Filter Topology Research Articles

Compact Dual-Band and Wideband Filters With Resonant Apertures in Rectangular Waveguide

The objective of this article is to describe a new family of microwave bandpass filters in the rectangular waveguide based on resonant apertures, which can be used to implement both single- and dual-band transfer functions. The use of capacitive stubs and a staircase configuration is also discussed in order to enhance the out-of-band response and the selectivity of the filter with respect to the state of the art. Finally, simulations are compared with measured results, showing very good agreement, thereby fully validating both the new filter topologies and the design procedure.

Experimental Harmonics Analysis of UPS (Uninterrupted Power Supply) System and Mitigation Using Single-Phase Half-Bridge HAPF (Hybrid Active Power Filter) Based on Novel Fuzzy Logic Current Controller (FLCC) for Reference Current Extraction (RCE)

UPS Uninterruptible power supply) is used as backup when the input source, usually the national grid, fails to give power to a load. In addition to the growing use of electronic power devices in industrial and residential systems, such as UPS, controlled rectifiers, SMPS (Switch Mode Power Supplies), and DC Converters, there is a serious problem caused by harmonics in AC mains, which lowers the power quality. Harmonics can cause a variety of problems, including sensitive equipment failure, resonance issues, heated wires, power loss, and inefficient distribution systems. A passive or active power filter could be used to reduce harmonics. However, passive filters are more difficult to design and are bulkier. With the advancement of power electronics, active power filters were developed, and the best combination of both was supplied in the form of hybrid active power filters (HAPF). This study shows an approach to minimizing the harmonics contained in the output of a UPS connected to a nonlinear load. Experiments with several UPS types have been conducted under various nonlinear loads, as well as charging and discharging of batteries, and the proposed technique significantly reduces harmonics in a system with a HAPFs (hybrid active power filter) based on a unique FLCC (fuzzy logic current controller). In this paper, we use a fuzzy logic controller to generate pulse width modulation (PWM) switching signals in a single-phase half-bridge HAPF. The operation of the proposed PWM-FLCC will be studied in a steady and transient state. Based on a connection between the uninterrupted power supply (UPS) supplying a single-phase power to a nonlinear load, different power filter topologies and a brief review of reference current extraction (RCE) methods used in this study were also included and the most common configurations have been compared with their advantages and disadvantages to ensure the right selection of the power filter for UPS connected with the nonlinear load. The results of the investigation demonstrate that the HAPF with the fuzzy logic current controller has reasonable performance, with a significant reduction in current THD down to 1.09%, as per IEEE-519 standard.

Design of a small size C‐band cavity bandpass filter

AbstractThis letter proposed a new topology of a cavity bandpass filter, with which a C‐band small size bandpass cavity filter is realized. The filter adopts a capacitor‐loaded open terminal coaxial resonant cavity, the Q factor of which is greater than 7000, with the 50 Ohm coaxial lines as the input and output ports. By building an equivalent circuit, the coupling matrix is synthesized to obtain the characteristics between the resonators. The cascaded quadruplet section with inductive cross‐coupling and the folded structure is adopted to make the volume smaller and more compact than the traditional filter. The measured results show that the standing wave ratio of the filter in the whole 500 MHz passband is less than 1.22, and the rejection at 3500 MHz and 4500 MHz reaches −70 dB.

Coupling Matrix Designing of a Cross-Coupled ‎Resonator Waveguide Filter Based on a Fast ‎Tuning and Step by Step Optimization ‎Technique

This paper presents an efficient hybrid method of filter modeling that combines a fast tuning step to global optimization technique to design a new topology of a 4th order cross-coupled resonator bandpass microwave filter. The method can rapidly extract the coupling matrix from the electromagnetic (EM) simulated scattering parameters (S-parameters) of a rectangular waveguide resonator bandpass filter with losses that will be implemented in a computer-aided tuning tool to develop a high performance microwave bandpass filter design simulated by successively adding a one resonator each time of a set of sequential tuning iterations within the ANSYS-HFSS. This minimizes the time of designing of the microwave filter's structure as well as permits to ‎build a higher waveguide filter's order providing a complex ‎cross-coupling‎. A filter parameters’ manual-coarse adjustment is finally achieved by implementing a step by step optimization tool based on the EM-simulator as a fast process for ideal refinement to the partial circuital response.

