Passive radar secondary peak suppression method and device and electronic equipment

Abstract

The invention provides a passive radar secondary peak suppression method and device and electronic equipment, and can be applied to the technical field of passive radar signal processing. The method comprises the steps that a reference signal from an opportunity emission source and an echo signal from a detection target are acquired through a passive radar, and the echo signal is formed by reflecting a signal of the opportunity emission source by the detection target; detecting the signal format of the reference signal to obtain a signal format detection result; and performing secondary peak suppression on a coherent accumulation result of the passive radar based on the reference signal and the echo signal by using a processing strategy corresponding to the signal format detection result to obtain a target coherent accumulation result, the coherent accumulation result being determined based on the reference signal and the echo signal.

Description

Technical Field

[0001] The present disclosure relates to the technical field of passive radar signal processing, and in particular to a passive radar side peak suppression method, device and electronic equipment. Background Art

[0002] Passive radar is a radar system that detects targets by receiving existing electromagnetic wave signals (such as radio, television, and communication signals) in the environment. Its operating principle is to use the direct wave signal from an opportunistic transmitter (such as a TV station or base station) as a reference signal while simultaneously receiving the echo signal reflected from the target. By calculating the mutual ambiguity function between the two, a time delay-frequency shift plane is constructed. The energy peaks (such as the main peak) on this plane are analyzed to obtain true information about the target, thereby detecting, locating, and tracking the target.

[0003] In recent years, with the emergence and rapid development of internet satellite technology, the signals transmitted by internet satellites have provided a vast array of new electromagnetic signals for passive radars. Internet satellite systems utilize a large number of low-orbit satellites to form an internet satellite constellation. Through high-frequency electromagnetic signals and advanced communication technologies, they provide high-speed, low-latency broadband internet services to users worldwide. Compared to traditional opportunistic transmitters, the electromagnetic signals transmitted by internet satellites offer advantages such as wide coverage, high signal stability, and freedom from geographical restrictions. However, the electromagnetic signals transmitted by internet satellites are not specifically designed for radar detection applications. Therefore, when internet satellites are used as opportunistic transmitters to provide usable electromagnetic signals for passive radars to detect targets, secondary peaks may appear on the delay-frequency shift plane of the ambiguity function generated by the passive radar's calculation of the reference signal and the echo signal, due to the signal frame structure. These secondary peaks do not reflect the true information of the detected target and can interfere with the identification of the main peak that reflects the true information of the detected target, causing the passive radar to generate false alarms and failing to accurately detect, locate, and track the target. Therefore, a method is needed to suppress these secondary peaks in passive radars. Summary of the Invention

[0004] In view of this, the present disclosure provides a passive radar side peak suppression method, comprising: obtaining a reference signal from an opportunity emission source and an echo signal from a detection target through a passive radar, wherein the echo signal is formed by reflecting the reference signal from the detection target; detecting the signal format of the reference signal to obtain a signal format detection result; and utilizing a processing strategy corresponding to the signal format detection result, based on the reference signal and the echo signal, suppressing side peaks on a coherent accumulation result of the passive radar to obtain a target coherent accumulation result, wherein the coherent accumulation result is determined based on the reference signal and the echo signal.

[0005] According to an embodiment of the present disclosure, when the signal format detection result is unknown, the coherent accumulation result of the passive radar is subjected to secondary peak suppression based on the reference signal and the echo signal to obtain a target coherent accumulation result, including: performing a two-dimensional matching calculation on the reference signal and the echo signal to obtain a mutual ambiguity function between the reference signal and the echo signal; determining a function peak with a peak value greater than a first preset threshold from multiple function peaks included in the time delay-frequency shift plane of the mutual ambiguity function to obtain multiple alternative main peaks; obtaining a first coherent accumulation result based on the multiple alternative main peaks; and suppressing the secondary peak of the first coherent accumulation result based on the positional relationship between the main peak and the secondary peak of the reference signal to obtain a target coherent accumulation result.

[0006] According to an embodiment of the present disclosure, the passive radar secondary peak suppression method also includes: performing a two-dimensional matching operation on a reference signal to obtain a self-ambiguity function of the reference signal; determining a function peak whose peak value is greater than a second preset threshold from multiple function peaks included in the time delay-frequency shift plane of the self-ambiguity function to obtain multiple reference peaks; determining a first reference peak and at least one second reference peak from the multiple reference peaks, wherein the peak value of the first reference peak is greater than the peak value of each of the at least one second reference peaks; based on the difference between the position coordinates of the first reference peak and the position coordinates of each of the at least one second reference peaks, determining the positional relationship between the main peak and the secondary peak of the reference signal, wherein the position coordinates of the first reference peak include the time delay and frequency shift of the first reference peak.

[0007] According to an embodiment of the present disclosure, based on the positional relationship between the main peak and the secondary peak of the reference signal, the first coherent accumulation result is subjected to secondary peak suppression to obtain a target coherent accumulation result, including: determining the alternative main peak with the highest peak value in the first coherent accumulation result as the first target main peak; when there is at least one target secondary peak corresponding to the secondary peak position information in the first coherent accumulation result, the first target main peak is added to the main peak set, and the first target main peak and at least one target secondary peak are removed from the first coherent accumulation result to obtain an updated first coherent accumulation result, and based on the positional relationship between the main peak and the secondary peak of the reference signal, the updated first coherent accumulation result is subjected to secondary peak suppression; when there is no secondary peak corresponding to the secondary peak position information in the first coherent accumulation result, the target coherent accumulation result is obtained based on the first coherent accumulation result and the main peak set.

[0008] According to an embodiment of the present disclosure, based on the positional relationship between the main peak and the secondary peak of the reference signal, the secondary peak position information of the secondary peak corresponding to the first target main peak is determined, including: taking the position coordinates of the first target main peak as the starting point, and obtaining the alternative secondary peak position coordinates based on the positional relationship between the main peak and the secondary peak of the reference signal; taking the alternative secondary peak position coordinates as the center, and obtaining the secondary peak position information based on a preset protection interval range.

[0009] According to an embodiment of the present disclosure, when the signal format detection result is a known format, the coherent accumulation result of the passive radar is subjected to secondary peak suppression based on the reference signal and the echo signal to obtain the target coherent accumulation result, including: determining the position information of the cyclic prefix in the reference signal according to the signal format of the reference signal; removing the cyclic prefix from the reference signal based on the position information of the cyclic prefix to generate a new reference signal; and performing two-dimensional matching calculation on the new reference signal and the echo signal to obtain the target coherent accumulation result.

[0010] According to an embodiment of the present disclosure, the position information of the cyclic prefix in the reference signal is determined according to the signal format of the reference signal, including: calculating the autocorrelation function of the reference signal, and determining the effective symbol length of the reference signal based on the autocorrelation peak of the autocorrelation function; calculating the cyclic autocorrelation function of the reference signal, and determining the symbol length of the reference signal based on the cyclic autocorrelation function; determining the cyclic prefix length of the reference signal based on the effective symbol length and the symbol length; generating a synchronization sequence according to a format protocol of a known format, and correlating the synchronization sequence with the reference signal to obtain a signal frame starting position; determining the cyclic prefix starting position based on the signal frame starting position, the synchronization sequence length and the symbol length of the reference signal; determining the cyclic prefix ending position based on the cyclic prefix starting position of the symbol and the cyclic prefix length of the reference signal; and obtaining the position information of the cyclic prefix based on the cyclic prefix starting position and the cyclic prefix ending position.

[0011] According to an embodiment of the present disclosure, based on the position of the cyclic prefix, the cyclic prefix is removed from the reference signal to generate a new reference signal, including: setting the reference signal value between the starting position of the cyclic prefix and the ending position of the cyclic prefix to zero to obtain a zero signal interval of the reference signal; and adding random noise within the signal zero interval to form a new reference signal.

[0012] An embodiment of the present disclosure also provides a passive radar side peak suppression device, comprising: a signal acquisition module, for acquiring a reference signal from an opportunity emission source and an echo signal from a detection target through a passive radar, wherein the echo signal is formed by the detection target reflecting the signal of the opportunity emission source; a signal format recognition module, for detecting the signal format of the reference signal and obtaining a signal format detection result; a side peak suppression module, for utilizing a processing strategy corresponding to the signal format detection result, based on the reference signal and the echo signal, to suppress side peaks on the coherent accumulation result of the passive radar, thereby obtaining a target coherent accumulation result, wherein the coherent accumulation result is determined based on the reference signal and the echo signal.

[0013] An embodiment of the present disclosure further provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors execute the above-mentioned passive radar side peak suppression method.

[0014] According to the embodiments of the present disclosure, by first identifying and detecting the signal format of the reference signal and then selecting a targeted processing strategy to suppress the secondary peaks of the coherent accumulation results of the passive radar, the targetedness and flexibility of the secondary peak suppression of the coherent accumulation results of the passive radar are improved, so that the passive radar can select a suitable method to more accurately realize the identification and elimination of the secondary peaks in the coherent accumulation results, reduce the occurrence of missed detection, false detection, etc., and thus improve the accuracy of the passive radar in detecting the detection target. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0016] Figure 1 The flowchart of the passive radar side peak suppression method according to an embodiment of the present disclosure is schematically shown;

[0017] Figure 2 The following schematically illustrates a flow chart of a corresponding processing strategy when a signal format detection result is unknown according to an embodiment of the present disclosure;

[0018] Figure 3 The figure schematically shows a flowchart of a corresponding processing strategy when the signal format detection result is a downlink OFDM signal of a low-orbit communication constellation according to an embodiment of the present disclosure;

[0019] Figure 4 Schematic diagram showing a fuzzy function slice diagram after secondary peak suppression according to an embodiment of the present disclosure

[0020] Figure 5 The following schematically shows a flow chart of a method for determining cyclic prefix position information in a reference signal according to an embodiment of the present disclosure;

[0021] Figure 6 Schematically shows a schematic diagram of autocorrelation estimation of effective symbol length according to an embodiment of the present disclosure;

[0022] Figure 7 Schematically shows a synchronization sequence simulation diagram generated according to an embodiment of the present disclosure;

[0023] Figure 8 A block diagram of a passive radar side peak suppression device according to an embodiment of the present disclosure is schematically shown; and

[0024] Figure 9 The figure schematically shows a block diagram of an electronic device suitable for a passive radar side peak suppression method according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0026] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0027] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0028] When expressions such as “at least one of A, B, and C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art. For example, “a system having at least one of A, B, and C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc. When expressions such as “at least one of A, B, or C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art. For example, “a system having at least one of A, B, or C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.

