Optimizing Phase-Noise Performance: Theory and Design Techniques for a Crystal Oscillator

At the heart of today's communication systems lies the autonomous signal source, the oscillators. The design criteria for these are governed by a system's requirements (based on its applications). Oscillators have evolved over the past century and today offer a wide range of options with stringent specifications in terms of power consumption, performance, and cost. Optimizing for phase noise with improved overall performance is considered a key design criterion, and a figure of merit (FOM) that includes all important parameters then determines the oscillator performance [1]-[3]. This article describes the winning entry in the IEEE Microwave Theory and Techniques Society (MTT-S) 2016 International Microwave Symposium (IMS2016) Student Design Competition (SDC) for the category focused on a low-phase-noise 100-MHz crystal oscillator, which was sponsored by Technical Committees MTT-17 and MTT-21 [4]. All competition participants received identical crystal resonators from the same vendor; hence, the major task was to design a circuit using novel noise-cancellation techniques to realize a low-phase-noise signal source. Here, we discuss the various limitations in the design of quartz crystal-resonator-based signal sources and present a novel approach for achieving high dc-RF conversion efficiency ( h) without degrading phase noise and oscillator FOM performance [5]-[7].