Inverse Analog Filters: History, Progress and Unresolved Issues

Abstract

This paper traces the history of the evolution of inverse analog filters (IAF) and presents a review of the progress made in this area to date. The paper, thus, presents the current state-of-the art of IAFs by providing an appraisal of a variety of realizations of IAFs using commercially available active building blocks (ABB), such as operational amplifiers (Op-amp), operational transconductance amplifiers (OTA), current conveyors (CC) and current feedback operational amplifiers (CFOA) as well as those realized with newer active building blocks of more recent origin, such as operational transresistance amplifiers (OTRA), current differencing buffered amplifiers (CDBA) and variants of current conveyors which, although not available as off-the-shelf ICs yet, can be implemented as complementary metal–oxide–semiconductors (CMOS) or be realized in discrete form using other commercially available integrated circuits (IC). In the end, some issues related to IAFs have been highlighted which need further investigation.

First‐order inverse filters: Implementations using a single voltage conveyor and potential applications

“…As a result, looking for suitable applications for the employment of this type of filters is a crucial process. This was also clearly mentioned in Senani et al, 5 where the main derivation was that second-order inverse band pass filters could be employed for implementing proportional-integral-derivative (PID) controllers. This is originated from the fact that control applications do not generally require a relatively wide frequency band of operation.…”

“…Inverse filters have a frequency response which is reciprocal of the frequency response of their conventional counterparts, that is, low pass, high pass, and band pass. Second‐order inverse filters have been widely introduced in the literature, 1–4 but a limited number of first‐order structures have been published 5 . More specifically, the inverse filter structures in Shah et al 6,7 are current mode inverse all pass filters using as active elements four terminal floating nullor (FTFN) and current differencing transconductance amplifiers (CDTAs), respectively.…”

Development and Implementation of Synchronized Phasor Measurements for Dynamic State Power System Monitoring and Fault Identification

“…For the power ow calculation, accurate measurement of magnitude and phase angle is important. For the elimination of harmonics in the current waveforms analog lters can be used, but these lters introduce some time lag in the measurements, measurements are not faster, and due to the aging effect the harmonics are not eliminated properly [13]. Instead of analog lters digitalized phasor measurement technique is very useful to get the measurement of the fundamental component magnitude and phase angle [14].…”

Further Generalization and Approximation of Fractional-Order Filters and Their Inverse Functions of the Second-Order Limiting Form

“…As highlighted in [35], the issue of design stability for the inverse filters is an important topic. A different set of constraints have been proposed here to ensure the approximant's stable and minimum phase response as compared to the Hurwitz determinant method employed in [21].…”