Efficient Filter Design Research Articles

Efficient microwave filter design using differential evolution algorithm with chain local search in MOEA/D framework

Efficient microwave filter design using differential evolution algorithm with chain local search in MOEA/D framework

Chirped Managed Laser for Multilevel Modulation Formats: A Semi-Analytical Approach for Efficient Filter Design

Chirped Managed Laser for Multilevel Modulation Formats: A Semi-Analytical Approach for Efficient Filter Design

An efficient equalization filter design approach for the accurate sound reproduction in a room environment with wide-band content

In some sound reproduction applications, a desired sound field needs to be reproduced by remote loudspeakers in a room with sufficient accuracy over a wide frequency band. When low-frequency room modes exist and the low-frequency content is required to be reproduced accurately, an equalization filter with a long time-domain response may be necessary, resulting in a filter with a significantly high filter order, especially when the sampling rate is high for the high-frequency content. This imposes computational challenges on both filter design and implementation. In this article, a convex formulation is proposed for the wide-band sound reproduction filter design. To address issues due to the low-frequency room modes, a reduced-order technique is then proposed based on a sub-band filter structure where a low sampling rate is used to equalize the low-frequency room mode characteristics, and a high sampling rate is used for high-frequency features which usually has a short time span in response. The computational time can be reduced by several orders of magnitude and the numerical stability can be improved when the proposed order reduction method is used to eliminate redundant orders. Simulation and experimental results confirm the accuracy and efficiency advantages of the proposed method.

Efficient Filter Design to Compensate Fabrication Imperfections in 6G Communication Systems.

In this paper, we present a consistent methodology for the reliable design of 6G-oriented filters with enhanced endurance to construction imperfections. The systematic formulation does not depend on the filter's operating frequency and employs a robust strategy for obtaining new roots and poles of the filtering function. Essentially, it requires that all the local maxima of the filtering function do not fluctuate beyond the design attenuation levels for a set of predefined roots/poles distortions. To this purpose, two novel algorithms for the derivation of the appropriate filtering functions are developed, in the prior basis, together with a versatile optimization criterion and a heuristic comparison approach that guarantee optimal outcomes. Specifically, the principal idea of the first technique is to accurately extract the roots of the new polynomial from a system of equations on condition that the maximum local peaks of the distorted (due to imperfections) initial polynomial are below a prefixed threshold, such as the unit. Conversely, the second method develops an alternative polynomial, compressed in the amplitude and frequency range, so that a similar prerequisite regarding the maximum local peaks, is satisfied. It is stressed that both methods are fully generalized and may be applied to any polynomial combination, without increasing the overall complexity. The proposed framework is successfully verified in terms of theoretical examples and the numerical simulation of realistic waveguide and mictrostrip line filters, operating at frequencies from 2GHz to 65GHz, which unveil its superiority over existing schemes and implementations.

Classifying spam emails using agglomerative hierarchical clustering and a topic-based approach

Spam emails are unsolicited, annoying and sometimes harmful messages which may contain malware, phishing or hoaxes. Unlike most studies that address the design of efficient anti-spam filters, we approach the spam email problem from a different and novel perspective. Focusing on the needs of cybersecurity units, we follow a topic-based approach for addressing the classification of spam email into multiple categories. We propose SPEMC-15K-E and SPEMC-15K-S, two novel datasets with approximately 15K emails each in English and Spanish, respectively, and we label them using agglomerative hierarchical clustering into 11 classes. We evaluate 16 pipelines, combining four text representation techniques -Term Frequency-Inverse Document Frequency (TF-IDF), Bag of Words, Word2Vec and BERT- and four classifiers: Support Vector Machine, Näive Bayes, Random Forest and Logistic Regression. Experimental results show that the highest performance is achieved with TF-IDF and LR for the English dataset, with a F1 score of 0.953 and an accuracy of 94.6%, and while for the Spanish dataset, TF-IDF with NB yields a F1 score of 0.945 and 98.5% accuracy. Regarding the processing time, TF-IDF with LR leads to the fastest classification, processing an English and Spanish spam email in 2ms and 2.2ms on average, respectively.

Tunable toroidal resonance based on hybrid graphene-metal metasurfaces

With the rise of artificial magnetism and metamaterials, toroidal resonance has gained much attention for its special properties. In this paper, we propose a novel hybrid graphene-metal metamolecule consisting of a square bracket-like resonator and two asymmetric U-shaped resonators. By applying various Fermi energies to graphene, the amplitude of electromagnetically induced transparency (EIT) can be efficiently manipulated, and the maximum amplitude modulation depth can attain 81% in the microwave region. Numerical simulations and theoretical analysis demonstrate that the dynamic manipulation is mainly induced by the active tuning toroidal resonance through the recombination effect of the conductive graphene. Also, the maximum group delay of 85 ps can be attained and controlled with the increasing Fermi energy. The proposed hybrid graphene-metal metamolecule and dynamically manipulating mode presents a novel modulating strategy of EIT-like analog based on the toroidal response, which has great application for the design of efficient tunable resonators, filters, and sensors.