A New Integrated Active EMI Filter Topology With Both CM Noise and DM Noise Attenuation

Integration of electromagnetic interference (EMI) filters is a good idea to further decrease the volume and weight of a power converter. However, the conventional research articles mainly focus on the integration of passive components or planar printed circuit board structures. This article proposes a new integrated active EMI filter (AEF) topology. It can attenuate both common-mode (CM) and differential-mode (DM) noise at the same time. Different from the traditional discrete CM AEFs and DM AEFs, noise sensing and cancelation of this proposed topology are performed simultaneously. The working principle and special features of this topology are analyzed in detail. Based upon the theoretical analysis, the insertion loss of this integration topology is close to the traditional separated CM AEFs or DM AEFs. Besides fewer components and dc power supply are demanded. A prototype is built and tested through experiments. Experimental results derived on standard test board and practical converter show good agreement to theoretical analysis.

A Fusion Topology of Higher Efficiency and Lower Capacity Hybrid Parallel Multi-Converters for Power Quality Compensation

In high-power applications, different multilevel voltage source converter (VSC) topologies are usually applied. The hybrid parallel multiconverters, which is a combination of multiactive and hybrid VSCs connecting in parallel, can be a promising solution in a high-power grid. In this article, the fusion VSC topology concept is proposed in which fusion VSC takes the advantages of both active (inductive coupling) VSC and hybrid (capacitive coupling) VSC. It corresponds to overcoming the insufficient-capacity problems when active VSCs are employed alone and vice versa. This article proposes fusion active power filter topology by combing active and hybrid power VSC through their equivalent model for power quality compensation. With the proposed VSC's equivalent model, it can reduce the converter rating by 17%–80% compared with the conventional approaches. Additionally, the corresponding control algorithm is proposed for the FAPF for power quality compensation. Finally, the simulation and real-time digital simulator hardware-in-the-loop experimental results of the proposed FAPF topology are given to demonstrate the validity and effectiveness for reducing its capacity and power loss compared with the conventional multi-VSC in power quality compensation.

Passive Filter Topologies for Grid Connected and Standalone PV Systems: A Survey

A passive filter is often necessary in grid connected and standalone distributed generation systems to reduce harmonics on the inverter output voltage/current waveforms. This article presents a survey of passive filter structures used along with voltage source inverters in grid connected and standalone systems. The paper brings in the salient features of existing passive filters throwing their merits and demerits. In literature, intensive work has been performed on the identification of new passive filter topologies with features including reduced elements, lower losses, and reduced harmonics. New filtering techniques based on the traditional schemes have also been proposed for easy control, less complexity, and reduced harmonic distortion. In this paper, a review of such newly developed filter topologies is carried out. This work would constitute a base for selection of a particular filter structure, which serves an essential component in standalone and grid connected applications.

CFOA‐based simple mixed‐mode first‐order universal filter configurations

AbstractThis brief communication presents two current feedback op‐amp (CFOA)‐based simple first‐order mixed‐mode universal filter topologies—one of them providing first‐order low‐pass (LP), high pass (HP), and all pass (AP)—all the three filters in voltage‐mode (VM)/trans‐admittance‐mode (TAM) while the other one realizing the quoted three functions in current‐mode (CM)/trans‐impedance‐mode (TIM). Except the all pass filter realization from the first configuration which needs a second CFOA also as gain‐of‐two amplifier, in all the remaining cases of both the configurations, only a single CFOA is needed. The other notable features of the circuits are employment of only three resistors and a grounded capacitor (as preferred for IC implementation) and the availability of independent tunability of the gain (H0) and cut‐off frequency/pole frequency (ω0) of all the three filters, in both the cases. In spite of not offering ideally infinite input impedance in VM/TAM mode and ideally zero input impedance in CM/TIM mode, the circuits still possess easy cascadability due to providing a voltage output from a low‐output impedance terminal W while the current output from the high output impedance terminal Z. Non‐ideal and sensitivity analyses have also been carried out. The workability of the proposed circuits has been demonstrated through PSPICE simulations and experimental results using the commercially available AD844‐type IC CFOA.

A 3rd-Order FIR Filter Implementation Based on Time-Mode Signal Processing

This paper presents the hardware implementation of a 3rd-order low-pass finite impulse response (FIR) filter based on time-mode signal processing circuits. The filter topology consists of a set of novel building blocks that perform the necessary functions in time-mode including z−1 operation, time addition and time multiplication. The proposed time-mode low-pass FIR filter was designed in a 28 nm Samsung fully-depleted silicon-on-insulator FD-SOI process under 1 V supply voltage with 5 MHz sampling frequency. Simulation results validate the theoretical analysis. The FIR filter achieves a signal-to-noise-plus-distortion ratio (SNDR) of 38.6 dB at the input frequency of 50 KHz consuming around 200 μW.

