A coherent demodulator for LEO satellites based on dual lock loops

Since dynamic characteristics of low earth orbit (LEO) satellites will induce Doppler shift on carrier frequency and code rate. Therefore, most implementations of traditional receivers for LEO satellites adopt differential demodulation techniques, and the cost is a 3 dB demodulation threshold increment, which raises overall system budget and brings about constraints on practical implementations. This paper presents a new coherent demodulation method based on dual lock loops aiming at large Doppler frequency shift, the variation rate of Doppler frequency and Doppler code shift in LEO satellite communication systems. Simulation results show our presented method can remove influences of dynamic Doppler frequency shift on carrier and code.