A PRF Generation Method for Tracking and Measuring Radar

Abstract

The present application proposes a PRF generation method for a tracking and measuring radar, which relates to the field of radar system design. It includes: a search phase: controlling the radar to scan the entire working area in a first low PRF working mode to determine the moving target of interest; a tracking and measuring phase: in response to the determination of the moving target, executing a loop process until it is no longer necessary to track and measure the moving target, wherein the loop process includes: controlling the radar to emit a first predetermined group of a specified number of pulses in a second low PRF working mode to measure the distance and azimuth pitch angle of the moving target; controlling the radar to emit a second predetermined group of a specified number of pulses in a high PRF working mode to measure the radial speed of the moving target; adjusting the radar antenna beam pointing according to the measured distance and azimuth pitch angle of the moving target to ensure that the moving target is illuminated. This technical solution can solve the contradiction between distance measurement and speed measurement in the prior art, and improve the applicability and application effect of the radar system.

Description

Technical Field

[0001] The present application relates to the field of radar system design, and in particular to a PRF generation method for a tracking and measurement radar. Background Art

[0002] Precision tracking and measurement radar is a radar system specially used to detect and track moving targets. It is usually installed on the ground, ship, missile or aircraft, and can achieve real-time measurement and positioning of target objects by transmitting and receiving electromagnetic wave signals. These measurement data are crucial for subsequent decision-making and processing, and can help people accurately understand the movement status of the target.

[0003] In the existing precision tracking and measurement radar system, pulse Doppler radar technology is usually used to achieve the distance and speed measurement of the target. It uses the Doppler principle, that is, two objects moving relative to each other will produce Doppler frequency shift, and the target's speed is calculated by measuring the frequency shift. However, there is a contradiction in the distance and speed measurement of pulse Doppler radar: in order to achieve unambiguous distance measurement, it is necessary to select a suitable pulse repetition frequency (PRF) to meet the requirements of the farthest target distance; and in order to achieve unambiguous speed measurement, a higher PRF is required to meet the requirements of the fastest target speed.

[0004] In practical applications, it is often difficult to find a PRF value that satisfies both distance measurement and speed measurement without ambiguity. Therefore, traditional pulse Doppler radars usually use three PRF working modes: low PRF working mode, medium PRF working mode and high PRF working mode, and select one of the PRF working modes according to different usage scenarios. However, in traditional pulse Doppler radars, once the system design is completed, the corresponding PRF value is fixed and cannot be modified, so there will always be blind spots in distance measurement and speed measurement. These blind spots limit the application effect of pulse Doppler radars in certain specific scenarios. Summary of the invention

[0005] The purpose of this application is to provide a PRF generation method for a tracking and measuring radar, which can realize the accurate tracking and measurement of moving targets by pulse Doppler radar, effectively solve the contradiction between distance measurement and speed measurement existing in the prior art, and improve the applicability and application effect of the radar system.

[0006] This application is implemented as follows:

[0007] In the first aspect, the present application provides a PRF generation method for a tracking and measuring radar, comprising: a search phase: controlling the radar to scan the entire working area in a first low PRF working mode to determine a moving target of interest. A tracking and measuring phase: in response to the determination of the moving target, executing a loop process until it is no longer necessary to track and measure the moving target, wherein the loop process includes: controlling the radar to transmit a first predetermined group of a specified number of pulses in a second low PRF working mode to measure the distance and azimuth pitch angle of the moving target; controlling the radar to transmit a second predetermined group of a specified number of pulses in a high PRF working mode to measure the radial speed of the moving target; and adjusting the radar antenna beam pointing according to the measured distance and azimuth pitch angle of the moving target to ensure that the moving target is illuminated.

[0008] In some implementations, the pulse repetition frequency PRF1 of the radar in the first low PRF operating mode is constrained as follows: Where c is the speed of electromagnetic wave propagation; R max is the maximum distance of the moving target of interest; τ1 is the pulse width of the transmitted signal, and the constraints of τ1 include as well as d is the working ratio.

[0009] In some implementations, the radar is controlled to scan the entire working area in a low PRF working mode to determine a moving target of interest, including: controlling the radar to operate in a first low PRF working mode so that the radar antenna scans in a predetermined azimuth and elevation direction to cover the entire working area; wherein, pulses are emitted and corresponding echo signals are processed while the beam is scanning to determine whether a moving target exists; and when a moving target exists, the distance of the moving target is calculated using the delay of the moving target relative to the radar, otherwise the scanning continues.

[0010] In some implementations, emitting pulses and processing corresponding echo signals while beam scanning includes: controlling the radar to emit N1 pulses, performing coherent accumulation on the received echo signals, and performing pulse compression processing, wherein the constraint condition of N1 is: Among them, v max is the maximum speed of the moving target; R bin is the range gate, and the size of the range gate is: c is the speed of electromagnetic wave propagation; f s is the sampling frequency of the range echo signal, f s ≥2B r , B r is the bandwidth of the transmitted signal.

[0011] In some implementations, the pulse repetition frequency PRF2 of the radar in the second low PRF operating mode is constrained as follows: as well as Among them, c is the speed of electromagnetic wave propagation; R1 is the distance of the moving target, which is the target distance obtained in the search phase or the target distance obtained in the previous cycle of the tracking measurement phase; τ1 is the pulse width of the transmitted signal; k is the predetermined time expansion factor.

[0012] In some implementations, controlling the radar to transmit a first predetermined group of specified number of pulses in the second low PRF operating mode includes: controlling the radar to transmit a first predetermined group of specified number of pulses in the second low PRF operating mode, and performing coherent accumulation and pulse compression processing on received echo signals; wherein the constraint condition of the first predetermined group of specified number N2 is: Among them, v max is the maximum speed of the moving target; R bin is the range gate, and the size of the range gate is: c is the speed of electromagnetic wave propagation; f s is the sampling frequency of the range echo signal, f s ≥2B r , B r is the bandwidth of the transmitted signal.

[0013] In some implementations, the pulse repetition frequency PRF3 of the radar in the high PRF working mode is constrained as follows: Where: λ is the wavelength of the radar transmission signal; v1 is the radial velocity of the moving target relative to the radar, which is the highest velocity of the moving target or the detection velocity of the moving target obtained in the previous cycle of the tracking measurement phase.

