We design a four-reflector offset antenna satisfying the cross-polarization elimination condition and the broadband characteristics condition which consists of one primary horn, three subreflectors and one main reflector. The cross-polarization elimination condition for the four-reflector offset antennas is expressed by the equations of hyperbolas with the coordinate axes of the reciprocal of equivalent focal lengths. The configurations of the reflector system are derived simply from the graphical representation because four-reflector offset antennas satisfying these relationships exist on the hyperbolas with the coordinate axes of the reciprocal of equivalent focal lengths. Furthermore, we clarified that the derived condition for having planar phase front applying the broadband characteristics condition is independent of frequency. An actual design example for the four-reflector offset antennas satisfying the cross-polarization elimination condition and the condition for having planar phase front, both of which are independent of frequency is shown. The design method using the graphical representation is simpler than that of the tri-reflector offset antennas.

To realize S-band mobile satellite communications and broadcasting systems, the onboard mission system and equipment were designed for the Japanese Engineering Test Satellite VIII. The system performs voice communications using handheld terminals, high-speed data communications, and multimedia broadcasting through a geostationary satellite. To enhance system efficiency and flexibility, the onboard mission system features phased-array-fed reflector antennas with large antenna diameter and baseband switching through onboard processors. Configurations and performance of the subsystems and key onboard equipment, large deployable reflectors, feed arrays, beam forming networks and onboard processors, are presented. The S-band mobile systems and onboard equipment will be verified through in-orbit experiments scheduled for 2002.

The growth mechanisms of three-dimensionally (3D) faceted InGaN quantum wells (QWs) on (=1=12=2) GaN substrates are discussed. The structure is composed of (=1=12=2), {=110=1}, and {=1100} planes, and the cross sectional shape is similar to that of 3D QWs on (0001). However, the 3D QWs on (=1=12=2) and (0001) show quite different inter-facet variation of In compositions. To clarify this observation, the local thicknesses of constituent InN and GaN on the 3D GaN are fitted with a formula derived from the diffusion equation. It is suggested that the difference in the In incorporation efficiency of each crystallographic plane strongly affects the surface In adatom migration.