Denoising electrocardiogram signals using multiband filter and its implementation on FPGA

The electrocardiogram (ECG) signal carries vital information related to cardiac activities. While measuring ECG using electrodes, the signal is contaminated with powerline interference (PLI) from harmonics, baseline wandering (BW), motion artefacts (MA) and high frequency (HF) noise. The extraction of the ECG signal, without the loss of useful information from the noisy environment, is required. Therefore, the selection and implementation of an efficient filter design is proposed. The Finite Impulse Response (FIR)-based multiband needs separate digital filters, such as Lowpass, Highpass, and Bandstop Filter in cascade. The coefficients of the FIR multiband filter are optimised using a least squares optimisation method and realised in a direct form symmetrical structure. The capability of the proposed filter is evaluated on a Physionet ECG ID database, having records of inherent noisy ECG signals. The performance is also verified by measuring the power spectrum of the noisy and filtered ECG waveform. Also, the feasibility of the proposed multiband filter is investigated on Xilinx ISE and the design is implemented on a field programmable gate array (FPGA) platform. A low order simple multiband filter structure is designed and implemented on the reconfigurable FPGA device.

Intensity-tunable terahertz bandpass filters based on liquid crystal integrated metamaterials.

In this paper, we demonstrate an intensity-tunable THz bandpass filter by introducing liquid crystal (LC) integrated with asymmetric frequency selective surface (FSS) and subwavelength metal gratings. Here, the tunable THz filter is derived from the inner polarization state conversion in composited devices, and the incident linear polarization can be converted into 90° orthogonal components. By controlling the LC orientation under the applied electric field with the metamaterial electrodes, the polarization conversion process can be actively modulated; thus, the polarization-dependent and tunable THz bandpass filter is achieved. Based on the multilayer design and the inner Fabry-Perot-like resonance mechanism, the LC-integrated metamaterials filter presents better filtering performance than the single FSS filter, and the Q-value is improved from 7.7 to 13.8 at the working frequency. Our simulated work paves the way for the design of new and efficient THz filters.

Power and delay efficient fir filter design using ESSA and VL-CSKA based booth multiplier

FIR filter plays a major role in digital image processing applications. The power and delay performance of any FIR filter depends on the switching activities between the filter coefficients (FCs) and its basic arithmetic operations (i.e., multiplication and addition) performed in the convolution equations. In this paper, a new FIR filter is designed using Enhanced Squirrel Search Algorithm (ESSA) and Variable latency Carry skip adder (VL-CSKA) based booth multiplier. The proposed ESSA algorithm selects an optimal FC by minimizing the switching activities of FC based on the ripple contents, power and Transition width parameter to meet the required specifications of FIR filter in the frequency domain. Also, the VL-CSKA based booth multiplier is proposed to reduce the delay of FIR filter with parallel addition of partial products (PPs). In this design, the VL-CSKA adders utilize variable size and compound gate-based skip logic to deduce the delay with low power. The proposed FIR filter is simulated in Xilinx working platform by developing Verilog coding. The simulation result shows that the proposed FIR filter outperforms the state-of-the-art FIR filters by consuming only 0.142 mW power with delay of 28.175 ns.

Architectural Exploration for Energy-Efficient Fixed-Point Kalman Filter VLSI Design

Efficient Kalman filter (KF) designs for real-time mobile applications, such as nano-drones navigation, robots localization, spacecraft orbit control, GPS positioning, image recognition, and multisensor data fusion for wearable systems, are key technology goals. The KF is a compute-intensive kernel composed of consecutive complex matrix operations, like multiplications and matrix inversions. The most complex block in the KF is the Kalman gain (KG) function, which involves matrices inversion at each iteration, applying the determinant matrix calculation and division operations. In this article, we combine architectural solutions of different types, for which balancing conflicting low-power and high-performance requirements aiming at real-time KF processing is a key design issue. The key finding in our architectural exploration herein presented is that the KF architectures in semiparallel and sequential forms offer the best balance of circuit area size, power dissipation, and processing speed. Compared to the state-of-the-art solutions, our KF architecture is more efficient, with 2.8 times fewer arithmetic operators, requiring 3.3 times fewer clock cycles. The usefulness of the developed KF in digital signal processing (DSP) is shown herein by simulations of system identification, noise elimination, and state estimation applications. These figures highlight the results of the KF architecture: the speed of adaptation for the system identification applications with root mean square error (RMSE) of 0.01 after 12 samples, precision level in noise elimination applications with RMSE of 0.13, and reliability in state estimation processes with RMSE less than 10% of system peak response.

