| This thesis explores low-voltage harmonic integrated radio-frequency (RF) voltage-controlled-oscillators (VCOs) for systems-on-chip (SoC) and means of isolating them from external noise disturbances. This issues is of increasing importance to as chips are required to mingle sensitive analog functions with and increasingly dense array of digital electronics.; Focusing on 5-GHz LC-VCOs, this work suggests two ways that extrinsic noise can be blocked. First, a circuit technique is considered wherein a common-mode noise sensor (CMFB) block is attached to the VCO and used to suppress externally caused variations around the tank by controlling the bias source. Second, a device technique is forwarded wherein a novel varactor device with intrinsic common-mode rejection is used.; Simulations indicate that the CMFB can suppress the effect of common-mode noise from the supplies by 30-dB, while allowing a 1-GHz tuning range around a 5-GHz center frequency and 1.8-V power supply. The differential varactor structure is shown to suppress un-modulated power supply noise by as much as 70-dB (relative to differential input noise). This novel structure was designed and studied in a 2D-device simulator and implemented in an experimental 0.18-mum CMOS 5-GHz VCO along with the CMFB. Measurement results indicate a 10-fold decrease in VCO tuning sensitivity to quasi-static noise disturbances on the supply. Further, the circuit is shown to suppress 2nd harmonic distortion for 10-mV, 5-MHz disturbances introduced on the supply. |
