A high-frequency quad-modulus prescaler for fractional-N frequency synthesizer

Abstract

The design of a high-frequency fractional-N frequency synthesizer, which offers technological robustness, versatility, fast locking capability, low noise contribution, superior integration capacity and multi-modulus flexibility, for use in the 2450MHz band (and also support the 910MHz band) operation using a 0.35µm CMOS technology is demonstrated. The design focuses on the prescaler, which is one of the critical speed bottlenecks for phase-locked loop (PLL). A quad-modulus prescaler with programmable division ratios of 16/17/20/21 is implemented using differential current mode logic (CML) latches, OR-embedded CML latches and dynamic OR-gates to minimize dynamic power consumption, avoid glitches and jitter due to mismatch in input signalsâ phases whilst maintaining high-frequency and fast-switching capabilities. The prescaler is able to operate up to 3.87GHz with Iac=21.09mA, and 3.05GHz with Iac=18.09mA. The entire synthesizer design draws 21.34mA from a 3.3V supply, and occupies an area of approximately 0.699mm2.