Synthesis Of Filters Research Articles

Cell-Based Synthesis of Multiple Analog Filter and Oscillator Topologies Employing Graph

A new synthesis methodology, which offers design harmony of multiple analog filter and oscillator topologies is presented. Vertices of a bipartite graph are defined with simple mathematical function, denoted as cell. Weight of the edges are denoted by relation operator. A general theory has been developed based on graph and a set of traversal rules conjugated with cell, to produce multiple number of second-order function (SOF) in terms of cells. Theoretical approach has been facilitated with operational transconductance amplifier (OTA)-based circuit realization of multiple filter and oscillator topologies, and abridged with algorithm, which may lead to virtual EDA tool and field programmable analog array (FPAA). The proposed synthesis approach is validated with SPICE simulation.

ПРИМЕНЕНИЕ МЕТОДА КОРРЕКЦИИ БАЗИСА ДЛЯ УСТРАНЕНИЯ НЕОПРЕДЕЛЕННОСТИ ПРИ СИНТЕЗЕ ИНВЕРСНОГО ФИЛЬТРА

The process of linear filtering is considered as a process of representing a signal in an oblique coordinate system. An approach to the elimination of uncertainty of the "divide by zero" type in the synthesis of an inverse filter, based on the basis correction, is proposed.

Matrix Synthesis for Filters With Cascaded Extracted-Pole Sections

This letter proposes a direct matrix synthesis approach for filters with cascaded extracted-pole (EP) sections. The novel synthesis technique is based on the observation that an EP section is a special case of a singlet with a zero mainline coupling. With proper phase lengths inserted into a cross-coupled network, cascaded EP sections can be directly synthesized from the canonical wheel form by a sequence of elementary matrix operations. In this letter, the equation for the suitable phaselength is derived, and the matrix transformation strategy to synthesize cascaded EP sections is developed. Numerical synthesis examples are provided to validate the novel synthesis approach.

МЕТОДИКА И АЛГОРИТМ СИНТЕЗА УПРАВЛЯЕМЫХ ЦИФРОВЫХ ФИЛЬТРОВ ЧЕБЫШЕВА I РОДА НИЖНИХ ЧАСТОТ НА БАЗЕ МЕТОДА БИЛИНЕЙНОГО ПРЕОБРАЗОВАНИЯ

The article presents a technique for the synthesis of controlled digital recursive Chebyshev lowpassfilters of the first kind with an infinite impulse response. The frequency response of such filters hasripples in the passband and is as flat as possible in the stopband. Controllability is understood as anexplicit dependence of the filter coefficients on the cutoff frequency. The technique is based on the bilineartransformation of the transfer function of the analog low-pass filter prototype and the frequencytransformation of the amplitude-frequency characteristics of the obtained digital filter. The main idea ofthe technique is that for an analog prototype filter with a cutoff frequency of 1 rad/s, the parameters ofthe transfer function of biquadratic or bilinear links, which have the dimension of frequency, will benumerically equal to the correction factors for similar parameters of a controlled filter with an arbitrarycutoff frequency. As an example, the synthesis of a digital Chebyshev filter of the first kind of the fifthorder is considered. In this article, the transfer function of an arbitrary order filter is represented as acascade connection of II order links if the filter is of an even order. In the case of an odd order greaterthan one, one cascaded link of the first order is added. Despite the relative simplicity of the frequencyconversion, in its practical use for digital filters synthesized using computer-aided design of digital filters(or using reference books containing calculated prototype low-pass filters for various approximationsof the frequency response of an ideal low-pass filter), a series arises non-trivial specific momentsthat complicate the engineering use of this method of synthesizing controlled digital filters. Therefore, inaddition to the technique, a step-by-step algorithm has been developed that allows one to synthesize afilter without knowing these moments. The algorithm is implemented in the Mathcad environment; asan example, a digital recursive Chebyshev filter of the 1st kind of the 5th order is calculated.The example shows the calculated coefficients of a digital controlled low-pass filter, which explicitlydepend on the cutoff frequency, the amplitude-frequency characteristics of this filter and its lowfrequencyprototype converted into a filter with the same cutoff frequency, the amplitude-frequencycharacteristics are given in the same coordinates. Due to the good formalization of the algorithm, thelatter is suitable for the implementation of computer-aided design systems for controlled digitalChebyshev low-pass filters of the first kind.

