Design of Intermediate Frequency Signal Synchronization Acquisition in Satellite-Borne Synthetic Aperture Microwave Radiometer

The satellite-borne synthetic aperture microwave radiometer utilizes multiple antenna pairs to form baselines for detecting the brightness temperature signal of the target. Compared to traditional real aperture microwave radiometers, it has the characteristic of higher resolution. However, the phase difference between multiple antenna channels is one of the crucial factors affecting the accuracy of brightness temperature numerical inversion. To reduce the phase difference between the multiple channels of intermediate frequency signals, firstly, the principle of intermediate frequency signal acquisition in the synthetic aperture was analyzed, highlighting the impact of phase difference on inversion accuracy. Secondly, a synchronization method for the sampling clock and data reception clock was designed to further enhance the stability and consistency of the phase difference. Finally, this design method was experimentally validated. The results demonstrate that the proposed method has a phase difference stability of less than 0.03°, a phase difference consistency of less than 5°, the effective number of bits for all six channels are greater than 10.4, and the isolation degree between different channels exceeds 80 dB. The research results indicate that the proposed method effectively enhances the reliability of intermediate frequency synchronization acquisition unit in the satellite-borne synthetic aperture microwave radiometer, laying a solid foundation for subsequent processing.