Showing papers on "Electronic filter published in 2000"

Series active power filter compensates current harmonics and voltage unbalance simultaneously

Abstract: An active power filter connected in series to the power distribution system is presented and analysed. The series active power filter is implemented with a three-phase PWM voltage-source inverter and operates with a resonant LC passive filter connected in parallel to the power lines. The proposed scheme is able to simultaneously compensate current harmonics, the fundamental negative and zero sequence voltage components generated by the voltage source unbalance, and also eliminates the zero sequence current harmonic components that circulate through the neutral conductor. The active power filter is discussed in terms of the principles of operation under steady-state and transient conditions. The design and implementation of the power and control circuits are reported. Key predicted results are verified experimentally on a 5 kVA prototype model.

Impedance blocking filter circuit

Abstract: An impedance blocking filter circuit is provided for use in telecommunication systems for interconnecting between incoming telephone lines and customer's terminal equipment so as to unconditionally block impedances above 20 KHz due to the customer's terminal equipment from an ADSL network unit and/or home networking interface unit. The filter circuit includes first, second, and third inductors connected in series between a first input terminal and a first common point. A first resistor has its one end connected also to the first common point and its other end connected to a first output terminal. Fourth, fifth and sixth inductors are connected in series between a second input terminal and a second common point. A second resistor has its one end also connected to the second common point and its other end connected to a second output terminal. A capacitor has its ends connected across the first and second common points. In other aspects, the filter circuit also includes switching means for eliminating shunt additive capacitance, correction circuit means reducing significantly return loss, and switch suppression circuit means for eliminating transients.

Programmable RC filter

Abstract: A programmable resistive-capacitive filter circuit enabling on-chip digital control of the frequency response includes a switched resistive type voltage divider network where one of the resistors forms an element of an RC filter and wherein the voltage divider additionally provides a DC bias on an output terminal. One preferred embodiment of the invention is directed to a programmable bandpass filter including MOSFET type semiconductor devices which are utilized as switched resistive elements of the filter.

Surface acoustic wave filter

Abstract: PROBLEM TO BE SOLVED: To provide a SAW (surface acoustic wave) filter having several kinds of applications regardless of one kind of a SAW filter SOLUTION: This SAW filter 100 has SAW filter elements 10 and 20 internally Input-output terminals 12 and 24 of the elements 10 and 20, output-input terminals 16 and 28 are connected electrically to 1st, 2nd, 3rd and 4th filter terminals 40, 42, 44 and 46 respectively, input-output terminals 14 and 22 are both connected electrically to a 1st common filter terminal 48, and output-input terminals 18 and 26 are both connected electrically to a 2nd common filter terminal 50 respectively The filter 100 can optionally decide an input side and an output side, and also, whichever is selected as an input side, it can output a signal of a frequency band that passes through the 1st and 2nd SAW filter elements

Electronic tunable filters with dielectric varactors

Abstract: A radio frequency electronic filter includes an input, an output, and first and second resonators coupled to the input and the output, with the first resonator including a first voltage tunable dielectric varactor and the second resonator including a second voltage tunable dielectric varactor. The resonators can include a lumped element resonator, a ceramic resonator, or a microstrip resonator. Additional voltage tunable dielectric varactors can be connected between the input and the first resonator and between the second resonator and the output. Voltage tunable dielectric varactors can also be connected between the first and second resonators.

Active and hybrid filters for power conditioning

Abstract: This paper describes principles, system configurations, control strategies and implementations, and filtering characteristics of active and hybrid filters for power conditioning. Their practical applications are expanding not only into office-buildings, hospitals, water supply utilities and rolling stock but also into electric power utilities. For example, a hybrid filter consisting of a 5 MVA series active filter and a 25 MVA shunt passive filter has been installed at the Yamanashi test line for high-speed magnet-levitation trains. The series active filter makes a great contribution to damping of harmonic resonance between the supply inductor and the shunt passive filter.

Active LC filters on silicon

Abstract: The paper deals with research toward the design of active LC filters on silicon. Subjects such as negative resistors, Q enhancement, dynamic range, filter synthesis, and automatic tuning are discussed.

