Showing papers on "Electronic filter published in 2001"

Optimum filter bandwidths for optically preamplified NRZ receivers

Abstract: We present a comprehensive treatment of optically preamplified direct detection receivers for non-return-to-zero (NRZ) and return-to-zero (RZ) on/off keying modulation, taking into account the influence of different (N)RZ optical pulse shapes, specified at the receiver input, and filter transfer functions; optical Fabry-Perot filters (FPFs) and Bragg gratings as well as electrical fifth-order Bessel and first-order RC low-pass filters are considered. We determine optimum optical and electrical filter bandwidths and analyze the impact of bandwidth deviations on receiver sensitivity. Optimum receiver performance relies on a balance between noise and intersymbol interference (ISI) for NRZ transmission, while for RZ reception detection noise has to be traded against filter-induced signal energy rejection. Both for NRZ and 33% duty cycle RZ, optical filter bandwidths of around twice the data rate are found to be optimum. Receivers using RZ coding are shown to closely approach the quantum limit, and thus to outperform NRZ-based systems by several decibels. We further analyze the impact of important degrading effects on receiver sensitivity and optimum receiver bandwidths, including receiver noise, finite extinction ratio, chirp, and optical carrier frequency (or optical filter center frequency) fluctuations.

Considerations of a shunt active filter based on voltage detection for installation on a long distribution feeder

Abstract: This paper deals with a curious phenomenon referred to as the "whack-a-mole" that may occur in a long-distance distribution feeder having many capacitors for power-factor correction. The idea of whack-a-mole is that installation of an active or passive filter on the feeder makes voltage harmonics increase on some buses, whereas it makes voltage harmonics decrease on other buses, especially at the point of installation. The distributed-parameter representation is applied to a simplified feeder, thus making it possible to perform analysis of the whack-a-mole. As a result, this analysis yields such a basic way as to avoid the whack-a-mole. Moreover, both theory and experiment clarify that installation of the active filter acting as a harmonic terminator on the end bus of the feeder can damp out harmonic propagation throughout the feeder without causing any whack-a-mole.

Thin film bulk acoustic resonator (FBAR) and inductor on a monolithic substrate and method of fabricating the same

Abstract: An apparatus having both a resonator and an inductor fabricated on a single substrate and a method of fabricating the apparatus are disclosed. The apparatus includes a resonator and an inductor that is connected to the resonator. Both the resonator and the inductor are fabricated over their respective cavities to produce a high Q-factor filter circuit.

Cable modem tuner

Abstract: An IF input signal corresponding to a selected reception channel is applied through an SAW filter to an IF-AGC circuit, the amplitude of the signal is adjusted to a prescribed level, and the signal is thereafter supplied to a down converter unit The down converter unit selectively outputs a Low-IF signal provided by down-converting the IF input signal and the High-IF signal amplified without frequency conversion, in accordance with an external instruction A filter circuit has its cut off frequency selectively set to pass the Low-IF signal only, or both the Low-IF and High-IF signals

High frequency composite switch module

Abstract: A small-sized high-frequency composite switch module for selecting one of transmission/reception signals in frequency bands. The module comprises a multilayer body including a dielectric layer, a demultiplexing/multiplexing circuit, a switch circuit, a low-pass filter (LPF), a conductive pattern forming at least one of the demultiplexing/multiplexing circuit, the switch circuit, and the LPF and provided on the dielectric layer, a surface acoustic wave (SAW) filter mounted on the multilayer body, a cap portion provided on the surface of the SAW filter and adapted for hermetically sealing the space formed by the cap portion and enabling surface acoustic wave vibration, and a semiconductor switch element mounted on the multilayer body and constituting a part of the switch circuit.

Gaussian approach for performance evaluation of optically preamplified receivers with arbitrary optical and electrical filters

Abstract: A Gaussian approach (GA), which takes into account the influence of arbitrary optical and electrical filters, is proposed to analytically evaluate the performance of optically preamplified receivers. This GA also takes into account the effects of waveform distortion in the signal and in the signal-amplified spontaneous emission beat noise. Exact expressions for the mean and variance of the current at the decision circuit input are derived, which explicitly present the dependence on the optical and electrical filter transfer functions and take into account the presence or absence of a polariser. This GA is computationally much faster and simpler than more rigorous methods and the accuracy of its sensitivity estimates is investigated for different optical and electrical filters. It is shown that the GA predicts the optimal optical filter bandwidth very reasonably. Discrepancies below 1.2 dB are found between its sensitivity estimates and rigorous estimates. The assessment of the optical filter detuning impact on the receiver sensitivity is also investigated with this GA. Discrepancies less than 1 dB are found between the GA estimates and rigorous estimates. The GA sensitivity estimate's accuracy is also investigated in the presence of intersymbol interference (ISI) and very accurate predictions are obtained by the GA for significant ISI.

