A Superregenerative QPSK Receiver

In this paper we present a description and experimental verification of a superregenerative receiver (SR) for QPSK signals. Exploiting the fact that a conventional SR generates pulses which preserve the input phase information, we take N 1-bit samples of each generated pulse. A suitable choice of the sampling frequency gives as a result a bit vector containing a sub-sampled version of each PSK pulse. Extremely simple digital processing of the vectors from two consecutive pulses allows symbol decision, together with information on signal quality and frequency displacements. Although presented for the QPSK case, the principle may be applied to the M-PSK case with obvious changes. Experimental results on a 20 kbit/s proof-of concept receiver in the 27 MHz band, achieving a sensitivity of -103 dBm, with an FPGA-based implementation of the digital part, validate the proposed approach.