[0014] In some implementations, the value of the pulse repetition frequency PRF3 includes: dividing the distance R1 of the moving target detected by the radar in the second low PRF working mode by a preset unambiguous distance width to obtain a floating point number, and determining the value of the pulse repetition frequency PRF3 according to the floating point number; wherein the unambiguous distance width is c is the speed of electromagnetic wave propagation, PRF0 satisfies the constraint condition A predetermined initial value. Let the integer part of the floating point number be n and the decimal part be s, then determine the value of the pulse repetition frequency PRF3 according to the floating point number, including: if n is less than 2 or the value range of s is [0.3, 0.7], then PRF3 = PRF0; if s is less than 0.3, then If s is greater than 0.7, then

[0015] In some implementations, the calculation formula for the number N2 of the second predetermined group of specified numbers is N2=N3+N4, where: c is the speed of electromagnetic wave propagation; R1 is the distance of the target of interest; τ2 is the pulse width of the transmitted signal in the high PRF working mode, d is the radar duty ratio; λ is the wavelength of the radar signal; v max is the maximum speed of the moving target; k is the predetermined time expansion factor; R bin is the range gate; d is the Doppler resolution, ρ v is the speed resolution.

[0016] In some implementations, the selection of the pulse repetition frequency of the radar in the second low PRF operating mode is dynamically adjusted according to the distance of the moving target so that the distance measurement of the moving target is unambiguous; the selection of the pulse repetition frequency of the radar in the high PRF operating mode is dynamically adjusted according to the speed of the moving target and the wavelength of the radar transmission signal so as to make the Doppler frequency measurement unambiguous and ensure that the echo signal of the moving target is within a safety margin between the current transmission signal and the next cycle transmission signal.

[0017] In a second aspect, the present application provides a PRF generation system for a tracking and measurement radar, comprising:

[0018] The search module is used to control the radar to scan the entire working area in the first low PRF working mode to determine the moving target of interest. The tracking and measurement module is used to respond to the determination of the moving target and execute a loop process until it is no longer necessary to track and measure the moving target, wherein the loop process includes: controlling the radar to transmit a first predetermined group of specified number of pulses in the second low PRF working mode to measure the distance and azimuth pitch angle of the moving target; controlling the radar to transmit a second predetermined group of specified number of pulses in the high PRF working mode to measure the radial movement speed of the moving target; and adjusting the radar antenna beam pointing according to the measured distance and azimuth pitch angle of the moving target to ensure that the moving target is illuminated.

[0019] In a third aspect, the present application provides an electronic device, comprising a memory for storing one or more programs; a processor; when the one or more programs are executed by the processor, a method as described in any one of the first aspects is implemented.

[0020] In a fourth aspect, the present application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements a method as described in any one of the above-mentioned first aspects.

[0021] Compared with the prior art, the present invention has at least the following advantages or beneficial effects:

[0022] The present application proposes a PRF generation method for a tracking and measuring radar. In the tracking and measuring stage, the radar can accurately measure the moving target by measuring the distance and angle in the low PRF mode and the speed in the high PRF mode. This provides detailed position and motion information of the target, providing strong support for subsequent analysis and decision-making. And by adjusting the antenna beam pointing in real time to ensure that the radar beam is always irradiated on the target, the technical solution enhances the stability and reliability of target tracking. Even when the target moves quickly or the environment is complex, the target can be continuously tracked. In addition, the present application can flexibly respond to target tracking and measurement requirements in different scenarios by dynamically adjusting the PRF and antenna beam pointing. This improves the adaptability and flexibility of the radar system, enabling it to be widely used in various complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 A diagram showing the relationship between the unambiguous distance speed detection space and the wavelength in one embodiment of the present application;

[0025] Figure 2 A schematic diagram of the relationship between the detection space of a moving target of interest and low PRF, medium PRF and high PRF detection in one embodiment of the present application;

[0026] Figure 3 A flowchart of an embodiment of a PRF generation method for a tracking and measurement radar of the present application;

[0027] Figure 4 This is a schematic diagram of the effect of sidelobe clutter on moving target distance detection under medium or high PRF in one embodiment of the present application;

[0028] Figure 5 This is a schematic diagram showing the effect of sidelobe clutter on moving target distance detection at a low PRF in one embodiment of the present application;

[0029] Figure 6 A diagram showing the relationship between the distance and time of a moving target simulated in an embodiment of the present application;

[0030] Figure 7 A graph showing the relationship between the speed and time of a moving target simulated in an embodiment of the present application;

[0031] Figure 8 A graph showing the relationship between low PRF changes over time during the tracking measurement phase in an embodiment of the present application;

[0032] Fig. 9 This is a graph showing the relationship between high PRF and time during the tracking measurement phase in an embodiment of the present application. DETAILED DESCRIPTION

[0033] To make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme in the embodiment of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, rather than all of the embodiments. The components of the embodiment of the present application described and shown in the accompanying drawings here can be arranged and designed in various different configurations. At the same time in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations.

[0034] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0035] First of all, it should be noted that the technical solution of the present application is mainly applicable to the following application scenarios: tracking and measurement of a single moving target, for example: high-precision measurement of the trajectory of the launch process of artillery shells, missiles, satellites, rockets, etc.

[0036] Pulse Doppler radar has this contradiction in ranging and speed measurement. In terms of ranging, in order to achieve unambiguous ranging, the pulse repetition frequency (PRF) needs to meet the following requirements:

[0037]

[0038] In the above formula, R max The maximum distance of the moving target of interest. The farther the moving target is, the smaller the PRF value is required to be.

[0039] To use unambiguous Doppler velocity measurement, the PRF needs to meet the following requirements:

[0040]

[0041] In the above formula: v maxIndicates the maximum speed of a moving target. The faster the target is, the larger the PRF is required. When the target's distance and speed are both very high, there will not be a PRF that satisfies both distance and speed ambiguity.

[0042] Given a PRF, the maximum unambiguous distance R mu for:

[0043]

[0044] Maximum unambiguous velocity v mu for:

[0045]

[0046] Using R on the distance / speed platform mu ×v mu Represents the unambiguous detection space.

[0047]

[0048] The unambiguous distance and speed measurement space has nothing to do with the choice of PRF, but only with the wavelength of the transmitted signal. Figure 1 As shown, the longer the wavelength (the lower the frequency), the larger the unambiguous distance and velocity space.

