The Theory of Operation of an Equal-Gain Predetection Regenerative Diversity Combiner with Rayleigh Fading Channels

The theory of operation of an equal-gain predetection diversity combiner employing the Granlund technique of utilizing a combination of feedback and feedforward is presented. It is shown that the time delays of the filters and the loop phase shifts uniquely determine the operating frequencies within the system. The random FM at the discriminator output is shown to be a weighted sum of that on the input signals, and an upper limit for additional random FM caused by phase-shift error between the loops is derived. At the combiner output, the noise is found to be the sum of the uncorrelated noise from each input channel while the carrier amplitude of the diversity signal is the sum of the carrier amplitudes of the input signals after being cophased.