Integrated Oscillators in InGaP/GaAs HBT Technology

Licentiate thesis, 2012

The thesis presents two major concerns in the design of low phase-noise MMIC VCOs; the active device model and the simulation tool. Besides, several design techniques to improve VCO tuning range and phase noise are investigated. The VCOs designed in this work are implemented in InGaP/GaAs HBT technology. First, the device modeling, including HBT and varactor models, is addressed. The large-signal HBT model together with flicker-noise and residual phase noise measurements are introduced. A Varactor model including breakdown noise source is also presented and used in VCO phase-noise simulation. Another concern is the phase noise simulation accuracy using a commercial CAD tool. A short introduction on how the CAD tool simulates phase noise is presented. Then, an alternative approach, calculating phase noise posteriori based on output waveforms from the harmonic balance simulation is described. The posteriori calculation based on the theory of impulse sensitivity function introduced by Hajimiri, [13] are integrated in the CAD soft-ware data display. Three commonly used topologies, balanced Colpitts, cross coupled, and Gm-boosted designs; are introduced and used to verify the accuracy of the phase noise calculation. The last part of the thesis presents three special design techniques for lowered phase noise and/or improved tuning range: a double-tuned VCO, a VCO using Darlington pair transistors, and a strategy to integrate VCOs with a mixer. The associated circuits using the design techniques showed a clear improvement in phase noise performance and tuning bandwidth. The designed circuits bench-marked to state-of-the-art wideband MMIC VCOs show good performance that are in-line with the best results in open literatures.