Design and implementation of a code-phase-shift keying spread spectrum receiver employing a FPGA baseband decoder

In this paper, we present the design of an M-ary direct sequence spread spectrum receiver employing a novel code-phase-shift keying (CPSK) signaling scheme, with each of the M signaling waveforms derived from a different phase shift of a single pseudonoise sequence. The receiver consists of an IF demodulator and a CPSK baseband decoder, implemented using discrete components and a FPGA chip, respectively. A modified double-dwell serial search scheme is used for data acquisition and tracking, and the carrier-phase synchronization is solved by a Costas loop in the IF demodulator and a double threshold detection scheme in the CPSK decoder. Measurements of receiver performance are presented and compared with theoretical calculations.