CN108196250B - Continuous wave radar system and method for low-altitude small target detection - Google Patents

Abstract

The invention discloses a continuous wave radar system for low-altitude small target detection, wherein a transmitting module is used to generate a linear frequency modulation continuous wave and radiate it out; after the radiated linear frequency modulation continuous wave is reflected by the target, the echo reflected by the target is obtained The receiving module is used to receive the echo signal reflected by the target, obtain Z intermediate frequency signals, and send the Z intermediate frequency signals to the signal processing module; the signal processing module is used to receive the said receiving module. The Z intermediate frequency signals are used to obtain the real low-altitude small target traces, and the real low-altitude small target traces are sent to the terminal display module for display; the signal processing module is also used to obtain Z low-pass filtered digital signals and according to the real low-altitude small target traces Parameter estimation is performed to obtain the pitch and azimuth information of the real low-altitude small target, and then the pitch and azimuth information of the real low-altitude small target is sent to the terminal display module for display.

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 a method for detecting low-altitude small targets, which are suitable for detecting low-altitude slow-speed small targets in complex environments.

Background technique

The opening of low-altitude airspace has put forward new requirements for the target detection of ground military and civilian surveillance radars. At present, my country has no effective means of low-altitude target surveillance, which cannot meet the basic needs of low-altitude air traffic control, air defense and security. The rapid development and wide application of low-altitude, slow-speed and small-target technologies represented by UAVs has brought new challenges to national security. There is an urgent need for effective surveillance of low-altitude, slow-speed, small targets such as drones, such as security of key areas and regional no-fly.

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-speed small targets is even more difficult; although airborne early warning radar and ball-borne radar have the advantages of detecting low-altitude targets, However, the airborne early warning radar and the ball-borne radar have unfavorable factors such as complex system, difficult implementation, and high cost. The use of airborne early warning radar and ball-borne radar to detect low-altitude and slow-speed small targets is a bit of a loss. Therefore, in order to find a simple, cost-effective and low-altitude slow-speed small target detection method, people have considered the ground-based low-altitude radar with the ground early warning radar as the background. The beam of ground-based low-altitude radar should focus on low-altitude when the radar has a certain elevation, thus overcoming the beam occlusion problem in general ground-based early warning radars, so that the beam can effectively illuminate low-altitude targets. The radar should be small in size, light in weight, low in cost, and easy to erect. It is generally erected on the commanding heights of the ground, such as hills and the tops of tall buildings. When using ground-based low-altitude radar to detect low-altitude slow-speed small targets, the following problems are mainly faced:

(1) The radar scattering cross-section (RCS) of low-altitude slow-speed small targets is small, the signal echo is weak, the signal-to-noise ratio is low, and detection is difficult, so an effective weak signal detection method must be used.

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

(3) There are many interference targets: because the low-altitude slow-speed small target has a low flying height, the radar will inevitably detect ground moving targets (mainly ground moving vehicles) when it detects it.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the purpose of the present invention is to propose a continuous wave radar system and a method for detecting low-altitude small targets, so as to improve the detection capability of the radar system for low-slow small targets.

In order to achieve the above 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 is characterized in that it includes: a transmitting module, a receiving module, a signal processing module and a terminal display module; Enter the input end of the receiving module, 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;

The transmitting module is used to generate the chirp continuous wave and radiate it out; after the radiated chirp continuous wave is reflected, the echo signal reflected by the target is obtained; the receiving module is used for receiving the echo signal reflected by the target, and obtains Z IF signals, and send the Z IF signals to the signal processing module; the signal processing module is used to receive the Z IF signals sent by the receiving module, obtain real low-altitude small target traces, and convert the real low-altitude small target traces The small target dot trace is sent to the terminal display module for display;

The signal processing module is also used to perform A/D transformation, digital coherent detection, and low-pass filtering on the Z intermediate frequency signals, respectively, to obtain Z low-pass filtered digital signals. Filter the digital signal for parameter estimation, and then obtain the pitch and azimuth information of the real low-altitude small target, and then send the pitch 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 according to claim 1, the continuous wave radar system for low-altitude small target detection, It includes 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 select-1 switch; the receiving module includes a frequency synthesizer, 1: Z power dividers, N receiving antennas, Z b-to-1 switches, Z couplers and Z receivers; it is characterized in that the method comprises:

