CN108196250B - Continuous wave radar system and method for low-altitude small target detection - Google Patents
Continuous wave radar system and method for low-altitude small target detection Download PDFInfo
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- CN108196250B CN108196250B CN201810077837.4A CN201810077837A CN108196250B CN 108196250 B CN108196250 B CN 108196250B CN 201810077837 A CN201810077837 A CN 201810077837A CN 108196250 B CN108196250 B CN 108196250B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/282—Transmitters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/28—Details of pulse systems
- G01S7/285—Receivers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
- G01S7/41—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00 using analysis of echo signal for target characterisation; Target signature; Target cross-section
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Abstract
The invention discloses a continuous wave radar system for detecting a low-altitude small target, wherein a transmitting module is used for generating linear frequency modulation continuous waves and radiating the linear frequency modulation continuous waves; after the radiated linear frequency modulation continuous wave is reflected by a target, an echo signal reflected by the target is obtained; 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 signal processing module is further used for obtaining Z low-pass filtering digital signals and carrying out parameter estimation according to the trace of the real low-altitude small target point, further obtaining 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.
Description
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 small targets in a complex environment.
Background
The low-altitude airspace open provides new requirements for ground military and civil surveillance radar target detection, and China has no effective means in the aspect of low-altitude target surveillance at present, can not meet the basic requirements of low-altitude air traffic control, air defense and security protection, and needs to solve urgently; the rapid development and wide application of low-altitude slow-speed small-target technology represented by an unmanned aerial vehicle bring new challenges to national security, and the low-altitude slow-speed small targets such as the unmanned aerial vehicle and the like need to be effectively monitored urgently for local security, regional flight prohibition and the like.
The detection of low-altitude targets is one of the important problems faced by modern radar systems, and the detection of low-altitude slow small targets is more difficult; although the airborne early warning radar and the ball-mounted radar have the advantages of detecting low-altitude targets, the airborne early warning radar and the ball-mounted radar have adverse factors of complex systems, difficulty in implementation, high cost and the like, and the low-altitude slow-speed small target detection is achieved by the airborne early warning radar and the ball-mounted radar to be slightly irrevocable. Therefore, in order to find a simple, economic and effective low-altitude slow-speed small target detection method, people consider a foundation low-altitude radar with a ground early warning radar as a background. The wave beam of the foundation low-altitude radar is mainly pointed to the low altitude under the condition that the radar is elevated to a certain degree, so that the problem of wave beam shielding in the common ground early warning radar is solved, and the wave beam can effectively irradiate a low-altitude target. The radar is small in size, light in weight, low in cost and convenient to erect, and is generally erected at ground elevation points such as mountains, the tops of high buildings and the like. When a ground-based low-altitude radar is used for detecting low-altitude slow-speed small targets, the following problems are mainly faced:
(1) the radar scattering cross section (RCS) of the low-altitude slow-speed small target is small, the signal echo is weak, the signal-to-noise ratio is low, the detection is difficult, and an effective weak signal detection method must be adopted.
(2) The antenna beam points to low altitude (or is in a overlooking working state), the ground clutter intensity is large, the range is wide, and the situation is complex: the detection of low, small and slow targets under the non-uniform clutter background has a major technical bottleneck, a radar receiver needs a large dynamic range, and signal processing needs strong clutter suppression capability.
(3) The interference targets are more: because of the low flying height of the low-altitude slow-speed small target, the radar inevitably detects the ground moving target (mainly a ground moving vehicle) at the same time when detecting the low flying height.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a continuous wave radar system for detecting low-altitude small targets and a method thereof, which are used for improving the detection capability of the radar system for the low-altitude small targets.
In order to achieve the technical purpose, the invention is realized by adopting the following technical scheme.
The first technical scheme is as follows:
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 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 second technical scheme is as follows:
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 terminal display module, wherein the transmitting module comprises a transmitter, M transmitting antennas, a frequency synthesizer, a time schedule controller and an M-to-1 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:
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;
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.
