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This chapter presents passive and active filter topologies and design techniques, including practical design examples and system simulations. In DSP systems, there are analog filters required for signal conditioning and limiting the bandwidth before sampling. To design these filters, designers need to be knowledgeable of operational amplifiers, DC biasing circuits, AC coupling techniques and traditional passive components like inductors, capacitors and resistors.

This work demonstrates a Continuous-Time (CT) Ladder filter using transconductance amplifiers as an approximate delay stage implemented on a large-scale Field Programmable Analog Array (FPAA) and characterized on an SoC FPAA. We experimentally demonstrate a reprogrammable CT Analog linear-phase filter by utilizing the ladder filter delay element and Vector-Matrix Multiplication (VMM) both compiled on the SoC FPAA. Using the Ladder Filter as a programmable CT delay operation enables a traditionally difficult analog signal operation. This effort extensively models and characterizes the ladder filter delay stage in terms of its transfer function, delay tunability, power requirements, distortion, and SNR. The theoretical development is compared to experimental measurements on an SoC FPAA with programmable ladder filter delay of $2.9\mu \text{s}$ and $4.2\mu \text{s}$ for multiple input frequencies (e.g. 5kHz, 20kHz). In addition, we show that VMMs can compensate the non-idealities found in the ladder filter delay-line operation.

In recent years, several current mode wave active filters have been reported in literature. However, most schemes only have a few higher-order filters that employ a wave equivalent inductor in a se...

The purpose of the work, the results of which are presented in the article, was to develop a computerized mathematical model of the ladder filter to study the features of the synthesis of matching chains of any order on its basis. To achieve this goal, all the synthesis tasks were solved, including the choice of the prototype, frequency transposition, calculation of the poles of the transfer function of the prototype, calculation of the poles of the transfer function of the filter, calculation of the reflection coefficient of the filter, the calculation of the input resistance of the filter, the implementation of the ladder chain by the Cauer method and denormalization of the values of the elements of the ladder chain. Modeling of characteristics of ladder filters of any high order with frequency characteristic of Chebyshev on the computer with 32-bit operating system is carried out. It is shown that the use of standard mathematics leads to a significant increase in the error of matching of loads at increasing the order of the chain. To increase the accuracy of calculations it is proposed to use software that allows implementing mathematical operations on variables with any length of the mantissa. There are computer libraries where numbers are presented in the form of string type variables and arithmetic operations are carried out on them according to school rules “ in a column ” . Once the calculations are completed, the strings are converted back to normal numbers. The article considers the application of the variant of BigNumber library for high level JavaScript language. To estimate the accuracy of the calculation it is proposed to apply the property of antimetric ladder structure. From the presented results of the calculation it follows that in order to obtain not less than 15 reliable digits after the decimal point for the parameters of the n-th order filter it is necessary to increase the length of the variable mantissa to the value 2n.

This work demonstrates how an acoustic wave ladder filter can place transmission zeros below the passband with some of its series resonators. This approach provides an additional degree of flexibility in the structure. Additionally, the same approach is applicable to filters starting in shunt resonator where some shunt resonators can be used to place transmission zeros above the passband. This novel concept, derived from an accurate synthesis approach, enables the design of advanced responses that are not restricted to having the transmission zeros evenly distributed between the upper and the lower stopbands thus achieving improved rejection and selectivity. Synthesized examples of these filters are shown and their Butterworth - Van Dyke model elements are provided.

$T$ - and U-shared links of ladder filters based on microelectronic BAW resonators with a Bragg reflector are considered. The BAW resonator with a piezoelectric aluminum nitride thin film operated at a frequency of 3.7 GHz and has a quality factor of 518 is fabricated. The analytical studies of the electrical characteristics of ladder filters are presented. It is shown that ladder filter with a relative bandwidth of the order of 1 % can be obtained based on the resonators with resonance bandwidth equal to 10…15 MHz. The minimum insertion loss of the ladder filter is -2.9 dB. The maximum guaranteed attenuation in the stopband at 5 % offset is -41.4 dB for a U-shared link with three BAW resonators.

