Showing papers on "Electronic filter published in 2003"

Passive filters-potentialities and limitations

Abstract: New topologies for harmonic mitigation and active filters have come a long way, and these address the line-harmonic control at the source. These mitigate some of the disadvantages of passive filters, however, for nonlinear loads above 1 MW the passive filters are an economical choice. This paper discusses two types of filters: band pass filters and damped filters, which are commonly applied. The operation of these filters is described with respect to the design and system limitations. The operating constraints are then superimposed. The development of this approach shows that there are design limitations and large system changes or modifications can result in higher distortion or even damage to filters in extreme cases. The constraints and limitations that a designer faces in implementing an effective filter design with modern tools of harmonic analysis, measurements, and system analysis are discussed. The paper shows that in most distribution systems it is practical and economical to implement passive filter designs, provided the required safeguards are considered.

Improving passive filter compensation performance with active techniques

Abstract: This paper presents the performance analysis of a hybrid filter composed of passive and active filters connected in series. The analysis is done by evaluating the influence of passive filter parameters variations and the effects that different active power filter's gain have in the compensation performance of the hybrid scheme. The compensation performance is quantified by evaluating the attenuation factor in a power distribution system energizing high-power nonlinear loads compensated with passive filters and then improved with the connection of a series active power filter. Finally, compensation characteristics of the hybrid topology are tested on a 10-kVA experimental setup.

Component working with acoustic waves and having a matching network

Abstract: A component working with acoustic bulk waves is provided that has a multi-layer substrate, where the multi-layer substrate comprises an integrated matching network and further circuit elements for adapting the electrical filter properties and can serve as carrier substrate for thin-film resonators.

Comparisons in circuit configuration and filtering performance between hybrid and pure shunt active filters

Abstract: This paper deals with a hybrid shunt active filter for harmonic compensation of a three-phase diode rectifier in a 480-V adjustable-speed drive system. The hybrid filter is formed by a three-phase single-tuned current LC filter for the 7-th harmonic frequency and a small-rated three-phase voltage-source PWM inverter. Computer simulation is carried out to compare the hybrid filter with a pure shunt active filter in terms of circuit configuration and filtering performance. The simulation results indicate effectiveness and viability of the hybrid filter. In addition, theoretical analysis confirms the validity of the simulation results.

Piezoelectric resonant filter and duplexer

Abstract: A piezoelectric resonant filter includes a group of series resonators and a group of parallel resonators for forming a ladder-type filter circuit. Each of the resonators has a piezoelectric thin film having piezoelectric characteristic, and lower and upper electrodes disposed on opposite surfaces of the piezoelectric thin film for applying an excitation voltage to the piezoelectric thin film. The group of the parallel resonators exhibits a low frequency side attenuation extremum in the filter whereas the group of the series resonators exhibits a high frequency side attenuation extremum in the filter. At least one of the group of the series resonators and the group of the parallel resonators has a temperature compensating layer for bringing the temperature coefficient of the resonant frequency close to zero.

Passive filter design using genetic algorithms

Abstract: The objective of this paper is to propose a new approach for designing a passive LC filter of the full-bridge rectifier by using genetic algorithms (GAs). The performance of the cost-effective passive LC filter for a constant load depends on the appropriate inductor and capacitor selection. Several design methods are reviewed and a novel design methodology using GAs is proposed in this paper. By using the proposed GA program, designer can quickly find appropriate parameter values to meet the desired circuit performance. Experimental results show that an appropriate combination of the inductor and capacitor selected by the proposed GA program can meet the desired power quality requirement. Different cases of design examples are shown in this paper to verify the performance of the proposed design methodology.

Bulk acoustic wave resonator and circuit comprising same

Abstract: The invention relates to a resonator operating with bulk acoustic waves (BAW resonator, BAW=Bulk Acoustic Wave) and band-pass filters constructed of such resonators. To increase the edge steepness of the transmission band of a BAW band-pass filter, the invention proposes reducing the effective coupling of a BAW resonator by using the connection in parallel of a BAW resonator and a capacitor instead of only one resonator. In addition, to increase the edge steepness of the transmission band, the use of a connection of coupled BAW resonators in the serial branch of a filter circuit with another resonator or resonator stack in the parallel branch of the filter circuit is proposed, the additional resonator or resonator stack being connected to the center electrode of the resonator stack specified initially.

Mechanically switchable photonic crystal filter with either all-pass transmission or flat-top reflection characteristics.

