Phase Lock for Correlation Detection of a Periodic Pulse

The detection of the presence of a periodic pulse with uncertain pulse rate and low duty cycle is a common biotelemetry problem. Modern phase-lock and correlation techniques have provided more efficient means of making the presence decision than that provided by energy detection methods. A local signal is cross correlated with the input in a phase-locked loop (PLL) to provide phase reference. Upon lock, a local duplicate signal is generated and correlated with the input. A decision threshold operates on the correlator output. The PLL with filter F(s) = (s+a)/s and three appropriate nonlinearities are analyzed for acquisition time and maximum frequency error that will lock.