Micromachined Standards for Calibrated Millimeter and Submillimeter-Wave Network Measurements

University Of Virginia Main Campus, Charlottesville VA

Investigators

Abstract

0501391 Barker Intellectual Merit: The test and measurement infrastructure that has played such a pivotal role in the development of microwave and millimeter-wave systems is either scarce, expensive and complex, or does not exist for much of the terahertz region of the spectrum (also known as the submillimeter region and generally regarded as the frequency band extending from 300 GHz to 3 THz). At present, the devices and subsystems being designed for terahertz applications rely primarily on scaled modeling - full characterization of their performance is generally not possible until the device or subsystem has been integrated into a completed instrument. The six-port reflectometer is capable of measuring accurate scattering parameters using fairly simple power detector circuitry. The advantage of this approach is that it is more easily scaled up into the terahertz frequency range than the more complex vector network analyzers. However this technique requires a two-step calibration technique. The first step involves the use of a sliding termination that traces out a circle in the complex reflection-coefficient plane which allows the sixport to be converted to an equivalent four-port reflectometer. This four-port is then calibrated using the standard techniques for network analyzer calibration (ex. short-open-load). Unfortunately, above 100 GHz these sliding terminations are not particularly robust which leads to significant errors in the calibration. Therefore, this project will focus on the simulation and design of measurement standards for calibrating six-port analyzers. A sliding termination can be implemented electronically using RF-MEMS varactors distributed along a short- or open-circuited transmission line. The RF-MEMS variable capacitance is ideal for this application due to the fairly constant loss versus phase shift that can be achieved. However, at submillimeter-wave frequencies the parasitic capacitance and inductance within the RF-MEMS beam will significantly reduce the amount of phase variation that can be achieved. Therefore, this project will investigate novel methods of increasing the achievable phase variation from RF-MEMS devices in the submillimeter region. Broader Impacts: This research program will enhance and support a number of important research, teaching, and outreach activities at the University of Virginia. In addition, the work to be carried out under this grant will be an important step in building a measurement infrastructure for the submillimeter spectrum and instrumentation by providing reliable and precise MEMS standards for instrument calibration. Although most of the initial impact of this work will be felt by the communities that rely directly on millimeter and submillimeter-wave technology this research will also benefit emerging applications such as chemical and biological agent sensing, scaled radar-range systems, and ultra wideband communications. The most important beneficiaries of this program will be the graduate and undergraduate students at the University of Virginia and other institutions involved in high-frequency devices, millimeter-wave engineering, and submillimeter instrumentation research. In addition, our research team at the University of Virginia has close collaborative ties with Virginia Diodes, Inc., a small company focused on bringing terahertz technology to market, as well as the National Radio Astronomy Observatory's Central Development Laboratory.