Compared with the prior art, the invention has the following advantages:
first, the present invention implements 360 ° electronic scanning by a one-out-of-many switch.
Secondly, the invention adopts wide wave beam emission signals and completes simultaneous multi-beam reception through Digital Beam Forming (DBF) processing, and has long wave beam residence time, good clutter suppression performance and excellent low-speed target detection performance.
Third, a cylindrical array vertical dimension a row antenna can be used for height measurement.
Fourthly, the radar system adopts a linear frequency modulation continuous wave system and has the advantages of low transmitting power, simple structure, small volume, light weight, high reliability and low cost.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
FIG. 1 is a block diagram of a continuous wave radar system for low altitude small target detection in accordance with the present invention;
FIG. 2 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;
fig. 3a is a transmit antenna horizontal beam pattern;
fig. 3b is a transmit antenna vertical beam pattern;
FIG. 3c is a block diagram of the transmitter module workflow;
fig. 4a is a receiving antenna horizontal beam pattern;
fig. 4b is a receive antenna vertical beam pattern;
FIG. 4c is a block diagram of the receive module workflow;
FIG. 5 is a block diagram of a signal processing module workflow;
figure 6a is a horizontal dimension receive simultaneous multi-beam pattern;
figure 6b is a horizontal dimension transceive composite simultaneous multibeam pattern;
figure 6c is a vertical dimension receive simultaneous multi-beam pattern;
figure 6d is a vertical dimension transceive-synthesis simultaneous multi-beam pattern.
Detailed Description
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; the continuous wave radar system for detecting the low-altitude small target 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; in the embodiment, the low-low and slow small targets are all called low-altitude, slow-speed and small flying targets, the flying height is generally below 1000 meters, the speed is slow, and the radar reflection area is small.
The transmitting module is used for generating linear frequency modulation continuous waves and radiating the linear frequency modulation continuous waves; after the radiated linear frequency modulation continuous wave is reflected by a target, an echo signal reflected by the target is obtained; 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 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.
A transmitting module: the transmitting module comprises a transmitter, M transmitting antennas, a frequency synthesizer, a time schedule controller and an M1-out 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; referring to fig. 2, a schematic diagram of an antenna assembly of a continuous wave radar system for low-altitude small target detection according to the present invention is shown; wherein each of the M transmitting antennas is a small horn, and the M horns are uniformly disposed on a circular ring, the diameter of the circular ring is d, the M transmitting antennas all adopt a vertical polarization mode, and the horizontal beam pattern and the vertical beam pattern thereof are respectively shown in fig. 3a and fig. 3 b.
Referring to fig. 3c, which is a block diagram of the work flow of the transmitting module, the work flow of the transmitting 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 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; because each path of emission signal is a linear frequency modulation continuous wave, the emission antennas correspondingly selected at each moment are different, namely, the other 1 emission antenna is automatically selected at each moment through the time schedule controller, so that M emission antennas work once in a complete period; in a complete period, the M emission signals are radiated, so that the M emission signals can cover the range of 360 degrees of azimuth and 20 degrees of pitch; the time number of the time schedule controller is equal to the number of the transmitting antennas.
A receiving module: referring to fig. 2, a schematic diagram of an antenna assembly of a continuous wave radar system for low-altitude small target detection according to the present invention is shown; the continuous wave radar system for detecting the low-altitude small target is a continuous wave radar system, and M transmitting antennas in a transmitting module and N receiving antennas in a receiving module cannot be shared, so that a baffle is additionally arranged between the transmitting module and the receiving module and aims to ensure transceiving isolation; the baffle is cylindrical, has a diameter D and a height D4, is placed right below the transmitting module, and has a distance D3 between the top of the baffle and the M transmitting antennas.
