GB760388A - Improvements in or relating to radio antennae - Google Patents

Abstract

760,388. Directive radio systems. DECCA RECORD CO., Ltd. Dec. 24, 1953, No. 19441/55. Divided out of 760,317. Class 40(7) An aerial system has a ceramic dielectric element or elements, of the type which has a dielectric constant that can be controlled by establishing an electric potential gradient within the material, placed in the antenna field and means are provided for applying an adjustable control potential or potentials to the dielectric for adjusting the relative phases of different parts of the field. The dielectric elements may be materials containing barium titanate or certain other titanates and also certain metallic oxides. The electric potential gradient may be applied to the dielectric material in a number of ways such as are described in Specification 760,317, (see also Figs 1 to 4, (not shown). The more important of these comprise arranging strips at right angles to the electric vector of the field on opposite sides of a thin sheet thereof. Alternatively the strips may be on one side of the sheet only, the potential being applied between adjacent strips. In a different method of application chambers of ionized gas are arranged on each side of the dielectric and coupling effected through them. As the dielectric constant of the material is high, matching problems have to be taken into consideration. The matching arrangements may comprise one or more pieces of material having a dielectric constant or constants of a value or values intermediate between that of the dielectric element and the surrounding medium. In certain circumstances wedge or inverse wedge shaped pieces of dielectric material can be used for matching (Figs. 5, 6 and 7, not shown). One aerial system according to the invention comprises a parabolic reflector 130 fed from a horn primary element 131. In front of the horn are arranged two sheets of dielectric material 132 and 133. Means are provided for applying two differing control potentials to the dielectric elements in alteration to deflect the aerial beam between two directions making equal angles with the normal to the reflector mouth. In a modification (Fig. 10 not shown) the sheets of dielectric each extend over half the length of the reflector mouth and modify the phase of the radiation therefrom. The width of the beam radiated may be adjusted by using a primary element horn 140 with a wedge 141 of dielectric material in it. The phase distribution across the mouth of the horn of the energy radiated can be altered by applying differing potentials to the dielectric and the beam width thus modified. Switching of the radiated beam may be achieved by the use of two dielectric wedges 146, 147, placed in the horn mouth and having switched control potentials., In the case of a directional array comprising a plurality of spaced slots in the side of a waveguide a dielectric strip element may be arranged along the guide, parallel to either face or diagonally in the case of a square guide, and control potentials applied to the strip so as to vary the relative phases of the signals radiated from the various slots.