10 KW traveling-wave tubes for CW communications at C-band, X-band, and KU-band

A series of high gain, high efficiency traveling-wave tubes are described which have been specifically designed for ground based communication transmitters. These devices employ improved versions of the coupled-cavity circuit along with special techniques for band edge oscillation suppression. Noise measurements close to the carrier prove an unusually low degree of spurious output and a minimum of ion induced noise. Efficiencies of 20% to 33% have been achieved without the use of a depressed collector. At X-band efficiencies in excess of 40% have been demonstrated in a 10 kw amplifier with 50 db of gain through the use of a depressed collector. No observable regeneration effects have been present under these conditions. Linearity and intermodulation distortion have been extensively investigated and the results compared with other types of microwave amplifiers. A new method of negative feedback has been evolved which reduces third order distortion by at least 20 db beyond the value measured without feedback.