A method for coherent processing of multi-base radar received signals

Abstract

The present invention discloses a method for coherent processing of multi-base radar received signals, which is used when a distributed radar system works in a tracking mode, including: determining a probability density function of a phase estimation difference according to the echo observation number and a signal-to-noise ratio estimate of a historical echo observation; estimating the detection probability of a distributed coherent detector and a non-coherent detector according to the signal-to-noise ratio estimate of a current echo observation and the probability density function, and selecting between calculating global test statistics of distributed coherent and non-coherent detectors by comparing the two detection probabilities; calculating the selected global test statistic according to the current echo observation; and determining a target detection result according to the calculated global test statistic. The present invention avoids the problem of poor target detection performance caused by a low signal-to-noise ratio of an echo observation when the distributed radar system works in a tracking mode, and effectively improves the target detection probability of a distributed coherent radar system during target tracking.

Description

Technical Field

[0001] The invention belongs to the field of radar, and in particular relates to a method for coherent processing of multi-base radar received signals. Background Art

[0002] The distributed coherent radar system includes a fusion center and multiple radar stations. Among them, multiple radar stations receive echo signals from the same surveillance area. Each radar channel preprocesses the received signal to form echo observations or local test statistics, and transmits them to the fusion center through wireless or wired communication. The fusion center fuses all echo observations or local test statistics to determine whether the target exists in the surveillance area. Specifically, the detectors used by the fusion center are divided into coherent detectors and non-coherent detectors. When the target echo information parameters are known, the detection performance of the coherent detector is better than that of the non-coherent detector. The coherent detector needs to obtain the phase information of the target echo component in the echo signal of the same spatial resolution unit of each radar station; while for the non-coherent detector, each radar station does not need to obtain phase information, but due to its simple operation, it is often used in engineering.

[0003] The working modes of the distributed coherent radar system are divided into search mode and tracking mode. First, in the search mode, each radar station is unknown to the phase information of the echo observation received at the current moment, so the distributed coherent radar system uses a non-coherent detector to detect the target of interest in the monitoring space. Once the target is detected, the distributed coherent radar system will switch from the search mode to the tracking mode. In the tracking mode, the echo observation received by the distributed coherent radar system is the echo signal of the target. Therefore, the phase of the target echo component in the currently received echo observation can be estimated and obtained through the historical echo observation. At this time, in order to achieve a higher detection probability, the distributed coherent radar system uses a coherent detector in the tracking mode to fuse and judge the echo observations received by each radar. However, in the process of radar tracking the target, under the same phase estimation method, due to the different numbers of received echo observations and different signal-to-noise ratio estimates, the estimation accuracy of the phase of the echo observations of each radar varies. Therefore, in the tracking mode, the performance of coherent fusion target detection using a coherent detector is greatly affected by the phase estimation accuracy. In particular, when the phase estimation accuracy is low, the performance of distributed coherent detection will be worse than that of distributed non-coherent detection. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method for coherent processing of multi-base radar received signals.

[0005] The technical problem to be solved by the present invention is achieved through the following technical solutions:

[0006] A method for coherent processing of multi-base radar received signals, used when a distributed radar system operates in a tracking mode, the method comprising:

[0007] Determine the probability density function of the phase estimation difference of each radar station according to the echo observation number and the signal-to-noise ratio estimation value of the historical echo observation quantity of each radar station;

[0008] estimating the detection probabilities of the distributed coherent detector and the distributed non-coherent detector based on the estimated signal-to-noise ratio of the current echo observations of each radar station and the determined probability density function, and selecting between calculating the global test statistic of the distributed coherent detector and calculating the global test statistic of the distributed non-coherent detector by comparing the two detection probabilities;

[0009] Calculate the selected global test statistic based on the current echo observations of each radar station;

[0010] The target detection result is determined based on the calculated global test statistic.

