Equivalent Approach to Analyze the Nonlinearity of LFMCW SAR

The linearity of linear frequency modulated continuous wave synthetic aperture radar (LFMCW SAR) is an important index to measure the linear frequency modulated (LFM) signal and can cause great effect on imaging quality of SAR. Aiming at nonlinearity of LFMCW and combining the characteristic of LFMCW SAR system, nonlinear frequency error is analyzed and sidebands effects of frequency fixing with different reference signal are discussed. An equivalent approach to transform nonlinear frequency error into addictive noise by virtue of phase errors is proposed and effect of equivalent noise on LFMCW SAR range resolution is analyzed through simulation. Results demonstrate that lower linearity can cause larger effect on beat frequency and signal-to-noise ratio (SNR). The proposed method can provide new thought for the elimination of nonlinearity influence based on signal processing.