Design and realization of fractional order butterworth low pass filters

In this paper, simulated annealing and suitable scaling optimization techniques are used to design the fractional order low pass filters with Butterworth approximation. The frequency responses of the obtained optimal designs are closer to the ideal one as compared to the other existing designs. The designed filters are further realized using Tow-Thomas biquad topology by replacing traditional capacitors with the fractional capacitors, which are approximated by continued fraction expansion and then realized with the RC ladder network. The effectiveness of the proposed circuit realizations is also shown by PSPICE simulated results.