Quadrature modulator with integrated distributed RC filters

A quadrature modulator for the generation of complex modulated signals, comprising:

• a digital sample generator producing a sequence of numerical value pairs respectively representing a real and imaginary modulating waveform;
• a delta-sigma convertor circuit converting said sequence of pairs of numerical values to a high bit rate stream I representing said real waveform and a high bit rate stream Q representing said imaginary waveform, and additionally a bitstream I being the complement of I and a bitstream Q being the complement of Q;
• a pair of balanced, low-pass filters each having two inputs accepting said bitstreams I, I and Q, Q respectively and each having two output lines providing balanced, filtered I and Q signals;
• a first balanced modulator having a first, balanced input including two lines connected to said balanced, filtered I signals, and a second input connected to a cosine carrier frequency signal generator;
• a second balanced modulator having a first, balanced input including two lines connected to said balanced, filtered Q signals, and a second input connected to a sine carrier frequency generator;
• and
• an adder for adding said first and second balanced modulator outputs together.