GB890801A - Improvements in or relating to high frequency electro-magnetic wave energy transmission lines - Google Patents

Abstract

890,801. Waveguides. WESTERN ELECTRIC CO. Inc. Oct. 16, 1959 [Oct. 30, 1958], No. 35067/59. Class 40(8). A waveguide for propagation of energy in the H<SP>01</SP> mode comprises a conductive helix 41 surrounded by a layer 45 of lossy dielectric material, the whole being encased in a conductive jacket 46. The layer 45 has a thickness equal to an odd number of quarterwavelengths of the propagated energy so that it transforms the low impedance of the jacket 46 to a high impedance at the inner surface of the layer. The helix consists of stranded or solid wire made from copper or a base metal coated with, e.g. silver. The turns of the helix are spaced by a distance less than one quarter-wavelength and the space between the turns may be occupied by a thin coating of dielectric on the surface of the wire. The lossy dielectric 45 does not extend into the space between the turns of the helix and the outer surface of the helix may be overlaid with a thin sleeve of lossless dielectric material. The lossy dielectric 45 may have a power factor of about 0.5 and may comprise polythene loaded with iron dust or carbon black, glass roving or glass tape coated with tin oxide or carbon, carbon loaded paper or cotton string coated with carbon. Alternate layers of lossy and lossless dielectric may be used. The jacket 45 may consist of a copper or steel tube or may be made of overlapping metallic strips or woven braid. Specifications 764,737, 855,026, 890,799 and 890,800 are referred to.