GB1072327A - Flexible waveguide of oval corrugated tube - Google Patents

Abstract

1,072,327. Waveguides. TELEFUNKEN PATENTVERWERTIWGS G.m.b.H., and HACKETHAL - DRAHT - UND KABELWERKE A.G. Sept. 11, 1964 [Sept. 18, 1963], No. 37254/64. Heading H1W. Optimum dimensions, as regards attenuation and flexibility are chosen for a flexible, corrugated waveguide of oval cross-section intended for transmission of a plane polarized wavemode. A dimension A w , the " effective major axis," is defined by the expression: where a 1 is the major axis of the guide measured between the inwardly extending ridges of the corrugations, a 2 is the major axis measured between the grooves of the corrugations, t 1 is the depth of the grooves measured in the direction of the major axis (t 1 = (a 2 - a 1 )/2), and K 1 is a corrective factor lying between - 0.65 and +0À65 dependent upon the shape of the grooves. A dimension b w , the " effective minor axis", is similarly defined. According to the invention, the dimensions of the waveguide are chosen so that the ratio b w /a w lies between o.5 and 0.8. In the graph of Fig. 7 (not shown) the abscissae represent the ratio b w la w and the ordinates represent the working frequency relative to the cut-off frequency of the guide. A line (G) represents the upper limit of the pass-band, defined by the lowest frequency at which unwanted modes appear, and a line (E) represents the lower limit chosen to be 20% above cut-off. The lines (A) and (C) represent signals having a 10% band-width respectively transmitted in guides for which b w /a w is chosen for minimum attenuation and for maximum flexibility. An optimum waveguide affording both good attenuation and good flexibility may have a ratio b w /a w equal to 0.6 and transmits a signal represented by line (B). The corrugations may be helical and preferably have a pitch angle of between 0 and 60 degrees. The pitch angle may vary along the axis of the guide (e.g. between - 10 and +10 degrees). The depth of the corrugation may be different in the directions of the major and minor axes but both values are preferably less than 0À2a 1 . The profile of the corrugations may be sinusoidal, in which case K 1 =0. If the ridges of the corrugations are broadened, the corrective factor K 1 is positive and if the grooves are broadened the factor is negative (Figs. 4, 5 and 6, not shown).