Showing papers on "Low-pass filter published in 2010"

Improvement of the Electric Power Quality Using Series Active and Shunt Passive Filters

Abstract: A control algorithm for a three-phase hybrid power filter is proposed. It is constituted by a series active filter and a passive filter connected in parallel with the load. The control strategy is based on the vectorial theory dual formulation of instantaneous reactive power, so that the voltage waveform injected by the active filter is able to compensate the reactive power and the load current harmonics and to balance asymmetrical loads. The proposed algorithm also improves the behavior of the passive filter. Simulations have been carried out on the MATLAB-Simulink platform with different loads and with variation in the source impedance. This analysis allowed an experimental prototype to be developed. Experimental and simulation results are presented.

Fast Cartoon + Texture Image Filters

Abstract: Can images be decomposed into the sum of a geometric part and a textural part? In a theoretical breakthrough, [Y. Meyer, Oscillating Patterns in Image Processing and Nonlinear Evolution Equations. Providence, RI: American Mathematical Society, 2001] proposed variational models that force the geometric part into the space of functions with bounded variation, and the textural part into a space of oscillatory distributions. Meyer's models are simple minimization problems extending the famous total variation model. However, their numerical solution has proved challenging. It is the object of a literature rich in variants and numerical attempts. This paper starts with the linear model, which reduces to a low-pass/high-pass filter pair. A simple conversion of the linear filter pair into a nonlinear filter pair involving the total variation is introduced. This new-proposed nonlinear filter pair retains both the essential features of Meyer's models and the simplicity and rapidity of the linear model. It depends upon only one transparent parameter: the texture scale, measured in pixel mesh. Comparative experiments show a better and faster separation of cartoon from texture. One application is illustrated: edge detection.

Power line filter design for switched-mode power supplies

Abstract: Filtering. Graphical attentuation calculations. Conduction modes. Filter load impedance and measurement techniques. Filter source impedance. Power supply. Filter/supply interaction. Filter topologies and damping. Common mode component selection. Radiation coupling to on-board filters.

Guideline for a Simplified Differential-Mode EMI Filter Design

Abstract: The design of electromagnetic interference (EMI) input filters, needed for switched power converters to fulfill the regulatory standards, is typically associated with high development effort. This paper presents a guideline for a simplified differential-mode (DM) filter design. First, a procedure to estimate the required filter attenuation based on the total input rms current using only a few equations is given. Second, a volume optimization of the needed DM filter based on the previously calculated filter attenuation and volumetric component parameters is introduced. It is shown that a minimal volume can be found for a certain optimal number of filter stages. The considerations are exemplified for two single-phase power factor correction converters operated in continuous and discontinuous conduction modes, respectively. Finally, EMI measurements done with a 300-W power converter prototype prove the proposed filter design method.

Comparison and evaluation of the PLL techniques for the design of the grid-connected inverter systems

Abstract: The knowledge of the phase, amplitude and frequency of the utility voltage is a fundamental aspect for the design of the grid-connected inverter systems. In this paper are presented the basic features of the PLL technique. A particular attention is dedicated to the Synchronous Reference Frame-PLL scheme. About the generation of the orthogonal voltages system an evaluation of the most employed techniques is shown: Transport Delay, Inverse Park Transformation, Hilbert Transformation, Second Order Generalized Integrators (SOGI). Moreover some problems in filtering are treated. The internal filtering - due to the PD structure - and the external filtering - due to the harmonics presence in the grid voltage. In both the cases the most employed solutions are shown. For the internal filtering: Low Pass Filter, Resonant Filter, Moving Average Filter, Repetitive Controller. For the external filtering two alternative schemes are presented: the Dual SOGI-PLL and the Enanched-PLL (EPLL).

A Control Strategy for Hybrid Power Filter to Compensate Four-Wires Three-Phase Systems

Abstract: A control algorithm is proposed for a three-phase hybrid power filter constituted by a series active filter and a shunt passive filter. The control strategy is based on the dual formulation of the compensation system principles. It is applied by considering a balanced and resistive load as ideal load, so that the voltage waveform injected by the active filter is able to compensate the reactive power, to eliminate harmonics of the load current and to balance asymmetrical loads. This strategy improves the passive filter compensation characteristics without depending on the system impedance, and avoiding the series/shunt resonance problems, since the set load-filter would present resistive behavior. An experimental prototype was developed and experimental results are presented.