New hybrid parallel active filter configuration minimising active filter size

Abstract: The authors propose a new topology for a hybrid parallel active filter that can further reduce the active filter (inverter) power rating. The basic idea is to install the active filter in parallel with the passive filter inductor. One advantage of this is that the passive filter can operate by itself if the inverter is in the high-impedance mode. This means that the passive filter can operate without the aid of the active filter. Another advantage is that, because the significant portion of fundamental and harmonic components flows through the passive filter, the current loading to the inverter is reduced greatly. This contributes to reducing the cost of the expensive inverter, and, hence, this makes the application of a hybrid active power filter more feasible. Through computer simulations and experiments, the authors have verified the effectiveness of the proposed topology.

Hybrid filter control system with adaptive filters for selective elimination of harmonics and interharmonics

Abstract: The interharmonics produced by some classes of nonlinear loads limit the effectiveness of classical passive filter compensation and active compensation must be considered. In high-voltage, high-power applications hybrid filter systems are technically justified and cost-effective solutions. Hybrid filter control strategies successfully employed in the compensation of high-power rectifier loads based on the detection of the total current distortion are less effective in the compensation of interharmonics. A frequency selective control system for a voltage controlled active filter connected to the power system through a multistage passive filter is described. A bank of second-order IIR digital filters with interharmonic tracking ability is employed for high-resolution spectral estimation and control. This approach is verified by simulation. It is shown for example that the active filter can compensate for supply interharmonics produced by a cycloconverter load. Different control strategies based on the selective control system are investigated and compared with an earlier strategy based on the detection of the total current distortion. By using individual detection and compensation of critical harmonics and interharmonics, hybrid power filters can be optimised to satisfy the distortion limits with the lowest active filter rating and switching frequency.

Reactive power compensation and load balancing for unbalanced three-phase four-wire system by a combined system of an SVC and a series active filter

Abstract: A combined reactive power compensation method of a static VAr compensator (SVC) and a series active filter is described for unbalanced three-phase four-wire distribution feeders with harmonic distortion. The SVC which consists of /spl Delta/-connected thyristor-controlled reactors, Y-connected thyristor-controlled reactors and passive filters, acts as a classic reactive power compensator for load balancing and power factor correction. The small rating active filter is used to improve the filtering characteristics of the passive filter in the SVC and suppress possible resonance between the system impedance and the passive filter. Simulation results performed by the Electromagnetic Transients Program show that the proposed reactive power compensation configurations can effectively balance currents, correct power factor and eliminate harmonic currents.

Design and properties of polynomial-based fractional delay filters

Abstract: Design and properties of polynomial-based FIR filters with adjustable fractional delay are studied. Given the passband region, the filter parameters are optimized to minimize in the passband the worst-case phase delay deviation from the desired value (the maximum deviation for fractional delays between zero and unity) subject to a given worst-case amplitude deviation from unity in the passband. It is shown that the filter with fractional delay equal to one-half determines the lower limit for the achievable amplitude distortion. Because the filters under consideration are polynomial-based, they can be efficiently implemented using the modified Farrow structure introduced by the authors. The main benefit of the proposed synthesis scheme lies in the fact that it results in the structure where the linear-phase branch filters of the modified Farrow structure are fixed and only one parameter controls the fractional delay.

High frequency module

Abstract: PROBLEM TO BE SOLVED: To achieve the miniaturization of a module as a whole, the reduction of loss, and high isolation by arranging a means for miniaturizing a switch circuit to change over transmission and reception, for saving current consumption, and for adjusting matching between an antenna terminal and a switch, and also raising resistance against the high-voltage serge of the switch. SOLUTION: On the front surface of or at the inside of a multilayer board A obtained by alternately laminating dielectric layers and conductor layers, a high frequency module includes: a branching filter circuit which is connected to an antenna terminal so as to divide a plurality of transmission/reception systems different in pass bands into individual transmission/reception systems; a switch circuit which is connected to the branching filter circuit so as to change-over the respective transmission/reception systems into transmission systems and reception systems; a power amplifier circuit which is connected to the switch circuit so as to amplify a transmission signal in the pass band of each transmission system; and a matching circuit for the power amplifier circuit. The power amplifier circuit and the switch circuit are mounted on the front surface of the multilayer board A as high-frequency semiconductor integrated circuit elements. COPYRIGHT: (C)2005,JPO&NCIPI

New configuration for realizing universal voltage-mode filter using two current feedback amplifiers

Abstract: A new universal biquadratic filter configuration using two current-feedback amplifiers (CFAs) is presented. The circuit has three inputs and one low-impedance output and can realize all the standard filter functions, that is, highpass, bandpass, lowpass, notch, and allpass filters, without changing the passive elements. The proposed circuit has no requirements for component matching conditions and uses only four passive components. The center frequency and bandwidth can be orthogonally controllable. Also, the active and passive sensitivities are low.