[0049] Formula (6) gives the limit of the unambiguous distance measurement and speed measurement combination. Only when the maximum distance and speed meet the above formula, can a PRF be selected to meet both unambiguous distance measurement and unambiguous speed measurement. In practical applications, the above formula is difficult to meet, so pulse Doppler radars often use three PRF working modes to select one of the PRF working modes according to different usage scenarios:

[0050] Operation Mode 1: Low PRF.

[0051] In low PRF working mode, the interval between radar pulse signals is very long, which can ensure that the echo of the farthest target returns to the receiver before the next pulse signal is transmitted. Therefore, the distance of the measured target is not ambiguous, but due to the low PRF, the target speed that can be measured is prone to ambiguity and aliasing.

[0052] Working Mode 2: High PRF

[0053] In the high PRF working mode, the interval between the radar pulse signals is very short, and the echo of the moving target needs many cycles to return to the receiving antenna and be received. Under high PRF, the target distance is seriously ambiguous, and the distance cannot be decoupled by a single set of PRF. However, after Fourier transform, the frequency of the moving target is separated from the frequency of other clutter, thereby achieving unambiguous measurement of the moving target speed.

[0054] Working Mode 3: Medium PRF

[0055] In the medium PRF working mode, the PRF used by the radar is between the low PRF and the high PRF, so the received echo is blurred in the processing of distance and speed. In order to achieve the decoupling of distance and speed, it is necessary to transmit several groups of PRF signals (staggered PRF) with periodic changes, and then process them separately, and then use the consistency algorithm or the Chinese remainder theorem to achieve the decoupling of the target's true distance and speed.

[0056] The three working modes are shown as follows: Figure 2 shown. Figure 2 The horizontal axis is speed, and the vertical axis is distance. Low PRF: no ambiguity in distance, but ambiguity in speed; medium PRF: both distance and speed are ambiguity; high PRF: ambiguity in distance, but no ambiguity in speed.

[0057] Pulse Doppler radar has the following technical defects in using the above three methods to measure distance and speed:

[0058] (1) Low PRF and high PRF cannot simultaneously measure distance and speed

[0059] Through the above description and Figure 2 From the diagram given, we can clearly see that: under low PRF, the measured target distance is not blurred, but the measured target speed is blurred; under high PRF, the measured target speed is not blurred, but the measured target distance is blurred.

[0060] (2) At medium and high PRF, side lobe cluster (SLC) seriously affects the decoupling of target distance.

[0061] Under medium and high PRF, as the target distance increases, the delay of the target echo relative to the transmitted signal also increases, and the number of ambiguous periods (PRF interval time) will increase accordingly. For general radars, the power of the target echo signal is inversely proportional to the fourth power of the distance, so the increase in the target distance leads to a rapid decrease in the power of the echo signal. For medium and high PRF, the PRF reaches above 20KHz. At this time, the SLC distributed along the time domain fills the entire PRF receiving interval. The real target echo and SLC overlap, greatly reducing the target's SNR, directly affecting the detection accuracy of the target distance. In severe cases, the target is submerged in the SLC, resulting in the inability to accurately detect the real target.

[0062] (3) The electromagnetic wave coverage time brought by the staggered PRF occupies a large proportion.

[0063] In the medium PRF working mode, in order to achieve the decoupling of the real distance and speed, the staggered PRF method is adopted. The specific method is: during the radar beam dwell time, staggered PRFs (group number is P) are emitted in sequence, and each PRF emits M, which is divided into two parts. The first part is L, which represents the number of pulses required for the electromagnetic wave to cover the working interval; the second part is S, which represents the number of pulses for data processing. The relationship between them and M is: M = L + S. In this way, L pulses are not processed and are wasted, because the time overhead required for electromagnetic waves to cover the space occupies the proportion of the entire working time:

[0064]

[0065] Where: P represents the number of groups of staggered PRF, L represents the number of pulses required for the electromagnetic wave to cover the farthest effective distance, and M represents the number of pulses in a group of PRF.

[0066] From the above formula, we can see that: as the number of groups and the effective distance of the staggered PRF increase, the overhead ratio of the electromagnetic wave coverage space will also increase, thereby reducing the working efficiency of the radar.

[0067] (4) There are blind spots in distance and speed measurement.

[0068] In pulse Doppler radar, if the target's echo signal and transmission signal overlap, then the target signal is blocked and a blind spot for ranging and speed measurement appears. Ranging and speed measurement blind spots are inherent phenomena of pulse Doppler radar, and can only be avoided by modifying the PRF period. In traditional pulse Doppler radar, once the system design is completed, the PRF is fixed and cannot be modified, so there will always be blind spots for ranging and speed measurement.

[0069] Although pulse Doppler radar technology uses the Doppler principle to achieve the distance measurement and speed measurement of the target, it is limited by the choice of PRF and cannot meet the needs of unambiguous distance measurement and speed measurement at the same time. The traditional solution is to adopt three fixed low, medium and high PRF working modes. However, this fixed configuration cannot adapt to all usage scenarios, resulting in blind spots for distance measurement and speed measurement, limiting the application effect of the radar. Especially in certain specific scenarios, such as when the target speed changes greatly or the distance is different, the limitation of this fixed PRF value is particularly obvious. In this regard, the embodiment of the present application provides a PRF generation method for a tracking and measuring radar, which can achieve accurate tracking and measurement of moving targets by adjusting the PRF working mode in stages and dynamically adjusting the antenna beam pointing, effectively solving the contradiction between distance measurement and speed measurement in the prior art, and improving the adaptability and application effect of the radar system.

[0070] See also Figure 3, a PRF generation method for a tracking and measuring radar includes: a search phase: controlling the radar to scan the entire working area in a first low PRF working mode to determine the moving target of interest. Tracking and measuring phase: in response to the determination of the moving target, executing a loop process until it is no longer necessary to track and measure the moving target, wherein the loop process includes: controlling the radar to transmit a first predetermined group of specified number of pulses in a second low PRF working mode to measure the distance and azimuth pitch angle of the moving target; controlling the radar to transmit a second predetermined group of specified number of pulses in a high PRF working mode to measure the radial speed of the moving target; and adjusting the radar antenna beam pointing according to the measured distance and azimuth pitch angle of the moving target to ensure that the moving target is illuminated.

