| A millimeter wave linear frequency modulated continous wave(MMWLFMCW) radar has many advantages,such as small volume,light weight, high integration,wide bandwidth,high resolution,low probability of intercept and strong anti-jamming performance, and it is applied in many fields,for example, precision-guided,battlefield survellience, automative collision avoidence system,industrial control and environment remote sensing.Based on a pratical project for developing short-range guided radar,the dissertation has put importance on short-range MMWLFMCW radar target signal models, multiple-target movement parameters estimation, parasitic amplitude modulation suppression and phase noise's effects on multiple-target detection performances through the theoretical analysis, simulation and pratical experiments, and simulates the multiple-target echos with ground clutter based on measured data from a designed Ka band LFMCW radar. The research would be summarized as follows:(1) MMWLFMCW radar target echo signal expressions are derived in the time and frequency domain respectively. The multi-period and single-period ambiguity function of symmetrical triangular LFMCW signal with large time-bandwitdth product are derived through the solution of signal complex envelope, and their characteristics are analyzed and compared. Effects of system noise,sweeping frequency nonlinearity and time domain window on the MMWLFMCW radar range resolution are discussed in detail.(2) Methods for multiple-target range-velocity decoupling are studied. Firstly, for shortcomings of exisiting multiple-target detection methods, the dissertation presents a new method to decouple range-velocity ambiguity with emitting a transformable periods LFMCW signals .This method makes use of target echo signal spetrums symmetry in the down/up sweep frequency area of symmetrical triangular wave to reject clutters and improve detection performances. The new method uses sliding windows to detect the targets' signal spectrum peak and improves the parameter-estimation precision. Secondly, the dissertation puts forward a method of combining fractional Fourier transform with Radon-Ambiguity transform for multiple-target range-velocity decoupling. The fractional Fourier transform would correctly estimate signals' central frequency on the basis of frequency modulation rate estimation using Radon-Ambiguity transform and acquire the accurate targets' range. Lastly, a method of combination fractional autocorrelation with fractional Fourier transform to realize multiple-target range-velocity decoupling is presented. This method adopts iteration to implement one dimensional search for estimating frequency modulation rate and reduces the computation compared with Radon-Ambiguity transform. Simulation results have proved validity of these methods.(3) Methods for detecting multiple-target with acceleration are researched. A beta signal of MMWLFMCW radar target with acceleration is analyzed and the relationship between beta signal parameters and target movement parameters is established. The acceleration ambiguity function of millimeter wave radar signal and acceleration resolution expresstion are derived, and acceleration effects on performance of MMWLFMCW radar are studied. For shortcomings of Wigner-Ville distribution and Radon Transform to estimate multiple-target movement parameters, a new method is presented with modified Wigner-Ville distribution and Radon transform to reduce the cross-term of Wigner-Ville distribution and imporves the targets' parameters estimation precision. Simulation results have proved the conclusion.(4) A parasitic amplitude modulation and phase noise effects on radar performances are analyzed and discussed. A parasitic amplitude modulation existed in a MMWLFMCW radar is discusse and the causes of the parasitic amplitude modulation is analyzed by deriving the expressions of voltage controlled oscillator output signal with variable capacitor tuned. An intermediate frequency amplifier is designed to suppress the parasitic amplitude modulation and suppression effect is also analyzed. A beta signal model of a MMWLFMCW radar with consideration of a phase noise is established and its effects on multiple-target detection performace is analyzed.(5) Clutter measurement is investigated and multiple-target echos are simulated with ground clutter. A Ka band LFMCW radar for clutter measurement is designed and implemented, and cultter measurement principle and technique are discussed in detail. Backscattering coefficients are measured of some ground objects with this LFMCW radar system, and the effective independent samplings and numbers of measurement for the measurement are computed according to the experiment condition. The processing software platform is established and software gate is applied to suppress the interference signal in data processing. Measuring error factors causing are analyzed and errors are estimated, and the system accumulative error is summarized. The dissertation aslo simulates Weibull clutter with special power sepctrum using zero memory nonlinearity transfrom method on the basis of ground clutter measurement results,and simulates MMWLFMCW radar multiple-target echos with the ground clutter at low grazing angle.
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