Design of a 4.2-5.4 GHz LC VCO for IEEE 802.11a Applications

In this paper, a 4.2-5.4 GHz, -G_m LC voltage controlled oscillator (VCO) for IEEE 802.11a standard is presented. The circuit is designed with AMS 0.35 mum SiGe BiCMOS process that includes high-speed SiGe heterojunction bipolar transistors (HBTs). Phase noise is -110.7 dBc/Hz at 1 MHz offset from 5.4 GHz carrier frequency and -113.5 dBc/Hz from 4.2 GHz carrier frequency. A linear, 1200 MHz tuning range is obtained utilizing accumulation-mode MOS varactors. Phase noise is relatively low due to taking the advantage of differential tuning concept. Output power of the fundamental frequency changes between 3 mW and 3.5 mW depending on the tuning voltage. The circuit draws 2 mA without buffers and 14.5 mA from 2.5 V supply including buffer circuits leading to a total power dissipation of 36.25 mW. The circuit occupies an area of 0.6 mm² on Si substrate