21 GHz, Ultra-HD’s Holy Grail?

[SAT-WORLD]

Japan’s public broadcaster NHK is looking to satellite’s Ka-band for its future transmissions.
Will the rest of the world follow suit?
Ka-Band lies just above the immensely popular and crowded Ku-Band. Ku-Band works well for satellite transmissions, with most broadcasters managing to exploit a satellite’s high-power output to beam their signals to increasingly small dishes. But the problem with 21 GHz is that it doesn’t cope with heavy rain (or snow) very well.

The upside to 21 GHz is that the spectrum is largely unused. Indeed, the satellite industry has been seeking a use for the bandwidth for years and all manner of schemes have been proposed, including complex multiple spot-beams for satellite-supplied broadband.

The Japanese suggestion takes 21 GHz to the transmission limits. NHK’s engineers say that by using a phased array antenna on the satellite they can transmit higher power levels to those regions of a country suffering heavy rain – vital in a nation like Japan that suffers Monsoon-type rainfalls, and Typhoon-grade storms. In practical terms this means that two antennas will be used, one will cover the whole nation and the second, more concentrated, will cover a region about 200 km in diameter and focused on the Tokyo super-region. This super-beam will be activated if there’s poor weather.

But there’s a problem with simply boosting power-levels in this fashion. The all-important Travelling Wave Tubes get very hot, and the heat has to be dissipated somehow. NHK has worked with Japan’s Aerospace Exploration Agency to evolve methods to handle these heart levels.

The next stage is to start experiments, and Japan plans to use its ultra high-speed 21 GHz internet craft (called Kizuna, meaning Winds) for Ultra HD transmissions. Ground-based experimentation has already started, and the Japanese are saying that more sophisticated orbiting tests will start around 2010-2011.

Source:Rapid Tv News