Broad-Band Noncontacting Short Circuits for Coaxial Lines: Part I. TEM-Mode Characteristics

This paper discusses the factors that must be considered in the design of an S-type noncontacting plunger, which will present an effective short circuit to the TEM-mode in a circular coaxial line over a frequency tuning ratio of 3 to 1 or more Since there are no sliding contacts, a coaxial resonator may be tuned an unlimited number of times with this type of plunger and still remain free from physical wear, "finger noise," and mechanical hysteresis and drag. It was the use of this type of plunger that made possible the development of local oscillators which can be tuned an unlimited number of times over a microwave frequency range as great as 2 to 1. Subsequent Parts II and III of this paper will deal with the analysis and methods of controlling the parasitic resonances which may occur in a noncontacting plunger when the operating wavelength is less than the circumference of the outer coaxial line.