Synthesis Of Filters Research Articles

Synthesis of High-Selectivity Two-Dimensional Filter Banks Using Sigmoidal Function

This paper explores an application of the sigmoidal function—the complementary integral Gaussian error function (erfc(.))—in two-dimensional (2D) uniform and nonuniform filter bank synthesis. The complementary integral Gaussian error function graph represents a smooth low-pass filter magnitude response. A parameter changes the function slope and increases the magnitude response selectivity. The theory is applied to 2D band-pass filter banks. Exact expressions for the magnitude response parameters are determined. As a result, 2D uniform and nonuniform filter banks with very high selectivity and exact shapes are obtained. Three synthesis examples of 2D filter banks with circular and fan-shaped magnitude responses are provided. The theoretical exposition is supplemented with two examples of image analysis using 2D uniform and nonuniform filter banks. A procedure to reduce the computations in image analysis is proposed. A comparison of filter synthesis between Parks–McLellan’s 2D filters and the erfc(.) demonstrates the significantly shorter calculation time of the proposed method.

Synthesis And Efficiency Evaluation of Chitosan-Alginate Hydrogel Polyelectrolyte Complex Filter for Treatment of Oil Spillage

Crude oil spills pose considerable environmental concerns thereby demanding the development of effective, sustainable, and eco-friendly remediation solutions. In this study, we synthesized and evaluated the efficiency of a biodegradable polymer filter using sodium alginate and chitosan for the treatment of oil spillage. The sodium alginate-chitosan hydrogel polyelectrolyte complex (SACHPC) filter was synthesized via dipping method using a layer-by-layer self-assembly technique integrated with cotton wool as the filter medium. The efficiency of the filter was evaluated based on flow rate of recovered oil and reusability of the filter. Simulated oil spillage of 0.5 M was subjected to filtration using the SACHPC filter. The flow rate was determined based on the time taken for 1 L of oil to pass through the filter. The SACHPC filter exhibited underwater superoleophobic behaviour with exceptional filtration efficiency (> 98.3%) in acidic, neutral and alkaline conditions (pH 3, 7 and 11). The flow rate of the filter was 120 mL/min, while the third-use filter exhibited a decrease flow rate of 50 ml/min. Moreover, the filter achieved an impressive crude oil recovery rate of 85%. X-ray diffraction analysis confirmed crude oil adsorption in the presence of an amorphous phase while scanning electron microscopy analysis revealed the structural morphology of the SACPHC filter. Overall, the SACHPC filter maintained high filtration efficiency thereby offering a sustainable strategy for oily wastewater purification and oil spill clean-up.

Improving the color gamut of gold nanostructures using vertical tandem nano-disks

Metallic nanoparticles have been used in structural coloration applications since they provide an alternative for the synthesis of color filters, with extended color gamut, enhanced color saturation, and brightness. These optical properties can be further improved when integrating nanoparticles into coupled dimers that give rise to enhanced hybridized plasmon resonances. In this contribution, gold nano-disks are split into Au/SiO2/Au layered structures to enhance its plasmon resonances and evaluate its improved performance as reflective color filters. To do so, the reflectance spectra of the layered disks were obtained with numerical simulations, identifying high amplitude peaks in the visible band and low-amplitude peaks in the near infrared one, related to the hybridized resonances. By choosing the appropriate size of the intermediate dielectric and metallic layers, as well as the near-field coupling, peaks can be tuned along the visible and near infrared bands, respectively. The chromatic coordinates of the addressed nanostructures obtained from the reflectance spectra show that the nanostructures hold color gamut that extends toward magenta, orange, yellowish, and reddish shades of colors.