FPGA‐based implementation of floating point processing element for the design of efficient FIR filters

Numerous applications based on very large scale intergration (VLSI) architecture suffer from large size components that lead to an error in the design of the filter during the stages of floating point arithmetic. Hence, it is necessary to change the architectural model that increases the design complexity and the time delay effect. The issue encountered in the VLSI architectures for finite impulse response (FIR) filter is the increased number of components, especially delay elements. For the VLSI architecture reconfigured with reduced register usage, this article provides the floating point processing element (FPPE) implementation with Cross-Folded Shifting. The proposed FIR filter system reduces the number of components in the circuit which increases the complexity and high delay rate in the logical operation. The system has a comparatively reduced delay rate and power consumption. Hence, an efficient fast architecture based on the FPPE method is developed in this paper.

An Efficient FIR Filter Design using DA based Speculative Residue and Reverse Computation RNS system

An Efficient FIR Filter Design using DA based Speculative Residue and Reverse Computation RNS system

VLSI design of efficient FIR filters using Vedic Mathematics and Ripple Carry Adder

Constant multiplications like SCM and MCM are the latest and frequently used for low-level including FIR implementation. Although SCM is used directly in the FIR power standard, MCM is implemented in the form of forwarding configuration. In all cases, half of the FIR infrastructure stores the MM domain area making the time, time and energy more efficient than using MCM and SCM. The existence of a system has, so far, revealed a great deal of ingenuity to the extent of its use and the time lost by half. The adder we are using in this structure is ripple carry adder (RCA) through which we have achieved more efficiency and much lesser intricacy. Thus to speed up the operation of filters, we are using Ripple Carry Adder and Vedic Multiplier.

Impact of bio-alcohol fuels combustion on particulate matter morphology from efficient gasoline direct injection engines

The requirements for controlling particulate emissions in gasoline direct injection (GDI) engines, particularly in hybrid vehicles (where frequent cold-start event impact on both, particles characteristics and catalytic aftertreament efficiency), nesesitates the need for understanding their formation mechanism and their morphological characteristics. The findings described in this investigation have significance in the design of efficient Gasoline Particulate Filters (GPFs) and the development of computational models that predict particle filtration and oxidation processes.Morphological analysis of the particulate emissions from the combustion of commercial gasoline and two bio-alcohol blends: of 25% v/v ethanol in gasoline and 33% v/v butanol and 67% v/v gasoline, in a modern GDI engine has been carried out using a transmission electron microscopy. The primary particle size distribution from the combustion of butanol-gasoline blend was slightly smaller compared to gasoline, while the mean primary particle diameter was 3 nm smaller from the combustion of ethanol-gasoline fuel. This decrease in primary particle size for ethanol-gasoline blend was also reflected in a reduction of the mean radius of gyration and mean number of primary particles per agglomerate.The combustion of butanol-gasoline blend induced improved particle oxidation rates during the combustion process and post-oxidation stage, and led in 80% and 60% reduction in particle concentration in the engine exhaust when compared to the combustion of gasoline and ethanol-gasoline blend, respectively. Additionally, the estimation of the particle fractal dimension through the use of fractal equation, minimum bonding rectangle method and root form factor showed comparable results for butanol-gasoline and gasoline, with the particle agglomerates being more compact than the ethanol-gasoline fuel, where more chain like particles are seen. Therefore, particles emitted from the combustion of ethanol-gasoline fuel are easier to be trapped (lower fractal dimension) and present a higher reactivity (high surface/volume ratio) compared to particles emitted from gasoline combustion.

A new approach for the design of fractional delay by an FIR filter

Fractional delay filters modeling non-integer delays are digital filters which ideally have flat group delays. In this letter, a new, simple, accurate and efficient FIR filter design to implement the digital ideal fractional delay is presented. The design technique is based on the MacLaurin series expansion formula which is applied to a given function to obtain a closed form FIR digital filter approximation of the digital ideal fractional delay operator z−α. The obtained FIR filter approximation formula of the digital ideal fractional delay operator z−α is similar to the well known Grünwald-Letnikov FIR digital filter approximation formula of the ideal analog fractional differentiator sα. Some examples have been presented to illustrate the performance and the effectiveness of this new design method. Some comparisons results show that the proposed design yields better performances than the existing designs in the literature.