Direct finite-element analysis of the frequency response of a Y-Z lithium niobate SAW filter

Abstract: A direct finite-element model is developed for the full-scale analysis of the electromechanical phenomena involved in surface acoustic wave (SAW) devices. The equations of wave propagation in piezoelectric materials are discretized using the Galerkin method, in which an implicit algorithm of the Newmark family with unconditional stability is implemented. The Rayleigh damping coefficients are included in the elements near the boundary to reduce the influence of the reflection of waves. The performance of the model is demonstrated by the analysis of the frequency response of a Y-Z lithium niobate filter with two uniform ports, with emphasis on the influence of the number of electrodes. The frequency response of the filter is obtained through the Fourier transform of the impulse response, which is solved directly from the finite-element simulation. It shows that the finite-element results are in good agreement with the characteristic frequency response of the filter predicted by the simple phase-matching argument. The ability of the method to evaluate the influence of the bulk waves at the high-frequency end of the filter passband and the influence of the number of electrodes on insertion loss is noteworthy. We conclude that the direct finite-element analysis of SAW devices can be used as an effective tool for the design of high-performance SAW devices. Some practical computational challenges of finite-element modeling of SAW devices are discussed.

Lead set filter for a patient monitor

Abstract: A shielded conductor path comprising: a first signal conductor having an input end for acquiring a physiological signal and an output end for coupling the physiological signal to a physiological signal input of a patient monitor, and a second signal conductor positioned with respect the first signal conductor for acting as a shield therefore An inductance connected in series between an output end of the second signal conductor and the reference signal input of the patient monitor forms a filter circuit which attenuates the level of an interference signal in the second signal conductor In one preferred embodiment of the invention, the inductance is part of an RLC filter circuit contained in a housing which is selectively insertable between an EKG lead set and the EKG signal input of a patient monitor The selectively insertable filter permits the use of standard EKG lead sets in the presence of RF electrosurgery procedures, without risk of burning the patient at the site of the EKG electrodes

Noise-cut filter

Abstract: A spiral LC composite member is formed by splicing together a desired number of rectangular dielectric chips between two spiral coils with rectangular cross sections. A noise-cut filter circuit is formed by laminating and connecting a desired number of spiral LC composite members. A desired number of noise-cut filter circuits are layered through insulation sheets, and are enclosed by a magnetic body so that a magnetic circuit can be formed at the core and the outer circumference of the multi-layered body. This constructs a filter circuit serving as a reactor and a capacitor.

Digital comb filter for decoding composite video signals

Abstract: A digital comb filter for decoding composite video signals into a luminance and a chrominance component A Fast Fourier Transform (FFT) circuit or a band split filter circuit is used to determine important characteristics of an input video signal without demodulating the video signal The circuits produce a signature signal by which each of the video lines can be correlated Signature signals on various surrounding video lines that are of opposite subcarrier phase with the current line are compared to determine similarity and appropriate weighting coefficients for the surrounding lines If none of the surrounding lines are similar, the comb reverts to a band split filter to form chrominance A noise measure circuit determines an error signal input used to adjust the weighting coefficients as the noise level increases or decreases Multiplexer combines high pass and low pass taps of a band split filter into a single data stream Line delays, together with field delay memories, provide the interlaced line above and below the current line for the comb filter Interframe motion detector gives priority to the frame comb signal when no motion is detected between the current line and the frame delayed signal in the same vertical position as the current line Dynamic threshold modification is used to suppress unwarranted comb filter failures in the presence of luma edges

Two-branch microwave channelized active bandpass filters

Abstract: The realization of small highly selective microwave filters has emerged as a prominent issue in the design of miniaturized high-frequency systems. In this paper, a new way to implement channelized active bandpass filters is presented that deals with the impasse. The concept involves a two-branch configuration, which yields filter circuits that are more compact and offer lower noise figures than earlier three-branch versions, while still retaining all the advantages of channelized feedforward operation. The practicability of the technique is demonstrated with two 10 GHz bandpass filters of different design, whose assessed performance characteristics include signal distortion and noise properties.

