Abstract
A multi-modulus divider structure with optimized seamless switching golden states for robust division ratio extension in software defined sigma-delta Frequency synthesizer (FS) is presented in this paper. To support seamless dithering operation of the programmable multi-mode divider (PMMD) on a wide-range divide modulus, the reloading timing of the sigma-delta modulator (SDM) with the corresponding 2/3 divider cell circuit and the switching state when traversing the extension boundary are elaborated. The unified switching golden states are proposed and verified. A PMMD adopting this structure with division ratio ranging from 32 to 127 and a FS utilizing this PMMD are implemented in TSMC 180 nm 1P6M RFCMOS process. The PMMD works at the ratio of 62.5 and 95.8333 without division glitches and the FS covers successive frequency range from 45 MHz to 2.5 GHz with 48 MHz reference frequency. The simulation and measurement results demonstrate the proposed architecture and golden states are valid for seamless dithering and can be applied to software defined FS (SDFS).
Published Version
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