Analog Active Filter Research Articles

Optimal Design of State Variable Filter using Partition-bound Particle Swarm Optimization

Because of manufacturing constraints, designing analog active filters is highly challenging. Evolutionary computing is an effective method for automatically selecting the component values like resistors and capacitors. This work describes the partition-bound Particle Swarm Optimization (PB-PSO) for efficiently designing second-order active low-pass state variable filter (SVF) considering different manufacturing series. PB-PSO is responsible for efficiently picking components and minimizing total design error. The filter components are chosen to be compatible with the E12/ E24/ E96 series. Compared to earlier optimization strategies, the simulation findings show that PB-PSO reduces the overall design error.

Synthesis of electronically tunable multifunction biquad filter using voltage differencing differential input buffered amplifiers

AbstractBiquad filters are commonly used in analog circuits for various purposes in signal processing and communication applications. We synthesize an analog active biquad filter with five types of voltage‐mode filtering functions. The filter is synthesized using a parallel passive resistor‐inductor‐capacitor (RLC) network and unity‐gain voltage differencing amplifier. A voltage differencing differential input buffered amplifier (VD‐DIBA) is the main active component, and the biquad filter has a three‐input single‐output (TISO) topology. By replacing the passive inductor and resistor with VD‐DIBA‐based inductance and resistance simulators with a subtractor, the TISO voltage‐mode versatile filter is obtained from two VD‐DIBAs, one resistor, and two capacitors connected to the ground. The proposed filter can provide five types of voltage‐mode filtering functions: inverting bandpass and lowpass responses as well as noninverting band‐stop, high‐pass, and all‐pass responses. The all‐pass filter requires no additional active components. The three input voltage nodes have high impedance, and a low‐impedance output voltage node facilitates cascade connections without using additional voltage buffers. In addition, the natural frequency and quality factor can be electronically tuned. The quality factor is controlled without disturbing the passband gain and natural frequency. The proposed filter is simulated and verified experimentally in the Personal Simulation Program with Integrated Circuit Emphasis (PSPICE) and through laboratory tests employing VD‐DIBAs implemented using commercially available components.

On the Design Flow of the Fractional-Order Analog Filters Between FPAA Implementation and Circuit Realization

This work explicitly states the design flows of the fractional-order analog filters that researchers throughout the literature have used. Two main flows are studied: the FPAA implementation and the circuit realization. Partial-fraction expansion representation is used to prepare the approximated fractional-order response for implementation on FPAA. The generalization of the second-order active RC analog filters based on opamp from the integer-order domain to the fractional-order domain is presented. The generalization is studied from both mathematical and circuit realization points of view. It is found that the great benefit of the fractional-order domain is that it adds more degrees of freedom to the filter design process. Simulation and experimental results match the expected theoretical analysis.

Application of Voltage Difference transconductance Amplifier (VDTA) for realization of analog active filter: Review

The paper reviews the published work for realization of analog signal processing circuits especially filters using VDTA as an active building block. VDTA is new active building block which has been used to realize the filters and other analog signal processing networks. Important advantage of ideal effects of VDTA is also presented. Moreover, various types of active filters employing VDTA is its electronic tuning of transconductance gain. At the outset of this review paper brief account of filters and their application is given. Detailed study including Non-VDTA is also presented.

State-space approach for symbolic analysis of an analog passive filter and its conversion to digital filter

The conversion of an analog filter described by a wiring diagram into another digital filter, having the same frequency characteristics was recently solved by a Python implementation. In this paper we will use this application for symbolic analysis of a passive filter having multiple components. Its conversion to digital filter is also described. Through experimental results we prove that the magnitude and phase characteristics are similar for the active analog filter and for the corresponding digital filter.

