CN108196250A - For the continuous-wave radar system and its method of low altitude small target detection - Google Patents

Abstract

The invention discloses a kind of continuous-wave radar system for low altitude small target detection, wherein transmitting module is used to generate linear frequency modulation continuous wave, and radiate；The linear frequency modulation continuous wave radiateing obtains the echo-signal of target reflection after target reflects；Receiving module is used to receive the echo-signal of target reflection, and obtains Z intermediate-freuqncy signal, and the Z intermediate-freuqncy signal is sent to signal processing module；Signal processing module obtains true low altitude small target point mark, true low altitude small target point mark is sent to terminal display module shows for receiving the Z intermediate-freuqncy signal that the receiving module sends over；Signal processing module is additionally operable to obtain Z low-pass filtering digital signal and carries out parameter Estimation according to true low altitude small target point mark, and then the pitch angle and azimuth information of true low altitude small target are obtained, the pitch angle of true low altitude small target and azimuth information then are sent to terminal display module shows.

Description

Continuous Wave Radar System and Method for Low Altitude Small Target Detection

technical field

The invention relates to the technical field of target detection, in particular to a continuous wave radar system and method for low-altitude small target detection, which is suitable for the detection of low-altitude slow-speed small targets in complex environments.

Background technique

The opening of low-altitude airspace has put forward new requirements for ground military and civilian surveillance radar target detection. At present, my country has no effective means for low-altitude target surveillance, which cannot meet the basic needs of low-altitude air traffic control, air defense and security, and urgently needs to be solved; The rapid development and wide application of low-altitude, slow-moving and small-target technology represented by drones has brought new challenges to national security. There is an urgent need for effective monitoring of low-altitude, slow-moving and small targets such as drones for security and regional flight bans.

The detection of low-altitude targets has always been one of the important problems faced by modern radar systems, and the detection of low-altitude, slow and small targets is even more difficult; although airborne early warning radars and ball-borne radars have the advantages of detecting low-altitude targets, However, airborne early warning radar and ball-borne radar have disadvantages such as complex system, difficult implementation, and high cost. Using airborne early warning radar and ball-borne radar to detect low-altitude and slow-moving small targets is not worth the gain. Therefore, in order to find a simple, economical and effective low-altitude and slow-speed small target detection method, people have considered the ground-based low-altitude radar with the ground early warning radar as the background. Ground-based low-altitude radars should focus on low-altitude beams when the radar has a certain height, thus overcoming the beam occlusion problem in general ground early warning radars, so that the beams can effectively illuminate low-altitude targets. The radar should be small in size, light in weight, low in cost, and easy to install. It is generally installed on commanding heights on the ground such as hilltops and tops of tall buildings. When using ground-based low-altitude radar to detect low-altitude and slow-moving small targets, the main problems are as follows:

(1) The radar cross section (RCS) of low-altitude and slow-moving small targets is small, the signal echo is weak, the signal-to-noise ratio is low, and detection is difficult. Effective weak signal detection methods must be used.

(2) The antenna beam points to the low altitude (or is in the working state of looking down), the ground clutter intensity is large, the range is wide, and the situation is complicated: there are major technical bottlenecks in the detection of low, small, and slow targets in the background of non-uniform clutter, and the radar reception The machine needs to have a large dynamic range, and the signal processing needs to have a strong clutter suppression ability.

(3) There are many interference targets: because the low-altitude, slow-speed and small targets fly at a low altitude, it is inevitable that the radar will detect ground moving targets (mainly ground moving vehicles) at the same time when detecting them.

Contents of the invention

Aiming at the deficiencies in the prior art, the object of the present invention is to propose a continuous wave radar system and method for detecting low-altitude small targets, which are used to improve the detection capability of the radar system for low-slow and small targets.

In order to achieve the above-mentioned technical purpose, the present invention adopts the following technical solutions to achieve.

