Costas Psychalinos

University of Patras | UP · Division of Electronics and Computers (Department of Physics)

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 b...

NILES international conference is an annual conference hosted and organized by Nile University. It aims at providing a platform for researchers, engineers, academics, and industrial professionals to present their recent research work and to explore future trends in various areas of engineering and technology. The conference tackles 4 main tracks: E...

https://www.radioeng.cz/SI1_call_for_papers.pdf

This article presents an active realisation of an electronically controlled FO capacitor or a constant phase element (CPE) and an FO inductor (FOI) in the form of an integrated circuit. The realisation is demonstrated using an OTA-C structure in AMS 0.35 μm C35B4C3 technology. The same core is used for both realisations of CPE and FOI, and the angl...

In this work, we consider the design of third-order oscillators that are built around a multi amplifier structure with two- or three-amplifiers topologies. We derive all the possible oscillators that could be constructed using combinations of RC or RLC elements and provide the oscillation frequency and the oscillation start-up condition in each cas...

A theoretical study of the behavior of some elementary first- and second-order functions, which are suitable for realizing negative group delay, is performed in this work. As both the gain and phase responses are simultaneously considered, important derivations related to the actual bandwidth of operation are derived accompanied by useful design ti...

There is an increasing need to implement neuromorphic systems that are both energetically and computationally efficient. There is also great interest in using electric elements with memory, memelements, that can implement complex neuronal functions intrinsically. A feature not widely incorporated in neuromorphic systems is history-dependent action...

A study of the behavior of the power-law negative group delay filters, accompanied by a comparison with their integer-order counterparts, is performed in this work. Employing a curve-fitting based approximation technique, the resulting integer-order rational transfer function is versatile in the sense that it has the same form independent of the or...

First‐order generalized filter designs which simultaneously offer implementation of the low‐pass, high‐pass, and all‐pass filters basic functions with scaling of the associated time constant are presented in this work. These have been achieved thanks to the employment of the shadow filtering technique, which enables the utilization of a “hidden fil...

What follows is a brief history of the Circuit and Signal Processing Section of Electronics: In 2018, this Section was divided from Electronics [...]

A novel kind of non-integer order bilinear filters, named double-order bilinear filters, is introduced in this work. They are based on the employment of two non-integer orders, offering the maximum design flexibility in comparison with their fractional-order and power-law counterparts. An attractive offered benefit is that this is achieved without...

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We propose a new class of nonlinear resonance networks which are modeled by standard second-order nonlinear differential equations of the Levinson-Smith type or its subset, the Liénard type. In particular, we modify series and parallel RLC resonance networks such that the passive resistor in these networks is composed of a fixed part and a variable...

The approximation of the frequency behavior of fractional-order, power-law, and double-order filters can be performed by the same rational integer-order transfer function. This can be achieved through the utilization of a curve fitting based approximation. Moreover, their implementation can be performed by the same core, by only changing the corres...

A systematic method for approximating the complex‐order Laplacian operator by realizable integer‐order transfer functions is presented in this work. The realization is performed by a simple structure where only one active element is used. Thanks to the employment of complex‐order impedances, both integrators and differentiators can be readily imple...

In this work, we show that a pinched-loop can be observed in the voltage-current plane when a series R-L circuit is current excited. Specifically, the resistance (R) in this circuit is variable and is voltage-controlled by the voltage developed across the inductor due to the exciting current. In this context, we confirm our previous results that th...

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 offere...

Supercapacitors are mostly recognized for their high power density capabilities and fast response time when compared to secondary batteries. However, computing their power in response to a given excitation using the standard formul{\ae} of capacitors is misleading and erroneous because supercapacitors are actually non-ideal capacitive devices that...

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 Amplifi...

In this paper, a new versatile first-order voltage-mode analog filter using a single multiple-input voltage differencing differential difference amplifier for extremely low-voltage supply and low-frequency applications is presented. Using multiple-input MOS transistor technique, the filter can realize the first-order transfer functions of non-inver...