Noise Immunity-Enhanced Capacitance Readout Circuit for Human Interaction Detection in Human Body Communication Systems

Recent healthcare systems based on human body communication (HBC) require human interaction sensors. Due to the conductive properties of the human body, capacitive sensors are most widely known and are applied to many electronic gadgets for communication. Capacitance fluctuations due to the fact of human interaction are typically converted to voltage levels using some analog circuits, and then analog-to-digital converters (ADCs) are used to convert analog voltages into digital codes for further processing. However, signals detected by human touch naturally contain large noise, and an active analog filter that consumes a lot of power is required. In addition, the inclusion of ADCs causes the system to use a large area and amount of power. The proposed structure adopts a digital-based moving average filter (MAF) that can effectively operate as a low-pass filter (LPF) instead of a large-area and high-power consumption analog filter. In addition, the proposed ∆C detection algorithm can distinguish between human interaction and object interaction. As a result, two individual digital signals of touch/release and movement can be generated, and the type and strength of the touch can be effectively expressed without the help of an ADC. The prototype chip of the proposed capacitive sensing circuit was fabricated with commercial 65 nm CMOS process technology, and its functionality was fully verified through testing and measurement. The prototype core occupies an active area of 0.0067 mm2, consumes 7.5 uW of power, and has a conversion time of 105 ms.

DRLA: Dimensionality ranking in learning automata and its application on designing analog active filters

In this paper, a learning automata (LA) method is introduced based on dimensionality ranking (called DRLA), and its application for designing analog active filters is investigated. The basic idea in the DRLA is that the number of iterations and ordering selection of dimensions for the next phase is according to effect of each dimension in the fitness improvement of the current phase or previous phases. This strategy improves the exploration of search space and escaping the local minimums. Also, to achieve the proper balance in exploration and exploitation, the control parameter τ is changed by a linear control manner. To validate the applicability, accuracy, and performance of the proposed approach, it is first evaluated on 23 benchmark functions and then, as a new application of LA, applied to the optimal design of two different analog active filter topologies as real-world engineering problems. The filter component values are estimated within E96 series for resistors and capacitors, and a single-objective function is also considered as average quality factors deviation and cut-off frequency deviation. Simulation results compared to some rival single-objective metaheuristic optimization methods reveal that the improved method has competitive performance in terms of fitness, convergence, statistical analyses, box plot, and bode curve as well as runtime.

Design of an Oscillation-Based BIST System for Active Analog Integrated Filters in 0.18 µm CMOS

In this paper, an oscillation-based built-in self-test system for active an analog integrated circuit is presented. This built-in self-test system was used to detect catastrophic and parametric faults, introduced during chip manufacturing. As circuits under test (CUT), second-order Sallen-Key, Akerberg-Mossberg and Tow-Thomas biquad filters were designed. The proposed test hardware detects parametric and catastrophic faults on changeable limits. The influence of both oscillation and test hardware on fault detection limits were investigated and analyzed. The proposed oscillation based self-test system was designed and simulated in 0.18 µm complementary metal-oxide semiconductor (CMOS) technology. Due to the easiness of implementation and configuration for testing of different active analog filters, such self-test systems can be effectively used in modern integrated circuits, made of a large number of devices and circuits, such as the multi-standard transceivers used in the core hardware of software-defined radios. Using the proposed test strategy, the fault tolerance limits for catastrophic faults varied from 96% to 100% for all injected faults in different structures of low pass filters (LPF). The detection range of parametric faults of passive components’ nominal value, depending on the used structure of the filter, did not exceed –0.74% – 0.72% in case of Sallen-Key, –3.31% – 1.00% in case of Akerberg-Mossberg and –2.39% – 1.44% in case of Tow-Thomas LPF.

Energy efficiency digital filter design for spectral analysis of primary electrical values

In this paper, the knowledge based design of digital filter for analysis of spectral components is illustrated. The primary electrical values are analyzed observing of the faults which appear by earth short circuits. The main point of view is negative sequence component and higher harmonics in distributed electrical networks. Method of symbolic processing is used to design digital filter that realizes negative sequence component. Designing of digital filter is based on active analog filter in the three-phase electrical networks using bilinear transformation. We use methods of computer algebra tools (Mathematica) to simulate processes in network. Also, we automatically derive properties of digital filter, and the knowledge embedded in symbolic expressions was used to simulate an example system. The characteristics of digital filter are given and annotated using different sampling frequency and entire cases of earth short circuits.

