Filter Topology Research Articles

Tunable Impedance-Matching Filters

In this letter, we present a general design method for tunable matching networks that have a prescribed filter characteristic over a range of complex port impedances. The approach enables prediction of the achievable tunable impedance range, given a filter topology and tuning element values. As experimental validation, a 2.5-GHz second-order Chebyshev filter is designed using Skyworks SMV2205-040LF varactor diodes to tune the filter resonator and inverter. It is shown that the filter can match port impedances in a region that spans a range of real and imaginary parts of the impedance between 10 and 150 Ω with an insertion loss of 1.5 dB.

General method for synthesizing dispersive coupling matrix of microwave bandpass filters

AbstractIn this paper, a general method for synthesizing dispersive coupling matrix (DCM) of coupled-resonator bandpass filters with the general dispersion is proposed. Compared to the dispersion-less coupling matrix synthesized by classic approaches, the DCM incorporates the identity of the physical realization and provides an accurate description of the filter. Moreover, the DCM can accurately describe the complex resonators and coupling elements with intentional strong dispersion. A DCM consists of two parts: the frequency-invariant part that corresponds to the coupling matrix at the center frequency and the frequency-variant part that reflects the dispersion of the physical realization. By iteratively adjusting the transmission zeros governed by the given filter topology and ignoring the transmission zeros brought by the dispersion, the synthesis method can directly obtain the frequency-invariant part so that the overall DCM leads to an equal-ripple response. To illustrate the general synthesis method, two design examples are presented, which include a filter with unintentional weak dispersion and a filter with intentional strong dispersion. The examples are validated by EM simulation, demonstrating the effectiveness, accuracy, and generality of the proposed synthesis framework. Key words: dispersive coupling matrix, filter synthesis, microwave bandpass filter

Universal Filter Design Using 45 nm FinFET Technology-Based Floating Current Source

ABSTRACT Fin type Field Effect Transistor (FinFET) technology is a promising technology for single-digit nanometric dimensions. FinFETs are used to increase the performance by reducing the power consumption as the two gate voltages are controlled dependent and/or independently. This work explores the design of a Floating Current Source (FCS) using Double Gate (DG) FinFET and its application of a universal filter. The designed FinFET based FCS operates at 0.15 V power supply, the power consumption of the circuit is 51nW and bandwidth is approximately 100 MHz. The proposed FCS based filter circuit is simulated in LTspice with the FinFET 45 nm PTM-MG model. The filter topology behavior has been tested with an experimental study using the LM13700 integrated circuit and the experimental results are demonstrated. The proposed FinFET based circuit and its application can be used for the design of systems that require low power consumption and low chip area.

Design of Fast Locking and Locking Detection System of Frequency Synthesizer

In some electronic reconnaissance fields, fast frequency switching is required. A radio frequency signal generator with fast lock and accurate lock time appears to be of great significance. Traditional detection requires additional equipment, which is expensive and cumbersome to operate without portability. This paper designs a simple, portable and easy-to-operate lock detection method, uses a timer to monitor the LD pin of the phase lock chip in real time, optimizes the algorithm for capturing signal edge transitions, and calculates the frequency switching time. The ADF4351 fast lock mode is combined with lock detection to improve the topology of the loop filter and speed up the lock time. With the keyboard and LCD module, a radio frequency signal source system capable of self-checking and locking time is constructed. Simulation and actual results verify that after changing the filter structure to achieve quick lock, the lock time is optimized by 16%, which verifies the effectiveness of quick lock and the accuracy of lock detection, and realizes efficient and convenient lock time detection.

Electronically Tunable First Order AP/LP and LP/HP Filter Topologies Using Electronically Controllable Second Generation Voltage Conveyor (CVCII)

In this paper two new first order filter topologies realizing low-pass/all-pass (LP/AP) and low-pass/high-pass (LP/HP) outputs using electronically controllable second generation voltage conveyors (CVCIIs) are presented. Unlike second generation voltage conveyors (VCII), in CVCII each performance parameter, including ports, parasitic impedances, current and/or voltage gains can be electronically varied. Here, in particular, the proposed filter topologies are based on two CVCIIs, one resistor and one capacitor. In the first topology VLP/IAP/VAP and in the second topology ILP/VLP/IHP/VHP outputs are achievable, respectively. However, the current and voltage outputs are not achievable simultaneously and a floating capacitor is used. A control current (Icon) is used to change the first CVCII Y port impedance, which sets the filter −3 dB frequency (f0) of all the outputs. Moreover, in the second topology, the gains of HP and AP outputs are electronically adjusted by means of a control voltage (Vcon). Favorably, no restricting matching condition is necessary. PSpice simulations using 0.18 µm CMOS technology and supply voltages of ±0.9V show that by changing Icon from 0.5 µA to 50 µA, f0 is varied from 89 kHz to 1 MHz. Similarly, for a Vcon variation from −0.9 V to 0.185 V, the gains of IAP and IHP vary from 30 dB to 0 dB and those of VAP and VHP vary from 100 dB to 20 dB. The total harmonic distortion (THD) is about 8%. The power consumption is from 0.385 mW to 1.057 mW.