In this paper, a class-J power amplifier for operation in the X-band realized in SiGe bipolar technology is presented. The proposed design combines the high efficiency of class-J operation with solutions to mitigate AM-PM distortion down to a level compatible with high spectral efficiency modulation schemes like 64-QAM. The design of a transformer-based output matching network and the trade-off between efficiency and pure class-J operation related to a non-ideal second harmonic termination are discussed. The main sources of AM-PM distortion are identified in the base-emitter and collector-based bipolar junction transistor capacitance variation with power level and solutions that make the design less sensitive to these impairments are proposed. Linear MIM capacitors are used at the power amplifier (PA) core output to realize the proper class-J second harmonic termination, while an input matching network based on a Bessel ladder filter is adopted to make the signal phase at the PA core input less sensitive to base-emitter capacitance variation. A class-J PA previously designed for maximum power-added efficiency (PAE) is used as a reference throughout the paper to highlight the trade-off’s entailed by AM-PM distortion reduction. The designed PA features a peak gain of 15 dB at 10 GHz and 8-to-12 GHz −3 dB bandwidth. The saturated power is 22 dBm with a 33% PAE, while the output $p_{1\,\text {dB}}$ is 19 dBm. The AM-PM distortion at $p_{1\,\text {dB}}$ is 5 degrees.

A bulk acoustic wave (BAW) filter for the N41 band (2535 MHz-2655 MHz) is designed in this paper. This design is a ladder filter based on the one-dimensional Mason circuit model of the film bulk acoustic resonator (FBAR). In order to improve the accuracy of the simulation results, the acoustic-electro magnetic joint simulation is performed, and the results are compared with the circuit model. The filter designed in this paper has a low insertion loss (less than 2.0 dB), a high out-of-band rejection (greater than 42 dB), a high-power capacity (greater than 30 dBm), and a small size ($1.1\times 0.9m$ m2).

Low-power analog filter banks provide frequency analysis with minimal power and space requirements, making them viable solutions for integrated remote audio- and vibration-sensing applications. Compared with their digital counterparts, analog filter banks are better suited to achieve the lower power consumption necessary for IoT applications. In this work, the design and implementation of a sub-threshold complementary metal-oxide semiconductor (CMOS) integrated low-power tunable bandpass filter channel for signal spectrum analysis and signal discrimination is presented, including performance improvements to stability and precise matching between filter stages. The 8th-order filter channel achieves an effective Q-factor of 4.5 and dynamic range of 60 dB, has an operational frequency range from 2 kHz to 100 kHz, and consumes 256 µW nominally at the highest center frequency. An integrated analog Gm-C filter topology is selected for this application. Functionally, the high-Q bandpass filter transfer function is implemented via four cascaded 2nd-order filter cells and is fabricated in 130-nm 1.2-V CMOS technology, making it suitable for use in monolithic integrated spectral analysis (MISA) applications.

This paper presents a BAW resonator structure, including the irregular shape and the frame region at the edge of top electrode to smooth electric response and suppress spurious modes. The NRN method based on Generalized Chebyshev Filter synthesis is introduced to design a BAW ladder filter. By controlling the location of the transmission zero, a higher isolation is obtained in the proper frequency domain. Using such methodology, Band 25 Rx BAW ladder filter is obtained with an insertion loss of 1.2 dB in the passband and an isolation of 52 dB in the Tx band.

This paper proposes and demonstrates a promising platform for Super High Frequency (SHF) Lateral Field Excitation Cross-sectional Lame Mode Resonators (LFE CLMRs) based ladder filters. These filters are simple to fabricate-relying on only 2 critical masks, have 2.5% fractional bandwidth, and allow different frequency bandpass filters to be fabricated on a single die. Individual resonators in AlN and 20% ScAlN operating at around 3 GHz are fabricated and compared, with electromechanical coupling coefficient (k t 2) and quality factor at series resonance (Qs) of 2.0-3.5% and 300–150 for AlN and 5.0-6.5% and 250–100 for ScAlN measured. 1, 2, and 3 stage ladder filters are demonstrated with ~2.5%fractional bandwidth and

