P. Kalaria

Dual band microstrip patch antenna for wireless applications at 5.2 GHz and 5.8 GHz using CSSRR

This prototype antenna design was targeted for WiMAX applications at 5.2 GHz and 5.8 GHz. Patch antenna size reduction is achieved in this work. To realize a dual band operation for WiMAX application at 5.2 GHz and 5.8 GHZ, ground plane loaded with CSSRR has been proposed. The proposed antenna provides good flexibility on selection of dual frequency operation by modifying dimension of CSSRR and patch. The antenna was designed using CST V.9 simulator.

Systematic cavity design approach for a multi-frequency gyrotron for DEMO and study of its RF behavior

High frequency (>230 GHz) megawatt-class gyrotrons are planned as RF sources for electron cyclotron resonance heating and current drive in DEMOnstration fusion power plants (DEMOs). In this paper, for the first time, a feasibility study of a 236 GHz DEMO gyrotron is presented by considering all relevant design goals and the possible technical limitations. A mode-selection procedure is proposed in order to satisfy the multi-frequency and frequency-step tunability requirements. An effective systematic design approach for the optimal design of a gradually tapered cavity is presented. The RF-behavior of the proposed cavity is verified rigorously, supporting 920 kW of stable output power with an interaction efficiency of 36% including the considerations of realistic beam parameters.

Complementary Sierpinski gasket fractal antenna for dual-band WiMAX/WLAN (3.5/5.8 GHz) applications

A proximity-fed complementary Sierpinski gasket fractal with equilateral triangular shape resonator in multilayer structure to achieve dual-band behavior for WiMAX and WLAN applications has been proposed. An electromagnetic coupled stacked structure of two different patches operating at two frequencies (3.5 GHz WiMAX and 5.8 GHz wireless LAN) has been designed for dual-band wireless applications. Proposed antenna was simulated using CST Microwave Studio based on the finite integration technique (FIT) with perfect boundary approximation (PBA). Finally, the proposed antenna was fabricated and some performance parameters were measured to validate against simulation results. The design procedures and employed tuning techniques to achieve the desired performance are presented.

Multi-frequency operation of DEMO gyrotron with realistic electron beam parameters

Along with high power and high efficiency operation around 240 GHz, the requirements of DEMO gyrotrons include the possibility of multi-frequency operation and fast frequency tunability in 2-3 GHz steps. In this paper, multi-frequency operation of a proposed design for a conventional cavity DEMO gyrotron is presented, including operating parameters at different frequencies. The performance of the gyrotron is simulated considering realistic electron beam parameters.

Design of 170 GHz, 1.5-MW Conventional Cavity Gyrotron for Plasma Heating

In this paper, an overall conceptual design of a 170 GHz, 1.5 MW, continuous wave (CW) conventional cavity gyrotron is presented for plasma heating applications in thermonuclear fusion reactors. The operating mode is carefully selected with due consideration of design constraints/goals and mode competition. The

Interaction circuit design and RF behavior of a 236 GHz gyrotron for DEMO

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RF Behavior and Launcher Design for a Fast Frequency Step-tunable 236 GHz Gyrotron for DEMO

mode is selected as operating mode for the present study. A weakly tapered conventional cavity resonator is considered for the study of the RF-behavior. Single mode and multimode time dependence self-consistence calculations are carried out for power and efficiencies. In addition, the design studies of a triode type magnetic injection gun, magnetic guidance system, output system that consists of an optimized nonlinear taper, a highly efficient dimpled-wall quasi-optical launcher and a single disk Chemical Vapor Deposition diamond window are also reported. Results obtained support an output power of 1.5-MW CW power at 170 GHz with a conventional cavity gyrotron with 35% efficiency without single stage depressed collector. This device is intended to serve as heating source for international thermonuclear experimental reactor- like machines.

Transient response of dual-band-notched ultra-wideband antenna

The Demonstration Fusion Power Reactor (DEMO) to follow ITER by 2050 demands high frequency (>230 GHz), high power (in the range from 1 MW to 2 MW) gyrotrons as RF sources for electron cyclotron resonance heating and current drive (ECRH&CD). In the frame of the EUROfusion programme at KIT, the designs of conventional-cavity type and coaxial-cavity type DEMO-compatible gyrotrons are under investigation. In this presentation, the physical design of the interaction circuit of a 236 GHz conventional cavity gyrotron and its RF behavior are presented. The simulation results show a stable single mode RF output power without serious mode competition.

A fast frequency step-tunable 236 GHz gyrotron design for DEMO

Abstract As part of the EUROfusion project, the conceptual design of a 1 MW 236 GHz hollow-cavity gyrotron is ongoing at IHM, KIT for a DEMOnstration Power Plant (DEMO), along with a 2 MW coaxial-cavity design concept. Fast frequency-tunable gyrotrons (tuning within a few seconds) are recommended for plasma stabilization using a non-steerable antenna. In this work, the mode-selection approach for such a frequency-tunable gyrotron is presented and suitable operating modes for fast frequency tunability are suggested. Magnetic field tuning has been studied as an effective technique to tune the gyrotron operating frequency. The step-tunability of the 236 GHz gyrotron within the frequency range of ±10 GHz in steps of 2–3 GHz is demonstrated in numerical simulations. A hybrid-type Quasi-Optical Launcher (QOL) has been designed for a step-frequency tunable gyrotron with sufficiently high Fundamental Gaussian Mode Content (FGMC).

ELECTRON CYCLOTRON POWER SOURCE SYSTEM FOR ITER

In the present study, an ultra-wideband (UWB) antenna has been proposed using coplanar waveguide (CPW) feed with dual-band-notch characteristics. Slot-loaded radiator and U-shaped CPW resonator are used for band rejection at 3.5 and 5–6 GHz respectively to reduce interference with existing World interoperability for microwave access and wireless local area network systems. With an extended operating band (measured at 10 dB return loss) the antenna operates successfully over the entire UWB range (3.1–10.6 GHz) with a form factor of 30 × 20 × 1.524 mm on a commercially low-cost FR-4 substrate. Experimental measurement results are presented in support of the simulated results for the proposed antenna for practical application. The antenna has been successfully fabricated and measured, showing broadband matched impedance and good omnidirectional radiation pattern throughout the operating bandwidth. Measured time-domain analysis for both the orientations, i.e. face-to-face and side-by-side, yields excellent performance in the open environment scenario. With fairly good and consistent monopole such as omnidirectional radiation patterns in H-plane and linear transmission responses, the proposed antenna is well suited to be integrated within portable devices.