High-gain crossed-field amplifier tube

Raytheon Company, under Naval Electronic Systems Command sponsorship, has conducted a program to develop a high gain crossed-field amplifier. This development program reflected the future needs for high-gain CFA´s that would permit lower-powered rf drivers and eliminate the need for high power isolators. Present advantages of the crossed-field amplifier, such as high efficiency and cold cathode operation, were to be retained. The method of obtaining high gain in a crossed-field amplifier was to introduce the rf drive signal at the source of electrons. This was accomplished by forming the secondary emission cathode into a slow-wave structure that will support microwave energy. The traveling wave on the cathode forms the desired space charge spokes at a low energy level. These space charge spokes induce current in the anode circuit. The introduction of rf drive signal onto the cathode also provides a high degree of isolation between the amplified output signal and the rf drive energy. During the present cathode-driven, crossed-field amplifier program, the S-band CFA was operated with an rf gain of 28 dB over a frequency band of 14%. Initial background noise measurements were made using a full 2000 MHz sweep on the spectrum analyzer.