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Slotted-waveguide array antennas are attractive because of their low-loss characteristics in high frequencies. Several types of slotted arrays whose polarization angles are inclined to the waveguide axis have been reported. In this paper, we propose a new type of slot array antennas on a rectangular coaxial line for minimizing the waveguide width. As opposed to a conventional waveguide, there is no...
Millimeter wave imaging diagnostics such as electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR) are advanced technology to investigate electron temperature/density profiles and their fluctuations in magnetically confined plasmas. We have installed an ECEI system in the large helical device (LHD) at National Institute for Fusion Science (NIFS). The optimization of a...
This paper presents two types of millimeter-wave waveguide-type array antennas using low-loss engineering plastics. The first one is a cyclo-olefin polymer (COP) waveguide horn array antenna which is fabricated by the injection molding process. The other is a post-wall slotted waveguide array antenna with an offset directional beam using a post-wall rectangular waveguide inside a grafted olefin-styrene...
In this paper, we propose a new type of a small spiral antenna that has a pair of resistors and verify its ultra- wideband characteristics. Spiral antennas have ultra-wideband characteristics such as a nearly constant input impedance, antenna gain, and low axial ratio. However, when reflectors such as conducting planes or cavities are used, their performances are degraded due to reflections from the...
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