An 80 GHz SiGe Bipolar VCO with Wide Tuning Range Using Two Simultaneously Tuned Varactor Pairs

A SiGe millimeter-wave VCO with a center frequency of 80 GHz and an extremely wide (continuous) tuning range of 23 GHz (29%) is presented. The phase noise is ap -95.5 dBc/Hz (at 1 MHz offset frequency) and the total output power ap 12 dBm. A cascode buffer improves decoupling from the output load at reasonable VCO power consumption (240 mW). A low- power frequency divider (operating up to 100 GHz) provides, in addition, a divided-by-four signal. As a further intention of this paper, the basic reasons for the limitations of the tuning range in MMW-VCOs are shown and the improvement by using two (instead of one) varactor pairs is demonstrated.