Site: Space Communications Research Corp. (SCR)
5th Floor, Hayakawa Tonakai Building
Tokyo 101, Japan
Date Visited: October 22, 1992
Report Author: J. Pelton
The Space Communications Research Corporation (SCR) was formed in 1987 after the formation of the Japan Key Technology Center (JKTC) in 1986. (JKTC's activities are funded in part from the Japanese Government's dividends from NTT stock it holds as a result of the privatization of NTT in 1986.) SCR has spent about $40 million since then, an average of about $8 million/year. It has 22 employees, including some on loan from industry sponsors. The philosophy of SCR is to conduct cooperative activities with industry; most hardware developments are joint efforts with qualified aerospace, electronic or telecommunications industry partners. The major companies involved tend to be Toshiba, MELCO, and NEC. There are two other JKTC-initiated companies devoted to space communications technology and applications that were formed at about the same time as SCR. These are the Advanced Telecommunications Research Institute International (ATR) and the Space Communications Laboratories (SCL).
SCR tends to focus on the 10 to 20 year research horizon, which appears to be the normal practice for JKTC. This longer term basic research effort thus does not interfere with shorter term corporate R&D activities.
SCR has first considered three missions for the GPF (Geo-Stationary Platform). Those are LMSS, mm-wave (50/40 GHz) PCS over satellites, and future DBS-TV at 22 GHz. For the LMSS, 30 m class deployable antennas and high power SSPAs, especially at L- and S-band, are to be developed. For mm-wave PCS, also for mobile use, key items are the 40 GHz TWTA, the 50 GHz LNA, and a satellite switching system, including OBP. A 22 GHz HPA is needed for future DBS TV.
The primary focus of antenna work at SCR has been on very large deployable antenna reflectors for mobile applications. The characteristics of this long term design effort are provided below.
Baseband Processor. A 100 x 100 channel baseband OBP and bit-by-bit switching system is being developed with NEC.
HEMT and Super HEMT Devices. The focus is on pseudo-morphic HEMT devices (AlGaAs/GaAs). Fujitsu is doing this work for SCR under contract and is the main developer of this technology in Japan.
SSPAs. An 800 MHz band (UHF) Si MOSFET SSPA with 40 to 51% efficiency and a 2.5 GHz band (S-band) GaAs MESFET SSPA with 33 to 42% efficiency are being developed.
Deployable Mesh Antennas. A high precision, micro-deviation RMS mesh antenna and a 6 m (1/5 of 30 m) Hexalink Truss-type deployable antenna are now being constructed. (See also the main report,Chapter 2, Space and Ground Antennas section, subsection on Related Japanese Space Technology.)
TWTAs. SCR has attained values of over 30 W in power and 30% in efficiency in a 40 GHz high power TWTA developed with NEC for mm-wave PCS. A 22 GHz TWTA developed with Toshiba for DBS has achieved power of over 300 W and 50% efficiency.
The main report contains the most important information, but highlights and key findings are as follows:
Rain Attenuation. SCR is trying to develop techniques to deal with rain attenuation in a manner similar to that planned for ACTS. They are using "power upon demand" for beams during periods of high rainfall. However, this is for BS applications at 22 GHz, thus 3000 meteorological stations will be used to input data and monitor decisions on power levels for each beam. The one-way nature of current broadcast systems does not allow the possibility of changes during the dwell time of a beam.
Multipurpose GEO Space Platform. 30 m reflectors for LMSS operating in L-band and S-band have been the major development objective over these past several years. Some of their technology -- for example, the 1/5 scale models of large deployable mesh antennas, TWTAs at 40 and 22 GHz, and the super HEMT at 50 GHz -- are truly outstanding and world class. An orbital transfer vehicle (OTV) would need to be developed to support such missions; however, this has not yet been defined in clear technical terms. SCR representatives stated that NASDA was studying possible 8- and 16-ton GEO space platform configurations several years ago, but that these concepts are not under active study now.
A joint venture between the United States and Japan on a GEO space communications platform for mobile and broadcast services looks feasible for the 1993-98 time period if such a project was found mutually interesting.