摘要:
A television signal receiver for processing an HDTV signal transmitted in a vestigial sideband (VSB) format with a one dimensional data constellation includes a first carrier recovery network (18), an equalizer (20), and a second carrier recovery network (22, 30, 62). A multiple stage quantizer network (50, 66) exhibiting progressively finer resolution is associated with the operation of the equalizer for providing blind equalization without need of a "training" signal. The second carrier recovery network includes a phase detector (30) wherein a one symbol delayed (312) input signal and a quantized (310) input signal are multiplied (316), and an unquantized input signal and a quantized (310) one symbol delayed (314) input signal are multiplied (318). Signals produced by the multiplication are subtractively combined (320) to produce an output signal representing a carrier phase error.
摘要:
A television signal receiver for processing an HDTV signal transmitted in a vestigial sideband (VSB) format with a one-dimensional data constellation includes a first carrier recovery network (18), an equalizer (20), and a second carrier recovery network (22, 30, 62). A multiple stage quantizer network (50, 66) exhibiting progressively finer resolution is associated with the operation of the equalizer for providing blind equalization without need of a "training" signal. The second carrier recovery network includes a phase detector (30) wherein a one-symbol delayed (312) input signal and a quantized (310) input signal are multiplied (316), and an unquantized input signal and a quantized (310) one-symbol delayed (314) input signal are multiplied (316), and an unquantized input signal and a quantized (310) one-symbol delayed (314) input signal are multiplied (318). Signals produced by the multiplication are subtractively combined (320) to produce an output signal representing carrier phase error.
摘要:
An automatic gain control (AGC) system that monitors the distortion of the outer constellation points of a complex modulation format such as quadrature amplitude modulation (QAM) and adjusts both the RF and IF AGC gain to minimize such distortion. In particular, the receiver contains at least two stages of AGC gain. Typically, the RF AGC amplifier is contained in the tuner that is followed by an IF AGC amplifier. The IF amplifier is coupled to a mixer and an associated low pass filter which, in combination and when driven by a particular frequency, produces a baseband (or near baseband) signal, The baseband signal is digitized and processed by a gain control circuit. The gain control circuit produces IF and RF AGC signals that control the gain of the respective AGC stages.
摘要:
A QAM/VSB digital receiver is disclosed which includes a source of a QAM/VSB signal. An analog-to-digital converter is coupled to the QAM/VSB signal source, and is further responsive to a sample clock signal. A filter/complement is coupled to the analog-to-digital converter and has a first output terminal which produces a low-pass filtered QAM/VSB signal, and a second output terminal which produces a high-pass filtered QAM/VSB signal complementary to the low-pass filtered QAM/VSB signal. A sample clock generating circuit is coupled to the second output terminal of the filter/complement and produces the sample clock signal in response to the high-pass filtered QAM/VSB signal.
摘要:
A television signal receiver for processing an HDTV signal transmitted in a vestigial sideband (VSB) format includes input complex filters shared by a timing recovery network (30) and a carrier recovery network (50). The filter network includes a pair of upper and lower band edge filters (20, 22) mirror imaged around the upper and lower band edges of the VSB signal for producing suppressed subcarrier AM output signals. The timing recovery network includes a phase detector (28, 38, 62) and responds to an AM signal derived from the two filters (via 26) for synchronizing a system clock (CLK). The carrier recovery network (50) also includes a phase detector (54, 60, 62, 64), and responds to outputs from one or both of the filters for producing an output error signal (.DELTA.) representing a phase/frequency offset of the VSB signal. The error signal is used to reduce or eliminate the offset to produce a recovered baseband or near baseband signal. A subsequent equalizer eliminates any residual phase offsets in the recovered signal.
摘要:
A method and apparatus for performing bandedge equalization. Specifically, the apparatus contains a pre-equalizer for adjusting the amplitudes of the bandedges of a broadband signal in response to a control signal. A bandedge filter is connected to the pre-equalizer and extracts a bandedge signal from the broadband signal. Lastly, a bandedge signal processor that is connected to the bandedge filter generates the control signal in response to said bandedge signal. In this manner, when the bandedges of the broadband signal are asymmetric, the apparatus adjusts the signal strength of each bandedge with respect to one another to equalize (balance) the bandedges. The balanced signal can then be used by a bandedge timing recovery circuit. As such, the accuracy of a bandedge timing recovery circuit is not impacted by the asymmetric bandedges of the input signal.
摘要:
A television signal receiver for processing an HDTV signal transmitted in a vestigial sideband (VSB) format includes input complex filters shared by a timing recovery network (30) and a carrier recovery network (50). The filter network includes a pair of upper and lower band edge filters (20, 22) mirror imaged around the upper and lower band edges of the VSB signal for producing suppressed subcarrier AM output signals. The timing recovery network includes a phase detector (28, 38, 62) and responds to an AM signal derived from the two filters (via 26) for synchronizing a system clock (CLK). The carrier recovery network (50) also includes a phase detector (54, 60, 62, 64), and responds to outputs from one or both of the filters for producing an output error signal (.DELTA.) representing a phase/frequency offset of the VSB signal. The error signal is used to reduce or eliminate the offset to produce a recovered baseband or near baseband signal. A subsequent equalizer eliminates any residual phase offsets in the recovered signal.
摘要:
A data detector is disclosed which includes a source of a data signal representing a sequence of symbols. A maximum likelihood sequence detector, is coupled to the data signal source, and produces a most likely survivor sequence, which includes a plurality of symbols. A decision feedback equalizer and a phase detector, controlling the timing of the sampling of the data signal, are made responsive to the most likely survivor sequence.