Site: Nippon Hoso Kyokai (NHK)
Japan Broadcasting Corporation
Science and Technical Research Laboratories
Setagaya-ku, Tokyo 157, Japan
Date Visited: June 6, 1997
WTEC: K. Bhasin (report author), N. Helm, C. Mahle, R. DePaula, J. Evans
Nippon Hoso Kyokai (NHK) is Japan's sole public broadcaster, established in 1925. It is financially and operationally independent of the government and corporate influence. It is supported by monthly receiver fees of ¥1,395 for terrestrial broadcasts and an additional ¥945 for satellite broadcasts. These receiving fees account for 97.3% of operating revenues. There are more than eight million satellite receivers; two 24-hour satellite channels are being broadcast by NHK. It began direct broadcasting satellite (DBS) service in July 1987; since then it has been growing steadily, and is expected to grow as a major multimedia service for the next century. BSAT-1a (provided by Hughes International) was launched in April 1997 to support growth of DBS.
NHK has two research institutes that provide both hardware and software. Broadcast engineering is carried out by the NHK Science & Technical Research Laboratories, which the WTEC team visited, while program development is undertaken at the NHK Broadcasting Culture Research Institute. The NHK Science and Technical Research Laboratories were established in 1930, just five years after the start of radio broadcasting in Japan. The laboratories started out with a staff of 16 who researched such areas as the acoustic design of studios and the development of a domestic radio. The lab now has a staff of some 315 people. It is now working to put new broadcast media into practical use, and to improve equipment and systems for conventional broadcasting. Vigorous research is also being conducted on broadcast systems of the future. As Japan's sole integrated research institute for broadcast technology, the lab has been key to NHK's progress. It carries out its mission for future systems in three main areas:
The NHK Science and Technical Research Laboratories is working on the state-of-the-art broadcasting technologies presented below.
Following the success of DBS, the lab is engaged in the development of digital broadcasting systems, such as ISDB (integrated services digital broadcasting). Broadcast equipment, transmission systems and home receivers for new broadcast media services are also main subjects. See the list below.
Studies on areas ranging from program production technology to reception technology are conducted in order to improve such conventional broadcasting services as FM radio and terrestrial TV broadcasting. The list of topics is shown below.
Broadcast media will serve increasingly as the dominant source of information in the future. The development of more advanced and varied forms of broadcasting requires basic research into human sight and hearing, as well as solid-state devices and materials. NHK is researching three dimensional television systems (3D-TV) in addition to artificial intelligence (AI) technology, ultrahigh-density recording, and optoelectronics devices. The list is below:
Detailed information was presented on several key technology development activities related to satellite communications. These activities are discussed below.
Services currently use 12 GHz for both FSS and BSS. NHK broadcasts 2 programs, NTSC and HDTV (MUSE, 17 hours per day), and has about 10 million satellite subscribers out of a total of 35 million overall subscribers. There are 5 commercial TV broadcast networks in Japan. Digital TV broadcast is used in the DVB-S transmission system (29 Mbps per transponder, 4 to 6 channels of TV broadcast per carrier). PerfecTV started in 1996 and has 300,000 subscribers using JCSat. NHK has BS-3 (NEC built) and BSAT-1 (Hughes built, launched in April 97). BSAT-1 can transmit four 27 MHz channels out of 8 channels allocated. NHK expects to start digital TV Service around 2000. The 8 channels would consist of 4 analog and 4 digital channels.
NHK has a vision of what is needed for a future digital TV broadcast system. It is developing ISDB for BSS- band (2 channels of HDTV in one transponder). As the HDTV display is still costly (¥300,000 now, ¥150,000 next year for a 32" display), a converter box for about ¥20,000 is seen as a way to go from analog HDTV to digital. There is a lab prototype, which uses TC8PSK, QPSK and BPSK with 40 Mbps rate per transponder in 27 MHz of bandwidth. The essential information is QPSK at 1.2 Mbps (it gives a smaller picture when rain faded) with high quality information at around 20 Mbps. Control information is BPSK. A single unit switches between the three. This way the availability is 99.8% with 10 dB rain fade.
The frequency of 21.4 to 22 GHz is allocated here for TV broadcasting. In Tokyo, during the worst month there is 99% availability with 10 dB margin at 22 GHz while only 2 dB margin is needed for 12 GHz. Rain mitigation needs two mechanisms, satellite power control and hierarchical transmission. The carrier-to-noise-ratio (C/N) is 7.1 dB for QPSK rate ½, 10 dB for QPSK rate ¾ and 12.7 dB for TC8PSK rate 2/3. NHK designs for 7 dB power control range in satellite EIRP with two parallel TWTs. The system has 10 dB fade margin in which a 3 dB margin is inherent. The TWT is a NEC helix with variable power from 40 to 230 W at 22 GHz with 53% efficiency. Conduction cooling is used. Its mass is 1.1 kg. EPC for the tubes runs around 12 kV. The antenna for operational use must have 6 beams, 2.8 m reflector and 47 dBi.
Dr. Shogen presented a satellite newsgathering setup. A flat antenna for 14 GHz with 16 SSPAs is mounted on a gimbaled pedestal that tracks low rate motion. Fast steering is electronic via 16 8x8 element phased arrays, with 16 phase shifters (the 8x8 element subarrays are fixed). A 17th array is for grating lobe suppression. The SSPA has 5 W, total 80 W, and 30 W losses. The 3 center subarrays can receive 12 GHz and feed a beacon receiver to point the beam. Experiments at sea worked well. NEC is building this for the commercial market. At 14.5 GHz it has 513 dBW EIRP. Overall beam steering is plus or minus 2 degrees electrical, more mechanical and with overall 0.05 degrees pointing accuracy.
A lab tour of facilities included antenna models, during which TWTs (Toshiba and NEC) were shown. A prototype digital HDTV system was demonstrated through a rainfade. The team also saw a true multimedia HDTV setup. Work to define user desires is continuing. The idea is that TV broadcast downloads lots of information into the local server. Information is immediately accessible and automatically updated. Internet and other services can be accessed simultaneously with TV pictures (smaller than full screen). For local storage of program material, a mouseclick on the TV schedule will record.
NHK plays a central role on broadcasting in Japan. Its funding is assured through monthly fees on every receiving household. There is no corresponding entity in the United States. NHK provides a unified, stable, long-term outlook for broadcast satellite development. NHK has a technology development program that has provided progression from conventional BSS-TV at Ku-band, to HDTV broadcast at Ku-band, and continuing through to possible DBS TV at 21 GHz. It is engaged in the development of multimedia services by merging TV and PC technologies which will have significant impact on the emerging information infrastructure in the 21st century.