Step 1, the timing controller provides a timing signal to the frequency synthesizer at the mth time, and the frequency synthesizer generates a corresponding waveform according to the timing signal, and sends the waveform to the transmitter; The waveform transmits the chirp continuous wave, which is denoted as the mth transmission signal; the M transmission antennas select a transmission antenna through the M-to-1 switch, and connect the mth transmission signal to the transmission antenna, and the mth transmission antenna is used to connect the transmission antenna. M-channel transmit signals are radiated out; among them, M, b, Z are positive integers greater than 0 respectively;

Step 2, let the value of m take 1 to M respectively, and repeat step 1, and then obtain the first transmission signal to the M transmission signal respectively, which is recorded as the M transmission signal; wherein each transmission signal passes through after radiating out. The target is reflected, and the echo signal reflected by the target is obtained accordingly; the number of time sequence 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 by the 1:Z power divider, and the Z channel frequency signal components are obtained as Z test signals, which are respectively sent to the Z couplers. , the Z frequency signal components correspond to the Z couplers one-to-one; the N receiving antennas are divided into a row, and each row has Y receiving antennas. Select X receiving antennas respectively, and then obtain aX receiving antennas; wherein, X, Y, a, N are positive integers greater than 0, aX=Z, bX=Y;

The echo signals reflected by the target are respectively received by aX receiving antennas 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 obtains Z The received signals are then sent to the corresponding receivers; the Z receivers respectively perform down-conversion processing and intermediate frequency amplification processing after correspondingly receiving the received signals, and then obtain Z intermediate frequency signals; wherein, aY=N;

Step 4: After the signal processing module performs A/D transformation, digital coherent detection, and low-pass filtering processing on the Z intermediate frequency signals respectively, Z low-pass filtered digital signals are obtained, and then digital beamforming is performed on the Z low-pass filtered digital signals. , pulse compression and moving target detection to obtain moving target detection results;

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 result, obtain the real low-altitude small target trace, and finally send the real low-altitude small target trace to the terminal display module for display;

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

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

First, the present invention realizes 360° electronic scanning through multiple selection of one switch.

Second, the present invention adopts 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 excellent low-speed target detection performance.

Third, the cylindrical array vertical dimension a-row antenna can be used for altimetry.

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

Description of drawings

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

1 is a block diagram of a continuous wave radar system for low-altitude small target detection according to the present invention;

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

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

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

Figure 3c is a block diagram of the work flow of the launch module;

Fig. 4a is a receiving antenna horizontal beam pattern;

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

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

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

Fig. 6a is a horizontal dimension receiving simultaneous multi-beam pattern;

Fig. 6b is a multi-beam pattern of horizontal dimension transceiving and synthesizing at the same time;

Fig. 6c is a vertical dimension receiving simultaneous multi-beam pattern;

Fig. 6d is a pattern of simultaneous multi-beam pattern of vertical-dimension transmit-receive synthesis.

Detailed ways

Referring to FIG. 1, it is a block diagram of a continuous wave radar system for low-altitude small target detection according to 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 the chirp continuous wave outward, and after being reflected by the target, it enters the input end of the receiving module, 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 In the example, the low-slow and small targets are called low-altitude, slow-speed, and small flying targets.

The transmitting module is used to generate the chirp continuous wave and radiate it out; after the radiated chirp continuous wave is reflected by the target, the echo signal reflected by the target is obtained; the receiving module is used for receiving the echo signal reflected by the target, and obtains the echo signal reflected by the target. The Z intermediate frequency signals are sent to the signal processing module; the signal processing module is used to receive the Z intermediate frequency signals sent by the receiving module, obtain the real low-altitude small target traces, and convert the real low-altitude small target traces. The low-altitude small target trace is sent to the terminal display module for display.

The signal processing module is also used to perform A/D transformation, digital coherent detection, and low-pass filtering on the Z intermediate frequency signals, respectively, to obtain Z low-pass filtered digital signals. Filter the digital signal for parameter estimation, and then obtain the pitch and azimuth information of the real low-altitude small target, and then send the pitch 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-to-1 switch; the output terminal of the timing controller is connected to the input terminal of the frequency synthesizer, and the output terminal of the frequency synthesizer is connected to the input terminal of the transmitter. The output end of the transmitter is connected to the input end of the M-to-1 switch, and the output of the M-to-1 switch is connected to M transmitting antennas; with reference to FIG. 2 , it is a schematic diagram of the antenna composition of a continuous wave radar system used for low-altitude small target detection according to the present invention; wherein Each of the M transmitting antennas is a small horn, and the M horns are evenly placed on a ring with a diameter of d. The M transmitting antennas are all vertically polarized, and their horizontal beam patterns and vertical beam patterns are shown in Figure 3a and Figure 3b, respectively.

