CMOS linear power ampflier with a transmission-line transformer

Abstract

An RF power amplifier is one of the most crucial elements in wireless communication systems, since it is the most power-consuming component. It is also one of the most difficult blocks to integrate in a CMOS technology. CMOS active devices have low breakdown voltage, low current driving capabilities, and large capacitances, while passive devices suffer from substrate loss at high frequencies. Power-transistor models are usually not available from CMOS foundry companies. In spite of the above shortcomings, however, CMOS is an optimum integration solution, and that is why CMOS is competing with compound-semiconductor technologies in RF power amplifiers. Many efforts have been made to overcome the problems in CMOS and realize a fully-integrated CMOS power amplifier. One of the solutions is to use a transmission-line transformer as an output matching network, instead of on-chip passive components with low quality factors. In this thesis, presented are fully-integrated CMOS linear power amplifiers with an on-chip transmission-line transformer. The transmission-line transformers were designed by performing electro-magnetic (EM) simulations. Power transistors were also measured and modeled so that a circuit simulator predicts the exact performance of the designed power amplifiers. The proposed model extends its range to turnoff region, and includes the parasitic resistances, inductances, capacitances, and skin effects of combining metal patterns. Two CMOS power amplifiers were designed for 900-MHz mobile-RFID reader applications. The one, fabricated in a 0.18-μm CMOS technology, provided a gain of 28.2 dB, a $P_{1dB}$ of 21.8 dBm, and PAE of 19 % at the $P_{1dB}$, with a supply voltage of 1.8 V. The power amplifier achieved a $P_{1dB}$ larger than 24 dBm with a supply voltage of 2.5 V. From the measured and simulated performance of the power amplifier, the proposed power-transistor models were verified. The other power amplifier, fabricated using a 0.25-μm CMOS ...