Low cost and low power open-loop frequency synthesiser

A fully integrated frequency synthesiser based on a low-cost and low-power multifunctional phase-locked loop (PLL) is proposed for frequency shift keying applications. The optimised open-loop modulation circuit and its digital control module are detailed. The 0.166 mm² synthesiser is implemented in a 0.28 μm CMOS technology with 2.5 V supply voltage. Measurement results related to the open-loop frequency drift and demodulated signal together with the PLL lock time are presented.