N receiving antennas in the receiving module are cylindrical arrays, which have a rows, Y receiving antennas in each row, a × Y being N receiving antennas in total, the diameter of the cylindrical array is D, the height of the cylindrical array is D2, and the receiving antennas are placed right below the baffle, the distance between the N receiving antennas in the receiving module and M transmitting antennas in the transmitting module is D1, the rows in the a rows are arranged at unequal intervals, the N receiving antennas all adopt a vertical polarization mode, the unit form is a dipole or other (easy to place on the side surface of the cylinder), that is, Y array elements surround a circular ring in the horizontal direction to form a circular array, and then a identical circular arrays are obtained, a identical circular arrays are arranged at unequal intervals to form a cylindrical array, and the horizontal beam pattern and the vertical beam pattern of the cylindrical array are respectively shown in fig. 4a and fig. 4 b.
Referring to fig. 4c, a work flow diagram of a receiving module includes a frequency synthesizer, a 1: Z power divider, N receiving antennas, Z b-to-1 switches, Z couplers and Z receivers, where each coupler includes a first input end and a second input end; the output end of the frequency synthesizer is connected with the input end of a 1: Z power divider, Z output ends of the 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 1-selected switch input ends, aX b 1-selected switch output ends are correspondingly connected with Z second input ends of the Z couplers, aX is Z, aY is N, and bX is Y; the Z couplers correspond to the Z receivers one by one, and the working process of the receiving module is as follows:
after the frequency synthesizer generates a required frequency signal, dividing the required frequency signal into Z paths through a 1: Z power divider, obtaining Z path frequency signal components, using the Z path frequency signal components as Z test signals, and respectively and correspondingly sending the Z path frequency signal components to Z couplers, 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; echo signals reflected by the target are respectively received by aX receiving antennas (a total of aX and Z receiving antennas), and enter couplers corresponding to the respective 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.
The frequency synthesizer of the transmitting module and the frequency synthesizer of 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.
The signal processing module: the signal processing is one of the core parts of the radar (especially for the radar), and the signal processing module mainly processes the Z intermediate frequency signals and extracts useful information to complete the processing of target detection and information extraction; the radar signal processing module mainly comprises an A/D conversion part, a digital coherent detection part, a low-pass filtering part, a simultaneous multi-beam forming part (DBF), a pulse compression part, a moving target detection part (MTD), a constant false alarm rate detection part (CFAR), a target parameter estimation part and the like.
Referring to fig. 5, a signal processing module workflow block diagram; z intermediate frequency signals output by the receiving module are directly sent to the signal processing module, and 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; then, carrying out Digital Beam Forming (DBF), pulse compression and Moving Target Detection (MTD) on the Z low-pass filtering digital signals to obtain a moving target detection result, and obtaining a first constant false alarm detection threshold U and a second constant false alarm detection threshold K by adopting a unit average constant false alarm detection method (CA-CFAR), wherein the constant false alarm detection threshold is KU; using a detection threshold KU to perform constant false alarm detection (CFAR) on a moving target detection result 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; and combining the target information and Z low-pass filtering digital signals detected by the external equipment to learn the characteristics of the target, the interference and the environment, increasing or decreasing the second constant false alarm detection threshold K to obtain an adjusted second constant false alarm detection threshold, multiplying the adjusted second constant false alarm detection threshold by the first constant false alarm detection threshold to obtain a new detection threshold, and performing constant false alarm detection (CFAR) on the detection result of the moving target by using the new detection threshold to ensure that the false alarm probability is constant.
For example, under the background of strong clutter, the detection result of the moving target must include clutter, and at this time, the second constant false alarm detection threshold K can be appropriately raised through target, interference and environmental characteristic learning, so as to ensure that the false alarm probability is constant; meanwhile, the signal processing module performs parameter estimation on the Z low-pass filtering digital signals by combining the real low-altitude small target information, namely performs parameter estimation on the real low-altitude small target by using methods such as single-pulse angle measurement or beam scanning angle measurement, so as to obtain pitch angle and azimuth angle information of the real low-altitude small target, and sends the pitch angle and azimuth angle information of the real low-altitude small target to the terminal display module for display.
Specifically, because the radar system is a digital beam forming system, in the process of signal processing, a plurality of receiving beams can be formed simultaneously when the receiving beams are formed through the DBF, so as to cover the radiation range of the transmitting beams, which is equivalent to a "wide transmitting and narrow receiving" system, and the advantages of long residence time of the receiving beams at each wave position and strong clutter suppression capability are provided, which is also an important condition guarantee that the low-altitude target detection radar system obtains strong clutter suppression capability.
