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Axial Ratio and Gain Enhancement of a Circular-Ring Slot Antenna Using a Pair of Asymmetrical Rectangular Slots and a Parasitic Patch for a Radio Beacon on a Nanosatellite

1
Center for Environment Remote Sensing, Chiba University, Chiba 263-8522, Japan
2
Space Science Center, Indonesian National Institute of Aeronautics and Space, Bandung 40173, Indonesia
3
Aeronautic Technology Center, National Institute of Aeronautics and Space, Bogor 16350, Indonesia
4
Department of Informatics, Universitas Pembangunan Jaya, Tangerang Selatan 15413, Indonesia
*
Author to whom correspondence should be addressed.
Aerospace 2019, 6(4), 39; https://doi.org/10.3390/aerospace6040039
Received: 17 January 2019 / Revised: 11 March 2019 / Accepted: 12 March 2019 / Published: 28 March 2019
Radio beacons enable measurements of ionospheric radio scintillations and total electron content (TEC). These beacons transmit unmodulated, phase-coherent waves in S-band frequencies. Many satellite applications require circularly polarized (CP) wideband antennas. Their compact size, lightweight, and simple fabrication method make CP antennas suitable for small satellite systems. The slot antenna has wideband impedance, but the 3 dB axial ratio bandwidth (ARBW) is narrower compared to the impedance bandwidth (IBW). In this paper, a circularly polarized circular-slotted antenna (CSA) is proposed to enhance the ARBW and the antenna gain. A pair of asymmetrical rectangular slots, a simple 50 Ω feedline and a parasitic patch were introduced to a CSA to enhance the 3 dB ARBW and the antenna gain. Rectangular slots were inserted on the diagonal axis of the CSA, the feedline was shifted to the left side of the x-axis, and a parasitic patch was attached to the circular slot. The lengths of the rectangular slots correspond to the resonant frequency, and the parasitic patch width corresponds to the higher frequency of the 3 dB ARBW. The asymmetrical rectangular slots, the shifted feedline, and the parasitic patch successfully improved the measured 3 dB ARBW of the antenna by 787.5 MHz or 35.79%. The measured gain of a CSA with left-hand circular polarization (LHCP) was also improved by shifting the feedline and the rectangular slot, achieving a peak gain of 5 dBic. View Full-Text
Keywords: nanosatellite; microstrip antenna; slot antenna; axial ratio enhancement; circular polarization nanosatellite; microstrip antenna; slot antenna; axial ratio enhancement; circular polarization
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Sitompul, P.P.; Sri Sumantyo, J.T.; Kurniawan, F.; Nasucha, M. Axial Ratio and Gain Enhancement of a Circular-Ring Slot Antenna Using a Pair of Asymmetrical Rectangular Slots and a Parasitic Patch for a Radio Beacon on a Nanosatellite. Aerospace 2019, 6, 39.

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