Broadband Switch-Mode Radio Frequency Power Amplifiers using Tunable Ferroelectric Thick-Film Components

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This project covers fundamental investigations on thermal effects in novel ferroelectric (Barium Strontium Titanate) varactors for RF amplifiers when exposed to high power at high frequencies. In addition, one major objective is to achieve efficient RF- and DC-decoupling for dynamic biasing. This is aimed to be accomplished by enhanced varactor layouts, in uniplanar as well as multilayer structures by considering coupled electrical and thermal properties at the same time, and by using different material preparation methods for thick-film and bulk ceramics. Special attention is put to reduce thermal resistance by using alternative substrate materials and a high-power package. Especially the high-power package requires dedicated investigations, as it influences the electrical as well as thermal properties of the device. The novel varactors will be modeled, characterized and optimized under large signal operation. Reliable models will be developed to enable simulation of tunable circuits at different temperatures as well as different power levels.As a proof-of-concept, a demonstrator integrating tunable matching networks into GaN-HEMT based power amplifiers with output power up to 50 W will be designed for a telecom band in the 0.9 to 3.0 GHz range. Efficiency and linearity of the tunable power amplifier will be investigated with signals up to 20 MHz bandwidth for the first time. Novel varactor biasing and RF- and DC-decoupling will be realized for dynamic operation and first dynamic behavior will be investigated using two-tone signals in large-scale operation.