FPGA implementation of BPSK modem for telemetry systems operating in noisy environments

BPSK modulation is widely used approach in industrial telemetry systems for digital communication over noisy channels due to inherent high noise immunity and low bit-error rate (BER). The most critical part of the BPSK modem implementation in a programmable digital system is the design of demodulator part. We studied characteristics and trade-offs for two commonly used approaches to the BPSK demodulator implementation, which are both suitable for efficient field-programmable gate array (FPGA) implementation: the incoherent BPSK demodulator, based on the complex product demodulation, and the coherent BPSK demodulator, based on the carrier synchronization using internal phase-lock loop (PLL) (Costas Loop) and numerically controlled oscillator (NCO). We employed correlation filter and integrator for symbol synchronization. We compared overall characteristics for both approaches, in terms of robustness in noisy environments and FPGA implementation complexity.