Referring to Fig. 3c, it is a block diagram of the work flow of the launch module, and the work flow of the launch module is:

1.1 The timing controller provides a timing signal to the frequency synthesizer at the mth time, and the frequency synthesizer generates a corresponding waveform according to the timing signal, and sends the waveform to the transmitter; the transmitter transmits the waveform according to the waveform sent by the frequency synthesizer. The linear frequency modulated continuous wave is denoted as the mth transmission signal; the M transmission antennas select a transmission antenna through the M-to-1 switch, and connect the mth transmission signal to the transmission antenna, and the mth transmission antenna is transmitted through the transmission antenna. The emission signal is radiated; wherein, M is a positive integer greater than 0.

1.2 Let the value of m take 1 to M respectively, repeat 1.1, and then obtain the first transmission signal to the M transmission signal respectively, which is recorded as the M transmission signal; after each transmission signal is radiated, it is reflected by the target, And correspondingly obtain the echo signal reflected by the target; since each transmission signal is a chirp continuous wave, the corresponding selected transmission antenna at each moment is different, that is, at each moment, another transmission antenna is automatically selected by the timing controller, Therefore, M transmit antennas are made to work once in a complete cycle; and in a complete cycle, M transmit signals are radiated, which can ensure that the M transmit signals cover the range of 360° in azimuth and 20° in elevation; among which the timing sequence The number of controller moments is equal to the number of transmitting antennas.

Receiving module: Referring to Figure 2, it is a schematic diagram of the antenna composition of a continuous wave radar system for low-altitude small target detection according to 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 and the N receiving antennas in the receiving module cannot be shared, so a baffle is added between the transmitting module and the receiving module. The purpose of the baffle is to ensure the isolation of transmission and reception; 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, with 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 it is placed on the baffle. Right 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 a dipole or other (easy to be placed on the side of the cylinder), that is to say, there are Y array elements encircling a ring in the horizontal direction to form a circular array, and then a same circular array is obtained, A identical circular arrays are arranged at unequal intervals to form a cylindrical array, whose horizontal beam pattern and vertical beam pattern are shown in Figure 4a and Figure 4b, respectively.

4c, a block diagram of the working flow of the receiving module, the receiving module includes a frequency synthesizer, a 1:Z power divider, N receiving antennas, Z b-to-1 switches, Z couplers and Z receivers, each coupler It includes a first input end and a second input end; the output end of the frequency synthesizer is connected to the input end of the 1:Z power divider, and the Z output ends of the 1:Z power divider are correspondingly connected to the Z first input ends of the Z couplers , the outputs of the Z couplers are correspondingly connected to the Z inputs of the Z receivers, the N receiving antennas are divided into a row, the Y receiving antennas in each row are respectively connected with the X b-to-1 switch inputs, and aX b select 1 switch output terminal corresponds to Z second input terminals connected to Z couplers, aX=Z, aY=N, bX=Y; Z couplers correspond to Z receivers one-to-one, the working flow of the receiving module Yes:

After the frequency synthesizer generates the required frequency signal, the required frequency signal is divided into Z channels by the 1:Z power divider, and the Z channel frequency signal components are obtained as Z test signals, which are respectively sent to the Z couplers, the Z channel The frequency signal components are in one-to-one correspondence with the Z couplers; the N receiving antennas are divided into a row, and each row has Y receiving antennas. X receiving antennas are generated, 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; the Z receivers respectively receive the received signals and perform down-conversion processing and intermediate frequency amplification respectively. processing, and then Z intermediate frequency signals are obtained, and the Z intermediate frequency signals are sent 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 ends, one of which is connected to the input end of the transmitter, and the other is connected to the input end of the transmitter. The output end is connected to the input end 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 the 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 block diagram of the working flow 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. , 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 the 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; CFAR), obtain the real low-altitude small target spot trace, and finally send the real low-altitude small target spot trace to the terminal display module for display; Characteristic learning, 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 to multiply the first constant false alarm detection threshold, get The new detection threshold is used to perform constant false alarm detection (CFAR) on the moving target detection results to ensure that the false alarm probability is constant.

