CN-118549929-B - Target detection method based on FMCW-OAM radar target imaging

Abstract

The invention provides a target detection method based on FMCW-OAM radar target imaging. The orbital angular momentum OAM carried by the vortex electromagnetic waves can provide more target information in radar imaging and target detection. According to the invention, vortex phase is added into the traditional frequency modulation continuous wave FMCW radar, so that the azimuth imaging performance of the FMCW radar is improved, the measurement accuracy is not influenced by the actual azimuth of a target, the target distance and the speed, and the azimuth detection range is widened. Meanwhile, compared with a pulse OAM radar, the FMCW-OAM radar has the advantages of small short-distance detection blind area, high measurement precision, low power consumption, low sampling frequency and the like.

Inventors

• Liao Die
• LUO ZHIBANG
• CHEN SIHUI

Assignees

• 电子科技大学

Dates

Publication Date

20260508

Application Date

20230927

Claims (2)

1. 1. The target detection method based on FMCW-OAM radar target imaging is characterized by comprising the following steps: 1) A signal transmitting step: The transmitter of FMCW-OAM radar imaging model uses uniform circular array UCA with N array elements to generate FMCW-OAM signal, uses array as origin to build XYZ coordinate system, the nth array element uses the t time unit, the first vortex electromagnetic wave mode and the transmitted signal in one frequency modulation period The method comprises the following steps: , ; is the carrier frequency of the wave, Representing the frequency modulation rate of the LFM signal, Is a phase offset set for obtaining the eddy current phase, azimuth angle of each array element N=0,..n-1, l=0,..l-1, L is the total number of modes of the FMCW-OAM signal; the total emission signal of the UCA with the uniform circular array is ; The transmitter transmits L FMCW-OAM signals of different modes simultaneously; 2) Signal reception chirp removing step: The receiver of the FMCW-OAM radar imaging model adopts a single antenna to receive, and the echo signal of the received target is combined with the signal Mixing to obtain mixed signal Represented as , wherein, Is that Order Bessel function, intermediate quantity , In order to uniform the radius of the circular array UCA, 、 And Representing the distance, azimuth and pitch angle of the target relative to the radar center respectively, Is the time delay of the double-pass distance, the intermediate quantity , 、 The distribution represents X, Y coordinates of the object in the coordinate system, For the target speed to be the same, Representing the included angle between the speed of the target and the positive direction of the X axis; at a sampling frequency For a pair of Sampling, sampling the signal Is that , wherein, Representing the frequency shift caused by the linear doppler frequency, Is the carrier frequency Corresponding wavelength, sample number variable , Is the number of samples in the frequency modulation period; 3) And a data storage step: sampling P times in each scanning period of a receiver of the FMCW-OAM radar imaging model, wherein a complete detection period comprises M scanning periods, L.times.P.M received data samples are obtained by one detection, the data samples are stored in a three-dimensional data matrix, and sampling data in one scanning period are stored along the row direction of the matrix; 4) A target distance measuring step: FFT is calculated on data samples along the row of the three-dimensional data matrix, namely p-dimension, so as to obtain frequency domain data : ; To perform frequency domain variation after p-dimensional FFT conversion in period, the method comprises the steps of calculating Obtaining frequency domain values ; Obtaining the distance of the target , wherein, For the bandwidth of the baseband signal, Is the speed of light; 5) A target azimuth measuring step: For data samples along columns of a three-dimensional data matrix The dimension performs an FFT to obtain azimuth information of the target, , wherein, OAM mode range for signaling , As azimuth, PSF is point spread function; 6) A target speed measuring step: FFT is carried out on a three-dimensional data matrix of data samples obtained in M scanning periods according to the period dimension M dimension to obtain frequency domain data , ; Wherein, the Frequency domain variance after FFT transformation for different period dimension M-dimensions, m=0,.. Obtaining frequency domain values ; For the intermediate quantity it is, ; Obtaining the actual speed of the target 。
2. 2. The method of claim 1, wherein the resolution in the distance direction Azimuth angle resolution Speed resolution 。