Technical solution one:

A continuous wave radar system for low-altitude small target detection, characterized in that it includes: a transmitting module, a receiving module, a signal processing module and a terminal display module; the output end of the transmitting module radiates a linear frequency-modulated continuous wave outward, and after being reflected by the target Enter the input terminal of the receiving module, the output terminal of the receiving module is connected to the input terminal of the signal processing module, and the output terminal of the signal processing module is connected to the input terminal of the terminal display module;

The transmitting module is used to generate a chirp continuous wave and radiate it; the radiated chirp continuous wave is reflected to obtain an echo signal reflected by the target; the receiving module is used to receive the echo signal reflected by the target and obtain Z an intermediate frequency signal, sending the Z intermediate frequency signals to a signal processing module; the signal processing module is used to receive the Z intermediate frequency signals sent by the receiving module to obtain real low-altitude small target traces, and transmit the real low-altitude small target traces The small target dots are sent to the terminal display module for display;

The signal processing module is also used to perform A/D conversion, digital coherent detection, and low-pass filtering on the Z intermediate frequency signals to obtain Z low-pass filtered digital signals, and perform Z low-pass filtering according to the real low-altitude small target point trace. Filter the digital signal for parameter estimation, and then obtain the pitch angle and azimuth information of the real low-altitude small target, and then send the pitch angle and azimuth information of the real low-altitude small target to the terminal display module for display; Z is a positive integer greater than 0.

Technical solution two:

A continuous wave radar method for low-altitude small target detection, applied to the continuous wave radar system for low-altitude small target detection described in claim 1, the continuous wave radar system for low-altitude small target detection, Including a transmitting module, a receiving module, a signal processing module and a terminal display module, the transmitting module includes a transmitter, M transmitting antennas, a frequency synthesizer, a timing controller and an M selection 1 switch; the receiving module includes a frequency synthesizer, 1: Z power splitter, N receiving antennas, Z b selection 1 switches, Z couplers and Z receivers; it is characterized in that the method includes:

Step 1, the timing controller provides a timing signal to the frequency synthesizer at the mth moment, and the frequency synthesizer generates a corresponding waveform according to the timing signal, and sends the waveform to the transmitter; The waveform transmits linear frequency modulation continuous wave, which is recorded as the m-th path transmission signal; the M transmit antennas select a transmit antenna through the M selection 1 switch, and connect the m-th path transmit signal to the transmit antenna, and the m-th path transmit signal is connected to the transmit antenna through the transmit antenna. M channels of transmitting signals are radiated out; wherein, M, b, and Z are positive integers greater than 0;

Step 2, let the value of m take from 1 to M respectively, repeat step 1, and then obtain the first transmission signal to the Mth transmission signal respectively, which are recorded as M transmission signals; where each transmission signal passes through The target reflection, and correspondingly obtain the echo signal reflected by the target; the number of times of the timing controller and the number of transmitting antennas are equal and one-to-one correspondence;

Step 3: After the frequency synthesizer generates the required frequency signal, the required frequency signal is divided into Z channels through the 1:Z power divider, and the Z channel frequency signal components are obtained as Z test signals, which are respectively sent to Z couplers , the Z frequency signal components correspond to the Z couplers one by one; the N receiving antennas are divided into a row, and each row has Y receiving antennas. After the Y receiving antennas in each row pass through X b selection 1 switches, each The row selects X receiving antennas respectively, and then obtains aX receiving antennas; wherein, X, Y, a, N are respectively positive integers greater than 0, aX=Z, bX=Y;

The echo signals reflected by the target are received by aX receiving antennas respectively, and enter the couplers corresponding to the respective receiving antennas; each coupler calibrates the test signal received by itself and the echo signal reflected by the target, and then Z A received signal is sent to the corresponding receiver; Z receivers respectively perform down-conversion processing and intermediate frequency amplification processing after receiving the received signal, and then obtain Z intermediate frequency signals; wherein, aY=N;

Step 4: After the signal processing module performs A/D conversion, digital coherent detection, and low-pass filtering on the Z intermediate frequency signals, Z low-pass filtering digital signals are obtained, and then digital beamforming is performed on the Z low-pass filtering digital signals , Pulse compression and moving target detection to get the moving target detection result;

Determine the constant false alarm detection threshold, and use the constant false alarm detection threshold to perform constant false alarm detection on the moving target detection results to obtain the real low-altitude small target traces, and finally send the real low-altitude small target traces to the terminal display module for display;

The signal processing module estimates the parameters of Z low-pass filtered digital signals according to the real low-altitude small target traces, and then obtains the pitch angle and azimuth angle information of the real low-altitude small target, and sends the pitch angle and azimuth information of the real low-altitude small target to The terminal display module performs display.

Compared with the prior art, the present invention has the following advantages:

First, the present invention realizes 360° electronic scanning through a multi-choice switch.

Second, the present invention uses a wide beam to transmit signals, and completes simultaneous multi-beam reception through digital beam forming (DBF) processing, with long beam dwell time, good clutter suppression performance, and superior low-speed target detection performance.

