GB803723A - Improvements in or relating to aircraft antenna - Google Patents

Abstract

803,723. Aerials; R.F. couplings. STANDARD TELEPHONES & CABLES, Ltd. Nov. 9, 1956, No. 34298/56. Class 40 (7). The invention relates to " notch " aerials for aircraft of the kind in which a metal skinned aerofoil is provided with a notch in an edge thereof which has a depth of less than a quarterwavelength at the mean operating frequency and a width of less than its depth. The notch is bounded within the aerofoil by two parallel plane conducting surfaces connected to the metal skin along the respective edges of the notch, the surfaces being joined over at least part of the length of the notch root. Such a notch has heretofore been proposed having a coaxial feeder connected across the parallel plane conducting surfaces and a tuning condenser connected between the same two surfaces (Fig. 2, not shown). In order to increase the bandwidth and avoid the necessity for tuning the aerial the present invention contemplates the introduction into the notch of a further plane conducting surface in parallel relationship with the two previously-mentioned and having its outermost end connected to one of them. Figs. 3A and 3B show one embodiment in midsection and plan respectively. In this embodiment 3 is the edge of the metal aerofoil 1 and the notch 2 is bounded by parallel conductive surfaces 4 and 5 connected together at the notch root by a further conductive member 6. According to the invention a plate 13 is introduced parallel to surfaces 4 and 5 and connected to surface 4 at its outer end by section 15. This plate considerably increases the transmission line path in the notch and thus the bandwidth. The feeder 8 may be either connected across the gap between surfaces 5 and 13, as shown, or between the surfaces 4 and 13 (Fig. 4, not shown). If the length of plate 13 required is sufficiently small it may be placed close to the root of the notch and connected to the surface 4 a considerable distance from the edge 3. It is then possible to connect the feeder 8 across the surfaces 4 and 5 at a point closer to the edge 3. Where, on the other hand, it is desired to increase the transmission line path very considerably the arrangement shown in Fig. 6 may be used ; the plate 13 in this case being turned up and back on itself as shown at 16.