Design Procedure of RF Quadrature Modulators and Demodulators with Controllable Unbalance LO Path

The paper presents a design procedure that generalises the existing experience in designing local oscillator paths for quadrature modulators and demodulators. The main stages of the procedure are the choice of the phase splitter architecture; design and adjustment of a polyphase filter or frequency divider; phase control circuit design; amplifiers design, tuning the frequency response, output amplitude and level of the local oscillator signal; DACs design for phase and amplitude unbalance control, layout design. Modern quadrature modulators and demodulators are used in wireless communication systems, satellites, cellular, locators, Wi-Fi systems.