Solidly mounted multi-resonator bulk acoustic wave filter with a patterned acoustic mirror

Abstract: A method of fabricating a multi-resonator bulk acoustic wave (BAW) filter and a filter provided by such a method, the filter having a plurality of layers of materials serving as an acoustic mirror for a plurality of resonator sections, each resonator section including at least a top electrode and a bottom electrode sandwiching a piezolayer, the method including the steps of: choosing dielectric materials for some of the layers of materials serving as the acoustic mirror and metallic materials for the others of the layers; and providing at least one of the metallic layers via a fabrication procedure in which the metallic layer is patterned into distinct portions by an etching process that removes enough of the metallic layer between where different resonator sections are to be placed as to provide electrical isolation between the portions of the layer beneath the different resonator sections; thereby providing a multi-resonator BAW filter with reduced capacitive coupling between resonators, compared to the capacitive coupling present in a multi-resonator BAW filter fashioned in a similar manner except excluding the step of etching to pattern any metallic layers of the similarly fashioned acoustic mirror.

Parallel operation of passive power filter and hybrid power filter for harmonic suppression

Abstract: Harmonic pollution has been serious in recent years. Passive filters have been used to suppress harmonic current conventionally. However, passive power filters have the problem of resonance. To solve the resonance problem, active power filters and hybrid power filters were developed. After considering the power capacity and cost, the hybrid power filter is the better choice for the future. Many passive power filters have already been installed in the industry power systems. However, the elements of these passive power filters are often destroyed due to the resonance or the harmonic current injection of a neighbouring harmonic source. To improve the performance of passive power filters, a small capacity of hybrid power filter is proposed to connect in parallel with the existing passive power filters. The combined power filter system, which contains the parallel operation of existing passive power filters and hybrid power filters, is analysed and simulated. The simulation results show that the filter performance and resonance problem of existing passive power filters can be improved by applying the hybrid power filter.

Introduction to Microwave Circuits: Radio Frequency and Design Applications

Abstract: Preface Acknowledgments Microwave Circuits Models, Modeling, and Characterization S - Parameter Measurement Methods Multiport and Differential - Mode Scattering Parameters Stability, Stabilization, and Gain Matching Networks, Attenuators, and Phase Shifters RF/Microwave Power Generation Considerations Resonators and Oscillators Microwave Filter Design Noise Considerations for Microwave Circuits Detection and Mixing Microwave Components Pulsed Microwave Circuit Analysis Nonlinear Effects in Microwave Circuits Amplifier, Oscillator, and Filter Circuit Design Examples Appendix A: An Approximate Formula for the Characteristic Impedance of a Microstrip Line Appendix B: Some Complex Variable Facts Appendix C: Matric Multiplication Appendix D: Resistor, Capacitor, and Inductor Component Modeling Appendix E: Chip Resistor Sizes - Nominal Sizes Only Appendix F: S Parameters (Scattering Parameters - Current Referenced) Appendix G: Modeling Using an Equivalent Mechanical Model Bibliography Index About the Author

Recent advances in SAW packaging

Abstract: Continuous size reduction of today's mobile telephones in parallel with enhanced functionality demands for higher integration of components as well as for significantly reduced device and component size. Since modern surface acoustic wave (SAW) components combine superior filter functionality with small size, they play an important role in mobile phone evolution. Increasing the levels of functional integration and permanent miniaturization are therefore the major driving forces in current SAW filter development. Conventional wire-bonded ceramic, metal or plastic packages are to an increasing degree being replaced by space efficient flip-chip or chip-scale packages. EPCOS' proprietary packaging technology chip sized SAW package (CSSP) combines consequent package size reduction, filter application-specific technological features and outstanding internal electromagnetic performance made possible by the flip-chip technology. Specific CSSP technologies - each offering an optimum ratio between active chip space and package size - were developed for lower frequency (e.g. CDMA-IF) filters as well as for extremely frequency-precise IF-filters (e.g. GSM-IF), 1 GHz and 2 GHz RF filters, respectively. As functional integration like balun functionality or impedance transformation becomes more and more important for RF SAW filters, an integral design approach including acoustical and 3-D electromagnetic effects has to be used. The influence of sophisticated electromagnetic package design will be illustrated by examples resulting e.g. in superior amplitude and phase symmetry of balanced RF filters. Further size reduction will be obtained by integrating SAW filters with active as well as passive components in the frontend of cellular terminals.

