The design and measurement results of a fully-differential fundamental-wave VCO based on the Colpitts topology are presented. The circuit is realized in a 0.13-?m SiGe BiCMOS technology with a maximum oscillation frequency of 300 GHz. Design measures taken to minimize phase noise and to achieve high output power without using any output buffer are discussed. Operating at a supply voltage of 3.3V, on-wafer measurements show a tuning range of around 12 GHz from 147 to 159 GHz. The circuit achieves a maximum output power of 9 dBm (at 3.3V) and 9.8 dBm (at 3.6 V), both with an efficiency of around 6% and consumes a DC power of 132 mW and 164 mW, respectively. The average measured phase noise of the VCO over the entire tuning range is -92 dBc/Hz at 1 MHz offset, with a minimum phase noise of -96 dBc/Hz around 157GHz. The VCO demonstrates state-of-the-art performance in D-Band both in terms of output power and phase noise.