GB494801A - Antenna network particularly applicable to systems for radio guiding of moving vehicles - Google Patents

Abstract

494,801. Directive wireless systems. STANDARD TELEPHONES & CABLES, Ltd. Dec. 3, 1937, No. 33558. Convention date, Dec. 31, 1936. [Class 40 (v)] In a directional aerial system in which the radiation characteristic of a main aerial is oscillated by means of a plurality of conductors arranged to function alternately as directors and reflectors by changing the sign of ances are cancelled and the conductors have no directing influence during the switching period. In Fig. 1 a fixed radiation characteristic having a suitable front to rear ratio is produced by the main aerial A, the two directors D1, D2 and the reflector R1. The two conductors R2, D3 have the form B, B<1>, Fig. 2, and are each spaced a quarter wavelength from the aerial A and are caused to act alternately as reflectors and directors by relay switches R. When the switch R is open the conductor B, B<1> is inductive at the operating wavelength of the aerial A and acts as a reflector ; whereas when the switch R is closed the inductance L is short circuited and the conductor B, B<1> reacts as a capacity, giving the effect of a director. Owing to the retardation of the relays operating the switches R, the two conductors tend to operate simultaneously either as reflectors or directors during switching, thus causing a sudden change in the magnitude of the emitted radiation which is heard as a key click in the receiver. This is prevented by connecting the two conductors R2, D3 (shown as B, B<1>, C, C<1> in Fig. 8) at their electrical centres to a transmission line X,Y having a length equal to half a wavelength. The impedance of the conductor C, Cl seen from the end Y is an inductance and from the end X is a capacity. Under these conditions no current flows and the line does not modify the normal operation of the conductors. If the two conductors operate simultaneously as reflectors or directors during switching a current flows in the line X, Y and eliminates the effects of the two conductors thus eliminating key clicks. According to the Specification as open to inspection under Sect. 91 the phase of the transverse radiation may be maintained constant by feeding the lateral conductors and the phase of the longitudinal field is changed by making the main aerial A or its directors D1, D2 or reflector R1 of the form showing in Fig. 2, in which case the keyed conductors may be fed from the same source as the lateral conductors. The arrangement may also be used to vary the angle of transmission or reception of a directional system and a number of lateral systems may be provided to increase the number of possible angles. This subject-matter does not appear in the Specification as accepted.