The synchronous oscillator: a synchronization and tracking network

The synchronous oscillator (SO) is a free-running oscillator which oscillates at its natural frequency in the absence of an externally applied signal. In the presence of a signal, the oscillator synchronizes with and tracks the input waveform with an acquisition time inversely proportional to the tracking bandwidth. The SO possesses a constant output signal amplitude in the tracking region and an adaptive tracking bandwidth proportional to the input signal level. The authors present the theory and experimental characterization of SOs in terms of selectivity, noise rejection, carrier-to-noise improvement, tracking range, and acquisition time. A specific application is described for SO carrier and clock recovery networks in 60- and 120-Mb/s QPSK modem with bit-error-rate (BER) performance approaching that of hard-wired connection.