In this work, a novel technique based on adaptive filtering is proposed for the control of a three-phase universal active power filter with a solar photovoltaic array integrated into its dc bus. Two adaptive filters along with a zero crossing detection technique are used to extract the magnitude of a fundamental active component of distorted load currents, which is then used in estimation of a reference signal for the shunt active filter. This technique enables extraction of an active component of all three phases with reduced mathematical computation. The series active filter control is based on synchronous reference frame theory and it regulates load voltage and maintains it in-phase with voltage at point of common coupling under conditions of voltage sag and swell. The performance of the system is evaluated on an experimental prototype in the laboratory under various dynamic conditions such as sag and swell in voltage at point of common coupling, load unbalancing, and change in solar irradiation intensity.

This paper proposes an analytical design procedure for the LLCL and the LCCL filters for grid integration of high-power voltage-source converters. The low switching frequency and stringent limits on grid-injected harmonics in high-power applications lead to large smoothing filters. In order to reduce the size and weight, high-order filters are already proposed and wise design procedures with the main goal of minimizing the overall filter size are being suggested. In this paper, the parameters of the LLCL and the LCCL filters are designed in the per-unit system to satisfy the requirements on the injected grid current and at the same time minimize the overall filter size through minimizing the total energy stored in the filter components. The experimental results of a downscaled laboratory prototype with a low switching frequency prove the effectiveness of the proposed design procedure.

Employing the LCL passive filter in inverter-based distributed generation to ensure high quality power delivery comes at the expense of poor performance due to the resonance phenomenon. Literature elucidated several active approaches to mitigate this phenomenon. This paper proposes a sensorless active damping technique that is able to restrain the resonant current component through the estimation of the filter capacitor current using the Kalman filter. The Kalman filter is able to improve the quality of the estimated variables in noisy environments accompanied with measurements and model uncertainties. The effect of LCL filter parameter mismatch on the performance of the Kalman filter is assessed. Stability and convergence analyses are also conducted. An effective tuning method for the grid current controller employing a proportional-resonant controller is adopted. Experimental evaluations were conducted to validate the proposed control strategy. 1 2017 Elsevier Ltd Scopus

In this paper, the use of MOS-only active filters in the implementation of area-effective low-IF image reject filters is discussed. For this purpose, complex filter design procedure is considered regarding MOS-only filter realization techniques and a new second-order filter topology which favors filter’s area-effective implementation is proposed. Owing to the presented approach, a new complex image-reject filter with reduced chip area, which can be used in dual-band GNSS receivers, is obtained. Issues related to IQ imbalance are briefly discussed and a calibration imbalance circuit is proposed. By virtue of the current-mode design technique, the IQ imbalance circuit is embedded with the complex filter, simplifying the system topology. In order to illustrate the feasibility of the filter, post-layout simulation results of a fourth-order Butterworth-type image reject filter designed for dual-band GNSS receivers are provided using SPECTRE simulation tool in CADENCE design environment.

Recently, many active filter circuits that use only MOS transistors were presented in the literature. In these circuits, instead of passive resistors, transconductances of MOSFETs operating in saturation region are used. Moreover, their parasitic gate to source capacitances are employed instead of passive capacitors. These circuits provide circuit implementation with fewer transistors and eliminate the need for external passive elements. In this study, a MOS-only third order Butterworth filter for high frequency applications has been proposed. The circuit leads to a compact circuit having fewer number of transistors compared to classical active block-based analog counterparts. Simulation results agree well with the theoretical study.

This paper presents a new realization of a grounded simulated inductor using a single dual output second-generation voltage conveyor (VCII±) as an active building block, two resistors and one grounded capacitor. The main characteristic of the proposed circuit is that the value of the series resistor can be significantly reduced. Thus, it has the property of improved low-frequency performance. Another feature is the use of a grounded capacitor that makes the proposed circuit attractive for integrated circuit (IC) realization. A simple CMOS implementation of the required VCII± is used. However, a single passive component-matching condition is required for the proposed structure. As an application example, a standard fifth-order high-pass ladder filter is also given. SPICE simulations using 0.18 μm CMOS technology parameters and a supply voltage of ±0.9 V as well as experimental verifications, are carried out to support the theory.

