A 2.4-GHz Monolithic Fractional-$N$ Frequency Synthesizer with Robust Phase-Switching Prescaler and Loop Capacitance Multiplier
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The design of a 2.4-GHz fully integrated ΣΔ fraction-N frequency synthesizer in o.35-μm CMOS process is presented. The design focuses on the prescaler and the loop filter, which are often the speed and the integration bottlenecks of the phase-locked loop (PLL), respectively. a 1.5-V 3-mW inherently glitch-free phase-switching prescaler is proposed. It is based on eight lower frequency 45°-spaced phases and a reversed phase-switching sequence. The large integrating capacitor in the loop filter was integrated on chip via a simple capacitance multiplier that saves silicon area, consumes only 0.2 mW, and introduces negligible nose. The synthesizer has a 9.4% frequency tuning range from 2.23 to 2.45 GHz. It dissipates 16 mW and takes an active area of 0.35 mm2 excluding the 0.5-mm2 digital ΣΔ modulator.
author list (cited authors)
Shu, K., Sánchez-Sinencio, E., Silva-Martínez, J., & Embabi, S.