Terms Of Power Handling Research Articles

Oversized Substrate-Integrated Waveguide for High-Power Millimeter-Wave Systems

In this article, the oversized substrate-integrated waveguide (OS-SIW) is proposed, analyzed, and experimentally demonstrated. The physical parameters and the effect of material surface roughness on the attenuation and the SIW power capability lead to the exploitation of wider and thicker waveguides, as an alternative to enhance the power-handling capability (PHC) and reduce the losses. The resulting oversized waveguide is a guide whose width or thickness is greater than that of the SIW, which is sized to support only the TE10 mode in the operating band. An SIW-to-OS-SIW transition has been designed to allow the component characterization in the W-band. The proposed transition allows to propagate only the desired mode TE10 in the OS-SIW and prevent the higher mode propagation. The experimental results of the manufactured prototypes accord well with the simulations in terms of power handling and transmission losses. The proposed OS-SIW line shows lower attenuation (1.5 Np/m) than a standard SIW (3 Np/m) or a microstrip line (about 3.7 Np/m). However, the OS-SIW 5a has achieved an average power of 90 W at 90 GHz. The investigated OS-SIW configuration offers high PHC, low losses, and easy integration into high-power millimeter-wave systems.

RF Power-Handling Performance for Direct Actuation of Germanium Telluride Switches

The study presented in this article concerns germanium telluride (GeTe) phase-change material-based switches, actuated via direct heating and arranged through two configurations: series or shunt. It is concluded that direct heating provides a performing solution for GeTe amorphization, preventing heater aging. The two configurations are compared in terms of RF performance, power handling, and linearity. Some design rules are derived from empirical data, consolidated with thermal simulations. In either configuration, a large, thick, and short GeTe switch geometry is preferable. Higher isolation can be obtained in shunt configuration, while lower insertion loss can be reached in a series configuration. The Figure-of-Merit, as cutoff frequency, is 11 and 21 THz for shunt and series configurations, respectively. In terms of power handling, for amorphous GeTe, results confirm the existence of a threshold voltage leading to better handling for longer switches in both configurations. For crystalline GeTe, design rules that link the maximum current through the switch before failure to the material geometry are derived for the very first time. It is shown that current is proportional to the GeTe switch width, to the square root of its thickness, and inversely proportional to its length. The shunt configuration presented here holds 31 dBm at ON-state and more than 35 dBm at OFF-state while the series configuration holds 27 dBm at ON-state and 32 dBm at OFF-state. For power handling, a balance exists between series and shunt configurations with a ratio of 4 in the crystalline phase and of 0.25 in the amorphous phase.

(Invited) The Current Status and Future Prospects of SiC Devices

Although silicon power devices have served well as the key technology for power electronics for several decades, silicon-based technology is reaching its physical limits, in terms of power handling and switching frequency capabilities. Thanks to its superior material properties, SiC is the most promising post-silicon alternative for high voltage, high frequency, and high temperature power conversion applications. Since the advent of the first SiC Schottky Barrier Diode (SBD) in the 1990’s, numerous research groups have devoted their efforts to commercialize SiC devices such as MOSFETs, JFETs, and Thyristors. In this talk, issues regarding current SiC devices and processing technology will be identified and future research directions will be discussed.

Silicon carbide: A unique platform for metal-oxide-semiconductor physics

A sustainable energy future requires power electronics that can enable significantly higher efficiencies in the generation, distribution, and usage of electrical energy. Silicon carbide (4H-SiC) is one of the most technologically advanced wide bandgap semiconductor that can outperform conventional silicon in terms of power handling, maximum operating temperature, and power conversion efficiency in power modules. While SiC Schottky diode is a mature technology, SiC power Metal Oxide Semiconductor Field Effect Transistors are relatively novel and there is large room for performance improvement. Specifically, major initiatives are under way to improve the inversion channel mobility and gate oxide stability in order to further reduce the on-resistance and enhance the gate reliability. Both problems relate to the defects near the SiO2/SiC interface, which have been the focus of intensive studies for more than a decade. Here we review research on the SiC MOS physics and technology, including its brief history, the state-of-art, and the latest progress in this field. We focus on the two main scientific problems, namely, low channel mobility and bias temperature instability. The possible mechanisms behind these issues are discussed at the device physics level as well as the atomic scale, with the support of published physical analysis and theoretical studies results. Some of the most exciting recent progress in interface engineering for improving the channel mobility and fundamental understanding of channel transport is reviewed.

Advances in Lower Hybrid Current Drive for Tokamak Long Pulse Operation: Technology and Physics

The paper gives a picture of the present status and understanding of technology and physics of Lower Hybrid Current Drive for long pulse operation in tokamaks, including the development of continuous wave (CW) high power klystrons, and its evolutions towards ITER. 3.7 GH / 700 kW CW klystrons produced in series by Thales Electron Devices are now in operation on Tore Supra. First series of eight klystrons delivered more than 4 MW to sustain non-inductive plasmas during 50 s. Moreover, a prototype of 500 kW CW klystron operating at 5 GHz developed for KSTAR by Toshiba Electron Tubes and Devices, and foreseen for ITER, is able to produce RF output powers of 300 kW / 800 s and 450 kW / 20 s on matched load. The situation on wave coupling and antennas is reported, with the latest Tore Supra results of the new CW Passive-Active Multi-junction (PAM) launcher: the antenna concept foreseen for ITER. First experiments with the PAM antenna in Tore Supra have provided extremely encouraging results in terms of power handling and coupling. Relevant ITER power density of ∼25 MW/m 2 (2.7 MW of power injected into the plasma) has been maintained over ∼80 s. In addition, LH power of 2.7 MW has been coupled at a plasma-antenna distance of 10 cm.