[0071] It should be noted that during the search phase, the radar is controlled in the first low PRF working mode. The purpose of this phase is to scan the entire working area to determine the possible moving targets of interest. If the moving target of interest is determined, it switches to the tracking and measurement phase, otherwise it remains in the search phase. Due to the low PRF, the radar can cover a larger detection range while reducing the data processing burden caused by the high PRF. Through this phase of scanning, the radar can quickly lock onto the potential target position, providing a basis for the subsequent tracking and measurement phase.

[0072] In the search phase, the low PRF working mode enables the radar to cover a larger detection area in a short time, so as to quickly detect potential moving targets. And because of the low PRF, the number of echo signals received by the radar is relatively small, which reduces the burden on the data processing system and improves the system's response speed.

[0073] Next, in the tracking and measurement phase, the radar executes a loop process based on the target position determined in the search phase until it is no longer necessary to track and measure the target. The loop process includes three key steps: (1) Distance and angle measurement: In the second low PRF working mode, the radar transmits a first predetermined group of pulses with a specified number of pulses to measure the distance and azimuth and elevation angles of the moving target. This step provides accurate position information of the target, which helps with subsequent antenna beam adjustment. (2) Speed ​​measurement: In the high PRF working mode, the radar transmits a second predetermined group of pulses with a specified number of pulses to measure the radial speed of the moving target. The high PRF working mode can more accurately capture the target's motion information, thereby achieving accurate measurement of the target's speed. (3) Pointing adjustment: During the measurement process, the radar will also adjust the antenna beam pointing in real time based on the target's position information to ensure that the radar beam is always irradiated on the target. This step improves the stability and accuracy of target tracking.

[0074] During the tracking and measurement phase, the radar can accurately measure the moving target through ranging and angle measurement in low PRF mode and speed measurement in high PRF mode. This provides detailed position and motion information of the target, providing strong support for subsequent analysis and decision-making. And by adjusting the antenna beam pointing in real time to ensure that the radar beam is always irradiated on the target, this technical solution enhances the stability and reliability of target tracking. Even when the target moves quickly or the environment is complex, continuous tracking of the target can be maintained. In addition, the present application can flexibly respond to target tracking and measurement requirements in different scenarios by dynamically adjusting PRF and antenna beam pointing. This improves the adaptability and flexibility of the radar system, enabling it to be widely used in various complex environments.

[0075] In summary, the technical solution of the present application has at least the following advantages:

[0076] (1) There is no ambiguity in both distance and azimuth. In the search phase, the main purpose is to find out whether the target exists or not. Since the first low PRF working mode is adopted, there is no ambiguity in the distance. After entering the tracking measurement phase, a combination of the second low PRF working mode and the high PRF working mode is adopted. The second low PRF working mode is used to measure the distance and azimuth pitch angle of the moving target without ambiguity, and the high PRF working mode is used to measure the speed of the moving target. As a result, there are no blind spots in distance and speed in both stages.

[0077] (2) There is no blind spot in distance and speed. During the tracking and measurement phase, the PRF period of each cycle can be adjusted in real time according to the distance and speed of the target, ensuring that the echo signal of the moving target is located in the middle of the PRF period, neither overlapping with the current transmission pulse nor overlapping with the transmission signal of the next cycle, thus cleverly avoiding the ranging blind spot.

[0078] (3) Simple calculation of distance and speed. The target distance and speed obtained under medium PRF are fuzzy, and the real distance and speed need to be calculated by using a consistency algorithm or the Chinese remainder theorem. This process brings great difficulty. However, the present application uses a combination of the second low PRF working mode and the high PRF working mode to ensure that the distance or speed will not be blurred during the design, so the real distance and speed of the moving target can be easily calculated.

[0079] (4) High time utilization efficiency. In order to understand the real distance and speed under medium PRF, a staggered PRF is used. Under each set of PRF working conditions, more pulse signals need to be sent for electromagnetic waves to fill the working interval, and then the received signal can be processed. The more groups are used, the more the utilization efficiency of time resources and energy utilization will be reduced. In this application, the time resources required for electromagnetic waves to fill the working interval will appear only when the second low PRF working mode and the high PRF working mode are switched. Compared with the medium PRF, the efficiency is much improved.

[0080] (5) Not affected by antenna sidelobe clutter (SLC). Sidelobe clutter mainly affects the distance detection of moving targets. This application uses a low PRF to detect moving targets, and separates the SLC and the echo of the moving target in time. Therefore, the distance detection of the moving target by this application is not affected by SLC. Figure 4 As shown in Figure 1, it shows the influence of sidelobe clutter on moving target distance detection under medium or high PRF. Figure 4 As can be seen from the figure, the echo of the moving target has dropped below the SLC since the 6th PRF, resulting in the moving target being unable to be detected. Figure 5 As shown in the figure, the relationship between the sidelobe clutter and the moving target distance detection under low PRF is shown. Because under low PRF, it is ensured that the target echo at the farthest distance has returned to the receiver before the next PRF starts, so in the current PRF cycle, only the nearest SLC competes with the moving target echo, and the sidelobe clutter at the far end is almost negligible, so it has no effect on the detection of moving targets.

[0081] (6) The system is simple to implement. In the medium PRF mode, the echo of the moving target is affected by the sidelobe clutter in the time domain. In severe cases, the true distance of the moving target cannot be accurately calculated. For the pulse Doppler radar with medium PRF, the conventional approach to reduce the impact of sidelobe clutter and improve the improvement factor is to add an auxiliary antenna, namely a stealth antenna, when the system is implemented. The beam width of this antenna is more than 4 times the beam width of the main antenna, and the gain is equivalent to the gain of the first sidelobe of the main antenna. The main antenna transmits the signal, and the main antenna and the stealth antenna receive the signal at the same time. Then, in the time domain, the echo signal of the main antenna is subtracted from the echo signal received by the stealth antenna to suppress (not cancel) the sidelobe clutter, thereby improving the impact of sidelobe clutter on the detection of moving targets. The disadvantages of this method include: 1) the need to add a stealth channel; 2) the suppression effect is limited. However, the present application uses a low PRF to detect the distance of the moving target, and the moving target will be stronger than the sidelobe clutter (see Figure 5 ), the sidelobe clutter has basically no effect on the detection of moving targets, and the system does not require a blanking channel at all, thus simplifying the system design.

