A cyclotron resonance frequency multiplier

The current density available from known thermionic cathodes imposes a serious limitation on the power output obtainable from electron tubes operating at frequencies above about 10 Gc. This paper describes a proposal for a frequency multiplier which has the interesting property that the RF energy imparted to the electron beam by the signal source may be one or two orders of magnitude greater than the dc energy supplied by the battery. Thus it is expected that the power output at a particular frequency will be much higher for a given cathode current density than that obtained from conventional types of electron-beam oscillators and amplifiers. The multiplier operates by converting the input energy at one radio frequency into rotational energy of an electron beam by means of a Cuccia coupler. The beam then couples power to the output load via a multicavity circuit containing cavities where is the frequency multiplication to be obtained. The paper includes details of experimental work on a low-power tube multiplying from 600 Mc to 3600 Mc. In this tube 1.3 watts of RF input power is coupled on to a 50 volt, 260-µa beam and the power at 3600 Mc is coupled out via a 12-cavity magnetron anode structure. Photographs are given of the trace of the rotating beam impinging on a fluorescent screen and these demonstrate the degree of focussing achieved along the length of the tube. The paper concludes with a study of the feasibility of a tube multiplying from 10 Gc to 100 Gc with an output of tens of watts.