Abstract: We theoretically introduce a new type of optical all-pass filter based on guided resonance in coupled photonic crystal slabs. The filter exhibits near-complete transmission for both on- and off-resonant frequencies and yet generates large resonant group delay. We further show that such a filter can be mechanically switched into a flat-top band rejection filter.

A novel open-loop control method for a current-source active power filter

Abstract: This paper presents a new control system for a current-source active power filter. The harmonic current compensation is realized using only a feedforward control of the load currents. The LC filter resonance of the converter is damped in an open-loop manner using the dynamic equations of the supply filter. The benefits of the proposed control system are that it is simple and straightforward, the number of measurements and sensors can be minimized, and also that the LC filter size can be optimized according to proper harmonic distortion level of the supply currents without care about the stability issues of the closed-loop system. This usually leads to reduction of the filter size. Also, the changes in fundamental current components of the active filter can be effectively realized when the active power filter can also be used as a fast reactive power compensator. The control system also includes the calculation delay compensation of the digital control system. The control system is realized using a single-chip Motorola MPC555 microcontroller. The tests with the prototype show effective current harmonic compensating performance of the nonlinear loads.

Filter networks for long cable drives and their influence on motor voltage distribution and common-mode currents

Abstract: Filter networks for long cable drives have been studied in the last decade to solve the over-voltage problem at the motor terminals. However, little research has been dedicated to analyze their influence on the voltage distribution in the motor stator winding and on the circulation of the common-mode currents. In this paper, the project of dv/dt filters through simulation and analysis from previous works is extended including the motor voltage distribution and common-mode current analysis. Simulation and experimental results are presented demonstrating the usefulness of the filter networks on the motor over-voltage mitigation. Three filter topologies is discussed and compared here: RLC filter at the motor terminals, RLC Filter at the inverter output and reactor filter, which is extensively used in the industry. Simulation and experimental results demonstrates that the RLC Filter at the inverter output is the most interesting solution among the main types of passive filter networks.

A novel digitally tunable microwave-photonic notch filter using differential group-delay module

Abstract: We demonstrate a digitally tunable microwave-photonic notch filter based on a differential group-delay module which produces a relative delay between two orthogonal polarizations. A maximum rejection level greater than 60 dB is obtained. The tunability of the filter is achieved through real-time electronic control of the relative delay time.

Adaptive speech filter

Abstract: An adaptive speech filter ( 10 ) for conditioning speech signals to increase signal to noise ratio in a relatively noisy environment. The adaptive speech filter ( 10 ) has a preamp circuit ( 12 ), a high pass adaptive filter circuit ( 14 ), an output buffer circuit ( 16 ), a peak detector amplifier/filter circuit ( 18 ), a peak detector circuit ( 20 ) and a voltage regulator circuit ( 22 ), embodied in an application specific integrated circuit ( 24 ). The adaptive speech filter ( 10 ) is intended for input to telephones, radios, and the like.

A robust multilevel hybrid compensation system for 25 kV electrified railway applications

Abstract: On many electrified railway systems with single-phase 25 kV industrial frequency supply, the power quality can be particularly poor when conventional SCR-based locomotives are operating, and this constrains the amount of power that can be delivered to the locomotives. This paper presents a shunt compensation system consisting of alternatively a cascaded or a reduced topology multilevel active power filter, and a low rating damping filter. The active filter is controlled by a novel hysteresis current regulation strategy, and both mitigate low order voltage harmonic distortion along the feeder and provides RMS voltage support. The passive filter damps harmonic resonances that are typical in such 25 kV traction systems. The results show that the filter system can significantly increase traction system power transfer capacity with only a relatively small capital investment, allowing older thyristor based locomotives and increased traffic levels to be supported without necessarily requiring a complete system upgrade. Simulation and experimental results are included showing the performance of the filter for both steady state and transient conditions.

Filters with active tuning for power applications

Abstract: Filters for switched-mode power converters have traditionally relied on low-pass networks-with corner frequencies well below the ripple fundamental-to attenuate switching harmonics over a range of frequencies. The filters explored in this report provide extra attenuation at discrete frequencies, easing the filtering requirement of accompanying low-pass networks. When a converter's switching frequency is tuned to a filter resonance using a novel phase-lock control scheme, a resonant filter can match the ripple-attenuation performance of a low-pass network for less volume, weight, and expense. The design and application of resonant filters and active-tuning control are discussed, and experimental results from the input filter and power stage of a prototype DC-DC converter are presented.

