GB640152A - Antenna system - Google Patents

Abstract

640,152. Radio aerials. BENDIX AVIATION CORPORATION. Nov. 22, 1946, No. 34746. Convention date, Jan. 2. [Class 40 (vii)] An antenna system comprises means forming a ground plane, a horizontally extending, circular, plane member spaced less than a quarter wavelength from said ground plane at the mean frequency of the system, and a co-axial uniform cylindrical member between the plane and the circular member which is electrically interrupted at a point spaced from the circular member and fed at the interruption, which is so positioned that the input impedance of the antenna matches the characteristic impedance of the line. The antenna is of particular value where the height is limited to less than a quarter of the operating wavelength by space considerations as, for example, in vehicle mounted equipment and it may also be used over a broad frequency band without undue difficulties in matching. In one embodiment, Fig. 3, the ground plane 10 may be a large conductive sheet or a plate of quarter wavelength radius at the mean operating frequency. A composite hollow cylinder composed of conducting segments 11 and 28 separated by a short insulating section 12 is mounted over an aperture in the ground plane and is energized by a co-axial feeder passing therethrough. The length of the composite cylinder is considerably less than a quarter wavelength. Disc 14 is mounted on top of element 28, its radius being such that together with the length of the composite cylinder a quarter wavelength antenna is formed. The position of the segment 12 at which point the antenna is energized depends on the matching impedance required. If the height of the antenna is still further reduced so that the load presented to the feed line 15 is capacitive a shorted stub may be connected across the feed points to provide an inductive reactance to counterbalance the capacitive reactance of the system. The Specification as open to inspection under Sect. 91 comprises also an embodiment (Fig. 4, (Cancelled), not shown), in which segment 28 is omitted and insulating segment 12 is in contact with disc 14. Fig. 5, (Cancelled) (not shown), shows the arrangement of a compensating shorting stub under such circumstances. This subject-matter does not appear in the Specification as accepted.