First-order allpass sections-based current-mode universal filter using ICCIIs

Abstract: An inverting type current conveyor (ICCII) is presented and its usefulness in active filter synthesis illustrated by presenting a new current-mode universal filter using this element. The universal filter configuration based on the implementation of first-order allpass sections employs the absolute minimum number of passive and active components and hence leads to a filter circuit with very simple implementation.

A 10.7-MHz CMOS SC radio IF filter using orthogonal hardware modulation

Abstract: FM radio receivers require an IF filter for channel selection, customarily set at an IF center frequency of 10.7 MHz. Up until now, the limitations of integrated radio selectivity filters in terms of power dissipation, dynamic range, and cost are such that it is still required to use an external ceramic 10.7-MHz bandpass filter. This paper demonstrates a CMOS switched-capacitor IF filter that can be integrated with most of the rest of the FM receiver, eliminating external components and printed circuit board area. This is made possible through a combination of two techniques: orthogonal hardware modulation, and delta-charge redistribution. It exhibits a tightly controlled center frequency with a Q of 55 and also contains a programmable gain. The filter occupies an area of 0.7 mm/sup 2/ in a 0.6 /spl mu/m CMOS process with poly-poly capacitors. The new filter requires only 16 mW of power, and this is offset by elimination of the power needed in current designs to drive off-chip filters.

Highly selective HTS band pass filter with multiple resonator cross-couplings

Abstract: A highly selective High Temperature Superconducting (HTS) band pass filter with multiple resonator cross-couplings is presented. High Quality (Q) factor HTS filter elements enable highly selective low loss filters to be manufactured. In order to increase the selectivity of a planar filter while maintaining a small footprint, multiple cross-couplings are added. The cross-couplings are added to provide either low side rejection enhancement, high side enhancement or enhancements to both sides of the filter depending on the specific application. This paper will discuss the design and development of a 10-Pole highly selective band pass filter with multiple cross-couplings.

Surface acoustic wave (saw) filter of the reactance filter type exhibiting improved stop band suppression and method for optimizing the stop band suppression

Abstract: The invention relates to a surface acoustic wave (SAW) filter of the reactance filter type comprising at least two SAW resonators (R2, R3) in two parallel branches and comprising a SAW resonator (R1) in a serial branch. According to the invention, an electric connection, said connection being produced on the substrate, of the ground sides (12-6, 12-7) of both SAW resonators (R2, R3) in the parallel branches is provided before the connection (12-5) to the housing in order to be able to shift the pole location associated with the parallel branch to a lower frequency.

System and method for varying low audio frequencies inversely with audio signal level

Abstract: The present invention relates to an auto loudness circuit for performing loudness compensation automatically depending on the signal level. When the signal level decreases, loudness compensation is slowly introduced and as the signal level increases, loudness compensation is quickly removed. To do so, the auto loudness circuit utilizes a filter circuit with the characteristic of a first order bass boost. The filter circuit maintains a corner frequency which is proportional to the inverse of audio level in order to mimic the Fletcher-Munson curves. Because the circuit employs a capacitance-multiplier with a first order resistance capacitance filter, the bass boost is inversely proportional to the signal level. Thus, bass boost is achieved automatically as the program content changes so that the listener is unaware of significant changes in program material as signal levels change either through increase or decrease in volume, crescendo or new material.

Filter banks implemented with integrated thin film resonators

Abstract: Filter banks composed of five or more bandpass filters fabricated on a single die have been demonstrated and are under continuing development. Such filters will find applications in multi-channel radios, spectrum analyzers, and in other frequency control applications. Fabrication of ladder bandpass filters requires that resonators be built at two or more frequencies for each filter. In the simplest form of the ladder filter, at least one frequency is needed for the series resonator and a lower frequency for the shunt resonator. This paper reports on a technique to fabricate multiple frequency resonators and experimental results for a simple five channel filter bank.

