Digitally programmed fractional-order Chebyshev filters realizations using current-mirrors

Fractional-order filter realizations with Chebyshev characteristics, approximated by appropriate integer-order topologies, are realized in this work. The employed active blocks were current-mirrors and the derived filters offer the following attractive characteristics: capability of operating in a low-voltage environment, circuit simplicity and resistor-less realization. In addition, a digitally controlled current division network is employed to perform electronic adjustment of the cut-off frequency as well as the order of the filters. The performance of the proposed fractional-order filters is evaluated through the Analog Design Environment of the Cadence software and the Design Kit provided by the AMS 0.35μm CMOS process. The obtained simulation results for orders 1.2, 1.5, and 1.8 confirm that both pass-band and stop-band characteristics of the filters are preserved, while the transition from pass-band to stop-band is performed in fractional-order steps.