[0011] Optionally, determining a probability density function of a phase estimation difference of each radar station according to the echo observation number and the signal-to-noise ratio estimation value of the historical echo observation quantity of each radar station includes:

[0012] For each radar station, according to the echo observation number and the signal-to-noise ratio estimation value of the historical echo observation quantity of the radar station, the corresponding probability density function parameter value is searched from the preset lookup table; the found probability density function parameter value is substituted into the preset probability density function of the phase estimation difference to obtain the probability density function of the phase estimation difference of the radar station;

[0013] Among them, the lookup table includes multiple groups of correspondences, and the correspondences are the correspondences between the echo observation numbers and the signal-to-noise ratio estimation values ​​and the probability density function parameter values; the correspondences are obtained by optimizing the probability density function parameter values ​​so that the detection probability of the distributed coherent detector calculated by the probability density function is close to the true detection probability.

[0014] Optionally, the probability density function is:

[0015] ;

[0016] in, Represents the phase estimation error The probability density function of is the independent variable of the probability density function, , , and are the probability density function parameter values, , , , ,and ; represents the natural exponential function, represents the error function; Indicates The phase estimate difference of the radar stations.

[0017] Optionally, estimating the detection probability of the distributed coherent detector and the distributed non-coherent detector according to the signal-to-noise ratio estimation value of the current echo observation quantity of each radar station and the determined probability density function includes:

[0018] According to the estimated signal-to-noise ratio of the current echo observation of each radar station and the determined probability density function, the detection probability of the distributed coherent detector is calculated using a preset coherent detection probability calculation formula;

[0019] The coherent detection probability calculation formula is:

[0020] ;

[0021] in, represents the right tail function of the standard normal distribution, is the global detection threshold of the distributed coherent detector, ; , Indicates The estimated signal-to-noise ratio of the current echo observations of the radar station, , is the total number of radar stations; Indicates The target amplitude preset value of the echo signal received by each radar station; Indicates The phase estimation difference of the radar stations is , Represents the transpose of a matrix; , , The phase estimation error The probability density of According to Computed detection probability of distributed coherent detector;

[0022] According to the estimated signal-to-noise ratio of the current echo observation of each radar station, the detection probability of the distributed non-coherent detector is calculated using the preset non-coherent detection probability calculation formula;

[0023] The non-coherent detection probability calculation formula is:

[0024] ;

[0025] in, express Marcum- Q function, , is the global detection threshold of the distributed non-coherent detector; According to Computed detection probability for distributed non-coherent detectors.

[0026] Optionally, selecting between computing a global test statistic for a distributed coherent detector and computing a global test statistic for a distributed incoherent detector comprises:

[0027] determining whether the current detector is a distributed coherent detector or a distributed non-coherent detector;

[0028] like , then choose to calculate the global test statistic of the current detector;

[0029] like ,and , then choose to calculate the global test statistic of the distributed coherent detector;

[0030] like ,and , then choose to calculate the global test statistic of the distributed non-coherent detector;

[0031] in, is the preset tolerable detection probability difference.

[0032] Optionally, the global test statistic of the distributed coherent detector is calculated as follows:

[0033] ;

[0034] in, Indicates The current echo observations of the radar stations, , is the total number of radar stations; Indicates The target amplitude preset value of the echo signal received by each radar station; Indicates Radar station pair The estimated value of the phase component of Indicates the real part operation, the upper right represents the conjugate transpose of a matrix, , superscript right represents the transpose of a matrix, , Indicates The estimated signal-to-noise ratio of the current echo observations of the radar station, Represents the global test statistic of the distributed coherent detector.

[0035] Optionally, the global test statistic of the distributed non-coherent detector is calculated as follows:

[0036] ;

[0037] in, Indicates The radar station receives Frame echo observation, , is the total number of radar stations; Represents the global test statistic of the distributed noncoherent detector.

[0038] Optionally, determining a target detection result according to the calculated global test statistic includes:

[0039] For the selected global test statistic, a probability density function of the global test statistic under the assumption that the target does not exist is constructed, and a corresponding global threshold is calculated according to the probability density function and the global false alarm probability;

[0040] The target detection result is determined based on the calculated global test statistic and the corresponding global threshold.

[0041] Optionally, when choosing to calculate the global test statistic of the distributed coherent detector, the probability density function of the global test statistic is:

[0042] ;

[0043] The global detection threshold is calculated by the following formula:

[0044] ;

[0045] in, represents the right tail function of the standard normal distribution, represents the global test statistic of the distributed coherent detector, represents the global false alarm probability, is the global detection threshold of the distributed coherent detector; Indicates about The probability density function of .

