil interference method for LFMCW millimeter-wave fuzes. Background Technology

[0002] As a type of proximity fuse, radio fuses have advantages such as long detection range, high ranging accuracy, and high target recognition rate. In recent years, in order to improve the accuracy of proximity fuses, the application frequency band of radio fuses has gradually developed towards millimeter waves. However, millimeter wave fuses are prone to failure modes such as "premature detonation" under chaff interference. The occurrence of chaff interference greatly affects the performance of missile-borne fuses. Therefore, it is urgent to improve the ability of millimeter wave fuses to resist chaff interference.

[0003] Currently, anti-chaff interference technologies can be broadly categorized into six types: (1) identification methods based on echo signal waveform characteristics; (2) identification methods based on echo signal time-domain characteristics; (3) identification methods based on echo signal frequency-domain characteristics; (4) identification methods based on echo signal Doppler characteristics; (5) identification methods based on polarization domain information; and (6) identification methods based on composite guidance. Polarization characteristics reflect the inherent physical properties of the target, providing more target information for the fuze. Utilizing the difference in polarization characteristics between the target and the interference can further improve the fuze's ability to identify and suppress interference.

[0004] However, existing research on using polarization information to combat chaff interference only considers the case where the target and chaff interference are both within the detection range of the fuze, and lacks hardware implementation verification. Summary of the Invention

[0005] To address the impact of foil interference on LFMCW millimeter-wave fuses, this invention proposes an FPGA-based anti-foil interference method for LFMCW millimeter-wave fuses.

[0006] The technical solution of the present invention to solve the above problems is:

[0007] A method for resisting chaff interference in LFMCW millimeter-wave fuzes based on FPGA, characterized by comprising the following steps:

[0008] 1) AD acquisition data output

[0009] The analog-to-digital conversion is completed by sampling the difference frequency echo signals of the horizontal and vertical polarization channels using an ADC.

[0010] 2) Synchronization pulse

[0011] Synchronization control of the two acquired echo signals is achieved using synchronization pulses;

[0012] 3) FIFO buffer and FIR digital filtering

[0013] The two echo signals controlled by the synchronization pulse are buffered in a FIFO, and then the filter is designed using the FIR IP core.

[0014] 4) Polarization recognition

[0015] 4.1) Utilization To calculate the polarization ratio of the i-th echo signal in step 3), where A HH and A HV The amplitudes of the two echo signals are represented by i = 1, 2, ..., N, where N is the number of statistical echo signals.

[0016] 4.2) After calculating the polarization ratio of N echo signals, calculate their mean and determine whether the mean is greater than the discrimination threshold of the mean polarization ratio. The threshold is different for different aircraft targets. In practical applications, the mean polarization ratio of the aircraft needs to be determined in advance. The calculation method is the same as step 4.1), and this mean is used as the discrimination threshold of the mean polarization ratio.

[0017] 4.3) When the average polarization ratio of the echo signal is less than or equal to the discrimination threshold, it is determined that there is chaff interference, and it is necessary to process the chaff interference signal to suppress it, and proceed to step 5; when the average value is greater than the discrimination threshold, it is determined that there is only an aircraft target, and the target distance information can be directly analyzed and proceed to step 6.

[0018] 5) Oblique projection polarization filtering

[0019] 5.1) The echo signal that has been determined to have foil interference after polarization identification is used as the input signal. The input signal is the echo signal of the dual-polarized fuse. First, the polarization angle γ of the echo signal is calculated using the following formula. J The difference φ between the polarization angles J Polarization parameters are estimated to determine the polarization state of the foil:

[0020]

[0021] φ J =arg[E JV (t)]-arg[E JH (t)]

[0022] Among them, E JV (t) represents the echo signal amplitude of the vertically polarized channel, E JH (t) represents the amplitude of the echo signal in the horizontally polarized channel, and arg[g] represents the phase angle of the signal.

[0023] The polarization state of the aircraft target needs to be determined in advance for practical applications. The calculation method is the same as that in step 5.1) for calculating the polarization state of the chaff, and the aircraft polarization angle γ can also be obtained. S and the phase difference of the aircraft polarization angle φ S ;

[0024] 5.2) The oblique projection operator is calculated using the following formula based on the polarization parameters estimated in step 5.1):

[0025]

[0026]

[0027]

[0028] Among them, [g] T The transpose operation for a matrix is ​​represented by [g]. H Let S denote the conjugate transpose of the matrix, S denote the polarization subspace of the aircraft signal, J denote the polarization subspace of the chaff signal, and E denote the polarization subspace of the chaff signal. SJ For oblique projection operators, Let I be the orthogonal projection operator of the orthogonal complement space of J, and let I be the identity matrix;

[0029] 5.3) Multiply the oblique projection operator in step 5.2) with the input signal of any polarization channel to obtain the target echo signal after suppressing chaff interference;

