Accession Number:

ADA080427

Title:

Intermodulation Measurement in the UHF Band and an Analysis of Some Basic Conducting Materials.

Descriptive Note:

Technical note,

Corporate Author:

MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB

Personal Author(s):

Report Date:

1979-11-19

Pagination or Media Count:

48.0

Abstract:

In a modern communications satellite, it is generally required that high-power multi-channel transmitters and super-sensitive broadband receivers be packed in a limited space. Because of the very large power level difference between transmit and receive signals and the limitation of frequency allocation, intermodulation IM interference due to passive residual nonlinearities in the high-power transmission path can be a real problem. This kind of problem did crop up during several communication satellite development programs. This report represents an effort toward a better understanding of the general IM phenomenon. Passive nonlinearities of resistivity in conducting material, in contrast with that due to contact junctions, were studied by careful measurement and analysis. Forward and backward traveling wave IMs in a long transmission line were distinguished and interpreted. New evidence concerning the deviation from Ohms law by metal conductors was obtained and quantitative characterization of the weak nonlinear characteristics of good conductors was attempted. The IM production of steel, stainless steel, and graphite fiber were conclusively demonstrated. These materials are used in certain filter and antenna fabrications in aerospace applications for low thermal expansion or light weight. Intermodulations generated by many commonly used conducting materials were measured in the UHF band and analyzed in terms of resistivity nonlinearities. Contact nonlinearity at the most critical locations in the measurement was avoided by the use of quarter-wavelength couplings. Forward and backward traveling intermodulation waves in a transmission line were distinguished and interpreted.

Subject Categories:

  • Cybernetics
  • Electricity and Magnetism
  • Radiofrequency Wave Propagation

Distribution Statement:

APPROVED FOR PUBLIC RELEASE