| 摘要 |
862,151. Radio direction finding. TELEFUNKEN G.m.b.H. Dec. 8, 1959 [Dec. 13, 1958 ; Feb. 5, 1959], No. 41685/59. Class 40(7) In order to provide an Adcock directionfinding installation effective over a wide frequency range two Adcock aerial systems having different base lengths are arranged concentrically. Errors due to the effect of the outer system elements on those of the inner system are avoided, according to the invention, by providing twice the number of elements in the outer system as there are in the inner system and positioning each inner system element on the line bisecting the angle subtended at the centre by an adjacent outer aerial pair. The errors due to the two members of the pair acting as parasitic elements cancel at the inner aerial element. For directionfinding the two elements of each outer aerial pair are connected in parallel. Fig. 2 shows an installation having six inner system elements 10-15 inclusive evenly spaced round a central receiving installation 16 and coupled to it, as indicated for element 11 only, at 17. The outer system elements 18-29 inclusive are also evenly spaced round the central installation at a greater radius and, as indicated for the elements 10, 18 and 19, each inner element is angularly mid-way between a pair of outer elements. The parallel connection between a pair of outer aerial elements is indicated for elements 24, 25. The elements of the aerial system not in use at a given time are advantageously grounded and the feeders disconnected at both their ends. Instead of disconnecting the feeders, they may be provided at the aerial element ends with filters rejecting the frequencies accepted by the other system and at the receiver end with an impedance matching termination. Fig. 3 shows this form of coupling for a typical outer system element designated 30. The element is coupled to ground through a parallel tuned filter circuit 31, 32, 33 and the primary of coupling transformer 34. The feeder from the transformer secondary provides one input to a combining circuit 36, also fed from the other element of the pair, and the combined output is passed to co-ordinate transformer 37. The cartesian coordinate output signals may be fed by switch 40 to a cathode-ray tube indicator 43 or, when this is connected to the other aerial system, to dummy load resistors 44. The switches may also be arranged to enable the aerial systems each simultaneously to feed its own direction-finding receiver. |
