The Quadrature IF Mixer is an image rejection mixer without the IF hybrid. Thus each IF output is 90° apart, or the I output is proportional to the SIN(WLO+WRF) , while the Q output is proportional to COS(WLO+WRF).
If one used these signals to power the horizontal and vertical inputs of an oscilloscope, a circle would be displayed for an AC IF frequency and a fixed radial vector for a DC IF or I/Q phase detector. Generally, the QIFM configuration is used for wideband digital or analog processing of video IF signals. | 
