For future direct broadcasting satellites in Japan, precisely contoured beam antennas will be required for onboard antennas. Single shaped-reflector antennas are suitable for that purpose, since they do not need complex feed networks. However, in a previous study, discontinuities in the reflector surface were observed. The problem of the discontinuity was circumvented in this work and the shaped reflectors were successfully designed to produce contoured beams for covering the Japanese islands for the downlink and feederlink antennas. The downlink antenna was fabricated, and the radiation pattern was verified by measurement. The radiation pattern meets the radio regulations imposed on the onboard antenna, such as sidelobe and cross-polarization characteristics. >

Single shaped reflector antennas for broadcasting satellites

Previously, the authors have proposed a design method of a shaped dual-reflector contoured-beam antenna with virtual multihorns with a view to applications to the broadcast satellite BS-3. In such a design, there were discontinuities on the main reflector.



In this paper, a method for eliminating these step discontinuities is studied for the dual-reflectors. The current distribution on the main reflector corresponding to the desired radiation pattern is determined by optimization depending on the constraint gain of the far field. Note that the optimization method for the aperture phase distribution was known for a single smoothly shaped contoured-beam antenna. Also, in this paper, an optimization method for the amplitude distribution is proposed anew. Further, by adding a restriction to the phase difference between the adjacent elements in the optimization of the phase distribution, the step discontinuity on the reflector is eliminated. By means of this method, an antenna made of a main reflector with an aperture diameter of 2.3 m is designed at 12 GHz which is the frequency of the downlink of the broadcast satellite.



Most of Hokkaido, Honshu, Shikoku, Kyushu, and Okinawa is covered by a radiation pattern with more than 40 dBi and other remote islands with more than 28 dBi. A one-half scale model is fabricated and the radiation pattern is measured at 22 GHz. The results agree well with the numerical results. Also, the sidelobe and the cross-polarization characteristics of this antenna sufficiently satisfy the technical standards in RR.AP 30.

Contoured‐beam antenna using smoothly shaped dual‐reflectors for broadcasting satellites

A precisely shaped contoured beam antenna has been designed in the downlink frequency band (12 GHz) for future direct broadcasting satellites in Japan. The antenna consists of a single offset shaped reflector and a single feed horn. The single offset shaped reflector antenna was shown to radiate a contoured beam which covered the major part of the Japanese territory at over 40 dBi and other remote islands at over 28 dBi. The calculated radiation pattern was verified by measurement. >

A contoured beam shaped reflector antenna for broadcasting satellites

放送衛星3号 (BS-3) は, 昭和65年度にBS-3aを, 昭和66年度にBS-3bをH1ロケットにより打上げることを目標に開発が進められている.BS-3の放送用アンテナは, 沖縄地方の利得向上, 低サイドローブ化などBS-2よりも厳しい要求があるが, 楕円開口オフセットパラボラ反射鏡と, 1次放射器として楕円コルゲートホーンおよび短辺にコルゲートを施した長方形ホーンを用いることにより, 要求条件をすべて満たす設計とすることができた.設計の妥当性を確認するために開発モデル (EM) を製作し, 各種試験を実施した.パターン測定の結果, 12GHz帯テレビチャンネルにおいて, 東京39.6dBi以上, 那覇36.8dBi以上, などの利得が得られ設計の妥当性が確認できた.また, 熱歪による利得の変動は0.1～0.3dB程度で, 熱歪時でも要求利得を満たすことが解析により確認できた.

放送衛星3号 (bs-3) 放送用アンテナの電気設計

The antenna for broadcasting satellites succeeding the BS-3 can utilize larger antennas than before and there is a very strong desire to improve the capability of precise beam shaping. To develop an antenna which meets this requirement, the reflector shaping technique has been investigated for a system which consists of two reflectors and one horn, and where reflectors can be shaped to provide easy and precise beam shaping.



To determine the aperture distribution of the main reflector for the desired radiation pattern, imaginary multihorns are used, and the position and power of each horn is adjusted. Then one horn is placed at the feed point and the subreflector is shaped keeping in mind the amplitude distribution given by imaginary multihorns. Afterward, the main reflector is adjusted taking into consideration the phase distribution.



Using this two-step reflector shaping technique, dual-reflector antennas with the main reflector having a diameter of 2.8 m were designed at a frequency of 12 GHz. As a result, a radiation pattern of good shape was obtained which covers all the four main islands of Japan at -2 dB (relative value), Okinawa at -4 dB and Ogasa-wara Islands at -14 dB. To check the validity of this technique, a scale model of approximately one-half size was fabricated and measurements were made at 22.75 GHz. The calculated values are shown to agree with the measured values.

Contoured-beam antenna using shaped offset-fed dual-reflectors for broadcasting satellites

Shuichi Miura Noboru ~oyama t (Satellite Program Department, NASDAI* Kenji Ohmaru Kazuyoshi Shogen (Science and Technical Research Laboratories, NHK)** Tomoki Obuchi Yoshihide Miyata (Space Development Division, NEC Corporation)*** This paper describes the electrical performance of the Shaped-beam antenna for the next phase Japanese broadcasting satellites (BS-3a, BS-3b) with analysis and some typical test results of both a bread board model (BBM) and an engineering one (EM). The BS-3a and BS-3b will be launched as successors of the BS-2 in 1990 and 1991 respectively by H-I launch vehicle. BS-3 antenna employs an elliptical offset parabolic reflector fed with a new type elliptical corrugated horn and a rectangular one. The major and minor axis lengths of the aperture are 1700 mm and 800 mm, which is somewhat smaller than that of the BS-2 antenna. The EM antenna has attained a gain of more than 39 dB for the major part of the Japan Islands, more than 36 dB for Okinawa and more than 28 dB for the remote islands. The sidelobe and crosspolar components radiated outside the service area are verified to satisfy the WARC-BS requirements on the basis of power flux density on the earth assuming 120 W output power of the transponder. It is found that BS-3 EM antevna has an efficiency of more than 70%.

Electrical performance of BS-3 shaped-beam antenna

A study of highly shaped contoured beam antenna for Japanese DBS

This paper describes a study of contoured beam onboard a n t e n n a for f u t u r e Japanese direct broadcasting satellites (DBS) with pattern analysis and test results for the full-scale bread board model (BBM). The BS-3a and BS-3b were launched in 1990 and 1991, respectively, by the HI launch vehicle into a geo-synchronous orbit of 110 degrees east longitude. A follow-on DBS will be launched before the end of the BS-3's life (7 years). As the methods to realize the contoured-beam pattern for Japanese territory, the BS-3 antenna employs an elliptical offset parabolic reflector fed with a new type. \rJ of elliptical corrugated horn as well as a rectanylar horn. Thus, the contoured beam is based on an el ipse, and it is difficult to achieve the best fitting contour patterns for the Japanese territory. The antenna examined herein consists of a shaped reflector and a horn. This shaped reflector antenna has achieved a better shaped radiation pattern than the BS-3, and has attained a gain of more than 38 dBi for the major parts of Japan while, maintaining the RR.AP30* regulations for sidelobe and cross-polarization levels, theoretically and experimentally. In order to verify our shaped reflector antenna characteristic, a BBM antenna with 2.3m aperture was constructed and has shown good agreement with the analytical results. The authors propose this reflector antenna as a candidate for the next Japanese direct broadcasting satellite antenna system.

Tomoki Obuchi

Papers

Electrical performance of BS-3 shaped-beam antenna

A study of highly shaped contoured beam antenna for Japanese DBS

A study of a contoured beam antenna for future Japanese DBS