. The Bell System technical journal . ream admittances in the designof microwave amplifiers and of the need for a better understanding of theperformance of the 1553, a program was initiated to investigate some of ADMITTANCES OF PARALLEL-!LANE ELECTRON TUBES 621 these effects experimentally. It seemed best to start this work with a studyof the electron stream admittances of simple diodes, with the object ofextending the measurements to the triode as the work progressed. Diodes Tlie diodes used in this work were identical in construction with the 155,^triode, Inil for the substitution of a solid
. The Bell System technical journal . ream admittances in the designof microwave amplifiers and of the need for a better understanding of theperformance of the 1553, a program was initiated to investigate some of ADMITTANCES OF PARALLEL-!LANE ELECTRON TUBES 621 these effects experimentally. It seemed best to start this work with a studyof the electron stream admittances of simple diodes, with the object ofextending the measurements to the triode as the work progressed. Diodes Tlie diodes used in this work were identical in construction with the 155,^triode, Inil for the substitution of a solid copper anode in place of the all cases the cathode-anode spacing was approximately mil, and thearea of the cathode was square centimeters. With this spacing onewould expect the potential minimum to be relatively close to the anode suchthat a considerable portion of the cathode-anode region would containelectrons moving in both directions. The potential distribution then wouldbe something like that shown in Fig. Fig. 2—Electron motion in a close-spaced diode. The method used in measuring the microwave-frequency input admit-tances of diodes was based largely on a technique used by Mr. J. A. Morton,and will be described in some detail. In a typical amplifier, radio-frequency power is fed from a waveguidesource to the cathode-grid input region of a 1553 triode through a waveguide-cavity transformer. A similar circuit can be used for measuring diode ad-mittances. The fundamental problem is to learn how to relate admittancesmeasured with a standing wave detector located in the wa\cguide supplyline to the equivalent two-terminal admittances located at the cathode-anode gap of the diode itself. In other words, we have to know the trans-formation-ratio between an admittance across the cathode-anode gap of thediode and the corresponding admittance which will be measured in thewaveguide. Let us refer to the circuit in Fig. 3. The circuit shows an input trans- 622
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