Wideband Class-B Power Amplifiers

Vanwege vertrouwelijke informatie of andere redenen is slechts een deel van de publicatie opgenomen in de repository. Due to confidential information or other reasons only a part of the publication is presented in the repository. Wideband Class-B power amplifier is required in Modern communication systems. The bandwidth limitation of Class-B Power amplifier is generally caused by the narrow band 2nd harmonic short. In this thesis the methods of 2nd harmonic manipulation in Class-B power amplifier are discussed. In the beginning, the current and voltage waveforms at output of the amplifier are analyzed, and a series of load configurations which can give good performance in Class-B power amplifier is given. In single-ended topology the traditional 2nd harmonic short networks are band limited and interaction between fundamental impedance and 2nd harmonic impedance limited the performance of short networks. Introducing varactors into the short networks the bandwidth of amplifier is extended. Performance of commercial varactor is restricted by the breakdown voltage and package parasitic. A 32% relative bandwidth Class-B power amplifier is realized with the 90 V break down voltage varactors from the Aeroflex central frequency of the amplifier is 1 GHz, the drain efficiency is above 65% over the frequency band. In differential topology the fundamental signal and 2nd harmonic are isolated, which provides convenience for wideband design. In practical design the bandwidth limitation is generally caused by the non-idea transformer in fundamental matching, compensation capacitors are required at primary of transformer. In low power condition, the 2nd harmonic short bandwidth can be extended by using the coupling between primary inductors. Two loops structure is applied in this case. In high power design, the 2nd harmonic is shorted though the large compensation capacitors. One loop structure is applied in this condition. In simulation result these structures can provide 50% to 70% relative bandwidth, which indicates their potential in wideband Class-B design.

Subject

Power amplifier
Class B
wideband

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http://resolver.tudelft.nl/uuid:560ef9a7-7615-40a2-aefc-7e747b9e4cc7

Embargo date

2010-09-06

Part of collection

Student theses

Document type

master thesis

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