[0029] It should also be noted that directional terms such as "upper," "lower," "front," "back," "left," and "right" mentioned in the embodiments are merely references to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, identical elements are represented by identical or similar reference numerals. Conventional structures or configurations will be omitted where they may cause confusion in understanding this disclosure.

[0030] Passive radar is a radar system that detects targets by receiving existing electromagnetic wave signals (such as radio, television, and communication signals) in the environment. Its operating principle is to use the direct wave signal from an opportunistic transmitter (such as a TV station or base station) as a reference signal while simultaneously receiving the echo signal reflected from the target. By calculating the mutual ambiguity function between the two, a time delay-frequency shift plane is constructed. The energy peaks on this plane (such as the main peak) are analyzed to obtain true information about the detected target, thereby detecting, locating, and tracking the target.

[0031] In recent years, with the emergence and rapid development of internet satellite technology, the signals transmitted by internet satellites have provided a large number of new electromagnetic wave signals for passive radar to utilize. Internet satellite systems utilize a large number of low-orbit satellites to form an internet satellite constellation. Through high-frequency electromagnetic wave signals and advanced communication technologies, they provide high-speed, low-latency broadband internet services to users around the world.

[0032] Compared with traditional opportunistic transmitters, Internet satellites have the following advantages as opportunistic transmitters: Internet satellites usually achieve continuous global coverage by establishing a satellite constellation composed of a large number of satellites. Therefore, they can ignore geographical restrictions and provide passive radars with usable electromagnetic wave signals in places where the electromagnetic signals of other opportunistic transmitters cannot reach; Internet satellite signals are relatively stable during transmission and are not easily affected by ground environmental factors; Internet satellites operate in specific frequency bands and adopt advanced communication technologies and anti-interference measures, and have strong anti-interference capabilities; the propagation path of Internet satellite signals is relatively single and is not easily affected by problems such as multipath interference; Internet satellites mostly use the high-frequency Ku / Ka band (12–40 GHz), which can provide ultra-large bandwidth. The high-frequency band and large-bandwidth opportunistic source signals can enable passive radars to obtain higher resolution.

[0033] However, internet satellite signals are not specifically designed for radar detection applications. The repetitive nature of the internal frame structure of internet satellite signals can cause passive radars to generate secondary peaks on the delay-frequency shift plane, based on the cross-ambiguity function calculated between the reference signal and the echo signal. These secondary peaks can interfere with the passive radar's ability to identify the primary peak on the delay-frequency shift plane, which represents the true target information. For example, when multiple targets are present, the peak value of the secondary peak of the echo signal of a strong target may be greater than the peak value of the primary peak of the echo signal of a weak target, resulting in missed detection of the weak target. Furthermore, if the peak value of the secondary peak is higher, the passive radar may mistakenly identify the secondary peak as the primary peak, resulting in a false alarm. Therefore, a method is needed to suppress the secondary peaks generated by the repetitive nature of the internet satellite signal frame structure.

[0034] In view of this, an embodiment of the present disclosure provides a method for suppressing secondary peaks of a passive radar, which first identifies and detects the signal format of a reference signal, and then selects a targeted processing strategy to suppress secondary peaks of the coherent accumulation results of the passive radar. This improves the targetedness of the secondary peak suppression of the coherent accumulation results of the passive radar, and enables the passive radar to more flexibly select a suitable method to suppress secondary peaks.

[0035] Specifically, an embodiment of the present disclosure provides a passive radar side peak suppression method, comprising: obtaining a reference signal from an opportunity emission source and an echo signal from a detection target through a passive radar, wherein the echo signal is formed by the detection target reflecting the signal of the opportunity emission source; detecting the signal format of the reference signal to obtain a signal format detection result; and utilizing a processing strategy corresponding to the signal format detection result, based on the reference signal and the echo signal, performing side peak suppression on a coherent accumulation result of the passive radar to obtain a target coherent accumulation result, wherein the coherent accumulation result is determined based on the reference signal and the echo signal.

[0036] Figure 1 The flowchart of the passive radar side peak suppression method according to an embodiment of the present disclosure is schematically shown.

[0037] like Figure 1 As shown, the method includes operations S101 to S103.

[0038] In operation S101 , a reference signal from an opportunity transmission source and an echo signal from a detection target are acquired by a passive radar.

[0039] According to embodiments of the present disclosure, an echo signal can be generated by a target reflecting an electromagnetic wave signal emitted by an opportunistic emitter that impinges on its surface. By analyzing the received echo signal, a passive radar can obtain information about the target. For example, by analyzing the time delay and Doppler shift of the echo signal relative to a reference signal, information such as the target's position and velocity can be calculated.

[0040] According to an embodiment of the present disclosure, the echo signal received by the passive radar may include the echo signal of a single detection target, or may include the echo signals of multiple detection targets.

[0041] According to an embodiment of the present disclosure, the opportunistic emission source may be a third-party radio signal source, whose electromagnetic wave signal is not specifically designed for radar detection but can be borrowed by a passive radar for target detection.

[0042] According to an embodiment of the present disclosure, the reference signal can be a direct signal emitted by an opportunistic transmitter received by a passive radar, or it can be a signal reconstructed based on prior knowledge such as a known communication protocol of the opportunistic transmitter; the reference signal has a strong waveform correlation with the echo signal. In some embodiments, the echo signal can be similar to a signal obtained by adding a time delay and / or Doppler frequency shift to the reference signal.

[0043] According to an embodiment of the present disclosure, a passive radar may adopt a dual-antenna configuration when detecting a target, wherein the echo receiving antenna points to the target airspace to receive the echo signal; and the reference antenna points to the opportunity transmitting source to obtain the direct signal.

[0044] According to an embodiment of the present disclosure, a reference signal can be used as a reference signal for signal processing of an echo signal. During the signal processing process, the reference signal can be subjected to a two-dimensional matching calculation with the echo signal to obtain a mutual ambiguity function of the echo signal and the reference signal. Based on the time delay-frequency shift plane of the mutual ambiguity function, a main peak reflecting the true information of the detection target on the plane can be obtained by screening, wherein the position coordinates of the main peak are composed of the time delay and frequency shift of the echo signal of any detection target relative to the reference signal. For example, there is a main peak on the time delay-frequency shift plane of a mutual ambiguity function, and its position coordinates can be ( , 11kHz), the position coordinates can represent the time delay of the echo signal of a detection target relative to the reference signal as , the frequency shift is 11kHz.

[0045] According to embodiments of the present disclosure, the propagation time difference between the echo signal of any detection target and a reference signal can be obtained based on the time delay, and the propagation distance difference between the echo signal of any detection target and the reference signal can be calculated based on the propagation time difference. In the case of multi-station collaboration and / or multi-parameter combination, the radial distance between the detection target and the passive radar can be calculated by combining the propagation distance difference and the geometric relationship between the opportunity transmission source, the detection target, and the passive radar. The propagation distance of the echo signal of any detection target can be the sum of the distance from the opportunity transmission source to the detection target and the distance from the detection target to the passive radar; the propagation distance of the reference signal can be the distance from the opportunity transmission source to the passive radar. In addition, the speed of the detection target can be calculated based on the frequency offset and the geometric relationship between the opportunity transmission source, the detection target, and the passive radar.

[0046] In operation S102 , a signal format of a reference signal is detected to obtain a signal format detection result.

[0047] For example, the reference signal may be a downlink signal of an Internet satellite, and the method for detecting the signal format of the reference signal may be to compare the reference signal to be detected and identified with a sample of a known signal format.

[0048] According to an embodiment of the present disclosure, when the format of the reference signal is detected, the signal format detection result may be the name of a signal in a known format. For example, the signal format detection result may be: the downlink OFDM signal of Internet satellite system A, wherein the specific format of the downlink OFDM signal is known. When the signal format of the reference signal is not detected, the signal format detection result may be: the signal format is unknown.

[0049] In operation S103 , a processing strategy corresponding to the signal format detection result is used to suppress secondary peaks on the coherent integration result of the passive radar based on the reference signal and the echo signal to obtain a target coherent integration result.

[0050] According to embodiments of the present disclosure, the target coherent accumulation result can be composed of a main peak reflecting the true information of the detected target on the time delay-frequency shift plane of the mutual ambiguity function. The mutual ambiguity function can be obtained by performing a two-dimensional matching calculation based on the reference signal and the echo signal. The target coherent accumulation result can include one or more main peaks, and the corresponding detected targets can also be one or more.