For example, under the background of strong clutter, the moving target detection result will 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 that the false alarm probability is constant. At the same time, the signal processing module estimates the parameters of the Z low-pass filtered digital signals in combination with the real low-altitude small target information, that is, the parameters of the real low-altitude small target are estimated by using methods such as single-pulse angle measurement or beam scanning angle measurement, and then the real low-altitude small target is obtained. The pitch angle and azimuth angle information of the target are 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 "broadband and narrowband" system is that the receiving beam has a longer residence time in each wave position and has strong clutter suppression capability, which is also an important guarantee for the low-altitude target detection radar system to obtain strong clutter suppression capability.

The simultaneous multi-beam forming of the receiving antenna includes the simultaneous multi-beam forming of the horizontal-dimension antenna and the simultaneous multi-beam forming of the vertical-dimension antenna; at the same time, the arrangement of the a-row antennas in the vertical dimension is unequally spaced, which can be used for altimetry; 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 according to claim 1, the continuous wave radar system for low-altitude small target detection, It includes 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 select-1 switch; the receiving module includes a frequency synthesizer, 1: Z power dividers, N receiving antennas, Z b-to-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 time, and the frequency synthesizer generates a corresponding waveform according to the timing signal, and sends the waveform to the transmitter; The waveform transmits the chirp continuous wave, which is denoted as the mth transmission signal; the M transmission antennas select a transmission antenna through the M-to-1 switch, and connect the mth transmission signal to the transmission antenna, and the mth transmission antenna is used to connect the transmission antenna. The m channels of transmit signals are radiated; wherein, M, b, and Z are positive integers greater than 0, respectively.

Step 2, let the value of m take 1 to M respectively, and repeat step 1, and then obtain the first transmission signal to the M transmission signal respectively, which is recorded as the M transmission signal; wherein each transmission signal passes through after radiating out. The target is reflected, and the echo signal reflected by the target is obtained correspondingly; the number of time sequence 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 by the 1:Z power divider, and the Z channel frequency signal components are obtained as Z test signals, which are respectively sent to the Z couplers. , the Z frequency signal components correspond to the Z couplers one-to-one; the N receiving antennas are divided into a row, and each row has Y receiving antennas. Row selects X receiving antennas respectively, and then obtains aX receiving antennas; wherein X, Y, a, and N are positive integers greater than 0 respectively, bX=Y, aX=Z.

The echo signals reflected by the target are respectively received by aX receiving antennas 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 obtains Z The received signals are then sent to the corresponding receivers; the Z receivers respectively receive the received signals and perform down-conversion processing and intermediate frequency amplification processing respectively, thereby obtaining Z intermediate frequency signals; where 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 respectively, Z low-pass filtered digital signals are obtained; then the Z low-pass filtered digital signals are digitally beamformed , pulse compression and moving target detection, obtain the moving target detection result, use 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 moving target detection results, 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; Low-pass filtering the digital signal, learning the characteristics of the target, interference and environment, increasing or decreasing the second constant false alarm detection threshold K, obtaining the adjusted second constant false alarm detection threshold, and then using 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 moving target detection result to ensure a constant false alarm probability.

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

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

The arrangement of the radar system in the experiment is as follows: the transmitting antenna consists of 12 small horns, all the horns are placed on a ring by the transmitting antenna, the receiving antenna is cylindrical, there are 3 rows in total, 48 in each row, a total of 144 antennas, Through the 3-to-1 switch, 16 antennas are selected from the 48 antennas for simultaneous multi-beam forming.

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 λ. 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 dimension receiving antennas (16 antennas in total) are used to simulate simultaneous multi-beam forming in the horizontal dimension, and 7 beams are generated at the same time, and the coverage range is 168.75°-198.75°.

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

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

Next, 3 receiving antennas in the vertical dimension are used to simulate simultaneous multi-beam forming in the vertical dimension, and 4 beams are formed at the same time. The center directions of the 4 beams are 2°, 7°, 12° and 17° respectively, covering a range of 15°.

Experiment 3: Without considering the vertical beam pattern of the transmitting antenna, the simulation results are shown in Figure 6c; it can be seen from Figure 6c that the beam side lobe level is higher when the transmitting antenna pattern is not considered; in order to further reduce the beam side lobe power If it is flat, consider adding the vertical beam pattern of the transmitting antenna.

