Echo cancellation is of great potential for a radar cross section reduction in stealth technology. All the techniques developed in the last decade rely primarily on the assumption that cancellation echo and target echo synchronize in the time domain. However, the cancellation echo may lag behind the target echo when countering a synthetic aperture radar (SAR). This is because the cancellation echo generation requires extra processing time when the SAR transmits and receives large time bandwidth product signal such as linear frequency modulation pulses. Thus, the cancellation echo and target echo cannot cancel each other perfectly. In this paper, we develop a novel three-stage active cancellation method using frequency and delay-time modulation to cancel out the target echo. In this scenario, the cancellation echo will intentionally lag behind the target echo. Theoretical analyses and simulation results verify the effectiveness of the proposed method.