In this paper, a very simple topology of a current mode MOSFET-only filter with single-input and multi-output is proposed. It is very important to emphasize that it is possible to obtain five of the filter functions, namely low-pass (LP), band-pass (BP), high-pass (HP), band-stop (BS) and all-pass (AP) using the proposed topology without using external passive elements. The core circuit of the proposed filter employs only four MOS transistors; therefore, it occupies very small chip area. It is also possible to adjust the filter gain with the biasing voltage. In addition, the circuit exhibits a very low input impedance and also high output impedances which make it possible for cascading. The MOSFET capacitances which determine the transfer functions are all grounded, so physical capacitances can be used instead of MOSFET parasitic capacitances to operate the filter at very low frequencies. Moreover, proposed filter structure has low supply voltage as 1 V in order to be applicable to low voltage operations. Detailed simulation results, including noise and Monte Carlo analysis, are provided using 0.18 µm TSMC technology parameters to verify the feasibility of the filter circuit.

This paper presents Operational trans-resistance (OTRA) based electronically tunable high pass L-C based ladder filter. The proposed high pass filter is designed by following a systematic approach using leap frog simulation for ladder filters. The cut-off frequency of the proposed filter can be varied with the application of appropriate voltages to the gate of MOSFETs hence making the design electronically tunable. Therefore, it can be used for RF applications at 455kHz and 1MHz (intermediate frequencies for RF applications). Performance of the proposed circuit is verified through SPICE simulations employing a 0.5m MOSIS AGILENT CMOS realization of OTRA.

The most common damped filters (DFs) are the second-order, third-order, C-type, and double-tuned filters. Other DFs such as the first-order and band-pass filters exist, but their high operating losses considerably diminish their usage. In this paper, firstly, for the third-order damped filter with equal and unequal capacitors, the relations among their circuit parameters are derived. Secondly, the optimal design problem of the two third-order high-pass filters is formulated by regarding these expressions to minimize the filter cost taking into account both the investment and operating expenses. The total and individual harmonic distortion indices, power factor and the harmonic voltage amplification ratios which measure the filter’s resonance damping capability, are considered as constraints. A recent metaheuristic optimization technique based on the intelligent behavior of crows, known as the Crow Search Algorithm (CSA), is employed for the solution of the formulated design problem. Further, a comparative analysis of the two designs of the third-order high-pass filters and a third-order C-type filter is presented. The results reveal that all the proposed filters guarantee no electrical resonance hazards while maintaining the allowable limits for the various performance indices of the system, load, and filter. Besides, the comparative analysis validates that the C-type filter provides higher power factor, system efficiency and transmission loss improvement than the other two filters, and that the proposed filters achieve almost the same voltage and current harmonic mitigation levels. The solution of the cost minimization problem reveals that the C-type filter and the third-order high-pass filter with equal capacitors have the worst and best resonance damping capabilities respectively, under the worst case conditions. Additionally, the filters with the lowest and highest cost are found as the third-order filter with unequal capacitors and the C-type one, respectively. Besides, the CSA is compared to the genetic algorithm (GA), and particle swarm optimization (PSO) techniques and the results show the fast convergence capability and the effectiveness of the proposed algorithm in solving the problem of optimal design of third-order resonance-free passive filters in distribution networks.

We present a new design method for bandpass filters capable of adjusting center frequencies, bandwidths, and notches. For designing such filters, filter topologies employing frequency-tunable resonators in cul-de-sacs are developed. The cul-de-sac resonators are mainly responsible for constructing notches, while the resonators in main paths form passbands. For verifying the presented design method, we have designed two bandpass filters. Each filter consists of two different resonator types: microstrip-line resonators for forming passbands and substrate-integrated waveguide resonators for producing notches. The measured results of the two designed filters show that frequency-tunable notches can be placed next to the passbands without producing unwanted resonant peaks that are usually observed in bandpass-bandstop filter cascades. This indicates that the filters designed using the presented topologies can replace bandpass-bandstop filter cascades.