Third, the cylindrical array vertical dimension a row antenna can be used for height measurement.

Fourth, the radar system adopts the linear frequency modulation continuous wave system, which has the advantages of low transmission power, simple structure, small size, light weight, high reliability and low cost.

Description of drawings

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is a kind of continuous wave radar system block diagram that is used for low-altitude small target detection of the present invention;

Fig. 2 is a kind of continuous wave radar system antenna composition schematic diagram for low-altitude small target detection of the present invention;

Figure 3a is the horizontal beam pattern of the transmitting antenna;

Figure 3b is a vertical beam pattern of the transmitting antenna;

Figure 3c is a block diagram of the workflow of the transmitting module;

Figure 4a is the horizontal beam pattern of the receiving antenna;

Figure 4b is a vertical beam pattern of the receiving antenna;

Figure 4c is a block diagram of the workflow of the receiving module;

Fig. 5 is a block diagram of the workflow of the signal processing module;

Figure 6a is a multi-beam pattern for simultaneous reception in the horizontal dimension;

Fig. 6b is a simultaneous multi-beam pattern for transceiving and synthesizing in the horizontal dimension;

Figure 6c is a multi-beam pattern for simultaneous reception in the vertical dimension;

Figure 6d is a simultaneous multi-beam pattern for transmitting and receiving in the vertical dimension.

Detailed ways

Referring to Fig. 1, it is a block diagram of a continuous wave radar system for low-altitude small target detection of the present invention; wherein the continuous wave radar system for low-altitude small target detection includes a transmitting module, a receiving module, a signal processing module and a terminal Display module; the output end of the transmitting module radiates linear frequency modulation continuous wave outwards, and enters the input end of the receiving module after being reflected by the target, the output end of the receiving module is connected to the input end of the signal processing module, and the output end of the signal processing module is connected to the input end of the terminal display module; this implementation The low-slow and small targets in the example are all called low-altitude, slow-speed, and small-scale flying targets. The flying altitude is generally below 1,000 meters, the speed is relatively slow, and the radar reflection area is small.

The transmitting module is used to generate a chirp continuous wave and radiate it out; the radiated chirp continuous wave is reflected by the target to obtain an echo signal reflected by the target; the receiving module is used to receive the echo signal reflected by the target and obtain Z intermediate frequency signals, sending the Z intermediate frequency signals to a signal processing module; the signal processing module is used to receive the Z intermediate frequency signals sent by the receiving module to obtain real low-altitude small target traces, and send the real The traces of small low-altitude targets are sent to the terminal display module for display.

The signal processing module is also used to perform A/D conversion, digital coherent detection, and low-pass filtering on the Z intermediate frequency signals to obtain Z low-pass filtered digital signals, and perform Z low-pass filtering according to the real low-altitude small target point trace. Filter the digital signal for parameter estimation, and then obtain the pitch angle and azimuth information of the real low-altitude small target, and then send the pitch angle and azimuth information of the real low-altitude small target to the terminal display module for display; Z is a positive integer greater than 0.

Transmitting module: the transmitting module includes a transmitter, M transmitting antennas, a frequency synthesizer, a timing controller and an M selection 1 switch; the output of the timing controller is connected to the input of the frequency synthesizer, and the output of the frequency synthesizer is connected to the input of the transmitter. Transmitter output end connects M and selects 1 switch input end, and M selects 1 switch output end and connects M transmit antennas; With reference to Fig. 2, it is a kind of continuous wave radar system antenna composition diagram for low-altitude small target detection of the present invention; Wherein Each of the M transmitting antennas is a small horn, and the M horns are evenly placed on a circular ring with a diameter of d. The M transmitting antennas are all vertically polarized, and their horizontal beam pattern and vertical beam patterns are shown in Figure 3a and Figure 3b, respectively.

Referring to Figure 3c, it is a block diagram of the workflow of the launch module, and the workflow of the launch module is:

1.1 The timing controller provides a timing signal to the frequency synthesizer at the mth moment, and the frequency synthesizer generates a corresponding waveform according to the timing signal, and sends the waveform to the transmitter; the transmitter transmits according to the waveform sent by the frequency synthesizer Linear frequency modulation continuous wave, denoted as the m-th path transmission signal; M transmission antennas select a transmission antenna through the M selection 1 switch, and connect the m-th path transmission signal to the transmission antenna, through which the m-th path The transmitting signal is radiated; wherein, M is a positive integer greater than 0.