A compact low-profile substrate integrated waveguide wearable filtenna for 5G communication

We have proposed the design and synthesis of a compact, low-profile, flexible substrate integrated waveguide (SIW) wearable filtering antenna (filtenna) for 5 G communication, along with two parasitic resonator patches. We initially used a half-mode rectangular-shaped substrate-integrated (HMRSI) cavity as a resonating patch to minimize circuit size. The HMRSI cavity is located in close proximity to two parasitic truncated corner patches that serve as both the radiator and the final stage resonators, thereby optimizing filtering performance and expanding the operating bandwidth. The interaction of the parasitic patches with the HMRSI cavity produces one radiation null at the upper band-edges, while the corner truncation and notching on the parasitic patches with defected ground creates the other, enhancing the roll-off rate. Typical filter synthesis technology guides the design of the antenna. We have manufactured and measured an optimized prototype. The proposed flexible filtenna demonstrates excellent out-of-band selectivity, and its measurement aligns well with simulated ones, achieving an 8.2% fractional bandwidth (FBW), a maximum realized gain of 6.1 dBi, and a flat passband gain response. The proposed filtenna has also studied the human body and achieved a low specific absorption rate (SAR), which enables it to be an on-body wearable filtenna.

Best multiband filter problem

This mini-review examines the problems of geometric function theory that arise in the synthesis of electric filters, and in particular the work of A. A. Gonchar on the generalisation of Zolotarev’s third problem. The modern development of this topic is described, in particular the method of algebro-geometric Ansatz.

Helicopter Turboshaft Engines’ Gas Generator Rotor R.P.M. Neuro-Fuzzy On-Board Controller Development

The work is devoted to the helicopter turboshaft engines’ gas generator rotor R.P.M. neuro-fuzzy controller development, which improves control accuracy and increases the system’s stability to external disturbances and adaptability to changing operating conditions. Methods have been developed, including improvements to the automatic control system structural diagram which made it possible to obtain the system transfer function in the bandpass filter transfer function form. The work also improved the fuzzy rules base and the neuron activation function mathematical model, which significantly accelerated the neuro-fuzzy controller training process. The transfer function frequency and time characteristics analysis showed that the system effectively controlled the engine and reduced vibration. Methods for ensuring a guaranteed stability margin and the synthesis of an adaptive filter were studied, which made it possible to achieve the system’s high stability and reliability. The results showed that the developed controller provided high stability with amplitude and phase margins, effectively compensating for changes in external conditions. Experimental studies have demonstrated that the control quality improved by 2.31–2.42 times compared to previous neuro-fuzzy controllers and by 5.13–5.65 times compared to classic PID controllers. Control errors were reduced by 1.84–2.0 times and 5.28–5.97 times, respectively, confirming the developed neuro-fuzzy controller’s high efficiency and adaptability.

Active filter design and synthesis for hybrid neuro-fuzzy and robust PID controllers

Active filter design and synthesis for hybrid neuro-fuzzy and robust PID controllers

Multilayer UWB bandpass filter using liquid crystal polymer technology

This proposed design presents a novel bandpass filter employing a Marchand balun to attain ultra-wideband (UWB) performance extending from 3.1 to 10.7 GHz with 6.8 GHz central frequency and 110% FBW. The UWB bandpass filter’s fractional bandwidth can be tailored owing to the diverse input/output impedances of the planar Marchand balun. This adaptability is accomplished by connecting two planar Marchand baluns consecutively, leveraging the concepts of transversal filter ideas and multilayer LCP technology resulting in 0.3 dB and 12 dB insertion and return losses respectively. In-depth guidelines for the formulation and synthesis of the UWB bandpass filter are incorporated.

Positive functional filters synthesis for positive linear systems

Abstract This paper deals with the problem of positive functional $H_{\infty }$ filtering for positive linear systems subject to both bounded disturbances and unknown inputs. The order of the designed $H_{\infty }$ filter is equal to the dimension of the functional to be estimated, that can be useful for control purpose for example. We focus on the design of positive filters which guarantee that the functional (of the state) is always non-negative at any time and converges to the real functional state by minimizing the effect of the disturbances on the estimation error. In fact, we propose a new positive reduced order $H_{\infty }$ filter for positive linear systems for which the states remain in the non-negative orthant of the state space, subject to both disturbances and unknown inputs. This paper is a first attempt to design positive unknown inputs functional $H_{\infty }$ filter for such positive linear systems. The proposed approach is based on the positivity of an augmented system composed of dynamics of both considered system and proposed filter, on the unbiasedness of the estimation error by the resolution of Sylvester equation; then we derive conditions for the establishment of such filters in terms of an optimization problem. An algorithm that summarizes the different steps of the proposed positive functional $H_{\infty }$ filter design is given. Finally, numerical example and simulation results are given to showcase the effectiveness of the proposed design method.

