Patent GB-813058-A (GB)
Title: Radio direction finder
IPC: G01S3/14
Filed: 1956-05-09
Abstract: 813,058. Radio direction-finding. KO KUSAI DENSHIN DENWA KABUSHIKI KAISHA. May 9, 1956 [May 9, 1955 (2); Sept. 22, 1955; Oct. 8, 1955], No. 14447/56. Class 40 (7). In a radio direction-finder four bearing- dependent R.F. voltages Ea1, Ea2, Eb1 and Eb2 corresponding to the signals received by two orthogonal pairs of reversed cardiod directivity patterns E1, E3 and E2, E4, Fig. 10, are applied sequentially by electronic switches S and Sa through a single amplifier Ap1 to separate peak rectifying and capacitor-resistor storage circuits D1 ... D4 to give corresponding D.C. voltages ea1, ea2, eb1, eb2 and two A.C. signals of amplitude proportional to (Ea1- Ea2) and (Eb1-Eb2) respectively are derived from the L.F. oscillator Oc (frequency f) controlling the electronic switches and are applied to the Y and X plates of a C.R.T. B to give a linear trace whose inclination # is equal to the direction of arrival # of the received radio waves; the dotted portion of the trace is blanked out to provide an unambiguous indication by applying an output from the oscillator Oc to the grid of the C.R.T. through a half-wave rectifier D5 giving an output Fig. 2 (e) (full lines). The rectifiers D1 ... D4 may be linear or quadratic; in the former case the amplifier Pp1 may have a square-law characteristic. As shown in Fig. 1, the bearing-dependent R.F. voltages Ea1, Ea2, Eb1, Eb2 are produced by applying push-pull outputs EAD, - EAD and EBD, - EBD from two crossed Adcock aerials A1, A2 and B1, B2 or from two equivalent crossed loop aerials sequentially by switches S1, S3, S2, S4 to the amplifier Ap1 where they are combined with a 90 degree phase-shifted omnidirectional signal Es derived as shown by combining the outputs from the aerials A1, A2, B1, B2. In a modification, Fig. 4, the signal Ea1 is produced by combining the output EA1 from the aerial A1 in opposition with a signal eA2 obtained by phase-shifting the output EA2 from the aerial A2 at P1 by the amount # such that 2#d/# ### #, when d is the spacing between the aerials A1 and A2 and between the aerials B1 and B2. The signals Ea2, Eb1 and Eb2 are produced in a similar manner from the signals EA2, eA1; EB1, eB2 and EB2, eB1. The switches S and Sa are preferably triode valve switches, Figs. 5 and 6 (not shown), controlled by four-phase sine waves derived from a single phase output from the L.F. oscillator Oc, another output from said oscillator being modulated at F1 and F2 (Fig. 5, not shown), by the D.C. signals ea1, ea2, eb1, eb2 to give corresponding A.C. signals Va1, Va2, Vb1, Vb2, Figs. 2 (a) and (c). The signals Va1 and Va2 are combined differentially in the modulator F1 giving a resultant signal Ea = (Val - Va2), Fig. 2 (b), which is applied to the Y plate of the C.R.T. B and a corresponding signal Eb = (Vb1 - Vb2) from the modulator F2 is applied to the X deflector plates to produce the trace. In a modification, Fig. 6 (not shown), a square wave of frequency f and amplitude proportional to (Ea1 - Ea2) is produced by alternately applying the D.C. voltages ea1 and ea2 to an amplifier by means of a relay controlled by the oscillator Oc, the square wave being then differentiated by a C.R. network to give an exponential peaky waveform, Fig. 7 (not shown), which is applied to the Y plates of the C.R.T., a corresponding peaky waveform of amplitude proportional to (Eb1 - Eb2) being produced in a similar manner and applied to the X plates to give a resultant radial trace, Fig. 9, whose brightness decreases radially outwards along the trace; the dotted portion of the trace is blanked out as in Fig. 1.