Comparison of Different Passive Filter Topologies for Harmonic Analysis of a Line Commutated Converter based HVDC System

Comparison of Different Passive Filter Topologies for Harmonic Analysis of a Line Commutated Converter based HVDC System

Optimized Filter Design for Common-Mode Current Reduction in Four-Wire Inverter-Fed Motors

Two optimized filter topologies for four-wire electric drive systems (EDSs) are proposed with smaller size, lower power loss, and larger common-mode (CM) current reduction than the usual filter topologies. It has been previously shown that using a four-wire topology reduces the CM current in a wide frequency range, when compared with the three-wire one. However, there still exist low- and high-frequency resonances in the transfer function between neutral and inverter output voltage, resulting in the increase of CM current. By means of the transfer function analysis, two types of optimized filter topology specified for the four-wire EDS are proposed. Unlike conventional CM filter (CMMF), the design of these two new filters also requires a serious consideration of the characteristics of motor and cable impedance. Based on the design procedure, these two filters are built with excellent performance of CM current reduction in the whole frequency range. Besides, compared with conventional CMMF used for three-wire EDS, they also show benefits, such as lower power loss and less implementation space. All theoretical analyses are validated by the experimental measurements and can benefit further studies.

Modular waveguide filter platform for educational and prototyping purposes

AbstractIn this paper, a modular waveguide filter platform suitable for educational and prototyping purposes is presented. The waveguide filter platform is dimensioned to work in the F-band (4.9–7.05 GHz). The design of the platform is discussed and versatile application possibilities are shown in many examples. The platform can be used to realize generalized Chebyshev filters with or without cross-couplings by exploiting TE101 and TE102 mode cavities. Transmission zeros can be introduced by the utilization of wires or aperture couplings. Filter topologies based on the extracted pole technique can be examined as well. Small changes in the set-up also allow the realization of a gap waveguide filter, a diplexer set-up as well as filters with frequency-dependent coupling apertures. Most required components can either be purchased cheaply or be manufactured with a three-dimensional printer.

Synthesis of active-RC filters using genetic algorithms

Traditionally, analogue filter designers synthesise their circuit topologies using pencil-and-paper method. Based on their previous experience, they generally use their intuition to reach proper network configuration for the desired filter function. However, this approach might be very time-consuming and cumbersome. With the advent of computer technology, the generation of analogue filters (or any other types of circuit for that matter) can be done using software. Taking advantage of this high computing power, some evolutionary methods, like genetic algorithms (GAs), can be employed to obtain the desired circuits sophistically, which generally leads reaching the goal faster. In this paper, automatic synthesis of filters utilizing GAs is presented. Although the approach can be applied to all analogue filters, this paper specifically focuses on active-RC filter topologies, which compose of an active element, e.g. operational amplifier, and resistors and capacitors. Some of the filter topologies that are generated by the constructed software are presented. Experimental results regarding to GA performance are also included.

A compound control strategy for LCL-based three phase four leg shunt active power filter

Conventional single inductor filter which is applied to three-phase four-leg shunt active power filter hardly meet the requirements for high frequency harmonic suppression. LCL filter has advantage both in high dynamic response and high frequency harmonic suppression. Repetitive control can realize accurate tracking of multi-harmonics signal. However, the design of corrector for repetitive control is mostly complicated. This paper proposes a topology of three-phase four-leg shunt active power filter based on LCL filter and improve its stability through capacitive current feedback. Compound control strategy which includes PI control and repetitive control is adopted to improve the compensation effect of harmonic current. Corrector for repetitive control has simple structure and is easy to design. The conventional PI control and compound control are compared and analyzed in detail. Moreover, the difference of property between LCL filter and single inductor filter is compared and analyzed. Simulation results show the correctness and effectiveness of the designed LCL filter and the proposed compound control strategy. The proposed method provides a reference for making three-phase four-leg shunt active power filter more practical.

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.

Modal filter design reducing the impact of sensors noise on the filter outputs

Discrete modal filters can be obtained as a weighted sum of the output signals from an array of discrete sensors installed in a flexible structure. Although several researchers proposed different design methodologies and implementation strategies for modal filters based on a particular array of discrete sensors, the noise component of these sensors was not analyzed and included in the design process. Therefore, this work presents a methodology to identify the topology of sensors and filter gains that minimize the noise component in the filter output. The experimental implementation of this methodology shows that an adequate topology of sensors can maintain the same level of noise from the sensors in the filter output. Furthermore, the noise at the filter output can increase considerably if other not suitable topologies are selected.

