GB1321582A - Leaky coaxial cables - Google Patents

Abstract

1321582 Aerials; radio signalling SUMITOMO ELECTRIC INDUSTRIES Ltd 6 Jan 1971 [26 Jan 1970 1 Feb 1970] 615/71 Headings H4A and H4L A leaky coaxial cable has in its outer conductor a radiating slot array in which each slot is arranged periodically at a fixed axial interval, or integral multiple thereof, and in which the shapes or sizes or other radiation factors of the slots are changed discretely from one slot to another in another periodicity. A substantially sinusoidal variation of radiation intensity is obtained along the cable, a plurality of slots being comprised in each half of said other periods. As described, a leaky coaxial cable comprises an inner conductor 1, and an outer conductor 2, equal length straight slots 4 1 , 4 2 ... &c. being cut in the latter at regular pitch intervals p 0 . In order to obtain a substantially sinusoidal distribution of radiation intensity over each section p of eight pitch intervals p 0 the slots therein are rotated by discrete amounts one after the other. Thus, considering the slots 4 1 to 4 9 , the slots 4 1 , 4 5 , 4 9 corresponding to zero values of radiation intensity are parallel to the axis of the cable. The slots 4 2 , 4 7 are rotated by maximum amounts in opposite senses, corresponding respectively to the positive and negative maxima of the said sinusoidal distribution. The slots 4 2 , 4 4 and 4 6 , 4 8 are similarly rotated, by lesser amounts. In a second embodiment the ineffective slots 4 1 , 4 5 , 4 9 are omitted (Fig. 5, not shown) and this applies for the equivalent slots in all other embodiments. In a third embodiment straight slots which are equally inclined to the axis but which have different lengths are used (Fig. 6, not shown), and in a fourth embodiment straight slots having differing lengths and inclinations are used (Fig. 7, not shown). A fifth embodiment features the use of folded line-shaped slots having portions 5, 6, Fig. 8, respectively perpendicular to and parallel to the axis, and of differing sizes, to obtain the required sinusoidal distribution of radiation intensity. In a sixth embodiment folded lineshaped slots of differing sizes are also used, but are angularly displaced by differing amounts relative to the axis (Fig. 9, not shown). It is stated that the cables described have broad hand characteristics particularly suitable for vehicular communication systems.