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The conductor and dielectric loss mechanisms in microstrip reflectarray are described using simulation models and waveguide measurements. The dielectric constant and loss tangent variation with frequency is obtained for a particular substrate using existing datasheets. Variable size patch reflectarray element was studied for loss characterization. The effect of these losses is characterized and the potential cause for the loss phenomenon is provided. It is observed that the dielectric loss and copper loss occur near the patch resonance due to strong electric fields in the substrate region below the patch and the large currents on the top surface of the patch, respectively. Index Terms--Conductor loss, dielectric loss, reflectarray.

A microstrip-fed semi-elliptical dipole antenna (MFSEDA) is proposed and designed for ultrawideband (UWB) communications. The antenna has large bandwidth covering the frequency band from 3.1 to 10.6 GHz, radiation patterns similar to those of a conventional dipole antenna, and small size with the dimension of only about one third of the wavelength instead of half wavelength for the lower frequency. With simple and proper modification of the radiation patches, a frequency-notched antenna based on the MFSEDA is also designed and good band-notched performance from 5.0 to 6.0 GHz can be obtained. Measured results show that these MFSEDAs are suitable for UWB applications due to their high performances. Index Terms--Band-notched antenna, planar elliptical antenna, ultrawideband (UWB) antenna.

For high data rate applications, current suspension interconnect solutions should stay above 50 Ohm differential impedance ([Z.sub.diff]) due to footprint limitations and frequency dependent ohmic losses of the stainless steel plane at low [Z.sub.diff]. This paper describes the impedance and bandwidth (BW) design space of today's interconnects and also shows why this technology is still compatible with current system front-ends up to 3 Gb/s. Furthermore, the benefits of reduced power and higher overshoot using less than 50 Ohm impedance and high bandwidth interconnects are explored with a system model. Three alternate low impedance interconnect structures are used to demonstrate these benefits, and are explored analytically and evaluated for mechanical tradeoffs. Index Terms--Coupled transmission lines, microstrip, multiconductor transmission lines, preamp.

This paper presents a novel transition between a microstrip line and a substrate integrated waveguide (SIW) in a multilayer substrate design environment. In order to achieve a low-loss broadband response, the transition, consisting of a tapered or multisectionai ridged SIW and a tapered microstrip line, is modeled and designed by simultaneously considering both impedance matching and field matching. Characteristic impedance and guided wavelength calculated by using closed-form expressions based on a transverse resonant method are used to develop our design procedure. Effective broad bandwidth is obtained in two examples developed in this study, which are validated with simulated and measured results. This transition provides a simple way to design substrale integrated circuits with buried microstrip circuits in the multilayer substrate in which any ratio of impedance transform can be anticipated. Index Terms--Microstrip line, multilayer structure, ridged waveguide, substrate integrated circuits (SICs), snbstrate integrated waveguide (SIW), transition.

A design for a gaseous radiation detector based on charge multiplication is described and its performance assessed. The device uses a microstructure which has an anode surrounded by another close-lying second anode, playing the role of a grid at a potential between anode and cathode that allows a more accurate definition of the multiplication volume. The main characteristics of this Gridded Microstrip Gas Chamber (G-MSGC) detector are described. The best energy resolutions for 5.9 keV X-rays obtained were 13.4% for Xe and 12.6% for the P10 mixture. Index Terms--Energy resolution, gas detectors, microstrip, P10, x-ray detectors, xenon.