Approved ~

,,-.- iii-Current interest in high-sensitivity receivers for frequency modulation is centered around two implementations of the device: phase-lock and frequency-feedback. Enloe and later Cahn presented linearized frequency-feedback re-ceiver ign theory based on a twin threshold concept. /The derivation of a-linear model for the frequency-feedback receiver, for the situation of Gaussian signals and noise, is presented. A statistical optimization is then performed giving the loop transfer function and threshold performance for a maximum sensitivity receiver. The design theory is based on a si threshold concept dis carding the previous twin threshold approach. It is shown that in an optimum design the modulation error is less than I rad. This allows the use of a narrow-band i-f filter and obviates the need to consider threshold characteristics of the discriminator within the loop