A fully digital hardware detector for π/4 QPSK

A hardware detector for π/4 QPSK modulation is described. The digitally adjustable diversity detector integrated circuit (DADD IC) is composed entirely of digital logic circuitry and offers significant size and current drain reductions over conventional DSP-based demodulation techniques. The DADD circuit performs two-branch demodulation with the following key features: post-detection diversity phase combining; long-loop and short-loop frequency control; fast-acquisition decision-directed clock recovery with fade protection, and channel quality estimation. The DADD can be readily configured for various data rates, intermediate frequencies, and reference oscillator frequencies. Moreover, with minor modifications the DADD IC can be used to detect other digitally phase or frequency modulated waveforms. As simulations and bench measurements demonstrate, the DADD IC offers excellent static and faded bit error rate performance for either continuous or burst-mode applications