A new approach for the design of digital frequency selective FIR filters using an FPA-based algorithm

Efficient digital filter design is an essential signal processing task. Finite Impulse Response (FIR) filters are used in many applications due to its properties of linear phase and frequency stability. Most traditional design methods suffer from the problem of insufficient control over the frequency response of the designed filter. For this reason, the use of a recently developed optimisation technique called flowers pollination algorithm (FPA), –based on the natural process of pollination of flowers– along with a novel multiple fitness function, is proposed in order to obtain optimised filter coefficients that best approximate ideal specifications. Results have been compared to both traditional methods (mainly windowing and the Parks-McClellan algorithm) as well as to several nature-inspired schemes. Finally, processing of a real EEG signal is used to quantitatively evaluate performance of designed filters. Numerical results show that our method achieves better fit to desired filter specifications, a 5−10 times larger attenuation in the stop band and a narrower transition band, at the expense of slightly increasing the pass-band ripple (5−15%) in 3 out of 4 of the cases.

SERIAL ADDER BASED MULTIPLICATION AND ACCUMULATION UNIT (MAC)

For efficient digital FIR filter applications, the Multiplication and Accumulation (MAC) unit is implemented by using various methods. In a digital filter, the MAC unit is one of the main units for performing multiplications and additions. This paper presents an efficient filter design for digital signal processing (DSP) applications with the reduction of carry propagation. In general, the performance of transpose filter mainly depends on the design of MAC unit. The design of a traditional filter consists of a large number of logical elements and has a high computational delay due to the conventional MAC unit. To design an efficient MAC unit, a serial adder is employed by using 2:1 multiplexer and a shifter block. The proposed work is implemented by using Xilinx ISE synthesis tool.

Efficient filter design against interrupted sampling repeater jamming for wideband radar

Interrupted sampling repeater jamming (ISRJ) is an effective coherent jamming, which can induce false high-resolution range profile (HRRP) and image to greatly complicate the target detection and recognition of wideband radar. To counter ISRJ, an efficient filter is designed based on the time-frequency (TF) characteristic differences between target echo and ISRJ. Meanwhile, a feasible jamming suppression scheme is proposed, which not only could eliminate ISRJ but also could reserve the target echo. The main emphasis is that the received echo suppressed by our scheme is similar with the true target’s HRRP on the basis of high correlation coefficient (CC) and large signal-jamming-to-noise ratio (SJNR) improvement factor. Simulation results are covered to illustrate the feasibility and validness of jamming suppression.

Design Space Analysis and $\rho$– $\eta$ Pareto Optimization of $LC$ Output Filters for Switch-Mode AC Power Sources

In this study, the design space (DS) concept is refined and utilized to design the output filter of a ${\rm 10}$ - ${\rm kW}$ , four-quadrant, three-phase, switch-mode controllable AC power source (CPS). The DS concept is based on the simultaneous consideration of multiple criteria that are derived from application-oriented specifications for the CPS regarding quality and transient response of the output voltage, and limited reactive power demand of the output filter. In this paper, the output filter of the studied CPS needs to satisfy six different criteria, which, in the case of a single-stage $LC$ filter, leads to bounds on the values of $L$ and $C$ that can be indicated by boundary curves in an $L\hbox{-}C$ plane. The intersection set of all boundary curves defines the DS, in which all six specifications can be fulfilled. For the considered requirements, it is shown that the DS is empty for a single-stage $LC$ filter, but exists for a two-stage $LC$ filter, which is therefore employed as an output filter of the CPS. To fully exploit the 4D DS of the two-stage $LC$ filter, a multi objective optimization, resulting in the power density–efficiency Pareto front, is performed to determine the most compact and/or most efficient filter design among all possible filter realizations with parameters in the DS. From the outcome of this optimization, the filter design with the highest power density of ${14.6}\, {\rm kW} / {\rm dm}^{3}$ ( ${239}\, {\rm W} /{\rm in}^{3}$ ), for an efficiency of $99.4\%$ , is realized in hardware. Finally, all six specifications for the CPS are successfully verified by experimental measurements.

Transmission and localisation in ordered and randomly-perturbed structured flexural systems

The paper presents a novel analysis of localisation and transmission properties of randomly-perturbed flexural systems. Attention is given to the study of propagation regimes and the connection with transmission resonances following perturbations of ordered stacks. The analytical study is complemented with numerical simulations relevant to different discrete systems. Applications are in the design of efficient vibration isolation systems and filters of elastic waves considered as ordered structures subjected to small random perturbations.