Variable rate dpsk system architecture

Abstract: A communication system and more particularly to a variable rate differential phase shift keying (DPSK) communication system with minimal hardware that does not have power or performance penalties associated with known DPSK modulation systems is disclosed. The DPSK modulation system in accordance with the present invention includes a transmitter, which includes a carrier signal source, a phase modulator and a DPSK encoder for modulating a carrier signal. The modulated carrier signals may be amplified, for example, in optical communication systems by a rare earth element doped fiber amplifier. The signals are continuously transmitted to a multi-rate receiver through a communication channel, for example, free space. The multi-rate receiver includes a single demodulator, for example, a single optical interferometer, used for multiple integer sub-harmonic data rates which demodulates the modulated signal. The demodulated signals are detected, for example, in optical communication systems by an arrangement of photodiodes, and the detected signals are applied to, for example, a clock and data recovery circuit that is tuned as a function of data rate, for example, by way of a switched filter circuit. The switched filter circuit may include a plurality of low-pass filters that are selected as a function of the data rate. Since the carrier signal is continuously transmitted, a phase reference is available to demodulate all received power and the peak transmitted power is approximately equal to the average transmitted power even at data rates corresponding to bit times that are large compared to the differential time delay of the demodulator.

Printer system with encoder filtering arrangement and method for high frequency error reduction

Abstract: A printhead firing control system for an inkjet printer includes a printhead mounted for movement across a paper path and an encoder for producing a digital output signal indicative of movement of the printhead. A filter circuit is connected to receive the digital output signal for filtering the digital output signal to remove frequency variations which meet at least one predetermined parameter, thereby providing a filtered digital signal. A fire-pulse generation circuit receives the filtered digital signal from the filter circuit and produces printhead heater resistor drive pulses based at least in part upon the filtered digital signal. This arrangement provides for improved printing accuracy by eliminating frequency changes in the digital encoder signal which may erroneously be caused by mechanical vibrations or other noise within the printer. An improved digitally controlled oscillator construction is also described.

New inverter output filter topology for PWM motor drives

Abstract: This paper presents a new inverter output filter topology for PWM motor drives. It is shown that the proposed filter effectively reduces high frequency harmonics which cause serious damage to the motor bearings and insulation. The proposed filter is comprised of a conventional RLC network cascaded with an LC trap filter. The LC trap, tuned to the inverter switching frequency is very effective in reducing the switching harmonics. By using this new topology the need for high damping resistance and low RLC cut-off frequency is eliminated. This reduces the phase shift in the current regulation loop and increases the filter efficiency. Experimental verification of the filter topology is provided with a 480 V inverter and a 25 HP permanent magnet synchronous motor. Space-vector predictive current regulation is implemented as an inner-loop current regulator for the outer-loop speed control using a digital signal processor. The effectiveness of the filter at different motor speeds is presented.

Surface acoustic wave filter

Abstract: The present invention disclosed a SAW filter in which unnecessary space on a chip (11) can be reduced in comparison with the prior art, and in which a smaller chip can be realized. Because oblique step shaped reflection surfaces (14, 15, 54, 55, 64, 65) are provided in- order to reflect the SAW, a smaller SAW filter than that used in the prior art can be realized (Figure 1).

Surface Acoustic Wave Filter Using Floating Electrode Slanted Finger Unidirectional Transducers

Abstract: This paper describes a wide-band surface acoustic wave (SAW) filter designed to achieve large stop-band attenuation. The SAW filters using slanted finger interdigital transducers are suitable for mid- or wide-band filters. To achieve a stop-band attenuation of more than 80 dB, two SAW filters using slanted finger unidirectional transducers (SFUDTs) were cascaded. Since these SFUDT filters have center-to-center distances that differ by one-fourth of the acoustic wavelength at the center frequency, the triple transit echo was effectively compensated. A cascaded-pair SFUDT SAW filter with a fractional bandwidth of 15 percent was designed and fabricated on a 128°Y-X LiNbO3 substrate. An insertion loss of 14 dB, amplitude ripples of 0.5 dB and stop-band attenuation of 80 dB or more were achieved.

Intelligent controller for communicable plastics casing circuit breaker

Abstract: The intelligent controller of communicable plastic shell circuit-breaker includes switching power supply circuit, voltage filter circuit, amplifying circuit and current filter circuit, amplifying circuit, comparator detection circuit, multicircuit switch circuit, absolute value amplifying circuit, phase-locked loop frequency tracking circuit, power factor detection circuit, leakage protecting circuit, tripping control circuit, chip microprocessor circuit and display keyboard circuit. It can make independent real-time detection of three-phase four-wire circuit parameters, possesses alarm and protection functions, can implement permanent memory and inquiry of failure, and can transfer the field state, set parameters and failure logging into higher level computer by means of communication interface so as to form multi-stage monitoring system.