Method for testing the stability of an autoregressive model of the vocal tract and adjusting its parameters

Within the framework of the traditional direction of research in the field of acoustic measurements, an autoregressive model of the vocal tract as a key link in the human speech apparatus is considered. The acute problem of ensuring the stability of the autoregressive model in systems with adaptation of its parameters to the observed speech signal of short duration is pointed out. To overcome this problem, the task was set of testing the stability of the autoregressive model and adjusting its parameters based on the results of this testing. The study is based on the author’s method of formant analysis of vowel sounds of speech through the synthesis of a recursive shaping filter in the free oscillation mode. To solve sated task, a method is proposed for testing the stability and adjusting the parameters of the autoregressive model of the vocal tract based on a two-stage algorithm for its transformation. At the first stage of transformation, the stability of the autoregressive model is tested using the impulse response of the shaping filter. At the second stage, if the stability of the autoregressive model is violated, its impulse response is modified by element-by-element multiplication by a variable exponential value that asymptotically converges to zero. A regular algorithm has been developed for recalculating the modified impulse response into an adjusted vector of autoregressive parameters at the second stage of transformation. Based on the results of experimental testing of the proposed method, it was concluded that guaranteed stability of the autoregressive model of the vocal tract has been achieved with minimal distortion in the frequency domain. The results obtained are useful in the development and modernization of automatic speech recognition systems, digital speech communications, artificial intelligence and other information systems that use data compression and speech coding based on an autoregressive model of the vocal tract in automatic speech signal processing.

General Matrix Synthesis for Cascaded-Block Filters With Flexible Bandwidth

General Matrix Synthesis for Cascaded-Block Filters With Flexible Bandwidth

A Novel Proximal Policy Optimization Approach for Filter Design

This paper proposes a proximal policy optimization (PPO) algorithm for coupling matrix synthesis of microwave filters. With the improvement of filter design requirement, the limitations of traditional methods such as limited applicability are becoming more and more obvious. In order to improve the filter synthesis efficiency, this paper constructs a reinforcement learning algorithm based on Actor-Critic network architecture, and designs a unique filter coupling matrix synthesis reward function and action function, which can solve combinatorial optimization problems stably.

Microstrip Quasi-Elliptic Absorptive Bandpass Filter with Ultra-Wide Reflectionless Range and Compact Size

Absorptive bandpass filters (ABPFs) are highly attractive in modern microwave communication systems due to their ability to internally absorb the harmful stopband RF-power reflections. This paper reports an approach to designing quasi-elliptic ABPFs with ultra-wide reflectionless range, enhanced selectivity, and compact size. The method is realized based on a fourth-order quasi-elliptic absorptive lowpass filter (ALPF) prototype with a simplified structure. This ALPF prototype exhibits both good impedance-matching over the whole normalized frequency domain and an adjustable transmission zero close to the passband. By applying an equivalent impedance transformer model, a coupled-line-based ABPF scheme is devised from the ALPF prototype, which eliminates conventional dispersive transmission line inverters, resulting in an ultra-wide reflectionless range and a compact size. Closed-form equations are derived to support the filter synthesis. A 2.45 GHz microstrip ABPF with 30% fractional bandwidth is designed for verification. The measured minimum in-band insertion loss is 0.83 dB and the reflectionless range of return loss better than 10 dB is from DC to 12.88 GHz. Both the upper and lower stopband suppression exceed 20 dB, with the upper stopband extending up to 6.80 GHz. The upper and lower out-of-band roll-off rates are 93.9 and 121.4 dB/GHz, respectively. The overall circuit size is 0.12 λg2.

Parameterization to fault detection filtering for Itô stochastic T‐S fuzzy systems

AbstractThis article focuses on the fault detection filtering problem for Itô stochastic Takagi–Sugeno (T‐S) fuzzy systems. In terms of line integral Lyapunov function, a sufficient condition of exponential stability in mean square and extended dissipativity for the systems under consideration is established which has less conservatism than the one based on quadratic Lyapunov function. The obtained sufficient condition is nonlinear, which makes the synthesis of fault detection filter being difficult and challenging. By choosing general matrix variables and constructing the appropriate orthogonal complement matrices, the nonlinear sufficient condition can be converted into linear one ingeniously via utilizing Finsler's lemma twice. Thus, the fault detection filter can be developed by virtue of parameterization. It should be pointed out that our filter determined by the parameterization approach includes the one obtained by the equivalent transformation method as a special case. Finally, we demonstrate the feasibility and superiority of our proposed approach through three numerical examples.

