Abstract. Within current implementations of mobile terminals, more and more analog components are replaced by appropriate digital processing. On the one hand, the analog front-ends become less complex. On the other hand, more digital signal processing is required to compensate for the spurious effects of the front-end. In this article, the frequency-selective imbalance of the in-phase and quadrature-phase signals is addressed. A closed representation of arbitrary signals being processed by an arbitrary imbalanced analog front-end is provided. The analysis is valid for both, direct conversion and intermediate frequency (IF) reception. With the consideration of practical variations of amplitude and phase impairments, the influence of only the frequency-dependent portions of the impairments is investigated. It is shown, that the compensation of the quasi-linear impairments is sufficient and complex deconvolutive IQ-regeneration procedures are not stringently required to obtain sufficient signal qualities.