DC Offset
DC offset is a complex signal impairment that shifts the locus of ideal symbol coordinates off-center in the I/Q plane. A DC offset can be added to the baseband I component, the Q component, or both. The DC offset can be either positive or negative, with the sign indicating the direction of the shift. DC offset is expressed as a percentage of full scale, where "full scale" (fs) is the amplitude of the baseband quadrature modulation (QM) waveform.