Vestigial sideband generator particularly for digital television

A vestigial sideband modulator responsive to a first signal comprising information and having a frequency ωm in a predetermined bandwidth extending from ω1 to ω2, the modulator comprising:

• a source of orthogonally phased sinusoidal components having a folding frequency ω4, where ω4 is folding frequency equal to or less than (ω1″ω2)/2;
• a first signal multiplying arrangement adapted to be responsive to the first signal and the orthogonally phased sinusoidal components, the first signal multiplying arrangement generating orthogonally phased second and third signals containing the information of the first signal, each of the second and third signals having a frequency equal to (ωm−ω4);
• a lowpass filter arrangement adapted to be responsive to the second and third signals for deriving orthogonal fourth and fifth signals that contain the information of the first signal and have the same frequency, the fourth and fifth signals having a spectrum extending between ω1 and ω3, where ω3 is between ω1 and ω4, the fourth and fifth signals being such that the frequency components of the first signal extending between ω4 and ω2 are folded on the frequency components of the first signal extending between ω1 and ω4;
• a second signal multiplying arrangement adapted to be responsive to the fourth and fifth signals and quadrature phases of a carrier to generate a plurality of product signals;
• and
• a signal combiner adapted to linearly combine the plurality of product signals to derive a vestigial sideband signal containing the information in the first signal.

A digital television transmitter responsive to a digital television signal comprising a digital vestigial sideband modulator including,

• a digital sinusoidal source for deriving at least two digital signals representing sinusoidal waves,
• a digital multiplier arrangement having at least two multipliers, each multiplier for multiplying a digital signal including information in the digital television signal by an associated digital sequence derived by the digital sinusoidal source and for deriving plural digital product signals,
• a digital lowpass filter arrangement for passing low frequency components of the plural digital product signals and blocking high frequency components of the plural digital product signals,
• circuitry adapted to be responsive to a carrier and the signals passed by the lowpass filter arrangement for deriving an analog vestigial sideband signal including the information in the digital television signal, the analog vestigial sideband signal modulating the carrier, and
• further including another digital sinusoidal source for deriving other digital signals presenting sinusoidal waves having an offset frequency, a first digital signal combiner for combining the another digital signals and the digital components passed by the low pass filter arrangement, whereby the frequency of a digital I.F. is changed by a frequency determined by the offset frequency.

A digital television transmitter responsive to a digital television signal comprising a digital vestigial sideband modulator including;

• a digital sinusoidal source for deriving at least two digital signals representing sinusoidal waves;
• a digital multiplier arrangement having at least two multipliers, each multiplier for multiplying a digital signal including information in the digital television signal by an associated digital sequence derived by the digital sinusoidal source and for deriving plural digital product signals;
• a digital lowpass filter arrangement for passing low frequency components of the plural digital product signals and blocking high frequency components of the plural digital product signals;
• circuitry adapted to be responsive to a carrier and the signals passed by the lowpass filter arrangement for deriving an analog vestigial sideband signal including the information in the digital television signal, the analog vestigial sideband signal modulating the carrier;
• and
• further including an up frequency shifter arrangement for increasing by a predetermined factor a sampling rate of the digital signals applied to a first digital signal combiner.