Book Description

Radio-frequency power amplifiers are an integral part of today's communication systems. Primary importance is given to improve its efficiency and linearity, which are required for the effective signal transmission. Three main architectures on which, the efficiency of communication systems are based on are: (a) Kahn's technique, (b) Doherty's power amplifiers, and (c) Cheireix out-phasing modulation. Several schemes to implement these techniques exist in literature and their study is very diverse. In this thesis, a detailed literature survey on these techniques is presented, which includes their operation, properties, advantages, disadvantages, and areas of potential applications. This main objective of this thesis is to adopt the Kahn's architecture and implement the various electrical blocks using the latest technology. The main building blocks of the described architecture are: AM/PM signal generator, amplitude detector, dynamic power supply, and a radio-frequency power amplifier. The circuit operation, properties, and circuit-level implementation of all these blocks are presented. The design of a pulse-width modulated buck dc-ac converter used as a dynamic power supply is given. The amplitude-modulated Class-D radio-frequency power amplifier is designed and its performance is evaluated. Each of the circuit-level implementations of the various blocks were designed, built, and simulated on SABER circuit simulator. A test audio signal with frequency 2.5 kHz is generated in the AM/PM signal generator block. A buck dynamic power supply operates at a fixed supply voltage of 25 V with its output voltage varying between 3 V to 23 V. The Class-D radio-frequency power amplifier is designed to generate a carrier frequency of 250 kHz. The efficiency of each stage was determined.