A Non-Linear Correction Method for Terahertz LFMCW Radar

The nonlinearity in terahertz (THz) linear frequency modulated continuous wave (LFMCW) radar usually blurs the range profile and decreases the signal to noise ratio, hampering applications where high range-resolution is particularly emphasized. A software correction method, which comprises of transmitted nonlinearity estimation and nonlinear phase compensation for the beat signal, is proposed in this paper to drastically reduce the nonlinearity in THz LFMCW radar. Besides the commonly considered nonlinearity caused by voltage-controlled oscillator (VCO), the nonlinearity from other broadband hardware devices have also been included in our modified correction model, which gives the advantage of preciser compensation. Moreover, utilizing the phase gradient autofocus (PGA) method to estimate the transmitted nonlinear term and the residual video phase (RVP) removal method to remove the range dependency of the received nonlinearity, our method can uniformly compensate the nonlinearity in the whole range profile. In addition, no presupposed parametric model for the nonlinearity waveform is needed, which further strengthens the effectiveness of the proposed method in practical use. Both the simulated data and the real tested data, acquired by a 190 GHz radar with 60 GHz bandwidth, has been used to demonstrate the validity and the effectiveness of the method.