Non-integer order filters can be derived from a generalized structure presented in this work. More specifically, fractional-order and power-law filters of single- or double-order are special cases of non-integer order filters with three degrees of freedom and can be implemented using a Current Feedback Operational Amplifier as the active element. T...

Complex-order controllers are a generalized version of conventional integer-order controllers and are known to offer greater flexibility, better robustness, and improved system performance. This paper discusses the design of complex-order PI/PID controllers to control the speed of an induction motor drive and an electric vehicle. The speed-tracking...

In this Letter we highlight some fundamental errors in the paper “Origin of the Curie–von Schweidler law and the fractional capacitor from time-varying capacitance” [J. Pow. Sources 532 (2022) 231309] by V. Pandey. In particular, with the use of the convolution integral of linear time-varying capacitance with the time-derivative of voltage (i.e. Eq...

Novel structures of fractional-order differentiation and integration stages are presented in this work, where passive resistors are not required for their implementation. This has been achieved by considering the inherent resistive behavior of fractional-order capacitors. The implementation of the presented stages is performed using a current feedb...

In this Letter, we introduce and experimentally verify a very simple tunable-phase oscillator structure based on cascaded standard filter sections. In particular, a standard inverting second-order low-pass filter is cascaded with a first-order bi-linear filter in a closed loop resulting in a third-order structure that can be made marginally stable....

Second-generation voltage conveyor structures, based on the employment of flipped voltage follower stages, are investigated and proposed in this work. The proposed core has the feature of offering extremely low or electronically adjustable input resistance and programmable outputs, enhancing the achieved design flexibility and versatility of this a...

The equivalence of fractional-order inverse filters with fractional-order controllers is demonstrated in this work. This is achieved by appropriately rewriting the filters transfer functions in order to clarify the correspondence between the gain and time-constant of the filters and the scaling factor and differentiation/integration constant of the...

The fractional‐order Laplace operator s±α=(jω)±α$$ {s}^{\pm \alpha }={\left( j\omega \right)}^{\pm \alpha } $$ has been used in recent years in many applications including the synthesis of fractional‐order capacitors and inductors as well as in fractional‐order filter design. However, the synthesis and application of fractional‐order impedances wit...

Non-integer power-law all-pass transfer functions, are approximated by suitable integer-order transfer functions in this work. The derivation of the integer-order transfer functions is based on the analytic expansion of the (non-integer) power-law transfer functions through the utilization of the binomial theorem. The offered benefit is the derivat...

Two different approximation tools for deriving integer-order rational transfer functions, which fulfill the loop-shaping requirements in fractional-order (FO) controllers used in mechatronic applications, are presented and compared in this work. The first one is based on the employment of a curve fitting-based tool offered by the MATLAB symbolic to...

First‐order low pass and high pass inverse filter topologies, offering simplicity and independent adjustment of the gain and the characteristic frequency, are introduced in this work. These features are offered thanks to the terminals properties of the second generation voltage conveyor. In addition, possible applications of these types of filters...

We propose a class of fully differential filters based on a common-gate differential amplifier cell in three different topologies. Our focus is on the synthesis of second-order band-pass filters and we found 53 possible circuits. All filters are resonance-based and have electronically tunable gain. Post layout simulations in 65-nm CMOS technology a...

A simple ultra-low-voltage realization of second-generation voltage conveyor (VCII) based on the employment of super source follower, as voltage follower, and of current follower is presented in this paper. Full CMOS realization of the proposed VCII contains only ten transistors and two biasing voltages except for DC power supply voltages. Thanks t...

We seek to generalize and study the well-known Warburg impedance element, which has an impedance proportional to 1/s (s=jω is the complex frequency), to a two-port impedance network. For this purpose, we consider an infinite binary tree structure inside which each impedance is treated as a two-port network. We obtain a Warburg impedance matrix, whi...

A structure suitable for implementing power-law low-pass and high-pass filter transfer functions is presented in this work. Through the utilization of a field-programmable analog array device, full programmability of the characteristics of the intermediate stages, as is required for realizing the rational integer-order transfer function that approx...