A filter based on characteristic functions is developed in this paper, to fit to a class of non-Gaussian dynamical systems, which state models and measurement models are all nonlinear and multi-dimensional. The new filter overcomes limitations and expands the application of this kind of filter, which is proved to just fit to one special kind of systems with multi-dimensional linear state models and one-dimensional nonlinear measurement models. Firstly, the filter using characteristic function is introduced and its limitation is analysed. Then, we design the new filter to fit to nonlinear states and multi-dimensional measurements. Thirdly, the matrix format of performance index is presented to match to the new filter gain, and the weighting function vector is given to ensure the uniform boundedness of such a performance index. Finally, the new filter gain can be obtained by minimizing this performance index, and the process of filtering design is accomplished. Simulation examples are given to illustrate the effectiveness of the proposed filter design scheme.

Novel topologies of fractional-order filters, implemented using the internal gate-source capacitance of MOS transistors, are introduced in this paper. This has been achieved using current-mirrors as active elements, resulting into resistorless realizations due to the employment of the small-signal transconductance parameter of the MOS transistor. This also offers the capability for electronic tuning of the frequency characteristics of the derived filter structures. The evaluation of the proposed technique has been performed through the design of a generalized fractional-order filter, which is also digitally programmed in such way that the four standard filter functions are offered. The behavior of the filter has been evaluated using the Cadence IC design suite and the Design Kit provided by the Austrian Micro Systems 0.35 μm CMOS process.

This paper presents a compact, wideband, waveguide bandpass filter using a hybrid combination of complementary split ring resonators (CSRRs) and Koch fractal. Three identical planar structures, printed with CSRRs and Koch fractal, have been placed in the transverse plane of a standard WR-90 waveguide at a quarter wavelength distance to form the filter. The proposed filter has been simulated using Ansoft HFSS (version 14) and the obtained frequency response has been compared with the frequency response of its lumped element equivalent circuit. The filter was also fabricated and its frequency response has been measured. The measured result shows a 3-dB fractional bandwidth of 12.66% at resonant frequency 9.95 GHz. The total length of the fabricated filter is 20.33 mm. Detailed design procedure has been presented along with necessary diagrams. A table has been provided to compare the performance of the proposed filter with those already available in the literatures. The table shows that the proposed filter is compact, has higher bandwidth and better frequency response compared to the rests.

A first order sliding mode controller with appropriate parameters sliding surface (modeled in usual time domain and realized by transfer function) is considered here for LCL grid connected three phases three wires shunt active filter (SAF). If shunt active conditioners are already well known in compensation for the main types of current disturbances in the electrical power systems, it is also admitted that they generate some undesired components caused by VSI switching frequency. In order to prevent these components from spreading to the grid side, a LCL output filter is generally proposed. In this context, a VSI connected grid via a LCL filter is largely proposed for renewable energy systems, where the component to be injected into the grid is only the fundamental. Unfortunately, when the injected components include fundamental plus harmonics and for a LCL output filter associated to linear controllers, a phase shift appears, between the identified harmonics current and the injected current. This phase shift impacts negatively the current disturbances filtration and/or compensation of the SAF. Therefore, sliding mode controller with appropriate sliding surface, in both time and frequency domains, is proposed as nonlinear control method, to overcome the phase shift effects over the entire bandwidth, for the shunt active filter. Besides, a PWM-SM-Controller, with zero order hold in input of the PWM, will allow to operate in a fixed frequency, preventing a variable switching frequency effects. The rapidity, tracking and robustness of this proposed controller, within the SAF, are validated by Matlab, Simulink, Simscap-Sim_Power_System code.