Experiment 4: The vertical beam pattern of the transmitting antenna is not considered, and the simulation result is shown in Figure 6d.

In conclusion, the simulation experiment verifies the correctness, effectiveness and reliability of the present invention.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention; in this way, if these modifications and variations of the present invention belong to the scope of the claims of the present invention and its equivalent technology, It is then intended that the present invention also includes such modifications and variations.

Claims (3)

1. A continuous wave radar system for low altitude small target detection, comprising: the system comprises 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 waves outwards, the linear frequency modulation continuous waves are reflected by a target and then enter the input end of the receiving module, the output end of the receiving module is connected with the input end of the signal processing module, and the output end of the signal processing module is connected with the input end of the terminal display module;

the transmitting module is used for generating linear frequency modulation continuous waves and radiating the linear frequency modulation continuous waves; reflecting the radiated linear frequency modulation continuous wave to obtain an echo signal reflected by a target; the receiving module is used for receiving echo signals reflected by a target, obtaining Z intermediate frequency signals and sending the Z intermediate frequency signals to the signal processing module; the signal processing module is used for receiving the Z intermediate frequency signals sent by the receiving module to obtain a real low-altitude small target point trace, and sending the real low-altitude small target point trace to the terminal display module for display;

the transmitting module comprises a transmitter, M transmitting antennas, a frequency synthesizer, a time schedule controller and an M-to-1 switch; the output end of the time schedule controller is connected with the input end of a frequency synthesizer, the output end of the frequency synthesizer is connected with the input end of a transmitter, the output end of the transmitter is connected with the input end of an M-to-1 switch, and the output end of the M-to-1 switch is connected with M transmitting antennas;

the working process of the transmitting module is as follows:

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 linear frequency modulation continuous waves according to the waveforms transmitted by the frequency synthesizer, and the linear frequency modulation continuous waves are recorded as mth path of transmission signals; the M transmitting antennas select one transmitting antenna through an M-to-1 switch, the mth path of transmitting signals are connected to the transmitting antenna, and the mth path of transmitting signals are radiated through the transmitting antenna; wherein M is a positive integer greater than 0;

1.2, taking the value of M from 1 to M respectively, and repeatedly executing 1.1 to obtain a 1 st path of emission signal to an M th path of emission signal respectively, and marking as the M paths of emission signals; wherein, each path of emission signal is reflected by the target after being radiated out, and correspondingly, an echo signal reflected by the target is obtained; the time number of the time sequence controller is equal to the number of the transmitting antennas;

the signal processing module is further used for respectively carrying out A/D conversion, digital coherent detection and low-pass filtering on the Z intermediate-frequency signals to obtain Z low-pass filtering digital signals, carrying out parameter estimation on the Z low-pass filtering digital signals according to a real low-altitude small target point trace to further obtain pitch angle and azimuth angle information of the real low-altitude small target, and then sending the pitch angle and azimuth angle information of the real low-altitude small target to the terminal display module for display; z is a positive integer greater than 0;

the frequency synthesizer included in the transmitting module and the frequency synthesizer included in the receiving module are the same frequency synthesizer, the frequency synthesizer comprises two output ends, one of the output ends is connected with the input end of the transmitter, and the other output end is connected with the input end of the 1: Z power divider.

2. The continuous wave radar system for low altitude small target detection as claimed in claim 1 wherein the receiving module comprises a frequency synthesizer, a 1: Z power divider, N receiving antennas, Z1-out-of-b switches, Z couplers and Z receivers, each coupler comprising a first input terminal and a second input terminal; the output end of the frequency synthesizer is connected with 1: the power divider comprises Z power divider input ends, Z output ends of a 1: Z power divider are correspondingly connected with Z first input ends of Z couplers, the output ends of the Z couplers are correspondingly connected with Z input ends of Z receivers, N receiving antennas are divided into a rows, Y receiving antennas of each row are respectively connected with X b-to-1 switch input ends, AX b-to-1 switch output ends are correspondingly connected with Z second input ends of the Z couplers, aX is Z, AY is N, bX is Y; the Z couplers correspond to the Z receivers one by one;

the work flow of the receiving module is as follows:

