Brian M. Pierce

Comparison of split post dielectric resonator and ferrite disc resonator techniques for microwave permittivity measurements of polycrystalline yttrium iron garnet

Two techniques are evaluated for the accurate measurement of the microwave permittivity of polycrystalline yttrium iron garnet (YIG) at frequencies between 5.5 and 12.5 GHz: split post dielectric resonator (SPDR) and ferrite disc resonator (Courtney). Both techniques separate YIG permittivity from that of YIG permeability by applying a magnetic induction bias to the YIG sample under test. The SPDR method needs no special sample preparation in the case of YIG substrates, whereas the Courtney method requires the grinding of rods from bulk YIG. The Courtney measurements of the YIG real permittivity are found to be higher on average than SPDR measurements. Agreement between the two techniques improves with increasing magnetic induction bias.

Array antennas using low loss MEMS phase shifters

A line source of sixteen 5-bit MEMS phase shifters was used for beam scan of a novel X-band CTS (continuous transverse stubs) antenna over +/- 45 degrees in the H-plane. The 5-bit phase shifter has 1 dB loss on average over 6-10 GHz. The building block of these phase shifters is a cantilevered MEMS switch developed by HRL Laboratories. The metal-contact switch is characterized by 0.15 dB loss and 40 dB isolation at 10 GHz.

Microwave Components with MEMS Switches

RF MEMS switches with metal-metal contacts are being developed for microwave applications where broadband, high linearity performance is required. These switches provide less than 0.2 dB insertion loss through 40 GHz. This paper describes the integration of these switches into selected microwave components such as reconfigurable antenna elements, tunable filters, switched delay lines, and SPDT switches. Microwave and millimeter wave measured results from these circuits are presented.

Expanding Human Cognition and Communication

In order to chart the most profitable future directions for societal transformation and corresponding scientific research, five multidisciplinary themes focused on major goals have been identified to fulfill the overall motivating vision of convergence described in the previous pages. The first, “Expanding Human Cognition and Communication,” is devoted to technological breakthroughs that have the potential to enhance individuals’ mental and interaction abilities. Throughout the twentieth century, a number of purely psychological techniques were offered for strengthening human character and personality, but evaluation research has generally failed to confirm the alleged benefits of these methods (Druckman and Bjork 1992; 1994). Today, there is good reason to believe that a combination of methods, drawing upon varied branches of converging science and technology, would be more effective than attempts that rely upon mental training alone.