Wide-band ground-plane DC block and bias feed

The realization of a wideband, ground-plane DC block and bias feed for microstrip transmission lines operating in Ka-band, 26.5-40.0 GHz, is described. The waveguide-to-microstrip fixture and transition used for testing are described. Analysis of the ground-plane bias gap structure is provided. A few possible applications are discussed     

Frequency doubling in GaAs/AlGaAs field effect transistor usingreal space transfer

A modified field effect transistor (FET) topology is used which enhances the real space transfer of carrier out of the channel toward a special collector terminal. The drain current rises, peaks, and then reduces as gate voltage is increased due to a steep rise in collector current with gate voltage. When biased near the peak, the AC drain current induced by the gate is folded over becoming frequency doubled. The device exhibits functional multiplexing being operable as either a positive transconductance, negative transconductance, or frequency doubling element setable via quiescent gate voltage     

Ferroelectric phase shifters and their performance in microwave phased array antennas

Abstract

Recent advances in the development of Barium Strontium Titanate ferroelectric composition has made possible reasonable performance of ferroeletric phase shifters to frequencies up to 10 GHz. These material improvements, coupled with phase shifter circuit design changes have resulted in phase shifts greater than 360 degrees with less than 6 dB insertion loss. In particular additives to the BaxSr1-_xTiO₃ composition have been shown to exhibit a consistent electrical phase shift verses DC potential over parameters of temperature and humidity. These ferroelectric material improvements and circuit design changes, included with the development of multiple ferroelectric phase shifters makes possible the fabrication of a low cost electronic scanning antenna. A single four element phase shifter was used with a one dimensional linear antenna array which was constructed on three layers and used an aperture coupled distribution technique. Individual elements of this multiple four element phase shifter were evaluated with respect to uniformity phase shift and insertion loss. The four element antenna was fed by four ferroelectric phase shifters and the phase shifters are corporately fed by the microwave source. The ferroelectric phase shifters are controlled via a dedicated microcontroller which calibrates out element phase variations and provides a real time scan capability for the antenna assembly.     

Field effect real space transfer transistor

We report demonstration of the first field effect real space transfer transistor (FERST), a gated real space carrier transfer device. It is a dual output, multifunctional device which, depending on region of operation, demonstrates either of three characteristics: traditional FET transconductance, sign reversing transconductance, or dual output with near complimentary transconductances. Additionally, the FERST structure provides a new means for exploring the physics of real space transfer     

Increased dielectric quality factor in planar resonators byselective dielectric removal

A means for increasing the effective dielectric quality factor by selective removal of dielectric from a microstrip resonator is discussed. Methods for determining the impedance and effective dielectric constant are included. The reduction in loss compared with an equivalent microstrip resonator is presented     

Design Rules for Addressing Material Asymmetry Induced by Templated Epitaxy for Integrated Heteroepitaxial On-Chip Light Sources

Integrating quantum dot (QD) gain elements onto Si photonic platforms via direct epitaxial growth is the ultimate solution for realizing on-chip light sources. Tremendous improvements in device performance and reliability have been demonstrated in devices grown on planar Si substrates in the last few years. Recently, electrically pumped QD lasers deposited in narrow oxide pockets in a butt-coupled configuration and on-chip coupling have been realized on patterned Si photonic wafers. However, the device yield and reliability, which ultimately determines the scalability of such technology, are limited by material uniformity. Here, detailed analysis is performed, both experimentally and theoretically, on the material asymmetry induced by the pocket geometry and provides unambiguous evidence suggesting that all pockets should be aligned to the [1 $\overline{1}0$] direction of the III-V crystal for high yield, high performance, and scalable on-chip light sources at 300 mm scale.