[0046] Optionally, when choosing to calculate the global test statistic of a distributed non-coherent detector, the probability density function of the global test statistic is:

[0047] ;

[0048] The global detection threshold is calculated by the following formula:

[0049] ;

[0050] in, represents the global test statistic of the distributed non-coherent detector, represents the global false alarm probability, is the total number of radar stations, represents the incomplete gamma function, is the global detection threshold of the distributed non-coherent detector; Indicates about The probability density function of .

[0051] The method for coherent processing of multi-base radar received signals provided by the present invention aims at the problem that the detection performance is affected by the phase estimation accuracy when a distributed coherent radar system uses a coherent detector to perform coherent fusion target detection in a tracking mode. When the distributed radar system works in the tracking mode, the probability density function of the phase estimation difference of each radar station is determined according to the echo observation number and the signal-to-noise ratio estimation value of the historical echo observation quantity of each radar station, the detection probability of the distributed coherent detector and the distributed non-coherent detector is estimated according to the signal-to-noise ratio estimation value of the current echo observation quantity of each radar station and the determined probability density function, and by comparing the two detection probabilities, a choice is made between calculating the global test statistic of the distributed coherent detector and calculating the global test statistic of the distributed non-coherent detector, so that the distributed radar system can realize the dynamic switching of coherent and non-coherent detection in the process of target tracking, ensure that the detection probability of the target is kept at a high level, and solve the problem of low distributed coherent detection performance due to poor phase estimation accuracy in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a flow chart of a method for coherent processing of multi-base radar received signals provided by an embodiment of the present invention;

[0053] Figure 2 is a flow chart of another method for coherent processing of multi-base radar received signals provided by an embodiment of the present invention;

[0054] Figure 3 FIG. 4 shows a curve showing a change in the detection probability of the current echo observation amount with the estimated signal-to-noise ratio under different echo observation numbers and different estimated signal-to-noise ratio values ​​of the historical echo observation amount in an embodiment of the present invention. DETAILED DESCRIPTION

[0055] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0056] In view of the fact that the performance of coherent fusion target detection using a coherent detector is greatly affected by the phase estimation accuracy when the distributed radar system works in the tracking mode in the prior art, in order to solve this problem and ensure that the detection probability of the target by the distributed radar system remains at a high level, an embodiment of the present invention provides a method for coherent processing of multi-base radar received signals, which is used when the distributed radar system works in the tracking mode. The multi-base radar system is also a distributed radar system, and the distributed radar system includes a fusion center and A radar station, is the total number of radar stations, See also Figure 1 The distributed coherent radar target detection method in tracking mode provided by the embodiment of the present invention comprises the following steps:

[0057] S10. Determine the probability density function of the phase estimation difference of each radar station according to the echo observation number and the signal-to-noise ratio estimation value of the historical echo observation quantity of each radar station.

[0058] Specifically, for A radar station can obtain a signal-to-noise ratio estimation value by performing signal-to-noise ratio estimation on the frame of echo observations each time it receives a new frame of echo observations. Thus, a signal-to-noise ratio estimation value of each historical echo observation can be obtained. The signal-to-noise ratio estimation can be implemented using a maximum likelihood estimation method, which is not limited in the embodiment of the present invention.

[0059] Then, for each radar station, the corresponding probability density function parameter value is looked up from a preset lookup table based on the number of echo observations and the signal-to-noise ratio estimate of the historical echo observations of the radar station; the found probability density function parameter value is substituted into the preset probability density function of the phase estimation difference to obtain the probability density function of the phase estimation difference of the radar station.

[0060] The above-mentioned lookup table includes multiple sets of correspondences, which are the correspondences between the echo observation number and the signal-to-noise ratio estimation value and the probability density function parameter value; the correspondence is obtained by optimizing the probability density function parameter value so that the detection probability of the distributed coherent detector calculated by the probability density function is close to the true detection probability.

[0061] Among them, the probability density function of the phase estimation difference is:

[0062] ;

[0063] in, Represents the phase estimation error The probability density function of is the independent variable of the probability density function, , , and are the probability density function parameter values, , , , ,and ; represents the natural exponential function, represents the error function; Indicates The phase estimate difference of the radar stations.