[0082] Based on the above solution, in some implementations of the present application, the constraint condition of the pulse repetition frequency PRF1 of the radar in the first low PRF working mode is: Where c is the speed of electromagnetic wave propagation; R max is the maximum distance of the moving target of interest; τ1 is the pulse width of the transmitted signal, and the constraints of τ1 include as well as d is the working ratio.

[0083] It should be noted that the above implementation further refines the pulse repetition frequency (PRF) constraints of the radar in the first low PRF working mode, as well as the related parameter constraints in the second low PRF working mode and the high PRF working mode. These constraints are intended to ensure that the radar system can efficiently and accurately complete the search and tracking measurement tasks in different working modes. Among them, It means that the actual working ratio of the radar must be less than the design working ratio of the designed transmitter; It means that the distance corresponding to the pulse width must be smaller than the radar's closest operating distance to prevent ranging blind spots.

[0084] Based on the aforementioned scheme, in some implementations of the present application, the radar is controlled to scan the entire working area in a low PRF working mode to determine the moving target of interest, including: controlling the radar to operate in a first low PRF working mode so that the radar antenna scans in predetermined azimuth and elevation directions to cover the entire working area; wherein, pulses are emitted and corresponding echo signals are processed while the beam is scanning to determine whether a moving target exists; and when a moving target exists, the distance of the moving target is calculated using the delay of the moving target relative to the radar, otherwise the scanning continues.

[0085] It should be noted that controlling the radar to operate in the first low PRF working mode can reduce the possibility of distance ambiguity and ensure that the radar has enough time to process the received echo signal to accurately measure the distance of the target. The radar antenna scans in a predetermined azimuth and elevation direction to ensure that the entire working area is fully covered. Exemplarily, the radar antenna can be gradually adjusted within a predetermined angle range to achieve effective detection of moving targets in different directions and heights. During the scanning process, the radar continuously transmits pulse signals and receives echo signals reflected from the moving target. These echo signals undergo a series of processing steps (such as amplification, filtering, demodulation, etc.) to extract information related to the target. Through the processed echo signal, the radar system can determine whether the moving target exists. If there is a moving target, the delay between the moving target and the radar is used to calculate the distance of the moving target. This calculation process is based on the propagation speed of electromagnetic waves (taking the speed of light) and the time difference between pulse emission and echo reception. Then, based on the calculated distance and the direction of the radar antenna, the position of the moving target of interest can be determined. If no target is detected during the current scanning cycle, the radar will continue to scan until the entire working area is scanned or a target is detected.

[0086] Based on the above scheme, in some implementations of the present application, the transmitting of pulses and processing of corresponding echo signals while beam scanning include: controlling the radar to transmit N1 pulses, and performing coherent accumulation on the received echo signals, and performing pulse compression processing, wherein the constraint condition of N1 is: Among them, v max is the maximum speed of the moving target; R bin is the range gate, and the size of the range gate is: c is the speed of electromagnetic wave propagation; f s is the sampling frequency of the range echo signal, f s ≥2B r , B r is the bandwidth of the transmitted signal.

[0087] It should be noted that coherent accumulation processing is to align and accumulate multiple pulse echo signals in time to enhance the strength of the target signal and improve the signal-to-noise ratio to improve the detection capability of moving targets. Pulse compression processing uses the prior knowledge of the transmitted signal to filter the received echo signal by designing a filter that matches the transmitted signal. After pulse compression processing, the radar system can obtain a higher distance resolution, thereby more accurately measuring the distance of the target. In the above implementation, by clarifying the constraints of N1, it can be ensured that the radar system can accurately measure the distance and speed of the target. The setting of these technical details and constraints not only improves the performance of the radar system, but also enhances its reliability and stability in practical applications.

[0088] Based on the above scheme, in some implementations of the present application, the constraint condition of the pulse repetition frequency PRF2 of the radar in the second low PRF working mode is: as well as Among them, c is the speed of electromagnetic wave propagation; R1 is the distance of the moving target, which is the target distance obtained in the search phase or the target distance obtained in the previous cycle of the tracking measurement phase; τ1 is the pulse width of the transmitted signal; k is the predetermined time expansion factor.

[0089] In the above implementation, the pulse repetition frequency PRF2 constraint of the radar in the second low PRF working mode is further determined to ensure that the radar system can effectively detect and track moving targets without generating range ambiguity. The predetermined time expansion factor can be set to 1.05.

[0090] Based on the foregoing solution, in some implementations of the present application, the controlling the radar to transmit a first predetermined group of specified number of pulses in the second low PRF operating mode includes: controlling the radar to transmit a first predetermined group of specified number of pulses in the second low PRF operating mode, and performing coherent accumulation and pulse compression processing on the received echo signals; wherein the constraint condition of the first predetermined group of specified number N2 is: Among them, v max is the maximum speed of the moving target; R bin is the range gate, and the size of the range gate is: c is the speed of electromagnetic wave propagation; f s is the sampling frequency of the range echo signal, f s ≥2B r , B r is the bandwidth of the transmitted signal.

[0091] Based on the above scheme, in some implementations of the present application, the constraint condition of the pulse repetition frequency PRF3 of the radar in the high PRF working mode is: Where: λ is the wavelength of the radar transmission signal; v1 is the radial velocity of the moving target relative to the radar, which is the highest velocity of the moving target or the detection velocity of the moving target obtained in the previous cycle of the tracking measurement phase.

[0092] In the above implementation, when the radar operates in a high PRF (pulse repetition frequency) working mode, the setting of its pulse repetition frequency is subject to specific constraints. These constraints are intended to ensure that the radar system can accurately measure the radial velocity of the moving target while avoiding distance ambiguity caused by excessively high pulse repetition frequencies. This constraint ensures that the radar system can accurately measure the radial velocity of the moving target, and the pulse repetition frequency needs to be high enough to capture the echo signal changes caused by the movement of the target between adjacent pulses. At the same time, this condition also avoids the distance ambiguity problem caused by excessively high pulse repetition frequencies, because when the pulse repetition frequency exceeds a certain threshold, the echoes from targets at different distances may overlap, causing the radar system to be unable to accurately distinguish them.

