Bandpass tracker for DTV receiver, with VSB I-F signal filtered for more symmetrical AFPC Loop response

A digital radio receiver for a baseband symbol code designed to have a spectrum reaching essentially to zero-frequency and transmitted by a digital radio signal with vestigial-sideband amplitude modulation of a suppressed carrier wave so as to have an asymmetrical channel response around the frequency of said suppressed carrier wave, even in a narrow-frequency band including a pilot carrier signal at the frequency of said suppressed carrier wave, said receiver comprising:

• a tuner including
• mixer circuitry for supplying a final intermediate-frequency signal responsive to local oscillations and received vestigial-sideband amplitude-modulation sidebands of a carrier wave with accompanying pilot carrier signal, and further including
• a local oscillator for supplying said local oscillations with frequency and phase controlled in response to an automatic-frequency-and-phase-control signal;
• in-phase demodulator circuitry for recovering said baseband symbol code in response to said final intermediate-frequency signal;
• first filter circuitry for shaping the frequency spectrum of said final intermediate-frequency signal in its frequency-selective response thereto so as to be of substantially reduced slope in said narrow-frequency band including a pilot carrier signal;
• quadrature-phase demodulator circuitry for generating said automatic-frequency-and-phase-control signal in response to the frequency-selective response of said first filter circuitry to said final intermediate-frequency signal;
• and
• second filter circuitry for shaping the frequency spectrum of said final intermediate-frequency signal in its frequency-selective response thereto to achieve a cumulative roll-off in said receiver of 3 db at the frequency of said suppressed carrier wave and for applying said final intermediate-frequency signal with its frequency spectrum so shaped to said in-phase demodulator circuitry as input signal for demodulation.

A receiver for a baseband symbol code designed to have a spectrum reaching essentially to zero-frequency and transmitted by vestigial-sideband amplitude modulation of a suppressed carrier wave so as to have an asymmetrical channel response even in a narrow-frequency band including a pilot carrier signal at the frequency of said suppressed carrier wave, said receiver comprising:

• a tuner including
• mixer circuitry for supplying a final intermediate-frequency signal responsive to local oscillations and received vestigial-sideband amplitude-modulation sidebands of a carrier wave with accompanying pilot carrier signal, and further including
• a local oscillator for supplying said local oscillations with frequency and phase controlled in response to an automatic-frequency-and-phase-control signal;
• analog-to-digital conversion circuitry for digitizing said final intermediate-frequency signal to supply a digitized final intermediate-frequency signal;
• in-phase digital synchrodyning circuitry for recovering said baseband symbol code in response to said digitized final intermediate-frequency signal;
• first digital filtering circuitry for supplying a first digital filtering response to said digitized final intermediate-frequency signal in which the system response of said digitized final intermediate-frequency signal is shaped so as to be of substantially reduced slope in said narrow-frequency band including a pilot carrier signal;
• quadrature-phase digital synchrodyning circuitry for generating a digital loop-error signal by synchrodyning said first digital filtering response to baseband;
• circuitry for generating said automatic-frequency-and-phase-control signal for said local oscillator responsive to said digital loop-error signal;
• and
• second digital filter circuitry for shaping the frequency spectrum of said final intermediate-frequency signal in its system response thereto to achieve a cumulative roll-off in said receiver of 3 db at the frequency of said suppressed carrier wave, said second digital filter circuitry connected so that said digital final intermediate-frequency signal with the frequency spectrum in its system response so shaped is applied to said in-phase digital synchrodyning circuitry as input signal for demodulation.