Variable-Frequency Grid-Sequence Detector Based on a Quasi-Ideal Low-Pass Filter Stage and a Phase-Locked Loop

Abstract: This paper proposes a filtered-sequence phase-locked loop (FSPLL) structure for detection of the positive sequence in three-phase systems. The structure includes the use of the Park transformation and moving average filters (MAF). Performance of the MAF is mathematically analyzed and represented in Bode diagrams. The analysis allows a proper selection of the window width of the optimal filter for its application in the dq transformed variables. The proposed detector structure allows fast detection of the grid voltage positive sequence (within one grid voltage cycle). The MAF eliminates completely any oscillation multiple of the frequency for which it is designed; thus, this algorithm is not affected by the presence of imbalances or harmonics in the electrical grid. Furthermore, the PLL includes a simple-frequency detector that makes frequency adaptive the frequency depending blocks. This guarantees the proper operation of the FSPLL under large frequency changes. The performance of the entire PLL-based detector is verified through simulation and experiment. It shows very good performance under several extreme grid voltage conditions.

Digital Average Current-Mode Control of PWM DC–DC Converters Without Current Sensors

Abstract: This paper introduces a digital average current-mode control technique for pulsewidth modulation dc-dc converters which only rely on voltage sampling. The proposed approach is to estimate inductor current using first-order discrete-time low-pass filter; therefore, the controller can calculate average inductor current in every switching cycle. As a novel technique of predictive average current control, it has been investigated by choosing an appropriate duty ratio to regulate valley inductor current first and then eliminating error between the estimated average inductor current and a reference current in succedent switching cycle. The algorithm is based on a two-loop control structure to achieve an accurate voltage regulation and is derived for three basic converters: buck, boost, and buck-boost. The validity of the proposed approach has been demonstrated by simulation and experimental results on a dc-dc boost converter.

Novel Voltage-Mode All-Pass Filter Based on Using DVCCs

Abstract: In this paper, a novel design for realizing a voltage-mode (VM) all-pass filter utilizing two differential voltage current conveyors (DVCCs) is proposed. Also, the suggested filter uses a canonical number of passive elements (one grounded capacitor and one resistor) without requiring any element matching condition. The proposed filter has high input and low output impedances, which make it suitable for cascading. The effects of the nonidealities of the DVCCs on the proposed design are investigated. As an application, a quadrature oscillator is designed using the proposed VM all-pass filter and an integrator. The proposed filter and oscillator circuits are simulated using the SPICE simulation program to confirm the theory.

Comparative analysis of low-pass output filter for single-phase grid-connected Photovoltaic inverter

Abstract: Nowadays, the LCL-filter type becomes an attractive grid interfacing for grid-connected Voltage Source Inverter (VSI). LCL-filter can render the current harmonics attenuation around the switching frequency by using smaller inductance than L-filter. Moreover, system using LCL-filter does not depend on the grid impedance and has a better output response while comparing with LC-filter. Firstly, an analysis and design procedure of output LCL-filter for single-phase grid-connected Photovoltaic (PV) inverter system is presented in this paper. Due to the theoretical analysis, a comparison between the designed LCL-filter with L-filter and LC-filter based single-phase grid-connected PV inverter system is carried out. The comparison results are given to validate the theoretical analysis and effectiveness of filters.

High- RF-MEMS 4-6-GHz Tunable Evanescent-Mode Cavity Filter

Abstract: This paper presents a miniature high- tunable evanescent-mode cavity filter using planar capacitive RF micro- electromechanical system (MEMS) switch networks and with a frequency coverage of 4.07-5.58 GHz. The two-pole filter, with an internal volume of 1.5 cm , results in an insertion loss of 4.91-3.18- and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, and an ulti- mate rejection of 80 dB. RF-MEMS switches with digital/analog tuning capabilities were used in the tunable networks so as to align the two poles together and result in a near-ideal frequency response. The measured of the filter is 300-500 over the tuning range, which is the best reported using RF-MEMS technology. The filter can withstand an acceleration of 55-110 g without affecting its frequency response. The topology can be extended to a multiple-pole design with the use of several RF-MEMS tuning networks inside the evanescent-mode cavity. To our knowledge, these results represent the state-of-the-art in RF-MEMS tunable filters.

A Novel Ultra-Wideband Differential Filter Based on Double-Sided Parallel-Strip Line

Abstract: In this letter, double-sided parallel-strip line (DSPSL) has been used to build a novel differential filter with ultra- wideband (UWB) response. Swap structures, based on DSPSL, are employed in the design to realize 180° phase shift. So the swap structures can realize the conversion between differential- and common-mode. Utilizing the characteristic, the input common- mode signals will be cancelled at the center of the filter, while the input differential-mode signals can propagate in the proposed filter. The proposed new differential filter was calculated in analytical method, and was simulated by the full-wave electromagnetic simulator, and was validated by the measurement. The last results show they have a good in-band and out-band performance. With fractional bandwidth of 110% centered at 3 GHz, the differential-mode signals can propagate with UWB frequency response, while the common-mode signals are suppressed below -20 dB in the whole frequency band.

