Method and apparatus for a fully digital quadrature modulator

A method of digital In-phase/Quadrature complex modulation, said method comprising the steps of:

• providing an I switch array adapted to generate a first signal proportional to the number of switches active within said I switch array;
• providing a Q switch array adapted to generate a second signal proportional to the number of switches active within said Q switch array;
• applying a first gated combination of an I local oscillator clock signal and an I digital control word to said I switch array whereby the number of switches active in said I switch array is determined by said I control word;
• applying a second gated combination of a Q local oscillator clock signal and a Q digital control word to said Q switch array whereby the number of switches active in said Q switch array is determined by said Q control word;
• and
• summing said first signal and said second signal to yield a complex modulated output signal therefrom.

A digital quadrature modulator, comprising:

• a local oscillator operative to generate quadrature phases;
• a switch array comprising a plurality of switches adapted to generate a complex modulated output signal substantially proportional to the number of switches active at any one time in said array;
• a switch matrix adapted to couple said quadrature phases output of said local oscillator to said switch array;
• and
• control means coupled to said switch array, said control means operative to dynamically allocate a first portion of said switches to In-phase (I) output and a second portion to Quadrature (Q) output based on values of In-phase (I) and Quadrature (Q) input signals.

A digital quadrature modulator, comprising:

• oscillator means for generating a local oscillator In phase (I) (LOI) signal, an inverted LOI signal, a Quadrature (Q) (LOQ) signal, and an inverted LOQ signal;
• an In phase (I) switch array comprising a plurality of first switches adapted to generate an In phase (I) output signal substantially proportional to a number of first switches active at any one time, wherein the number of first switches active in synchronization with the LOI or LOI signal is determined by a magnitude of an In phase (I) digital input signal;
• a Quadrature (Q) switch array comprising a plurality of second switches adapted to generate a Q output signal substantially proportional to the number of second switches active at any one time, wherein the number of second switches active in synchronization with the LOQ or LOQ signal is determined by a magnitude of a Quadrature (Q) digital input signal;
• first means adapted to couple either said LOI signal or said LOI signal to said In phase (I) switch array in accordance with a sign of said In phase (I) input signal;
• second means adapted to couple either said LOQ signal or said LOQ signal to said Quadrature (Q) switch array in accordance with a sign of said Quadrature (Q) input signal;
• and
• means for summing said In phase (I) output signal and said Quadrature (Q) output signal to generate a quadrature modulated output therefrom.

A digital quadrature modulator, comprising:

• oscillator means for generating a first local oscillator signal LOI, a second local oscillator signal LO′I, a third local oscillator signal LOQ, and fourth local oscillator signal LO′Q;
• a switch array comprising a plurality of switches adapted to be shared between In phase (I) and Quadrature (Q) digitally control branches, said switch array operative to generate a quadrature modulated output signal substantially proportional to a number of switches instantaneously active in accordance with combined In phase (I) and Quadrature (Q) input digital signals and said local oscillator signals;
• first means for generating an In phase (I) contribution in accordance with an In phase (I) input signal and an In phase (I) local oscillator signal;
• second means for generating a Quadrature (Q) contribution in accordance with an In phase (I) input signal and an In phase (I) local oscillator signal;
• and
• third means for time multiplexing said In phase (I) contribution and said Quadrature (Q) contribution to yield said combined In phase (I) and Quadrature (Q) signal to produce said quadrature modulated output.