Advanced digital modulation schemes used in the wireless applications, result in the modulated RF signals with high peak to average power ratio which requires linear amplification. On the other hand, the demand for a longer talk time with less battery volume and weight, especially in hand-held radio units, necessitate more power efficient methods to be utilized in power amplifier design. But improved linearity and efficiency have always been contradicting requirements demanding innovative power amplifier and linearizer design techniques.
Dynamically varying the load impedance and bias point of a transistor according to the varying envelope of the incoming RF signal also known as Dynamic Load Modulation (DLM) and Dynamic Supply Modulation (DSM), respectively, are two separate methods for improving the efficiency in power amplifier
design. In this dissertation, a combination of both variable gate bias and tunable load concepts is applied in an amplifier structure consisting of two transistors in parallel.
A novel computer aided design methodology is proposed for careful selection of the load and biasing points of the individual transistors. The method which is based on load-pull analysis performs sweeps on the gate bias voltages of the active devices and input drive level of the amplifier in order to obtain ranges of biases that result in the generation of IMD sweet spots. Following that, the amplifier is designed employing the load line theory and bias switching at the same time in order to enhance the efficiency in reduced drive levels while extending the output 1 dB compression point to higher values at higher drives.
Tunable matching networks are implemented utilizing varactor stacks in a &Pi / con
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12615730/index.pdf |
| Date | 01 March 2013 |
| Creators | Ronaghzadeh, Amin |
| Contributors | Demir, Simsek |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | Ph.D. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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