Video detection circuit

Claim 2

A waveshaping circuit for conditioning a signal in which data transitions occur at varying amplitude levels, comprising: an adjustable attenuator responsive to a signal to be conditioned to produce an attenuated signal having an amplItude in accordance with the extent of said adjustment, first circuit means responsive to said attenuated signal for adjusting said attenuator in accordance with gradual changes in its average amplitude to keep the average amplitude of said attenuated signal relatively constant, second circuit means responsive to said attenuated signal for producing a first signal corresponding to rapid transitions in said attenuated signal, means responsive to said attenuated signal for producing a second signal corresponding to at least the gradual transitions of said attenuated output signal, and summing means responsive to said first and second signals for producing a combined signal in accordance with the sum of said first and second signals.

Claim 3

The apparatus of claim 1, further comprising: level detecting means responsive to said combined signal for producing an output signal having a first amplitude for each portion of said combined signal below a predetermined amplitude and a second amplitude for each portion of said combined signal above said predetermined amplitude.

Claim 4

The apparatus of claim 1, in which said first circuit means comprises: a low pass filter and said second circuit means comprises a high pass filter.

Claim 5

The apparatus of claim 3, in which said means for producing said second signal comprises: circuit means connected between said low pass filter and said summing means.

Claim 6

The apparatus of claim 1, in which said first circuit means comprises: a low pass filter, and said second circuit means comprises a band pass filter for rejecting frequencies above and below the range in which information transitions in the signal to be conditioned occur.

Claim 7

The apparatus of claim 5, in which said means for producing said second signal comprises: wide band circuit means connected between said attenuator and said summing means.

Claim 8

The apparatus of claim 6, in which said wide band circuit means comprises: a low pass filter having a cutoff frequency substantially above the upper cutoff frequency of said band-pass filter.

Claim 9

In combination, variable gain amplifying means responsive to a first applied signal for amplifying a second applied signal an amount determined by said first applied signal to produce an amplified signal, a low pass filter means connected to said amplifying means and responsive to said amplified signal to apply a first signal to said amplifying means to vary the gain of said amplifying means and reduce low frequency excursions of said amplified signal, summing means responsive to two applied signals for producing an output signal in accordance with their sum, differentiating means responsive to said amplified signal for applying a first signal to said summing means in accordance with high frequency fluctuations in said amplified signal, and circuit means for applying said amplified signal to said summing means.

Claim 10

In combination, variable gain amplifying means responsive to a first applied signal for amplifying a second applied signal an amount determined by said first applied signal to produce an amplified signal, a low pass filter means connected to said amplifying means and responsive to said amplified signal to apply a first signal to said amplifying means to vary the gain of said amplifying means and reduce low frequency excursions of said amplified signal, summing means responsive to two applied signals for producing an output signal in accordance with their sum, differentiating means responsive to said amplified signal for applying a first signal to said summing means in accordance with high frequency fluctuations in said amplified signal, and circuit means for applying said amplified signal to said summing means.

Claim 11

The apparatus of claim 8, further comprising: level detecting means controlled by said summing means for producing an output signal having a first or a second amplitude according as the amplitude of said output signal is above or below a predetermined value, respectively.

Claim 12

In combination, a variable gain amplifier responsive to an applied input signal to produce an amplified output signal, a low pass filter having a cutoff at a frequency f1 connected in an automatic gain control loop around said amplifier, a band-pass filter having a passband between frequencies f2, f2>f1, and f3, f3>f2, connected to said amplifier for producing an output signal in accordance with the components of the amplifier output signal in said pass band, and a summing circuit connected to said band-pass filter and said amplifier for producing an output signal in accordance with the sum of their output signals.

Claim 13

In combination, a variable gain amplifier responsive to an applied input signal to produce an amplified output signal, a low pass filter having a cutoff at a frequency f1 connected in an automatic gain control loop around said amplifier, a band-pass filter having a passband between frequencies f2, f2>f1, and f3, f3>f2, connected to said amplifier for producing an output signal in accordance with the components of the amplifier output signal in said pass band, and a summing circuit connected to said band-pass filter and said amplifier for producing an output signal in accordance with the sum of their output signals.

