A coherent digital demodulator for multiple signal formats and widely varying data rates

The tracking and data relay satellite system (TDRSS) uses four ground station demodulators for K-band signals with data rates from 1 kb/s to 300 Mb/s. The author discusses the feasibility of replacing these demodulators with a single digital demodulator that may be reconfigured by altering stored parameters to accommodate all signal formats and data rates. This implementation will reduce total ground station cost and facilitate automation of ground station operation. Analysis of system performance concentrates on the carrier tracking loop. Analytic and simulation results relate system performance to parameter values and signal format as data rate and power vary independently on the in-phase and quadrature channels. It is demonstrated that a single digital demodulator can support TDRSS-compatible signals at data rates conservatively extending from 1 K symbols/s to 10 M symbols/s, using off-the-shelf hardware with six or more bits of accuracy