Study On Monopulse Angle Estimation For Wideband Linear Frequency Modulation Radars

In modern radar systems,wideband radars are widely used with advantages such as strong anti-jamming capability and high accuracy of parameter estimation,and the linear frequency modulated(LFM)pulses are the main waveforms of the current wideband radars.Since range resolution is normally inversely proportional to the bandwidth of the transmitted pulses,wideband LFM radars can form the high resolution range profile(HRRP)of targets from the radar returns.Wideband LFM radars are becoming increasingly important,while the angle estimation for wideband signals is little studied in previous works.Therefore,we focus on the problem of monopulse angle estimation for wideband LFM radars in this article.And the main objectives of our research work can be summarized as follows:(1)The model of wideband linear frequency modulation signal is discussed in detail.The processes of down converting,sampling,filtering,and dechirp process are simulated in our model.And the final output of this signal model is obtained in discrete form.(2)As noise in wideband radars has larger bandwidth than narrowband radars,the challenge lies in the accumulation of energy from the high resolution range profile of monopulse.To accumulate the energy of the received echo signals from different scatterers of the same target,we propose to utilize a monopulse angle estimation algorithm based on cross-correlation operation,which can achieve a good performance in low signal-to-noise ratio(SNR)conditions.In the proposed algorithm,the problem of angle estimation is converted to estimating the frequency of the cross-correlation function.Experimental results verify the effectiveness of the algorithm,and demonstrate the performance of the proposed algorithm compared with the traditional monopulse angle estimations.Based on the performance requirements of the algorithm implementation,we describe the parallel implementation of three important modules of the algorithm on CUDA.Besides,the results and time-consuming comparisons of the algorithm implementation on GPU platform and MATLAB platform are also presented.(3)To solve the problems of adopting traditional monopulse angle estimations for multi-targets angle estimation within the beam,we propose to utilize the filter banks to separate the targets and perform monopulse angle estimation for multi-targets based on wideband LFM radars.Furthermore,to deal with the problem of nonlinear phase of prototype low-pass filter causing the decrease of the accuracy of angel estimation,an improve algorithm is also proposed.In the improve algorithm,the filter banks are used to guide the rectangle windows to select the signals in the channels where the targets are located respectively.Experimental results verify the effectiveness of the algorithm,and demonstrate the performance of the algorithm adopting rectangle windows is better than the algorithm adopting filter banks.