Sometimes it takes years—even decades—to turn a good idea into reality. Such was the case with direct broadcast satellite service. After almost 20 years of research, Japan’s public broadcasting organization, NHK, began the world’s first DBS service in 1984, laying the foundation for today’s satellite television. On 18 November, IEEE is honoring the development with a Milestone in Electrical Engineering and Computing.
CONCEPT TO REALITY
NHK’s work on DBS, which beams TV broadcasts into homes, bars, restaurants, and other places where it has been ordered, started with a theory: If radio waves can be transmitted from a satellite in space, then simultaneous communications and broadcasts over a wide area on Earth must be possible. First theorized in 1945 by radar engineer Arthur C. Clarke, who became famous as a science fiction author, the idea sparked NHK President Yoshinori Maeda’s interest in 1965. Maeda thought satellite broadcasting of TV signals to homes could be possible. NHK also was influenced by the communications satellites being developed in the United States at the time, such as Telstar.
NHK spent the next 18 years researching how to develop DBS, with the help of other companies and organizations including Toshiba, General Electric, the Telecommunications Satellite Corp. of Japan (TSCJ), and NASA.
To aid the satellite’s development, Japan in 1969 established the National Space Development Agency of Japan (NASDA), which made that its primary mission.
But there were many challenges. Such broadcasting would require a far smaller antenna and a higher-sensitivity receiver on the ground than was being used at the time. The receiving antennas for satellite communications ranged in size from several meters to dozens of meters in diameter—much too large for home use. Also, home receivers would have to be inexpensive yet offer higher sensitivity even with increased output from the satellite.
A key breakthrough was the invention by Yoshihiro Konishi, NHK research engineer in chief, of an inexpensive solid-plane circuit with a low noise figure in the 12-gigaherz band. By using low-noise home receivers, the output power of the satellite’s transmitter could be lowered to 100 watts—which enabled the satellite to be smaller. Terrestrial television broadcasting stations use power on the order of 50 000 watts. The solid-plane circuit also solved the problem of making an affordable home receiver. Using the 12 GHz band was also important, because the rain attenuation (the fading in signal caused by atmospheric rain, snow, or ice) in that band wasn’t severe.
Japan’s first broadcast satellite, known as the BS, was launched in 1978 atop a U.S. Delta rocket. A year later, two backup satellites, BS-2a and BS-2b, were launched. On 12 May 1984, the BS-2a became the first national DBS, transmitting experimental TV signals into the homes of Japanese viewers. The DBS relied on a satellite in geostationary orbit broadcasting to small antennas atop the home receivers.
The result was a vast improvement over terrestrial broadcasting of the time, which involved large transmitting stations equipped with huge antennas and expensive receivers cooled with liquid helium. The satellite transmissions led to a clearer picture and could be broadcast over a large area. The reception area included more than just the main islands of Japan; it reached out to islands in the Pacific Ocean that were up to 1000 kilometers away from the nearest terrestrial broadcasting station. Other advantages included the ability to receive signals behind tall buildings and high mountains—a problem with terrestrial broadcasting.
A ceremony dedicating a Milestone plaque is to be held outside the NHK Science and Technology Research Laboratories, in Tokyo. The plaque reads:
NHK began the world’s first direct broadcast satellite service in May 1984. This was the culmination of 18 years of research that included the development of an in expensive low-noise receiver and investigations of rain attenuation in the 12 GHz band. RRL, NASDA, TSCJ, Toshiba Corporation, General Electric Company, and NASA participated with NHK to make satellite broadcasting to the home a practical reality.
For more information about this and other IEEE Milestones, visit the IEEE Global History Network.