Dual-shaped Reflector Antenna Research Articles

Design of a Ku-Band Compact Corrugated Horn with High Gaussian Beam Efficiency

The design of a compact corrugated horn operating in Kuband is presented. This horn successfully optimized for high Gaussian beam efficiency and low spillover is manufactured and tested as a feed for an offset dual shaped reflector antenna. The requirements have been satisfied. The sidelobe level is below –30 dB, and the cross-polarization level is below –35 dB over the operating band. All simulation results are confirmed by measurements.

콤팩트 안테나 테스트 레인지용 경면수정 오프셋 복반사경 시스템의 설계

경면수정 오프셋 그레고리안 반사경 안테나는 고이득, 저 사이드로브 특성 때문에 위성 통신 시스템에 널리 사용되고 있다. 그러나 본 논문에서는 CATR(Compact Antenna Test Region)을 위한 반사경 시스템으로 설계하고 그 근접 전계 특성을 조사하였다. CATR은 시험 영역에 진폭과 위상 리플이 작고 교차 편파가 낮은 균일 평면파를 제공하여야 한다. 따라서 근접 전계를 개구면의 전력 분포, 급전 혼의 복사 패턴, 개구면과 시험 영역까지의 거리 변화에 따라 계산하여 나타냈다. 또한, 30 GHz에서 동작하는 경면수정 오프셋 복반사경을 제작하고 근접전계를 측정하였다. 그 결과, 측정치와 계산치가 비슷하게 나타났다. 이로서 본 논문에서 설계된 경면수정 오프셋 복반사경은 콤팩트 안테나 테스트 레인지로 사용될 수 있을 것으로 생각된다. Gregorian offset dual-shaped reflector antennas have been widely used in the satellite communication systems for their high gain and low sidelobe characteristics. However, in this paper, it is designed as the CATR(Compact Antenna Test Range) reflector system, and its near-field characteristics are investigated. The CATR facility needs to provide an uniform plane wave with the minimum amplitude and phase ripple and the low cross polarization to the test region. Therefore, the reflector near-field patterns are calculated and presented with the variations of the aperture power distribution, the feed horn pattern, and the distance from the aperture to the test zone. Also, the offset dual-shaped reflector is fabricated at 30 GHz, and its near-field patterns are measured. The measured results are in good agreement with the calculated results. From theses results, we confirm that the designed offset dual-shaped reflector can be used as the reflector system for the compact antenna test range.

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.

An omnidirectional dual-shaped reflector antenna

A dual-shaped reflector antenna with an omnidirectional pattern and vertical polarization is presented. A radial-mode conical feed illuminates a rotationally symmetric dual-shaped reflector system able to drive the main beam in a nearly horizontal direction and able to control both the main lobe direction and its pattern. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 27: 371–374, 2000.

Improvement of sidelobe characteristics of an offset dual reflector antenna with an elliptical beam

After we manufactured an offset dual-shaped reflector antenna with an elliptical beam designed by the geometrical optics approach, we found that the antenna could not provide the desired low sidelobe characteristics. In general, we often encounter the case in which the desired sidelobe characteristics are not attained because of design inaccuracy, reflector surface error, and reflector alignment error after antenna manufacturing. We here propose a newly developed method, called aperture phase distribution control by adjustment of reflector segments (APCAR). This method has been verified through improvement of sidelobe characteristics of the offset dual-shaped reflector antenna with an elliptical beam, whose aperture diameter is 1.3 m × 2.8 m. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(12): 10–19, 1999

Improvement of sidelobe characteristics of an offset dual reflector antenna with an elliptical beam

After we manufactured an offset dual-shaped reflector antenna with an elliptical beam designed by the geometrical optics approach, we found that the antenna could not provide the desired low sidelobe characteristics. In general, we often encounter the case in which the desired sidelobe characteristics are not attained because of design inaccuracy, reflector surface error, and reflector alignment error after antenna manufacturing. We here propose a newly developed method, called aperture phase distribution control by adjustment of reflector segments (APCAR). This method has been verified through improvement of sidelobe characteristics of the offset dual-shaped reflector antenna with an elliptical beam, whose aperture diameter is 1.3 m × 2.8 m. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(12): 10–19, 1999

