QPSK/OQPSK Signal Detection with IF AGC on LEO Satellite

The effect of IF (intermediate frequency) analog AGC on QPSK/OQPSK signal detection is evaluated for LEO satellite system where Doppler drift, large dynamic range of signal power and low Eb/No condition are difficult to deal with. The way of setting reference value of logarithmic power based AGC is discussed. Coherent accumulation and non-coherent accumulation are used for detecting, while signal's PDF and performance vs. accumulation times are derived mathematically. Experiment shows that with 60 KHz Doppler offset, Eb/No=0dB under QPSK/OQPSK, only 16 bits was consumed to detect the signal with 99.9% detection probability and 0.1% false alarm probability.