[0051] According to embodiments of the present disclosure, utilizing a processing strategy corresponding to the signal format detection result can be understood as selecting a more appropriate method, such as a more accurate and faster method, for secondary peak suppression based on the signal format detection result. For example, in one embodiment of the present disclosure, internet satellite downlink signals are used for target detection. However, downlink signals from internet satellite systems do not have a unified format. While the signal formats of some downlink signals have been publicly disclosed, the signal formats of others have not.

[0052] When signal format detection is performed on an Internet satellite signal serving as a reference signal and the signal format detection result is an unknown format, the present disclosure adopts a secondary peak suppression method for the unknown reference signal format to suppress secondary peaks; when the signal format detection result is a known specific format protocol, the present disclosure adopts a method that matches the structural characteristics of the signal format to achieve secondary peak suppression.

[0053] According to the embodiments of the present disclosure, by first identifying and detecting the signal format of the reference signal and then selecting a targeted processing strategy to suppress the secondary peaks of the coherent accumulation results of the passive radar, the targetedness and flexibility of the secondary peak suppression of the coherent accumulation results of the passive radar are improved, so that the passive radar can select a suitable method to more accurately realize the identification and elimination of the secondary peaks in the coherent accumulation results, reduce the occurrence of missed detection, false detection, etc., and thus improve the accuracy of the passive radar in detecting the detection target.

[0054] According to the embodiments of the present disclosure, in the actual application of passive radar, the signal structure of the signals emitted by some opportunistic emission sources is not disclosed to the public. For example, the specific signal format of the downlink signals of some Internet satellites is not disclosed to the public. Therefore, when using the electromagnetic wave signals emitted by the above-mentioned opportunistic emission sources for passive radar detection, it is necessary to suppress the secondary peaks in the case of an unknown signal format.

[0055] According to an embodiment of the present disclosure, when the signal format detection result is unknown, the coherent accumulation result of the passive radar is subjected to secondary peak suppression based on the reference signal and the echo signal to obtain a target coherent accumulation result, including: performing a two-dimensional matching calculation on the reference signal and the echo signal to obtain a mutual ambiguity function between the reference signal and the echo signal; determining a function peak with a peak value greater than a first preset threshold from multiple function peaks included in the time delay-frequency shift plane of the mutual ambiguity function to obtain multiple alternative main peaks; obtaining a first coherent accumulation result based on the multiple alternative main peaks; and suppressing the secondary peak of the first coherent accumulation result based on the positional relationship between the main peak and the secondary peak of the reference signal to obtain a target coherent accumulation result.

[0056] Figure 2 The flowchart schematically shows a corresponding processing strategy when the signal format detection result is unknown according to an embodiment of the present disclosure.

[0057] like Figure 2 As shown, the method includes operations S201 to S204.

[0058] In operation S201 , a two-dimensional matching calculation is performed on a reference signal and an echo signal to obtain a mutual ambiguity function between the reference signal and the echo signal.

[0059] According to an embodiment of the present disclosure, a two-dimensional matching calculation is performed on the reference signal and the echo signal to obtain the mutual ambiguity function of the reference signal and the echo signal, which can be shown as formula (1):

[0060] (1);

[0061] in, represents the reference signal, Indicates the echo signal Adding a time offset and take the conjugate obtained signal, represents the mutual fuzzy function value, Indicates delay, represents the frequency shift, and N represents the number of sampling points.

[0062] In operation S202, a function peak having a peak value greater than a first preset threshold is determined from a plurality of function peaks included in a time delay-frequency shift plane of the mutual ambiguity function to obtain a plurality of candidate main peaks.

[0063] According to an embodiment of the present disclosure, a function peak on the delay-frequency shift plane can be determined based on the distribution of the function value of the mutual ambiguity function on the two-dimensional plane. Specifically, a point on the delay-frequency shift plane where the function value of the mutual ambiguity function is significantly higher than that of the surrounding area can be determined as a function peak.

[0064] According to an embodiment of the present disclosure, the first preset threshold can be used as a noise floor decision threshold to extract all function peaks with peak values higher than the noise floor as candidate main peaks. The candidate main peaks include the main peak and / or secondary peaks obtained by calculating the mutual ambiguity function between the reference signal and the echo signal.

[0065] According to the embodiment of the present disclosure, the main peak reflects the real information of the detection target, and the distance, speed, position and other information of the detection target can be obtained by analyzing the main peak.

[0066] The false target information generated in the calculation of the mutual ambiguity function due to the repetitiveness of the reference signal within the signal frame is eliminated.

[0067] According to the embodiments of the present disclosure, the influence of background noise on secondary peak identification is eliminated by presetting a first preset threshold, which can reduce the amount of calculation for subsequent secondary peak identification, speed up the identification, and reduce system resource overhead.

[0068] In operation S203 , a first coherent accumulation result is obtained based on the multiple candidate main peaks.

[0069] According to an embodiment of the present disclosure, a set of candidate main peaks constitutes a first coherent accumulation result. The candidate main peaks can be main peaks or secondary peaks. Therefore, the first coherent accumulation result includes main peaks and secondary peaks generated based on the echo signal of the detection target.

[0070] The main peak and the secondary peak can be distinguished by selecting the secondary peak and / or the main peak in the first coherent accumulation result. Furthermore, only the main peak is retained for calculating the real information of the detected target, thereby achieving secondary peak suppression for the passive radar.

[0071] In operation S204 , based on the positional relationship between the main peak and the secondary peak of the reference signal, secondary peak suppression is performed on the first coherent integration result to obtain a target coherent integration result.

[0072] According to an embodiment of the present disclosure, the echo signal received by the passive radar may include echo signals of multiple detection targets. The reference signal may be correlated with the echo signal of any detection target. Therefore, the positional relationship between the main peak and the secondary peak of the reference signal obtained by performing a self-ambiguity function calculation on the reference signal can match the positional relationship between the main peak and the secondary peak of the echo signal obtained by performing a mutual ambiguity function calculation on the echo signal of any detection target and the reference signal. Therefore, the positional relationship between the main peak and the secondary peak of the echo signal of any detection target can be determined based on the positional relationship between the main peak and the secondary peak of the reference signal, and then the secondary peak corresponding to the echo signal of any detection target can be screened out and suppressed based on the positional relationship between the main peak and the secondary peak of the echo signal of any detection target.

[0073] According to an embodiment of the present disclosure, the positional relationship between the main peak and the secondary peak of the reference signal may be the relative distance between the coordinates of the main peak and the secondary peak on the time delay-frequency shift plane.

[0074] According to the embodiments of the present disclosure, based on the characteristic of strong correlation between the waveforms of the reference signal and the echo signal of any detection target, the positional relationship between the main peak and the secondary peak of the echo signal of any detection target can be determined according to the positional relationship between the main peak and the secondary peak of the reference signal, thereby realizing the identification and elimination of the secondary peak, solving the technical problem of identifying and suppressing the secondary peak of the echo signal in the case of an unknown signal structure.

[0075] According to an embodiment of the present disclosure, the passive radar secondary peak suppression method also includes: performing a two-dimensional matching operation on a reference signal to obtain a self-ambiguity function of the reference signal; determining a function peak whose peak value is greater than a second preset threshold from multiple function peaks included in the time delay-frequency shift plane of the self-ambiguity function to obtain multiple reference peaks; determining a first reference peak and at least one second reference peak from the multiple reference peaks, wherein the peak value of the first reference peak is greater than the peak value of each of the at least one second reference peaks; based on the difference between the position coordinates of the first reference peak and the position coordinates of each of the at least one second reference peaks, determining the positional relationship between the main peak and the secondary peak of the reference signal, wherein the position coordinates of the first reference peak include the time delay and frequency shift of the first reference peak.

[0076] According to an embodiment of the present disclosure, a two-dimensional matching operation is performed on the reference signal, and the self-ambiguity function of the obtained reference signal can be shown as formula (2):

[0077] (2);

[0078] in, represents the reference signal, Indicates the reference signal Add delay and take the conjugate obtained signal, represents the fuzzy function value, Indicates delay, represents the frequency shift, and N represents the number of sampling points.

[0079] According to an embodiment of the present disclosure, the function peak of the self-ambiguity function of the reference signal on the delay-frequency shift plane can be determined based on the distribution of the function values of the self-ambiguity function of the reference signal on the delay-frequency shift plane. Specifically, the function peak can be determined as a point on the delay-frequency shift plane where the function value of the self-ambiguity function is significantly higher than that of the surrounding area.

[0080] According to an embodiment of the present disclosure, the second preset threshold can be used as a noise floor decision threshold to extract all reference peaks whose peak values are higher than the noise floor, wherein the reference peaks include the main peak and secondary peaks of the reference signal obtained by performing self-fuzzy function calculation on the reference signal.

[0081] According to embodiments of the present disclosure, the second preset threshold can be set based on one or more influencing factors. These factors may include noise conditions, system sensitivity requirements, and long-term experience. The second preset value can be a fixed value or a dynamically adjustable value. For example, in one embodiment, the second preset threshold is set to 13dB based on long-term experience. In another embodiment, the second preset threshold is temporarily set to 13dB based on noise conditions. If the noise conditions change, the second preset threshold will also be adjusted accordingly.

[0082] According to an embodiment of the present disclosure, the multiple reference peaks screened by the second preset threshold can be used to calculate the positional relationship between the main peak and the secondary peaks of the reference signal.

[0083] According to an embodiment of the present disclosure, the reference peak with the largest peak value can be determined as the main peak of the reference signal, that is, the first reference peak; the remaining reference peaks can be determined as secondary peaks of the reference signal, that is, at least one second reference peak. The positional relationship between the secondary peak of any reference signal and the main peak of the reference signal can be expressed as the difference between the coordinates of the secondary peak of any reference signal on the time delay-frequency shift plane and the coordinates of the main peak of the reference signal on the time delay-frequency shift plane, where the difference in coordinates can be represented by a difference array; the positional relationship difference array between the secondary peaks and the main peak of multiple reference signals constitutes the positional relationship between the main peak and the secondary peaks of the reference signal.

