Precise 50 to 60 GHz Measurements on a Two-Mile Loop of Helix Waveguide

Low-loss transmission via the TE 0 i mode in circular waveguide has been studied for many years for use as a wideband communication medium.1 Much work has been done on the design of improved waveguides, 2,3 the understanding of the effects of spurious modes,4-5 and the measurement of sample guides over wide frequency bands.0-7 Interesting waveguide communication system layouts have proposed repeater spacings in the range of 10 to 20 miles. Reasonable design requires that the total loss of such a waveguide section be predictable to within a few dB. However, the longest guides on which measurements have been reported are a few hundred yards, and the variation to be expected between different samples of similar construction is unknown. This paper describes measurements made in the 50 GHz to 60 GHz band on a two-mile triangular loop of helix waveguide. Extremely precise observations were made on many sections of the loop in order to: (i) Test whether the loss of a long line is indeed the sum of the losses of its component sections as is expected if the sections act independently. 933