Patent GB-628747-A (GB)
Title: Improvements in or relating to radio frequency transmitting apparatus
IPC: G01S1/30
Filed: 1946-08-21
Abstract: 628,747. Automatic phase control systems. O'BRIEN, W. J. Aug. 21, 1946, No. 24981. Convention date, Aug. 27, 1945. [Class 38 (iv)] [Also in Group XL (c)] Relates to a system in which the phase relation between continuous radio transmissions from spaced points is used for navigational purposes. According to the invention a slave station receives a signal transmitted from the main station and continuously transmits at an unlike, but harmonically related frequency, and a phase controller at the slave station is used to maintain a fixed multiple phase relation between the two transmissions. Fig. 2 shows the master transmitter A which transmits a continuous wave at a frequency for example of 60 kc/s. and the equipment at a slave station B, which is geographically spaced from A. The signal from A is received at B on loop 17, and is then passed through amplifier and frequency divider 19, phase controller 20, power amplifier 21 and frequency multiplier and amplifier 16 to transmitting aerial 14, the frequency through the phase controller being at 30 kc/s. and the final transmission being at 90 kc/s. The outgoing transmission from B is also picked up by a loop 28 and passed through a frequency doubler to phase discriminator 22, which is also fed, via a frequency trebler, with energy from the receiving loop 17. The phase discriminator compares these two signals, and supplies a control voltage to vary the phase shift produced by phase controller 20, so as to maintain a constant phase relation between the two transmissions. The output from phase discriminator 22 may also be applied to a phase indicator 33. A "pip". generator 34, which generates a series of harmonics in fixed multiple phase relationship, may be connected to the phase discriminator circuit to provide a preset indication on indicator 33 for checking purposes. The signals from stations A and B are received at some mobile station, and the phase of these signals, referred to the least common multiple of the two frequencies (i.e. 180 kc/s.), is compared. The lines of equal phase difference form a field pattern over the area, and may be used for navigation. One or more other slave stations, operating at different, but harmonically related frequencies, may also be provided. Fig. 3 shows a circuit suitable for the phase controller unit 20. The output from divider. 19, Fig. 2, is applied to the primary of transformer 37, and thence to amplifier valve 64. The tuned secondary windings 39 and 59 of transformer 37 are associated with reactancevalves 47 and 60, the grids of which are fed with voltages at 90 degrees phase difference from their anode voltages by means of networks 53, 54, 55 and 61, 62, 63 respectively. The circuit comprising valves 47 and 60 effectively controls the phase of the input to valve 64, the output from which is applied via manual phase adjusting means 67 to leads 74 and 75 which are connected to power amplifier 21 of Fig. 2. The reactance effect of valves 47 and 60 is controlled by means of a voltage from the phase discriminator, which is used to bias the grids through resistance 56 and thus vary the mutual conductance of the valves. Specifications 620,479, 620,481, [Group XL (c)], 620,507, [Group XXXVI], 625,983 and 628,125, [both in Group XL (c)], are referred to.