[0084] For example, in one embodiment, the reference peak obtained by calculation includes: 、 、…、 ; Among them, the reference peak The peak value of is determined as the main peak of the reference signal, and other reference peaks are determined as secondary peaks of the reference signal. With the main peak The positional relationship can be expressed as a difference array ,in, and The value of can be calculated by the following formula (3) and formula (4) respectively.

[0085] (3);

[0086] (4);

[0087] in, It represents the difference between the rth secondary peak and the main peak of the reference signal on the delay axis of the delay-frequency shift plane. represents the difference between the rth secondary peak and the main peak of the reference signal on the frequency shift axis of the time delay-frequency shift plane. Therefore, the positional relationship between the main peak and the secondary peak of the reference signal can be expressed as , where R is the number of secondary peaks of the reference signal.

[0088] According to an embodiment of the present disclosure, by setting a second preset threshold, the reference peak including the main peak and secondary peak of the reference signal is extracted from the background noise, so as to eliminate the interference of the background noise and eliminate the possible false secondary peaks in order to calculate the positional relationship between the main peak and the secondary peak of the reference signal, thereby improving the accuracy of the positional relationship calculation; by determining the positional relationship between the secondary peak and the main peak of the reference signal as the difference between the position coordinates of the secondary peak and the main peak of the reference signal, a clear reference basis is provided for suppressing the secondary peak of the first coherent accumulation result.

[0089] According to an embodiment of the present disclosure, based on the positional relationship between the main peak and the secondary peak of the reference signal, the first coherent accumulation result is subjected to secondary peak suppression to obtain a target coherent accumulation result, including: determining the alternative main peak with the highest peak value in the first coherent accumulation result as the first target main peak; when there is at least one target secondary peak corresponding to the secondary peak position information in the first coherent accumulation result, the first target main peak is added to the main peak set, and the first target main peak and at least one secondary peak are removed from the first coherent accumulation result to obtain an updated first coherent accumulation result, and based on the positional relationship between the main peak and the secondary peak of the reference signal, the updated first coherent accumulation result is subjected to secondary peak suppression; when there is no secondary peak corresponding to the secondary peak position information in the first coherent accumulation result, the target coherent accumulation result is obtained based on the first coherent accumulation result and the main peak set.

[0090] According to an embodiment of the present disclosure, the echo signal received by the passive radar may include echo signals of multiple detection targets. Therefore, the first coherent integration result obtained by calculating the reference signal and the echo signal may include multiple main peaks and multiple secondary peaks generated based on the echo signals of the multiple detection targets; the signal strengths of the echo signals of the multiple detection targets may be different. Therefore, the peak value of the main peak of one echo signal may be smaller than the peak value of the secondary peak of another echo signal, which may cause the main peaks and secondary peaks of the multiple detection targets to be unable to be accurately distinguished. However, the peak value of the main peak corresponding to the echo signal of any detection target may be greater than the peak values of all its corresponding secondary peaks. Therefore, among the multiple candidate main peaks of the first coherent integration result, the candidate main peak with the largest peak value may be the main peak corresponding to the echo signal of a detection target, that is, the first target main peak, where the echo signal intensity of the detection target is the largest.

[0091] According to an embodiment of the present disclosure, the alternative main peaks in the first coherent accumulation result can also be arranged in descending order according to the peak size to obtain the alternative main peak arrangement, and the alternative main peak ranked first is determined as the first target main peak and added to the main peak set, wherein the main peak set can include multiple main peaks reflecting the real information of multiple detection targets.

[0092] According to an embodiment of the present disclosure, after determining that the alternative main peak with the largest peak value in the first coherent accumulation result is the first target main peak, a round of secondary peak identification can be performed on the first reference signal; wherein, one round of secondary peak identification may include: determining the secondary peak position information of the secondary peak corresponding to the first target main peak on the time delay-frequency shift plane based on the positional relationship between the main peak and the secondary peak of the reference signal, wherein there may be one or more secondary peaks; based on the above-mentioned secondary peak position information, comparing with the alternative main peak in the first coherent accumulation result, when the position coordinates of the alternative main peak match the above-mentioned secondary peak position information, determining the alternative main peak as a secondary peak, wherein the first target main peak and the corresponding secondary peak may be alternative main peaks generated based on the echo signal of the same detection target.

[0093] According to an embodiment of the present disclosure, after completing a round of secondary peak identification, the first target main peak and the corresponding secondary peaks may be removed from the first coherent accumulation result, and the first coherent accumulation result may be updated.

[0094] According to an embodiment of the present disclosure, another alternative main peak with the highest peak value can be selected from the alternative main peaks of the updated first coherent accumulation result as the first target main peak, and added to the main peak set, wherein the first target main peak can be a main peak generated based on the echo signal of another detection target, and the next round of secondary peak identification can be performed based on the first target main peak.

[0095] According to an embodiment of the present disclosure, when the number of secondary peaks obtained in a round of secondary peak identification is zero, it can be considered that in the first coherent accumulation result of this round, the peak value of the secondary peak generated based on the echo signal with the highest signal strength is less than the second preset threshold, that is, the secondary peak has been submerged by the background noise and is filtered out together with the background noise. In this case, it can be considered that the secondary peaks corresponding to other possible main peaks in the first coherent accumulation result have also been filtered out together with the background noise. Therefore, the first target main peak of this round and other candidate main peaks in the first coherent accumulation result can be determined as main peaks and added to the main peak set, ending the identification of secondary peaks in the first coherent accumulation result, completing the secondary peak suppression of the first coherent accumulation result, and obtaining the main peak set after the secondary peaks are suppressed.

[0096] According to an embodiment of the present disclosure, the alternative main peak with the largest peak value in the first coherent accumulation result is determined as the first target main peak, and based on the relationship between the main peak and the secondary peak of the reference signal, the secondary peak generated by the echo signal based on the same detection target is identified, thereby improving the accuracy of identifying the secondary peaks in the first coherent accumulation result; through an iterative approach, all the main peaks and secondary peaks in the first coherent accumulation result are identified, effectively avoiding missed detection and false detection of secondary peaks existing in the first coherent accumulation result.

[0097] According to the embodiments of the present disclosure, the positional relationship between the main peak and the secondary peak of the reference signal obtained based on the self-ambiguity function of the reference signal may have errors due to factors such as calculation accuracy and signal interference; the self-ambiguity function obtained based on the echo signal and the reference signal may also cause the calculated positions of the main peak and / or secondary peak to shift due to signal interference, calculation accuracy and other reasons. Therefore, it is necessary to adopt appropriate methods to reduce the impact of the above-mentioned errors and / or shifts on the identification of secondary peaks.

[0098] According to an embodiment of the present disclosure, based on the positional relationship between the main peak and the secondary peak of the reference signal, the secondary peak position information of the secondary peak corresponding to the first target main peak is determined, including: taking the position coordinates of the first target main peak as the starting point, and obtaining the alternative secondary peak position coordinates based on the positional relationship between the main peak and the secondary peak of the reference signal; taking the alternative secondary peak position coordinates as the center, and obtaining the secondary peak position information based on a preset protection interval range.

[0099] According to an embodiment of the present disclosure, the positional relationship between the main peak and the secondary peak of the reference signal can be expressed as , where R is the number of secondary peaks of the reference signal, It can represent the coordinate difference between the rth secondary peak and the main peak of the reference signal on the delay axis. It can represent the coordinate difference between the rth secondary peak of the reference signal and the main peak of the reference signal on the frequency shift axis.

[0100] According to an embodiment of the present disclosure, the secondary peak position information can be one or more protection areas on the time delay-frequency shift plane of the mutual ambiguity function of the reference signal and the echo signal. When the position coordinates of the alternative main peak in the first coherent accumulation result are in the one or more protection areas, the alternative main peak can be determined to be the secondary peak corresponding to the first target main peak.

[0101] According to an embodiment of the present disclosure, the coordinates of the candidate secondary peak position can be used to determine the center position of the protection area. The coordinates of the candidate secondary peak position are obtained by adding them to the coordinates of the first target main peak.

[0102] For example, when the first target peak The coordinates are , corresponds to the first target main peak The rth candidate secondary peak position coordinates can be .

[0103] According to an embodiment of the present disclosure, the protection area corresponding to the rth secondary peak can be expressed as ,in and They are the guard intervals in the delay direction and frequency shift direction on the delay-frequency shift plane respectively.

[0104] According to the embodiments of the present disclosure, a protection area is set with the position coordinates of the alternative secondary peak as the center, and the alternative main peak falling within the protection area is determined to be a secondary peak. This method effectively avoids the technical problem of inaccurate identification of secondary peaks due to noise interference or calculation errors, and reduces the probability of misidentification or missed identification of secondary peaks.

[0105] According to an embodiment of the present disclosure, when the signal format detection result is a known format, the coherent accumulation result of the passive radar is subjected to secondary peak suppression based on the reference signal and the echo signal to obtain the target coherent accumulation result, including: determining the position information of the cyclic prefix in the reference signal according to the signal format of the reference signal; removing the cyclic prefix from the reference signal based on the position information of the cyclic prefix to generate a new reference signal; and performing two-dimensional matching calculation on the new reference signal and the echo signal to obtain the target coherent accumulation result.