[0064] When pre-building the lookup table, a large number of distributed coherent detectors are used for target detection, and the detection probability is statistically calculated to obtain the true detection probability under different observation conditions. The observation conditions mentioned here include the number of echo observations and the corresponding signal-to-noise ratio estimates. Then, given the observation conditions, by performing phase estimation on the current echo observation, the phase estimation value is subtracted from the preset true phase value to obtain the phase estimation difference; the phase estimation difference is substituted into the above-mentioned probability density function of the phase estimation difference, and by transforming different probability density function parameter values, a set of optimal probability density function parameters can be obtained, so that under the current given observation conditions, the detection probability of the distributed coherent detector calculated by the probability density function is close to the true detection probability under the same observation conditions. Therefore, by giving different fixed observation conditions, the preferred probability density function parameter values ​​corresponding to various observation conditions can be obtained, so as to construct the above-mentioned lookup table accordingly.

[0065] Among them, the phase estimation of the current echo observation includes: Each radar station first determines the parameters of the phase-locked loop, which includes the signal accumulation number of the low-pass filter. and the loop filter coefficients and The radar station will then The historical echo observations at time Input to the phase-locked loop, the phase-locked loop observes the current echo Perform phase estimation and obtain the phase estimation value , assuming the true phase value is , then the phase estimation error , . is the echo observation number of the historical echo observation, and the current echo observation is also the Frame echo observation, The frame echo observation and the echo observation before it are all historical echo observations.

[0066] S20. Estimate the detection probabilities of the distributed coherent detector and the distributed incoherent detector based on the estimated signal-to-noise ratio of the current echo observations of each radar station and the determined probability density function, and choose between calculating the global test statistic of the distributed coherent detector and calculating the global test statistic of the distributed incoherent detector by comparing the two detection probabilities.

[0067] Specifically, based on the signal-to-noise ratio estimation value of the current echo observation quantity of each radar station and the determined probability density function, the detection probability of the distributed coherent detector and the distributed non-coherent detector is estimated, including:

[0068] (1) calculating the detection probability of the distributed coherent detector using a preset coherent detection probability calculation formula based on the signal-to-noise ratio estimation value of the current echo observation of each radar station and the determined probability density function;

[0069] The formula for calculating the coherent detection probability is:

[0070] ;

[0071] in, represents the right tail function of the standard normal distribution, is the global detection threshold of the distributed coherent detector, ; , Indicates The estimated signal-to-noise ratio of the current echo observations of the radar station, , is the total number of radar stations; Indicates The target amplitude preset value of the echo signal received by each radar station; Indicates The phase estimation difference of the radar stations is , Represents the transpose of a matrix; , , The phase estimation error The probability density of According to Computed detection probability of distributed coherent detector;

[0072] In addition, when the lookup table is pre-built, the method of calculating the detection probability of the distributed coherent detector through the probability density function is also implemented using the coherent detection probability calculation formula.

[0073] (2) calculating the detection probability of the distributed non-coherent detector according to the estimated signal-to-noise ratio of the current echo observation of each radar station using a preset non-coherent detection probability calculation formula;

[0074] The calculation formula of non-coherent detection probability is:

[0075] ;

[0076] in, express Marcum- Q function, , is the global detection threshold of the distributed non-coherent detector; According to Computed detection probability for distributed non-coherent detectors.

[0077] Thus, two probabilities are estimated: the detection probability of the distributed coherent detector and the detection probability of the distributed non-coherent detector. Then, by comparing the two detection probabilities, a choice is made between calculating the global test statistic of the distributed coherent detector and calculating the global test statistic of the distributed non-coherent detector, specifically including:

[0078] (1) determining whether the current detector is a distributed coherent detector or a distributed non-coherent detector;

[0079] (2-1) If , then choose to calculate the global test statistic of the current detector;

[0080] (2-2) If ,and , then choose to calculate the global test statistic of the distributed coherent detector;

[0081] (2-3) If ,and , then choose to calculate the global test statistic of the distributed non-coherent detector;

[0082] in, is the preset tolerable detection probability difference. The reason is that when the detection probabilities of the distributed coherent detector and the distributed non-coherent detector are almost the same, there is no need to switch the detector, but the detector used in the previous frame can continue to be used. In fact, the switching of the detector means that the radar system needs to consume additional resources to process, so by setting , so that there is a certain gap in the detection probabilities of the two detectors, and then we decide which detector to use.