Description

Target detection method based on FMCW-OAM radar target imaging Technical Field The invention relates to a radar target detection technology, in particular to a target detection technology based on FMCW-OAM radar target imaging. Background Due to the introduction of the orbital angular momentum OAM, the vortex electromagnetic EM wave propagates in a spiral manner such that its phase distribution is spiral in the azimuth direction. This feature allows the vortex electromagnetic waves to convey more information than conventional plane waves. Thus, the swirling electromagnetic wave can bring more information back from the target within the beam radiation range without consuming a long coherence time or occupying a large spectrum bandwidth. In recent years, vortex electromagnetic waves have been widely focused and studied in the fields of communication, radar imaging, and the like. In 2013, li Liling et al introduced OAM into diffraction tomography, realized that super resolution imaging .[5]L.Li and F.Li,"Beating the rayleigh limit:Orbital-angular-momentumbased super-resolution diffraction tomography,"Phys.Rev.E,vol.88,p.033205,Sep 2013. Liu Kang et al of objects established echo signal models of MIMO and MISO OAM radar imaging systems, successfully realized two-dimensional distance-azimuth imaging .K.Liu,Y.Cheng,Z.Yang,H.Wang,Y.Qin,and X.Li,"Orbital-angularmomentum-based electromagnetic vortex imaging,"IEEE AWP Letters,vol.14,pp.711–714,2015. for OAM beams of different modes with different main lobes in different directions, studied the use of concentric circle arrays to calibrate the radiation position .K.Liu,Y.Cheng,X.Li,Y.Qin,H.Wang,and Y.Jiang,"Generation of orbital angular momentum beams for electromagnetic vortex imaging,"IEEE AWP Letters,vol.15,pp.1873–1876,2016. of the main lobe, and developed and improved the application of vortex electromagnetic waves in the field of gaze imaging. The vortex electromagnetic wave is also applied to SAR imaging, so that the eddy electromagnetic wave imaging is realized by adopting a compressive sensing method to improve the resolution J.Wang,K.Liu,Y.Cheng,and H.Wang,"Vortex sar imaging method based on oam beams design,"IEEE Sensors Journal,vol.19,no.24,pp.11 873–11 879,2019.. higher in azimuth angle of SAR, and compared with the prior Range Doppler (RD) algorithm, the method effectively solves the azimuth angle profile problem under high sidelobe level .Y.Zeng,Y.Wang,C.Zhou,J.Cui,J.Yi,and J.Zhang,"Super-resolution electromagnetic vortex sar imaging based on compressed sensing,"in 2020 IEEE/CIC International Conference on Communications in China(ICCC),2020,pp.629–633. The current radar imaging system adopting vortex electromagnetic waves is mostly pulse radar, namely OAM radar. The signal transmitted by the OAM radar is a high-energy pulse signal, the transmitter needs to have high power, the pulse radar needs to directly process echo signals, and the requirement on sampling frequency of a receiving end is high. Disclosure of Invention The invention aims to solve the technical problem of providing a target detection method for realizing vortex phase by adopting continuous frequency modulation waves and establishing an FMCW-OAM radar system to improve the imaging performance of the conventional radar. The technical scheme adopted by the invention for solving the technical problems is that the invention provides a target detection method based on FMCW-OAM radar target imaging, comprising the following steps: 1) A signal transmitting step: The transmitter of the FMCW-OAM radar imaging model generates an FMCW-OAM signal by using a uniform circular array UCA with the total number of array elements being N, and establishes an XYZ coordinate system by taking the array as an origin, wherein the nth array element is in a t time unit in a frequency modulation period, the mode of the first vortex electromagnetic wave, and the transmitted signal s n (t; l) is as follows: f c is the carrier frequency, K represents the frequency modulation rate of the LFM signal, Is a phase offset set for obtaining the eddy current phase, azimuth angle of each array elementN=0..n-1, l=0..l-1, L is the total number of modes of the FMCW-OAM signal; the total emission signal of the UCA with the uniform circular array is The transmitter transmits L FMCW-OAM signals of different modes simultaneously; 2) Signal reception chirp removing step: The receiver of the FMCW-OAM radar imaging model adopts a single antenna to receive, and the echo signal of the received target is combined with the signal Mixing to obtain mixed signal s '(t; l), sampling s' (t; l) with sampling frequency F s, sampling to obtain sampled signal F (omega; l) asWherein J l is the Bessel function of the order I, the intermediate quantityA is the radius of a uniform circular array UCA, R T,And theta T denote the distance, azimuth and pitch angle of the target with respect to the radar center,Representing the frequency shift caused by the l