DTV receiver with baseband equalization filters for QAM signal and for VSB signal which employ common elements

Claim 2

A digital television signal receiver comprising: demodulator circuitry for demodulating a quadrature-amplitude-modulation (QAM) digital television signal to generate an in-phase sample stream and a quadrature-phase sample stream; baseband equalization and ghost-cancellation filtering having adaptive filtering parameters; a time-division multiplexer for interleaving said in-phase sample stream and said quadrature-phase sample stream on an alternate-sample basis to generate an interleaved sample stream, said interleaved sample stream being applied as input signal to said baseband equalization and ghost-cancellation filtering when said digital television receiver is conditioned for receiving a QAM digital television signal, thereby causing a QAM-reception response from said baseband equalization and ghost-cancellation filtering; a time-division-multiplex de-multiplexer for separating said in-phase sample stream and said quadrature-phase sample stream from said QAM-reception response; a QAM symbol decoder connected for responding to said in-phase sample stream and said quadrature-phase sample stream separated from said QAM-reception response; and circuitry for generating the adaptive filtering parameters for said baseband equalization and ghost-cancellation filtering, so said baseband equalization and ghost-cancellation filtering operates as a dual-phase filter for said interleaved sample stream supplied thereto as its input signal when said digital television receiver is conditioned for receiving a QAM digital television signal.

Claim 3

The digital television signal receiver of claim 1 , further comprising: first and second rate-change filters respectively connected to receive said in-phase sample stream and said quadrature-phase sample stream separated from said QAM-reception response, for reduction to a sample rate equal to symbol rate for said QAM digital television signal before application to said QAM symbol decoder.

Claim 4

The digital television signal receiver of claim 1 , further comprising: demodulator circuitry for demodulating a vestigial-sideband amplitude-modulation (VSB AM) digital television signal to generate another in-phase sample stream, which said other in-phase sample stream is applied as input signal to said baseband equalization and ghost-cancellation filtering when said digital television receiver is conditioned for receiving a VSB AM digital television signal, thereby causing a VSB-reception response from said baseband equalization and ghost-cancellation filtering; a VSB symbol decoder connected for responding to said VSB-reception response; and circuitry for generating the adaptive filtering parameters for said baseband equalization and ghost-cancellation filtering, so said baseband equalization and ghost-cancellation filtering operates as a single-phase filter for said other in-phase sample stream supplied thereto as its input signal when said digital television receiver is conditioned for receiving a VSB AM digital television signal.

Claim 5

The digital television signal receiver of claim 3 , further comprising: a rate-change filter connected to receive said VSB-reception response from said baseband equalization and ghost-cancellation filtering, for reduction to a sample rate equal to symbol rate for said VSB AM digital television signal before application to said VSB symbol decoder.

Claim 6

The digital television signal receiver of claim 3 , further comprising: first and second rate-change filters respectively connected to receive said in-phase sample stream and said quadrature-phase sample stream separated from said QAM-reception response, for reduction to sample rate equal to symbol rate for said QAM digital television signal before application to said QAM symbol decoder; and a third rate-change filter connected to receive said VSB-reception response, for reduction to sample rate equal to symbol rate for said vestigial-sideband amplitude-modulation digital television signal before application to said VSB symbol decoder.

Claim 7

The digital television signal receiver of claim 5 , wherein the symbol rate for said VSB AM digital television signal is twice the symbol rate for said QAM digital television signal.

Claim 8

The digital television signal receiver of claim 5 , wherein the symbol rate for said VSB AM digital television signal is substantially 10.76* 10 6 symbols per second.

Claim 9

A digital television signal receiver comprising: demodulator circuitry for demodulating both vestigial-sideband amplitude-modulation (VSB AM) and quadrature-amplitude-modulation (QAM) digital television signals as received at different times to generate a baseband digital television signal response; baseband equalization and ghost-cancellation filtering connected for receiving said baseband digital television signal response as input signal, connected for supplying a de-ghosted response to said baseband digital television signal response received as input signal, operated as a single-phase filter when said baseband digital television signal response is demodulated from said vestigial-sideband amplitude-modulation (VSB AM) digital television signal, and operated as a dual-phase filter when said baseband digital television signal response is demodulated from said quadrature-amplitude-modulation (QAM) digital television signal; a VSB symbol decoder for decoding said de-ghosted response when said baseband digital television signal response is demodulated from said vestigial-sideband amplitude-modulation (VSB AM) digital television signal; and a QAM symbol decoder for decoding said de-ghosted response when said baseband digital television signal response is demodulated from said quadrature-amplitude-modulation (QAM) digital television signal.

Claim 10

A digital television signal receiver comprising: demodulator circuitry for demodulating both vestigial-sideband amplitude-modulation (VSB AM) and quadrature-amplitude-modulation (QAM) digital television signals as received at different times to generate a baseband digital television signal response; baseband equalization and ghost-cancellation filtering connected for receiving said baseband digital television signal response as input signal, connected for supplying a de-ghosted response to said baseband digital television signal response received as input signal, operated as a single-phase filter when said baseband digital television signal response is demodulated from said vestigial-sideband amplitude-modulation (VSB AM) digital television signal, and operated as a dual-phase filter when said baseband digital television signal response is demodulated from said quadrature-amplitude-modulation (QAM) digital television signal; a VSB symbol decoder for decoding said de-ghosted response when said baseband digital television signal response is demodulated from said vestigial-sideband amplitude-modulation (VSB AM) digital television signal; and a QAM symbol decoder for decoding said de-ghosted response when said baseband digital television signal response is demodulated from said quadrature-amplitude-modulation (QAM) digital television signal.