Improved robust filter synthesis combining linear matrix inequalities and heuristic algorithms

AbstractThis article introduces an alternative and less conservative filter design procedure applied to continuous time uncertain systems. In order to provide a reduction in conservatism and an norm improvement, the proposed technique avoids the conventional convexification procedure—which uses structure restrictions and slack variables. Instead, it defines an unconstrained structure. The proposed technique consists of a hybrid procedure, combining the application of linear matrix inequalities (LMIs) with heuristic optimization algorithms (HOAs). The HOAs, specifically genetic algorithms, are used to optimize terms that could cause bilinearities, subsequently evaluated by LMIs and generating the desired filter. Numerical examples and a comparison with other methodologies are presented, testifying to the proposed method's efficacy and the performance.

Полосно-пропускающий фильтр на цилиндрических волноведущих структурах со сложными металлическими гребнями

This paper shows the possibility of using a circular waveguide with radial ridges and annular segments of finite thickness as resonant diaphragms in the synthesis of band-pass cylindrical waveguide filters. An electrodynamic calculation and design of a band-pass waveguide filter based on round waveguides with thin plane-transverse metal resonant diaphragms has been carried out. The analysis of the electrodynamic parameters of the diaphragm from its geometrical dimensions is carried out. The results of a study of the resonant properties of a single diaphragm are presented. The results of comparing the frequency response of filters obtained by computer simulation with the measured frequency response of manufactured prototype filters are presented.

A Robust Algorithm for the Design of Wideband Positive-Slope Linear Group Delay Filters

This article proposes a robust method for the synthesis and design of optimal linear group delay filters with prescribed bandwidth and dispersion properties. The proposed filters are based on a cascade of second-order all-pass filter cells, for which all the parameters are optimized in order to reach the desired wideband linear group delay characteristic with positive slope. Compared to the previously published synthesis method, the proposed approach offers appropriate initialization enabling convergence and aiming for the optimal solution. The method’s convergence and robustness are proved through a 21-cells synthesis, which is the highest number of cascaded cells reported to date, due to the usual convergence problem. Then the electronic feasibility is illustrated through the measurement results of a lumped-elements linear group-delay filter prototype dimensioned with this method. The measured group delay presents a positive slope of 8 ns GHz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−1</sup> in the frequency range [100–725] MHz. It is, to the best of our knowledge, the highest positive slope reported to date with an electronic implementation (i.e except SAW and waveguide devices).

Efficient Water Cleaning by Self-standing Carbon Nitride Films Derived from Supramolecular Hydrogels.

The design of efficient self-standing hybrid systems for water purification that combines good adsorption properties with high photodegradation ability is highly challenging owing to the difficulty in simultaneously controlling the band structure and porosity of a semiconductor while maintaining its self-standing nature. Here, we report the synthesis of carbon-rich carbon nitride self-standing filters from supramolecular hydrogels composed of melamine and cyanobenzoic acid. The influence of the chemical structure on the properties of the hydrogels and the final films was studied by tuning parameters such as monomer nature, molar ratio, and pyrolysis temperature. Thanks to their ability to combine the adsorption and photodegradation of organic pollutants, the prepared self-standing films showed remarkable activity and stability in flow conditions (>95 % efficiency after 10 consecutive cycles). Additionally, the photocatalytic activity of the films was assessed in the powder form for the hydrogen evolution reaction and photocurrent generation in a photoelectrochemical cell. The reported work opens opportunities for the controlled synthesis of multifunctional filters for water purification and other energy-related and sustainable technologies.

