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Traveling wave vacuum tubes are now back – and better than ever.

Posted on February 12, 2016

Vacuum tube technology, which was state-of-the-art for radio and television sets in the 1940s and 50s, is making a resurgence in certain wireless communication fields.  In the process, technology enterprises are faced with challenges in protecting innovation over decades-old prior art.

Vacuum tubes promise to provide effective solutions to several problems faced by designers of millimeter wave and sub-millimeter wave radio frequency communication systems, and are thought to be key for significant improvement in mobile communications bandwidth.  A particular type of vacuum tube, traveling wave tubes, was first used in global communication satellites in the early 1960s, only to be eclipsed by the concurrent, explosive growth of semiconductor technology.  Those traveling wave vacuum tubes are now back – and better than ever.  In today’s cutting edge, ultra-compact and ultra-efficient cold-cathode vacuum tubes, traveling wave radio frequency signals are amplified by injection as an electron beam from the cathode into a helical circuit modulator, which results in exponential growth of the modulated radio frequency signal.  In addition, modern traveling wave tubes can actually recover some of the “lost” power not conveyed to the collector, in a manner similar to regenerative brakes in a hybrid or electric car.  Improvements in computer modeling and simulation, pulsed operation, materials science, and microfabrication techniques are all collectively enabling transmissions by vacuum tubes with astonishing power at frequencies in excess of 200 giga-Hertz.  The resulting devices far outperform counterpart semiconductor devices in both efficiency and costs. 

On top of industry bias in favor of integrated circuits, however, modern vacuum tube innovators face obstacles in protecting their investments in research and development.  Patents and trade secrets, the normal workhorses of intellectual property protection, both depend on an absence of prior, general knowledge for the innovation to be protectable.  Vacuum tubes saw decades of use and refinement before languishing into only limited use by electronics buffs and ham radio operators.  Unfortunately for modern innovators, for what may be the first time in history, information that saw even just limited publication fifty years ago or more is often still reasonably accessible to either patent examiners or competitors seeking to overcome patent or trade secret protections. 

Innovative improvements to vacuum tube technology are still protectable – just with somewhat more effort.  Enterprises in these situations should make the effort to obtain and catalog past publications within the relevant field, preferably creating searchable databases.  This involves more than mere Googling or searching recent patent and non-patent literature databases; review of library books, journals and microfiche collections and searches in foreign patent offices will ensure accuracy and completeness of the understanding of what was known, even back to five decades ago or more.  Once developed, the most relevant prior art material needs to be identified for individual improvements, disclosed in patent applications as appropriate, and specified within a trade secrets log.  Innovations are then characterized against the backdrop of what is — or has been — already known.  In this way, the enterprise dramatically reduces the risk that a competitor will later unearth prior art damaging to the enterprise’s patent or trade secret claims.

History may repeat itself, even in technological fields; but innovation relating to “old” technologies can still receive strong protection when proper practices are put in place.