Modulated Frequency Synthesizers: Design for Wideband and High Efficiency Modulation

This book presents a wideband GFSK-modulated fractional-N frequency synthesizer which using the two-point delta-sigma modulation (TPDSM). Two bottlenecks in this design have been rigorously investigated. One is the nonlinear performance of fractional-N frequency synthesizers. The other one is the inherent gain and delay mismatch between the two modulation points. Both nonlinear and mismatch factors dominate the modulation accuracy in the closed phase-locked loop (PLL). The proposed formulation can successfully predict the dependencies of the modulation accuracy on both factors. The comparison of the averaged frequency deviation and frequency-shift-keying (FSK) error between theory and measurement shows excellent agreement. The modulated frequency synthesizer implemented in this study can achieve a 2.5 Mbps data rate as well as a 15 ¿s PLL stable time with only 2.2 % FSK error under good design and operating conditions.

Kang-Chun Peng, PhD: Studied Electrical Engineering at National Sun Yat-sen University. Assistant Professor of Computer and Communication Engineering at National Kaohsiung First University of Science and Technology, Taiwan.