A 19-23 GHz integrated LC-VCO in a production 70 GHz fT SiGe technology

Abstract

Integrated LC-VCOs for microwave frequencies are widely used nowadays. Traditionally, a lot of attention is paid to optimize the quality factor of the integrated inductor and varactor. The active part of the oscillator, used to undamp the resonator circuit, is often implemented as a cross-coupled differential pair. Even with a near-loss-less resonator circuit, this cross-coupled pair inherently puts a limit to the maximum attainable oscillation frequency. We derive a relation for this maximum attainable frequency f/sub cross/, and demonstrate a 19-23 GHz integrated LC-VCO approaching this theoretical limit for our IC-technology.