Pre-emphasis network with variable time delay
AssigneeEagle Comtronics, Inc.
InventorDale W. Marland
Life of this patent
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Abstract
A pre-emphasis network used in a television signal jamming encoder has a variable gain tuned amplifier first stage and an attenuable notch filter and variable gain broadband amplifier second stage. The notch filter is tuned to a center frequency above the television signal intermediate frequency's visual carrier frequency resulting in 15 dB of increased pre-emphasis and a time delay which compensates for a time delay imparted by a decoding network upon decoding of a signal jammed by this encoder.
Claims18
An electronic circuit, comprising:
- an input terminal;
- a first amplifier, connected to said input terminal, for amplifying an input signal around a first center frequency, and for outputting a first amplified signal;
- a notch filter, including a first variable attenuating means, for attenuating and imparting a time delay to said first amplified signal, having a first end coupled to an output of said first amplifier and a second end connected to ground, said notch filter having a second center frequency higher than said first center frequency of said first amplifier;
- a second amplifier for amplifying the attenuated and time-delayed first amplified signal, said second amplifier having an input coupled to the output of said first amplifier means and the first end of said notch filter, and having a second variable attenuating means for attenuating the output of said second amplifier;
- an output terminal coupled to an output of said second amplifier;
- and
- control means for controlling said first and second attenuating means.
An electronic circuit, comprising:
- an input terminal for receiving an input signal;
- a notch filter, including a first attenuating means for attenuating said input signal, having a first end coupled to said input terminal and a second end connected to ground, said notch filter having a predetermined center frequency, and imparting a time delay to said signal;
- an amplifier for amplifying the attenuated and time-delayed input signal, said amplifier having an input coupled to said input terminal and the first end of said notch filter, and having a second attenuation means for attenuating the output of said amplifier;
- an output terminal coupled to an output of said amplifier;
- and
- control means for controlling said first and second attenuation means.
A method of processing an electronic signal, comprising:
- amplifying an input signal around a first center frequency resulting in a first amplified signal;
- filtering said first amplified signal through a notch filter having a variable attenuating means such that an attenuation and a time delay are selectably imparted to a portion of said first amplified signal;
- amplifying the attenuated and time-delayed first amplified signal through a variable gain amplifier;
- and
- controlling the attenuation and time delay in said filtering step and said gain of said variable gain amplifier in said amplifying step.
A method of processing an electronic signal, comprising:
- processing an intermediate frequency signal for a cable television television channel through a bandpass filter having a first center frequency;
- filtering said processed signal through a notch filter having a second center frequency higher than the first center frequency of said bandpass filter thereby imparting a time delay to a portion of said processed signal;
- and
- amplifying the processed and filtered signal.
Dependencies are inferred from the claim text.