Multichannel Quadrature Modulation

Abstract

A method is disclosed for 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. A CW signal is generated having a frequency equal to the center frequency F. Digital representations are produced of a first composite baseband signal and a second composite baseband signal. The digital representations of the first and second composite baseband signals are converted to a first analog and a second analog composite baseband signal respectively. The CW signal with the first analog and the second analog composite baseband signals are modulated in quadrature to generate the multichannel signal.

1 . (canceled) 
   
   
       2 . 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.   
   
   
       3 . The method of  claim 2  further comprising obtaining at least one of the time varying vectors in accordance with an impulse response causing each of the RF signals uniquely associated therewith to have spectral density extending over a frequency range substantially equal to an adjacent channel separation frequency of the multichannel signal. 
   
   
       4 . The method of  claim 2  further comprising obtaining the time varying vectors uniquely associated with each of the plurality of RF signals in accordance with a common impulse response. 
   
   
       5 . The method of  claim 3  wherein the adjacent channel separation frequency of the multichannel signal is 6 MHz. 
   
   
       6 . The method of  claim 4  wherein the adjacent channel separation frequency of the multichannel signal is 6 MHz. 
   
   
       7 . The method of  claim 2  further comprising obtaining the time varying vectors in accordance with varying levels selected from a fixed set of values. 
   
   
       8 . The method of  claim 2  further comprising obtaining the time varying vectors in accordance with varying levels of a periodic signal. 
   
   
       9 . The method of  claim 2  further comprising obtaining at least one of the time varying vectors in accordance with an impulse response causing the RF signals uniquely associated therewith to be VSB modulated 
   
   
       10 . The method of  claim 2  further comprising sharing the CW signal to generate a plurality of the multichannel signals. 
   
   
       11 . The method of  claim 10  further comprising feeding each of the generated plurality of the multichannel signals to a separate RF output port. 
   
   
       12 . The method of  claim 10  further comprising combining the generated plurality of multichannel signals to form a broadband signal. 
   
   
       13 . The method of  claim 12  further comprising amplifying the broadband signal using a common amplifier. 
   
   
       14 . The method of  claim 2  wherein said converting the digital representations further comprises converting samples at a sample rate that is equal to an integral multiple of the predetermined frequency increment.