[0106] Figure 3 The figure schematically shows a flowchart of a corresponding processing strategy when the signal format detection result is a downlink OFDM signal of a low-orbit communication constellation according to an embodiment of the present disclosure;

[0107] like Figure 3 As shown, the method includes operations S301 to S303.

[0108] In operation S301 , position information of a cyclic prefix in a reference signal is determined according to a signal format of the reference signal.

[0109] According to embodiments of the present disclosure, a cyclic prefix is a segment of tail data of a valid symbol added before the symbol in the OFDM signal frame structure. It is used to eliminate multipath interference (ISI), simplify equalization at the receiving end, and assist in symbol synchronization. The valid symbol is the data transmitted by the communication signal.

[0110] According to an embodiment of the present disclosure, when the signal format of a reference signal is known, the position information of the cyclic prefix in the signal structure within the frame structure of the reference signal can be found based on the specific structure of the reference signal. The position information of the cyclic prefix can be determined by the starting position and the ending position of the cyclic prefix in the signal frame.

[0111] According to an embodiment of the present disclosure, based on the specific frame structure of the reference signal, the distance of the starting position of the cyclic prefix relative to the frame header and the distance of the ending position relative to the frame header can be obtained; based on the above distances, the specific position information of the cyclic prefix in the frame structure can be determined.

[0112] In operation S302 , based on the position information of the cyclic prefix, the cyclic prefix is removed from the reference signal to generate a new reference signal.

[0113] According to an embodiment of the present disclosure, removing the cyclic prefix can be understood as removing the cyclic prefix from the reference signal. For example, if the reference signal is an OFDM signal, removing the cyclic prefix can be understood as removing the cyclic prefix from each symbol header within the signal frame structure.

[0114] According to an embodiment of the present disclosure, the new reference signal may be used to perform mutual ambiguity function calculation with the echo signal to obtain a main peak corresponding to the detection target.

[0115] According to an embodiment of the present disclosure, a reference signal can be used to perform a two-dimensional matching calculation with the echo signal to obtain a mutual ambiguity function between the reference signal and the echo signal. The distribution of the function values of the mutual ambiguity function on the time delay-frequency shift plane can be obtained by sliding the mutual ambiguity function on the time delay-frequency shift plane. When the reference signal coincides with the echo signal of any detected target, a primary peak is generated; when only the reference signal coincides with the same cyclic prefix in the echo signal, a secondary peak is generated. Therefore, by removing the cyclic prefix from the reference signal, the cyclic prefix in the reference signal can be prevented from coinciding with the same cyclic prefix in the echo signal to generate a secondary peak.

[0116] In operation S303 , a two-dimensional matching calculation is performed on the new reference signal and the echo signal to obtain a target coherent accumulation result.

[0117] According to an embodiment of the present disclosure, the two-dimensional matching calculation may be to calculate a mutual ambiguity function between the new reference signal and the echo signal.

[0118] According to an embodiment of the present disclosure, the target coherent accumulation result may include a main peak corresponding to one detection target or may include multiple main peaks corresponding to multiple detection targets.

[0119] Figure 4 The figure schematically shows a slicing diagram of a fuzzy function after secondary peak suppression according to an embodiment of the present disclosure.

[0120] like Figure 4 As shown, Figure 4 This is a slice of the ambiguity function at zero frequency shift. There is a main peak at zero time delay, and no secondary peaks clearly distinguishable from the noise floor at other locations. This shows that the secondary peaks are effectively suppressed in the calculation of the mutual ambiguity function for the new reference signal and the echo signal.

[0121] According to the embodiments of the present disclosure, by removing the cyclic prefix from the reference signal frame structure based on the reference signal's signal format, a new reference signal is generated. This new reference signal is then used to calculate the mutual ambiguity function with the echo signal to obtain the main peak corresponding to the target being detected. This effectively addresses the technical issue of passive radars being unable to accurately detect, identify, and track targets due to the repetitive nature of the electromagnetic wave signal frame structure emitted by opportunistic transmitters. By rationally modifying the reference signal, the subsequent calculation required to identify the main peak is avoided, reducing the system's computational workload.

[0122] According to an embodiment of the present disclosure, the position information of the cyclic prefix in the reference signal is determined according to the signal format of the reference signal, including: calculating the autocorrelation function of the reference signal, and determining the effective symbol length of the reference signal based on the autocorrelation peak of the autocorrelation function; calculating the cyclic autocorrelation function of the reference signal, and determining the symbol length of the reference signal based on the cyclic autocorrelation function; determining the cyclic prefix length of the reference signal based on the effective symbol length and the symbol length; generating a synchronization sequence according to a format protocol of a known format, and correlating the synchronization sequence with the reference signal to obtain a signal frame starting position; determining the cyclic prefix starting position based on the signal frame starting position, the synchronization sequence length and the symbol length of the reference signal; determining the cyclic prefix ending position based on the cyclic prefix starting position of the symbol and the cyclic prefix length of the reference signal; and obtaining the position information of the cyclic prefix based on the cyclic prefix starting position and the cyclic prefix ending position.

[0123] According to an embodiment of the present disclosure, the signal format of the reference signal may be: pilot+symbol 1+symbol 2+symbol 3..., wherein the pilot may include a synchronization sequence, and the symbol composition may be: cyclic prefix+valid symbol.

[0124] Figure 5 The flowchart of the method for determining cyclic prefix position information in a reference signal according to an embodiment of the present disclosure is schematically shown.

[0125] like Figure 5 As shown, the method includes operations S501 to S507.

[0126] In operation S501 , an autocorrelation function of a reference signal is calculated, and an effective symbol length of the reference signal is determined based on an autocorrelation peak of the autocorrelation function.

[0127] According to an embodiment of the present disclosure, the reference signal obtained by the passive radar can be Perform windowing processing to obtain the reference signal segment , , where N represents the reference signal segment The sequence length is N, and N is greater than the estimated effective symbol length.

[0128] According to an embodiment of the present disclosure, the autocorrelation function of the reference signal can be expressed as the following formula (5):

[0129] (5);

[0130] in, Indicates the reference signal The reference signal segment obtained by windowing, N represents the reference signal segment The sequence length, represents conjugation, Indicates two reference signal segments The autocorrelation function value when the sliding distance is k.

[0131] According to an embodiment of the present disclosure, the symbol of the reference signal consists of a cyclic prefix and a valid symbol, wherein the cyclic prefix is a segment of tail copy data of a valid symbol added before the valid symbol. Referring to formula (5), it can be seen that when k=0, the two reference signal segments coincide, the autocorrelation function obtains the maximum peak, and when When the cyclic prefix coincides with the copied segment at the end of the valid symbol, the autocorrelation function obtains the second peak ; Detect the second peak , and extract the peak value corresponding to the sampling point position , then , further effective symbol length It can be expressed as formula (6).

[0132] (6);

[0133] in, is the effective symbol length in time units, is the sampling rate, is the number of sampling points that constitute a valid symbol.

[0134] In operation S502 , a cyclic autocorrelation function of a reference signal is calculated, and a symbol length of the reference signal is determined based on the cyclic autocorrelation function.

[0135] According to an embodiment of the present disclosure, the reference signal may be a cyclostationary signal. For the cyclostationary signal, the symbol length in the frame structure may be obtained by using a cyclic autocorrelation function and its extended calculation.

[0136] For example, the reference signal can be an OFDM signal for downlinking an Internet satellite. In the frame structure of an OFDM signal, a symbol can be composed of a valid symbol and a cyclic prefix. The cyclic prefix is located in front of the valid symbol and is connected to the valid symbol to form a symbol. Symbol length in time units It can be expressed as the following formula (7):

[0137] (7);

[0138] in, is the effective symbol length, is the cyclic prefix length.

[0139] According to an embodiment of the present disclosure, determining the symbol length of the reference signal based on the cyclic autocorrelation function may include:

[0140] Perform windowing on the reference signal to obtain the reference signal segment , where the reference signal segment The sequence length It needs to be greater than the symbol length. Since the symbol length has not yet been calculated, it can be determined based on experience. The cyclic autocorrelation function of the reference signal is calculated as shown in the following formula (8):

[0141] (8);

[0142] in, is the reference signal segment, represents conjugation, is the cycle frequency, reflecting the signal periodicity (i.e., OFDM symbol rate), For delay, The reference signal segment The sequence length, For a and is a two-dimensional matrix of horizontal and vertical coordinates.

[0143] exist and On the two-dimensional matrix with horizontal and vertical coordinates, search for the peak value corresponding to the symbol length. Since when the reference signal is an OFDM signal, only when the cyclic frequency value meets the OFDM symbol rate There is a peak. In a two-dimensional matrix, we can take the cyclic frequency where the peak exists Corresponding , detect the second peak on it , where the first peak is the cycle frequency , delay The peak value obtained when the cyclic autocorrelation function of the reference signal is calculated is the cyclic autocorrelation function value obtained when the two reference signal segments completely overlap; the second peak value is is the peak value that is adjacent to the first peak value on the two-dimensional matrix. The position of the second peak value in the two-dimensional matrix can be expressed as: , based on delay and sampling frequency The symbol length in time units is calculated using the following formula (9).

[0144] (9);

[0145] in, is the sampling rate, is the time delay, expressed in the number of sampling points.

[0146] In operation S503 , a cyclic prefix length of a reference signal is determined based on the effective symbol length and the symbol length.

[0147] According to an embodiment of the present disclosure, the length of the cyclic prefix It can be expressed as the following formula (10):

[0148] (10);

[0149] in, is the symbol length, is the effective symbol length.