Claim 11

The digital television signal receiver of claim 8 , wherein said baseband equalization and ghost-cancellation filtering comprises: a first digital filter connected for receiving said baseband digital television signal response as its input signal, said first digital filter for supplying at an oversampled rate a first finite-impulse response to said input signal thereof; a second digital filter connected for supplying at said oversampled rate a second finite-impulse response to an input signal thereof, a digital subtractor for supplying at said oversampled difference output signal responsive to said first and second finite-impulse responses received as minuend and subtrahend input signals, respectively; a quantizer for supplying a quantizer output signal responsive to quantizer input signal applied thereto; a dual-phase QAM rate-reduction filter connected for responding to said oversampled difference output signal to supply a QAM rate-reduction filter response at twice the Nyquist rate for said QAM digital television signal, said QAM rate-reduction filter response applied to said quantizer as said quantizer input signal when said baseband digital television signal response is demodulated from said QAM digital television signal; a single-phase VSB rate-reduction filter connected for responding to said oversampled difference output signal to supply a VSB rate-reduction filter response at the Nyquist rate for said VSB AM digital television signal, said VSB rate-reduction filter response applied to said quantizer as said quantizer input signal when said baseband digital television signal response is demodulated from said VSB AM digital television signal; a dual-phase QAM interpolation filter connected for responding to said quantizer output signal to supply the input signal to said second digital filter at said oversampled rate when said baseband digital television signal response is demodulated from said QAM digital television signal; and a single-phase VSB interpolation filter connected for responding to said quantizer output signal to supply the input signal to said second digital filter at said oversampled rate when said baseband digital television signal response is demodulated from said VSB AM digital television signal.

Claim 12

The digital television signal receiver of claim 9 , wherein said first and second digital filters are each of a type generating its response as a weighted summation employing adjustable weights, wherein said baseband equalization and ghost-cancellation filtering further comprises an error detector responsive to the difference between said oversampled difference output signal and the input signal to said second digital filter for generating decision feedback information; and wherein said digital television signal receiver further comprises a filter-parameter computer for computing adjustments to said adjustable weights of said first and second digital filters, based on said decision feedback informnation.

Claim 13

Baseband equalization and ghost-cancellation filtering apparatus for digital television receiver; said filtering apparatus comprising: a first digital filter connected for receiving baseband digital television signal response supplied at a first sample rate as its input signal, said first digital filter of a type for supplying at an oversampled rate a first finite-impulse response to said input signal thereof, a second digital filter connected for supplying at said first sample rate a second finite-impulse response to an input signal thereof, a digital subtractor for supplying at said first sample rate a difference output signal responsive to said first and second finite-impulse responses received as minuend and subtrahend input signals, respectively; a quantizer for supplying a quantizer output signal responsive to quantizer input signal applied thereto; a dual-phase rate-reduction filter connected for responding to said difference output signal to supply a dual-phase rate-reduction filter response; a single-phase rate-reduction filter connected for responding to said difference output signal to supply a single-phase rate-reduction filter response; a first multiplexer responsive to a first condition of a control signal for selecting said dual-phase rate-reduction filter response as said quantizer input signal and responsive to a second condition of said control signal for selecting said single-phase rate-reduction filter response as said quantizer input signal; a dual-phase interpolation filter connected for responding to said quantizer output signal to supply a dual-phase rate-reduction filter response; a single-phase interpolation filter connected for responding to said quantizer output signal to supply a single-phase interpolation filter response; a second multiplexer responsive to said first condition of said control signal for selecting said dual-phase interpolation filter response as said second digital filter input signal and responsive to said second condition of said control signal for selecting said single-phase interpolation filter response as said second digital filter input signal.

Claim 14

Baseband equalization and ghost-cancellation filtering apparatus for digital television receiver; said filtering apparatus comprising: a first digital filter connected for receiving baseband digital television signal response supplied at a first sample rate as its input signal, said first digital filter of a type for supplying at an oversampled rate a first finite-impulse response to said input signal thereof, a second digital filter connected for supplying at said first sample rate a second finite-impulse response to an input signal thereof, a digital subtractor for supplying at said first sample rate a difference output signal responsive to said first and second finite-impulse responses received as minuend and subtrahend input signals, respectively; a quantizer for supplying a quantizer output signal responsive to quantizer input signal applied thereto; a dual-phase rate-reduction filter connected for responding to said difference output signal to supply a dual-phase rate-reduction filter response; a single-phase rate-reduction filter connected for responding to said difference output signal to supply a single-phase rate-reduction filter response; a first multiplexer responsive to a first condition of a control signal for selecting said dual-phase rate-reduction filter response as said quantizer input signal and responsive to a second condition of said control signal for selecting said single-phase rate-reduction filter response as said quantizer input signal; a dual-phase interpolation filter connected for responding to said quantizer output signal to supply a dual-phase rate-reduction filter response; a single-phase interpolation filter connected for responding to said quantizer output signal to supply a single-phase interpolation filter response; a second multiplexer responsive to said first condition of said control signal for selecting said dual-phase interpolation filter response as said second digital filter input signal and responsive to said second condition of said control signal for selecting said single-phase interpolation filter response as said second digital filter input signal.

Claim 15

The baseband equalization and ghost-cancellation filtering apparatus of claim 11 , wherein said first and second digital filters are each of a type generating its response as a weighted summation employing adjustable weights, said filtering apparatus further comprising an error detector connected for comparing said difference output signal and the input signal to said second digital filter to generate decision feedback information useful for computing adjustments to said adjustable weights of said first and second digital filters.