GB1452017A - Radiating coaxial cable - Google Patents

Abstract

1452017 Aerials TIMES WIRE & CABLE CO 20 Sept 1974 [25 Sept 1973] 41086/74 Heading H4A A radiating high frequency transmitting cable comprises at least one centre conductor; a solid dielectric material layer enclosing the conductor or conductors; at least one field perturbing element with electrical properties different from those of the dielectric layer embedded a predetermined amount in the surface of the dielectric layer so that a major portion of its length is angularly oriented with respect to the centre conductor or conductors, and an outer apertured conductor and radiation shield element enclosing the dielectric layer and field perturbing element for at least a portion of the length of the cable and being in contact with the field perturbing element, the aperture of the shield element leaving at least a portion of the field perturbing element and adjacent dielectric layer unshielded in an area of the cable covered by the shield element. As described, a single centre conductor 1 is provided with an insulating surround 2 of polythene or other suitable dielectric material. The field perturbing element 3 comprises one or more strands of aluminium wire coiled about, and embedded in, the surface of the insulation 2. In one embodiment an outer shield 7, Fig. 3, of thin aluminium foil is tightly wrapped around the cable, and provides a longitudinally extending radiating slot 8, which is crossed by successive turns of the element 3. An overall insulating sheathing may be provided. It is stated that the effect of the field perturbing element is to enhance radiation from the slot. In order to level up the intensity of radiation along the cable, the winding pitch of the perturbing element and/or its degree of embedment in the insulation may be systematically varied. Instead of a continuous radiating slot, an array of slots may be provided, each slot being crossed by the field perturbing element. In one embodiment, the outer shield is continuous save for an array of longitudinally disposed, spaced apart, rectangular slots (Fig. 7, not shown). In another embodiment, slots are formed at intervals in a conductive tape, which is then close wrapped over the perturbing element on the surface of the cable insulation. An array of angularly disposed slots is thus produced (Fig. 8, not shown). In another embodiment, the cable of Fig. 3, is further provided with a spirally wound conductive tape 10, Fig. 6, over the shield 7, whereby an array of slots is formed from the continuous slot 8. As is shown in Fig. 9, a loosely braided or discontinuous outer shield 15, can provide openings 16 which act as an array of slots.