Moisture detection system and method of use thereof

Abstract: A moisture detection system includes an electrical conductor disposed on a surface of a substrate. The electrical conductor has a resonant frequency that varies as a function of an amount of moisture present adjacent the electrical conductor. An oscillator outputs an oscillator signal at a predetermined amplitude and a predetermined frequency. A resonator circuit is coupled to the electrical conductor and is responsive to the oscillator signal and the resonant frequency of the electrical conductor for outputting a resonator signal having an amplitude related to the resonant frequency of the electrical conductor. A filter circuit rectifies and filters the resonator signal and provides it to an analog-to-digital converter which outputs a digital signal related to the rectified and filtered resonator signal. A controller is responsive to the digital signal for causing a system associated with the substrate to operate in accordance with the digital signal.

Continuous time fourth order delta sigma analog-to-digital converter

Abstract: A fourth order delta sigma analog-to-digital converter is presented, comprising a passive delta sigma modulator including a passive filter, a quantizer, and a digital-to-analog converter in a first feedback loop, and an active filter having a large gain factor in a second feedback loop around the passive delta-sigma modulator

Design and evaluation of a hybrid passive/active ripple filter with voltage injection

Abstract: Active ripple filters can substantially attenuate power converter ripple, allowing considerable reduction in passive filter component size. Investigated here is a hybrid passive/active filter topology that achieves ripple reduction by injecting a compensating voltage ripple across a series filter element. Both ripple feedforward and feedback are employed. The design of sensor, amplifier, and injector circuitry for this application is explored. The experimental results demonstrate the feasibility and high performance of the new approach, and illustrate its potential benefits. It is demonstrated that the proposed approach is most effective in cases where it is desirable to minimize the amount of capacitance in the filter.

Superconducting microstrip filters using compact resonators with double-spiral inductors and interdigital capacitors

Abstract: Novel resonators composed of double-spiral inductors and interdigital capacitors are developed, which not only are compact in size but also have no harmonics up to three times of the fundamental frequency. The center frequency is insensitive to the thickness of the substrate. A miniature seven-pole narrow-band HTS bandpass microstrip filter has been designed, fabricated and tested for an astronomy observation application, which requires a center frequency at 610 MHz and 0.82% fractional bandwidth. The computed and measured results are found in excellent agreement.

Design and evaluation of a hybrid passive/active ripple filter with voltage injection

Abstract: Active ripple filters can substantially attenuate power converter ripple, allowing considerable reduction in passive filter component size. Investigated here is a hybrid passive/active filter topology that achieves ripple reduction by injecting a compensating voltage ripple across a series filter element. Both ripple feedforward and feedback are employed. The design of sensor, amplifier, and injector circuitry for this application is explored. The experimental results demonstrate the feasibility and high performance of the new approach, and illustrate its potential benefits. It is demonstrated that the proposed approach is most effective in cases where it is desirable to minimize the amount of capacitance in the filter.

Interactive multiobjective passive filter planning with fuzzy parameters in distribution systems using genetic algorithms

Abstract: The power quality in distribution systems becomes deteriorated due to an increase in nonlinear loads. This paper presents a new method, based on interactive multiobjective nonlinear programming (MONLP), using genetic algorithms (GAs) to study passive filter planning. The short-circuit capacity of the point of common coupling (PCC) and the individual bus loads are modeled with the fuzzy sets. The harmonic voltages and the filter cost are minimized while satisfying the harmonic standard and harmonic power flow equations with the harmonic Y-matrix. An 18-bus system is used as a test system for showing the applicability of the proposed method.

Method for fabricating surface acoustic wave filter packages and package sheet used therein

Abstract: A method for fabricating Surface Acoustic Wave filter packages uses a package sheet having an outline pattern and anti-bur holes. In the package sheet for a Surface Acoustic Wave filter package, the outline pattern is formed along outer peripheries of chip mounting areas where a plurality of SAW filter chips are to be mounted. The outline pattern is contacted with a metal shield layer formed on the SAW filter chips and a predetermined region of the package sheet. Circular anti-bur holes are located at the corners of the chip mounting areas and on cutting lines along which the sheet is to be singulated into individual SAW filter packages.

Emi filter circuit

Abstract: Techniques for reducing noise generated by a circuit include a common mode filter and a differential mode filter. The common mode filter includes an input for sensing a common mode signal between a power source and the circuit, an output, and active circuitry for producing an offset signal on the output. The differential mode filter includes an input, an output, and active circuitry for sensing a differential mode signal and producing variations in resistance between the input and output to offset the differential signal.

