Atsushi Kezuka

Roles of matching layers for a shaped beam lens horn antenna

A radio collision avoidance system that is used at a crossing is now developing in the intelligent transport systems (ITS). For transponder antennas of this system, a lens horn antenna that can achieve a cosecant squared beam in a vertical plane and a wide beam in a horizontal plane was developed. There, necessity of matching layers was pointed out. In this paper, roles of matching layers are shown through numerical and experimental results. Electrical field disturbance in the horn is cleared by using FDTD analysis. Realization of shaped beam characteristics is shown through numerical and experimental result.

Antennas with cosecant square radiation pattern both upward and downward for FWA

In this paper, antenna with cosecant square radiation pattern both upward and downward is proposed for FWA base station antenna. The single reflector antenna design using geometrical optics is also described. The validity of the design method is confirmed by physical optics.

Phase correction method for GO designed dielectric lens horn antenna

In order to achieve omni-directional coverages on base station antennas for fixed wireless access systems (FWA), a TM 01 mode conical hom with 4.6A aperture size was employed as a feed hom for an axisymmetrical reflector antenna. Here, a shaped dielectric lens was inserted in the conical horn so as to achieve low sidelobe radiation characteristics. However, it was pointed out that radiation pattern shaping ability was degraded in this small lens antenna. In this paper, deteriorations of aperture distributions in a shaped lens are clarified through FDTD calculations. Severe phase delays are shown in the aperture phase distributions. A novel lens shaping method of compensating the phase delays is developed. Aperture distributions and radiation patterns of the corrected lens are estimated through FDTD calculations. Satisfactory uniform phase distributions in aperture distributions and low sidelobe radiation patterns are ensured.

Synthesis approach for electrically small Cassegrain antenna

A synthesis approach of electrically small Cassegrain antenna with dielectric supported sub-reflector is presented. In this approach, feed system is designed to realize ideal far field pattern. Full-wave analysis software is used for this simulation. The main-reflector is shaped to compensate feed system phase shift. Calculating the far field pattern of whole Cassegrain antenna by PO, we confirm the validity of the curvature shaping main-reflector.

Dual Polarized Characteristics of a Shaped Reflector Antenna with Omni-Directional Coverage

The dual polarized characteristics of shaped reflector antennas with omni-directional coverage were examined. Target radiation patterns for vertical and horizontal polarizations were achieved by using a common reflector

Achievement of low sidelobe characteristics in a TM/sub 01/ mode lens horn antenna

In order to achieve low sidelobe characteristics in a dielectric lens inserted TM/sub 01/ mode horn, a shaping method of a dielectric lens has been developed by the authors previously. An antenna is fabricated in order to examine realizability experimentally. Achievement of excellent matching layers are shown to be important. As a result, measured radiation patterns that agree with the calculated patterns are obtained. Moreover, very small frequency dependencies are ensured. Sidelobe levels of -27dB are achieved by the fabricated antenna.