Design of a 4.5-5.8 GHz differential LC VCO using 0.35m SiGe BiCMOS technology

Abstract

In this paper, a 4.5-5.8 GHz, Gm LC voltage controlled oscillator (VCO) for IEEE 802.11a standard is presented. The circuit is designed with AMS 0.35m SiGe BiCMOS process that includes high-speed SiGe Heterojunction Bipolar Transistors (HBTs). According to measurement results, phase noise is -102.3 dBc/Hz at 1MHz offset from 5 GHz carrier frequency. A linear, 1300 MHz tuning range is obtained utilizing accumulation-mode varactors. Phase noise is relatively low due to taking the advantage of differential tuning concept. Output power of the fundamental frequency changes between -1.6 dBm and 0.9 dBm depending on the tuning voltage. Average 2nd and 3rd harmonic levels are -25 dBm and -41 dBm, respectively. The circuit draws 14 mA DC current from 3.3 V supply including buffer circuits leading to a total power dissipation of 46.2 mW. The prototype VCO occupies an area of 0.6 mm2 on Si substrate, including DC and RF pads.