INVESTIGATION OF LOW WEIGHT FOCUSING SCHEMES FOR TRAVELING-WAVE TUBE AMPLIFIERS.
Quarterly rept. no. 3, 15 Jan-14 Apr 67,
WATKINS-JOHNSON CO PALO ALTO CALIF
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The report describes the third quarter results on a program concerned with the investigation of lightweight focusing schemes for low-noise TWT amplifiers. These results are of significance because they represent an advance in low-noise, X-band TWT technology and show some important effects of reversed-field focusing on solid and hollow beams. The results show that a noise figure less than 6.0 dB, a gain greater than 30 dB, and an output power greater than 10 mW can be achieved at X-band frequencies with a solid-beam tube focused in a lightweight, 3.4 pound, single-reversal permanent magnet. The results also show that a noise figure less than 5.0 dB, a gain greater than 20 dB, and a power output greater than 0.5 mW can be achieved at X-band with a lightweight, 6.4 pound, straight-field permanent magnet. A high magnetic field is necessary to achieve lowest noise performance in a SRPM. Unfortunately, this causes velocity spread effects which seriously degrade the gain and power output of the tube. The best means for minimizing the velocity spread without increasing the noise figure is to employ a low gamma a, high voltage helix design. A low voltage, low current density, hollow-beam tube gives lower noise figure than higher voltage solid-beam tubes. However, a hollow beam collapses when it passes through a sudden field reversal. This causes a drastic fall off in gain and power. The utility of a low noise, hollow beam SRPM tube awaits evaluation of a severed helix design which incorporates a high gamma a input helix and a low gamma a output helix. Author
- Electrical and Electronic Equipment