[0150] In operation S404, a synchronization sequence is generated according to a format protocol of a known format, and a correlation calculation is performed between the synchronization sequence and a reference signal to obtain a signal frame start position.

[0151] According to an embodiment of the present disclosure, the frame start position can be obtained by detecting a correlation peak of a synchronization sequence, wherein the frame start position indicates the first sampling point position of a frame header.

[0152] According to embodiments of the present disclosure, a synchronization sequence can be used to achieve frame timing synchronization and determine the starting position in the frame structure. Common synchronization sequence formats used in reference signals may include: ZC sequence (Zadoff-Chu), pseudo-random noise sequence (such as m sequence, Gold sequence), etc.

[0153] In one embodiment of the present disclosure, the opportunistic transmitter is a constellation of low-orbit communications satellites. Its downlink signal format is a known OFDM signal. A passive radar receives the direct signal from this downlink signal as a reference signal. Based on the signal format, it generates a synchronization sequence consisting of a Primary Synchronization Signal (PSS) and a Secondary Synchronization Signal (SSS).

[0154] According to an embodiment of the present disclosure, the process of determining the starting position of the signal frame may be: generating a PSS, performing sliding correlation calculation on the generated PSS and a reference signal, searching for a generated correlation peak, and determining the starting position of the signal frame based on the correlation peak.

[0155] In operation S505 , a cyclic prefix starting position is determined based on a signal frame starting position, a synchronization sequence length, and a symbol length of a reference signal.

[0156] According to an embodiment of the present disclosure, the reference signal may include multiple or one signal frames, and the signal frame may be composed of a synchronization sequence and a symbol. The starting position of the cyclic prefix may be obtained by taking the starting position of the signal frame as the starting point, referring to the synchronization sequence length and the symbol length of the reference signal.

[0157] For example, in one embodiment of the present disclosure, the frame start position is point A, the synchronization sequence length is B, there are three symbols in the frame structure, and the symbol length of the reference signal is , then the starting position of the cyclic prefix of the first symbol is , the starting position of the cyclic prefix of the second symbol is , the starting position of the cyclic prefix of the third symbol is .

[0158] According to an embodiment of the present disclosure, other structures may also exist in the signal frame structure, and the components in the signal frame structure may also be arranged in other arrangements. For example, the signal frame structure may also include other signal structures such as pilots and intervals, and the synchronization sequence may also be inserted between symbols, etc. However, all of these may be based on a method similar to the above method, and the starting position of the cyclic prefix may be determined according to the length and positional relationship of the components in the signal frame structure.

[0159] In operation S506 , a cyclic prefix end position is determined based on the cyclic prefix start position of the symbol and the cyclic prefix length of the reference signal.

[0160] According to an embodiment of the present disclosure, the cyclic prefix end position of each symbol can be obtained by adding the corresponding cyclic prefix start position to the cyclic prefix length.

[0161] In operation S507 , position information of the cyclic prefix is obtained based on the cyclic prefix start position and the cyclic prefix end position.

[0162] According to an embodiment of the present disclosure, the position information of the cyclic prefix may be an interval defined by a cyclic prefix start position and a cyclic prefix end position in a frame structure.

[0163] Figure 6 The figure schematically shows a schematic diagram of estimating the effective symbol length by autocorrelation according to an embodiment of the present disclosure.

[0164] like Figure 6 As shown, two reference signals are correlated by sliding. When the sliding distance is the same as the effective symbol length, the cyclic prefix overlaps with the corresponding copied segment at the end of the effective symbol, so that the autocorrelation function obtains a second peak.

[0165] Figure 7 The figure schematically shows a synchronization sequence simulation diagram generated according to an embodiment of the present disclosure.

[0166] like Figure 7 As shown in the figure, the PSS (Primary synchronization signal) generated according to the signal format protocol is an M sequence, and its value is .

[0167] According to the embodiments of the present disclosure, a synchronization sequence is generated based on the specific format protocol of the reference signal, thereby achieving accurate positioning of the starting position of each signal frame within the reference signal; based on the internal periodicity of the symbol, the effective symbol length in the symbol is effectively and relatively accurately obtained by calculating the autocorrelation function; based on the periodicity between symbols, the symbol length is accurately calculated by calculating the cyclic autocorrelation function and further the starting position of the cyclic prefix is obtained; based on the specific structure of the above-mentioned signal frame and the position and length of other structures that may exist according to different specific frame structures within the frame, the positioning of the cyclic prefix is accurately achieved.

[0168] According to an embodiment of the present disclosure, based on the position of the cyclic prefix, the cyclic prefix is removed from the reference signal to generate a new reference signal, including: setting the reference signal value between the starting position of the cyclic prefix and the ending position of the cyclic prefix to zero to obtain a zero signal interval of the reference signal; and adding random noise within the signal zero interval to form a new reference signal.

[0169] According to an embodiment of the present disclosure, the cyclic prefix starting position and the cyclic prefix ending position determine the position of the cyclic prefix in the signal frame structure frame; by setting the cyclic prefix to zero, the cyclic prefix in the reference signal is eliminated; the zeroed signal interval is the position where the cyclic prefix is located.

[0170] According to an embodiment of the present disclosure, by adding random noise in the zeroing interval, it is possible to effectively avoid the occurrence of numerical calculation instability and new secondary peaks or interference noise that may be caused when the cyclic prefix is set to zero and the new reference signal and echo signal are subjected to two-dimensional matching calculation.

[0171] An embodiment of the present disclosure also provides a passive radar side peak suppression device, including: a signal acquisition module, used to obtain a reference signal from an opportunity emission source and an echo signal from a detection target through a passive radar, wherein the echo signal is formed by the detection target reflecting the signal of the opportunity emission source; a signal format recognition module, which detects the signal format of the reference signal and obtains a signal format detection result; a side peak suppression module, which uses a processing strategy corresponding to the signal format detection result to suppress the side peaks of the coherent accumulation result of the passive radar based on the reference signal and the echo signal, and obtain a target coherent accumulation result, wherein the coherent accumulation result is determined based on the reference signal and the echo signal.

[0172] Figure 8 The block diagram of a passive radar side peak suppression device according to an embodiment of the present disclosure is schematically shown.

[0173] like Figure 8 As shown, the passive radar secondary peak suppression device 800 includes a signal acquisition module 810 , a signal format recognition module 820 and a secondary peak suppression module 830 .

[0174] The signal acquisition module 810 is used to acquire a reference signal from an opportunistic transmitter and an echo signal from a detection target through a passive radar. The echo signal is formed by the detection target reflecting the signal from the opportunistic transmitter.

[0175] The signal format identification module 820 is configured to detect the signal format of the reference signal and obtain a signal format detection result.

[0176] The secondary peak suppression module 830 is used to suppress secondary peaks on the coherent accumulation result of the passive radar based on the reference signal and the echo signal using a processing strategy corresponding to the signal format detection result, thereby obtaining a target coherent accumulation result, wherein the coherent accumulation result is determined based on the reference signal and the echo signal.

[0177] According to an embodiment of the present disclosure, the secondary peak suppression module 830 may include an unknown format secondary peak suppression submodule.

[0178] The unknown format secondary peak suppression submodule is used to suppress the secondary peak of the coherent accumulation result of the passive radar based on the reference signal and the echo signal when the signal format detection result is unknown, so as to obtain the target coherent accumulation result.

[0179] According to an embodiment of the present disclosure, the unknown format secondary peak suppression submodule may include: a two-dimensional matching unit, a first coherent accumulation result acquisition unit, and a target coherent accumulation result first acquisition unit.

[0180] The two-dimensional matching unit is used to perform two-dimensional matching calculation on the reference signal and the echo signal to obtain the mutual ambiguity function of the reference signal and the echo signal.

[0181] The first coherent accumulation result acquisition unit is used to determine a function peak with a peak value greater than a first preset threshold from multiple function peaks included in the time delay-frequency shift plane of the mutual ambiguity function, to obtain multiple candidate main peaks; and to obtain a first coherent accumulation result based on the multiple candidate main peaks.

[0182] The target coherent accumulation result first acquisition unit is used to suppress the secondary peak of the first coherent accumulation result based on the positional relationship between the main peak and the secondary peak of the reference signal to obtain the target coherent accumulation result.

[0183] According to an embodiment of the present disclosure, the unknown format secondary peak suppression submodule may further include a main peak and secondary peak position relationship determination unit.

[0184] The main peak and secondary peak position relationship determination unit is used to determine the main peak and secondary peak position relationship of the reference signal.

[0185] According to an embodiment of the present disclosure, the main peak and secondary peak position relationship determination unit may include: a self-ambiguity function calculation subunit, a reference peak acquisition subunit, a first reference peak determination subunit, and a position relationship determination subunit.

[0186] The self-ambiguous function calculation subunit is used to perform a two-dimensional matching operation on the reference signal to obtain the self-ambiguous function of the reference signal.

[0187] The reference peak acquisition subunit is used to determine a function peak with a peak value greater than a second preset threshold from multiple function peaks included in the time delay-frequency shift plane of the self-ambiguity function to obtain multiple reference peaks.

[0188] The first reference peak determining subunit is configured to determine a first reference peak and at least one second reference peak from a plurality of reference peaks, wherein the peak value of the first reference peak is greater than the peak value of each of the at least one second reference peaks.

[0189] The position relationship determination subunit is used to determine the position relationship between the main peak and the secondary peak of the reference signal based on the difference between the position coordinates of the first reference peak and the position coordinates of at least one second reference peak, wherein the position coordinates of the first reference peak include the time delay and frequency shift of the first reference peak.