1.2 Let the value of m take from 1 to M respectively, repeat 1.1, and then obtain the first to Mth transmission signals respectively, which are recorded as M transmission signals; where each transmission signal is reflected by the target after being radiated, And the echo signal reflected by the target is obtained accordingly; since each transmission signal is linear frequency modulation continuous wave, the corresponding transmission antennas selected at each time are different, that is, another transmission antenna is automatically selected by the timing controller at each time, Therefore, the M transmit antennas are all working once in a complete cycle; and in a complete cycle, the M transmit signals are radiated to ensure that the M transmit signals cover the range of 360° in azimuth and 20° in elevation; the timing The number of moments of the controller is equal to the number of transmitting antennas.

Receiving module: Referring to Fig. 2, it is a schematic diagram of the antenna composition of a continuous wave radar system for low-altitude small target detection of the present invention; wherein the continuous wave radar system for low-altitude small target detection is a continuous wave radar system, and the transmitting module The M transmitting antennas in the receiving module cannot be shared with the N receiving antennas in the receiving module, so a baffle is added between the transmitting module and the receiving module. The purpose of the baffle is to ensure the isolation of sending and receiving; the baffle is cylindrical and has a diameter of D , the height is D4, and it is placed directly below the transmitting module, and the distance between the top of the baffle and the M transmitting antennas is D3.

The N receiving antennas in the receiving module are cylindrical arrays, a total of a row, Y receiving antennas in each row, a total of a×Y=N receiving antennas, the diameter of the cylindrical array is d, the height is D2, and placed on the baffle Directly below, the distance between the N receiving antennas in the receiving module and the M transmitting antennas in the transmitting module is D1, the rows in row a are arranged at unequal intervals, and the N receiving antennas are all vertically polarized. The unit form is dipole or other (easily placed on the side of the cylinder), that is to say, there are Y array elements forming a ring in the horizontal direction to form a circular array, and then get a same circular array, a The same circular arrays are arranged at unequal intervals to form a cylindrical array, and its horizontal beam pattern and vertical beam pattern are shown in Figure 4a and Figure 4b respectively.

Referring to Fig. 4c, the block diagram of the working process of the receiving module, the receiving module includes a frequency synthesizer, a 1:Z power divider, N receiving antennas, Z b-selecting 1 switches, Z couplers and Z receivers, each coupler Including a first input terminal and a second input terminal; the output terminal of the frequency synthesizer is connected to the input terminal of the 1:Z power divider, and the Z output terminals of the 1:Z power divider are correspondingly connected to the Z first input terminals of the Z couplers , the output terminals of Z couplers are correspondingly connected to Z input terminals of Z receivers, N receiving antennas are divided into a row, and Y receiving antennas in each row are respectively connected to X b selection 1 switch input terminals, aX b Select 1 switch output port corresponding to Z second input ports connected to Z couplers, aX=Z, aY=N, bX=Y; Z couplers correspond to Z receivers one-to-one, the working process of the receiving module Yes:

After the frequency synthesizer generates the required frequency signal, the required frequency signal is divided into Z channels through the 1:Z power divider, and the Z channel frequency signal components are obtained as Z test signals, which are respectively sent to Z couplers. The frequency signal components correspond to the Z couplers one by one; the N receiving antennas are divided into a row, and each row has Y receiving antennas. X receiving antennas are produced, and then aX receiving antennas are obtained; the echo signals reflected by the target are respectively received by aX receiving antennas (aX=Z receiving antennas in total), and enter the couplers corresponding to the respective receiving antennas; each coupling The receiver calibrates the test signal received by itself and the echo signal reflected by the target, and then obtains Z received signals and sends them to the corresponding receivers; Z receivers respectively perform down-conversion processing and intermediate frequency amplification after receiving the received signals processing, and then obtain Z intermediate frequency signals, and send the Z intermediate frequency signals to the signal processing module.

Wherein, the frequency synthesizer included in the transmitting module and the frequency synthesizer included in the receiving module are the same frequency synthesizer, and the frequency synthesizer includes two output terminals, one of which is connected to the input terminal of the transmitter, and the other The output terminal is connected to the input terminal of the 1:Z power divider.

