Examination Committee

Prof Xiangru ZHANG, CIVL/HKUST (Chairperson)
Prof Howard C LUONG, ECE/HKUST (Thesis Supervisor)
Prof Pui In Elvis MAK, Faculty of Science and Technology, University of Macau (External Examiner)
Prof Philip K T MOK, ECE/HKUST
Prof Patrick YUE, ECE/HKUST
Prof Yi-Kuen LEE, MAE/HKUST

Abstract

Fueled by unprecedented growth in mobile internet, multimedia and cloud computing applications, modern communication networks must support increasingly higher data rates. To achieve this, wireless standards are forced to adopt progressively complex modulation schemes and exploit wider channel bandwidths which present significant design challenges to the frequency synthesizers of a wireless transceiver. This thesis presents a number of circuit and system level techniques to improve the output frequency range and spectral purity of multi-band CMOS frequency synthesizers.
 
The first part of this thesis proposes a reconfigurable dual-band and concurrent oscillator capable of generating harmonically unrelated tones in two frequency bands, 4.7-6.6GHz and 8.5-10.7GHz, either concurrently or one-at-a-time for multi-band radio applications. By exploiting the high non-linearity of a Class-C biased cross-coupled pair, stable coexistence of the two tones is demonstrated to be possible using a single CMOS gm-cell for the first time.
 
The second part focuses on improving the spectral purity and frequency resolution of wideband inductor-less injection-locked PLLs. A phase-domain filtering technique capable of up to 20dB phase-noise and spur suppression is proposed. Additionally, a capacitor-ring coupled oscillator reduces delay-cell mismatches while increasing the number of phases available for injection. Demonstrated in 65nm CMOS, the prototype 1.2GHz synthesizer improves high-frequency phase noise from -115 to - 135dBc/Hz @10MHz, injection spurs from 40.5dBc to -57dBc, integrated jitter from 3.57ps to 1.48ps, and frequency resolution from 48MHz to 2MHz allowing for an inductor-less alternatives to LC-based PLLs in wireless applications.
 
Finally, the design of a millimeter-wave (mmW) sub-harmonic injection-locked (SHIL) fractional-N frequency synthesizer for wireless multi-band point-to-point backhaul communications is presented. The locking range of injection-locked frequency multipliers (ILFMs) are significantly widened due to a proposed 0° rippled phase response and a highly efficient 3rd-harmonic injection current generation technique. Based on this wide locking-range ILFM chain and a dual-modulus divider, a modified SHIL architecture is further proposed to significantly relax the oscillator design trade-offs to simultaneously achieves an excellent output phase noise between -107dBc/Hz and -113.9dBc/Hz @1MHz offset over a wide output frequency range from 20.6GHz to 48.2GHz with a fine frequency resolution of 220kHz while consuming 148mW of power. This architecture allows costly mmW frequency calibration loops required in conventional SHIL-PLLs to be completely removed.