Multichannel Quadrature Modulation

A method of modulating both quadrature components of each of a plurality of RF signals with waveforms comprising time varying vectors uniquely associated with each of the RF signals, the RF signals each occupying a bandwidth of a television channel and together comprising a multichannel signal spanning a frequency range that is substantially centered about a center frequency F, said method comprising:

• generating a CW signal having a frequency equal to the center frequency F;
• producing digital representations of a first composite baseband signal and a second composite baseband signal, wherein:
• the first and second composite baseband signals each comprise at least one sinusoid that is modulated in quadrature with waveforms that are each a linear combination of the waveforms comprising the time varying vector that is uniquely associated with at least one of the RF signals having a frequency higher than F and the waveforms comprising the time varying vector that is uniquely associated with at least one of the RF signals having a frequency lower than F;
• and
• wherein the time varying vectors are obtained in accordance with an impulse response causing each of the RF signals uniquely associated therewith to have spectral density extending over a frequency range of a television channel;
• and
• wherein the spectral density extending to a channel adjacent to the frequency range spanned by the multichannel signal is attenuated by at least 50 dB at a frequency designated for audio subcarrier;
• and
• wherein each of the first and the second composite baseband signals has a baseband frequency span that is substantially half of the frequency range spanned by the multichannel signal;
• converting the digital representations of the first and second composite baseband signals to a first analog and a second analog composite baseband signal respectively;
• modulating in quadrature the CW signal with the first analog and the second analog composite baseband signals to generate the multichannel signal.