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Baseband phase modulator apparatus employing digital techniques

  • US 4,761,798 A
  • Filed: 04/02/1987
  • Issued: 08/02/1988
  • Est. Priority Date: 04/02/1987
  • Status: Expired due to Term
First Claim
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1. A Zero IF modulator apparatus for modulating RF carrier signals with baseband signals and operative to perform phase or frequency modulation, comprising:

  • first and second analog-to-digital converters each having a separate input adapted to receive an analog baseband signal and each having a separate output for providing a digital signal indicative of the analog baseband signal applied to said input,a weighting function generator means having an input coupled to the output of said first analog-to-digital converter and operative to provide at an output said digital signal at the output of said first analog-to-digital converter as multiplied by a given weighting function,a digital sine/cosine amplitude converter means having an input and operative to provide at a first output a first digital quadrature baseband signal and to provide at a second output a second digital quadrature baseband signal,adding means having one input coupled to the output of said weighting function generator means and another input coupled to the output of said second analog-to-digital converter with the output of said adding means coupled to the input of said sine/cosine amplitude converter means wherein said sine/cosine converter can receive a digital baseband signal from either said first or second converters,a first digital-to-analog converter coupled to said first output of said sine/cosine converter means to provide at an output a first analog quadrature signal,a second digital-to-analog converter coupled to said second output of said sine/cosine converter means to provide at an output a second analog quadrature signal, andmodulation translation means including a carrier oscillator operating at a given frequency, said modulation translation means responsive to said first and second analog quadrature signals for translating said signals to a given carrier frequency.

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