Zenith Electronics Corporation

Thomas P Horwitz

Richard W Citta

Ronald B Lee

Gopalan Krishnamurthy

Raymond C Hauge

Paul A Snopko

A system supplies a compressed digital signal to a digital television receiver and includes a source of compressed baseband signal. An encoder encodes the baseband signal in a digital format, and the baseband signal has a frequency. The frequency of the encoded baseband signal is shifted by a first frequency shifter. A first interpolator interpolates an output of the first frequency shifter, a second interpolator that interpolates an output of the first interpolator, and a third interpolator that interpolates an output of the second interpolator. A second frequency shifter shifts a frequency of an output of the third interpolator to produce a signal at a selected channel.

Low cost VSB encoder and RF modulator for supplying a substantially 6 MHZ VSB signal to digital television receiver

An encoder-modulator for coupling a digital baseband television signal to a VSB digital television receiver that includes filters, equalization circuitry, and forward error correction circuitry for correcting signal impairments that are below a given threshold. The encoder-modulator processes the baseband signal for low power transmission on an RF channel with less-than-nominal bandpass characteristics. A coaxial cable or other low noise communication link directly connects the RF signal to the RF input of the television receiver. Any errors or signal impairments in the transmitted signal that are below the predetermined threshold are corrected by the filters and equalization circuitry built into the VSB digital television receiver.

Low cost VBS encoder and RF modulator for supplying VSB baseband signal to RF input of digital television receiver

A VSB modulator receives a stream of data at a 10.76 MHz constant symbol rate and converts it to a 6 MHz bandwidth signal centered at 44.0 MHz. The incoming data is interpolated by three to generate three data images and a digital filter selects the image embracing the range of 5.38 to 10.76 MHz. A sine X/X correction is added to compensate for the loss experienced in the D/A converter. The signal for the D/A converter is filtered and mixed with a 35.93 MHz oscillator output to produce data about the 44.0 MHz IF frequency. A SAW filter rejects all but the desired data.

VSB modulator

A circuit for error correcting a received complex data signal comprises a synchronous detector for recovering an in-phase data component from the received signal and a Hilbert transform filter for estimating the related quadrature component from the recovered in-phase data component, the recovered in-phase data component including a periodically recurring reference signal. A decision feedback loop is periodically operable in response to the reference signal for initially error correcting a selected characteristic of the received signal at a first relatively rapid rate and for subsequently error correcting the selected characteristic at a rate which is less than the first rate and which is dependent upon the estimated S/N ratio of the received signal. In one embodiment, phase errors are corrected at a rate which is also directly related to the value of the estimated quadrature component. In another embodiment, amplitude errors, e.g. gain and offset, are corrected at a rate which is inversely related to the value of the estimated quadrature component.

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Elgin, IL, United States of America

Thomas P Horwitz