Performance comparison of hybrid active power filter for p-q theory and SVPWM technique

Harmonic Distortion in many of the industrial applications are occur primarily owing to the enormous utilization of loads with high non-linearity like power converters, speed varying drives and arc furnaces. The power semiconductor is used to achieve the variation in speed and conversion from one source to another. Mostly active filters and tuned filters are utilized to remove the harmonic included in the source current. The tuned passive filters and inductance inserted in the line reduces the harmonics but at the same time induces the resonances in most of the industrial applications. Due to this, harmonic distortion increases in the source current and voltage. This can be reduced by adding hybrid filter in the system with decreased rating of active filter in high power applications. This article deals with the various topology of hybrid filters. The working of the proposed filter design in variable inductance mode based on the pollution created in the source voltage and current is studied. In the proposed hybrid filter passive filter is tuned with seventh harmonic frequency and connected in series with active filters to reduce the harmonic distortion. DC link voltage and the active filter VA rating could be minimized. The control signal to the filter is derived from p-q theory and space vector pulse width modulation (SVPWM). The performance of the system under study is simulated and noted for the THD percentage before and after the filter is added to the system and the same model is experimented with reduced voltage level.

A Novel Evolution Strategy of Level Set Method for the Segmentation of Overlapping Cervical Cells

Development of an accurate and automated algorithm to completely segment cervical cells in Pap images is still one of the most challenging tasks. The main reasons are the presence of overlapping cells and the lack of guiding mechanism for the convergence of ill-defined contours to the actual cytoplasm boundaries. In this paper, we propose a novel method to address these problems based on level set method (LSM). Firstly, we proposed a morphological scaling-based topology filter (MSTF) and derived a new mathematical toolbox about vector calculus for evolution of level set function (LSF). Secondly, we combine MSTF and the mathematical toolbox into a multifunctional filtering algorithm 2D codimension two-object level set method (DCTLSM) to split touching cells. The DCTLSM can morphologically scale up and down the contour while keeping part of the contour points fixed. Thirdly, we design a contour scanning strategy as the evolution method of LSF to segment overlapping cells. In this strategy, a cutting line can be detected by morphologically scaling the union LSF of the pairs of cells. Then, we used this cutting line to construct a velocity field with an effective guiding mechanism for attracting and repelling LSF. The performance of the proposed algorithm was evaluated quantitatively and qualitatively on the ISBI-2014 dataset. The experimental results demonstrated that the proposed method is capable of fully segmenting cervical cells with superior segmentation accuracy compared with recent peer works.

Grid code compatibility and real-time performance analysis of an efficient inverter topology for PV-based microgrid applications

The integration of the Photovoltaic (PV) - based Distributed Generation (DG) Systems to the conventional electrical grid is a significant issue to achieve a confidential grid operation. This study presents a novel structure for the suppression of the common-state leakage current for PV-based inverters. It investigates the real-time performance of the inverter for the grid-code compatibility of the PV-based microgrid applications. Many of the topologies have been introduced to suppress leakage currents in grid-based Photovoltaic (PV) inverters, but most of them cannot practically reach more than 95% efficiency. The number of the components, especially the switching semiconductors, including the power switches and power diodes and the current and ripples' level in the topology filter side inductors, are essential criteria for efficiency. The proposed inverter includes six power switches and two power diodes. Since different operational states, only two power components per branch of the inverter are activated a higher efficiency than the conventional H5, H6, and HERIC converters. It presents the THD equal to 1,42 for load-connection states that is considerable. This converter can also generate pure sinusoidal current and voltage waveforms for the reactive loads, especially resistive-inductive load connections that are most common in industrial applications. As a study-case, the implemented inverter was tested under different grid conditions in the laboratory, and a real-time LabVIEW-based monitoring and grid protection system was realized within the research scope. Under/over-frequency protection and under/over voltage protection were performed to provide a reliable microgrid management system for the developed inverter. According to IEEE 929-2000 threshold values for the breakers' reaction operation under the ±10% as the output threshold voltage, the converter's performance is presented. A real-time monitoring and protection system are developed, and the developed LabVIEW analyzer has done the hardware test results. THD and spectrum analysis are also investigated in the real-time domain by the developed inverter test system. In this way, the implemented inverter's grid code compatibility is investigated in real-time, and the experimental results show that the proposed inverter is reliable for PV-based microgrid applications.

