Square-Law Device Analysis for the Detection and Timing Estimation of a BurstBPSK Signal

摘要

A square-law device is often found in the receiver front end of radar andcommunication devices. The two outputs of a square law device were analyzed in terms of output signal to noise ratio (SNR) for a burst binary phase shift keyed (BPSK) modulated pulse. After first deriving the device's output for a general BSPK signal, a closer examination was performed for a 13 bit Barker code which was selected for its good autocorrelation properties. The baseband component was shown to have a 2-3 dB performance advantage over the bandpass component. This SNR advantage increases as the frequency uncertainty of the input signal and hence, the input filter bandwidth, increases. The SNR of a BPSK modulated pulse following the enveloped detector and lowpass filter is compared to that obtained from a CW pulse having an equal power and duration. From the comparison, an expression is derived that transforms the E(sub b)/N(sub o) for a burst BPSK modulated signal to an equivalent E(sub b)/N(sub o) for a CW pulse. This can be utilized in parameter estimation and signal detection analyses for BPSK modulated pulses.