Comparison of frequency detectors for low Earth orbit satellite communications systems

The requirement of a carrier synchronisation system to track the significant Doppler frequency shift of a transmission from a low Earth orbit (LEO) satellite has been investigated. The performances of two frequency estimator structures have been compared in the presence of the time-varying Doppler shift characteristic of the transmission from a LEO satellite and AWGN. The frequency detector derived from maximum likelihood principles has been shown to have a superior performance under these conditions. The complexity of the two detectors is comparable, both can share the operations of the data filters, limiting the additional computing burden