High Performance RF Circuit Design: High Temperature, Ultra-Low Phase Noise, and Low Complexity

Advanced achievements in the area of RF circuit design led to a significant increase in availability of wireless communications in everyday life. However, the rapid growth in utilizing the RF equipment has brought several challenges in different aspects of RF circuit design. This has been motivating researchers to introduce solution to cope with these challenges and further improve the performance of the RF circuits. In this dissertation, we focus on the improvements in three aspects of the circuit design. High temperature and temperature compensated transmitter design, ultra-low phase noise signal generators, and compact and low complexity polar transmitter design.

Increase in the ambient temperature can impact the performance of the entire communication system. However, the RF hardware is main part of the system that is under the impact of the temperature variations in which it can change the characteristics of the individual building blocks of the RF chain. Moreover, transistors are the main elements in the circuit whose performance variation must be consider when the design target is compensating the temperature effects. The influence of the temperature variation is studied on the transistors and the building blocks in order to find the most effective approaches to compensate these variations and stabilize the performance of the RF chain at temperatures up to 220 C. A temperature sensor is designed to sense these variations and adjust the characteristics of the circuit components (e.g. bias voltages), accordingly. Further, a new variable gain phase shifter (VGPS) architecture is introduced toward minimizing the temperature impact on its performance in a phased-array transmitter architecture. Finally, a power amplifier as the last stage in a transmitter chain is designed and the variation in its performance with temperature is compensated through the VGPS stage. The transmitter is prototyped to evaluate its performance in practice.

Another contribution of this dissertation is to introduce a novel voltage-controlled oscillator (VCO) structure to reduce the phase noise level below state-of-the-art. The noise to phase noise mechanism in the introduced doubly tuned oscillator is studied using linear time-variant (LTV) theory to identify the dominant noise sources and either eliminate or suppress these noise sources by introducing effective mechanism such as impedance scaling. The designed VCO is fabricated and measurement results are carried out that justified the accuracy of the analyses and effectiveness of the introduced design approach.

Lastly, we introduce a compact and simple polar transmitter architecture. This type of transmitters was firstly proposed to overcome the serious shortcomings in the IQ transmitters, such as IQ imbalance and carrier leakage. However, there is still several challenges in their design. We introduce a transmitter architecture that operates based on charge to phase translation mechanism in the oscillator. This leads to significantly reduction in the design complexity, die area, and power dissipation. Further, it eliminates a number of serious issues in the design such as sampling rate of the DACs. comprehensive post-layout simulations were also performed to evaluate its performance.