GB1406141A - Antenna assembly - Google Patents

Abstract

1406141 Aerials BALL BROS RESEARCH CORP 2 Jan 1973 174/73 Heading H4A The invention is concerned with an aerial arrangement for a propelled vehicle, such as a missile, in which a conductive cylindrical element of greater diameter than the body of said vehicle is positioned thereabout, and is connected thereto at one end to define a coaxial cavity which is open at one end and closed at the other. Electrical signal feed means are connected to the open end of the cavity at either one point or at a plurality of points which are equally spaced around the periphery. The invention also includes an aerial arrangement of a coaxial cavity which is open at one end and closed at the other, and which is fed with an electrical signal at the open end by means connected to a plurality of points which are equally spaced around the periphery. As described, a missile 12, Fig. 1, has a metallic cylindrical body 14, which is excited as an asymmetric wide band dipole by means of an annular slot element 10, located near the nose portion 15. Said element 10 comprises a conductive ring 16, Fig. 2, which is uniformly spaced from the body 14 by insulating material 18 (e.g. P.T.F.E.), and which at its forward end is fixed to, and is closed by a conductive ring member 22. Said member 22 is secured to the body 14 by screws 23, and is of substantially triangular cross-section to reduce air drag. The annular cavity so formed has a depth equivalent to a quarter wavelength at the operating carrier frequency, and it is excited at a plurality (e.g. fourteen) of equi-spaced points around its perimeter by means of coaxial lines, such as 30, 32, which are fed from a signal source 25 by a power divider 28. The spacing between a pair of feed points may be approximately one wavelength at the said frequency. As is shown in respect of the line 30, a coaxial jack 44 is provided at each feed point, the outer member 52 thereof being mounted inside the body 14, and the inner member 50 thereof being extended to the ring 16. At the end of the outer conductor 35 of the line 30 a ring 40 is soldered on, and this is clamped to the member 52 by means of a gland nut 42. The end of the inner conductor 34 of the line 30 has a sleeve 45 which receives the inner member 50 of the jack 44. The radiation pattern obtainable approximates to isotropic, apart from deep nulls fore and aft (Fig. 4, not shown).