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위성측위 신호 수신을 위한 다중대역 원편파 안테나 설계
홍상석 ( Sang Seok Hong ),안병철 ( Bierng Chearl Ahn ) 충북대학교 산업과학기술연구소 2015 산업과학기술연구 논문집 Vol.29 No.1
This paper presents a multi-band circularly-polarized antenna for receiving GNSS signals at the Chinese BDS B3 band(1268.52±10MHz), the US GPS L1 band (1575.42±10MHz) and the Russian GLONASS L1 band (1602±8MHz). The proposed antenna consists of a two-layer substrate having two slotted circular patches, two coaxial probes. Slot widths are adjusted for good axial ratio and reflection coefficient at each band. The optimally designed antenna has a reflection coefficient of less than -10dB over 1240-1291MHz and 1518-1630MHz, an axial ratio of less than 5dB at 1268MHz and 1575MHz.
홍예선,김상석,김대현,김상범,박상준,최관호,Hong, Yeh-Sun,Kim, Sang-Seok,Kim, Dae-Hyun,Kim, Sang-Beom,Park, Sang-Joon,Choi, Kwan-Ho 항공우주시스템공학회 2014 항공우주시스템공학회지 Vol.8 No.1
The conventional hydraulic circuits for electro-hydrostatic actuators equipped with a single-rod cylinder can oscillate under overrunning load conditions. In this paper the oscillation problem encountered in the conventional hydraulic circuits for EHAs is analyzed and it is shown by simulation results that this problem can be solved by employing a counter balance valve instead of a pilot-operated check valve generally used in the conventional hydraulic circuits.