The carpitron as a power amplifier in a communication satellite

The carpitron, an externally R.F. driven cross-field oscillator (carcinotron) has been used for several years as a power amplifier at C Band in ground stations operating in conjunction with Intelsat geostationary satellites. It can amplify one single carrier allowing transmission of a large number of voice channels or one television program. Observed operating life exceeds 25,000 hours. It was thought that this kind of microwave tube could be used as a satellite-borne power amplifier. A carpitron of a simple design built for operation at 12 GHz showed 38% electronic efficiency at 500 watts output power and 15 dB gain. The injected beam is generated by a short kino gun with a cathode current density of 1.5 ampere per square centimeter. An improved tube has been designed, which is presently under construction, with two main objectives: 1. Increase electronic efficiency to 50% or more. 2. Better distribution of the intercepted beam along the delay line. In order to achieve these objectives a large signal computer program was used to design a constant phase velocity, variable impedance, delay line. Computer results show the possibility of efficiency improvement. Confidence in computer program was gained from good correlation between computed and experimental results observed on previous tubes. Computed and experimental results on improved carpitron will be given at the conference. This work has been partly supported by the European Space Research Organization (ESRO).