Reconfigurable and Broadband Circuits for Flexible RF Front Ends

Abstract: Most of today’s microwave circuits are designed for specific function and special need. There is a growing trend to have flexible and reconfigurable circuits. Circuits that can be digitally programmed to achieve various functions based on specific needs. Realization of high frequency circuit blocks that can be dynamically reconfigured to achieve the desired performance seems to be challenging. However, with recent advances in many areas of technology these demands can now be met.Two concepts have been investigated in this thesis. The initial part presents the feasibility of a flexible and programmable circuit (PROMFA) that can be utilized for multifunctional systems operating at microwave frequencies. Design details and PROMFA implementation is presented. This concept is based on an array of generic cells, which consists of a matrix of analog building blocks that can be dynamically reconfigured. Either each matrix element can be programmed independently or several elements can be programmed collectively to achieve a specific function. The PROMFA circuit can therefore realize more complex functions, such as filters or oscillators. Realization of a flexible RF circuit based on generic cells is a new concept. In order to validate the idea, two test chips have been fabricated. The first chip implementation was carried out in a 0.2μm GaAs process, ED02AH from OMMICTM. The second chip was implemented in a standard 90nm CMOS process. Simulated and measured results are presented along with some key applications such as low noise amplifier, tunable band pass filter and a tunable oscillator.The later part of the thesis covers the design and implementation of broadband RF front-ends that can be utilized for multistandard terminals such as software defined radio (SDR). The concept of low gain, highly linear frontends has been presented. For proof of concept two test chips have been implemented in 90nm CMOS technology process. Simulated and measurement results are presented. These RF front-end implementations utilize wideband designs with active and passive mixer configurations.We have also investigated narrowband tunable LNAs. A dual band tunable LNA MMIC has been fabricated in 0.2μm GaAs process. A self tuning technique has been proposed for the optimization of this LNA.