GB1345274A - Circuit arrangement for generating a phase-shiftable voltage - Google Patents

Abstract

1345274 Phase shifting BRUKER PHYSIK AG 20 July 1971 [30 July 1970] 34044/71 Heading H2F [Also in Division H3] A phase shifting circuit comprises a device 5, Fig. 1, for generating from a reference voltage U B at least 3 auxiliary voltages having a certain, constant phase relationship, a resistor 14 having taps 15-18 to which these voltages are fed as shown, the resistance between each tap being proportional to the phase relationship of the applied voltages, the resistor having a wiper 19 connected to an output 20, 21 from which a voltage having any fixed phase relationship with U B may be obtained. The device 5 is adapted to provide V auxiliary voltages in quadrature substantially independent of the frequency of the input voltage. As shown, Fig. 2, the input 2, 4 is taken to two potential dividers 24, 25 in parallel each comprising resistances 26, 27 and variable reactances 28, 29, preferably capacitance diodes or controllable inductors, the resistive component 26 of divider 24 and the reactive component 29 of divider 25 being connected to the input 2. The outputs of the dividers are tapped at 30, 31 and used as inputs to buffer amplifiers 34, 35 having outputs 36, 37 taken to primaries 42, 43 of output transformers 40, 41. In operation at a particular frequency, the resistive and reactive components of both dividers are adjusted for equality such that the phases of the voltages at 30, 31 are 45‹ with respect to U B and 90‹ with respect to each other. The secondaries 44, 45 of transformers 40, 41 are centre-tapped to earth and 4 voltages in quadrature may be tapped at points 6, 7, 8, 9. In the event of the frequency of U B changing the reactive components will also change and the phase and magnitude of the voltages at 30, 31 will change in opposite directions. The outputs of amplifiers 34, 35 are taken via diodes 48, 49 and resistances 50, 51 as input to an automatic gain controlled amplifier 52 which thus is operated by the difference in voltage at 36, 37. The output 53 is proportional to this difference and is fed-back to alter the capacitance or inductance of both reactances causing change in the voltages at 30, 31 again in the opposite directions until near equality is reached, the reactive and resistive components again being equal to restore phase quadrature at points 6-9 despite the change in frequency.