[0190] According to an embodiment of the present disclosure, the unknown format secondary peak suppression submodule may further include a secondary peak suppression unit.

[0191] The secondary peak suppression unit is used to suppress the secondary peak of the first coherent integration result based on the positional relationship between the main peak and the secondary peak of the reference signal to obtain a target coherent integration result.

[0192] According to an embodiment of the present disclosure, the secondary peak suppression unit may further include: a first target main peak determination subunit, a secondary peak search subunit, and a target coherent accumulation result acquisition subunit.

[0193] The first target main peak determining subunit is configured to determine the candidate main peak with the highest peak value in the first coherent accumulation result as the first target main peak.

[0194] The secondary peak search subunit is used to add the first target main peak to the main peak set, remove the first target main peak and at least one secondary peak from the first coherent accumulation result, and obtain an updated first coherent accumulation result when there is at least one secondary peak corresponding to the secondary peak position information in the first coherent accumulation result; and suppress the secondary peak on the updated first coherent accumulation result based on the positional relationship between the main peak and the secondary peak of the reference signal.

[0195] The target coherent accumulation result obtaining subunit is used to obtain the target coherent accumulation result based on the first coherent accumulation result and the main peak set when there is no secondary peak corresponding to the secondary peak position information in the first coherent accumulation result.

[0196] According to an embodiment of the present disclosure, the unknown format secondary peak suppression submodule may further include a secondary peak position information acquiring unit.

[0197] The secondary peak position information acquiring unit is configured to determine the secondary peak position information of the secondary peak corresponding to the first target main peak based on the positional relationship between the main peak and the secondary peak of the reference signal.

[0198] According to an embodiment of the present disclosure, the secondary peak position information acquiring unit may include: a candidate secondary peak position coordinate determining subunit and a secondary peak position information determining subunit.

[0199] The candidate secondary peak position coordinate determining subunit is configured to obtain the candidate secondary peak position coordinates based on the positional relationship between the primary peak and the secondary peak of the reference signal, taking the position coordinates of the first target primary peak as a starting point.

[0200] The secondary peak position information determining subunit is configured to obtain the secondary peak position information based on a preset guard interval range and with the candidate secondary peak position coordinates as the center.

[0201] According to an embodiment of the present disclosure, the secondary peak suppression module 830 may include a known format secondary peak suppression submodule.

[0202] The known format secondary peak suppression submodule is used to suppress the secondary peak of the coherent accumulation result of the passive radar based on the reference signal and the echo signal when the signal format detection result is a known format, so as to obtain the target coherent accumulation result.

[0203] The known format secondary peak suppression submodule may further include: a cyclic prefix position determining unit, a new reference signal generating unit, and a target coherent accumulation result second acquiring unit.

[0204] The cyclic prefix position determining unit is configured to determine position information of the cyclic prefix in the reference signal according to the signal format of the reference signal.

[0205] The new reference signal generating unit is configured to remove the cyclic prefix from the reference signal based on the position information of the cyclic prefix to generate a new reference signal.

[0206] The second target coherent accumulation result acquisition unit is used to perform two-dimensional matching calculation on the new reference signal and the echo signal to obtain the target coherent accumulation result.

[0207] According to an embodiment of the present disclosure, the cyclic prefix position determination unit may also include: an effective symbol length determination subunit, a symbol length determination subunit, a cyclic prefix length determination subunit, a signal frame start position determination subunit, a cyclic prefix start position determination subunit, a cyclic prefix end position determination subunit, and a cyclic prefix position information determination subunit.

[0208] The effective symbol length determination subunit is used to calculate the autocorrelation function of the reference signal and determine the effective symbol length of the reference signal based on the autocorrelation peak of the autocorrelation function.

[0209] The symbol length determination subunit is configured to calculate a cyclic autocorrelation function of the reference signal and determine the symbol length of the reference signal based on the cyclic autocorrelation function.

[0210] The cyclic prefix length determining subunit is configured to determine the cyclic prefix length of the reference signal based on the effective symbol length and the symbol length.

[0211] The signal frame starting position determination subunit is used to generate a synchronization sequence according to a format protocol of a known format, and perform correlation calculation on the synchronization sequence and a reference signal to obtain the signal frame starting position.

[0212] The cyclic prefix starting position determining subunit is used to determine the cyclic prefix starting position based on the signal frame starting position, the synchronization sequence length and the symbol length of the reference signal.

[0213] The cyclic prefix end position determination subunit is used to determine the cyclic prefix end position based on the cyclic prefix start position of the symbol and the cyclic prefix length of the reference signal.

[0214] The cyclic prefix position information determining subunit is configured to obtain the position information of the cyclic prefix based on the cyclic prefix starting position and the cyclic prefix ending position.

[0215] According to an embodiment of the present disclosure, the new reference signal generating unit may further include: a zeroing subunit and a random noise adding subunit.

[0216] The zeroing subunit is used to set the reference signal value between the cyclic prefix starting position and the cyclic prefix ending position to zero, so as to obtain a zeroing signal interval of the reference signal.

[0217] The random noise adding subunit is used to add random noise in the zero signal interval to form a new reference signal.

[0218] According to the embodiments of the present invention, any number of modules, sub-modules, units, and sub-units, or at least part of the functions of any number of them, can be implemented in one module. According to the embodiments of the present invention, any one or more of the modules, sub-modules, units, and sub-units can be split into multiple modules for implementation. According to the embodiments of the present invention, any one or more of the modules, sub-modules, units, and sub-units can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application-specific integrated circuit (ASIC), or can be implemented by hardware or firmware in any other reasonable way of integrating or packaging the circuit, or can be implemented in any one of the three implementation methods of software, hardware, and firmware, or in any appropriate combination of any of them. Alternatively, according to the embodiments of the present invention, one or more of the modules, sub-modules, units, and sub-units can be at least partially implemented as a computer program module, which can perform the corresponding functions when the computer program module is executed.

[0219] For example, any multiple of the signal acquisition module 810, the signal format identification module 820, and the secondary peak suppression module 830 can be combined into a single module / unit / sub-unit, or any one of these modules / units / sub-units can be split into multiple modules / units / sub-units. Alternatively, at least part of the functionality of one or more of these modules / units / sub-units can be combined with at least part of the functionality of other modules / units / sub-units and implemented in a single module / unit / sub-unit.

[0220] According to an embodiment of the present disclosure, at least one of the signal acquisition module 810, the signal format identification module 820, and the secondary peak suppression module 830 can be at least partially implemented as a hardware circuit, such as a field programmable gate array (FPGA), a programmable logic array (PLA), a system on a chip, a system on a substrate, a system on a package, an application-specific integrated circuit (ASIC), or can be implemented in hardware or firmware by any other reasonable means of circuit integration or packaging, or can be implemented in any one of the three implementation methods of software, hardware, and firmware, or in any appropriate combination of any of these. Alternatively, at least one of the signal acquisition module 810, the signal format identification module 820, and the secondary peak suppression module 830 can be at least partially implemented as a computer program module, which can perform the corresponding function when executed.

[0221] It should be noted that the passive radar secondary peak suppression device part in the embodiment of the present disclosure corresponds to the passive radar secondary peak suppression method part in the embodiment of the present disclosure. The description of the passive radar secondary peak suppression device part specifically refers to the passive radar secondary peak suppression method part, which will not be repeated here.

[0222] An embodiment of the present disclosure further provides an electronic device, comprising: one or more processors; and a memory for storing one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors execute the above-mentioned passive radar side peak suppression method.

[0223] Figure 9 The figure schematically shows a block diagram of an electronic device suitable for a passive radar side peak suppression method according to an embodiment of the present disclosure.

[0224] Figure 9 The electronic device shown is only an example and should not limit the functions and scope of use of the embodiments of the present disclosure.

[0225] like Figure 9As shown, the electronic device 900 according to an embodiment of the present disclosure includes a processor 901, which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 902 or a program loaded from a storage unit 908 into a random access memory (RAM) 903. The processor 901 may include, for example, a general-purpose microprocessor (e.g., a CPU), an instruction set processor and / or a related chipset and / or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor 901 may also include onboard memory for caching purposes. The processor 901 may include a single processing unit or multiple processing units for performing different actions of the method flow according to an embodiment of the present disclosure.

[0226] Various programs and data required for the operation of the electronic device 900 are stored in the RAM 903. The processor 901, the ROM 902, and the RAM 903 are connected to each other via a bus 904. The processor 901 executes the various operations of the method flow according to the embodiment of the present disclosure by executing the programs in the ROM 902 and / or the RAM 903. It should be noted that the programs may also be stored in one or more memories other than the ROM 902 and the RAM 903. The processor 901 may also execute the various operations of the method flow according to the embodiment of the present disclosure by executing the programs stored in the one or more memories.

[0227] According to an embodiment of the present disclosure, electronic device 900 may further include an input / output (I / O) interface 905, which is also connected to bus 904. Electronic device 900 may also include one or more of the following components connected to I / O interface 905: an input section 906 including a keyboard, mouse, etc.; an output section 907 including devices such as a cathode ray tube (CRT), liquid crystal display (LCD), and speakers; a storage section 908 including a hard disk; and a communication section 909 including a network interface card such as a LAN card or modem. Communication section 909 performs communication processing via a network such as the Internet. A drive 910 is also connected to I / O interface 905 as needed. Removable media 911, such as a magnetic disk, optical disk, magneto-optical disk, semiconductor memory, etc., is installed in drive 910 as needed, so that computer programs read from the removable media can be installed into storage section 908 as needed.

