Non-Integer-Order Low-Pass Filter with Electronically Controllable Parameters

In this paper, a new non-integer-order (fractional-order) low-pass filter with independent electronic control of the order, quality factor and pole frequency is presented. The filter operates in the current mode and uses Operational Transconductance Amplifiers (OTAs) and Adjustable Current Amplifiers (ACAs) as active elements. The values of non-integer order, quality factor and pole frequency of the filter are controlled by the internal and electronically controllable parameters of the used active elements (transconductance, current gain in our case). The proposed filter allows tunability of the pole frequency in range from 43.0 to 364.0 kHz. The filter order is controlled from 1.17 to 1.75 and finally it provides possibility to control quality factor from 0.64 to 1.9. Features of the proposed circuit are verified by PSpice simulations using transistor-level simulation models of the active elements.