High- $Q$ RF-MEMS 4–6-GHz Tunable Evanescent-Mode Cavity Filter

Abstract: This paper presents a miniature high-Q tunable evanescent-mode cavity filter using planar capacitive RF microelectromechanical system (MEMS) switch networks and with a frequency coverage of 4.07-5.58 GHz. The two-pole filter, with an internal volume of 1.5 cm3, results in an insertion loss of 4.91-3.18- and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, and an ultimate rejection of > 80 dB. RF-MEMS switches with digital/analog tuning capabilities were used in the tunable networks so as to align the two poles together and result in a near-ideal frequency response. The measured Qu of the filter is 300-500 over the tuning range, which is the best reported Q using RF-MEMS technology. The filter can withstand an acceleration of 55-110 g without affecting its frequency response. The topology can be extended to a multiple-pole design with the use of several RF-MEMS tuning networks inside the evanescent-mode cavity. To our knowledge, these results represent the state-of-the-art in RF-MEMS tunable filters.

Ultrawideband Filter Technologies

Abstract: This article presents an introduction of recently developed techniques for the design and implementation of UWB bandpass filters, including single-layer and multilayer technologies. Several techniques using single-layer technology were reported on, including the MMR technique, the hybrid microstrip/CPW technique, the optimum short-circuited-stub technique, the cascaded highpass/lowpass filter technique and techniques that use EBG-loaded structures.

A tunable universal terahertz filter using artificial dielectrics based on parallel-plate waveguides

Abstract: Using parallel-plate waveguides (PPWGs) that mimic artificial dielectrics, we demonstrate a universal filter that provides low-pass, high-pass, band-pass, and band-stop (or notch) filtering functionalities in the terahertz (THz) frequency regime. The device essentially consists of two PPWGs in a complementary geometry. The filtering functionality is achieved by positioning an appropriate amplitude mask in the path of the spatially chirped THz beam between the two waveguides. By varying the position of the mask, we experimentally and theoretically demonstrate continuous tunability of the respective 3 dB cutoff frequencies within the frequency range from about 0.3 to 0.7 THz.

High-Density EMI Filter Design for DC-Fed Motor Drives

Abstract: This paper presents strategies to reduce both differential-mode (DM) and common-mode (CM) noise using a passive filter in a dc-fed motor drive. The paper concentrates on the type of grounding and the components to optimize filter size and performance. Grounding schemes, material comparison between ferrite and nanocrystalline cores, and a new integrated filter structure are presented. The integrated structure maximizes the core window area and increases the leakage inductance by integrating both CM and DM inductances onto one core. Small-signal and large-signal experiments validate the structure, showing it to have reduced filter size and good filtering performance when compared with standard filters at both low and high frequencies.

Linear and Non-linear Contrast Enhancement Image

Abstract: This paper attempts to undertake the study two types of the contrast enhancement techniques, linear contrast techniques and non-linear contrast techniques. In linear contrast techniques applying three methods, Max-Min contrast method, Percentage contrast method and Piecewise contrast technique. Non-linear contrast techniques applying four contrast methods, Histogram equalization method, Adaptive histogram equalization method, Homomorphic Filter method and Unsharpe Mask. in the Homomorphic Filter method applying by using two type of filter, Low Pass Filter(LPF)and High Pass Filter(HPF).this applying to choose the base guesses for contrast enhancement image.

First-order voltage-mode all-pass filter employing one active element and one grounded capacitor

Abstract: A new circuit topology of first-order voltage-mode all-pass filter providing high-input and low-output impedances is described. The filter consists of only one grounded capacitor and one active element, namely VD-DIBA (Voltage Differencing-Differential Input Buffered Amplifier), with the possibility of electronically tuning the natural frequency. The filter is assembled from commercial integrated circuits, and the frequency responses measured are compared with the theoretical characteristics.