MOSFET-C transimpedance filters with center frequency tunability feature

ABSTRACT In this paper, seven different MOSFET-C transimpedance filters with their corresponding transfer functions and basic filter specifications, are provided. Presented designs show second-order standard band-pass, low-pass, or high-pass characteristics. Moreover, some filters provide both low-pass and band-pass characteristics. Especially, having a tunability feature makes a design more useful and applicable for various communication and instrumentation systems. The selected filter topology was biased under various biasing conditions to tune central frequency by keeping bandwidth constant. To elaborate the design with different aspects, we checked its small-signal performance by introducing both changing temperature and implementation errors. The theoretical results are in detail verified by numerous simulations using Cadence IC6 Spectre analog design environment. In the design, transistors with 1.8 V supply voltage were used and modelled by the SilTerra Malaysia 180 nm CMOS process parameters. The implemented layout, including metal-insulator-metal on-chip capacitors, occupies an area of 175 μm × 75 μm, while the total power consumption of the filter is found to be only 128.86 μW.

Voltage Differencing Buffered Amplifier-Based Novel Truly Mixed-Mode Biquadratic Universal Filter with Versatile Input/Output Features

In this paper, a first-of-a-kind mixed-mode universal filter employing three VDBAs and three passive components, is proposed. The filter operates in all four modes and provides all five filter responses, namely voltage-mode (VM), current-mode (CM), trans-impedance-mode (TIM), or trans-admittance-mode (TAM). Additionally, the same filter topology can also work as a CM single-input-multi-output (SIMO) filter. A state-of-the-art comparison of various ‘voltage differencing’ variants of the voltage differencing buffered amplifier (VDBA)-based SIMO/MISO (single-input-multi-output/multi-input-single-output)-type biquad filters further highlight the significance of the presented research. In the proposed no passive component matching is required for generating the filter responses. The filter circuit also provides inbuilt tunability of the quality factor independent of the pole frequency. The non-ideal frequency dependent gain and component sensitivity analyses of the filter were also performed. The Silterra Malaysia 0.18μm process design kit (PDK) is employed to design and validated the proposed VDBA-based filter using the Cadence design software. The simulation results closely follow the theoretical predictions. To further verify the practical feasibility of the proposed filter, an experimental evaluation is also completed. The VDBA-based filter is implemented using off-the-shelf operational transconductance amplifiers Intersil CA3080, Texas Instruments LF356 op-amp, and Analog Devices AD844s. The filter is designed for a characteristic frequency of 100 kHz. The time and frequency domain measurement results indicate the proper functioning of the filter.

Analysis of LCL Filter Topologies for DC-DC Isolated Cuk Converter at CCM Operation

In this study, the application and analysis of LCL filter topologies including an LCL, an LCL with damping, and an LCL trap filter used by a DC-DC isolated Ćuk converter operated at CCM are presented. The converter is designed for 50 W with 42 kHz switching frequency using a SiC MOSFET as a power switch. Although LCL filter topologies are commonly used with an inverter, their use in DC-DC converters has not been studied in detail. The main contribution of the paper is the application, design, and analysis of an LCL trap filter, which is not presented for a DC-DC converter in the literature, as an input filter of a DC-DC isolated Ćuk converter. For exact analysis of the effect of the filter, as a second main contribution of the paper, a state-space average mathematical model, small signal analysis of an isolated Ćuk converter for CCM operation, which was not presented before in the literature, is derived and its transfer function is obtained. In this paper, the practical design and transfer functions of LCL-based filter topologies are also presented. In order to analyze the effect of filter topologies by using linear methods including root locus and Bode graphs, the transfer function of the converter is cascaded with the transfer function of each filter separately, which is the third contribution of the paper because such analysis has not been presented in the literature. Furthermore, each cascaded transfer function and the transfer function of the converter are validated by step responses. All LCL filters, with an LC filter for comparison, are employed in the experimental setup. Owing to the applications, control characteristics and input current ripples are measured. In addition, the efficiencies of each different structure are determined. As a result of the analysis and measurements, the LCL trap filter gives better results in terms of efficiency (86%) and input current ripple (0.96 A peak). Moreover, the LCL with damping filter gives poorer control characteristics, but the maximum gain of the controller avoiding the instability of LCL with damping is 0.0855, which is higher than that of the others. Furthermore, it is shown that each LCL filter topology provides a 45% lower total inductor value compared to the LC filter.

