Silicon-based distributed voltage-controlled oscillators

Distributed voltage-controlled oscillators (DVCOs) are presented as a new a pproach to the design of silicon VCOs at microwave frequencies. In this pap er, the operation of distributed oscillators is analyzed and the general os cillation condition is derived, resulting in analytical expressions far the frequency and amplitude. Two tuning techniques for DVCOs are demonstrated, namely, the inherent-varactor tuning and delay-balanced current-steering t uning. A complete analysis of the tuning techniques is presented. CMOS and bipolar DVCOs have been designed and fabricated in a 0.35-mum BiCMOS proces s. A 10-GHz CMOS DVCO achieves a tuning range of 12% (9.3-10.5 GHz) and a p hase noise of -103 dBc/Hz at 600 kHz offset from the carrier. The oscillato r provides an output power of -4.5 dBm without any buffering, drawing 14 mA of de current from a 2.5-V power supply A 12-GHz bipolar DVCO consuming 6 mA from a 2.5-V power supply is also demonstrated. It has a tuning range of 26% with a phase noise of -99 dBc/Hz at 600 kHz offset from the carrier.