[0083] S30. Calculate the selected global test statistic according to the current echo observation quantity of each radar station.

[0084] Specifically, when the global test statistic of the distributed coherent detector is selected to be calculated, the calculation method of the global test statistic of the distributed coherent detector is as follows:

[0085] ;

[0086] in, Indicates The current echo observations of the radar stations, , is the total number of radar stations; Indicates The target amplitude preset value of the echo signal received by each radar station; Indicates Radar station pair The estimated value of the phase component of Indicates the real part operation, the upper right represents the conjugate transpose of a matrix, , superscript right represents the transpose of a matrix, , Indicates The estimated signal-to-noise ratio of the current echo observations of the radar station, Represents the global test statistic of the distributed coherent detector.

[0087] When you choose to compute the global test statistic for a distributed non-coherent detector, the global test statistic for a distributed non-coherent detector is computed as follows:

[0088] ;

[0089] in, Indicates The radar station receives Frame echo observation, , is the total number of radar stations; Represents the global test statistic of the distributed noncoherent detector.

[0090] S40. Determine a target detection result according to the calculated global test statistic.

[0091] Specifically, for the selected global test statistic, a probability density function of the global test statistic under the assumption that the target does not exist is constructed, and a global threshold is calculated based on the probability density function and the global false alarm probability; the target detection result is determined based on the calculated global test statistic and the corresponding global threshold.

[0092] Among them, when choosing to calculate the global test statistic of the distributed coherent detector, the global test statistic The probability density function of is:

[0093] ;

[0094] in, represents the right tail function of the standard normal distribution, Indicates that the independent variable is of function; Indicates about The probability density function of .

[0095] Correspondingly, the global detection threshold is calculated by the following formula:

[0096] ;

[0097] in, is the global detection threshold of the distributed coherent detector, Represents the global false alarm probability. In practice, the above formula is used to solve By setting the global false alarm probability , to solve the above equation .

[0098] When choosing to calculate the global test statistic of a distributed non-coherent detector, the probability density function of the global test statistic is:

[0099] ;

[0100] here, represents the incomplete gamma function, Indicates that the independent variable is and The incomplete gamma function of Indicates about The probability density function of .

[0101] Correspondingly, the global detection threshold is calculated by the following formula:

[0102] .

[0103] in, represents the global test statistic of the distributed non-coherent detector, represents the global false alarm probability, is the total number of radar stations, represents the incomplete gamma function, is the global detection threshold of the distributed non-coherent detector.

[0104] After calculating the global test statistic and the corresponding global detection threshold, it is determined whether the global test statistic is greater than the corresponding global detection threshold; if so, it is determined that the target is detected, otherwise it is determined that the target is not detected.

[0105] In one implementation, when no target is detected, it can be further determined whether the distributed radar target detection system has been continuously If no target is detected in any frame, the detection ends; otherwise, each radar station receives the next frame of target echo observation data and continues to detect the target. It is the upper limit of the number of frames used to decide whether to end the detection. Based on this implementation, Figure 2 Another distributed coherent radar target detection method in tracking mode provided by an embodiment of the present invention is shown, comprising the following steps:

[0106] a. All radar stations receive the current Frame echo observation;

[0107] b. The fusion center determines the probability density function of the phase estimation difference of each radar station based on the echo observation number and signal-to-noise ratio estimation value of the historical echo observation of each radar station; calculates the detection probability of the distributed coherent detector based on the signal-to-noise ratio estimation value of the current echo observation of each radar station and the determined probability density function. and the detection probability of distributed non-coherent detectors ;

[0108] c. Fusion Center Judgment Is it true? If it is true, the current detector is used and the global test statistic of the current detector is calculated ( or ), then execute step e; if not, execute step d;

[0109] d. Fusion center judgment Is it true? If true, calculate , then execute step e; if not, calculate , then execute step e;

[0110] e. The fusion center determines the target detection result based on the global test statistic and the global detection threshold.

