LC Voltage-Controlled Oscillators

The explosive growth in wireless communications has driven universities and companies to produce wireless transceivers at low-cost, low-power, and compact size. Recently, all of RF components, such as low-noise amplifiers (LNAs), mixer, local oscillators (LOs), and IF Filters, seem possible to be integrated in CMOS scaled technology. On-chip passive elements such as spiral inductors and varactors make on-chip implementation of LC-tank voltage-controlled oscillators (VCOs) easy.In this thesis, the theory and practice of LC VCOs are studied, and many key techniques in circuit implementation were explained in a simple way.First, this thesis briefly introduces the fundamental theory of oscillators and oscillator's class. All kinds of the circuit structures of narrowband, wideband, and quadrature-output LC-VCOs are also presented.The design, simulation and optimization of on-chip inductor are studied. Three methods of analysis and simulation of on-chip inductor are summarized briefly. We have proposed the effective capacitance model of two neighbor metals in on-chip inductors, and calculate the parasitic capacitance of serial multilayer inductors. In order to improve the quality factor of on-chip inductor, multipath metal structure and double reverse-biased PN junctions in deep-Nwell are proposed.Secondly, this thesis describes a new prediction method of tuning curves of a LC-tank VCO with period calculation technique. With this period calculation technique, the prediction of oscillator's tuning curves is more accurate compared with the traditional harmonic approximation. The simulation and measurement agree well with the results obtained from the theoretical analyses.We have studied three analysis methods of phase noise: linear time invariant(LTI), nonlinear time invariant(NTI) and linear phase time varying(LPTV). The underlying physics of LC oscillators is analyzed in detail. The general process of LC-VCOs' design and optimization is summarized, and we proposed the method of Rs/L minimization in the inductor selection. With linear time invariant(LTI) modeling of phase noise, we calculate the minimum phase-noise factor of LC VCOs, and summarize many techniques of lowering phase-noise. The inductive voltage control is proposed to lower the even harmonics in the oscillating voltage and to lower the phase noise, which comes from even harmonics.In the end, we have designed and tested two LC VCOs in CSM 0.35um RF/Mixed CMOS process, which are applied to the TV Tuner applications.