[0030] 6) FFT Transform

[0031] Calling the FFT IP core transforms the echo signal processed in step 4.3 or step 5 from a time-domain signal to a frequency-domain signal;

[0032] 7) Distance estimation and detonation control

[0033] The frequency domain signal obtained in step 6) is the effective target echo signal after suppressing chaff interference. For the LFMCW millimeter-wave fuze, the target distance can be calculated using the spectral line number corresponding to the spectral peak using the following formula:

[0034]

[0035] Among them, f beat_up and f beat_down These represent the difference frequency signals of the moving target's upper and lower sweep frequencies, respectively, where c is the speed of light, and T is the speed of light. M Let ΔF be the modulation period of the LFMCW signal. M The modulation bandwidth of the LFMCW signal;

[0036] When the target is within the range of the LFMCW millimeter-wave fuze detection system, an execution-level signal is output. The execution-level signal obtained after the previous steps is more reliable, reducing the probability of false detonation of the fuze.

[0037] Compared with the prior art, the advantages of this invention are:

[0038] 1. The processing of echo signals in this invention is completed in the polarization domain. Polarization domain processing, as a supplementary form of time-domain, frequency-domain, and spatial-domain signal processing, can solve problems that cannot be solved in the above three domains.

[0039] 2. This invention integrates the detection of chaff interference in the echo signal with the suppression of chaff interference, making it a relatively complete anti-interference method. The oblique projection polarization filtering method used here has the advantage of not affecting the amplitude and phase information of the target, and can be used when the polarization angles of the target and the interference differ by any one of them. Attached Figure Description

[0040] Figure 1 This is a flowchart of the method of the present invention.

[0041] Figure 2 This is a flowchart of the polarization identification method in this invention.

[0042] Figure 3 This is a flowchart of the oblique projection polarization filtering in this invention. Detailed Implementation

[0043] An FPGA-based method for resisting chaff interference in LFMCW millimeter-wave fuzes includes the following steps:

[0044] 1) AD acquisition data output

[0045] The analog-to-digital conversion is completed by sampling the difference frequency echo signals of the horizontal and vertical polarization channels using an ADC.

[0046] 2) Synchronization pulse

[0047] Synchronization control of the two acquired echo signals is achieved using synchronization pulses;

[0048] 3) FIFO buffer and FIR digital filtering

[0049] The two echo signals controlled by the synchronization pulse are buffered in a FIFO, and then the filter is designed using the FIR IP core.

[0050] 4) Polarization recognition

[0051] 4.1) Utilization To calculate the polarization ratio of the i-th echo signal in step 3), where AHH and A HV The amplitudes of the two echo signals are represented by i = 1, 2, ..., N, where N is the number of statistical echo signals.

[0052] 4.2) After calculating the polarization ratio of N echo signals, calculate their mean and determine whether the mean is greater than the discrimination threshold of the mean polarization ratio. The threshold is different for different aircraft targets. In practical applications, the mean polarization ratio of the aircraft needs to be determined in advance. The calculation method is the same as step 4.1), and this mean is used as the discrimination threshold of the mean polarization ratio.

[0053] 4.3) When the average polarization ratio of the echo signal is less than or equal to the discrimination threshold, it is determined that there is chaff interference, and it is necessary to process the chaff interference signal to suppress it, and proceed to step 5; when the average value is greater than the discrimination threshold, it is determined that there is only an aircraft target, and the target distance information can be directly analyzed and proceed to step 6.

[0054] 5) Oblique projection polarization filtering

[0055] 5.1) The echo signal that has been determined to have chaff interference through polarization identification is used as the input signal. The input signal is the echo signal of a dual-polarized fuze. First, the polarization angle γ of the echo signal is calculated using the following formula. J The difference φ between the polarization angles J Polarization parameters are estimated to determine the polarization state of the foil:

[0056]

[0057] φ J =arg[E JV (t)]-arg[E JH (t)]

[0058] Among them, E JV (t) represents the echo signal amplitude of the vertically polarized channel, E JH (t) represents the echo signal amplitude of the horizontally polarized channel, and arg[g] represents the signal phase angle.

[0059] The polarization state of the aircraft target needs to be determined in advance for practical applications. The calculation method is the same as that for calculating the polarization state of the chaff in step 5.1), and γ can also be obtained. S Aircraft polarization angle and φ S The difference in aircraft polarization angle.

[0060] 5.2) The oblique projection operator is calculated using the following formula based on the polarization parameters estimated in step 5.1):

[0061]

[0062]

[0063]

[0064] Among them, [g] T The transpose operation for a matrix is ​​represented by [g]. H Let S denote the conjugate transpose of the matrix, S denote the polarization subspace of the aircraft signal, J denote the polarization subspace of the chaff signal, and E denote the polarization subspace of the chaff signal. SJ For oblique projection operators, Let J be the orthogonal projection operator of the orthogonal complement space, and I be the identity matrix.

