Fractional-order Butterworth filters of order 1 + α (0 < α < 1) can be implemented by a unified structure, using the method presented in this paper. The main offered benefit is that the cutoff frequencies of the filters are fully controllable using a very simple method and, also, various types of filters (e.g., low-pass, high-pass, band-pass, and band-stop) could be realized. Thanks to the employment of a Field Programmable Analog Array device, the implementation of the introduced method is fully reconfigurable, in the sense that various types of filter functions as well as their order are both programmable.

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A generalized structure for implementing fractional-order controllers is introduced in this paper. This is achieved thanks to the consideration of the controller transfer function as a ratio of integer and non-integer impedances. The non-integer order impedance is implemented using RC networks, such as the Foster and Cauer networks. The main offered benefit, with regards to the corresponding convectional implementations, is the reduced active and, also, passive component count. To demonstrate the versatility of the proposed concept, a controller suitable for implementing a cardiac pacemaker control system is designed. The evaluation of the performance of the system is performed through circuit simulation results, using a second-generation voltage conveyor as the active element.

Higher-order fractional filters with fully controllable frequency characteristics are realized in this work, after fitting the filter's magnitude response data using a minimum-phase state-space model. Subsequently, rational integer-order transfer functions are derived and implemented using as active elements: a) Operational Transconductance Amplifiers (OTAs) and b) a Field Programmable Analog Array (FPAA) device. The realized filters enjoy electronic adjustability of their type, order, and characteristic frequencies while being easily validated on the digitally programmable FPAA platform.