This paper describes an onboard antenna for the 21 GHz band variable EIRP (equivalent isotropically radiated power) broadcasting satellite. This frequency band provides a large rain/vapor attenuation. For example, the atmospheric attenuation is about 10 dB for 1% of the time during the worst month in Tokyo. In order to overcome the large attenuation, a multi-beam system is studied, in which each of the beams covers a small area and the radiation power of the beam is controlled according to the atmospheric attenuation of that area. The onboard antenna is one of the key components in this system. We have developed a scale model of the multi-beam antenna. The characteristics of the antenna agree with the designed characteristics.

Radiation characteristics of multi-horn antenna for 21 GHz band variable EIRP broadcasting satellite

Radiation Characteristics of Multi-horn Antenna for 21 GHz Band Variable EIRP Broadcasting Satellite

Simultaneous Optimal Design Method of Primary Radiator and Main Reflector for Shaped Beam Antennas

A satellite broadcasting system for the 21-GHz BSS (broadcasting satellite service) band which has multi-beam variable EIRP (equivalent isotropically radiated power) transponders is studied taking into account compensation for the rain attenuation. First, the relationship between the number of beams and radiation power which is necessary for nationwide coverage in Japan is discussed. The result shows that an employment of a 6-beam variable EIRP system can reduce the necessary output power to a half that of a fixed EIRP system. Second, to study the system feasibility, some key components were manufactured experimentally. We have developed a multi-beam antenna, which consists of a 6horn feed and a single parabolic reflector, and high-power TWTs. To realize the variable EIRP system, a method to control the output power of TWT for achieving maximum efficiency is proposed. By combining two TWTs in parallel, a maximum output of 430 W was obtained with this method.

A study on variable eirp system for the 21 ghz band direct broadcasting satellites

A study on variable EIRP system for 21 GHz global broadcasting satellite

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

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.

Hayato Nishida

Papers

A study on variable EIRP system for 21 GHz global broadcasting satellite

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

A study of a contoured beam antenna for future Japanese DBS