[0228] According to an embodiment of the present disclosure, the method flow according to an embodiment of the present disclosure can be implemented as a computer software program. For example, an embodiment of the present disclosure includes a computer program product, which includes a computer program carried on a computer-readable storage medium, and the computer program includes a program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from the network through the communication part 909, and / or installed from the removable medium 911. When the computer program is executed by the processor 901, the above-mentioned functions defined in the system of the embodiment of the present disclosure are executed. According to an embodiment of the present disclosure, the system, equipment, device, module, unit, etc. described above can be implemented by a computer program module.

[0229] The present disclosure also provides a computer-readable storage medium, which may be included in the device / apparatus / system described in the above embodiments, or may exist independently and not be incorporated into the device / apparatus / system. The computer-readable storage medium carries one or more programs, and when executed, implements the method according to the embodiments of the present disclosure.

[0230] According to embodiments of the present disclosure, a computer-readable storage medium may be a non-volatile computer-readable storage medium. Examples include, but are not limited to, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present disclosure, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0231] For example, according to an embodiment of the present disclosure, the computer-readable storage medium may include the ROM 902 and / or the RAM 903 described above and / or one or more memories other than the ROM 902 and the RAM 903 .

[0232] An embodiment of the present disclosure also includes a computer program product, which includes a computer program, which contains program code for executing the method provided by the embodiment of the present disclosure. When the computer program product runs on an electronic device, the program code is used to enable the electronic device to implement the target recognition method based on frequency modulated continuous wave laser radar provided by the embodiment of the present disclosure.

[0233] When the computer program is executed by the processor 901, the above functions defined in the system / device of the embodiment of the present disclosure are performed. According to the embodiment of the present disclosure, the system, device, module, unit, etc. described above can be implemented by a computer program module.

[0234] In one embodiment, the computer program may be stored on a tangible storage medium such as an optical storage device or a magnetic storage device. In another embodiment, the computer program may be transmitted and distributed in the form of a signal on a network medium, downloaded and installed via the communication portion 909, and / or installed from a removable medium 911. The program code contained in the computer program may be transmitted using any appropriate network medium, including but not limited to wireless, wired, or any suitable combination thereof.

[0235] According to an embodiment of the present disclosure, the program code for executing the computer program provided by the embodiment of the present disclosure can be written in any combination of one or more programming languages. Specifically, these computer programs can be implemented using high-level procedural and / or object-oriented programming languages, and / or assembly / machine languages. Programming languages include, but are not limited to, languages such as Java, C++, Python, "C" or similar programming languages. The program code can be executed entirely on the user computing device, partially on the user device, partially on a remote computing device, or entirely on a remote computing device or server. In cases involving a remote computing device, the remote computing device can be connected to the user computing device through any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computing device (for example, using an Internet service provider to connect via the Internet).

[0236] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of the systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each box in the flowchart or block diagram can represent a module, program segment, or part of the code, which contains one or more executable instructions for implementing the specified logical functions. It should also be noted that in some alternative implementations, the functions marked in the boxes can also occur in an order different from that marked in the accompanying drawings. For example, two boxes shown in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, as well as the combination of boxes in the block diagram or flowchart, can be implemented using a dedicated hardware-based system that performs the specified functions or operations, or can be implemented using a combination of dedicated hardware and computer instructions. It will be understood by those skilled in the art that the features described in the various embodiments of the present disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present disclosure. In particular, without departing from the spirit and teachings of the present disclosure, the features described in the various embodiments of the present disclosure may be combined and / or coupled in various ways, and all of these combinations and / or couplings fall within the scope of the present disclosure.

[0237] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A passive radar side peak suppression method, characterized in that: The method comprises: Acquiring a reference signal from an opportunistic transmitter and an echo signal from a detection target by a passive radar, wherein the echo signal is formed by the detection target reflecting the signal from the opportunistic transmitter; detecting a signal format of the reference signal to obtain a signal format detection result; and Using a processing strategy corresponding to the signal format detection result, based on the reference signal and the echo signal, a coherent integration result of the passive radar is subjected to secondary peak suppression to obtain a target coherent integration result, wherein the coherent integration result is determined based on the reference signal and the echo signal.

2. The passive radar side peak suppression method according to claim 1, characterized in that: When the signal format detection result is unknown, performing secondary peak suppression on the coherent integration result of the passive radar based on the reference signal and the echo signal to obtain a target coherent integration result includes: performing a two-dimensional matching calculation on the reference signal and the echo signal to obtain a mutual ambiguity function between the reference signal and the echo signal; Determining a function peak having a peak value greater than a first preset threshold from a plurality of function peaks included in the time delay-frequency shift plane of the mutual ambiguity function, to obtain a plurality of candidate main peaks; Based on the multiple candidate main peaks, obtaining a first coherent accumulation result; and Based on the positional relationship between the main peak and the secondary peak of the reference signal, the secondary peak is suppressed on the first coherent integration result to obtain the target coherent integration result.

3. The passive radar side peak suppression method according to claim 2, characterized in that: Also includes: Performing a two-dimensional matching operation on the reference signal to obtain a self-fuzzy function of the reference signal; Determining a function peak having a peak value greater than a second preset threshold from a plurality of function peaks included in the time delay-frequency shift plane of the self-ambiguity function to obtain a plurality of reference peaks; determining a first reference peak and at least one second reference peak from the plurality of reference peaks, wherein a peak value of the first reference peak is greater than a peak value of each of the at least one second reference peak; Based on the difference between the position coordinates of the first reference peak and the position coordinates of each of the at least one second reference peak, the position relationship between the main peak and the secondary peak of the reference signal is determined, wherein the position coordinates of the first reference peak include the time delay and frequency shift of the first reference peak.

4. The passive radar side peak suppression method according to claim 2, characterized in that: The performing secondary peak suppression on the first coherent integration result based on the positional relationship between the main peak and the secondary peak of the reference signal to obtain the target coherent integration result includes: Determine the candidate main peak with the highest peak value in the first coherent accumulation result as the first target main peak; When at least one secondary peak corresponding to the secondary peak position information exists in the first coherent integration result, adding the first target main peak to the main peak set, removing the first target main peak and the at least one secondary peak from the first coherent integration result to obtain an updated first coherent integration result, and performing secondary peak suppression on the updated first coherent integration result based on a positional relationship between a main peak and secondary peaks of the reference signal; When there is no secondary peak corresponding to the secondary peak position information in the first coherent integration result, the target coherent integration result is obtained based on the first coherent integration result and the main peak set.

5. The passive radar side peak suppression method according to claim 4, characterized in that: The determining, based on the positional relationship between the main peak and the secondary peak of the reference signal, the secondary peak position information of the secondary peak corresponding to the first target main peak includes: Taking the position coordinates of the first target main peak as a starting point, obtaining the position coordinates of the candidate secondary peak based on the positional relationship between the main peak and the secondary peak of the reference signal; The secondary peak position information is obtained based on a preset guard interval range and with the candidate secondary peak position coordinates as the center.

6. The passive radar side peak suppression method according to claim 1, characterized in that: When the signal format detection result is a known format, performing secondary peak suppression on the coherent integration result of the passive radar based on the reference signal and the echo signal to obtain a target coherent integration result includes: determining, according to a signal format of the reference signal, position information of a cyclic prefix in the reference signal; Based on the position information of the cyclic prefix, removing the cyclic prefix from the reference signal to generate a new reference signal; A two-dimensional matching calculation is performed on the new reference signal and the echo signal to obtain a target coherent accumulation result.

7. The passive radar side peak suppression method according to claim 6, characterized in that: The determining, according to the signal format of the reference signal, position information of a cyclic prefix in the reference signal includes: Calculating an autocorrelation function of the reference signal, and determining an effective symbol length of the reference signal based on an autocorrelation peak of the autocorrelation function; calculating a cyclic autocorrelation function of the reference signal, and determining a symbol length of the reference signal based on the cyclic autocorrelation function; determining a cyclic prefix length of the reference signal based on the effective symbol length and the symbol length; Generate a synchronization sequence according to the format protocol of the known format, and perform correlation calculation on the synchronization sequence and the reference signal to obtain a signal frame starting position; Determining a cyclic prefix starting position based on the signal frame starting position, the synchronization sequence length, and the symbol length of the reference signal; Determining a cyclic prefix end position based on a cyclic prefix start position of the symbol and a cyclic prefix length of the reference signal; and The position information of the cyclic prefix is obtained based on the cyclic prefix starting position and the cyclic prefix ending position.

8. The passive radar side peak suppression method according to claim 6 or 7, characterized in that: The removing the cyclic prefix from the reference signal based on the position of the cyclic prefix to generate a new reference signal includes: Setting the reference signal value between the cyclic prefix starting position and the cyclic prefix ending position to zero to obtain a zero signal interval of the reference signal; Random noise is added in the zero signal interval to form a new reference signal.

9. A passive radar secondary peak suppression device, characterized in that: include: a signal acquisition module, configured to acquire a reference signal from an opportunity emission source and an echo signal from a detection target through a passive radar, wherein the echo signal is formed by the detection target reflecting the reference signal; Signal format recognition module: detects the signal format of the reference signal and obtains a signal format detection result; A secondary peak suppression module is configured to perform secondary peak suppression on a coherent accumulation result of the passive radar based on the reference signal and the echo signal using a processing strategy corresponding to the signal format detection result, thereby obtaining a target coherent accumulation result, wherein the coherent accumulation result is determined based on the reference signal and the echo signal.

10. An electronic device, characterized in that: include: one or more processors; a memory for storing one or more programs, When the one or more programs are executed by the one or more processors, the one or more processors are enabled to execute the passive radar side peak suppression method according to any one of claims 1 to 8.

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