Quadratic nyquist slope filter
First Claim
1. A television demodulator circuit comprising:
- I, Q demodulator for receiving a television signal and for mixing the television signal with an in-phase (“
I”
) local oscillator signal and a quadrature phase (“
Q”
) local oscillator signal at a tuned television channel to generate a baseband I signal and a baseband Q signal;
low pass filter, coupled to the I, Q demodulator, for filtering the baseband I signal and baseband Q signal; and
Nyquist slope filter for receiving the baseband I signal and baseband Q signal and for generating a video signal by generating a Nyquist slope response and by attenuating channels adjacent to the tuned television channel, wherein the Nyquist slope filter comprises a transfer function with at least two zero crossings, so as to provide a notch filter response for attenuation of a television channel adjacent to the tuned television channel.
2 Assignments
0 Petitions
Accused Products
Abstract
A television demodulator circuit, for use in a television receiver, generates baseband video and audio outputs from a television signal, such as an intermediate frequency television signal. The I, Q demodulator circuit mixes the television signal with an in-phase (“I”) local oscillator signal and a quadrature phase (“Q”) local oscillator signal at the tuned frequency to generate baseband I and Q signals. The baseband I and Q signals are input to low pass filters and a Nyquist slope filter. The Nyquist slope filter generates, for the baseband I and Q signals, a Nyquist slope response and attenuates channels adjacent to the tuned television channel. The Nyquist slope filter comprises a transfer function with at least two zero crossings, so as to provide a notch filter response for attenuation of a television channel adjacent to the tuned television channel. For example, the transfer function may have three zero crossings to attenuate a sound carrier frequency, a color carrier frequency, and a picture frequency for the television channel adjacent to the tuned television channel. The transfer function, expressed in the S domain, comprises an all-pass fractional transfer function with a real number in the numerator and a complex number in the denominator. A television receiver that incorporates the I, Q demodulator circuit is disclosed.
103 Citations
11 Claims
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1. A television demodulator circuit comprising:
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I, Q demodulator for receiving a television signal and for mixing the television signal with an in-phase (“
I”
) local oscillator signal and a quadrature phase (“
Q”
) local oscillator signal at a tuned television channel to generate a baseband I signal and a baseband Q signal;low pass filter, coupled to the I, Q demodulator, for filtering the baseband I signal and baseband Q signal; and Nyquist slope filter for receiving the baseband I signal and baseband Q signal and for generating a video signal by generating a Nyquist slope response and by attenuating channels adjacent to the tuned television channel, wherein the Nyquist slope filter comprises a transfer function with at least two zero crossings, so as to provide a notch filter response for attenuation of a television channel adjacent to the tuned television channel. - View Dependent Claims (2, 3, 4, 5)
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6. A television demodulator circuit comprising:
-
I, Q demodulator for receiving a television signal and for mixing the television signal with an in-phase (“
I”
) local oscillator signal and a quadrature phase (“
Q”
) local oscillator signal at a tuned television channel to generate a baseband I signal and a baseband Q signal;low pass filter, coupled to the I, Q demodulator, for filtering the baseband I signal and baseband Q signal; and Nyquist slope filter for receiving the baseband I signal and baseband Q signal and for generating a video signal by generating a Nyquist slope response and by attenuating channels adjacent to the tuned television channel, wherein said Nyquist slope filter comprises an all-pass fractional transfer function. - View Dependent Claims (7, 8)
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9. A television demodulator circuit comprising:
-
I, Q demodulator for receiving a television signal and for mixing the television signal with an in-phase (“
I”
) local oscillator signal and a quadrature phase (“
Q”
) local oscillator signal at a tuned television channel to generate a baseband I signal and a baseband Q signal;low pass filter, coupled to the I, Q demodulator, for filtering the baseband I signal and baseband Q signal; and Nyquist slope filter for receiving the baseband I signal and baseband Q signal and for generating a video signal by generating a Nyquist slope response and by attenuating channels adjacent to the tuned television channel, wherein the Nyquist slope filter comprises inverters, such that a transfer function for the Nyquist slope filter comprises terms of the numerator with the same sign. - View Dependent Claims (10, 11)
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Specification
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- Resources
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Current AssigneeRfstream Corporation
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Original AssigneeRfstream Corporation
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InventorsUtsunomiya, Kimitake, Kamata, Takatsugu
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Primary Examiner(s)Natnael; Paulos M.
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Application NumberUS10/262,514Publication NumberTime in Patent Office1,646 DaysField of Search348/726, 348/473, 348/475, 348/725, 348/728, 348/729, 375/296US Class Current348/726CPC Class CodesH03D 1/2245 using two quadrature channe...
