(A) study on high performance CMOS VCOs

다국어 초록 (Multilingual Abstract)

A number of high performance CMOS VCOs/QVCOs are presented in this thesis. These VCOs/QVCOs are all detailedly analyzed and fabricated using advanced CMOS technologies. The measured results verify the new techniques proposed in this thesis.
A self-switched biasing quadrature VCO is presented in this thesis. It is implemented by directly injecting the oscillation signals of one VCO core into the other VCO core through the divided tail current sources without additional active devices for coupling. The proposed coupling structure automatically switches the NMOS FETs used in VCO cores and current sources from strong inversion to accumulation. Since the deep switching of MOSFETs was reported to physically reduce flicker noise, the proposed QVCO is expected to improve the phase noise performance, which is confirmed experimentally. The designed QVCO using 0.18??m CMOS technology operates from 1.86 to 2.2 GHz with a 17% frequency tuning range. The measured phase noise is from -129.1 to -134.5 dBc/Hz at a 1 MHz offset, which is really close to ideal simulation results with the NMOS model disabling the flicker noise components. The average measured phase noise is 7.2 dB below the simulated one with a flicker noise model, which verifies the physical reduction of flicker noise by deep switching of MOSFET. The phase noise Figure-of-Merit (FoM) ranges from 179 to 185 over the entire tuning range. The QVCO dissipates 20mA from a 1.8V supply.
This thesis also presents two oscillators, programmable wideband VCO and QVCO, which adopt modified gyrator-C type active inductors with PMOS transistors in the feedback path. New design equations for an active inductor considering the effects of the parasitic capacitance of PMOS are derived and used to design a high Q active inductor. The fabricated VCO and QVCO achieve frequency tuning ranges from 1.85 to 3.66 GHz and 1.55 to 3.61 GHz, respectively. The measured phase noise of VCO and QVCO range from -81.1 to -111.3 dBc/Hz and from -80.1 to -107.7 dBc/Hz at 3 MHz offset, respectively.
Artificial dielectric is taken advantage to construct variable metal-to-metal capacitor and micro-strip line inductor (also named slab inductor) at millimeter-wave frequencies. These customized passive components are adopted to widen the frequency tuning range of the MMW VCOs. The MMW VCO adopts slap inductor with digitally controllable artificial dielectrics shows less effective in widening the frequency tuning range due to the neutralization in total parasitic capacitance caused by the coupling effect of the two differential inductor lines. This VCO shows a 700 MHz measured frequency range from 36.01 to 37.71 GHz. The measured phase noise at 3 MHz offset is from -97 to -100.7 dBc/Hz. Unlike the variable inductor, the variable metal-to-metal capacitor with digitally controllable artificial dielectrics shows large varying capacitance and high quality factor. The MMW VCO adopting this variable capacitor for sub band frequency tuning achieves a wide frequency tuning range. The measured operation frequency ranges from 43.5 to 45.5 GHz with 2 GHz tuning range while that of the VCO with MTM capacitor only ranges from 44.8 to 46 GHz. The measured phase noises at 3 MHz offset range from -97 to -102.7 dBc/Hz across the entire frequency band. Additionally, a 16-phase MMW VCO is also fabricated using 0.13 RF CMOS technology in this thesis. This multiple phase oscillator is composed of eight VCO cores. These eight VCO cores couple from one to another and finally make up a circle. The measured operation frequency ranges from 19.69 to 23.48 GHz with 19% tuning range. The measured phase noise at 1 MHz offset ranges from -91 to -98 dBc/Hz.
Keywords: artificial dielectric, active inductor, CMOS, current source splitting, digitally controllable, flicker noise, gyrator-C, metal-to-metal capacitor, millimeter-wave, phase noise, programmable, quadrature VCO, self-switched biasing, transmission line inductor, variable, wideband, voltage controlled oscillator

목차 (Table of Contents)

• 1. Introduction 1
• 1.1 Background 1
• 1.2 Applications of oscillator 3
• 1.3 Characteristics of modern CMOS VCO 5
• 1.4 The scope of this thesis 8
• 2. Voltage Controlled Oscillator 9
• 2.1 Introduction 9
• 2.2 Cross-coupled LC oscillator 12
• 2.3 Quadrature LC oscillator 15
• 2.4 Passive components 17
• 2.4.1 Inductor 18
• 2.4.2 MOS varactor 20
• 2.5 Phase noise 24
• 3. Low Phase Noise Self-Switched Biasing CMOS LC Quadrature VCO 28
• 3.1 Introduction 28
• 3.2 Current source splitting VCO 31
• 3.3 Self-switched biasing QVCO through tail current source coupling 33
• 3.3.1 Self-switched biasing technique 33
• 3.3.2 Oscillation modes of the SSB QVCO 36
• 3.3.3 Phase noise analysis of the SSB QVCO 38
• 3.3.4 Negative peak-value of the injected signal 42
• 3.3.5 Quaddrature phase error 43
• 3.3.6 Power consumption of the SSB QVCO 44
• 3.4 Measurement Results and Discussion 47
• 4. Programmable wideband active-inductor based VCO/QVCO 54
• 4.1 Introduction 54
• 4.2 Active inductor design 54
• 4.3 Programmable wideband VCO design 59
• 4.4 Programmable wideband quadrature VCO design 62
• 4.5 Phase noise analysis of this VCO topology 63
• 4.6 Measurement results 67
• 5 Millimeter-wave VCOs 72
• 5.1 Introduction 72
• 5.2 Full custom passive components design 74
• 5.2.1 Variable inductor adopting digitally controllable artificial dielectric 74
• 5.2.2 Variable Metal-to-Metal capacitor using digitally controllable artificial dielectric 78
• 5.3 A high performance MMW VCO using variable inductor with digitally controllable artificial dielectric 83
• 5.4 A wideband MMW VCO adopting variable Metal-to-Metal capacitor with digitally controllable artificial dielectric 90
• 5.5 Multi-phase MMW VCO 97
• 6 Conclusions 101
• References 106