GB987519A - Circuit arrangement for regulating the frequency or phase of an oscillator - Google Patents

Abstract

987,519. Automatic frequency and phase control systems. STANDARD TELEPHONES & CABLES Ltd. May 3, 1963 [May 18, 1962], No. 17538/63. Heading H3A. The remanence of a transfluxor is used for storing the control voltage in a retro-active frequency or phase control system, if the synchronizing source fades, the control voltage being always present since derived by rectifying an A.C. or pulse voltage applied to an output winding of the transfluxor. As shown, an increasing magnetizing current is applied to the input winding of the transfluxor 7 from a cathode follower 5, due to the discharge of a time constant grid circuit 19, 18, 20, 21, 22 which is initially negatively charged from a source U to block the tube 5 (and the transfluxor 7 initially magnetized by the same source U). Output voltage - U R from the transfluxor is used for controlling the frequency or phase of one frequency input F 0 to the discriminator but on phase or frequency synchronism of the oscillator and synchronizing frequencies, F 0 , F S being achieved a negative voltage is produced from discriminator 1 and again blocks tube 5, so that the control voltage - U R ceases to increase. Any subsequent drift between F 0 , F S removes this blocking voltage from tube 5 so that the control voltage - U R increases until synchronism is restored, but if this increasing same polarity of - U R fails to produce synchronism a value of the cathode current of tube 5 is reached at which relay A and switches a 1 , a 2 are energized and the negative bias source - U again applied to tube 5 and the transfluxor 7 to re-set it. Relay A then falls back and the control voltage - U R again starts to increase with the same polarity as before but from a lower minimum value, until the correct control value of - U R is reached, whereupon, as before, tube 5 is again blocked and the sweep of - U R ceases. The control voltage - U R may be centred about a zero value by adding positive voltage from a rectifier 16. Alternatively each energization of relay A and erase of the transfluxor may, by further relays, reverse the polarity of the control voltage ŒU R , or input current to the transfluxor, or this reversal may be effected by otherwise detecting the sense of the frequency error. A voltage divider 21, 22 may apply a portion of the output of the blocking voltage from stage 1 to the control voltage - U R (or ŒU R ), to compensate for the removal of current from the transfluxor input winding. The frequency or phase discriminator may also apply its output directly to the oscillator as a fine control. The transfluxor alternatively may itself control the oscillator, by its output winding being included in series with the oscillator coil.