Design method for an offset dual-shaped reflector antenna with high efficiency and an elliptical beam

A newly developed method of design for a shaped reflector antenna is described. A conventional quadratic reflector configuration is assumed; the reflectors are then modified to yield the desired aperture shape and field distribution by introducing shaping functions. This method is useful for designing antennas with an arbitrary shaped beam, such as an elliptical-beam antenna, and has been verified through a 4.7 m * 2.3 m (equivalent to 3.3 m diameter) dual-band (30-20 GHz) earth-station antenna for the Japanese domestic satellite system CS. The measured aperture efficiency is more than 76%, and the ratio of the major and minor axes of the elliptical beam is 2:1. >

Design considerations for beamwaveguide in the NASA Deep Space Network

A generalized solution is found for retrofitting a large dual-shaped reflector antenna for a beamwaveguide. The design is termed as a bypass beamwaveguide. Both highpass design feed imaging and bandpass design feed imaging are considered. Each design was studied using geometrical optics, Gaussian wave analysis, and both low-frequency and high-frequency diffraction analysis. An important extension of the Mizusawa-Kitsuregawa criteria was discovered (M.M. Zusama and T. Kitsuregawa, ibid., vol.AP-21, pp.844-8, Nov. 1973). The principle revealed shows how a two-reflector cell, although in itself distorting, may be combined with a second cell which compensates for the first and delivers an output beam which is a good image of the input beam.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Low-loss offset feeds for electrically large symmetric dual-reflector antennas

Circularly symmetric, dual-reflector, high-gain antenna systems often require feeds placed off the system's axis because of the need for multiple feeds to use the reflector antenna. Also, the constraint requiring the hyperboloid or shaped subreflector to remain circularly symmetric is sometimes added. In a Cassegrainian system, the subreflector and feed may be rotated off-axis around the paraboloid focus and retain main reflector focusing. However, substantial spillover results in considerable noise in a high-gain/low-noise temperature system. In a shaped system, the tilt of the shaped subreflector and feed together results in substantial defocusing as well as spillover noise. If the subreflector is tilted approximately one-half the angle of the feed tilt in either the Cassegrainian or the dual-shaped reflector antenna, it is found that spillover and noise are substantially reduced with tolerable defocusing. An extensive numerical analysis of these effects was conducted to determine the characteristics of a 70-meter, dual-shaped reflector versus Cassegrainian antenna and to gain some understanding of the cause of the observed effects.

Synthesis of offset dual shaped subreflector antennas for control of Cassegrain aperture distributions

Many existing large ground reflector antennas have been designed as Cassegrain systems-i.e., paraboloid/hyperboloid combinations. Other large ground antennas are simply paraboloid designs. Upgrading the gain of these systems to a gain comparable to that obtainable with a dual shaped reflector antenna system has been an important and costly objective of many such ground stations. A potentially economic method for such an antenna upgrade is presented herein. It involves a redesign of only the subreflector portion of a Cassegrain antenna or the introduction of a subreflector feed system for a parabaloid. A pair of offset subreflectors are synthesized which will give a controllable high gain amplitude distribution in the aperture of the large paraboloid. The synthesis method that is used is based on an approximate formulation for an offset dual shaped high gain antenna that was first presented by Galindo-Israel and Mittra in 1977. In that approximate formulation, the geometrical optics (GO) energy was scattered from a subreflector and then from a second large reflector which reflected a uniform phase distribution. In the present offset dual shaped subreflector (DSS) antenna, the second reflection is from a smaller (sub) reflector and it scatters a spherical wave that feeds a hyperboloid or feeds a large paraboloid directly. Excellent results are shown for the approximate synthesis of the DSS.