A packaging methodology for duplexers using fbars

Abstract: Film bulk acoustic resonators when used in electronic filters are prone to small shifts in resonant frequency as a result of inductances in the ground paths. These inductances can create undesirable electrical and/or physical characteristics that effect performance. The degradation can be minimized if the physical layout of the filter and package.

Current-mode biquad with a minimum number of passive elements

Abstract: This brief reports a current-mode LP, HP and BP filter which ideally exhibits zero input and very high output resistance. All active and passive sensitivities are no more than one half in magnitude. The filter employs a minimum number of passive elements, only two capacitors and two resistors, and two filter functions can simultaneously be realized.

A 1.9 GHz Si active LC filter with on-chip automatic tuning

Abstract: The achievable quality factors (Q) of on-chip inductors fabricated with standard Si technology are limited. Inductor Q factors can be enhanced by active means, resulting in GHz-range filters with adequate dynamic range for certain applications. One such application is the replacement of off-chip filters in the transmit part of a wireless transceiver, following a mixer. The limits of the technique are tested here by using it in a filter for the entire band used in the PCS 1.9 GHz standard. A tuning-friendly filter can be built with magnetically coupled LC resonators. Two identical Q-enhanced LC resonators, together with the loading impedances, are used form a balanced 4th-order bandpass filter. The filter and its tuning system are implemented in a 0.25 /spl mu/m BiCMOS technology.

Application of the genetic algorithm and simulated annealing to LC filter tuning

Abstract: The paper discusses and compares the application of genetic algorithm and simulated annealing methods to LC filter tuning. Specifically, the paper is concerned with the application and implementation of these methods for the development of a fast microprocessor-based automatic antenna tuning unit, providing the facility to adapt to changes in load impedance, temperature or environment. A number of simulations were carried out to evaluate the relative performance of these algorithms. Finally, experimental results are presented where the simulated annealing algorithm was used to control a commercial impedance matching device in real time.

Odd-order low-pass pots device microfilter

Abstract: An odd-order low-pass microfilter is disclosed for being interposed between a home telephone wiring network and a POTS, or voice band, device to separate voice-band signals from higher frequency signals, such as ADSL signals and home networking signals. The filter topology is substantially symmetric so that the filter is reversible in that either end of the filter may be directly coupled to the home telephone wiring network without impairing high frequency signal performance or the filter characteristic of the filter. In one embodiment, the filter is a three-pole filter with a single capacitor disposed between a pair of coupled inductors. Each of the coupled inductors advantageously has an interwinding capacitance over about 100 pF to improve the filter frequency response without increasing the cost of the filter. In another embodiment, the filter is a reversible three-pole filter with a single capacitor disposed between first and second pairs of uncoupled, or discrete, inductors.

Saw filter with an attenuation pole including a band-pass ladder type of saw filter having a saw resonator

Abstract: A polar SAW (Surface Acoustic Wave) filter includes a band-pass ladder type SAW filter having a SAW resonator. A two-terminal pair circuit is serially connected to the band-pass ladder type SAW filter and includes a plurality of inductors. The polar SAW filter has attenuation poles in each of the higher-frequency and lower-frequency attenuation ranges of a pass band.

Saw filter using a carbon nanotube and method for manufacturing the same

Abstract: Disclosed is an element using a piezoelectric characteristic, and in particular, an SAW filter and a method for manufacturing the same. The SAW filter according to the invention is resistant to input wave of high power by employing ta-C or CNT as an acoustic wave transmission medium. The method for manufacturing the SAW filter according to the invention simplified the manufacturing process and reduced a transmission loss as well noise.

An image-rejecting mixer and vector filter with 55-dB image rejection over process, temperature, and transistor mismatch

Abstract: This paper describes an image-rejecting mixer and vector filter for use in radio systems with channel bandwidths in the range of 1 MHz. The circuit replaces the SAW filter and second downconverter commonly used in this style of radio. Because the output of the circuit is at an IF of 5 MHz, traditional demodulation methods including limiting and FM discrimination can still be used. The circuit is based on a quadrature mixer that guarantees good performance despite device mismatches and process variation. The circuit consumes 29 mA at 3.3 V,and achieves better than 55-dB image rejection despite device mismatches and process variation and is implemented in a single-poly triple metal 0.5 /spl mu/m CMOS process with linear capacitor implants. The circuit is designed for input signals from 125 to 250 MHz. Input referred voltage noise is 900 /spl mu/Vrms. The in-band IP3 is 18 dBm. By changing an external reference frequency, the passband width of the filter can be varied from 3 to 0.5 MHz.

