Design Of Ultra-wideband ΔΣ Fractional-N Frequency Synthesizer

Recently, wireless systems and services are proliferating across the world. TheRF transceivers, especially frequency synthesizer, play key roles in wirelesscommunication systems. Frequency synthesizer is performed as the source of thewireless communication system to complete modulation, demodulation, spectrumtransform and so on. Its performance directly determines the quality of wirelesscommunication.In this paper, a ΔΣ fractional-N frequency synthesizer based on Chartered0.18μm RF CMOS process is presented.Based on the system design and the project requirements, the architecture ofultra-wideband ΔΣ fractional-N frequency synthesizer, based on phase-locked loops,is proposed. The main circuit design includes: phase-frequency detector, charge pump,loop filter, voltage-controlled oscillator, programmable divider, ΔΣ modulator, resetcircuit, bandgap reference and interface buffers.The proposed ultra-wideband ΔΣ fractional-N frequency synthesizer is fabricatedin Chartered Semiconductor on April, June and September2012. The test results showthat the proposed ultra-wideband ΔΣ fractional-N frequency synthesizer covered thefrequency range from1.4GHz to1.7GHz, the out-of band phase noise is about-119.49dBc/Hz@1MHz.