Signal processing module: Signal processing is one of the core parts of the radar (especially for this radar). The signal processing module mainly processes Z intermediate frequency signals and extracts useful information to complete target detection and information extraction. Processing; the radar signal processing module mainly includes A/D conversion, digital coherent detection, low-pass filtering, simultaneous multi-beam forming (DBF), pulse compression, moving target detection (MTD), constant false alarm detection (CFAR), target parameters estimate etc.

Referring to Figure 5, the working flow diagram of the signal processing module; the Z intermediate frequency signals output by the receiving module are directly sent to the signal processing module, and the signal processing module performs A/D conversion, digital coherent detection, and low-pass filtering on the Z intermediate frequency signals respectively. , to obtain Z low-pass filtered digital signals; then perform digital beamforming (DBF), pulse compression and moving target detection (MTD) on the Z low-pass filtered digital signals to obtain moving target detection results, and use unit average constant false alarm The detection method (CA-CFAR) obtains the first constant false alarm detection threshold U and the second constant false alarm detection threshold K, that is, the constant false alarm detection threshold is KU; use the detection threshold KU to perform constant false alarm detection ( CFAR) to obtain the real low-altitude small target traces, and finally send the real low-altitude small target traces to the terminal display module for display; combined with the target information detected by external equipment and Z low-pass filtered digital signals, the target, interference and environment Characteristic learning, increase or decrease the second constant false alarm detection threshold K to obtain the adjusted second constant false alarm detection threshold, and then use the adjusted second constant false alarm detection threshold to multiply the first constant false alarm detection threshold to obtain A new detection threshold is used, and the constant false alarm detection (CFAR) is performed on the moving target detection results with the new detection threshold to ensure that the false alarm probability is constant.

For example, in the background of strong clutter, the detection result of the moving target must contain clutter. At this time, the second constant false alarm detection threshold K can be appropriately increased by learning the characteristics of the target, interference and environment to ensure a constant false alarm probability. ; At the same time, the signal processing module combines the real low-altitude small target information to estimate the parameters of Z low-pass filtered digital signals, that is, use single pulse angle measurement or beam scanning angle measurement to estimate the parameters of the real low-altitude small target, and then obtain the real low-altitude small target. The pitch angle and azimuth angle information of the target is sent to the terminal display module for display.

Specifically, since the radar system is a digital beamforming system, in the signal processing process, multiple receiving beams will be formed at the same time when the receiving beam is formed by DBF, the purpose is to cover the radiation range of the transmitting beam, which is equivalent to The advantage of the "wide transmission and narrow reception" system is that the receiving beam has a longer dwell time at each wave position and strong clutter suppression capability, which is also an important guarantee for the low-altitude target detection radar system to obtain strong clutter suppression capability.

Among them, the simultaneous multi-beamforming of the receiving antenna includes the simultaneous multi-beamforming of the horizontal dimension antenna and the simultaneous multi-beamforming of the vertical dimension antenna; at the same time, the a row of antennas in the vertical dimension are arranged at unequal intervals, which can be used for height measurement; it should be pointed out that if In order to reduce the gain loss of edge beams, the number of corresponding simultaneous multi-beams can be increased through DBF processing, but this will also increase the amount of computation appropriately.

A continuous wave radar method for low-altitude small target detection, applied to the continuous wave radar system for low-altitude small target detection described in claim 1, the continuous wave radar system for low-altitude small target detection, Including a transmitting module, a receiving module, a signal processing module and a terminal display module, the transmitting module includes a transmitter, M transmitting antennas, a frequency synthesizer, a timing controller and an M selection 1 switch; the receiving module includes a frequency synthesizer, 1: Z power splitters, N receiving antennas, Z b-selection 1 switches, Z couplers and Z receivers; the method includes:

Step 1, the timing controller provides a timing signal to the frequency synthesizer at the mth moment, and the frequency synthesizer generates a corresponding waveform according to the timing signal, and sends the waveform to the transmitter; The waveform transmits linear frequency modulation continuous wave, which is recorded as the m-th path transmission signal; the M transmit antennas select a transmit antenna through the M selection 1 switch, and connect the m-th path transmit signal to the transmit antenna, and the m-th path transmit signal is connected to the transmit antenna through the transmit antenna. m channels of transmitting signals are radiated out; wherein, M, b, and Z are positive integers greater than 0, respectively.

Step 2, let the value of m take from 1 to M respectively, repeat step 1, and then obtain the first transmission signal to the Mth transmission signal respectively, which are recorded as M transmission signals; where each transmission signal passes through The target reflects, and correspondingly obtains the echo signal reflected by the target; the number of moments of the timing controller and the number of transmitting antennas are equal and correspond one-to-one.