Novel filtering and diplexing linear tapered slot antenna with high-selectivity

In this article, a novel filtering and diplexing antenna using a linear tapered slot antenna (LTSA) are demonstrated. To begin, a highly-selective, second order bandpass filter is designed using generalized Chebyshev filter synthesis technique. Filtering and diplexing antennas are realized by co-designing the filter along with a wideband LTSA. The proposed filtering antenna exhibits 3.21% fractional bandwidth (FBW) over (4.29–4.43) GHz, high band-edge selectivity performance with 6 dBi flat in-band realized gain and stable end-fire radiation patterns with a low cross-polarization level of less than -30 dB. Further, a diplexing antenna with good bandpass filtering characteristics is also implemented. The design shows FBW of 3.32% (3.55–3.67) GHz and 3% (4.91–5.06) GHz and flat-radiation gain of 5.2 dBi and 5 dBi with sharp roll-off in Tx (lower) and Rx (upper) passbands, respectively. It also demonstrates good out-of-band suppression level of more than 20 dB, end-fire radiation patterns with cross-polarization lower than -27 dB and back-lobes lower than -14 dB for both the passbands. In order to validate their functionality, both the designs are fabricated and the experimental results correlate well with the simulated results.

Cu-boosted one-pot nanoarchitectonics for synthesis of polydopamine membranes as reusable laccase mimic

As a good alternative for natural enzyme, enzyme mimics with artificial functional materials have attracted considerable attention. However, it remains a great challenge to develop a facile method to design laccase mimic with high catalytic activity, long-term stability and reusability. In this report, we propose the one-pot synthesis of reusable paper filter templated Cu-doped polydopamine membranes (PF@PDA/Cu) with laccase-like activity. Compared with the natural laccase, the PF@PDA/Cu membrane exhibits enhanced catalytic activity for the chemical conversion of hydroquinone into benzoquinone. Interestingly, these membranes present good tolerance to high temperature and the catalytic activity increases with the increase of temperature. Moreover, these membranes could be stored for 7 days and recycled for 5 times with negligible loss of catalytic activity. This work provides a promising paradigm for rational design and practical applications of metal-loading PDA materials based on one-pot synthesis methodology.

A wideband omnidirectional planar filtenna for 5 GHz WLAN application

This paper presents a wideband planar filtenna based on the filter synthesis technique. The proposed filtenna consists of a third order hairpin line resonator filter coupled with an elliptical antenna. One arm of the last resonator of hairpin line resonator along with the extended feed arm of an antenna constitute an admittance inverter, which provides better integration between filter and antenna. The measured results show that the proposed filtenna exhibits a filtering response with impedance bandwidth of 26.5% (4.19–5.47 GHz), flat passband gain, good selectivity at band edges and omnidirectional radiation pattern well suited for WLAN application.

Improving the joint estimation of CO2 and surface carbon fluxes using a constrained ensemble Kalman filter in COLA (v1.0)

Abstract. Atmospheric inversion of carbon dioxide (CO2) measurements to better understand carbon sources and sinks has made great progress over the last 2 decades. However, most of the studies, including a four-dimensional variational ensemble Kalman filter and Bayesian synthesis approaches, directly obtain only fluxes, while CO2 concentration is derived with the forward model as part of a post-analysis. Kang et al. (2012) used the local ensemble transform Kalman filter (LETKF), which updates the CO2, surface carbon flux (SCF), and meteorology fields simultaneously. Following this track, a system with a short assimilation window and a long observation window was developed (Liu et al., 2019). However, this data assimilation system faces the challenge of maintaining carbon mass conservation. To overcome this shortcoming, here we apply a constrained ensemble Kalman filter (CEnKF) approach to ensure the conservation of global CO2 mass. After a standard LETKF procedure, an additional assimilation is used to adjust CO2 at each model grid point and to ensure the consistency between the analysis and the first guess of the global CO2 mass. Compared to an observing system simulation experiment without mass conservation, the CEnKF significantly reduces the annual global SCF bias from ∼ 0.2 to less than 0.06 Gt and slightly improves the seasonal and annual performance over tropical and southern extratropical regions. We show that this system can accurately track the spatial distribution of annual mean SCF. And the system reduces the seasonal flux root mean square error from a priori to analysis by 48 %–90 %, depending on the continental region. Moreover, the 2015–2016 El Niño impact is well captured with anomalies mainly in the tropics.