Analog Filter Design: A Succinct Investigation

In many systems, it is essential to extract or enhance the desired information and remove the unwanted components. This is the simplest aim of signal processing where the filter turns out to be the key element. The objective of this paper is to investigate the characteristics of analog passive and active filters. Particularly, the interest goes to the conventional Butterworth, Chebychev and Bessel filter. A comparative study of these filters is done. The different circuits are simulated using the MULTISIM software to visualize the magnitude and phase responses. The procedure of designing the different filters is presented so that it can be used in any application.

Symbolic Analysis of an Analog Active Filter as Path for Conversion to Digital Filter

Abstract Recently have been reported methods to deliver a digital filter from an analog active filter, described only by its circuits diagram. The proposed approaches have been implemented in MATLAB and Python, and they were based on state-space conversion from analog to digital domain. Based on the Python approach, we show in this paper how to compute the transfer function of a large order analog active filter. The analog filter is described only by its circuits diagram. Finally, the analog filter is converted to the corresponding digital filter, having similar frequency gain and phase characteristics.

Optimal components selection for active filter design with average differential evolution algorithm

Component selection in electronic circuit design is an important issue to achieve a targeted performance and quality level. Particularly in filter circuits, changes in gain and phase response of the circuit are directly dependent on the component values of the filter. Therefore, the selection of component values must be done carefully. In this article, a differential evolution (DE) algorithm with a new mutation strategy, named as average DE (ADE), is introduced for analog active filter design. The ADE algorithm minimizes the total design error of the state variable filter (SVF) for the optimal selection of component values. Simulation results indicate that the proposed algorithm reduces the design error when compared to other methods.

Analog active filter design using a multi objective genetic algorithm

The selection of the correct values for passive elements, resistors, and capacitors, is an important task in analog active filter design. The classic method of choosing passive elements is a difficult task and can lead to errors. To reduce the incidence of error and human effort evolutionary optimization techniques are used to select the values of capacitors and resistors. However, due to the single objective optimization technique, these are not well suited to optimize different filter parameters. For this reason, the performance of a multi-objective genetic algorithm named non-dominated sorting genetic algorithm II (NSGA-II) against the different single objective algorithms is evaluated. Two analog active filters: A fourth order Butterworth and a second order state variable filter with the operational amplifiers in their cores are used for testing purposes. In both cases two different objects are chosen along with eight components as variables to be optimized. The component values are compatible with the E12, E24 and E96 series using NSGA-II. The computation results are better in terms of design error and allow for better resistor and capacitor choice. To reach the same or better results the NSGA-II needs fewer generations compared with other genetic algorithms for this problem.

A hybrid genetic algorithm for analog active filter component selection

Analog filters are circuits that process electrical signals on a frequency-dependent basis. Analog filter circuits can be implemented using resistors, capacitors and inductors and they can also be implemented with only resistors and capacitors with the use of active circuit equipments. The selection of optimum component values is difficult because of the number of possible filter combinations. This paper presents an effective algorithm that hybridizes the Genetic Algorithm (GA) to form a Hybrid Genetic Algorithm (HGA) and proposes the use of Tabu Search (TS) for the analog active filter component selection. The GA has a powerful global searching ability and so is used to perform exploitation and because TS also has good local searching ability, it too is applied to perform exploitation. Thus, the proposed HGA will have very good searching ability. In this study, a band-pass Sallen-Key filter circuit was used, and the filter component values were found using HGA with LabVIEW. The results are compared to other reported state-of-the-art algorithms, such as the artificial bee colony (ABC) and differential evaluation (DE) to demonstrate the effectiveness and efficiency of the developed method. It can be said that the developed LabVIEW based HGA gives satisfactory results with regard to amplitude response, the minimum fitness values and the computational time.

