JED - July 2009 - (Page 26)

By Barry Manz For generating truly impressive amounts of radio frequency (RF) power, especially over broad bandwidths at frequencies from 4 GHz to 100 GHz, nothing beats a vacuum electron device (VED) and, in particular, a traveling wave tube (TWT). As a result, while the markets for VEDs (vacuum tubes in the vernacular) are flat according to most reports; klystrons, crossed-field amplifiers, gyrotrons, magnetrons, inductive output tubes (IOTs) and TWTs will continue to generate hundreds of millions of dollars in revenue thanks to their use in defense, scientific and medical applications. While solid-state RF power transistors are slowly creeping upward in efficiency, output power and frequency, their ability to produce the megawatts of power from a klystron at 40 GHz or 250 kW from a TWT remains far out on the horizon. RF power transistors based on gallium arsenide (GaAs), silicon (typically bipolar junction transistors or BJTs and LDMOS FETs) or gallium nitride (GaN) – the defense industry’s compound semiconductor technology – are being deployed in improvised explosive device (IED) jammers and other comparatively low-power electronic warfare (EW) systems. However, in many EW systems, performance over very broad bandwidth is paramount and tubes reign supreme and likely will remain so for years. In short, industry prophets and the media have predicted for years that VEDs of all sorts The Traveling Wave Tube Lives On… and On would soon be relegated to microwave lore, victims of the inexorable march of semiconductor technology. But as we move toward the second decade of the 21st century, VEDs still are not just viable but essential for military and commercial applications alike. well-acquainted with the unique benefits provided by TWTs. For proof, consider that there currently are at least 300,000 TWTs and other VEDs employed in nearly 300 US defense systems of various types, with radar, EW and satellite communications systems being the largest consumers. Even though government funding of VED development has been spotty in recent years, TWT development is hardly standing still, not just in the United States but in many countries. This year’s International Vacuum Electronics Conference (IVEC) in Rome, sponsored by the European Space Agency, included papers from the United States, Russia, China, Korea, Germany, Israel, Switzerland, France, Italy, Ukraine, Norway, India, A TUBE, YOU SAY? Vacuum tubes are not in the vocabulary of almost anyone born after about 1970, unless they happen to be amateur radio operators or audiophiles seeking that “tube sound.” Even to designers in the commercial wireless industry, vacuum tubes either are archaic or irrelevant. However, designers of EW systems, satellite communications transponders or broadcast transmitters are TWT and MPM Manufacturers CPI dB Control e2v ELTA Systems Ltd L-3 Electron Devices L-3 Electron Technologies NEC Teledyne MEC Thales Electron Devices TMD Triton

Table of Contents for the Digital Edition of JED - July 2009

JED - July 2009
The View From Here
From the President
The Monitor
Washington Report
World Report
Advancing TWT Technology
Technology Survey: COMINT/DF Receivers
EW 101
AOC News
JED Sales Offices
Index of Advertisers
JED Quick Look

JED - July 2009