September 24, 2012
Credit: Credit: L-3 Communications
Amy Svitak Velizy, France, and Paris
Traveling wave tubes and the process required to manufacture them have changed little over the past half-century. But these archaic vacuum-electron devices, known as TWTs, generate high-powered radio-frequency signals on some of the most advanced telecom satellites orbiting today.
Over the years, TWTs have become smaller, lighter, more powerful and efficient. But as satellite technology races ahead, production of these key components remains largely stuck in the past.
With global demand for faster and more affordable broadband on the rise, large satellite operators in Europe and the U.S. are starting to populate their fleets with high-throughput Ka-band communications satellites that can deliver high-speed bandwidth virtually anywhere on the planet. Over the next few years, the world's two principal TWT suppliers—L-3 Communications and Thales Electron Devices—anticipate a corresponding increase in TWT unit orders, in particular for high-frequency Ka-band tubes that generate huge amounts of spectrum power in the 18-40-GHz. range.
With close to 11,000 TWTs in space, Thales has more than 500 million hours in orbit, “and 50 million hours being added each year,” says Jean-Francois Auboin, director of Thales space programs and engineering. When mated with a regulated power supply, TWTs are ideal for sending large amounts of data over long distances, providing more power and efficiency than solid-state radio-frequency transistors, he says.
Both L-3 and Thales have seen an increase in orders for Ka-band wave tubes in the past few years. At Thales, roughly 50% of TWT units delivered in 2011 were in the Ka-band frequency spectrum, Auboin says. Although he anticipates the trend will continue, comparably ramping up TWT production capacity is easier said than done.
Built one at a time by hand, in production facilities redolent of the 1950s, Ka-band TWTs are assembled in a process that is part engineering, part alchemy, a series of painstaking steps that can take up to a year to produce a single, functioning device.
Hunched over microscopes, tweezers in hand, workers at Thales's Velizy factory look less like radio-frequency engineers than jewelers soldering metal or setting precious stones. Rudimentary as the process may seem, the skill of assembling high-frequency-band tubes is costly and difficult to master. Once trained to assemble C- or Ku-band tubes, a worker cannot simply switch to building higher-frequency Ka-band TWTs.