Crossed-Field Microwave Devices

Abstract

Crossed-Field Devices are high-power devices and are associated with high efficiency, small weight, adequate bandwidth and good performance as regards various parameters such as phase coherence, jitter, fast frequency sweep and phase versus frequency. Distributed-emission type devices using cold secondary emitter cathode have the advantage of no heater requirement and thereby stand-by requirements are eliminated. Use of platinum as secondary emitter is anticipated to result in 100 000 hours of life of crossed-field devices. In linear format costly modulator is not required and this device provides the flexibility of sophisticated wave shape pattern generation. A number of tubes can be operated in parallel resulting in high output power and at the same time providing redundancy to prevent a total system failure if one tube fails. Same tube type with power dividers can be used as a driver as well as the PA, thereby simplifying the logistics. Life of microwave tubes can be significantly increased and maintenance problems reduced by proper care and handling of these devices.

These devices are superior to linear tubes in many respects except gain and noise output; this has restricted the wide use of CFAs in all systems. Recent developments in achieving high gain and low noise with these devices, provide a great deal of optimism in use of these devices in future systems. Cost reduction techniques in case of cooker magnetron in particular, and above developments signify the importance of continued R&D support in this area, for increased exploitation of their potential and more utilization of these devices.

Indexing Terms:

• Crossed-Field Devices
• Microwave Power Sources
• M-Type Tubes

Additional information

Notes on contributors

R. P. Wadhwa

WADHWA, R P (Dr.): BSc (Hons), DIISc, MEE, DSc,: Was a research student at the IISc, Bangalore (1955) and then worked at CEERI, Pilani at Rensselaer Polytechnic Institute, at EPSCO Boston (1957); Engineer at IBM, Poughkeepsie (1958–59); Research Engineer at University of Michigan (1959–63) and Senior Engineer at Litton Industries (1963–66). While working with Litton Industries, he had also held a part-time teaching assignment with University of California Extension Service. Worked as Assistant Director at CEERI, Pilani (1966–70) and joined BEL, Bangalore as Deputy General Manager (Feb. 1970).

Dr. Wadhwa has worked in the area of delay lines, microwave measurements, noise in Crossed-Field-Devices, Ion-Beam- Neutralisation for Space travel, development and production of microwave components, wide dynamic range Crossed-Field Guns, development and production of various types of electron tubes including various expansion programmes involving design and construction of sophisticated equipments. He has published nearly 40 papers in these fields, guided students for MTech as well as PhD degrees, and has three patents to his credit.

His work for 3.5-dB Noise Figure Crossed-Field Amplifier was a major break-through. He was awarded the Shanti Swarup Bhatnagar Prize for the year 1972 for his outstanding contributions in Engineering Sciences. Appointed Honorary Editor for JIETE in the area of ‘Electron Devices’.

He was Vice-President of Indian Vacuum Society (1972–74), President of Indian Vacuum Society (1974–76), Council Member of IETF. (1972–75). He is MIETE, SMIEEE.