Physical Layer Design of Microwave Communication Link for Quantum Science Experiment Satellite

In order to ensure quantum science experiments can be developed smoothly, a high data rate two-way link for Space-Ground microwave communication must be established. By following the study on Consultative Committee for Space Data Systems (CCSDS) and taking into account the scientific requirements of microwave communication link for quantum science experiment satellite, the physical layer hardware architecture and modulation/demodulation algorithm of microwave communication link for the satellite are presented. The uplink modulation type of the microwave communication link is SRRC-OQPSK, which is accordance with CCSDS spectrum standard. The specification of uplink data rate is 1.024Mbit·s^-1. The downlink modulation type of the microwave communication link is SRRC-OQPSK/GMSK, and the data rate is 4Mbit·s^-1. By compatible tests with several ground stations, it is found that the sensitivity of carrier acquisition is superior to -100dBm, and AGC (Automatic Gain Control) ability is greater than 43dB. Moreover, the bit error rate of actual transmission is superior to 1×10^-9 as the received signal level is equal to -96dBm. The in-orbit verification indicates that the physical layer design scheme of microwave communication link meets the requirements of space quantum science experiments.