THE CHARACTERISTIC IMPEDANCE AND PHASE VELOCITY OF A SHIELDED HELICAL TRANSMISSION LINE
Abstract
The results are given a theoretical and experimental investigation of the properties of a shielded helix when used as a transmission line. Such a structure is dispersive and, because of the presence of both TM and Te modes, cannot have a true characteristic impedance. However, such an impedance is defined in terms of a distributed capacitance and inductance. These parameters are determined for the case of infinite wave length for round wire helices. The equations are developed for a uniform dielectric inside the shield and for 2 dielectrics, one inside the helix and the other between the helix and shield. These analytic results are shown to agree with the experimental results obtained by the author and by Keutner (Elektrische Fernmeldetechnik, no. 62:3, 1943), Susskind (T.V.E. :26, 1951), and Kukel (Engineering Problems in the Exponential Transmission Line Pulse Transformer Design, Ph.D Dissertation, Carnegie Institute of Technology, 1953). An attempt was made to solve the wave equation for a tape helix; the tape is assumed to be anisotropic to the extent that it can conduct only the helix direction. The results show that the phase velocity varies as the frequency variex. The phase velocity and characteristic impedance of a narrow tape helix compare favorably with these same properties of a wire helix, the wire diameter being equal to the tape width.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 30, 1953
- Accession Number
- AD0012477
Entities
People
- Herbert S. Kirschbaum
Organizations
- Carnegie Institute of Technology