The Grass Valley Group, Inc.

Graham-Patten Systems, Inc.

William L Rorden

Leon J Stanger

Birney D Dayton

A phase-locked loop circuit receives an input signal that has a predetermined frequency during a succession of symbol intervals and of which the phase during a given symbol interval is related to the phase during a reference interval by the angle 2n.pi./N, where N is a positive integer and n is an integer in the range from 0 to (N-1), and generates a reference signal of which the phase has a desired relationship to the phase of the input signal during the reference interval. The circuit comprises a controllable oscillator that is responsive to a control signal to generate the reference signal, the frequency of the reference signal being equal to the predetermined frequency when the value of the control signal is zero. The circuit also comprises a demodulator for generating a first signal representative of the sine of the phase of the input signal relative to the reference signal and for generating a second signal representative of the cosine of the phase of the input signal relative to the reference signal, and a function generator for receiving the first and second signals and generating the control signal such that when the phase of the input signal relative to the reference signal is equal to 2n.pi./N plus the phase of the input signal relative to the reference signal during the reference interval, the value of the control signal is zero and the first derivative of the value of the control signal with respect to phase of the input signal relative to the reference signal is positive.

Phase-locked loop circuit

A differential input receiver having normal and common mode impedance balanced inputs and a common mode rejection ratio approaching infinity is provided. The receiver includes a differential input operational amplifier across which is connected a fixed gain inverting amplifier. The fixed gain, inverting amplifier being connected in a feedback configuration across the differential input amplifier. Additionally, the values and ratios of the various resistors being selected to provide the balanced differential input and the substantially zero common mode gain of the receiver.

Differential amplifier having high common-mode rejection ratio

A circuit for reducing the effects of negative-going impulse noise in composite television video signals has on sync separators is disclosed. A variable output current source is used to supply rundown current to a dc restorer in a sync separator. A retriggerable monostable multivibrator is triggered by negative-going impulse spikes in the composite video signal. The output of this multivibrator is coupled to the current source to increase its output and therefore decrease the time required for the dc restorer to recover from the negative spike.

Growing community of inventors

Grass Valley, CA, United States of America

William L Rorden