Evaluation of Different MMIC VCO Design Approaches

This paper describes the evaluation of six different MMIC voltage controlled oscillators (VCO's). One of the VCO's is meant to be utilized as basis oscillator in a phase-locked loop (PLL), and the VCO's are all especially sensitive to varactor changes. The intention is to find the most suitable solution, and the evaluation criteria are relative bandwidth, tuning sensitivity, power performance, and pulling figure. The measurements show that a series-resonant VCO with two varactors and the DC control voltages fed through spiral inductors is the most favourable solution. However, this solution is area consuming and can be replaced by an area-minimized version with slightly poorer performance.