Claim 14

The apparatus of claim 10, further compriSing: a level detector connected to said summing circuit for producing a signal having a first or a second value according as the output signal from said summing circuit is above or below a predetermined value, respectively.

Claim 15

In combination, amplifying means comprising: an input terminal and an output terminal, said amplifying means further comprising a gain control circuit including a variable impedance adjustable to vary the gain between said input terminal and said output terminal, a low pass filter connected to said output terminal to produce a first signal corresponding to low frequency components of the output signal of said amplifier produced in response to an applied input signal, means responsive to said first signal for adjusting said variable impedance to stabilize the average level of the output signal of said amplifier, an active filter having an input terminal, an output terminal, and a response characteristic insensitive to frequencies passed by said low pass filter, means connecting the output terminal of said amplifying means to the input terminal of said active filter, and summing means connected between the output terminal of said amplifying means and the output terminal of said active filter to produce an output signal in accordance with the sum of their output signals.

Claim 16

In combination, amplifying means comprising: an input terminal and an output terminal, said amplifying means further comprising a gain control circuit including a variable impedance adjustable to vary the gain between said input terminal and said output terminal, a low pass filter connected to said output terminal to produce a first signal corresponding to low frequency components of the output signal of said amplifier produced in response to an applied input signal, means responsive to said first signal for adjusting said variable impedance to stabilize the average level of the output signal of said amplifier, an active filter having an input terminal, an output terminal, and a response characteristic insensitive to frequencies passed by said low pass filter, means connecting the output terminal of said amplifying means to the input terminal of said active filter, and summing means connected between the output terminal of said amplifying means and the output terminal of said active filter to produce an output signal in accordance with the sum of their output signals.

Claim 17

The apparatus of claim 12, further comprising: level detecting means connected to said summing means to produce a first or a second output signal level according as the output signal from said summing means is below or above a predetermined value, respectively.

Claim 18

The apparatus of claim 12, in which said active filter comprises: an amplifier and a differentiating circuit connected to said amplifier.

Claim 19

The apparatus of claim 12, in which said active filter comprises: a band-pass filter and an amplifier connected to said band-pass filter.

Claim 20

The apparatus of claim 12, in which said amplifying means comprises: an operational amplifier and an attenuator connected between said input terminal and said operational amplifier, said attenuator comprising a potential divider including a fixed impedance connected in series with said variable impedance.

Claim 21

The apparatus of claim 16, in which said fixed impedance comprises: at least one active component and exhibits a high impedance to the frequencies passed by said low pass filter and a low impedance to frequencies passed by said active filter.

Claim 22

The apparatus of claim 16, in which said variable impedance comprises: a field effect transistor.

Claim 23

The apparatus of claim 12, in which said amplifying means comprises: an amplifier and a gain determining impedance network connected to said amplifier, said network including said variable impedance connected in parallel with a fixed impedance, and said fixed impedance comprising a resistor and a capacitor connected in parallel.

Claim 24

The apparatus of claim 19, in which said variable impedance comprises: a field effect transistor.

Claim 25

In combination, a variable gain network responsive to a first applied signal to produce an output signal amplified to an extent dependent on a second applied signal, summing means responsive to a set of applied signals to produce an output signal in accordance with this sum, differentiating means connected between said network and said summing means to apply a first signal to said summing means, means for applying the output signal from said network to said summing means, a low pass filter responsive to the output signal from said network to produce a control signal, and means for applying said control signal as said second signal to said network.

Claim 26

In combination, a variable gain network responsive to a first applied signal to produce an output signal amplified to an extent dependent on a second applied signal, summing means responsive to a set of applied signals to produce an output signal in accordance with this sum, differentiating means connected between said network and said summing means to apply a first signal to said summing means, means for applying the output signal from said network to said summing means, a low pass filter responsive to the output signal from said network to produce a control signal, and means for applying said control signal as said second signal to said network.