This brief presents a filter-integrated high-efficiency class-F power amplifier (PA). The hybrid cavity–microstrip filtering circuit is employed not only to realize output impedance matching and the third-harmonic manipulation but also to provide high-selectivity bandpass responses. To fulfill the requirements of high-efficiency class-F PAs, cavity resonators and microstrip feeding structures are involved, and their benefits are fully exploited. The metal cavity resonator features a high $Q$ value and, thus, low loss in the passband, resulting in high efficiency. Moreover, metal walls of cavities act as heat sink for the transistor. The microstrip feeding structures are used to improve the skirt selectivity and manipulate the third harmonic. Moreover, it features easy integration with the transistor, and thus, the transition between cavity and microstrip lines is eliminated. The hybrid filter is characterized based on filter synthesis theory. Complex impedance conversion analysis is carried out to guide the impedance transformation from 50 $\Omega$ to a complex one desired by the transistor. For demonstration, a filtering PA operating at 2.4 GHz is designed and measured. It exhibits both high-selectivity bandpass responses and good PA performance with maximum power-added efficiency of 70.9% at 40.8-dBm output power.

Use of parallel resonance to notch filter the fundamental ripple frequency on a switching regulator output offers advantages in the combined metric of size and power compared to traditional low-pass solutions. Availability of barium strontium titanate varactors with capacitance of several nanofarads now makes automatic tuning of parallel resonance alignment with the ripple fundamental a feasible alternative. A phase-lock automatic-tuning circuit is demonstrated. The effective use of this technique as the power-supply filter used to power a 16 bit ADC is shown. The suitability of the resulting filter and regulator to full surface mount encapsulation is demonstrated.

This paper presents a second-order tunable single-ended (unbalanced) bandpass filter (BPF) with continuous 0.4–3-GHz coverage and a tunable balun BPF with continuous 1.1–1.7-GHz coverage for software-defined radio transceivers with the use of band-switchable and radio frequency (RF)-micro-electromechanical systems (MEMS)-tuned resonators. The BPFs are realized with two pairs of RF switches for coarse-tuning and RF-MEMS-tunable capacitors for fine-tuning. On the one hand, for the tunable single-ended BPF, a transition between three bands is enabled using two pairs of RF switches. On the other hand, for the tunable balun BPF, a transition between two bands is enabled using one pair of RF switches. Furthermore, the three-band switchable single-ended BPF is constructed in a nested two-filter bank structure for expanding the tuning range without increasing the footprint. In addition, to complement the discrete band gaps, RF-MEMS capacitor-tuned resonators are used, and a continuous tuning range of nearly the entire ultra-high-frequency band is achieved. The filter bank is fabricated on a Duroid substrate with εr = 3.5 and h = 0.787 mm. The filter bank has an insertion loss of 3.2–6.8 dB and a 1-dB bandwidth of 65–450 MHz with a continuous tuning range of 0.4–3 GHz.

This paper presents an approach for designing 3-pole tunable microstrip bandpass filter with constant fractional bandwidth (CFBW). To achieve sharp roll-off responses, a cross-coupling scheme is ad...

A compact size and high selective bandpass filter is presented in this paper. The filter is designed to serve at 3.5 GHz with two transmission zeros at 3.35 GHz and 3.85 GHz. The filter is designed as two gap capacitor coupled to two coupled composite right–left handed transmission lines. The coupled lines were designed to demonstrate a zeroth order phase at 3.5 GHz. Also, the transmission zeros were achieved as a consequence of the electrical/magnetic couplings between the two coupled transmission lines. The employed cell, filter design equations are emphasized. The filter S-parameters were extracted based on the circuit model, full wave simulation, and experimental measurements. A good agreement between modeled, simulated, and measured results is achieved. The measured center frequency of the bandpass filter is 3.55 GHz and 100 MHz bandwidth which is suitable for WiMAX applications. Also, the filter has low measured insertion loss which does not exceed 1 dB within passband. Finally, the filter has advantages of compactness (size is 20 3 18 mm2) which is only 50% compared to conventional non-selective one-stage coupled line filter.

