Experimental verification of filters using fractional-order capacitor and inductor emulators

Fractional-order filter design examples, realized through the substitution of fractional-order capacitors and inductors by appropriate active emulators, are presented in this paper. The implementation of emulators has been achieved using Current Feedback Operational Amplifiers (CFOAs) as active element. Also, the realization of the required fractional-order differentiation/integration, for emulating the fractional-order elements, is performed through the employment of an integer-order multi-feedback topology. An important benefit, from the design flexibility point of view, is that the same topology could be used for emulating both fractional-order capacitor and inductor, and this is achieved through an appropriate selection of the time-constants and gain factors. The behavior of the realized filters is evaluated using the commercially available AD844 discrete CFOA.