Patent ID: 7149261

Claim:
An image reject circuit apparatus comprising: a first frequency downconversion circuit employing a first local oscillator for downconverting in-phase and quadrature signal components of a digitized communication signal to a first intermediate frequency; sigma delta converters for generating an in phase digital bit stream and a quadrature phase digital bit stream; a digital in-phase and quadrature phase second local oscillator; mixing circuitry for mixing respective single serial digital bit stream in-phase signal and single serial digital bit stream quadrature phase signal through a set of logic gates to produce a digital representation of downconverted in-phase and quadrature components, the mixing circuitry comprising, for each significant bit: first and second exclusive-OR gates coupled to receive as first input an in phase digital bit stream and as second inputs a high accuracy sine function bit stream and a high accuracy cosine function bit stream; third and fourth exclusive-OR gates coupled to receive as first input a quadrature phase digital bit stream and as second inputs a high accuracy sine function bit stream; first OR gate for logically adding the outputs of the first and second XOR gates for the in-phase channel; first AND gate for logically multiplying the outputs of the first and second XOR gates for the in-phase channel; second OR gate for logically adding the outputs of the third and fourth XOR gates for the quadrature phase channel; and second AND gate for logically multiplying the outputs of the third and fourth XOR gates for the quadrature phase channel; weighting resistances in series with the outputs of the logic gates for combining the digital representation of the downconverted in-phase and quadrature components according to a value in an in-phase signal and in a quadrature phase signal; and reconstruction filters to recover in-phase and quadrature phase baseband signals from said downconverted in-phase and quadrature components substantially free of image artifacts.