GB708008A - Improvements in or relating to folded slot aerials - Google Patents

Abstract

708,008. Aerials. NATIONAL RESEARCH DEVELOPMENT CORPORATION. June 5, 1952 [June 20, 1951], No. 14678/51. Class 40 (7) Relates to folded slot aerials of the type comprising an elongated aperture 1 in a conducting surface 2 enclosing a centre conductor 3 disposed substantially in the plane of the conducting surface and having adjacent feed points A and B located on the centre conductor and the boundary of the slot respectively. According to the present invention the bandwidth of such an aerial is increased by making the reactancefrequency characteristic of the impedance looking in at the feed point towards the left-hand of the slot different from that looking in towards the right-hand. This is effected by marking the aerial unsymmetrical with respect to the feed points by (1) displacing the feed points a distance l from the centre as shown in Fig. 3, (2) filling the slot on one side of the feed points with dielectric, Fig. 4 (not shown), (3) marking the two portions of the centre conductor of different width, Fig. 10 (not shown), (4) marking the transverse dimensions of the slot different, Fig. 5 (not shown), (5) inserting series lumped or distributed reactance in one portion of the centre conductor, Fig. 6 (not shown), which may be extended to join the end boundary of the slot, Fig. 7 (not shown), (6) connecting one end of the centre conductor to the adjacent end boundary of the slot directly, Fig. 8 (not shown), or via a reactance X, Fig. 3, (7) connecting one or both ends of the centre conductor to the surface 2 beyond the end boundary of the slot, Fig. 9, (not shown). Any suitable combination of the above methods may be employed and in any of the embodiments the impedance may be adjusted by displacing the centre conductor from the centre of the slot as illustrated in Fig. 13, which shows a slot backed by a cavity resonator whose boundaries are indicated at 5, the slot being folded to provide a non-directional radiation pattern. Fig. 11 and Fig. 12 (not shown) illustrate a slot cut in the conductor skin 2 of an aircraft and covered on the inside with a sheet of dielectric 4, the centre conductor comprising two portions 3A and 3B of unequal length and thickness, the thick portion 3A being in contact with the dielectric and the thin portion 3B being spaced therefrom by supports 4B so that the effective dielectric constants for the two portions of the central conductor is also different.