Analysis of current harmonics compensation using various active filter topologies

The technological requirements in the industrial and domestic sectors greatly depend on the sensitive and controllable electrical and electronic equipment to meet the application-specific demands, the usage of these nonlinear devices inherently contribute to the degradation of electric power quality, among the various power quality disturbances, Harmonics, which significantly contribute to the waveform distortion has gained the attention among the researchers due to its negative impact on the entire power system network. Hence, the suppression of harmonics has been the focus area in the present context. The paper presents an overview on circuit configuration of three active power filter topologies, delta connected Shunt active filter, Delta-connected Fixed Capacitor Thyristor Controlled Reactor (FCTCR) and delta connected Hybrid filter. Paper also investigates the effectiveness of instantaneous active reactive power theory, Synchronous reference frame theory And Adaptive detection algorithm as control strategies for the suppression of the harmonics under different power system network conditions. Results of the simulation studies are presented in the paper to assess the performance of designed filter with different control strategy for the mitigation of current harmonics in the proposed power system network, simulation studies are carried out using MATLAB/SIMULINK.

Advanced System Analysis and Survey on the GPS Receiver Front End

A fully integrated GPS receiver system can enable unique system capabilities by synthesizing both receiver front end and baseband on the same chip, leading to lower area overhead and higher integration. A survey on the GPS receiver system that focuses on front end design is presented in the paper. The first section discusses the various global navigation satellite system (GNSS), followed by the GPS working section. Afterwards, the paper discusses the previous works on the GPS receiver front end design. It provides a detailed survey and classification of various receiver architecture, including the LNA, mixer, filter, and ADC topologies. Besides, several image rejection techniques are presented for more than 50 GPS receivers. The various performance parameters of the GPS receiver front end in the literature are presented with the graphical view in the state-of-the-art discussion section. This literature survey provides the most extensive compilation to date of the various topologies, techniques and explains their implementation in the GPS receiver system. A new figure of merit that includes all the system parameters is proposed. The FOM can be an excellent reference to enhance the research work in the field of GPS receivers. In the end, the paper describes the possible research scope and challenges associated with the design of the GPS receiver front end.

Multi-Band Bandpass Filter Using Novel Topology for Next-Generation IoT Wireless Systems

The design of single- and quad-band Bandpass Filter (BPF) topology has been presented in this paper for next-generation Internet of Things (IoT) devices. The main topology is constructed using the Split Ring Resonator (SRR), separated by the Anti-Parallel Coupled Line Structure (APCLS). A detailed analysis of APCLS has been presented, which is further used to construct the single- and quad-band BPF. The single-band BPF design consists of SRR loaded with APCLS. The developed single-band BPF displays a dual-mode response with a center frequency of 2.65 GHz and a measured fractional bandwidth of 17.17%. Moreover, a quad-band bandpass filter has been achieved using the same topology with minor modification in the SRR and APCLS electrical parameters. The developed quad-band BPF generates a dual-mode response having center frequencies of 1.2, 2.4, 3.5, and 4.7 GHz with the measured fractional bandwidth of 13%, 26%, 16%, and 5%, respectively. Two prototypes have been fabricated on the high-frequency substrate to validate the proposed topologies. Very high rejection in the stopbands region, little in-band insertion loss, and very selective passband have been measured for single- and quad-band BPFs. The measured and simulated results are well correlated.

Highly-Miniaturized Dual-Mode Bandpass Filter Based on Quarter-Mode Substrate Integrated Waveguide With Wide Stopband

This paper presents a novel design of a highly-miniaturized dual-mode bandpass filter (BPF) employing a quarter-mode substrate integrated waveguide (QMSIW). The QMSIW resonator is based on a square cavity with metallic vias along two sides, and open-ended edges at the remaining sides that contain orthogonal feed lines. An open slot is introduced along the two sides of the square cavity with metallic vias to form a magnetic wall. A single metallic via is assigned at the corner of the two open-edged sides to form an electrical wall, which produces different resonances. By loading a slot diagonally, the mode frequencies can be controlled independently, which allows us to realize a second-order BPF. The detailed design steps and a flowchart explaining the filter’s topology evolution are presented. The eigen-mode analysis, field distributions, coupling matrix, and full-wave simulation of the proposed QMSIW filter topology are used to determine the filter’s operating principle. To verify the proposed theory, a second-order BPF is realized, fabricated, and demonstrated experimentally. The BPF prototype exhibits excellent performance such as a small footprint of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.019\lambda ^{2}$ </tex-math></inline-formula> , a wide passband of 34.8-percent, low insertion loss of 0.43 dB, and a wide stopband of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.36f_{0}$ </tex-math></inline-formula> with a rejection level greater than 20 dB. Excellent consistency is found between the EM-simulated and measured responses of the device.