Finite-Frequency $\mathcal {H}_{-}/\mathcal {H}_{\infty }$ Memory Fault Detection Filtering Design for Uncertain Takagi–Sugeno Fuzzy Affine Systems

This article is concerned with the finite-frequency <inline-formula><tex-math notation="LaTeX">$\mathcal {H}_{-}/\mathcal {H}_{\infty }$</tex-math></inline-formula> memory fault detection filtering problem for discrete-time Takagi&#x2013;Sugeno fuzzy affine systems with norm-bounded uncertainties. The objective is to design a piecewise affine memory filter by using system historical information such that the resulting closed-loop filtering error system is asymptotically stable with the prescribed finite-frequency <inline-formula><tex-math notation="LaTeX">$\mathcal {H}_{-}/\mathcal {H}_{\infty }$</tex-math></inline-formula> performance. Based on the generalized Kalman&#x2013;Yakubovi&#x010D;&#x2013;Popov lemma combined with the celebrated <inline-formula><tex-math notation="LaTeX">$\mathcal {S}$</tex-math></inline-formula>-procedure, new sufficient conditions for the fuzzy affine filtering error system to have the finite-frequency <inline-formula><tex-math notation="LaTeX">$\mathcal {H}_{-}/\mathcal {H}_{\infty }$</tex-math></inline-formula> performance are given at first. By further using piecewise fuzzy quadratic Lyapunov functions and Projection lemma, the filtering analysis results for the filtering error system to be asymptotically stable with the prescribed finite-frequency <inline-formula><tex-math notation="LaTeX">$\mathcal {H}_{-}/\mathcal {H}_{\infty }$</tex-math></inline-formula> performance are obtained. Then, the filtering synthesis is carried out with the aid of matrix inequality convexification techniques, and the synthesis results are described in terms of linear matrix inequalities. It is further shown that a better filtering performance can be achieved by using more system historical information. Finally, simulation is provided to verify the effectiveness of the proposed approach.

Design of an Efficient 24–30 GHz GaN MMIC Power Amplifier Using Filter-Based Matching Networks

A broadband GaN MMIC power amplifier (PA) with compact dimensions of 1.94 × 0.83 mm2 is presented for 5G millimeter-wave communication. To guarantee output capability at the operating band edges where serious performance degradation is likely to occur, the appropriate large-signal matching model and optimal impedance domain need to be carefully determined through load-pull analysis. Broadband matching networks (MNs) in the lowpass form are thereafter developed based on the Chebyshev filter synthesis theory. Using high-pass interstage MN in conjunction with parallel RC lossy circuits to compensate for the transistor’s negative gain roll-off slope ensures a flat frequency response. The input MN is designed as a band-pass filter due to the reactance extracted from the input side of the stabilized device exhibiting series LC resonance characteristics. Measured on-wafer pulsed results for the proposed three-stage PA demonstrate up to 30.9 dBm of output power, more than 28.6 dB of small-signal gain, and a peak power-added efficiency (PAE) of 35.6% at 27 GHz. Both uniform gain and saturated output power (Psat) are achieved across 24–30 GHz with fluctuations of less than 0.8 dB.

Synthesis of resonance-based common-gate fully differential band-pass 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 are provided to validate the proper function of these filters.