In this paper, a variation-aware and reliable design of a fully integrated radio frequency (RF) bandpass filter realized using a voltage differencing transconductance amplifier is presented. The filter is characterized by its high frequency operation, low power consumption, high quality factor, and it is insensitive to process, voltage, and temperature variations. Sensitivity analysis has been performed to analyze the circuit performance in the presence of parasitics. The inductor-less approach finds its application in integrated building blocks of RF front ends, thus eliminating the requirement of off-chip filters in transceivers. Centered at 2.511 GHz and operating within the 36.21 MHz 3-dB bandwidth, the filter draws 0.168 mA from a ±1 V power supply, attains a voltage gain of 72.6 dB, a quality factor of 69.34 and noise figure of ~29.6 dB. In addition, it has a dynamic range of 125.84 dB-Hz and a 1-dB compression of −1.5 dBm which translates into a figure of merit as high as 94 dB.

High-order passive filters, such as the well-known LCL filters, are normally employed in the grid-connected power conversion systems to effectively attenuate the switching frequency harmonic introduced by the modulation of power converters. Although much more compact than the conventional single-inductor L filters, such passive filters are still bulky and expensive when compared with their active counterparts, e.g., the semiconductor switches. In order to improve the system power density and reduce its cost, the magnetic integration technique has been widely adopted so that the discrete inductors of passive filters are replaced by the integrated inductor, resulting in smaller magnetic cores and, therefore, the decreased volumes of passive filters. For conventional magnetic integrated LCL filters, the converter-side inductor and the grid-side inductor are integrated together and their coupling coefficient is intentionally minimized. In this letter, this coupling coefficient is fully utilized and properly designed, and the resulting coupling effect is equivalent to inserting an additional inductor into the filter capacitor branch loop. The integrated inductor and the filter capacitor can form an integrated LLCL filter, which exhibits the advantages of both the LLCL filter and magnetic integration, e.g., enhanced harmonic attenuation, reduced filter inductances, and system volume without adding the extra trap inductor. Finally, experimental results obtained from a single-phase grid-connected voltage-source converter interfaced by the proposed integrated filter are presented to validate its effectiveness.

In this paper a control strategy for a hybrid filter has been proposed. The hybrid filter consists of an active power filter connected in series with the source and a passive filter connected in parallel with the load. The proposed strategy is based on minimizing the effective value of the voltage at the point of common coupling to ensure the transfer of the power demanded by the load. By applying the Lagrange multipliers, the value of the equivalent resistance of the set load-compensator was determined in order to achieve unity power factor. An experimental prototype was designed to verify its behavior. The compensation equipment operation was analyzed from the point of view of the system stability and from their behavior regarding disturbances of the grid voltage. For this, the hybrid filter was subjected to six electromagnetic compatibility test as it is defined in IEC 61000 standard. In all tests, the equipment maintained its functionality before, during and after the perturbation in the supply voltage.

In this paper, the design method of CLC filter for current source inverter (CSI) is discussed. This inverter is basically for photovoltaic system with small power which is also called micro-inverter. For better performance of small power inverter, flyback-type converter-side topology is determined and it operates as CSI because it has inductor inside. The CLC filter is the output filter for this CSI. Mostly, the components’ capacity and system size are regarded as key factors when evaluating small-powered systems. The CLC filter is made with an additional capacitor to a conventional CL filter. The proposed CLC filter assures the same or the better performance on current ripple reduction than the CL filter. Hence, according to this output filter benefits, the micro-inverter system can be smaller and cost down. The passive damping methods are also analysed upon the positions of resistive damping in the filter circuit. Among four different damping methods according to the resisters’ position, the opt...

In this study, a monolithic microwave integrated circuit channelized active bandpass filter using noise cancelling circuit is presented. We propose a new structure on the channelized bandpass filter. By adding output currents of three bandpass filters and using current to voltage converter, the proposed three-channel bandpass filter is achieved. In designing each bandpass filter, a recursive differential structure has been used. Also, to decrease the noise of this filter, a new noise cancelling circuit operated in a wide range from 1 to 7 GHz is investigated. By using this circuit, input impedance matching is obtained simultaneously. The chip has been implemented using GaAs 0.15 µm technology and occupies an area of 2.5 × 2.4 mm2. The post layout simulation results show a noise figure of 1.4–3.7 dB with a good input and output impedance matching less than −10 dB. The centre frequencies of channelized filter are 2, 4, and 6 GHz while the voltage gains are 18, 12, and 10 dB, respectively. The circui...

