An approach for circuit design optimization based on complexity considerations

• Main Author: Tan, Aaron Zhi Quan
• Other Authors: Goh Wang Ling
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Electrical and electronic engineering::Electronic circuits
• Online Access: https://hdl.handle.net/10356/136800
• Institution: Nanyang Technological University

Optimizing circuit trade-offs is a highly challenging task for any design team. This challenge is further exacerbated with the additional design complexity of integrating multiple circuits. Today, with the increasing demand for newer wireless communication products, design teams face a shorter time-to-market (TTM) for every generation of their new products and each product requires major improvement in wireless capability. Hence, it is important for the design teams to design circuits with complexity in mind. A design approach divided into architecture complexity, component complexity and discretional complexity are proposed. A novel benchmarking figure-of-merit, complexity factor (CF), was formulated and proposed for the architecture complexity. A simulated application of a goal, gain optimization, demonstrated and revealed that a reduction of up to 400% in the normalized complexity factor (NCF) could enhance the gain performance by approximately up to 40% for ultra-high frequency (UHF) applications. As the number of variables to be permuted is very high for the power amplifier (PA) blocks from circuit down to the process level, it is treated as a black box in the analysis but the next topology complexity step addressed this. A topology comparison was proposed between a 2-stacked EDNFET and SGNFET and a 4-stacked resistor-ladder SGNFET PA. Both of them achieved a near 20dBm output power and approximately 60% efficiency on the test-chips measurements, which demonstrated that the 2-stacked EDNFET and SGNFET topology with a reduction in stack height is a potential candidate for a reduced difficulty and complexity Doherty power amplifier (DPA) design. In the discretional complexity step, we explored the linearization of the DPA and proposed a DPA with a gm3 cancellation bias scheme tapping on its intrinsic linearization property, without adding external circuity to increase the complexity of the overall circuit but at the same time, improve its linearity by 6-8dB compared to a DPA optimized for power and more than 9dB compared with a balance PA with a similar structure.