GENERAL STRUCTURE OF INTEGRATOR-BASED CONTINUOUS-TIME ACTIVE-RC FILTER AND APPLICATIONS

In the paper, a general structure of integrator-based continuous-time Active-RC filter is presented. More specifically, filter structures containing inverting amplifiers and passive feedback network are considered. The structure is analyzed using matrix description. The extensions of the model that take into account finite DC gain and finite bandwidth of operational amplifiers as well as other non-ideal effects are presented. The matrix-based approach is formulated especially for efficient use in computer analysis and design of Active-RC filters. An application example of the proposed approach to obtain OPAMP specifications for 3rd order low-pass Chebyshev filter for Analog Front End for VDSL is given. In this paper, we consider a general Active-RC filter topology suitable for computer-aided analysis, design and optimization of Active-RC filters. The structure is not the most general one, since it is restricted to filter topologies containing only inverting amplifiers (especially integrators) and RC feedback network.

Modeling and control of DC/AC converters for photovoltaic grid-tie micro-inverter application

• Modeling and control for a Photovoltaic-based microinverter system. • An efficient maximum power point tracking algorithm is implemented here. • Both state-space modeling and small-signal analysis are carried out. • Enhancement of transient and dynamic performance by using a cascaded controller. • Finally, a 500 Watts, 110 V, 50 Hz microinverter prototype is fabricated and tested. This paper is devoted to the modelling and control for a low cost, high-power quality single-phase voltage source inverter (VSI) for a grid-tied PV-based micro-inverter system. The first stage includes a high-efficiency isolated boost dual half-bridge dc-dc converter topology which interfaces to the PV panel and produces a dc-link voltage. The second stage is comprised of a single-phase VSI circuit. A state-space average model for a 1-Φ VSI with low-pass LCL filter topology has been developed. The steady-state and dynamic performance of the system can be improved by using three cascaded control loops. The fast inner current controller is adopted to regulate the inductor current of the inverter thereby improved dynamic response of the system. The small-signal analysis is conducted to assess the robustness of the proposed controller. An outer dc bus voltage control loop is employed to keep the constant voltage across the dc-bus capacitor. Next, the grid-side current loop is employed to regulate the grid current with a low total harmonic distortion level. The Bode-diagrams are plotted to assess the stability of each control loops. Finally, a 500 Watts, 110 V, 50 Hz micro-inverter prototype is fabricated and tested. The simulation and experimental results are given to show the effectiveness of the proposed control scheme.

Lossy Microwave Filters With Active Shape Correction

Obtaining the prescribed microwave filter response is highly desirable for proper frequency selectivity in RF transceivers. As the traditional microwave filter design methods do not take into account finite unloaded quality factors, lossy resonators cause significant deviations from the prescribed filter response, especially in filters with narrow bandwidths or of high orders. This deviation gets more severe as the resonator losses increase. Building on the lossy filter design techniques by using an active shape correction mechanism, this paper proposes a new approach to recover the filter response when the filter has moderately-to-highly lossy resonators. Being different than most active filter topologies, where all of the resonators are loss-compensated, this study aims at achieving the shape correction with $N-2$ active elements. To characterize the design, a novel lossy-active coupling matrix is introduced by extending the $(N+2) \times (N+2)$ lossy coupling matrix. The proposed theory is verified with the design and fabrication of two $3^{rd}$ order 5 % bandwidth filters operating at 1 GHz and employing resonators with quality factors of 100 and 28, respectively. It has been shown that the method can recover the response in both designs and the theoretical and measured responses are in good agreement.

Compensating Processing Delay in Excess of One Clock Cycle in Noise Shaping Loops Without Altering the Filter Topology

This work presents an analytical method to design a stable loop filter for a noise shaper with parasitic delays or poles in the loop. This method does not require an increase in the order of the loop or extra feedback paths and keeps the original poles and zeros of the noise-transfer function at the same location. The method has been applied to a low-pass loop filter with a parasitic unit delay and a band-pass loop filter with either three unit delays or a high-frequency pole, obtaining stable loop filters in all three cases.

A Dual Function Reconfigurable Bandpass Filter for Wideband and Tri-Band Operations

A dual-functional reconfigurable filter is explored for the application in wideband and triple band pass filter. The wideband configuration is implemented by parallel combination of open stub loaded and short circuited stub loaded resonators to exhibit a passband from 2.0 GHz-6.1 GHz. Tight coupling generates transmission zeroes at the either side of passband, which enhances the selectivity. The proposed tri-band BPF offers passbands at 2.4 GHz, 3.5 GHz and 5.2 GHz where two-stepped impedance resonators (SIRs) and one uniform impedance resonator (UIR) are assembled to accomplish such behavior. The two short circuited stubs are connected to the feed line to extend the range of upper stopband. PIN diodes are effectively utilized to switch the operation from wideband to tri-band or vice versa. Detailed design guidelines are provided to design the proposed filter. The behavior of the proposed filter topology is investigated by even and odd mode analysis. The developed reconfigurable filter is fabricated and measured to verify the anticipated and simulated results. A close agreement is observed between them. The fabricated reconfigurable BPF has a very compact size, high selectivity, less insertion loss and good return loss profile.