60 GHz silicon transmitters

The continual push for faster wireless systems in consumer devices is driven by the desire for higher performance media streaming, faster sync and better energy efficiency (lower energy per bit). The next generation of wireless links will be enabled by the wide unlicensed bandwidth available at mmWave frequencies and will provide multigigabit per second connections. At the time the majority of this work was done (2006-2010), there were no consumer wireless systems faster than a few hundred megabits per second. The work in this thesis aims to develop key components for a 60 GHz transmitter (TX) in silicon as well as an architecture amenable to integration in a consumer device that can operate at a rate greater than 1 gigabit per second. The first three chapters give an overview of Silicon technology for mmWave systems and cover theory for transmitters and phased arrays. Several optimisations for mm Wave transmitters are shown in Chapter 4 including a method to calculate the optimal number of transmitters given a fixed power budget, why TX/RX switches are preferred and the asymmetry that can arise between devices in a mm Wave ecosystem. Chapter 5 presents a design flow for mmWave circuits that is based on careful modeling and the scaling of low frequency design techniques to mmWave. Two power amplifiers are shown. The first, a board level design at 1GHz which won the high efficiency PA competition at 2007 IMS with an efficiency of 88%. The second is a 60GHz SiGe transmission line based design which achieves a close match to simulation, wide bandwidth and is used in the single antenna transmitter presented in Chapter 7. The outcomes from this work are a design flow for first time right power amplifiers (and mmWave circuits in general) as well as two PAs designed using this flow. Chapter 6 builds on the mmWave PA design presented in Chapter 5. Two transformer coupled PAs are presented. The first a four stage design in SiGe that reduces the area required significantly compared to the transmission line design. A differential topology also enables higher output power by combining two out of phase signals into a single ended signal using an output balun. The second PA is designed in CMOS and achieved state of the art efficiency. It shows the benefit of neutralisation for transformer coupled designs and that the design methodology is equally valid in CMOS technology. Chapter 7 ties the work from the previous chapters together and presents two transmitters for 60GHz operation. The first transmitter is a single chip design with single antenna. The second design uses a novel architecture that enables the front-end to be placed at the end of a coaxial cable and allows for a scalable number of antennas. This architecture (co-invented with Leonard Hall) enables the optimal placement of 60GHz antennas in devices.