A generalized structure that is capable of implementing power-law filters derived from 1st and 2nd-order mother filter functions is presented in this work. This is achieved thanks to the employment of Operational Transconductance Amplifiers (OTAs) as active elements, because of the electronic tuning capability of their transconductance parameter. A...

The exploitation of fractional calculus in engineering applications requires the utilization of fractional-order elements. As there is no immediate access to such type of elements, emulators that proportionally imitate their behavior are developed. The realization of emulators of fractional-order elements is based on the approximation of their impe...

An attractive feature of fractional calculus is its application in various interdisciplinary fields, extending from biomedical and biological notions to mechanical properties. For their description, fractional-order models have outperformed the corresponding integer-order models, resulting in a more realistic behavior, due to the additional degrees...

A simple and direct procedure for implementing fractional-order filters with transfer functions that contain Laplace operators of different fractional orders is presented in this work. Based on a general fractional-order transfer function that describes fractional-order low-pass, high-pass, band-pass, band-stop and all-pass filters, the introduced...

Novel double-dispersion models based on power-law filters are introduced in this work. These models are based on standard first-order and/or second-order low-pass filter transfer functions (denoted as mother functions) and do not require the employment of the fractional-order Laplacian operator. An attractive benefit, from the flexibility point of...

Low-pass and high-pass non-integer shelving filter designs, which are suitable for acoustic applications, are presented in this work. A first design is based on a standard fractional-order bilinear transfer function, while a second one is based on the transposition of the integer-order transfer function into its power-law counterpart. Both transfer...

This paper describes the design of analog pseudo-differential fractional frequency filter with the order of (2 + α), where 0 < α < 1. The filter operates in a mixed-transadmittance mode (voltage input, current output) and provides a low-pass frequency response according to Butterworth approximation. General formulas to determine the required transf...

Fractional-order controllers have gained significant research interest in various practical applications due to the additional degrees of freedom offered in their tuning process. The main contribution of this work is the analog implementation, for the first time in the literature, of a fractional-order controller with a transfer function that is no...

A power-law compensator scheme for achieving robust frequency compensation in control systems including plants with an uncertain pole, is introduced in this work. This is achieved through an appropriate selection of the compensator parameters, which guarantee that the Nyquist diagram of the open-loop system compensator-plant crosses a fixed point i...

An alternative procedure for the implementation of fractional-order compensators is presented in this work. The employment of a curve-fitting-based approximation technique for the approximation of the compensator transfer function offers improved accuracy compared to the Oustaloup and Padé methods. As a design example, a lead compensator intended f...

A novel procedure for the circuit implementation of the driving-point impedance of frequency-domain material models, constructed from fractional-order elements of arbitrary type and order, is introduced in this work. Following this newly introduced concept, instead of emulating separately each fractional-order element in the model under considerati...

A novel procedure for the realization of a fractional-order PID loop-shaping controller, suitable for precision control of mechatronic systems, is introduced in this work. Exploiting appropriate tools, the controller function is approximated as a whole, leading to a simple form of integer-order approximation, when compared to the case where each in...

This paper presents a new multiple-input single–output voltage-mode universal biquad filter based on multiple–input operational transconductance amplifiers (MI-OTA). This work demonstrates that the multiple-input OTA–based universal filter can provide more filtering responses and other benefits, compared to conventional OTA–based one. The filter pr...

The success of fractional-order fractance (FOF) as a modeling tool in (photo)bio(electro)chemical systems can be readily gauged by the large body of research work that has been conducted over the past few years in terms of materials fabrication, building integer-order emulators of their behavior, as well as applications in filter design, controller...

Double‐exponent fractional‐order impedance functions are important for modeling a wide range of biochemical materials and biological tissues. Through appropriate selection of the two exponents (fractional orders), the well‐known Havriliak–Negami, Cole–Cole, Cole–Davidson, and Debye relaxation models can be obtained as special cases. Here we show th...