Attenuation-Predistortion Linearization of CMOS OTAs With Digital Correction of Process Variations in OTA-C Filter Applications

Abstract: An architectural attenuation-predistortion linearization scheme for a wide range of operational transconductance amplifiers (OTAs) is proposed and demonstrated with a transconductance-capacitor (Gm-C) filter. The linearization technique utilizes two matched OTAs to cancel output harmonics, creating a robust architecture. Compensation for process variations and frequency-dependent distortion based on Volterra series analysis is achieved by employing a delay equalization scheme with on-chip programmable resistors. An OTA design with the proposed broadband linearization method has third-order inter-modulation (IM3) distortion better than -74 dB up to 350 MHz with 0.2V?? input, 70 dB signal-to-noise ratio (SNR) in 1 MHz bandwidth, and 5.2 mW power consumption. The distortion-cancellation technique enables an IM3 improvement of up to 22 dB compared to a commensurate OTA without linearization. A proof-of-concept low-pass filter with the linearized OTAs has a measured IM3 < - 70 dB and 54.5 dB dynamic range over its 195 MHz bandwidth. The standalone OTAs and the filter were fabricated on a 0.13 ?m CMOS test chip with 1.2 V supply.

Improving Trajectory Tracking in Wave-Variable-Based Teleoperation

Abstract: For wave-variable-based teleoperation systems, the performance of trajectory tracking is not ensured due to a bias term introduced by the wave communication channel. This paper proposes a new method that can improve the trajectory tracking performance. The key idea is that the wave in the forward path is augmented by the user-perceived force and slave control force. The passivity of the augmented teleoperation system can be maintained by tuning the bandwidth of the low-pass filter, as demonstrated via an example. Therefore, the system stability can be always guaranteed. Both the simulation and experimental results verify the effectiveness of the scheme.

Compact quasi-elliptic microstrip lowpass filter with wide stopband

Abstract: A compact microstrip lowpass filter with quasi-elliptic response is proposed. To achieve compact design, both symmetrically loaded radial-shape patches and meandered main transmission line are adopted. To realise the quasi-elliptic response and strengthen the roll-off sharpness for the filter, a coupled capacitor between adjacent radial-shape patches is introduced in interdigital form. Furthermore, the adoption of radial-shape patches and the interdigital structure can introduce both serial and parallel resonance in the circuit. Thus, a wide stopband with 7th harmonic suppression is achieved. A demonstration filter with 3 dB cutoff frequency at 1.18 GHz has been designed, fabricated and measured. Results show that a relative stopband bandwidth of 132.3 (referred to a suppression degree of 15 dB) is obtained while achieving a high figure-of-merit of 11543.

Nonuniformly Spaced Photonic Microwave Delay-Line Filters and Applications

Abstract: A finite impulse response (FIR) filter for microwave signal processing implemented based on an optical delay-line structure with uniformly spaced taps has been extensively investigated, but the realization of such a filter with negative or complex tap coefficients to provide an arbitrary frequency response is still a challenge. In this paper, an overview of photonic microwave delay-line filters with nonuniformly spaced taps, by which an arbitrary bandpass frequency response can be achieved with all-positive tap coefficients, is presented. We show that the nonuniform time delays provide equivalent phase shifts to the tap coefficients, while the all-positive-coefficient nature simplifies greatly the filter realization. Based on the theory, a 50-tap flat-top bandpass filter with a quadratic phase response is designed and analyzed. A seven-tap nonuniformly spaced photonic microwave filter with a flat-top and chirp-free bandpass response is then demonstrated. The use of the proposed technique for advanced microwave signal processing is then discussed. The generation of a chirped microwave signal and a phase-coded microwave signal are discussed and demonstrated. The use of the proposed technique to design a FIR filter for microwave matched filtering is also discussed and experimentally demonstrated.

Efficiency of Filter Bank Multicarrier Techniques in Burst Radio Transmission

Abstract: The filter bank multicarrier (FBMC) technique has been proposed in the FP7 European research program, as an enhancement to the OFDM technique for future broadband radio systems. Besides gains in efficiency, mainly due to the absence of cyclic prefix, an important feature of FBMC is the absence of spectral leakage, which makes it particularly appealing for cognitive radio. However, in burst transmission, the filter impulse response introduces transitions which extend the length of the burst with respect to OFDM and may reduce the gains in efficiency. After a brief overview of the FBMC technique, the exploitation in burst transmission is discussed. The effect of cutting the initial and final transitions of the burst is investigated. The level of temporary spectral leakage introduced by this operation is assessed. It is shown that cuts leading to an increase in burst length of half a symbol with respect to OFDM affect the first and the last symbol only, resulting in a minor reduction in bit loading for these symbols. Application to the time division duplex access mode is considered, as well as the case of the presence of a preamble in the burst. For implementation, it is proposed to resort to a simple memory preloading technique, which has the advantage of compatibility with OFDM in dual mode systems.

