An 802.15.4a wide band frequency synthesizer for 5GHz ISM band health care applications

Abstract

This paper presents a wide tuning, low phase noise, and fast locking CMOS integer-N frequency synthesizer with 1.8V power supply. The proposed design can be used for the IEEE 802.15.4a unlicensed ultra-wideband healthcare applications such as body sensor network. The operating frequency range of the proposed design is ranged from 4.6 GHz to 5.6 GHz for the local oscillator of the RF front-end circuits. The proposed frequency synthesizer consists of a fast-phase-frequency detector charge pump (Fast-PFDCP), a dual mode low-pass loop filter (Dual_Mode_LPF), a voltage control oscillator, an auto-band selection (ABS), an optimum-band selection (OBS), a lock detector, and a pulse-swallow divider. By adapting the Auto Band Selection (ABS), the proposed design can reduce the calibration time by using the binary search algorithm to select the calibration word. In addition, the Optimal Band Selection (OBS) algorithm is proposed to acquire the optimum band which exhibits the minimum VCOμ gainμ variation which can affect the performance of phase noise of overall frequency synthesizer significantly. Furthermore, the design of the voltage-controlled oscillator with the switch-capacitor technique can achieve the wide tuning range and the low phase noise in order to cover the desired operating frequency bands and to accommodate process, voltage, and temperature (PVT) variations. The frequency synthesizer is designed by using the TSMC 0.18μm CMOS 1P6M technology.