GB1343142A - Automatic frequency control - Google Patents

Abstract

1343142 Automatic frequency control, frequency comparators MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 19 April 1971 [13 Feb 1970 (3) 9 March 1970 3 Sept 1970] 21604/71 Heading H3A In an automatic frequency control system, the controlled and reference signals F, S 0 are fed to a frequency comparator which produces a positive or negative a.f.c. pulse signal on one or other of two output terminals depending on whether F > S 0 or F < S 0 , the width of the pulses depending on the frequency difference. In the arrangement of Fig. 1, a sync. signal S 0 and a flyback signal F to be synchronized are shaped by inverters 3, 4, 5 to provide trains of positive going rectangular pulses S<SP>11</SP>, F<SP>1</SP>, Fig. 2, which are fed to NOR gates 8, 9 to produce signal X. The signal S<SP>11</SP> is also inverted at 6 and integrated at 7 to provide a signal S<SP>111</SP>1 which is fed together with the signal X to AND gate 10 which produces an output Y if an S<SP>11</SP> pulse leads an F<SP>1</SP> pulse. The X signal is also fed to gate 13 which inhibits passage of the signal X to output Z whenever an output Y exists. If an F<SP>1</SP> pulse leads an S<SP>11</SP> pulse, no Y output is produced to gate 13 is opened to give a Z output. Phase coincidence of F<SP>1</SP> and S<SP>11</SP> produces no X signal and hence no output occurs on either Y or Z. The lines Y, Z are connected to an integrator, Fig. 3, which provides the control signal and which has a variable time constant controlled by a signal P from Fig. 1. This signal P is applied to a peak detector 17 to provide a switching voltage for diode D 4 which switches R 3 C 3 in or out of circuit depending on the presence or absence of P. Figs. 5, 6 relate to a modification of the discriminator of Figs. 1, 2 which functions in a similar manner, but which employs a different arrangement of gates.