[0111] f. Determine whether the target has not been detected in consecutive P frames; if yes, end the detection; if not, , and then return to step a to continue target detection.

[0112] The method for coherent processing of multi-base radar received signals provided by an embodiment of the present invention aims at the problem that the detection performance is affected by the phase estimation accuracy when a distributed coherent radar system uses a coherent detector to perform coherent fusion target detection in a tracking mode. When the distributed radar system works in the tracking mode, the probability density function of the phase estimation difference of each radar station is determined according to the echo observation number and the signal-to-noise ratio estimation value of the historical echo observation quantity of each radar station, and the detection probability of the distributed coherent detector and the distributed non-coherent detector is estimated according to the signal-to-noise ratio estimation value of the current echo observation quantity of each radar station and the determined probability density function. By comparing the two detection probabilities, a choice is made between calculating the global test statistic of the distributed coherent detector and calculating the global test statistic of the distributed non-coherent detector, so that the distributed radar system can realize dynamic switching between coherent and non-coherent detection in the process of target tracking, ensuring that the detection probability of the target is maintained at a high level, and solving the problem of low distributed coherent detection performance due to poor phase estimation accuracy in the prior art.

[0113] The method for coherent processing of multi-base radar received signals provided in the embodiment of the present invention is applied to the fusion center of a distributed coherent radar system, but is certainly not limited thereto.

[0114] The following is a simulation experiment to further illustrate the technical effects of the present invention:

[0115] Parameter settings: The signal-to-noise ratio estimate of the signal received by a single radar station is set between 0dB and 15dB. The signal-to-noise ratio estimate of the echo observation received by each radar station is the same. The background noise is 0 with a mean and a variance of Gaussian white noise, , No. The target amplitude preset value of the echo signal received by each radar station All are set to 10dB, and the signal accumulation of the low-pass filter of the phase-locked loop of all radar stations is are all set to 15, the coefficients of the loop filter , , the phase difference estimated by each radar station The probability density function of It is the same. , , , , , the inter-frame interval is set to 0.01s, and the global false alarm rate is set to 10 -4 , , the tolerable detection probability difference when switching detectors Set to 0.05.

[0116] Simulation hardware environment: CPU is Inter Core i7-4790, main frequency is 3.60Ghz, main memory is 8GB.

[0117] Simulation software environment: Windows 10 Professional Edition, MATLAB simulation software.

[0118] Based on the above simulation configuration, under the condition of historical echo observation with a signal-to-noise ratio of 8dB, the actual detection probability change curve of the received current echo observation is as follows: Figure 3 As shown, Figure 3 The horizontal axis represents the signal-to-noise ratio of the current echo observation received by a single radar station, in dB; the vertical axis represents the detection probability of the current echo observation received by the radar station; the curve marked as "non-coherent" is the actual detection probability change curve of the current echo observation received using only a distributed non-coherent detector; the curve marked as "coherent-PLL, 8dB" is the actual detection probability change curve of the current echo observation received with a signal-to-noise ratio of 8dB using the method of an embodiment of the present invention; the curve marked as "coherent-PLL, 10dB" is the actual detection probability change curve of the current echo observation received with a signal-to-noise ratio of 10dB using the method of an embodiment of the present invention; the curve marked as "optimal coherence" is the actual detection probability change curve of the echo observation received using only a distributed coherent detector when the phase of the current echo observation is known. From Figure 3 It can be seen that when the signal-to-noise ratio of the current echo observation is less than 11.8dB, the detection performance of the distributed coherent detector is better than that of the distributed non-coherent detector. Considering the set detection probability tolerance value, in fact, when the signal-to-noise ratio of the current echo observation is between 11.5dB and 12.1dB, the difference in detection probability between the distributed non-coherent detector and the distributed coherent detector is within 0.05. At this time, the radar system does not need to choose the type of detector. When the signal-to-noise ratio of the echo observation is less than 11.5dB, the fusion center uses a distributed coherent detector. When the signal-to-noise ratio of the echo observation is greater than 12.1dB, the fusion center uses a distributed non-coherent detector.

