To provide a planar antenna capable of improving a circularly polarized wave characteristic to a wide band characteristic as to a planar antenna having wide band characteristics in sub-microwave bands, microwave bands, sub-millimeter wave bands, millimeter wave bands, etc.
A reflector 13 is arranged oppositely to a conductor plate 12 to constitute a radial waveguide 11, and a feeding connector 14 is attached to the lower central part of the conductor plate 12. Helical antennas 16 consisting of six elements e.g. are arranged concentrically around a feeding pin 15 of the feeding connector 14 on the upper surface of the reflector 13 as circularly polarized wave antennas, and helical feeding pins 17 having the same length are projected into the radial waveguide 11. Circularly polarized wave passive elements 18 are arranged in the upper surface radiation axis direction of the helical antennas 16 with a prescribed interval h (h=n×λ0/2+λ0/10). These circularly polarized wave passive elements 18 are arranged oppositely to respective helical antenna elements 16 at 45°±10° element angle. Since the circularly polarized wave passive elements 18 are arranged on the upper part of the circularly polarized wave antennas with the prescribed interval h, the circularly polarized wave characteristic is brought into a wide band.
Satoshi Kono
Makoto Nakamura
Kurata Masatoshi
Takashi Mine
Yoshihiro Fukuhara
Sadao Muramatsu
Ryo Hashimoto