Decision Directed AFC for Noncoherent Detectors Experiencing Large Signal Dynamics

This paper presents a decision directed non-coherent AFC scheme for use with M-ary Frequency Shift Keying (MFSK) where accurate tracking and noise/jitter performance under large dynamics are required. The AFC uses a linear discriminator to obtain good tracking performance with an associated small degradation in noise performance. Analysis is performed to examine the effects of noise on the linear discriminator and AFC loop and comparisons are made between this linear AFC and nonlinear FFT based schemes under the influence of noise and large dynamics. This AFC is intended for use with any MFSK system and specifically for a frequency-hopping system employing MFSK as a modulation technique. The AFC may also be easily generalized to any orthogonal modulation technique such as M-ary Code Shift Keying or M-ary Time Shift Keying.