I. Introduction
Many filter design solutions [1]–[9] focus on the versatility of the filter i.e. provision of multiple transfer functions from given proposed circuit topology. So-called universal (2nd-order) filters provide all standard 2nd-order functions (high pass (HP), low pass (LP), band pass (BP), band pass (BS) and all pass (AP)). So-called multifunctional filters then provide some of these functions (more than one, but not all). The ability of the filtering structure to provide multiple transfer functions and/or possibility of the fine adjustment of the transfer function (adjustment of the pass-band region, adjustment of the stop-band region, etc.) can be fairly beneficial in the domain of the signal processing [10].