the frequency synthesizer generates a required frequency signal, the required frequency signal is divided into Z paths through the 1: Z power divider, Z path frequency signal components are obtained and then serve as Z test signals which are respectively and correspondingly sent to Z couplers, and the Z path frequency signal components correspond to the Z couplers one by one; n receiving antennas are divided into a rows, each row of Y receiving antennas is provided with X switches for selecting 1 from b, and each row of Y receiving antennas is provided with X receiving antennas, so that the aX receiving antennas are obtained; echo signals reflected by the target are respectively received by the aX receiving antennas and enter the couplers corresponding to the receiving antennas; each coupler respectively calibrates the test signal received by the coupler and the echo signal reflected by the target, and then sends the Z received signals to corresponding receivers; and the Z receivers respectively perform down-conversion processing and intermediate frequency amplification processing after correspondingly receiving the received signals, so as to obtain Z intermediate frequency signals, and send the Z intermediate frequency signals to the signal processing module.

3. A continuous wave radar method for low-altitude small target detection is applied to the continuous wave radar system for low-altitude small target detection, which is disclosed by claim 1 and comprises a transmitting module, a receiving module, a signal processing module and a display module, wherein the transmitting module comprises a transmitter, M transmitting antennas, a frequency synthesizer, a time schedule controller and an M1-out-of-frame switch; the receiving module comprises a frequency synthesizer, a 1: Z power divider, N receiving antennas, Z1-from-b switches, Z couplers and Z receivers; characterized in that the method comprises:

step 1, a time sequence controller provides a time sequence signal to a frequency synthesizer at the mth moment, and the frequency synthesizer generates a corresponding waveform according to the time sequence signal and sends the waveform to a transmitter; the transmitter transmits linear frequency modulation continuous waves according to the waveforms transmitted by the frequency synthesizer, and the linear frequency modulation continuous waves are recorded as mth path of transmission signals; the M transmitting antennas select one transmitting antenna through an M-to-1 switch, the mth path of transmitting signals are connected to the transmitting antenna, and the mth path of transmitting signals are radiated through the transmitting antenna; wherein M, b and Z are positive integers which are greater than 0 respectively;

step 2, taking the value of M from 1 to M respectively, and repeatedly executing the step 1 to obtain a 1 st path of emission signal to an Mth path of emission signal which are marked as M paths of emission signals respectively; wherein, each path of emission signal is reflected by the target after being radiated out, and correspondingly, an echo signal reflected by the target is obtained; the time number of the time sequence controller is equal to the number of the transmitting antennas and corresponds to the transmitting antennas one by one;

step 3, after the frequency synthesizer generates the required frequency signal, dividing the required frequency signal into Z paths through a 1: Z power divider, obtaining Z path frequency signal components which are used as Z test signals and respectively sent to Z couplers correspondingly, wherein the Z path frequency signal components correspond to the Z couplers one by one; n receiving antennas are divided into a rows, each row of Y receiving antennas is provided with X switches for selecting 1 from b, and each row of Y receiving antennas is provided with X receiving antennas, so that the aX receiving antennas are obtained; wherein X, Y, a and N are positive integers greater than 0, aX is equal to Z, and bX is equal to Y;

echo signals reflected by the target are respectively received by the aX receiving antennas and enter the couplers corresponding to the receiving antennas; each coupler respectively calibrates the test signal received by the coupler and the echo signal reflected by the target, and then sends the Z received signals to corresponding receivers; respectively carrying out down-conversion processing and intermediate frequency amplification processing on the received signals by the Z receivers to obtain Z intermediate frequency signals; wherein aY ═ N;

step 4, the signal processing module respectively performs A/D conversion, digital coherent detection and low-pass filtering on the Z intermediate frequency signals to obtain Z low-pass filtering digital signals, and then performs digital beam forming, pulse compression and moving target detection on the Z low-pass filtering digital signals to obtain a moving target detection result;

determining a constant false alarm detection threshold, performing constant false alarm detection on a moving target detection result by using the constant false alarm detection threshold to obtain a real low-altitude small target point trace, and finally sending the real low-altitude small target point trace to a terminal display module for display;

the signal processing module carries out parameter estimation on the Z low-pass filtering digital signals according to the trace of the real low-altitude small target point, so that pitch angle and azimuth angle information of the real low-altitude small target are obtained, and the pitch angle and azimuth angle information of the real low-altitude small target are sent to the terminal display module to be displayed.

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