Hongrui Jiang

Novel TWT interaction circuits for high frequency applications

Summary form only given. The initial focus of this program is on the development of Ka-band TWTs producing 10 W of RF power. These devices would potentially be used as RF sources for phased array antennas. This requires innovative TWT designs, which result in improved repeatability, increased yield and reliability, and reduced cost over existing Ka-band devices. To do this, the batch nature of micro-electro-mechanical systems (MEMS) fabrication techniques is ideal. However, many TWT interaction circuits, such as the conventional helix, are not compatible with MEMS techniques. Thus, Calabazas Creek Research, Inc. (CCR) has computationally investigated several innovative TWT interaction circuits based on MEMS fabrication. These include the square helix, planar helix and modified folded waveguide circuits.

A selectively metallized, microfabricated W-band meander line TWT circuit

The development of a selective metallization process capable of metallizing only the top of a microfabricated, raised meander line ridge is described. This fabrication process has unique potential in the development of millimetre-wave and terahertz regime slow wave structures for travelling wave tubes. The fabrication process will be described and the latest images and measured data will be presented.

Overview of W-Band Traveling Wave Tube Programs

Two research programs are in progress to develop W-band traveling wave tubes (TWTs). One uses a folded waveguide (fwg) slow-wave circuit and the other uses a novel, planar meander line circuit. Both devices are currently being assembled. The predicted performance, fabrication methods and challenges, and measured data to date were presented

Microfabricated W-band traveling wave tubes

Two research programs are in progress to develop W-band travelling wave tubes (TWTs). One uses a folded waveguide (fwg) slow-wave circuit, and the other uses a novel, planar meander line circuit. Both devices are currently being assembled. The predicted performance, fabrication methods and challenges, and measured data to date will be presented.

W-band MEMS-based TWT development

Summary form only given. Calabazas Creek Research, Inc. is funded by the U.S. Air Force to develop advanced, wideband, high frequency, micro-electro-mechanical systems (MEMS)-based traveling wave tubes (TWTs) for the transformational communications architecture. Specifically, the program is developing an 83.5 GHz TWT. Full power testing of the TWT in a solenoid magnetic field by Boeing Satellite System, Inc. is planned in 2004. Following successful completion, PPM focusing will be implemented and development of a device for space qualification will begin. The program is scheduled for completion in April 2005. Successful completion of this program will increase the operating range and applications for vacuum-based RF devices.

Micromachined step-tapered high frequency waveguide inserts and antennas

Applications of high frequency radiation, in the ranges of 30-300 GHz (millimeter-wave) and 300-1000 GHz (terahertz), require the development of specialized components, specifically low-loss waveguides and antennas. Conventional waveguide antennas must be flared in both lateral dimensions requiring a large space and are challenging to fabricate. Previous work has shown the promise of tapered dielectric rod antennas for their high transmission and ease of integration into waveguide systems. However, practical repeatable machining techniques are neglected. This work develops the design, manufacturing, and analysis of step-tapered waveguide inserts and antennas, fabricated via controlled acid etching of high resistivity silicon, optimized for good transmission in the range of 75-110 GHz.

MEMS-microfabricated components for millimeter-wave and THz TWTs

Summary form only given. Microfabrication techniques used for MEMS offer promising advantages for fabrication of mm-wave and THz vacuum electronic devices (/spl mu/VEDs). This paper describes results of an exploratory investigation of several microfabrication methods considered candidates for production of circuits or circuit components for mm-wave and THz TWTs. The processes investigated have included LIGA, hot embossing (polymer micromolding), and deep reactive ion etching (DRIE). The circuits and circuit components investigated have included folded waveguides (FWGs), gratings, resistive wall amplifiers, and novel attenuators for FWG TWTs. We present and discuss the results of the microfabrication experiments, the design analyses, and their implications for advanced mm-wave and THz /spl mu/VEDs.

Generation of Terahertz Regime Radiation by Microfabricated Folded Waveguide Traveling Wave Tubes

The fabrication of a terahertz regime folded waveguide traveling wave tube (FWTWT) using MEMS microfabrication techniques is currently underway. Recent developments in the design, fabrication method, and measured data are presented

Selective Metallization for a W-band Meander Line TWT

The development of terahertz (THz) millimetre-wave (MMW) regime vacuum electronics necessitates the concurrent development of adequate fabrication techniques. Since the size of vacuum electronic devices is proportional to their frequency of operation, fabricating them for the THz and mmw regimes requires fabrication techniques capable of producing millimeter and micron-scale features. Monolithic microfabrication technologies such as deep reactive ion etching (DRIE) have been used widely in the MEMS community for years to achieve these sorts of feature sizes.

Microfabricated THz-regime Waveguides

Summary form only given. Vacuum electronic sources of THz regime (0.1-10 THz) radiation will require advanced methods to precisely fabricate miniature waveguides. We are exploring the design and fabrication of THz-regime waveguides using bulk silicon-based microfabrication, specifically, deep reactive ion etching. Due to the waveguides dimensions it is advantageous to fabricate it in halves on two separate silicon wafers. Final assembly consists of metallizing the halves and thermocompressively bonding them together. Finding an appropriate diffusion barrier and bonding technique is vital to the success of this design and has recently been our primary focus. Along with the development of THz-regime waveguides, we are exploring a novel coupling technique that consists of a tapered silicon tip, made by wet chemical etching. These silicon tips, fabricated from square silicon rods approximately the size of the waveguide, can be fabricated with a tolerance of less than one micron by monitoring the electrolytic current in the etchant bath and controlling the submersion depth of the silicon rod via robotic controls. In conjunction with the development of the waveguides and couplers, we are also investigating how THz regime radiation interacts with metallic thin films. We are developing computational models to predict effective RF conductivity of metallic thin films at THz frequencies, including the effects of surface roughness scattering at the interfaces. Experimentally, our micro fabricated THz-regime waveguides provide us with an excellent platform for validating the model. By measuring the throughput power for different lengths of waveguide, we can determine the ohmic loss per unit length. This presentation will discuss the latest developments in all of these research efforts namely the fabrication of THz regime waveguides, coupling techniques and our investigation into electron transport in metallic thin films at THz frequencies.