George R. Sloan

An X-band to Ku-band RF MEMS switched coplanar strip filter

Radio frequency microelectromechanical systems (RF MEMS) are key enabling technologies for miniature reconfigurable circuits such as microwave filters. We present a two-pole monolithic RF MEMS switched filter, fabricated on GaAs, that employs surface-micromachined capacitors to present a variable capacitance to a coupled coplanar strip filter, thereby switching the filter center frequency 37% between 10.7 GHz and 15.5 GHz with voltages of 20 and 0 V, respectively. This 15% bandwidth filter occupies a chip area of 2.2 /spl times/1.5 mm and demonstrates less than 2-dB of loss, making it promising for numerous applications within these critical frequency bands.

The modeling, analysis, and design of filter-based parametric frequency dividers

A technique for the design of filter-based parametric frequency dividers is discussed. The technique combines basic divider analysis with modern nonlinear simulation techniques. In essence, the procedure allows the completion of a successful design that is based on computer simulations, but requires little or no nonlinear optimization. Specifically, divider modeling, threshold, and efficiency are investigated, and a straightforward design strategy is given. >

Affordable, miniaturized SAR for tactical UAV applications

Sandia’s fielded and experimental SAR systems are well known for their real time, high resolution imagery. Previous designs, such as the Lynx radar, have been successfully demonstrated on medium-payload UAVs, including Predator and Fire Scout. However, fielding a high performance SAR sensor on even smaller (sub-50 pound payload) UAVs will require at least a 5x reduction in size, weight, and cost. This paper gives an overview of Sandia’s system concept and roadmap for near-term SAR miniaturization. Specifically, the “miniSAR” program, which plans to demonstrate a 25 pound system with 4 inch resolution in early 2005, is detailed. Accordingly, the conceptual approach, current status, design tradeoffs, and key facilitating technologies are reviewed. Lastly, future enhancements and directions are described, such as the follow-on demonstration of a sub-20 pound version with multi-mode (SAR/GMTI) capability.

MEMS high-Q tunable capacitor for reconfigurable microwave circuits

Future microwave networks require miniature high-performance tunable elements such as switches, inductors, and capacitors. We report a micro-machined high-performance tunable capacitor suitable for reconfigurable monolithic microwave integrated circuits (MMICs). The capacitor is fabricated on a GaAs substrate using low-temperature processing, making it suitable for post-process integration with MMICs, radio frequency integrated circuits (RFICs) and other miniaturized circuits. Additionally, the insulating substrate and high-conductivity metal provide low-loss operation at frequencies over 20 GHz. The device demonstrates a capacitance of 150 fF at 0 V bias, pull-in at about 15 V to 18 V, and further linear tuning from 290 fF to 350 fF over a voltage range of 7 V to 30 V. Also, the device demonstrates self-resonance frequencies over 50 GHz, and Q’s over 100 at 10 GHz. To enable integration into circuits, a simple equivalent circuit model of the device has been developed, demonstrating a good match to the measured data through 25 GHz. Initial testing to 1 billion cycles indicates that metal fatigue is the primary limitation to reliability and reproducibility, and that dielectric charging does not have a significant impact on the device. This device is promising for high-performance tunable filters, phase shifters, and other reconfigurable networks at frequencies through K-band.

An Algorithm for Using a Slide-Screw Tuner as a Computer-Controlled Impedance

In the testing of active microwave components, a common test procedure is to evaluate a devices performance when subjected to an all-phase, constant-standing-wave-ratio (APCS) load pull. Such a test specification is useful in verifying a devices stability and mismatch performance. Typically, APCS pulls are tediously performed by hand, with manually operated tuners. However, with the advent of mechanical, computer-controlled tuners, it is now possible to automate this procedure.

Results of the sub-thirty-pound high-resolution miniSAR demonstration

Sandia-developed SAR systems are well known for their real-time, high quality, high resolution imagery. One such system, the General Atomics Lynx radar, has been successfully demonstrated on medium-payload UAVs, including the Predator and Fire Scout. Previously, Sandia reported on its system concept and roadmap for SAR miniaturization, including details of the miniSAR program. This paper and its companions provide an update for miniSAR and discuss the results of the successful May 2005 demonstration of the 26 pound, 4-inch resolution system. Accordingly, the miniSAR system and software implementation and performance are reviewed. Additionally, future plans for miniSAR and the Sandia SAR/GMTI miniaturization efforts are discussed, such as the currently planned miniSAR demonstration onboard a small-payload UAV.

An L-band, LTCC frequency doubler using embedded lumped element filters

We have demonstrated an L-band frequency doubler (1.5 GHz, 33% BW) using an LTCC (low temperature co-fired ceramic) substrate. Lumped element filters were embedded in an LTCC carrier, providing greater than 10:1 footprint reduction over a previous single-layer hybrid implementation.

A Fully Automated, Single-Connection Tester for T/R Modules

This paper was written from both a specific and general point of view. The discussion on the testers instrument integration included an actual block diagram of the Sandia tester; this was done to provide a specific example of how the HP 85110As access links can be utilized. On the other hand, the de-embedding discussion and analysis was carried out from a general point of view to be of maximum service to the reader: the expression one should use to de-embed a measurement is ultimately a function of the measurement environment and the accuracy desired. For example, the usefulness of some of the approximations was shown to be a function of the instruments reflection coefficient at the measurement frequency.