A study on beam-tilt type planar antenna having high aperture efficiency.

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In construction of a large-scale multi-element planar array, reduction of the feeding loss is important for realization of high-efficiency performance. In reflection of this requirement, much attention is paid to a planar antenna having a loss-suppressed feeding system.This work presents a beam-tilt type planar antenna which excites singly-fed circularly polarized microstrip antenna (CP-MSA) via a low-loss radial waveguide. In order to check the performance of this antenna, some beam-tilt type planar arrays were fabricated and tested at the SHF-band.As a result of experiment, the following results were obtained. The axial ratio of the array was suppressed to below 1.0 dB over a wide range of frequency band. The aperture efficiency eta as determined from the inner diameter of the radial line reached approximately 90% at the SHF-band.On examining the input impedance characteristics, VSWR of a test array was below 1.5 over a broadband region.As mentioned previously, this planar array fed by a radial line demonstrated high-efficiency performance (approximately 90% aperture efficiency). It was conformed that this type of antenna can be useful model of a circularly polarized planar antenna.