Radio Interferometer System

1,191,831. Radio direction-finders. MULLARD Ltd. 21 March, 1967 [21 Dec., 1965], No.54085/65. Heading H4D. [Also in Division G4] In a radio direction-finder utilizing two interferometers of different apertures a respective discriminator digitizes the output of each interferometer into a code in which at least for the narrower interferometer only one digit at a time undergoes a transition for values progressing in a given sense of the signal phase difference (and hence of bearing) and logic means is so arranged to combine the outputs of the discriminators in computing a digital final unambiguous direction-denotive output that the information contained in a digit of the discriminator output of the narrower interferometer is not used in computing the final output when the input phase difference to that discriminator is within a designated value of an input phase difference corresponding to a transit of that digit. More than two interferometers may be employed and the invention is applicable to azimuth or elevation determination. If the amplitudes and phases of the two aerials of an interferometer are a, O and b, # respectively a hybrid junction associated with diode square-law detectors and a subtractor gives an output of amplitude 4a b cos #, Fig. 2 (not shown) and by extending this basic arrangement, Fig. 4, outputs E1 = 4a b cos # and F1 = - 4a b sin # can be obtained. Further outputs by similar means not shown are G1 = 4a b cos (#+#/4)/#2 and H1 = 4a b cos (#+3#/4)#2. The zero crossings of outputs E1, F1, G1, H1 divide the range 0