Optimal design of analog active filters using symbiotic organisms search

AbstractThis paper investigates the optimal design of analog active filters using the symbiotic organisms search (SOS) algorithm. Symbiotic organisms search is a newly proposed global optimization method that is inspired by the symbiotic interaction strategies between different organisms in an ecosystem. In SOS, the 3 common types of symbiotic relationships (mutualism, commensalism, and parasitism) are modeled using simple expressions, which are used to find the global minimum of the fitness function. Unlike other methods, SOS is free of tuning parameters, which makes it an attractive optimization method. Here, SOS is used to determine the values of the passive components (resistors and capacitors) used in active filters. Two active filter topologies, fourth‐order Butterworth low‐pass filter and second‐order state variable low‐pass filter, are considered. The components values are chosen from several standard industrial series (E12, E24, and E96). The results obtained using SOS are compared with those obtained using several optimization methods, like particle swarm optimization, seeker optimization algorithm, differential evolution, and other ones. It is shown that the SOS is a robust straightforward evolutionary algorithm that can outperform other well‐known methods.

Selection of Parameters of Bandpass Filtering of the ECG Signal for Heart Rhythm Monitoring Systems

This work is devoted to the bandpass frequency filtering of the ECG signal in heart rhythm monitoring systems against the background of disturbances and noises of various origins. It was suggested to optimize the procedure for selection of the bandwidth and the type of bandpass filter using the criteria for minimization of uncertainty in the measurement of the R-R intervals. Two different approaches to the bandpass filtering were considered: use of a second-order analog active filter and of an eighth-order digital filter.

A 5.2 mW IEEE 802.15.6 HBC Standard Compatible Transceiver With Power Efficient Delay-Locked-Loop Based BPSK Demodulator

A Low-power IEEE 802.15.6 human body communication (HBC) fully compatible transceiver is implemented in 130 nm CMOS process. In this work, the proposed HBC transceiver satisfying all the standard requirements has four key features for low power consumption which includes: 1) low-power analog active filters for TX spectral mask: 30% power reduction; 2) delayed locked loop (DLL) based BPSK receiver with the S/H operation for turning off unnecessary blocks: 40% power reduction; 3) low-power mode (LP-mode) receiver with the received signal strength indicator (RSSI) output data: 50% power reduction; and 4) reconfigurable LNA with RSSI output data: 60% power reduction. As a result, the proposed transceiver can fully satisfy the HBC standard requirements while consuming 5.2 mW from the 1.2 V supply.

Vortex search algorithm for the analog active filter component selection problem

Optimal selection of passive components is one of the most crucial design steps in analog active filter design problems. As the number of possible combinations increases, it becomes infeasible to perform an exhaustive search for optimum component values. Thus, intelligent algorithms are required for a fast and optimum selection of the passive component values. In this study, a newly proposed metaheuristic, the vortex search (VS) algorithm, is utilized for this purpose. To evaluate the performance of the VS algorithm, two different analog active filter topologies, the fourth-order Butterworth low-pass filter and the state variable low-pass filter, are used. The component values of the active filter topologies are selected within three different series of (E12, E24 and E96) passive components for both the resistors and the capacitors. The results are compared to other metaheuristics such as the particle swarm optimization (PSO2011), artificial bee colony (ABC), differential evolution (DE) and harmony search (HS) algorithms. It is shown that, the VS algorithm finds the minimum fitness values for both of the active filter topologies which in turn provides the optimum component values for each of the used component series.

Investigation of the optimum oscillation frequency value towards increasing the efficiency of OBIST approach

This paper is mainly focused on the investigation of the optimum value of the oscillation frequency in the Oscillation-based Built-In Self Tests (OBIST). It has been assumed that the proper frequency value might increase the test efficiency in covering hard-detectable short faults in analog integrated circuits (ICs) designed in nanoscale technology. In our research, active analog filters designed in 0.35μm and 90nm CMOS technologies were used as circuits under test (CUT). The tested circuits were brought to oscillation at different oscillation frequencies by varying the values of passive devices. The achieved results prove that the efficiency of OBIST approach can be increased in this way.

Analysis of the Parameters of Frequency Filtering of an Electrocardiograph Signal

The features of the processing of an electrocardiograph signal using band-pass frequency filtering on a background of distorting interference and noise of different kinds are analyzed. An approach to choosing the optimum passband and type of bandpass filter is proposed, based on the criterion of maximizing the signal-to-noise ratio at the filter output and minimizing the signal distortions, taking into account the variability of the heart rhythm. Two versions of such a bandpass filter are considered, namely, an analog active 2nd order filter and a digital 8th order filter.