Patent GB-673679-A (GB)
Title: Improvements in or relating to direction finding receivers
IPC: H01Q21/06
Filed: 1949-06-14
Abstract: 673,679. Radio direction-finding. SADIR CARPENTIER: June 14, 1949 [June 14, 1948; June 16, 1948; June 16, 1948], Nos. 15866/49, 15866/49, and 15867/49. Class 40 (vii). A rotatable radio direction-finding system of the dipole Adcock type comprises two spaced dipoles and at least one further dipole off the plane of the first two, the whole aerial array being rotatable as a unit and the dipoles being associated with at least one receiver by lines of such electrical lengths as to give zero voltage at the receiver, or all the receivers, only when the azimuth of the incoming signal is in a predetermined relationship with respect to the aerial system. In a first embodiment (Fig. 3) four dipoles and two receivers are used. The first two dipoles A and B are symmetrically connected to receiver E to give a null when they are broadside on to an incoming signal but an ambiguity of 180 degrees remains. The two supplementary dipoles CD, preferably but not essentially situated in a plane at right angles to the plane containing the aerials A and B, are connected by lines F and G of unequal electrical length to a second receiver R, a null being obtained in one but not the other position in which the input to receiver E is a null. Indicator S shows when the double null occurs. The difference in the delay in the two lines F and G must be different from 180 degrees and is, with advantage, made approximately 90 degrees of electrical angle. In a variation of this embodiment the pairs of dipoles AB and CD are connected as described in Specification 662,576, Fig. 4 (not shown), the method of operation is the same. Provided that aerial C is not,in line with aerials A and B the functions of aerials B and D may be combined. Fig. 6 shows such a system wherein 1, 2 is dipole A; 3, 4 dipole B; and 5, 6 dipole C, which is preferably at the vertix of an isosceles triangle ABC. The connections shown are based on the disclosure of the abovementioned Specification, lines 7, 8 and 9, 10 being of the same length and giving null conditions with 180 degrees bearing ambiguity and receiver E, whilst line 11, 12, differing in electrical length from the others, and interconnected as shown with aerial B gives a null at receiver R at one but not the other null position for receiver E. In other embodiments three aerials and one receiver are used. In these embodiments the dipoles feed the receiver through lines of unequal lengths so chosen that the voltages at the receiver ends thereof have phase differences of 120 degrees in the (unambiguous) null position. The physical aerial layout may be the same as that of the Fig. 6 embodiment, the aerials being connected to the receiver in parallel, Fig. 9 (not shown), or they may be connected in series in a manner based on the disclosure of the above-mentioned Specification, Fig. 10 (not shown). It is pointed out that with systems according to the invention spacing of the aerials A and B may be greater than half a wavelength without ambiguity arising and that larger separations give increased accuracy. Specification 130,490, [Class 40 (ii)], also is referred to.