A functional description of the Buffered Telemetry Demodulator (BTD)

This article gives a functional description of the buffered telemetry demodulator (BTD), which operates on recorded digital samples to extract the symbols from the received signal. The key advantages of the BTD are (1) its ability to reprocess the signal to reduce acquisition time, (2) its ability to use future information about the signal and to perform smoothing on past samples, and (3) its minimum transmission bandwidth requirement as each subcarrier harmonic is processed individually. The first application of the BTD would be the Galileo S-band contingency mission, where the signal is so weak that reprocessing to reduce the acquisition time is crucial. Moreover, in the event of employing antenna arraying with full spectrum combining, only the subcarrier harmonics need to be transmitted between sites, resulting in significant reduction in data rate transmission requirements. Software implementation of the BTD is described for various general-purpose computers.