The authors describe the experimental systems for fixed and mobile satellite communications in the ETS-VI (Engineering Test Satellite VI) program. The objectives of the experiments are space confirmation of the onboard equipment performance necessary for multibeam system implementation and function and performance evaluation of the total system including satellite and earth stations. The multibeam system uses three frequency bands: Ka-band (30/20 GHz), C-band (6/4 GHz), and S-band (2.6/2.5 GHz). A number of new techniques have been applied to enhance the multibeam and satellite switch advantages, including satellite-switch time division multiple access incorporated with demand assigned satellite switch operation, cross-band interconnection associated with cross-band diversity, single-beam/multibeam system interconnection, and band-selective switching. A new multibeam system, called the dynamic channel assigned multibeam satellite system, proposed for the mobile communications system to enhance traffic flexibility, is described. >

http://ieeexplore.ieee.org/iel5/799/1834/00049945.pdf

Experimental fixed and mobile multibeam satellite communications system

The configuration, on-ground tests, and design verification results for the multibeam antenna flight model for Engineering Test Satellite-VI (ETS-VI) are described for onboard multibeam antennas with thirteen and five beams for the Ka- and S-bands, respectively. The antennas feature Ka-band frequency reuse in alternate beams through use of a cluster horn; shared use of a reflector for two frequency bands using a novel frequency selective surface (FSS); large, lightweight deployable main reflectors with diameters of 3.5 m and 2.5 m; and a highly accurate antenna-pointing control system consisting of RF sensors and an antenna-pointing mechanism to drive the subreflector. >

On-board multibeam deployable antennas using Ka, C, andS frequency bands

Design of an on-board antenna pointing control system for communication satellites

This paper clarifies the radiation characteristics of a tension truss-type deployable antenna based on measurements made on its solid model and presents its experimental method. The main reflector of the model antenna is constructed by many triangular plates approximating a paraboloid. As the aperture shape of a tension truss-type deployable antenna is a hexagon, the difference between the circular aperture of the model antenna and the hexagon is covered with radiowave absorbers. The distribution of mechanical reflector errors which are projected on the aperture plane is formulated and their relations to electrical errors is shown. Data on reduction of gain and grating lobes in the radiation pattern arising from periodic reflector errors are obtained. The measured results are compared with calculated values of radiation characteristics and good agreement is obtained. It is shown that radiation characteristics can be estimated by the aperture integration method by neglecting the disturbance of current distribution at seams of facets.

Investigation of radiation characteristics of large deployable antennas using a model antenna

In most of the deployable antennas to be placed on board a satellite, the main reflector is made of planar facets or ruled surfaces Therefore, an anomaly can be expected in the electric field distribution on the aperture in comparison with the smooth reflector This paper presents the near-field measurement method, relevant problems, and measurement results for a polyhedron approximated antenna with a reflector made of planar facets The near-field measurement system is of a polarplane scanning type, and the two polar components of the electric field can be measured simultaneously With this system, the near-field of the polyhedron approximated antenna is measured It is experimentally shown that the amplitude is maximum at the junction of the facets; thus, the validity of the previously reported theoretical analysis is proven Although the near-field distribution depends on the measurement plane, the results of the transform of such a distribution to the far-field by the aperture distribution method are identical regardless of the measurement plane Further, reduction of the near-field measurement points is discussed In the case of the present antenna, it is shown to be necessary to use 30 points and 36 points, respectively, of the number of measurement points in the radial and circumferential directions with the measurement scan range at the circumscribing circle of the hexagonal aperture, if the far-field paraxial radiation characteristics obtained are accurate to within 1 dB

Application of a near-field measurement to the characteristics verification of a polyhedron approximated antenna

On-board Ka-band multibeam antenna system with high pointing accuracy for ETS-VI

Structure of deployable satellite antennas.

Ka, C, S frequency bands, multi-beam deployable antenna system for large-capacity communication satellite

On-board antennas of 2.5/3.5 m in diameter which cover Japan with 13 beams in 30/20 GHz bands are developed. To achieve intense frequency reuse, a 9-horn cluster feed is adopted. A tower mounted type deployable antenna configuration is selected so as to overcome the fairing envelope limitation

On-board K-band multibeam antenna configuration with low sidelobes and low crosspolarisation

The authors describe the function of the ETS-VI (Engineering Test Satellite-VI) spacecraft and give a brief description of the onboard antennas and the problems associated with antenna integration. The configuration of the fixed and mobile communication antenna system is shown. The deployed configuration of the structural model antenna consists of tower, main and subreflectors for 20/S and 30/C, Ka-band cluster horns for 20 and 30 GHz, frequency selective surfaces for 20/S and 30/C, a C-band horn, an S-band horn, and an antenna pointing mechanism for each subreflector. The accurate integration of the antenna components to the fixed points of the tower is discussed. >

I. Ohtomo

Papers

On-board Ka-band multibeam antenna system with high pointing accuracy for ETS-VI

Structure of deployable satellite antennas.

Ka, C, S frequency bands, multi-beam deployable antenna system for large-capacity communication satellite

On-board K-band multibeam antenna configuration with low sidelobes and low crosspolarisation

Fixed/mobile multi-beam communication antenna for ETS-VI satellite