The All Digital Quadrature Demodulator Based on Second-order Sampling and Secondary Mixing

Compared to the method based on the first order sampling,the method based on the second order sampling has more freedom in the selection of sampling rate,carrier frequency and the difference of sampling instant in the process of generating the digital I/Q components with different sampling instant.This paper proposes a single IF quadrature demodulation model and obtains a new relation between the sampling rate and the carrier frequency,via generating the digital complex exponential with different sampling instant and using the secondary mixing.This relation expand the selection range of sampling rate,carrier frequency and the difference of sampling instant,and simplify the design of radar system in the front of ADC and the process of ADC.Finally,simulation and analysis are processed to verify our method.