Design Method of Low-Altitude Anti-jamming Transceiver Integrated Adaptive Radar System

Abstract

To address the inability of existing low-altitude radars to effectively suppress the effects of ground clutter and sea clutter, this invention presents a design method for an integrated low-altitude anti-jamming transceiver adaptive radar system. This method outlines the structure and function of the new system, and provides a method for transmitting multiple orthogonal signals with control delays for target detection, as well as a secondary software mixing method. Based on the signal processing results after software mixing, the range, velocity, and acceleration of the detected target and interference are obtained. Using this information, the interference from ground clutter and sea clutter is significantly suppressed, improving the system's speed and reliability.

Description

Technical Field

[0001] This invention relates to methods for monitoring low-altitude airspace and sea areas, and particularly to a design method for an integrated adaptive radar system with anti-jamming transceiver, belonging to the fields of safety and air traffic management. Background Technology

[0002] In the field of airport operational safety, birds and non-cooperative drone targets pose a significant threat to flight safety and cause substantial economic losses. Regarding bird strikes, takeoff and landing are the most vulnerable times. Over 90% of bird strikes occur at or near airports, 50% occur below 30 meters, and only 1% occur above 760 meters. Due to the high speed of aircraft, collisions with birds often cause severe damage, sometimes resulting in crashes. Currently, bird strikes are a major threat to aviation safety, and accurate detection, continuous tracking, and effective identification of low-speed, small targets are key tasks of reconnaissance and surveillance. Radar systems, as the primary detection equipment, face two main technical challenges:

[0003] (1) Current radar technology requires the echo of the first transmitted signal to arrive before the second transmission can be carried out. The time period for calculating the speed is relatively large (especially for distant targets), which causes a large error. According to the calculation of commonly used low-altitude radar at home and abroad, with a scanning speed of 24 revolutions per minute, the time interval for calculating the speed is 2.5 seconds. Within 2.5 seconds, the repeatability accuracy of the gimbal, the detection environment of the two beam angles, and the accuracy of the two target azimuths must be the same or very close. The speed calculation error will be very large. Therefore, it is difficult to effectively suppress sea clutter and ground clutter by transmitting signals in the same azimuth multiple times.

[0004] (2) Radar has a beam angle, and it is difficult to determine the specific location of the same target by transmitting and receiving signals at adjacent locations; therefore, it is difficult to effectively suppress sea clutter and ground clutter by processing signals transmitted and received at adjacent locations.

[0005] Therefore, existing low-altitude radar systems face the following challenges in practical applications:

[0006] (1) The detection of low-altitude targets by radar has a large detection blind zone and a large detection error. Under the coupling of factors such as land and sea clutter, terrain and object obstruction and multipath, the detection and identification of targets are difficult.

[0007] (2) Existing continuous wave low-altitude radars use a fixed transmission frequency, which makes it difficult to meet the different detection requirements of sea surface targets and air targets. Their transmission and reception system is difficult to adapt to the requirements of rapid target detection and tracking.

[0008] (3) In low-altitude target radar detection, the ground and sea clutter is dense and the model parameters change dynamically. The target echo is often buried in the high-intensity, high-density background clutter, making it difficult to detect the target quickly and reliably. Summary of the Invention

[0009] To address the inability of existing low-altitude radars to effectively suppress the effects of ground clutter and sea clutter, this invention presents a design method for an integrated low-altitude anti-jamming transceiver adaptive radar system. This method outlines the structure and function of the new system, and provides a method for transmitting multiple orthogonal signals with control delays for target detection, as well as a secondary software mixing method. Based on the signal processing results after software mixing, the range, velocity, and acceleration of the detected target and interference are obtained. Using this information, the interference from ground clutter and sea clutter is significantly suppressed, improving the system's speed and reliability.

[0010] The technical solution adopted by this invention to solve its technical problem is: a design method for a low-altitude anti-jamming integrated adaptive radar system, characterized by the following steps:

[0011] Step 1: The receiving section of the low-altitude anti-jamming integrated adaptive radar system receives signals through an antenna, extracts the carrier frequency signal through a high-frequency filter, then extracts the baseband signal through a baseband signal extractor (with or without mixing), and finally extracts the baseband signal through a baseband signal filter. The signal obtained by the A / D converter is sent to the central processing unit for secondary software mixing and subsequent signal processing. The transmitting section of the low-altitude anti-jamming integrated adaptive radar system uses a central processing unit to control the carrier frequency and mix batch orthogonal signals, which are then amplified by the radio frequency transmitting section and transmitted by the transmitting antenna.

[0012] Step 2: The central processing unit controls...

[0013]

[0014] Generate batch of orthogonal signals at all times The baseband signal is generated by mixing and the radio frequency section is controlled to generate a given carrier signal to transmit the baseband signal.

[0015] in , , It is a positive integer. The interval between the occurrence of two orthogonal signals. The transmission interval for two batches of orthogonal signals. To detect the fundamental frequency of the signal;

[0016] Step 3: The secondary software mixing section performs base frequency (ω) software mixing on the signal acquired by the A / D converter by module 1 inside the central processing unit, and performs 2-fold frequency (2ω) software mixing on module 2 inside the central processing unit. The signal is frequency-multiplied by N and mixed by Nω software using module N inside the central processing unit, and then acquired using common radar signal processing methods. target distance at any time , ;

[0017] Step 4: Calculate according to the following method

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] in, The distance between the detected target and the interference. The speed of the detected target and the interference. The acceleration of the detected target and the interference. and , The function is used to calculate the velocity of the target and the interference. Calculate the acceleration function for the target and the disturbance. For target and interference The function for calculating the second derivative;

[0024] Step 5: Based on the obtained target and interference , , , , To identify targets or interference: the velocity and acceleration of ground clutter generated by terrain features are close to zero, making them easy to eliminate; the velocity of ocean clutter generated by ocean waves is also significantly different from the velocity of moving targets at sea, making them easy to eliminate as well.