High-frequency module and mobile communication apparatus using the same

Abstract: A high-frequency module includes a diplexer, first and second high-frequency switches, a SAW duplexer, first and second LC filters functioning as first and second filters, and an SAW filter functioning as a third filter. The module defines a unit that integrates front-end sections of first to third communication systems, a digital cellular system (1.8 GHz band), a personal communication service (1.9 GHz band) and a global system for mobile communications (900 MHz band).

Frequency dependent excursion limiter

Abstract: A circuit and method provides for the protection of transducers from over excursion, particularly for the protection of transducers for audio loudspeakers. A frequency dependent excursion limiter circuit has an initial summing stage followed by a shaping filter stage. A clamping function is provided at the summing stage, or at a separate stage between the summing stage and the shaping filter stage, for clamping the driving signal at a predetermined maximum voltage if the driving signal exceeds the predetermined maximum voltage level. The shaping filter stage provides a frequency response shaping function based on a predetermined frequency response shaping criteria which is related to the frequency dependent excursion limits of the transducers being protected from mechanical overload. An inverse shaping filter function is provided at the initial summing stage by providing feedback from the shaping filter stage, thus eliminating the need for a separate inverse shaping filter circuit before clamping. The inverse shaping filter function allows low level signals below clamping to pass through the circuit unaffected. A frequency dependent excursion limiter circuit is also provided in the closed loop circuit of servo feedback system for protecting transducers in a servo feedback system from over excursion.

Terminal for mobile communication system

Abstract: PURPOSE: A terminal for a mobile communication system is provided so that transmission spurious property can be improved by removing 8192MHz clock noise of a baseband, by adding IQ low band filters to a preceding terminal of an QPSK modulator CONSTITUTION: A low band filter(101) removes 8192MHz frequency from a baseband signal processor by filtering an IF baseband signal A QPSK modulator(102) modulates the baseband signal from the low band filter(101) An LC band filter(103) passes a necessary frequency band by filtering the intermediate frequency from the QPSK modulator(102) An auto gain controller(104) controls a gain of the transmission signal A frequency up converter(105) converts the transmission signal from the auto gain controller(104) to a radio frequency A radio frequency band filter(106) filters the radio frequency from the frequency up converter(105) to a predetermined band A pre-amplifier(107) amplifies the output signal from the radio frequency band filter(106) A drive amplifier(108) amplifies the output signal from the pre-amplifier(107) to a predetermined level A final amplifier(109) amplifies the output signal from the drive amplifier(108) As the result, transmission spurious property is improved without requiring a saw filter In addition, current consumption of the amplifiers can be remarkably reduced by removing the loss of the transmission signal

Filters with active tuning for power applications

Abstract: Passive filters for switched-mode power converters rely 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 applications and limitations 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.

Applications of describing functions to estimate the performance of nonlinear inductance

Abstract: Passive filter design is traditionally considered to be very important for many power electronic circuits and power systems. It is is very critical in the design of these power electronic circuits and power systems to know how to obtain accurate corner frequencies. It is known that when the load is large, the inductance of an inductor is known to always change. This phenomenon is due to the fact that when the current load is high, the inductance always suffers from saturation or hysteresis. It is extremely difficult to estimate the actual value for the nonlinear inductance in large currents because the inductance is nonlinear. The paper investigates the saturation phenomenon for a nonlinear inductance. The describing function method can be used to linearise the nonlinear inductor and then estimate the inductance in large current situations. Hence, the corner frequency for the lowpass filter can also be calculated accurately. It is shown that, when the current is very large, the corner frequency drifts to a larger value in the low-pass filter. The drift value of the corner frequency can be easily calculated by the describing function. Simulation and experimental results verify this phenomenon. However, it should be stressed that the method used in the paper is restricted to low frequencies. The higher frequency effects are neglected throughout the paper.

Transconductor and filter circuit

Abstract: A transconductor which has a transconductance gm and which receives an input voltage V In and outputs in response to the input voltage V in an output current I out of gm × V in , wherein: the transconductor includes a plurality of sub-transconductors which are connected in parallel to one another; and at least one control signal is input to the plurality of sub-transconductors, and the plurality of sub-transconductors are controlled by the at least one control signal such that at least one of the plurality of sub-transconductors has a negative transconductance, whereby the transconductance gm of the transconductor can be varied.

