A systematic approach to the design of reconfigurable LC VCOs is proposed in this paper. The focus is on the choice of the reactive element of the tank most suited to switch the oscillation frequency. The optimum is the component that determines the tank Q. As an example, the design of GSM900/1800 VCO in a 0.13µm CMOS technology, switching a series inductor, is discussed. At this frequency, the tank Q is roughly the inductor Q, and series inductor switching allows area savings with respect to parallel switching.
The trade off .between phase noise and quadrature accuracy, typical of coupled voltage controlled oscillators, is broken if injection locking dividers are used for I and Q generation. Based on the general behavioral modeling of regenerative frequency dividers, this paper derives analytical expressions for locking band and phase deviation from quadrature. An injection locking quadrature generator, embedded in a 0 . l S p CMOS direct conversion receiver, shows 24% frequency locking range while drawing 4mA. The phase deviation from quadrature measured on down-converted signals is 0.8".
IntroductionHighly integrated transceivers for wireless applications have drawn attention, in the recent past, since they lead to potential cost savings. The best suited architectures are direct conversion and low-IF. On the other hand, a power consumption penalty is paid versus traditional multi-chip super-heterodyne solutions. The used technology and a
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