High Speed Target Parameter Estimation In Frequency Diverse Array Radar

Frequency Diverse Array(FDA)has emerged recently and attracts much attention.Different from the phased array,the transmission carrier frequency among the elements of the FDA radar has an offset,which makes the transmission beam of the FDA radar depend on the distance and angle at the same time.The distance-dependent beam makes the FDA radar have great advantages in high-resolution imaging,security communication,anti-electronic interference and distance-dependent clutter suppression.Meanwhile,in the high-speed target scene,in addition to the Doppler frequency shift corresponding to the center carrier frequency,the frequency offset will introduce additional Doppler frequency shift,which can be used to differentiate the blind-speed target.Although FDA radar has great advantages in parameter estimation and target detection,the complicated transmission structure of the FDA radar significantly increases the difficulty of its signal processing,especially in high-speed target scenarios.Therefore,this dissertation mainly focuses on the parameter estimation and target detection of the FDA radar for high-speed target.(1)Different from traditional radars,when detecting high-speed targets,FDA radar needs to consider the additional Doppler shift caused by frequency offset and the target's cross-range unit movement.For high-speed targets without Doppler ambiguity,we proves that ignoring the additional Doppler frequency shift caused by the frequency offset will lead to the range estimation offset.The theoretical analysis shows that this part of the range offset is related to the target speed and the number of accumulated radar pulses.Subsequently,this dissertation proposes a method that can simultaneously correct range migration and Doppler frequency migration to improve the positioning accuracy.For high-speed targets with Doppler ambiguity,the blind velocities corresponding to different carrier frequencies are different,which results in different unambiguity velocities corresponding to the same target.Therefore,the method applied to targets without Doppler ambiguity is not suitable for targets with Doppler ambiguity.Therefore,two Doppler compensation schemes suited for targets with Doppler ambiguity are investigated in this dissertation,one is Doppler compensation method based on zero-padded interpolation,and the other is Doppler compensation method based on Sinc interpolation.The simulation results show that the latter scheme outperforms the former one.(2)Compared with traditional radars,FDA radar can improve the detection performance of blindspeed target without changing the pulse repetition frequency.This dissertation derives the FDA radar MTI(Moving Target Indicators)improvement factor,and theoretically proves the ability of the FDA radar to improve the first blind speed of the traditional radar.Then the position of the blind speed point of the FDA radar is derived.The results show that the blind speed position of the FDA radar is only related to the frequency offset,carrier frequency and pulse repetition period,and has nothing to do with the number of transmitting antennas.Then,the problem of parameter estimation after filtering out the clutter is analyzed.The echo signal of the FDA radar needs to be processed by multiple channels,and the amplitude and phase changes of different channel signals after the filter are different,which will reduce the accuracy of parameter estimation.In response to this problem,a compensation method is proposed to improve the positioning accuracy of the FDA radar.Simulation results are provided to demonstrate the effectiveness of the proposed approach.