SiGe Bipolar VCO With Ultra-Wide Tuning Range at 80 GHz Center Frequency
Nils Pohl, Hans-Martin Rein, Thomas Musch, K. Aufinger, Josef Hausner
IEEE Journal of Solid-State Circuits, Volume 44, pp. 2655-2662, Oct. 2009
A SiGe millimeter-wave VCO with a center frequency around 80 GHz and an extremely wide (continuous) tuning range of 24.5 GHz (~30%) is presented. The phase noise at 1 MHz offset is ?97 dBc/Hz at the center frequency (and less than ?94 dBc/Hz in a frequency range of 21 GHz). The maximum total output power is about 12 dBm. A cascade buffer improves decoupling from the output load at reasonable VCO power consumption (240 mW at 5 V supply voltage). 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 limitation of the tuning range in millimeter-wave VCOs are shown and the improvement by using two (instead of one) varactor pairs is demonstrated.