Patent GB-776598-A (GB)
Title: Improvements in or relating to aerial systems and arrangements
IPC: H01Q21/26
Filed: 1955-12-14
Abstract: 776,598. Aerial systems. TELEFUNKEN GES. Dec. 14, 1955 [Jan. 25, 1955], No. 35889/55. Class 40(7). An aerial system providing a substantially uniform omnidirectional horizontal radiation and capable of maintaining a good impedance match over a wide band of frequencies consists of at least two vertically stacked, similar, aerial sections fed from a common feeder through sub-feeders one of which introduces a 90 degree phase shift relative to the other(s). The sections are so arranged that the effect of the phase shift is compensated for and the main radiation concentration directed in a substantially horizontal plane. Fig. 1 shows two aerial sections each comprised of crossed half-wavelength dipoles stacked one above the other. A 90 degree phase shift is introduced at 100 in the feed to the lower section which is rotated about its axis through an angle B to maintain the maximum radiation in a horizontal or nearly horizontal plane. Due to the phase shift any energy reflected back from one section reaches the main feeder in phase opposition to energy similarly reflected back from the other section and they balance out. As shown the main feeder is coupled to the sub-feeders 9 and 10 through a bridge circuit which extends the range over which cancellation occurs and provides a resistance 13 in which any reflected energy not cancelled out may be dissipated. The feeder 11 is coupled into the bridge through a transformer arangement 12. In the aerial sections one crossed dipole is fed with a 90 degree phase shift relative to the other and by closing the various phase shifters to give 90 degree phase shifts at slightly differing frequencies better wide-band effects can be obtained. The vertical spacing and angular displacement B should be chosen to obtain a well rounded polar-diagram. It is possible to arrange for each section of an aerial system to consist itself of two or more vertically stacked elements with a direction of maximum radiation which deviates slightly from the horizontal. The angular relationship of elements in each section can be arranged so that the radiation pattern in the horizontal plane is substantially circular. The crossed dipoles described give horizontally polarized energy but the radiation may be made vertically polarized by the use of helical aerials. It is also possible to use radiating units of the form in which the elements are arranged on a ring or polygon and carry currents of equal phase. The elements may be slots or dipoles, horizontally or vertically arranged. The lower section of a two-section aerial in such a case may be a unit with the elements arranged round a larger ring or polygon than the upper section to counteract the effect of the. 90 degree phase shift (Figs. 3 to 10, not shown). An aerial system consisting of two sections, each of six vertically stacked crossed dipoles and a similar system in which each half dipole is replaced by a " butterfly " element are described with reference to Fig. 11 (not shown). Means for feeding these systems from four transmitters over switch means are indicated schematically on the same Figure.