Design of an electronically controlled non-integer order generalized filter
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Date
2024-03-19
Authors
Καλούδη, Ελένη
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Abstract
This Thesis focuses on the design and implementation of non-integer order filters derived
from a first-order mother transfer function. Specifically, Fractional-order, Power-Law, and
Double-order Low-pass, High-pass, and Band-pass filters, as well as their Inverse counter-
parts, are investigated. To effectively realize these filters, the derived transfer functions
require approximation. While conventional approximation methods suffice for simulating
the behavior of simple fractional operators such as the Laplacian operator sα, they prove
inadequate for more complex filters, that involve more than one non-integer order coeffi-
cients. Thus, a curve fitting method based on MATLAB’s fitfrd command is employed.
The resulting integer-order transfer functions can be implemented using conventional filter
design topologies. This study utilizes the IFLF (Inverse-Follow-the-Leader-Feedback)
multiple-feedback filter topology with OTAs (Operational Transconductance Amplifiers)
as the active element, leveraging the adjustability of the transconductance through fine-
tuning the DC bias currents. This structure offers flexibility by enabling implementation
of multiple filter transfer functions from the same active core, through bias current
adjustments. Post-layout simulation results, obtained using Cadence IC design software
and the Design Kit provided by the Austria Mikro Systeme (AMS) 0.35 μm CMOS
technology, validate the reliability of this approach. In summary, this proposed concept
offers advantages such as resistorless implementations, satisfactory accuracy, utilization
of only grounded capacitors, and a universally adaptable electronic structure.
Description
Keywords
Generalized filters, Operational transconductance amplifiers, Fractional-order filters, Power-law filters, Double-order filters, Fractional calculus, CMOS integrated circuits