Wherein the receive antenna simultaneous multi-beamforming comprises simultaneous multi-beamforming for a horizontal dimension antenna and simultaneous multi-beamforming for a vertical dimension antenna; meanwhile, the a rows of antennas in the vertical dimension are arranged at unequal intervals and can be used for height measurement; it is to be noted that if the number of respective simultaneous multi-beams can be increased by the DBF process in order to reduce the gain loss of the edge beam, the amount of calculation is also increased appropriately.
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 terminal display module, wherein the transmitting module comprises a transmitter, M transmitting antennas, a frequency synthesizer, a time schedule controller and an M-to-1 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; the method comprises the following steps:
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; then, carrying out digital beam forming, pulse compression and moving target detection on the Z low-pass filtering digital signals to obtain a moving target detection result, and obtaining a first constant false alarm detection threshold U and a second constant false alarm detection threshold K by adopting a unit average constant false alarm detection method, wherein the constant false alarm detection threshold is KU; carrying out constant false alarm detection on the detection result of the moving target by using the detection threshold KU 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; and combining the target information and Z low-pass filtering digital signals detected by the external equipment to learn the characteristics of the target, the interference and the environment, increasing or decreasing the second constant false alarm detection threshold K to obtain an adjusted second constant false alarm detection threshold, multiplying the adjusted second constant false alarm detection threshold by the first constant false alarm detection threshold to obtain a new detection threshold, and performing constant false alarm detection (CFAR) on the detection result of the moving target by using the new detection threshold to ensure that the false alarm probability is constant.
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.
The effect of the invention can be further verified by the following simulation experiment:
the arrangement of the radar system in the experiment is as follows: the transmitting antenna is composed of 12 small-sized horns, all the horns are placed on a circular ring by the transmitting antenna, the receiving antenna is cylindrical, 3 rows are provided, 48 antennas are provided in each row, 144 antennas are provided in total, 16 antennas are selected from 48 antennas for simultaneous multi-beam forming through a switch with 1 in 3.
In the experiment, the working frequency of the radar system is X wave band, the wavelength is lambda, and the specific values of the rest parameters are represented by lambda: d is 10.7 λ, D is 15.3 λ, D1 is 10 λ, D2 is 6 λ, D3 is 8.5 λ, and D4 is 0.7 λ. The array element spacing of the horizontal dimension of the receiving antenna is 0.7 lambda, and the array element spacing of the vertical dimension is 2 lambda and 3 lambda.
Next, 18 th to 33 th 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 simultaneously, and the coverage range is 168.75-198.75 degrees.
Experiment 1: the simulation results are shown in fig. 6a, regardless of the horizontal beam pattern of the transmitting antenna; it can be seen from fig. 6a that the beam side lobe level is higher up to-6.7 dB without considering the transmit antenna pattern. To further reduce the beam side lobe level, the transmit antenna horizontal beam pattern may be considered plus.
Experiment 2: the simulation results are shown in fig. 6b, considering the transmit antenna horizontal beam pattern.
Next, simultaneous multi-beam forming in the vertical dimension is simulated by using 3 receiving antennas in the vertical dimension, 4 beams are formed simultaneously, and the central directions of the 4 beams are respectively 2 °, 7 °, 12 ° and 17 °, and cover a range of 15 °.
Experiment 3: the simulation results are shown in fig. 6c, regardless of the transmit antenna vertical beam pattern; it can be seen from fig. 6c that the beam side lobe level is higher without considering the transmit antenna pattern; to further reduce the beam side lobe level, the transmit antenna vertical beam pattern may be considered plus.
Experiment 4: the simulation results are shown in fig. 6d, regardless of the transmit antenna vertical beam pattern.
In conclusion, the simulation experiment verifies the correctness, the effectiveness and the reliability of the method.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention; thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include 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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