To satisfy the requirements of high spatial resolution and high sensitivity for distributed synthetic aperture radiometers, and to reduce inter-satellite data transmission pressure, this paper presents a research study on high-speed signal processing based on a distributed system, discussing a mixed quantization asymmetric digital correlation method. On the basis of pure digital quantization correlation, a method of pairwise correlation between second-order and eighth-order quantization is proposed, and its correction formula from the digital correlation coefficient to the analog correlation coefficient is derived. Simulations of the influence of the correlation coefficient, quantization threshold, and sampling frequency on various digital quantizations were carried out using MATLAB software. The output of the digital correlator and the efficiency factor were derived, demonstrating that the proposed mixed quantization asymmetric correlation method can enhance the sensitivity of the synthetic aperture microwave radiometer system. The efficiency factor obtained from the second and eighth order correlation method proposed in this paper has increased from 63% for the traditional second order quantization to 78%, nearing the efficiency factor of the third order quantization correlation.