Optimization of SiGe VCOs for Wireless Applications

This paper describes the optimization of phase noise performance in fully integrated SiGe HBT differential LC-tuned voltagecontrolled oscillators (VCOs) for wireless applications. An accurate expression for phase noise in SiGe HBT LC-tuned VCOs is presented which takes the non-linear operation of the oscillator into account. The expression is derived using conversion-matrix analysis and include the transfer of wideband noise sources in the LC-tuned VCO into close-in phase noise. Design methods are shown which minimize the different sources of phase noise toward the intrinsic limit set by the resonator quality factor. A set of 2 GHz differential SiGe HBT VCOs have been implemented in a 0.5 μm, 47 GHz SiGe BiCMOS process to provide experimental verification of the benefits of the design methods presented in this paper.

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