Abstract
On-chip integrated transformers are one of the main passive structures widely used in building blocks like LNA, VCO, PA, balun etc. And it can not only save die area compared with transmission line, but also gives more design freedom and easy biasing circuit design compared with inductors. Firstly, the dissertation discusses different kinds of transformer models, especially with simplified T-model and Magnetically Coupled Resonator (MCR), to guide the transformer-based RF Integrated Circuit (IC) design. Secondly, three different kinds of power combiners are researched for transformerbased power combining applications. Finally, an X-band CMOS power amplifier (PA) with shrinking process node is proposed to meet the requirement of higher integration density in modern wireless communication systems. The PA is implemented with the most shrinking standard CMOS technology of 40 nm, while still covering the entire X-band frequencies (8-12 GHz). In the proposed PA, transistor cells are designed with neutralization capacitors to increase stability and gain performance. As a trade-off among gain, output power, and PAE, the transistor cells in driving stage and power stage are biased for class A and class AB operation, respectively. Both transistor cells consist of two transistors working in differential mode. Furthermore, transformer-based matching networks are used to realize a two-stage X-band CMOS PA with compact size. The PA achieves an effective conductivity (EC) of 117.5, which is among the highest in recently reported X-band PAs in CMOS technology. The PA also attains a saturated output power Psat of 20.7 dBm, a peak PAE of 22.4%, and a gain of 25.6 dB at the centerfrequency of 10 GHz under a 1 V power supply.