Wideband, Low Profile Coupling Suppression Circuit for Simultaneous Transmit and Receive System Based on Hybrid Finite Impulse Response and Resonator Topology

In-band full-duplex (IBFD) systems can double the spectral efficiency by enabling simultaneous transmission and reception within the same band. Key to realizing full-duplex radios is the cancellation of the self-interference (SI) that couples from the transmitting antenna into the receiving path. This is done by introducing a self-interference cancellations (SIC) circuit to significantly reduce the coupled transmit signal and avoid receiver’s desensitization. Additionally, SI suppression becomes more challenging across broader bandwidths. This paper presents a novel, wideband, and low profile SIC circuit based on a hybrid Finite Impulse Response (FIR) and resonator filter topology. The latter is optimized to provide an average of 22dB cancellation across 800MHz in the L-band. Conventional, SIC circuits require a filter bank with at least two FIR filters to achieve such a wide bandwidth. Conversely, our FIR resonator design is low profile with a circuit size nearly half of that of a filter bank. Simulations show a minimum cancellation of 15dB and a maximum cancellation of 45dB. A prototype was fabricated and tested, showing an average of ~ 20dB cancellation which is in good agreement with our simulation. Further, measured results show a minimum cancellation of 15dB and maximum cancellation of 27dB.

3D-Printed Electromagnetic Band-Gap Band-Pass Filter Based on Empty Single-Ridge Waveguide

In this work, a new method for the design of band-pass filters in an empty waveguide by using periodic structures is presented in a theoretical and experimental way. The proposed filter topology uses a periodic profile of two heights in the central part of an Empty Single-Ridge Waveguide (ESRW) for the generation of an Electromagnetic Band-Gap (EBG), and it provides simple unit cell design parameters to produce specific dispersion characteristics. The implementation of two band-pass filters with different fractional bandwidths (36% and 55%) and different characteristics in the rejection band is proposed, where to minimize the mismatch in the ESRW filter’s passband, a tapering technique is used that follows a Kaiser distribution for the EBG. To experimentally validate the design concept, a band-pass filter with a fractional bandwidth of 55% centered on 5.45 GHz is manufactured, using a low-cost 3D printer, which allows the rapid manufacture of complex geometries at a very reduced price. The experimental results validate the simulated response of the implemented ESRW band-pass filter.

A Generalized Analytical Tuning Approach for Model Predictive Controlled Grid-Tied Converters Under Wide Range of Grid Inductance Variation

In medium-high power applications, the LCL is the preferred filter topology to attain efficient power conversion. The filter provides a high damping attenuation of -60 dB/decade above the resonance frequency at the cost of a higher order plant, complex parameter design, and, increased vulnerability to un-modeled disturbances. Recently, model predictive control applied to power electronic converters has experienced great interest from researchers. The technique is tailored to the control of complex MIMO systems such as the LCL filter as it allows simultaneous regulation of several state-variables via a user defined cost function. However, the tuning of weighting factors (WFs) within the cost function is not trivial, and in most cases employs an empirical procedure. This paper presents an analytical procedure for tuning of WFs for indirect model predictive current controlled grid-tied converters. The method is based on using analytical closed-form expressions, that relate closed-loop poles of the filter with WFs via physical plant parameters. The presented expressions generalize the tuning of WFs to any arbitrary LCL design. The proposed method is validated by hardware-in-the-loop simulations conducted on PLECS RTBOX 3. Through experimental testing, it is shown that the controller is robust against a wide range of grid impedance variation.

Reconfigurable Non-Foster Elements and Squint-Free Beamforming Networks Using Active Transversal Filter-Based Negative Group Delay Circuit

A new type of reconfigurable negative group delay (NGD) circuits based on active transversal filter topology is introduced in this work. By incorporating varactors with the NGD circuit at the input and output ports of active transversal filter based on distributed amplifiers (DAs), one can notably enhance the tunability for both amplitude and phase responses, thereby enabling NGD characteristic synthesis with a wider reconfigurable range. In this article, the proposed reconfigurable NGD circuits are applied to create both tunable non-Foster elements and tunable squint-free beamforming networks, which are verified by experiment. Furthermore, a general <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> -stage transfer function for the proposed reconfigurable NGD circuit is derived, in which a two-stage particular case is given as an illustrative proof-of-concept example. Based on the reconfigurable NGD circuits, a prototype of a tunable negative capacitor is fabricated and measured, of which the capacitance can be tuned from −1.0 to −4.0 pF over a bandwidth of 100 MHz at 1 GHz or around 10% relative bandwidth. In addition, such an NGD circuit is utilized to create a low-dispersion superluminal transmission line, which enables a reconfigurable series antenna feedline for squint-free beam steering. Experimental results show that the main beam of the NGD antenna array has a tuning range from −15° to 15° within a squint-free bandwidth of 100 MHz at 2 GHz or within a relative bandwidth of around 5%.