Step 3: After the frequency synthesizer generates the required frequency signal, the required frequency signal is divided into Z channels through the 1:Z power divider, and the Z channel frequency signal components are obtained as Z test signals, which are respectively sent to Z couplers , the Z frequency signal components correspond to the Z couplers one by one; the N receiving antennas are divided into a row, and each row has Y receiving antennas. After the Y receiving antennas in each row pass through X b selection 1 switches, each Each row selects X receiving antennas to obtain aX receiving antennas; wherein, X, Y, a, and N are positive integers greater than 0, bX=Y, aX=Z.

The echo signals reflected by the target are received by aX receiving antennas respectively, and enter the couplers corresponding to the respective receiving antennas; each coupler calibrates the test signal received by itself and the echo signal reflected by the target, and then Z The received signals are sent to the corresponding receivers; Z receivers respectively perform down-conversion processing and intermediate frequency amplification processing after receiving the received signals, and then obtain Z intermediate frequency signals; wherein, aY=N.

Step 4: After the signal processing module performs A/D conversion, digital coherent detection, and low-pass filtering processing on the Z intermediate frequency signals, Z low-pass filtering digital signals are obtained; then digital beamforming is performed on the Z low-pass filtering digital signals , pulse compression and moving target detection, to obtain the moving target detection result, adopt the unit average constant false alarm detection method to obtain the first constant false alarm detection threshold U and the second constant false alarm detection threshold K, that is, the constant false alarm detection threshold is KU; Use the detection threshold KU to perform constant false alarm detection on the detection results of moving targets to obtain the real low-altitude small target traces, and finally send the real low-altitude small target traces to the terminal display module for display; combined with the target information detected by external devices and Z Low-pass filter the digital signal, learn the target, interference and environmental characteristics, increase or decrease the second constant false alarm detection threshold K, get the adjusted second constant false alarm detection threshold, and then use the adjusted second constant false alarm detection threshold The threshold is multiplied by the first constant false alarm detection threshold to obtain a new detection threshold, and the new detection threshold is used to perform constant false alarm detection (CFAR) on the detection results of moving objects to ensure a constant false alarm probability.

The signal processing module estimates the parameters of Z low-pass filtered digital signals according to the real low-altitude small target traces, and then obtains the pitch angle and azimuth angle information of the real low-altitude small target, and sends the pitch angle and azimuth information of the real low-altitude small target to The terminal display module performs display.

Effect of the present invention can be further verified by following simulation experiments:

The arrangement of the radar system in the experiment is as follows: the transmitting antenna is composed of 12 small horns, all the horns are placed on a circular ring by the transmitting antenna, and the receiving antenna is in the shape of a cylinder, a total of 3 rows, 48 in each row, a total of 144 antennas, Through a 3-to-1 switch, 16 antennas are selected from 48 antennas each time for simultaneous multi-beamforming.

In the experiment, the operating frequency of the radar system is X-band, the wavelength is λ, and the specific values of the other parameters will be represented by λ: d=10.7λ, D=15.3λ, D1=10λ, D2=6λ, D3=8.5λ, D4=0.7 lambda. The array element spacing in the horizontal dimension of the receiving antenna is 0.7λ, and the array element spacing in the vertical dimension is 2λ and 3λ.

Next, the 18th to 33rd horizontal receiving antennas (16 antennas in total) are used to simulate simultaneous multi-beamforming in the horizontal dimension, and 7 beams are generated at the same time, covering a range of 168.75°-198.75°.

Experiment 1: Regardless of the horizontal beam pattern of the transmitting antenna, the simulation results are shown in Figure 6a; it can be seen from Figure 6a that when the transmitting antenna pattern is not considered, the beam sidelobe level is higher, reaching -6.7dB. In order to further reduce the beam sidelobe level, consider adding the transmit antenna horizontal beam pattern.

Experiment 2: Consider the horizontal beam pattern of the transmitting antenna, and the simulation results are shown in Figure 6b.

Next, three receiving antennas in the vertical dimension are used to simulate simultaneous multi-beamforming in the vertical dimension, and 4 beams are formed at the same time. The center points of the 4 beams are 2°, 7°, 12° and 17° respectively, covering a range of 15°.