[0025] The beneficial results of this invention are: a method for controlling the delay of multiple orthogonal signals to transmit together for target detection has been invented. The orthogonal principle has solved the technical bottlenecks of "send first, arrive later" and "send later, arrive first". Multiple orthogonal signals can be transmitted at one time according to a controllable time interval. The transmission can calculate information such as target distance, speed and acceleration. By using speed and acceleration information, the interference of ground clutter and sea clutter is greatly suppressed, and the speed and reliability of the system are improved.

[0026] The specific content of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0027] Appendix Figure 1 Low-altitude anti-jamming integrated adaptive radar system;

[0028] Appendix Figure 2 Software mixing scheme for low-altitude anti-jamming integrated adaptive radar system. Detailed Implementation

[0029] See attached document Figure 1 and attached Figure 2 .

[0030] Step 1: The receiving section of the low-altitude anti-jamming integrated adaptive radar system receives signals through an antenna, extracts the carrier frequency signal through a high-frequency filter, then extracts the baseband signal through a baseband signal extractor (with or without mixing), and finally extracts the baseband signal through a baseband signal filter. The signal obtained by the A / D converter is sent to the FPGA central processing unit for secondary software mixing and signal processing after software mixing. The transmitting section of the low-altitude anti-jamming integrated adaptive radar system uses the FPGA central processing unit to control the carrier frequency and mix batch orthogonal signals, which are then amplified by the radio frequency transmitting section and transmitted by the transmitting antenna.

[0031] Step 2: FPGA central processing unit controls...

[0032]

[0033] Generate batch of orthogonal signals at all times The baseband signal is generated by mixing and the radio frequency section is controlled to generate a given carrier signal to transmit the baseband signal.

[0034] in , , The interval between the occurrence of two orthogonal signals. The transmission interval for two batches of orthogonal signals. To detect the fundamental frequency of the signal;

[0035] Step 3: The secondary software mixing section mixes the signals acquired by the A / D converter using the following methods: FPGA internal module 1 performs base frequency (ω) software mixing; FPGA internal module 2 performs 2x (2ω) software mixing; FPGA internal module 3 performs 3x (3ω) software mixing; and FPGA internal module 4 performs 4x (4ω) software mixing. The signal is frequency-multiplied by 5 and mixed at 5 ω using software by module 5 inside the FPGA, and then obtained using common radar signal processing methods. target distance at any time , ;

[0036] Step 4: Calculate according to the following method

[0037]

[0038]

[0039]

[0040] in, The distance between the detected target and the interference. The speed of the detected target and the interference. The acceleration of the detected target and the interference. and , The function is used to calculate the velocity of the target and the interference. Calculate the acceleration function for the target and the disturbance;

[0041] Step 5: Based on the obtained target and interference , , To identify targets or interference: the velocity and acceleration of ground clutter generated by terrain features are close to zero, making them easy to eliminate; the velocity of ocean clutter generated by ocean waves is also significantly different from the velocity of moving targets at sea, making them easy to eliminate as well.

Claims

1. A design method for a low-altitude anti-jamming integrated adaptive radar system, characterized by the following steps: Step 1: The receiving section of the low-altitude anti-jamming integrated adaptive radar system receives signals through an antenna, extracts the carrier frequency signal through a high-frequency filter, then extracts the baseband signal through a baseband signal extractor (with or without mixing), and finally extracts the baseband signal through a baseband signal filter. The signal obtained by the A / D converter is sent to the central processing unit for secondary software mixing and subsequent signal processing. The transmitting section of the low-altitude anti-jamming integrated adaptive radar system uses a central processing unit to control the carrier frequency and mix batch orthogonal signals, which are then amplified by the radio frequency transmitting section and transmitted by the transmitting antenna. Step 2: The central processing unit controls... Batch orthogonal signals are generated on the fly and mixed to form baseband signals, and the radio frequency part of the transmission is controlled to generate a given carrier signal transmission baseband signal; wherein , , is a positive integer, is the occurrence interval of two orthogonal signals, is the transmission interval of two batch orthogonal signals, is the basic frequency of the probe signal; Step three, the secondary software mixing part mixes the signal collected by A / D with base frequency ω by internal module 1 of the central processor, mixes the signal with 2ω by internal module 2 of the central processor, , mixes the signal with Nω by internal module N of the central processor, and then obtains the target distance at the moment by using the common radar signal processing method ;​​ Step 4: Calculate according to the following method , , , , ,in, the range of the detected target and the jammer, the velocity of the detected target and the jammer, the acceleration of the detected target and the jammer, and , a function for calculating the velocity of the target and the jammer, a function for calculating the acceleration of the target and the jammer, a function for calculating the derivative of the target and the jammer; Step 5: Based on the obtained target and interference , , , , To identify targets or interference: the velocity and acceleration of ground clutter generated by terrain features are close to zero, making them easy to eliminate; the velocity of ocean clutter generated by ocean waves is also significantly different from the velocity of moving targets at sea, making them easy to eliminate as well.

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