Imperfections in Lined Waveguide

Lined waveguide shows promise as a communication medium. Circular electric wave loss in bends is reduced by a low-loss lining. A lossy lining reduces the degrading effects of mode conversion and reconversion. In straight circular waveguide with a perfectly uniform lining, circular electric waves will only suffer a slight increase in attenuation due to the loss factor of the lining and the slightly increased wall currents. Also, the phase constant will be only slightly shifted. Otherwise the transmission characteristics will remain smooth and undistorted. A perfect waveguide with a perfectly uniform lining, however, cannot be realized in practice. The waveguide will be slightly deformed, and any lining as it is applied by spraying, dipping, or other methods, will show variations in thickness along the circumference as well as longitudinally. These variations will, in general, be distributed randomly. 1 * Technische Hochschule Braunschweig; work done under letter contract . 1589 1()00 THE BELL ST,STEM TECHNICAL JOURNAL, SEPTEMBER 1962