Design of high performance frequency synthesizers in communication systems

Abstract

Frequency synthesizer is a key building block of fully-integrated wireless communication systems. Design of a frequency synthesizer requires the understanding of not only the circuit-level but also of the transceiver system-level considerations. This dissertation presents a full cycle of the synthesizer design procedure starting from the interpretation of standards to the testing and measurement results. A new methodology of interpreting communication standards into low level circuit specifications is developed to clarify how the requirements are calculated. A detailed procedure to determine important design variables is presented incorporating the fundamental theory and non-ideal effects such as phase noise and reference spurs. The design procedure can be easily adopted for different applications. A BiCMOS frequency synthesizer compliant for both wireless local area network (WLAN) 802.11a and 802.11b standards is presented as a design example. The two standards are carefully studied according to the proposed standard interpretation method. In order to satisfy stringent requirements due to the multi-standard architecture, an improved adaptive dual-loop phase-locked loop (PLL) architecture is proposed. The proposed improvements include a new loop filter topology with an active capacitance multiplier and a tunable dead zone circuit. These improvements are crucial for monolithic integration of the synthesizer with no off-chip components. The proposed architecture extends the operation limit of conventional integerN type synthesizers by providing better reference spur rejection and settling time performance while making it more suitable for monolithic integration. It opens a new possibility of using an integer-N architecture for various other communication standards, while maintaining the benefit of the integer-N architecture; an optimal performance in area and power consumption.