Free false lock and timing recovery independent frequency detector

In digital modulation for mobile radio telephone services continuous phase frequency modulation with small modulation indexes (MSK/GMSK) is sometimes used. A significant problem in phase-locked loop (PLL) carrier extraction is the initial acquisition. Very narrow loop bandwidth is generally required to control phase jitter, and acquisition may depend on an extremely accurate initial VCO frequency (VCXO) or sweeping. Reducing synchronization delay is important for the mobile communication. The frequency detector (FD) described in this paper, when added to the traditional phase detector, can effect acquisition even with a very small loop bandwidth and large initial frequency offsets. While limited to higher signal-to-noise ratios, the proposed FD is suitable for many applications and can be implemented with simpler circuitry, well suited to IC implementation.