ABSTRACT
In the transmitter/receiver pairing, the transmitter has the advantage because, at every moment, it controls what data it is transmitting, what the carrier phase and frequency are, and where the communications are in the Protocol Data Unit (PDU) structure. However, the receiver needs to determine this information on its own based only on what information is transmitted. Synchronizing the data flow between the transmitter and the receiver must be performed when either device is initialized or reset, and when the communications link fails. The receiver performs the following operations on the received data stream to make the synchronization process work: recovers the data clock rate and synchronizes to the bit pattern, achieves synchronization with PDU structure and achieves synchronization with the PDU internal data. The synchronization functions are not an artifact of the telemetry link only but occur for telecommand links as well. This chapter covers these three tasks and some of the techniques involved.