[0065] 5.3) Multiply the oblique projection operator in step 5.2) with the input signal of any polarization channel to obtain the target echo signal after suppressing the foil interference.

[0066] 6) FFT Transform

[0067] Calling the FFT IP core transforms the echo signal processed in step 4.3 or step 5 from a time-domain signal to a frequency-domain signal;

[0068] 7) Distance estimation and detonation control

[0069] The frequency domain signal obtained in step 6) is the effective target echo signal after suppressing chaff interference. For the LFMCW millimeter-wave fuze, the target distance can be calculated using the spectral line number corresponding to the spectral peak using the following formula:

[0070]

[0071] Among them, f beat_up and f beat_down These represent the difference frequency signals of the moving target's upper and lower sweep frequencies, respectively, where c is the speed of light, and T is the speed of light. M Let ΔF be the modulation period of the LFMCW signal. M This represents the modulation bandwidth of the LFMCW signal.

[0072] When the target is within the range of the LFMCW millimeter-wave fuze detection system, an execution-level signal is output. The execution-level signal obtained after the previous steps is more reliable, reducing the probability of false detonation of the fuze.

[0073] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for resisting chaff interference in LFMCW millimeter-wave fuzes based on FPGA, characterized in that, Includes the following steps: 1) AD acquisition data output The analog-to-digital conversion is completed by sampling the difference frequency echo signals of the horizontal and vertical polarization channels using an ADC. 2) Synchronization pulse Synchronization control is performed on the two acquired echo signals using synchronization pulses; 3) FIFO buffer and FIR digital filtering The two echo signals controlled by the synchronization pulse are buffered in a FIFO, and then the filter is designed using the FIRIP core. 4) Polarization identification, including the following steps: 4.1) Utilization To calculate the polarization ratio of the i-th echo signal in step 3), where A HH and A HV The amplitudes of the two echo signals are represented by i = 1, 2, ..., N, where N is the number of statistical echo signals. 4.2) After calculating the polarization ratio of N echo signals, calculate their mean value and determine whether the mean value is greater than the discrimination threshold value of the mean polarization ratio. The mean polarization ratio of the aircraft calculated in step 4.1) is used as the discrimination threshold value of the mean polarization ratio. 4.3) When the average polarization ratio of the echo signal is less than or equal to the discrimination threshold, it is determined that there is chaff interference. The chaff interference signal is suppressed and the process proceeds to step 5. When the average value is greater than the discrimination threshold, it is determined that there is only an aircraft target. The target distance information is obtained directly through analysis and the process proceeds to step 6. 5) Oblique projection polarization filtering, including the following steps: 5.1) The echo signal of the chaff jamming identified by the polarization recognition is taken as the input signal, and the input signal is the echo signal of the dual-polarization fuze. First, the polarization angle γ of the echo signal is determined by the following formula J and the polarization angle is different by φ J The polarization parameter estimation is carried out to determine the polarization state of the chaff. ϕ J Arg[E JV (t)]-arg[E JH (t)] Among them, E JV (t) represents the echo signal amplitude of the vertically polarized channel, E JH (t) represents the amplitude of the echo signal in the horizontally polarized channel, and arg[g] represents the phase angle of the signal. The polarization state of the aircraft target needs to be determined in advance. The calculation method is the same as in step 5.1) for calculating the polarization state of the chaff, to obtain the aircraft polarization angle γ. S and the phase difference of the aircraft polarization angle φ S ; 5.2) The oblique projection operator is calculated using the following formula based on the polarization parameters estimated in step 5.1): Among them, [g] T The transpose operation for a matrix is ​​represented by [g]. H Let S denote the conjugate transpose of the matrix, S denote the polarization subspace of the aircraft signal, J denote the polarization subspace of the chaff signal, and E denote the polarization subspace of the chaff signal. SJ For oblique projection operators, Let I be the orthogonal projection operator of the orthogonal complement space of J, and let I be the identity matrix; 5.3) Multiply the oblique projection operator in step 5.2) with the input signal of any polarization channel to obtain the target echo signal after suppressing chaff interference; 6) FFT Transform Calling the FFT IP core transforms the echo signal processed in step 4.3 or step 5 from a time-domain signal to a frequency-domain signal; 7) Distance estimation and detonation control The frequency domain signal obtained in step 6) is the effective target echo signal after suppressing chaff interference. For the LFMCW millimeter-wave fuze, the target distance is calculated using the spectral line number corresponding to the spectral peak using the following formula: Among them, f beat_up and f beat_down These represent the difference frequency signals of the moving target's upper and lower sweep frequencies, respectively, where c is the speed of light, and T is the speed of light. M Let ΔF be the modulation period of the LFMCW signal. M The modulation bandwidth of the LFMCW signal; When the target is within the range of the LFMCW millimeter-wave fuze detection system, the execution stage signal is output.

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