0.18μm 4.8GHz CMOS 1V LC VCO for wireless sensor networks

Wireless sensor network (WSN) can be widely used in many fields. Based on 0.18μm RF CMOS process, this paper presents a 4.8GHz 1V low phase noise LC voltage controlled oscillator (VCO) used in the frequency synthesizer for WSN applications. In order to work under 1V voltage, the LC VCO uses the structure of only one couple of NMOS differential negative resistances. The core circuit is biased by PMOS tail current to reduce sensitivity to power supply and achieve low phase noise, furthermore, it can also decrease power consumption. A 3 bit switch capacitor array is used for wide tuning range without worsen the phase noise performance. The output buffer uses common source structure. With 1V supply voltage, post simulation results show that the tuning range is from 4.61–5.47GHz, the worst phase noise at 1MHz and 3.5MHz offset is −115.1dBc/Hz and −126.2dBc/Hz respectively. And the chip area is 770μm×666μm.