[0119] In addition, from Figure 3 It can be seen that, when the number of echo observations is the same, the greater the signal-to-noise ratio of the historical echo observations, the higher the phase component estimation accuracy of the current echo observations, and the higher the detection probability of the distributed coherent detector. When the signal-to-noise ratio of the historical echo observations is greater, the signal-to-noise ratio corresponding to the intersection of the detection probabilities of the two detectors is greater, and the detection probability corresponding to the intersection is higher. This means that the greater the signal-to-noise ratio of the current echo observations, the higher the detection probability of the distributed non-coherent detector. If the detection probability of the distributed coherent detector is higher than that of the non-coherent detector, a higher phase estimation accuracy is required in the distributed coherent detector.

[0120] Therefore, the embodiment of the present invention can ensure that the detection probability always remains at a high level by selecting the optimal coherent detector between the distributed coherent detector and the distributed non-coherent detector.

[0121] In summary, in the scenario of distributed coherent radar, the embodiment of the present invention chooses between calculating the global test statistic of the distributed coherent detector and calculating the global test statistic of the distributed incoherent detector, so that the distributed coherent radar maintains a high detection probability level for the target during the process of tracking the target, thereby effectively improving the detection probability.

[0122] It should be noted that the terms "first", "second", etc. are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Instead, they are merely examples of devices and methods consistent with some aspects of the present disclosure.

[0123] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0124] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other changes to the disclosed embodiments by viewing the drawings and the disclosed content. In the description of the present invention, the term "comprising" does not exclude other components or steps, "one" or "an" does not exclude multiple situations, and the meaning of "multiple" is two or more, unless otherwise clearly and specifically limited. In addition, certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0125] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A method for coherent processing of multi-base radar received signals, characterized in that: When the distributed radar system is operated in a tracking mode, the method includes: Determine the probability density function of the phase estimation difference of each radar station according to the echo observation number and the signal-to-noise ratio estimation value of the historical echo observation quantity of each radar station; estimating the detection probabilities of the distributed coherent detector and the distributed non-coherent detector based on the estimated signal-to-noise ratio of the current echo observations of each radar station and the determined probability density function, and selecting between calculating the global test statistic of the distributed coherent detector and calculating the global test statistic of the distributed non-coherent detector by comparing the two detection probabilities; Calculate the selected global test statistic based on the current echo observations of each radar station; The target detection result is determined based on the calculated global test statistic.

2. The method according to claim 1, characterized in that According to the echo observation number and signal-to-noise ratio estimation value of the historical echo observation quantity of each radar station, the probability density function of the phase estimation difference of each radar station is determined, including: For each radar station, according to the echo observation number and the signal-to-noise ratio estimation value of the historical echo observation quantity of the radar station, the corresponding probability density function parameter value is searched from the preset lookup table; the found probability density function parameter value is substituted into the preset probability density function of the phase estimation difference to obtain the probability density function of the phase estimation difference of the radar station; Among them, the lookup table includes multiple groups of correspondences, and the correspondences are the correspondences between the echo observation numbers and the signal-to-noise ratio estimation values ​​and the probability density function parameter values; the correspondences are obtained by optimizing the probability density function parameter values ​​so that the detection probability of the distributed coherent detector calculated by the probability density function is close to the true detection probability.

3. The method according to claim 2, characterized in that The probability density function is: in, represents the probability density function of the phase estimation difference Δθn, x is the independent variable of the probability density function, α1, α2, l1 and l2 are all probability density function parameter values, α1≥0, α2≥0, l1≥0, l2≥0, and α1+α2=1; exp(·) represents the natural exponential function, erf(·) represents the error function; Δθn represents the phase estimation difference of the nth radar station.