Experiment 3: Regardless of the vertical beam pattern of the transmitting antenna, the simulation results are shown in Figure 6c; it can be seen from Figure 6c that when the transmitting antenna pattern is not considered, the beam sidelobe level is high; in order to further reduce the beam sidelobe level Flat, you can consider adding the vertical beam pattern of the transmitting antenna.

Experiment 4: Regardless of the vertical beam pattern of the transmitting antenna, the simulation results are shown in Figure 6d.

In summary, the simulation experiment has verified the correctness, effectiveness and reliability of the present invention.

Obviously, those skilled in the art can carry out various modifications and variations to the present invention without departing from the spirit and scope of the present invention; Like this, if these modifications and variations of the present invention belong to the scope of the claims of the present invention and equivalent technologies thereof, It is intended that the present invention also encompasses such changes and modifications.

Claims (5)

1. A continuous wave radar system for low-altitude small target detection is characterized in that it comprises: a launch module, a receiver module, a signal processing module and a terminal display module; After reflection, it enters the input terminal of the receiving module, the output terminal of the receiving module is connected to the input terminal of the signal processing module, and the output terminal of the signal processing module is connected to the input terminal of the terminal display module; The transmitting module is used to generate a chirp continuous wave and radiate it; the radiated chirp continuous wave is reflected to obtain an echo signal reflected by the target; the receiving module is used to receive the echo signal reflected by the target and obtain Z an intermediate frequency signal, sending the Z intermediate frequency signals to a signal processing module; the signal processing module is used to receive the Z intermediate frequency signals sent by the receiving module to obtain real low-altitude small target traces, and transmit the real low-altitude small target traces The small target dots are sent to the terminal display module for display; The signal processing module is also used to perform A/D conversion, digital coherent detection, and low-pass filtering on the Z intermediate frequency signals to obtain Z low-pass filtered digital signals, and perform Z low-pass filtering according to the real low-altitude small target point trace. Filter the digital signal for parameter estimation, and then obtain the pitch angle and azimuth information of the real low-altitude small target, and then send the pitch angle and azimuth information of the real low-altitude small target to the terminal display module for display; Z is a positive integer greater than 0. 2. a kind of continuous wave radar system that is used for low-altitude small target detection as claimed in claim 1, is characterized in that, described transmitting module comprises transmitter, M transmitting antennas, frequency synthesizer, timing controller and M selecting 1 switch; where the output of the timing controller is connected to the input of the frequency synthesizer, the output of the frequency synthesizer is connected to the input of the transmitter, the output of the transmitter is connected to the input of the M selection 1 switch, and the output of the M selection 1 switch is connected to M transmitting antennas ; The launch module workflow is: 1.1 The timing controller provides a timing signal to the frequency synthesizer at the mth moment, and the frequency synthesizer generates a corresponding waveform according to the timing signal, and sends the waveform to the transmitter; the transmitter transmits according to the waveform sent by the frequency synthesizer Linear frequency modulation continuous wave, denoted as the m-th path transmission signal; M transmission antennas select a transmission antenna through the M selection 1 switch, and connect the m-th path transmission signal to the transmission antenna, through which the m-th path The transmitting signal is radiated; where, M is a positive integer greater than 0; 1.2 Let the value of m take from 1 to M respectively, repeat 1.1, and then obtain the first to Mth transmission signals respectively, which are recorded as M transmission signals; where each transmission signal is reflected by the target after being radiated, And the echo signal reflected by the target is obtained correspondingly; the number of moments of the timing controller is equal to the number of transmitting antennas. 3. a kind of continuous wave radar system for low-altitude small target detection as claimed in claim 1, is characterized in that, described receiving module comprises frequency synthesizer, 1:Z power splitter, N receiving antennas, Z b Select 1 switch, Z couplers and Z receivers, each coupler includes a first input terminal and a second input terminal; the output terminal of the frequency synthesizer is connected to the input terminal of the 1:Z power divider, and the 1:Z power divider The Z output terminals of Z couplers are correspondingly connected to Z first input terminals of Z couplers, the output terminals of Z couplers are correspondingly connected to Z input terminals of Z receivers, and the N receiving antennas are divided into a row, each row The Y receiving antennas are respectively connected to X b-selection 1 switch input terminals, and the aX b-selection 1 switch output terminals are correspondingly connected to Z second input terminals of Z couplers, aX=Z, aY=N, bX=Y ; Z couplers correspond to Z receivers one by one; The workflow of the receiving module is: The frequency