A second electron cyclotron emission imaging (ECEI) system has been installed on the KSTAR tokamak, toroidally separated by 1/16th of the torus from the first ECEI system. For the first time, the dynamical evolutions of MHD instabilities from the plasma core to the edge have been visualized in quasi-3D for a wide range of the KSTAR operation (B0 = 1.7∼3.5 T). This flexible diagnostic capability has been realized by substantial improvements in large-aperture quasi-optical microwave components including the development of broad-band polarization rotators for imaging of the fundamental ordinary ECE as well as the usual 2nd harmonic extraordinary ECE.
A practical double-sided frequency selective surface for millimeter-wave applications Review of Scientific Instruments 89, 024703 (2018) A new high-performing PCB (Printed Circuit Board) dichroic filter, which can be used for the KSTAR (Korea Superconducting Tokamak Advanced Research) electron cyclotron emission imaging system, is proposed. The current dichroic filter consists of a triangular lattice array of circular holes on the 6-mm thick metal plate, while circular hole spacing limitation caused relatively narrow passband (∼20 GHz). On the other hand, the proposed PCB dichroic filter utilizes the inexpensive commercial PCB fabrication process with a flexible adjustment of circular hole spacing. Therefore, the proposed PCB dichroic filter provides significantly wider passband (∼60 GHz with 0.84 dB insertion loss) with much reduced weight and expense. Also, it is shown that a steep skirt property can be obtained with the thick PCB filter substrate. The design process, fabrication, and measurement results of the new PCB dichroic filter are described. Published by AIP Publishing. [http://dx
A Multiple-input multiple-output antenna array with two radiating elements having a wide bandwidth is reported in this work. Spatial diversity has been introduced to achieve the diversity gain and the array was kept compact by introducing five parasitic decoupling elements on the bottom of the substrate; each having a length equal to k/2 at a specific frequency. Each resonant element offers a resonant bandwidth of 1 GHz starting from 3 GHz to 8.5 GHz. Good agreement between the measured and simulated results shows that the antenna system performs very well over the frequency range 3 GHz to 8.5 GHz. In addition, an isolation of more than 15 dB is achieved with the help of the parasitic elements, while keeping an edge-to-edge and center-tocenter separation of 4 mm and 19 mm, respectively. The proposed antenna measures 26 3 40.5 mm 2 , and it is suitable for handheld devices, personal digital assistants, next generation home entertainment systems, and robots.
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