Low distortion passthrough circuit arrangement for cable television set top converter terminals
AssigneeGeneral Instrument Corporation
InventorsLouis Caporizzo, Dipakkumar R. Patel
Life of this patent
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Abstract
In a cable television converter terminal, NICAM signal passthrough is achieved using an alignment-free passthrough circuit including a NICAM SAW filter. The alignment-free passthrough circuit directly taps the output of the converter terminal's tuner to obtain the NICAM signal. As a result, the NICAM signal is not distorted by the components involved in obtaining the other signal components of the cable television signal. Consequently, sound quality is improved and rendered less vulnerable to degradation due to component aging, temperature fluctuations, and human error. The passthrough circuit can be implemented as a removable circuit module.
Claims9
For use in a cable television converter terminal, a passthrough circuit for passing a tuned signal from a tuner to a radio frequency modulator for output to external equipment, the passthrough circuit arrangement comprising:
- a first signal path, arranged to receive the tuned signal directly from the tuner and to provide a NICAM signal component of the tuned signal to the radio frequency modulator;
- and
- a second signal path, arranged to receive the tuned signal from the tuner and to provide at least one other signal component of the tuned signal to the radio frequency modulator;
- wherein the second signal path comprises:
- a channel surface acoustic wave filter, arranged to receive the tuned signal from the tuner and to filter the tuned signal to generate a filtered signal;
- an intermediate frequency strip, configured and arranged to amplify the filtered signal;
- a dual surface acoustic wave filter, configured and arranged to separate the amplified filtered signal into audio and video signal components;
- an audio and video amplifier, operatively coupled to the dual surface acoustic wave filter and configured and arranged to amplify the audio and video signal components;
- and
- an audio/video demodulator, configured and arranged to downconvert the amplified audio and video signal components to their respective baseband frequencies and to provide the downconverted audio and video signal components to the radio frequency modulator.
Dependencies are inferred from the claim text.