Synchronization techniques for a frequency-hopped wireless transceiver

The implementation of robust synchronization algorithms and architectures for master-slave configured frequency-hopped radios with frequency-shifted keying (FSK) modulation is described. The synchronization scheme, both acquisition and tracking, is based on a simple time division duplexing (TDD) frame structure, which consists of a pilot tone, a frame ID (Word Sync), and actual data. The acquisition process is accomplished by means of frame synchronization, based on coarse energy detection of the received signal and the pattern matching of a 2l-digit Barker code. The proposed scheme for synchronous-access frequency-hopped transceivers is much simpler than a parallel search method based on parallel matched filters, and relatively faster compared to a PN acquisition scheme based on serial search. Although FSK signals are detected noncoherently, a frequency tracking loop is required to compensate for the carrier frequency offset between the transmitter and receiver. The receiver also needs a time tracking loop to recover the clock from the received data. Both loops use a digital phase-locked loop architecture with programmable loop bandwidths.