GB890640A - Improvements in range and angular coordinates finder - Google Patents

Abstract

890,640. Alternating current transmission systems. ROBERTSHAW-FULTON CONTROLS CO. June 16, 1958 [June 28, 1957], No. 19204/58. Class 40 (4). [Also in Group XL (c)] In an infra-red direction finding system (see Group XL (c)), modulation signals derived from three phototransistor stages 120, 124, 420 are applied to respective vertical, range and horizontal channels and rectified outputs from the range channel amplifier 136 are applied to control the impedance of shunt networks comprising non-linear crystal diodes in the three channels to produce logarithmic input/output characteristics. Fig. 6 shows the block diagram corresponding to the circuit diagram of Figs. 7, 7a and 7b. The range channel comprises a cathode follower V4, Fig. 7, and an amplifier 136 (V5, V6, V7, Fig. 7a). One network comprising diodes 398, 400 is shunted across the input to the cathode follower V4, another network comprising diodes 414, 416 is shunted across the output from the cathode follower V4 and a D.C. control voltage applied across the diode pairs 398, 400 and 414, 416 is derived from an A.C. output from the amplifier 136 by means of a rectific unit 146 comprising a triode V8, Fig. 7a, transformer 362, Fig. 7b, and rectifiers 364, 366. A network comprising diodes 214, 212, Fig. 7, is shunted across the input to the vertical channel amplifier 128 (V2, V3, Fig. 7a) and a D.C. control voltage applied across the diodes 214, 212 is produced by applying an A.C. output from V7 of the range amplifier 136 through a valve V1, Fig. 7a, to rectifiers 182, 184, Fig. 7. The impedance of a similar network comprising diodes 448, 450, Fig. 7, in the horizontal channel is controlled in a corresponding manner.