[0093] Based on the above scheme, in some implementations of the present application, the value of the pulse repetition frequency PRF3 includes: dividing the distance R1 of the moving target detected by the radar in the second low PRF working mode by the preset unambiguous distance width to obtain a floating point number, and determining the value of the pulse repetition frequency PRF3 according to the floating point number; wherein the unambiguous distance width is c is the speed of electromagnetic wave propagation, PRF0 satisfies the constraint condition A predetermined initial value. Let the integer part of the floating point number be n and the decimal part be s, then determine the value of the pulse repetition frequency PRF3 according to the floating point number, including: if n is less than 2 or the value range of s is [0.3, 0.7], then PRF3 = PRF0; if s is less than 0.3, then If s is greater than 0.7, then

[0094] It should be noted that, through the processing in the above implementation, the value of the pulse repetition frequency PRF3 can satisfy the unambiguous Doppler frequency of the moving target, and at the same time ensure that the echo of the moving target of interest does not have a distance blind spot. At the same time, the moving target of interest can always be located in the middle of a PRF3, and will not overlap with the transmission signal of the current PRF3, nor will it overlap with the next transmission signal, and there is a safety margin between the two.

[0095] Specifically, when adjusting the value of PRF3, if n is less than 2 or the value range of s is [0.3, 0.7], PRF3 is kept as PRF0; if s is less than 0.3, PRF3 needs to be increased to reduce the unambiguous distance width so that the target echo signal is closer to the current transmission signal but still has a safety margin. If s is greater than 0.7, PRF needs to be reduced to increase the unambiguous distance width so that the target echo signal maintains a safe distance from the transmission signal of the next cycle. Through such processing, it can be ensured that the echo signal of the moving target is located at 30%-70% of the current transmission signal, and there is enough safety margin between the transmission signal of the current and next cycles. This can not only meet the requirements of unambiguous Doppler frequency of moving targets, but also ensure that the echo of the target of interest does not have a distance blind spot.

[0096] Based on the above solution, in some implementations of the present application, the calculation formula for the number N2 of the second predetermined group of specified numbers is N2=N3+N4, where, c is the speed of electromagnetic wave propagation; R1 is the distance of the target of interest; τ2 is the pulse width of the transmitted signal in the high PRF working mode, d is the radar duty ratio; λ is the wavelength of the radar signal; v max is the maximum speed of the moving target; k is the predetermined time expansion factor; R bin is the range gate; d is the Doppler resolution, ρ v is the speed resolution.

[0097] In the above implementation, the calculation formula for the number N2 of the second predetermined group of specified numbers is determined, which can ensure that the electromagnetic wave can cover the target space and meet the requirements of Doppler resolution, thereby improving the accuracy of target detection and measurement. In addition, reasonable parameter settings enable the radar system to reduce unnecessary pulse transmission and signal processing overhead as much as possible while meeting the detection and measurement requirements, thereby optimizing the allocation of radar resources. Among them, by limiting the pulse width, it is ensured that the actual working ratio of the radar is less than the design working ratio of the transmitter, preventing the damage of the transmitter, and improving the reliability and stability of the radar system.

[0098] Based on the aforementioned scheme, in some implementations of the present application, the selection of the pulse repetition frequency of the radar in the second low PRF operating mode is dynamically adjusted according to the distance of the moving target, so that the distance measurement of the moving target is unambiguous; the selection of the pulse repetition frequency of the radar in the high PRF operating mode is dynamically adjusted according to the speed of the moving target and the wavelength of the radar transmission signal, so as to make the Doppler frequency measurement unambiguous and ensure that the echo signal of the moving target is within the safety margin between the current transmission signal and the next periodic transmission signal.

[0099] It should be noted that in the second low PRF working mode, the radar system dynamically adjusts the pulse repetition frequency according to the distance of the moving target. The purpose of this adjustment is to ensure that the distance measurement of the moving target is unambiguous, that is, to avoid the distance confusion caused by the pulse repetition frequency being too high. In the high PRF working mode, the radar system dynamically adjusts the pulse repetition frequency according to the speed of the moving target and the wavelength of the radar transmission signal. The purpose of this adjustment is to ensure that the Doppler frequency measurement is unambiguous, that is, to avoid the Doppler frequency confusion caused by the pulse repetition frequency being too low. At the same time, it is also necessary to ensure that the echo signal of the moving target is within the safety margin between the current transmission signal and the next cycle transmission signal to prevent signal overlap and interference.

[0100] In order to enable those skilled in the art to understand the present application more intuitively, a specific example will be used here to illustrate.

[0101] The system parameters used in this example are shown in the following table:

[0102] serial number parameter symbol Specific value 1 Maximum operating distance <![CDATA[R max ]]> 250km 2 Maximum speed <![CDATA[v max ]]> 2000m / s 3 Transmitted signal wavelength λ 0.03125m 4 Pulse width at low PRF <![CDATA[τ1]]> 30us 5 Pulse width at high PRF <![CDATA[τ2]]> 2us 6 Radar duty ratio d 30％ 7 Speed ​​resolution <![CDATA[ρ v ]]> 1m / s 8 Bandwidth of the transmitted signal <![CDATA[B r ]]> 3.75MHz 9 Minimum range <![CDATA[R min ]]> 5km

[0103] In this example, the radar is placed 5 km behind the target, using a single pulse to measure angles, and the active phased array antenna changes the beam direction. The curves of the distance and speed of the simulated target over time are shown in the figure below: Figure 6-Figure 7 As shown in the figure, we can see that the maximum target speed is 2000m / s and the maximum distance is 250km. After the radar is turned on, it will first perform a power-on self-test and then enter the search phase.

[0104] In the search phase, the first low PRF working mode is used. The pulse width τ1 of the transmitted signal is selected so that the target echo at the closest range does not produce a range blind zone, that is:

[0105]

[0106] Temporarily select τ1 as 30us, and the corresponding distance blind area is 4.5km, which is less than 5km and meets the requirements. In order to ensure that there is no distance ambiguity at the farthest effective distance, the selected PRF1 needs to meet the following requirements:

[0107]

[0108] The actual PRF1 selected is: 580Hz, at which the corresponding maximum distance of the moving target is 254km, which is greater than 250km and meets the requirement of no blur for the moving target at the farthest distance.

[0109] Verify that the actual work ratio is:

[0110] τ1×PRF1=1.74% (10)

[0111] It is less than 30%, so it will not cause damage to the transmitter.

