Design Of Low Power Quadrature VCO Of WSN Transceiver Chip

Wireless Sensor Network (WSN) is an automatic network system composed of plenty of mini sensor nodes which are deployed in monitoring area. It is mainly used in intelligent home, environmental monitoring, health care and military security, etc. The growing development of WSN is driving a need for a more stable and low power consumption frequency synthesizer in wireless transceivers, and four quadrature signals of low consumption at high matching must be supported by frequency synthesizer in RF transceiver circuit. Therefore, as the decisive part of frequency synthesizer, the design of quadrature voltage-controlled oscillator (QVCO) is necessary.Based on the analysis of the theory of PLL frequencysynthesizer and voltage-controlled oscillator, the architecture of a low power quadrature voltage-controlled oscillator of WSN transc is given.This article presents a quadrature voltage-controlled oscillator,which consists of two identical complementary cross-coupled voltage-controlled oscillators coupled via transistors in parallel way.With the 4-bit switch capacitor array,it can cover the frequency tunning range.By using the 5-bit current switch array,operating current of the quadrature VCO can be easily controlled.The design is based on Candence simulation platform and implemented in TSMC 0.18μm RF CMOS process. Shown by the simulation, at the temperature of 27° C, the process corner of TT,the supply voltage of 1.8V and the situation of current switch of 11000, the proposed quadrature voltage-controlled oscillator (QVCO) has a frequency tuning range of 2.23GHz-2.81 GHz and a phase noise better than-114.8dBc/Hz@1MHz.The phase difference between two quadrature signals is 91.4 ° while consuming only 2.85mA.The performance of the quadrature voltage-controlled oscillator (QVCO) meets design requirement well and it can be applied in WSN RF transceiver chip.