synthesizer generates the required frequency signal, divides the required frequency signal into Z channels through the 1:Z power divider, and obtains the Z channel frequency signal components as Z test signals, which are respectively sent to Z couplers. The signal components correspond to Z couplers one by one; the N receiving antennas are divided into a row, and each row has Y receiving antennas. X receiving antennas, and then aX receiving antennas are obtained; the echo signals reflected by the target are respectively received by the aX receiving antennas, and enter into the couplers corresponding to the respective receiving antennas; The reflected echo signals are calibrated separately, and then Z received signals are obtained and sent to the corresponding receivers; Z receivers respectively perform down-conversion processing and intermediate frequency amplification processing after receiving the received signals, and then obtain Z intermediate frequency signals, and Send the Z intermediate frequency signals to a signal processing module. 4. A kind of continuous wave radar system that is used for low-altitude small target detection as claimed in claim 2 and 3, is characterized in that, the frequency synthesizer that described transmitting module comprises and the frequency synthesizer that described receiving module comprises are same A frequency synthesizer, the frequency synthesizer includes two output terminals, one of which is connected to the input terminal of the transmitter, and the other output terminal is connected to the input terminal of the 1:Z power divider. 5. A continuous wave radar method for low-altitude small target detection, applied to a kind of continuous wave radar system for low-altitude small target detection according to claim 1, the continuous wave radar for low-altitude small target detection The system includes a transmitting module, a receiving module, a signal processing module and a display module, the transmitting module includes a transmitter, M transmitting antennas, a frequency synthesizer, a timing controller and an M selection 1 switch; the receiving module includes a frequency synthesizer , 1: Z power splitter, N receiving antennas, Z b select 1 switches, Z couplers and Z receivers; it is characterized in that the method includes: Step 1, the timing controller provides a timing signal to the frequency synthesizer at the mth moment, and the frequency synthesizer generates a corresponding waveform according to the timing signal, and sends the waveform to the transmitter; The waveform transmits linear frequency modulation continuous wave, which is recorded as the m-th transmission signal; the M transmission antennas select a transmission antenna through the M selection 1 switch, and connect the m-th transmission signal to the transmission antenna. M channels of transmitting signals are radiated out; wherein, M, b, and Z are positive integers greater than 0; Step 2, let the value of m take from 1 to M respectively, repeat step 1, and then obtain the first transmission signal to the Mth transmission signal respectively, which are recorded as M transmission signals; where each transmission signal passes through The target reflection, and correspondingly obtain the echo signal reflected by the target; the number of times of the timing controller and the number of transmitting antennas are equal and one-to-one correspondence; Step 3: After the frequency synthesizer generates the required frequency signal, the required frequency signal is divided into Z channels through the 1:Z power divider, and the Z channel frequency signal components are obtained as Z test signals, which are respectively sent to Z couplers , the Z frequency signal components correspond to the Z couplers one by one; the N receiving antennas are divided into a row, and each row has Y receiving antennas. After the Y receiving antennas in each row pass through X b selection 1 switches, each The row selects X receiving antennas respectively, and then obtains aX receiving antennas; wherein, X, Y, a, N are respectively positive integers greater than 0, aX=Z, bX=Y; The echo signals reflected by the target are received by aX receiving antennas respectively, and enter the couplers corresponding to the respective receiving antennas; each coupler calibrates the test signal received by itself and the echo signal reflected by the target, and then Z A received signal is sent to the corresponding receiver; Z receivers respectively perform down-conversion processing and intermediate frequency amplification processing after receiving the received signal, and then obtain Z intermediate frequency signals; wherein, aY=N; Step 4: After the signal processing module performs A/D conversion, digital coherent detection, and low-pass filtering on the Z intermediate frequency signals, Z low-pass filtering digital signals are obtained, and then digital beamforming is performed on the Z low-pass filtering digital signals , Pulse compression and moving target detection to get the moving target detection result; Determine the constant false alarm detection threshold, and use the constant false alarm detection threshold to perform constant false alarm detection on the moving target detection results to obtain the real low-altitude small target traces, and finally send the real low-altitude small target traces to the terminal display module for display; The signal processing module estimates the parameters of Z low-pass filtered digital signals according to the real low-altitude small target traces, and then obtains the pitch angle and azimuth angle information of the real low-altitude small target, and sends the pitch angle and azimuth information of the real low-altitude small target to The terminal display module performs display.