Television – Receiver circuitry – Demodulator
Reexamination Certificate
2007-04-03
2007-04-03
Natnael, Paulos M. (Department: 2622)
Television
Receiver circuitry
Demodulator
Reexamination Certificate
active
10262514
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.
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Kamata Takatsugu
Utsunomiya Kimitake
Natnael Paulos M.
RfStream Corporation
Stattler Johansen & Adeli LLP
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