An Actively Controlled Two-Terminal Network Implementing a Given Linear Nonconvolution-Type Immittance Operator

This paper is a study on the synthesis of digital filters used to control active or self-excited systems. The active two-terminal branch implements a nonconvolution-type immittance operator, which generates a current waveform depending on the given impedance or admittance operator. In this article, for the first time, the method of how to construct immittance operators for linear time-variant (nonconvolution-type) two-terminal circuits, over discrete time, is presented. These operators are useful when calculating periodic steady-state signals of a parametric circuit. The formula for the duty cycle is derived based on the current generated by this branch, assuming a known branch voltage or vice versa. This formula allows us to make a direct calculation of the duty-cycle in an analytical manner and does not refer to any auxiliary signals, e.g., sawtooth signals, or to any control systems, e.g., PI controller. The determined duty-cycles allow us to select the appropriate switching frequency and voltage value for the switched voltage source. With this method, it is also possible to assess the parameters of the current signal that would be generated in the actual active filter branch due to the calculated PWM voltage. The presented method can be an alternative to commonly used PI controllers in feedback for controlling active power filters/inverters.

Direct Coupling Matrix Synthesis for Filters With Cascaded Singlets

This article proposes a direct coupling matrix synthesis approach for filters with cascaded singlets. A sequence of elementary matrix transformations is applied in the synthesis procedure to obtain the target coupling topology containing many cross couplings and nonresonant nodes. Two filter synthesis examples are presented to demonstrate the novel synthesis technique. To physically realize synthesized coupling matrices, some singlets need to be transformed into their dual forms, which are also singlets but with different coupling coefficients. A 6–4 generalized Chebyshev filter is designed according to the synthesized coupling matrix, where the singlets are realized as oversized rectangular waveguide cavities employing nonresonant modes. Due to the cascaded singlet coupling configuration, the modular design technique can significantly reduce the simulation time. After the waveguide modules are assembled, the model-based vector fitting technique is applied to aid the fine-tuning of the filter. Both simulation and measurement results are in good agreement with theoretical filter responses, validating the proposed coupling matrix synthesis and design technique for filters with cascaded singlets.

Synthesis of dielectric-loaded waveguide filters as an inverse problem

ABSTRACT A design strategy is proposed for microwave devices built with dielectric-loaded waveguides having one- or two-dimensional discontinuity profiles. The problem is formulated as an inverse problem where the pre-defined scattering parameters are aimed to be the final response of the system. This goal is achieved by optimizing the dimensions of the filling materials. To increase the success of the optimization, the problem is reduced to the longitudinal and widthwise thickness determination of the unit cell, which constitutes the whole structure in a cascade form. To this aim, the frequency response of the unit cell is targeted and then that of the whole system, which is achieved by a two-level optimization procedure of the unit cell. The usefulness of the proposed design strategy is shown through numerical examples as well as the measurement results of two prototypes.

Synthesis of Extracted-Zero Filters

We present an exact synthesis procedure for the low-pass prototype of extracted-zero filters. This type of filter has been recently introduced and it allows the realization of a true inline topology with up to two transmission zeros. Compared to other inline (or quasi-inline) solutions, the one here considered is the simplest to dimension and fabricate (the same techniques used for all-pole filters can be adopted). The procedure here presented has been applied to the synthesis of various prototypes and the results confirm the effectiveness of the proposed concept. A filter previously realized in a quasi-inline configuration has been re-designed in the new topology and the results obtained with the two topologies are compared and discussed.

Synthesis of Parametrically Coupled Networks

We show that a common language can be used to unify the description of parametrically-coupled circuits--parametric amplifiers, frequency converters, and parametric nonreciprocal devices--with that of band-pass filter and impedance matching networks. This enables one to readily adapt network synthesis methods from microwave engineering in the design of parametrically-coupled devices having prescribed transfer characteristics, e.g. gain, bandwidth, return loss, and isolation. We review basic practical aspects of coupled mode theory and filter synthesis, and then show how to apply both, on an equal footing, to the design of multi-pole, broadband parametric and non-reciprocal networks. We supplement the discussion with a range of examples and reference designs.