Kolmogorov–Zurbenko filters

Abstract: We reviewed the properties of the Kolmogorov–Zurbenko (KZ) filter and its extensions with applications in high resolution signal and image processing. The KZ filter is defined as an iteration of a moving average (MA) filter. The impulse response function of the KZ filter is a convolution of the rectangular window being used in a MA filter. Zero derivatives at the edges of the impulse response function make it a sharply declining function, providing high frequency resolution. The KZ Fourier transform (KZFT) is derived from the KZ filter by applying it to Fourier transform. Extensions of the KZ filter and the KZFT are demonstrated with examples. Copyright © 2010 John Wiley & Sons, Inc. For further resources related to this article, please visit the WIREs website.

Systematic Design Centering of Continuous Time Oversampling Converters

Abstract: We address the practical problem of determining the loop filter component values in a single-loop continuous-time delta sigma modulator. Conventional techniques to design center the converter to achieve a desired noise transfer function are cumbersome and not numerically stable. We present a robust procedure that can be used to determine the loop filter coefficients when real opamps (with finite gain, arbitrary Digital to Analog Converter (DAC) pulse, and multiple internal poles/zeros) are used. The method can also account for excess loop delay. We illustrate our technique with second-order low-pass and fourth-order bandpass examples.

UWB Bandpass Filter Using Cascaded Miniature High-Pass and Low-Pass Filters With Multilayer Liquid Crystal Polymer Technology

Abstract: This paper presents a new ultra-wideband (UWB) bandpass filter that is formed by cascading miniature high-pass and low-pass filters implemented with multilayer liquid crystal polymer technology. The miniature high-pass and low-pass filters can be designed independently and the design procedures are described. Experiments are carried out to validate the designs. Small sizes for the fabricated high-pass filter, low-pass filter, and UWB bandpass filter are achieved, which are 4.0 mm × 4.4 mm (0.162 ?g × 0.178 ?g), 4.56 mm × 4.9 mm (0.185 ?g × 0.198 ?g) and 5.1 mm × 8.86 mm (0.207 ?g X 0.359 ?g), respectively, where ?g is the guided wavelength at 6.85 GHz. Excellent performance is obtained for all the measured filters, including low insertion losses and high selectivity. Due to its simple structure and excellent performance, the proposed UWB bandpass filter is favorable for practical UWB communication and radar systems.

Extraction of Unloaded Q and Coupling Matrix From Measurements on Filters With Large Losses

Abstract: In this letter, a simple solution is described for obtaining an accurate evaluation of the coupling matrix and the unloaded Q from the measured scattering parameters of a microwave lossy filter (assuming all the resonators with the same unloaded Q). The Cauchy method is applied in a predistorted frequency domain, where the measured (lossy) parameters refer to a lossless device. In this way, it becomes possible to synthesize a prototype low-pass network using well established techniques, once the topology of the filters has been assigned. With respect to the previous methods available in the literature, the one here proposed allows very accurate results even with filters exhibiting large insertion losses; moreover the computing time is extremely short allowing the use of the method in real time computer-aided tuning procedures for microwave filters. An example of application of the proposed method is reported in the letter for illustrative and validating purposes.

A Study of a Hybrid Filter

Abstract: This paper presents results of a comparative study of two possible hybrid filter topologies, comprised of a passive and active stage, which can be implemented in any general dc supply distribution system. The main filter task is to mitigate current dynamics in the dc distribution system in order to prolong the operational life of delicate dc supplies, i.e., fuel cells, and to reduce the electromagnetic interferences between sensitive electronic circuits connected to the distribution net. The active stage is incorporated into the passive part in order to: 1) improve its insufficient attenuation in the low-frequency range and 2) source or sink any surplus energy flow between the dc source and load in case of low-frequency current dynamics. Two active stage topologies are proposed, analyzed, and evaluated in detail: 1) an active filter based on a single-leg inverter and 2) an active filter based on an electronic smoothing inductor. A special focus is on achieving attenuation at different voltage levels of the auxiliary supply and at different coupling inductances. The impact of the current ripple generated by the switching mode of the active filter operation is discussed as well. The active filter based on the single-leg inverter offers superior attenuation, particularly in the low-frequency range where attenuation is improved nearly for 15 dB compared to the passive filter.

LCL-filter design for grid-connected PCS using total harmonic distortion and ripple attenuation factor

Abstract: This paper deals with a design method of LCL filter for grid-connected three-phase PWM voltage source inverters (VSI). By analyzing the total harmonic distortion of the current (THD i ) in the inverter-side inductor and the ripple attenuation factor of the current (RAF) injected to the grid through the LCL network, the parameter of LCL can be clearly designed. The described LCL filter design method is verified by showing a good agreement between the target current THD and the actual one through simulation and experiment.