The objectives described in this proposal address the development and application of advanced methods for realizing circuit elements which are fundamental to microwave and mm-wave component design. The research focuses on new microwave transmission line architectures whose electrical characteristics can be manipulated using electrostatically-controlled tuning elements. By eliminating the need for RF-active device control, and incorporating microelectromechanical systems (MEMS) processing techniques, these lines will offer great latitude for integration, and are inherently fit for incorporation into MEMS microsensor design. The related education plan introduces the study of modern microwave sensor systems, through foal-world applications demonstrating the combined use of microwaves and other sciences.
The methodology used to produce the tunable transmission lines derives from the equivalence of distributed lines to cascaded, electrically small, series inductor-shunt capacitor (LC) pairs. In the planned approach, transmission line sections will be synthesized from LC pairs, each of which incorporates micromechanical tuning elements. The characteristic impedance and propagation constant, which are the defining properties of the transmission line, can be adjusted over wide tuning ratios using this new approach; a realistic goal is to achieve impedance ratios of 20:1. The tuning elements are monolithic, electro-statically driven micromembranes which flex under applied DC bias. These geometries are readily fabricated using conventional integrated-circuit and MEMS processing techniques.
As integrated microwave and mm-wave circuit design is based on distributed transmission line technology, the potential impact of variable impedance transmission lines is significant. Fundamentally new approaches to the design of matching networks, filters, attenuators and couplers are among the possible uses of these lines. They are a Iow-power, essentially passive alternative to active (RF) device control, and thus an enabling technology for applications such as advanced phased array antennas, integrated sensor/communications systems, and RF-analog/digital chips.
The research efforts will concentrate on determining optimal geometries for the tuning elements and control electrodes, and on their utilization in the transmission line configurations. Issues relating to drive voltages, propagation loss, frequency bandwidth and phase compensation will be addressed. This work will be conducted using experimental characterization in combination with circuit-level and numerical electromagnetic modeling. The approach will be demonstrated in the design of mm-wave, variable matching networks and attenuators.
The education plan centers on the development of a Sensor System Design course. This senior level, project-based course will use a case study of a real-world, microwave sensor application as the focus of each semester offering. Individual students, or groups of two, will be responsible for the design and development of particular sub-systems, e.g., RF, communications and signal conditioning. A significant feature of this course is that each sensor will be conceived in collaboration with a USF research center or a local company, which will provide the relevant scientific background, assist in system architecture design, and manage the actual field-deployment of the sensor. Development risks are minimized by keeping commercial off-the-shelf versions of each sub-system on-hand, and by maintaining a strictly academic association with the collaborators. The design course will pursue the objective of helping students learn how to learn, while at the same time providing a broad exposure to system-level engineering applications. Opportunities to transfer course material to community youth groups are planned. ***