[0112] The radar antenna scans the working range uniformly in azimuth and elevation. During the scanning process, it transmits pulse signals according to PRF1 of 580Hz, and then performs coherent accumulation processing on the received echo signals. The accumulation has two purposes: 1) improving SNR (Signal-to-Noise Ratio); 2) reducing the processing workload.

[0113] The transmitted signal is a linear frequency modulation signal with a bandwidth of 3.75 MHz and a corresponding sampling rate of f. s To satisfy the Nyquist sampling theorem, 4MSPS is selected, so a range gate is:

[0114]

[0115] The number N1 of echo signal accumulation needs to satisfy:

[0116]

[0117] According to the above formula, the number of pulse accumulation under low PRF is selected as 8. After accumulation, the number of echoes is reduced by 8 times, reducing the pressure of subsequent pulse compression; secondly, it also ensures that within 8 PRF accumulation cycles, the displacement of the fastest moving target will not exceed 1 range gate.

[0118] The SNR can be further improved by pulse compression of the accumulated signal:

[0119] B r ×τ1=112.5 (13)

[0120] Corresponding: 20dB.

[0121] Finally, the target is detected along the distance direction. If there is a moving target, the distance R1 of the moving target is obtained by calculating the delay. At the same time, the azimuth and elevation angle of the moving target relative to the radar are measured using single pulse angle measurement technology.

[0122] Once a moving target is detected, the radar enters the moving target tracking and measurement phase. Figure 1It can be seen that: when the wavelength is 0.03125m, the unambiguous speed and distance detection values ​​are: 2343.75m / s*km, while in this example, the product of speed and distance is: 500000m / s*km, which is much larger than the unambiguous detection value. Therefore, no matter what PRF is selected, it is impossible to simultaneously ensure that the distance and speed of the moving target are not ambiguous. For this reason, a combination of low PRF and high PRF is adopted in the tracking and measurement stage. When the PRF is low, in order to simplify the system implementation, the pulse width of the transmitted signal is still set to 30us. Since the moving target is in a very large range of 5km-250km relative to the radar distance, the choice of PRF at this time cannot be determined solely by the distance and pulse width, but also has to add a limiting factor: the working ratio. When the pulse width of the transmitted signal and the system design working ratio are determined, the maximum allowable PRF is:

[0123]

[0124] The above constraints are mainly to protect the transmitter. The highest RPF of the low PRF mode is set to 10000Hz, and the unambiguous distance corresponding to this PRF is:

[0125]

[0126] When the distance of the moving target is less than 10.05km, PRF2 is fixed to 10000Hz. When the distance of the moving target relative to the radar is greater than this value, the calculation formula of PRF2 is as follows:

[0127]

[0128] The number of echo coherent accumulations is consistent with the number of PRF selections in the search phase: N1=8.

[0129] After transmitting 8 pulse signals in low PRF mode (second low PRF working mode), the signal is then transmitted in high PRF mode (high PRF working mode). In order to ensure that the Doppler frequency of the moving target of interest is not aliased, consider the extreme case (the target speed is the highest speed), at this time, PRF3 is required to meet the following requirements:

[0130]

[0131] Set the highest PRF3 to 128000Hz, and calculate the pulse width τ2 of the transmitted signal based on this:

[0132]

[0133] The pulse width τ2 of the transmitted signal is set to 2us, and it remains fixed regardless of the moving speed. Assuming that the target speed measured in the previous cycle is v1, the initial PRF value PRF0 of the unambiguous moving target speed can be calculated as:

[0134]

[0135] Because the speed of the target is changing, the obtained PRF0 is also changing. In addition, the distance of the target relative to the radar is changing in real time, which may cause the echo signal to overlap with the transmitted signal. In order to avoid this situation, it is necessary to ensure that the target of interest is located in the middle of a PRF, neither overlapping with the transmitted signal of the current PRF nor with the next transmitted signal, and there is a safety margin between the two. Perform the following processing:

[0136] Determine a PRF3 initial value PRF0 that satisfies equation (19), and its corresponding period is Based on this, the unambiguous distance width is determined as:

[0137]

[0138] The distance R1 of the moving target detected by the radar in the second lowest PRF working mode is divided by the preset unambiguous distance width R mu , get a floating point number, let the integer part of the floating point number be n and the decimal part be s.

[0139] (1) If the value range of s is: [0.3:0.7], then the final PRF3 value is: PRF3 = PRF0;

[0140] (2) If s is less than 0.3, the final PRF3 value must satisfy:

[0141]

[0142] (3) If s is greater than 0.7, the final PRF3 value must satisfy:

[0143]

[0144] Through the above processing, it can be ensured that the echo signal of the moving target is located at 30%-70% of the current PRF3, and there is a sufficient safety margin between the current transmission signal and the transmission signal of the next cycle.

[0145] The number of pulses transmitted at high PRF is N2, which satisfies:

[0146] N2=N3+N4 (23)

[0147] Where: N3 represents the number of pulses required for the electromagnetic wave to cover the target space; N4 represents the number of pulses required to meet the Doppler resolution.

[0148] The number N3 of electromagnetic waves required to cover the target space must meet the following requirements:

[0149]

[0150] The number of PRFs N4 used to estimate the target speed needs to meet the following two conditions: 1) the displacement of the moving target within the duration of N4 PRF3 must be less than 1 range gate; 2) N4 must satisfy the Doppler resolution less than the Doppler resolution required by the system. According to the above parameters, the range gate is 37.5m; the Doppler resolution ρ d for:

[0151]

[0152] The value range of N4 is as follows:

[0153]

[0154] According to the above formula, the value of N4 is fixed to 2048.

[0155] The radar transmits N2 pulse signals in a high PRF mode, then skips receiving N3 echo signals, and continuously receives N4 (2048) echo signals. It then performs a 2048-point Fourier transform on the range cells with moving targets, and analyzes the Doppler frequency f of the moving targets in the frequency domain. d , and then use the following formula to calculate the speed of the moving target:

[0156]

[0157] This speed is used as the basis for generating PRF3 of the next high PRF cycle. When the speed detection is completed, the radar control system adjusts the radar beam pointing according to the azimuth and pitch angle of the target relative to the radar measured at low PRF, so that the beam is focused on the target, and then starts a new round of target tracking and measurement process.