4. The method according to claim 1, characterized in that: According to the estimated signal-to-noise ratio of the current echo observation of each radar station and the determined probability density function, the detection probability of the distributed coherent detector and the distributed non-coherent detector is estimated, including: According to the estimated signal-to-noise ratio of the current echo observation of each radar station and the determined probability density function, the detection probability of the distributed coherent detector is calculated using a preset coherent detection probability calculation formula; The coherent detection probability calculation formula is: Where Q(·) represents the right tail function of the standard normal distribution, gc is the global detection threshold of the distributed coherent detector, λn,i represents the estimated signal-to-noise ratio of the current echo observation of the nth radar station, n = 1,…,N, N is the total number of radar stations; It indicates the preset value of the target amplitude of the echo signal received by the nth radar station; Δθn indicates the phase estimation difference of the nth radar station, T represents the transpose of the matrix; Δθ=[Δθ1,Δθ2,…ΔθN]T, fΔθ n (Δθn) represents the probability density of the phase estimation difference Δθn; pd1(λi) represents the detection probability of the distributed coherent detector calculated according to λi=[λ1,i,…,λN,i]T; According to the estimated signal-to-noise ratio of the current echo observation of each radar station, the detection probability of the distributed non-coherent detector is calculated using the preset non-coherent detection probability calculation formula; The non-coherent detection probability calculation formula is: Where QN(·) represents the Nth-order Marcum-Q function, gnc is the global detection threshold of the distributed non-coherent detector; pd2(λi) represents the detection probability of the distributed non-coherent detector calculated according to λi=[λ1,i,…,λN,i]T.

5. The method according to claim 4, characterized in that Selecting between computing a global test statistic for a distributed coherent detector and computing a global test statistic for a distributed non-coherent detector by comparing the two detection probabilities comprises: determining whether the current detector is a distributed coherent detector or a distributed non-coherent detector; If |pd1(λi)-pd2(λi)|≤ε1, choose to calculate the global test statistic of the current detector; If |pd1(λi)-pd2(λi)|>ε1, and pd1(λi)-pd2(λi)>ε1, then choose to calculate the global test statistic of the distributed coherent detector; If |pd1(λi)-pd2(λi)|>ε1 and pd2(λi)-pd1(λi)>ε1, then choose to calculate the global test statistic of the distributed non-coherent detector; Among them, ε1 is the preset tolerable detection probability difference.

6. The method according to claim 1, characterized in that The global test statistic of the distributed coherent detector is calculated as follows: Wherein, zn,i represents the current echo observation of the nth radar station, and the current echo observation is the echo observation of the i-th frame; n = 1, ..., N, N is the total number of radar stations; Indicates the preset value of the target amplitude of the echo signal received by the nth radar station; represents the estimated value of the phase component of zn,i by the nth radar station, Indicates the real part operation, and the superscript H indicates the conjugate transpose of the matrix. The superscript T represents the transpose of the matrix, and Tc represents the global test statistic of the distributed coherent detector.

7. The method according to claim 1, characterized in that The global test statistic for a distributed non-coherent detector is calculated as follows: Where zn,i represents the i-th frame echo observation received by the n-th radar station, n = 1,…,N, N is the total number of radar stations; Tnc represents the global test statistic of the distributed non-coherent detector.

8. The method according to claim 1, characterized in that The target detection result is determined based on the calculated global test statistic, including: For the selected global test statistic, a probability density function of the global test statistic under the assumption that the target does not exist is constructed, and a corresponding global threshold is calculated according to the probability density function and the global false alarm probability; The target detection result is determined based on the calculated global test statistic and the corresponding global threshold.

9. The method according to claim 8, characterized in that When choosing to calculate the global test statistic of the distributed coherent detector, the probability density function of the global test statistic is: F0(Tc)=1-Q(Tc); The global detection threshold is calculated by the following formula: pf = Q(gc); Where Q(·) represents the right tail function of the standard normal distribution, Tc represents the global test statistic of the distributed coherent detector, pf represents the global false alarm probability, gc is the global detection threshold of the distributed coherent detector; F0(Tc) represents the probability density function about Tc.

10. The method according to claim 8, characterized in that When choosing to calculate the global test statistic of a distributed non-coherent detector, the probability density function of the global test statistic is: The global detection threshold is calculated by the following formula: Where Tnc is the global test statistic of the distributed non-coherent detector, pf is the global false alarm probability, N is the total number of radar stations, γ(·) is the incomplete gamma function, gnc is the global detection threshold of the distributed non-coherent detector, and F0(Tnc) is the probability density function about Tnc.

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