RLSA (radial line slot antenna) is a slotted waveguide array antenna which is proposed for the DBS (direct broadcast by satellite) reception. Theoretically, it has lower conduction loss and higher effectiveness than a planar microstrip antenna. DL-RLSA (double-layered RLSA) uses a radially inward travelling wave for slot excitation in the double-layered radial line. The effectiveness of DL-RLSA is more than 75% (33-37 dBi), which is twice the effectiveness of other planar antennas. In spite of that advantage, SL-RLSA (single-layered RLSA) is more popular because of the complex structure of DL-RLSA. However,the radially outward travelling wave of SL-RLSA gives high tapering when the travelling wave approaches the aperture edge. To remove these troublesome things, an effective feeder structure is proposed in which the diameter of the feeder rod widens towards its end. To find the optimum height and angle of the feeder, the finite-difference time-domain (FDTD) method is employed. The simulation parameter of the FDTD algorithm is the dimension of the feeder. Compared with the effectiveness of the conventional rod feeder structure, that of the proposed feeder structure is enhanced by 5dB.
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