[0158] Figure 8 The relationship between the low PRF and time during the tracking measurement phase is shown in FIG. Fig. 9 The graph shows the relationship between the high PRF and time during the tracking measurement phase. Figure 8When the distance between the target and the radar is relatively close at the beginning, the PRF2 is set to 10000Hz, so as to ensure that the actual working ratio of the radar is less than the designed working ratio and will not damage the transmitter; later, as the distance between the target and the radar becomes farther and farther, the corresponding PRF2 is also reduced to ensure that the distance measurement of the moving target is not ambiguous. Fig. 9 The reason why PRF3 changes linearly with time at the beginning is that the current target is very close to the radar. When the Doppler unambiguity is met, the ranging is also unambiguous, so the PRF3 at this time increases linearly. When PRF3 increases and the distance increases, the overall trend of PRF3 also increases with the increase in speed, and shows a sawtooth change. This change is a fine-tuning of PRF3 to ensure that the echo of the moving target of interest is located in the middle position of a PRF.

[0159] It will be apparent to those skilled in the art that the present application is not limited to the details of the exemplary embodiments described above, and that the present application can be implemented in other specific forms without departing from the spirit or essential features of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present application is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present application. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A PRF generation method for a tracking and measuring radar, characterized in that: include: Search phase: Control the radar to scan the entire working area in the first low PRF working mode to identify the moving target of interest; Tracking and measurement phase: In response to the determination of the moving target, a loop process is executed until it is no longer necessary to track and measure the moving target, wherein the loop process includes: controlling the radar to transmit a first predetermined group of specified number of pulses in a second low PRF operating mode to measure the distance and azimuth and elevation angles of the moving target; controlling the radar to transmit a second predetermined group of specified number of pulses in a high PRF operating mode to measure the radial movement speed of the moving target; and adjusting the radar antenna beam pointing direction according to the measured distance and azimuth and elevation angles of the moving target to ensure that the moving target is illuminated.

2. The method according to claim 1, characterized in that The pulse repetition frequency PRF1 constraint of the radar in the first low PRF working mode is: Where c is the speed of electromagnetic wave propagation; R max is the maximum distance of the moving target of interest; τ1 is the pulse width of the transmitted signal, and the constraints of τ1 include as well as d is the working ratio.

3. The method according to claim 1, characterized in that: The control radar scans the entire working area in the low PRF working mode to determine the moving targets of interest, including: The radar is controlled to operate in the first low PRF operating mode so that the radar antenna scans in predetermined azimuth and elevation directions to cover the entire working area; wherein, pulses are emitted and corresponding echo signals are processed while the beam is scanning to determine whether a moving target exists; and when a moving target exists, the distance of the moving target is calculated using the delay of the moving target relative to the radar, otherwise the scanning continues.

4. The method according to claim 3, characterized in that The transmitting of pulses and processing of corresponding echo signals while beam scanning includes: Control the radar to transmit N1 pulses, perform coherent accumulation on the received echo signals, and perform pulse compression processing. The constraint condition of N1 is: Among them, v max is the maximum speed of the moving target; R bin is the range gate, and the size of the range gate is: c is the speed of electromagnetic wave propagation; f s is the sampling frequency of the range echo signal, f s ≥2B r , B r is the bandwidth of the transmitted signal.

5. The method according to claim 1, characterized in that: The pulse repetition frequency PRF2 constraint of the radar in the second lowest PRF working mode is: as well as Among them, c is the speed of electromagnetic wave propagation; R1 is the distance of the moving target, which is the target distance obtained in the search phase or the target distance obtained in the previous cycle of the tracking measurement phase; τ1 is the pulse width of the transmitted signal; k is the predetermined time expansion factor.

6. The method according to claim 1, characterized in that The controlling radar to transmit a first predetermined group of specified number of pulses in the second low PRF working mode comprises: controlling the radar to transmit a first predetermined group of specified number of pulses in the second low PRF working mode, and performing coherent accumulation and pulse compression processing on the received echo signals; wherein the constraint condition of the first predetermined group of specified number N2 is: Among them, v max is the maximum speed of the moving target; R bin is the range gate, and the size of the range gate is: c is the speed of electromagnetic wave propagation; f s is the sampling frequency of the range echo signal, f s ≥2B r , B r is the bandwidth of the transmitted signal.

7. The method according to claim 1, characterized in that The pulse repetition frequency PRF3 constraint of the radar in high PRF working mode is: Where: λ is the wavelength of the radar transmission signal; v1 is the radial velocity of the moving target relative to the radar, which is the highest velocity of the moving target or the detection velocity of the moving target obtained in the previous cycle of the tracking measurement phase.

8. The method according to claim 7, characterized in that The value of the pulse repetition frequency PRF3 includes: The distance R1 of the moving target detected by the radar in the second low PRF working mode is divided by the preset unambiguous distance width to obtain a floating point number, and the value of the pulse repetition frequency PRF3 is determined according to the floating point number; wherein the unambiguous distance width is c is the speed of electromagnetic wave propagation, PRF0 satisfies the constraint condition a predetermined initial value of ; The integer part of the floating point number is n, and the decimal part is s. Then, the value of the pulse repetition frequency PRF3 is determined according to the floating point number, including: If n is less than 2 or the value range of s is [0.3, 0.7], then PRF3 = PRF0; if s is less than 0.3, then If s is greater than 0.7, then 9. The method according to claim 8, characterized in that The calculation formula of the number N2 of the second predetermined group of specified numbers is N2=N3+N4, where, c is the speed of electromagnetic wave propagation; R1 is the distance of the target of interest; τ2 is the pulse width of the transmitted signal in the high PRF working mode, d is the radar duty ratio; λ is the wavelength of the radar signal; v max is the maximum speed of the moving target; k is the predetermined time expansion factor; R bin is the range gate; d is the Doppler resolution, ρ v is the speed resolution.

10. The method according to claim 1, characterized in that The pulse repetition frequency of the radar in the second lowest PRF working mode is dynamically adjusted according to the distance of the moving target so that the distance measurement of the moving target is unambiguous; The pulse repetition frequency of the radar in the high PRF working mode is dynamically adjusted according to the speed of the moving target and the wavelength of the radar transmission signal to make the Doppler frequency measurement unambiguous and ensure that the echo signal of the moving target is within the safety margin between the current transmission signal and the next cycle transmission signal.

Images