Recurrent ladder network models are encountered in the analysis of many natural systems including wave propagation in transmission lines, porous electrode/electrolyte interfaces and viscoelastic (bio)materials. Here we re-visit the equivalent impedance of self-similar ladder networks composed of two arbitrary impedances recursively arranged, with t...

The main goal of this work is to exploit different tools in order to approximate a general double exponent fractional-order transfer function. Through the appropriate selection of the two fractional orders of this function, different types of filters can be derived. The investigated approximation tools are either curve fitting based tools or the Pa...

The Cole–Davidson function is an efficient tool for describing the tissue behavior, but the conventional methods of approximation are not applicable due the form of this function. In order to overcome this problem, a novel scheme for approximating the Cole–Davidson function, based on the utilization of a curve fitting procedure offered by the MATLA...

A new category of fractional-order filters, realized without employing a fractional-order Laplacian operator is introduced in this work. This can be achieved through the utilization of an efficient curve fitting method which approximates the frequency-domain behavior of the filter and transposes the fractional-order transfer function into the integ...

Abstract--- Fractional-order shelving filter designs, which are used for preserving the spectral balance of the human sound perception, are introduced in this work. The main attractive offered benefit is originated from the fact that fractional-order filters offer an extra degree of freedom with regards to the slope of the stop-band attenuation, al...

This paper proposes a new design of a 2α-order fractional-order band-pass filter with a tunability feature. The proposed filter is approximated with the second-order approximations of the Continued Fraction Expansion and the Matsuda. The proposed circuit is used to realize the filter transfer function based on the Inverse Follow the Leader Feedback...

Ultra-low-voltage sinh-domain implementation of delayed inertial neuron is introduced in this paper. The complex dynamical behavior of the neuron has been verified using three different activation functions, namely tanh, unipolar sigmoidal and bipolar sigmoidal. The networks containing two and four neurons have been designed, and their complex dyna...

This paper introduces a fractional-order eardrum Type-II model, which is derived using fractional calculus to reduce the number of elements compared to its integer-order counterpart. The proposed fractional-order model parameters are extracted and compared using five meta-heuristic optimization techniques. The CMOS implementation of the model is pe...

The fractional-order lung impedance model of the human respiratory tree is implemented in this paper, using Operational Transconductance Amplifiers. The employment of such active element offers electronic adjustment of the impedance characteristics in terms of both elements values and orders. As the MOS transistors in OTAs are biased in the weak in...

A novel scheme suitable for the emulation of fractional-order capacitors and inductors of any order less than 2 is presented in this work. Classically, fractional-order impedances are characterized in the frequency domain by a fractional-order Laplacian of the form \(s^{\pm \alpha }\) with an order \(0<\alpha <1\). The ideal inductor and capacitor...

Fractional-order lead/lag compensator realizations, using Operational Transconductance Amplifiers as active blocks, are presented in this paper. Two different types of fractional-order transfer functions, derived from the integer-order lead/lag compensator transfer function, are used to describe the behavior of the fractional-order compensator. Bot...

The constant phase element (CPE) or fractional-order capacitor is an electrical device that has an impe-dance of the form ZðsÞ 1⁄4 1=C a s a , where C a is the CPE parameter and a is a fractional dispersion coefficient of values between 0 and 1. Here we show that in the time-domain the classical linear charge-voltage rela-tionship of ideal capacito...

In this paper, a new current-mode instrumentation amplifier with electronic tuning and low-voltage operation capabilities is presented. Simplicity is other important feature so that the whole circuit is composed of only 20 transistors. All the above have been achieved using MOS transistors biased in the sub-threshold region. The required current-co...

This paper deals with fractional-order controller implementations, which can be constructed by electronically controlled building blocks fully integrated on a single chip. The proposed DC motor controller structure offers 50% reduction of the active components count, compared to the corresponding already published counterpart. The proposed liquid l...

Voltage-mode and current-mode fractional-order filter topologies, which are capable of realizing various types of transfer functions, are introduced in this paper. Thanks to the employment of the transconductance parameter of the MOS transistors, the derived filter structures offer the benefit of the electronic adjustment of their frequency charact...