Алгоритми цифрової обробки кореляційних функцій у течешукачах

The article is devoted to the processing of cross-correlation functions. The need for this processing is due to a wide variety of interference conditions for searching for leaks in underground pipelines. Interference often significantly distorts the appearance of correlation functions and makes it difficult to accurately determine the coordinates of damage for pipeline repairs. Various approaches to combating these distortions are considered, depending on the available information about the characteristics of interference and leakage noise. Such features as the characteristic delay of the correlation function, which often corresponds to an interference burst and features of the frequency distributions of interference and leakage noise. An algorithm for extracting the leak coordinate from the correlation function as the coordinate of the source of a broadband signal by orthogonal decomposition of the CCF is considered. This problem is solved on the basis of classical approaches to the synthesis of shaping and synthesis of matched filters. The connection between the results obtained is shown. Thus, two approaches were used: one has the main goal of suppressing interference, without directly determining the coordinates of leaks, the other, on the contrary, is focused primarily on the selection of useful correlation of leak noises. In real-life conditions, it is advisable to combine both approaches due to the variety of acoustic environments encountered.

From the construction of wavelets based on derivatives of the Gaussian function to the synthesis of filters with a finite impulse response

From the construction of wavelets based on derivatives of the Gaussian function to the synthesis of filters with a finite impulse response

Mirroring Physical Reality: Nonconventional Microwave Filter Synthesis

Mirroring Physical Reality: Nonconventional Microwave Filter Synthesis

Millimeter-wave 3D-printed filtering power divider with high frequency selectivity and enhanced heat dispersion

In this paper, a 3D-printed filtering power divider with high frequency selectivity and enhanced heat dispersion is proposed in the Ka-band. Based on filter synthesis theory, a meticulous design is implemented for 32 rectangular resonators and their adjacent inductive irises, enabling the simultaneous realization of a 1-to-8 power divider function and an integrated 11th-order filtering response. To enhance heat dispersion performance for high power applications, cooling fins, and cooling slots are strategically incorporated into the filtering power divider. The selective laser melting (SLM) 3D printing fabrication technology is employed for the cost-effective monolithic fabrication of the prototype. The measured results demonstrate that the return loss of the input port is over 12 dB within the frequency range of 27.0–31.4 GHz. The phase and amplitude difference between outputs are less than ±8° and ±0.6 dB. The transmission coefficient is approximately 9.7 dB, indicating an excellent low-loss performance of the 1-to-8 power divider. Beyond the operating bands, the transmission coefficient experiences a decline of over 55 dB/GHz, demonstrating an 11th-order filtering response. The proposed filtering power divider excels in low loss, superior frequency selectivity, and enhanced heat dispersion, promising advancements in high-power millimeter-wave systems.

Design of planar metal stripline filter and diplexer with frequency‐dependent couplings

AbstractIn this letter, frequency‐dependent coupling (FDC) is introduced into the design of metal stripline filters and diplexers for the first time. FDC is a popular research method to introduce the finite‐position transmission zeros in the synthesis and design of filters in recent years. Finite transmission zeros are critical for filters to enhance the rejection ratios. To verify the realizability and effectiveness of FDC, a filter centered at 3.52 GHz and a diplexer operating at 2.55 and 2.65 GHz have been designed and fabricated. The planar filter and diplexer are compact in structure with multiple transmission zeros, whose resonators and cavity are integrated and formed, the cavity and cover plate are soldered together. We designed, assembled and tested the filter and diplexer, the synthesis results, the simulation results, and the tested results are well matched with each other. Compared with the dielectric waveguide filter, the planar stripline filter has better insertion loss, better harmonic suppression, and higher reliability, which is expected to be widely used in 5G base station filters.

Iterative Synthesis of Dual-Band Filters With Separately Assignable Operating Bands Using Bandpass Polynomials and Prototypes

Iterative Synthesis of Dual-Band Filters With Separately Assignable Operating Bands Using Bandpass Polynomials and Prototypes