Direct microwave demodulation

The technical characteristics, advantages and disadvantages of three types of coherent direct microwave demodulators are discussed. Bypassing the intermediate frequencies normally present in radio circuitry is a means to lowering equipment costs and enhancing reliability. The phase, frequency and spectral demodulators described all allow carrier recapture with a Costas loop. In all cases, the demodulation is performed at an intermediate frequency after transposition of the modulated carrier wave. MSK, 4 PSK and 16 QAM modulations are considered, together with circuitry for each and experimental results. Finally, the progress toward development of an integrated receiver is assessed.