Izuru Naito

ULTRA-LOW PROFILE AIRBORNE REFLECTOR ANTENNA SUBSYSTEM FOR BROADBAND SATELLITE COMMUNICATIONS

An ultra-low profile airborne reflector antenna with an arbitrary polarization feed system and a wide-range scanning faculty has been proposed for the broadband satellite communication use. We have chosen a shaped elliptical dual reflector antenna with reflector shaping technique to realize both the ultra-low profile and high electric performances. A novel thin-type broadband OMT with pyramid-loaded waveguide turnstile junction has been presented to obtain the arbitrary polarization thin feed system.

Design Method for a Low-Profile Dual-Shaped Reflector Antenna with an Elliptical Aperture by the Suppression of Undesired Scattering

A design method is proposed for a low-profile dual-shaped reflector antenna for the mobile satellite communications. The antenna is required to be low-profile because of mount restrictions. However, reduction of its height generally causes degradation of antenna performance. Firstly, an initial low-profile reflector antenna with an elliptical aperture is designed by using Geometrical Optics (GO) shaping. Then a Physical Optics (PO) shaping technique is applied to optimize the gain and sidelobes including mitigation of undesired scattering. The developed design method provides highly accurate design procedure for electrically small reflector antennas. Fabrication and measurement of a prototype antenna support the theory.

DEVELOPMENT OF DUAL GRIDDED REFLECTOR ANTENNA FOR SUPERBIRD-C

Satellite communication antenna is required high EOC (Edge of Coverage) gain and XPD ( Cross polarization discrimination ) performance. Dual gridded reflector antenna is suitable to achieve these requirements because gridded reflector antenna has excellent cross polarization supperssion characteristics.[1][2] This antennaconsists of two single reflectors and two feed horns, which are one for transmit and another for receive, horn support structure and feed waveguides. MELCO developped the dual gridded reflector antenna for communication satellites in Ku-band. This paper describes the design concept, design method and measurement result.

A patterning method of polarization grids on a reflector using reflector surface developing technique

This article proposes a patterning method of polarization grids on a reflector using reflector surface developing technique for gridded reflector antennas. Gridded reflector antennas have excellent cross-polarization suppression characteristics caused by their polarization grids on a reflector. The proposed grid patterning method is simple to transcribe a plane grid pattern onto a curved reflector surface, being different from conventional complicated methods such as a direct photoetching method by N/C-driven laser system. A key technology for plane pattern design to obtain a desired pattern on a curved reflector surface is described. The method is evaluated through appropriate models and is verified by a measured radiation pattern.

Numerical calculation and experimental validation of RCS analysis for radome-enclosed scatterer by using PMCHWT-formulation

This paper investigates the accuracy of RCS analysis for radome-enclosed scatterer by using the PMCHWT-formulation. The analysis method based on a surface integral equation known as the PMCHWT-formulation is outlined shortly. We show that calculated scattering cross section patterns of a dielectric coated conducting sphere agree with exact solutions. Then a RCS pattern of an acrylic hemisphere covered conducting disk is compared with measurement result. Calculated RCS patterns of ellipsoidal radome-enclosed scatterer are also presented. We verify the method of moments using the PMCHWT-formulation is sufficiently accurate for RCS analysis of radome-enclosed scatterer.

An analysis of broadband corrugated conical horn antennas taking account of space harmonics due to mode converters

Since the mode converter in a corrugated conical horn antenna consists of a nonperiodic structure in which the depth or the width of the corrugated groove changes gradually, unwanted higher order modes can be generated in the case of oversizing. In this paper, non-periodic structure of this type is modeled as a multiple connection of uniform corrugated waveguides. Space harmonics are taken into consideration under the assumption that the number of stages of the corrugated grooves is not too small. A normalization condition for the corrugated mode function is proposed such that the average transmitted power in one period of the corrugated waveguide in a cylindrical region is unity. By means of the mode matching method, the scattering matrix corresponding to these mode functions is derived. Using this process, the scattering matrices are cascaded for each period of the corrugation and the scattering matrix and the radiation pattern for a corrugated conical horn antenna can be obtained. When the measured and computed values of the radiation pattern of the broadband corrugated conical horn antenna are compared, we confirm that agreement is excellent for both the principal polarization and the cross polarization components. From the amplitude and phase of the measured radiation pattern, the amount of unwanted higher order modes generated (in both amplitude and phase) is estimated and the validity of the method is verified by comparison with computed values.