Sync stripper

Claim 2

Signal processing apparatus comprising: differential amplifying means having an input circuit and an output circuit, said differential amplifying means being responsive to application of an input signal to be processed and of a correction signal to its input circuit for producing in its output circuit a difference signal proportional to the difference between the input signal and the correction signal; and a feedback circuit connected between the output and input circuits of said differential amplifying means, said feedback circuit including sampling means for sampling the magnitude of the difference signal in synchronism with the input signal and being responsive to the difference signal for producing a correction signal proportional to the average value of the samples and for supplying this correction signal to the input circuit of said differential amplifying means, whereby portions of the difference signal are maintained at a fixed level in the output circuit of said differential amplifying means.

Claim 3

Signal processing apparatus as in claim 1 wherein said feedback circuit further includes: an amplifier connected to the output circuit of said differential amplifying means and responsive to the difference signal for supplying said samplIng means with an amplified difference signal to be sampled; and a filter connected to said sampling means and responsive to the samples taken of the amplified difference signal for supplying the input circuit of said differential amplifying means with the correction signal.

Claim 4

Signal processing apparatus as in claim 2 including a signal limiting circuit connected in the output circuit of said differential amplifying means to limit the amplitude of the difference signal.

Claim 5

Signal processing apparatus as in claim 3 including a signal divider connected to the input circuit of said differential amplifying means and activated in response to an input signal having an amplitude above a threshold level, whereby the range of difference signals that may be maintained at the fixed level in the output circuit of said differential amplifying means is increased.

Claim 6

Signal processing apparatus as in claim 2 including: a low-pass filter connected to the input circuit of said differential amplifying means to filter the input signal before it is supplied to the differential amplifying means; and a clipping circuit connected to the output circuit of said differential amplifying means to remove an undesired portion of the difference signal.

Claim 7

Signal processing apparatus as in claim 5 wherein means including said clipping circuit is connected to said sampling means and is responsive to the difference signal for driving said sampling means in synchronism with the input signal.

Claim 8

Signal processing apparatus as in claim 6 wherein said last-mentioned means includes: a separation circuit connected to said clipping circuit and responsive to the clipped signal therefrom for providing a signal including portions occurring in phase with and at the repetition rate of said portions of the input signal; and a trigger circuit connected to said separation circuit and responsive to at least some of said portions of the signal therefrom for driving said sampling means to sample portions of the amplified difference signal that are supplied to the sampling means in phase with and at the repetition rate of selected ones of said portions of the input signal.

Claim 9

Signal processing apparatus as in claim 6 wherein said differential amplifying means comprises: first and second transistors, each having base, emitter, and collector electrodes; and circuit means connecting said first and second transistors in a differential configuration with the base of said first transistor being connected to receive the input signal and the base of said second transistor being connected to receive the correction signal, said first and second transistors being responsive to the input signal and the correction signal for producing the difference signal at the collector of said first transistor.

Claim 10

Signal processing apparatus as in claim 8 wherein: a unidirectional conducting element is connected between the collectors of said first and second transistors, said unidirectional conducting element being poled to limit the amplitude of the difference signal produced at the collector of said first transistor; said apparatus includes a signal divider comprising a first resistive element connected for receiving the input signal, another unidirectional conducting element connected to said first resistive element, and a second resistive element connected between said other unidirectional conducting element and a source of reference potential; the base of said first transistor is connected to a point between said first resistive element and said other unidirectional conducting element; said apparatus includes circuit means for connecting the base of said second transistor to a point between said second resistive element and said other unidirectional conducting element; said other unidirectional conducting element is poled to activate said signal divider in response to an input signal having an amplitude above the threshold level of said other unidirectional conductiNg element; the amplifier of said feedback circuit has an input circuit connected to the collectors of said first and second transistors and has an output circuit connected to said sampling means; said sampling means comprises a gate activated in synchronism with the input signal; and the filter of said feedback circuit is connected between said gate and the base of said second transistor.

Claim 11

Signal processing apparatus as in claim 1 wherein said differential amplifying means comprises: first and second transistors, each having base, emitter, and collector electrodes; and circuit means connecting said first and second transistors in a differential configuration with the base of said first transistor being connected to receive the input signal and the base of said second transistor being connected to receive the correction signal, said first and second transistors being responsive to the input signal and the correction signal for producing the difference signal at the collector of said first transistor.

Claim 12

Signal processing apparatus as in claim 10 wherein a unidirectional conducting element is connected between the collectors of said first and second transistors, said unidirectional conducting element being poled to limit the amplitude of the difference signal produced at the collector of said first transistor.