GB586080A - Shielded loop antenna - Google Patents

Abstract

586,080. Aerials. STANDARD TELEPHONES & CABLES, Ltd. Nov. 2, 1944, No. 21460. Convention date, Nov. 6, 1943. [Class 40 (v)] A shielded antenna for producing a substantially circular radiation pattern has four co-planar radiating members 6, 8, 10, 12, consisting of co-axial conductors about a quarter of the operating wavelength long arranged as a square or other symmetrical closed pattern. Adjacent ends of the radiating members are separated by small gaps 32. Four supporting arms 14, 15, 16, 17 are connected to junction boxes 20 inserted at the centre of each of the radiating members and at their inner ends to a central junction box 18 supported on a mast which may be the shielded dual transmission line feeding the antenna. Adjacent halves of radiating members, e.g. of members 8 and 10 contain inner conductors 26 and 28 respectively which are connected across the gap between them. The supporting arms each contain two conductors ; for example conductors 22 in 15 and 34 in 16, conductors 22 being joined one to conductor 26 and one to the other half of the inner conductor in radiator 8, the connections for 34 being similarly arranged. Lines 34 and the lines in arm 14 are joined in the box 18 and the junction is fed from the dual transmission line ; the lines in arm 14 being crossed so that current flows in the same direction round the whole Figure. Lines 22 and also the lines in arm 17 are terminated in inductive reactances mounted in the junction box 18, the dimensions of the system being such that these inductances may be regarded as equivalent to a capacitive reactance between the inner conductor and the shield at the gaps, thus giving the effect of a loaded line and producing a substantially circular radiation pattern. The inductance terminating lines 22 is set so that the impedance terminating line 28 is purely resistive and the other inductance for an equivalent condition. The inductive reactances at the end of arms 15 and 17 may he variable inductance coils or any other suitable arrangement, e.g. sliding shorts. Specifications 538,036 and 550,009 are referred to.