Digital filters are now key components in many modern digital systems. This paper proposed a novel evolutionary method to design structure-diversified digital filters. On the investigation of the existing evolution-based digital filter design methods, most state-of-the-art works concentrate on the evolution of appropriate transfer functions for digital filters. However, a transfer function is not equivalent to a practical digital filter that has proper structure and can be implemented by a hardware directly. Some researchers proposed a synthesis method to generate the structure of digital filter from a specified transfer function. However, this method needs an existing transfer function as the prior knowledge. Compared with existing works on the evolution of digital filters, the proposed method is novel at the following aspect: the proposed method can directly evolve the structure and parameters of digital filter without the pre-definition of the transfer function. The only prior knowledge we need is the specification of the design target, such as the frequency range of the passband and stop-band. In the experimental study, a significant characteristic is revealed that the proposed method is able to evolve structure-diversified filters with approximate frequency response. The proposed method is a prototype, and it is demonstrated to be a promising way of digital filter design.

This paper presents a low loss electrically tunable bandpass filter based on liquid crystal. By utilizing structure of transmission line and direct-connected feeding lines without coupling gaps which eliminate mismatch and radiation losses, then the proposed filter gets a low insertion loss. And the tunability of the filter is realized by utilizing electrically controlled liquid crystal (LC) material as the substrate. In order to verify the design concept, a liquid crystal tunable prototype filter is designed, fabricated and measured. Measured results agree well with the simulated results. With no bias voltage applied, the filter operates at center frequency of 11.5 GHz with fractional bandwidth of 11.3%. And with voltage tuning from 0 V to 10 V, the filter gets a tuning range of 500 MHz and the insertion losses are 2–3.1 dB, respectively.

Purpose This paper aims to describe a simple low-pass filter to suppress torque pulsation and current harmonics in permanent magnet synchronous motor (PMSM) drives. Design/methodology/approach For the control of the PMSM, a field-oriented control algorithm is always used. The proposed filter is actually a resistance, inductance, capacitance (RLC) filter. At the output of the inverter and the input of PMSM, an RLC filter is connected. This filter suppresses current harmonics through filtering phase voltage harmonics. Analysis of the filter is achieved through frequency characteristics analysis. Findings This filter can effectively filter out the harmonic of phase voltage. Both the simulation and experiment results show that the proposed filter can effectively suppress torque pulsation and current harmonics in PMSM drives. Also, the method of selecting filter parameters and the whole control system are very simple. Research limitations implications The filter increases the design cost of the system. Practical implications The harmonics and torque ripple of phase current are greatly suppressed. Also, the loss of the PMSM reduced. Originality/value The method of selecting filter parameters and the analysis of the proposed filter are proposed for the first time.

Compensation of the inactive components of network current of a rectifier with a capacitive filter or a combination thereof under connection of a parallel active filter with inductive storage based on a current inverter is considered. The active filter allows increasing the power coefficient to the maximum values, and this result may be achieved at high values of storage inductance. Modeling of the “rectifier–active filter” system is carried out by spectral methods. It is shown that correction of the switching algorithm by storage-current feedback provides a decrease by three to four times of inductance at the same values of the power factor of the “rectifier–active filter” system. A multistage active filter consisting of a current inverter and voltage inverter with current stabilization on the direct current is proposed. The total cost for the inductive elements in the multistage active filter may reduced by one order with the same values of power factors. Comparison of voltage inverters based on bridge and half-bridge schemes is carried out. Advantages of half-bridge inverters are shown.

In this paper, a systematic approach for implementing operational simulation of LC ladder filter using voltage differencing transconductance amplifier is presented. The proposed filter structure uses only grounded capacitor and possesses electronic tunability. PSPICE simulation using 180 nm CMOS technology parameter is carried out to verify the functionality of the presented approach. Experimental verification is also performed through commercially available IC LM13700/NS. Simulations and experimental results are found to be in close agreement with theoretical predictions.