Current driven polyphase filters and method of operation

Abstract: A filter circuit includes a polyphase filter coupled to a first circuit component and a second circuit component. The first circuit component propagates four input current signals to the polyphase filter. The third and fourth input current signals are substantially one-hundred-eighty degrees out of phase with the first and second input current signals. The polyphase filter receives the input current signals and generates four output current signals that are out of phase with each other. The second circuit component generates first and second output signals using the four output current signals. The first and second output signals are ninety degrees out of phase with each other.

Harmonic voltage reduction using a series active filter under different load conditions

Abstract: This paper proposes a series active filter using a simple control technique. The series active filter reduces the terminal harmonic voltages, supplying linear or even non-linear loads with a good quality voltage waveform. The operation principle, control strategy and theoretical analysis of the active filter are presented. These aspects were proven by the results of numerical simulations. Experimental results of the series active filter demonstrated its good performance under different load conditions.

Branching filter and communication device

Abstract: A branching filter and a communication device have excellent characteristics and an optimized configuration of a transmitting filter and a receiving filter. The branching filter includes a transmitting filter and a receiving filter wherein piezoelectric thin film resonators including a piezoelectric thin film sandwiched between opposed electrodes are arranged in a ladder type configuration on an opening or a recess of a substrate. The transmitting filter and the receiving filter are connected in parallel to an antenna terminal. The piezoelectric thin film resonators defining the transmitting filter and the piezoelectric thin film resonators defining the receiving filter are different from each other.

Compensation of filters in radio transmitters

Abstract: A radio transmitter for transmitting signals in a predetermined frequency band has a transmit filter and a compensating filter. The transmit filter filters a signal to be transmitted from the transmitter to suppress the transmission of parts of the signal outside the band. The compensating filter, e.g., operating in the digital domain, filters the signal upstream from the transmit filter, wherein the compensating filter is arranged to alter the signal to counteract at least one of a phase ripple, an amplitude ripple, and a group delay variation of the transmit filter within the band.

Piezoelectric devices mounted on integrated circuit chip

Abstract: An electronics filter circuit includes an electromechanical resonator that is mounted directly to the surface of a silicon integrated circuit, rather than being a surface mounted or leaded filter can on a circuit board. This filter circuit allows the integrated circuit electronic package to be significantly smaller than a conventional electromechanical resonator package. The electromechanical resonator may be protected during processing and during use with a protective cover that is made of a material such as titanium. The protective cover is attached to the integrated circuit chip.

Analysis of simple two-capacitor low-pass filters

Abstract: The performance of typical low-pass capacitor filters is limited by the mutual inductance between the input and output sides of the filter. This paper describes how two appropriately spaced capacitors can be used to construct a low-pass filter with significantly better high-frequency performance than a one-capacitor filter. Laboratory measurements and numerical simulations are used to quantify the mutual inductance and compare the performance of one- and two-capacitor low-pass filters.

Method and apparatus for a signal selective RF transceiver system

Abstract: Method and apparatus to dynamically configure the signal reception selectivity of a plurality of transceivers is described. In one embodiment, a transceiver includes a receiver circuit having two or more filter circuits. Each of the filter circuits is configured to pass RF signals from a different portion of an overall receiver bandwidth. When two or more receivers in proximity to one another are simultaneously operating, the filter circuits of the respective receiver are dynamically configured to different RF frequency passbands to minimize interference and cross talk between receivers and transmitters.

1.9 GHz range ultra-low-loss and steep cut-off double mode SAW filter for the Rx band in the PCS antenna duplexer

Abstract: This paper describes the DMS (double mode SAW) filter design techniques to achieve the ultra-low-loss and steep cut-off characteristics required for the Rx filter in the PCS (personal communications service) duplexer. It is the first attempt to employ DMS filters for antenna duplexers in mobile phones. It is demonstrated that the common ground inductance L/sub g/ and the coupling capacitance C/sub c/ between the input and output terminals of the DMS filters dramatically enhances the skirt steepness and the attenuation for the lower frequency side of the pass band. Based on this result, we propose a novel DMS filter structure that easily controls the L/sub g/ and C/sub c/ values. Moreover, we propose a compact DMS filter structure connected in parallel, which reduces the insertion loss. Applying these technologies to the Rx filter, we develop a DMS-employing PCS antenna duplexer.