Surface acoustic wave filter

Abstract: A surface acoustic wave filter employing surface acoustic wave electrodes for forming a ladder filter circuit according to the invention, the SAW filter comprises a series resonator group including a plurality of surface acoustic wave electrodes formed on a surface of a piezoelectric substrate and electrically disposed in series between an input terminal and an output terminal; and a parallel resonator group including a plurality of surface acoustic wave electrodes individually electrically disposed in parallel between an input- or output-terminal of the individual surface acoustic wave electrodes of the series resonator group and a ground electrode, wherein a part number of the surface acoustic electrodes of the parallel resonator group is configured to deteriorate an obtained Q value and presents a resonant frequency which is lower than an antiresonant frequency and higher than a resonant frequency respectively formed by the other surface acoustic wave electrodes of the parallel resonator group Thus is obtained a steep shoulder characteristic curve on a lower side of a passband

Hybrid resonator microstrip line electrically tunable filter

Abstract: A novel hybrid resonator microstrip line electrically tunable filter is presented in this paper. The tunable filter has mixed combline resonators and a hairpin like resonator. With this mixed resonator filter, transmission zeros can be obtained on each side of the passband. This elliptic function filter response is achieved without any nonadjacent coupling. Parascan/sup TM/ dielectric material varactors are then used at the end of each resonator, so that the filter passband is electrically tunable. A 4-pole design example is provided. The transmission zeros are clearly shown in both simulation and measurement.

Filter circuit and a superconducting filter circuit

Abstract: A filter circuit includes a first resonator and a second resonator each having a different resonance frequency. The first resonator is included in a first block, and the second resonator is included in a second block. The first block further includes a first delay unit connected to the first resonator. An input terminal divides an input signal to the first block and the second block. An output terminal combines signals passing through the first block and the second block and outputs the combined signal. The first delay unit converts a phase difference between the signals passing through the first block and the second block to reverse-phase or nearly reverse-phase.

Package for filter design based on MATLAB

Abstract: Electric filters have a relevant importance in electronic systems because they are present in almost any electronic system. For example, communication systems, as many other electric systems, make intensive use of filtering to separate unwanted noise from the desired signal. Unfortunately, filter design is an intensive computational task requiring a significant amount of numerical calculations to obtain either the parameters of a filter transfer function or the element values for a filter circuit realization. This paper describes a software package whose purpose is to provide a tool to be used as a teaching aid in analog and digital filter design courses. The feature of this package is that it uses MATLAB [2] for the numerical computations. The main advantage of the filter design software package described in this paper is that makes uses of one of the MATLAB toolboxes, the signals toolbox (which is used for analog and digital filter design), but used with an interface that makes possible even to the novice user to readily design filters, either analog or digital, without any previous knowledge of MATLAB or the signals toolbox. © 2002 Wiley Periodicals, Inc. Comput Appl Eng Educ 9: 259–264, 2001; Published online in Wiley InterScience (www.interscience.wiley.com.); DOI 10.1002/cae.cae.10004

Full-wave analysis of RF SAW filter packaging

Abstract: As SAW filters move to higher frequencies and smaller sizes, the packaging structure has an increasing effect on the electrical performance of the device. In order to correctly design a SAW filter, the package performance must be considered concurrently in the design process. This paper describes several new methods for package simulation in which a full-wave electromagnetic (EM) simulator is used to create a package model. A ceramic chip and wire package is used to demonstrate the techniques. The package model is combined with a model of a SAW ladder filter at 1960 MHz and compared to measured data. The full-wave simulation is first performed on an empty package, with inductors used to represent bond wires. More accuracy can be achieved if simplified bond wires are included in the full-wave analysis, although computation time increases. A more accurate model of the bond wire shape increases simulation time, with no increase in accuracy. Our results demonstrate that full-wave analysis techniques are useful for predicting critical parameters such as the shape and rejection level of a SAW filter.

A system and method for employing pulse width modulation for reducing vertical segregation in a gas discharge lamp

Abstract: In accordance with one embodiment of the present invention a system for driving a gas discharge lamp is comprised of a bridge circuit configured to provide a pulse voltage signal, a controller configured to generate a pulse width modulated signal corresponding to a desired waveform. A filter circuit is also configured to receive and filter the pulse voltage signal provided by the bridge circuit. In one embodiment of the invention the gas discharge lamp is driven by a pulse voltage signal corresponding to a pulse width modulation signal. The pulse width modulated signal is generated corresponding to a desired waveform, wherein the desired waveform includes a sweeping frequency signal and a fixed frequency amplitude modulating signal.