A Linear Array Antenna Using Bifilar Helical Elements for Mobile Satellite Communications

Masataka OHTSUKA  Yoshihiko KONISHI  Makoto MATSUNAGA  Takashi KATAGI  

IEICE TRANSACTIONS on Electronics   Vol.E79-C   No.5   pp.699-704
Publication Date: 1996/05/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Microwave Devices for Mobile Communications)
Category: Passive Devices
mobile satellite communication,  beam direction movement,  bifilar helical antenna,  TEM transmission line,  array antenna,  microwave and millimeter wave technology,  

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In this paper, authors propose a linear array antenna using two bifilar helical antenna elements placed along the helix axis to reduce beam direction movement according to frequency change. The beam direction movement of this proposed array antenna is smaller than that of a conventional bifilar helical antenna. Also, the gain of this proposed array antenna is higher than that of the conventional helical antenna for a cross point angle of radiation patterns at the different transmit and receive(Tx and Rx) frequencies. The conventional helical antenna is suitable for vehicle antennas in mobile satellite communication systems such as the MSAT system because it owns circularly polarized omni-directional radiation pattern and its thin pole form. However, this antenna has a disadvantage that the beam direction in an elevation plane moves according to frequency change. In the proposed array antenna, the beam direction movement is about 9 smaller than that of the conventional bifilar helical antenna on condition that antenna total length is 4.83 λ0, antenna diameter is 0.12 λ0, and frequency change is from 0.957f0 to 1.043f0(f0 is center frequency and λ0 is free space wavelength at f0). Also, the Tx and Rx gains of this proposed array antenna at the cross point angle between Tx and Rx beams are about 2 dB higher than that of the conventional bifilar helical antenna on the same condition.