Showing papers on "Electronic filter published in 1994"

Trends in active power line conditioners

Abstract: Active power line conditioners, which are classified into shunt and series ones, have been studied with the focus on their practical installation in industrial power systems. In 1986, a combined system of a shunt active conditioner of rating 900 kVA and a shunt passive filter of rating 6600 kVA was practically installed to suppress the harmonics produced by a large capacity cycloconverter for steel mill drives. More than one hundred shunt active conditioners have been operating properly in Japan. The largest one is 20 MVA, which was developed for flicker compensation for an arc furnace with the help of a shunt passive filter of 20 MVA. In this paper, the term of "active power line conditioners" is used instead of that of "active power filters" because active power line conditioners would cover a wider sense than active power filters. The primary intent of this paper is to present trends in active power line conditioners using PWM inverters, paying attention to practical applications. >

Low line harmonic ac to dc power supply

Abstract: The PWM control scheme is illustrated in conjunction with a power distribution control circuit (30), wherein the duty cycle of convverter (32) is suitably controlled by a number of feedback loops embodying various parameters, for example a voltage error signal, an average (eg. RMS) value of the input voltage (Vin). Circuit (30) comprises a rectifying circuit (42), a converter circuit (32), for example an AC-DC converter, a capacitor (C), an oscillator and PWM circuit (44), an error signal (46), a multiplier circuit (48), a differencing amplifier (50), and a synthesizing circuit (52). Circuit (30) appears as a resistive load to the line for feed PWM, a fixed load, and a fixed RMS input voltage. To stabilize the output voltage (Vout), the pulse width signal (44a) applied to converter suitably varies in proportion to both changes in the RMS value of the input voltage and the output voltage. The output voltage error signal applied to multiplier circuit by error circuit provides the correction value for Vout variations. The line RMS signal applied to multiplier by the line RMS filter circuit (52) compensates the PWM signal for variations in the RMS value of Vin. In this regard, the RMS loop modulator control signal may be advantageously normalized by Vrms (square) since Pin varies as Vin (square). Decreases in either the output error signal or the RMS signal increase the PWM value.

Assembly of filtering apparatus and replaceable filter; and filtering apparatus and filter for use therein

Abstract: An assembly of a filtering apparatus and a replaceable filter comprises an electronic filter identification system having an electronic label on the filter and read-out means on the filtering apparatus. The read-out means is connected to a control unit of the filtering apparatus and the control unit is influenced by the read-out means. For example, the control unit is only actuatable upon disposing a filter in the filtering apparatus having a proper label. The filter identification system may be interactive.

Interface between SAW filter and Gilbert cell mixer

Abstract: The invention concerns multipliers used to modulate a carrier by a signal. The signal is delivered by a Surface Acoustic Wave (SAW) filter, which requires a load impedance of low value, in the range of tens of ohms, and almost certainly less than 200 ohms. The invention modifies a Gilbert multiplier such that its signal-input stage presents the required load impedance to the SAW. The input impedance of the signal-input stage is adjustable.

Hybrid series active/parallel passive power line conditioner with controlled harmonic injection

Abstract: A power line conditioner includes an active filter coupled, in series, and a passive filter coupled, in parallel, to a three-phase power distribution network The three-phase power distribution network includes a voltage source that induces three-phase input currents at a first end of the three-phase power distribution network A load, circulating three-phase load currents, is positioned at a second end of the three-phase power distribution network The active filter controller of the invention uses synchronous transformations to identify selected harmonic reference components corresponding to individual harmonics of the three-phase load currents The selected harmonic reference components are multiplied by a predetermined factor corresponding to a permissible percentage of the individual harmonics that may be injected into the supply voltage This results in active filter reference signal components that are applied to the active filter In response to the active filter reference signal components, the active filter injects a permissible percentage of harmonics into the supply voltage so as to reduce the voltage distortion at the passive filter By reducing voltage distortion, the controlled injection of harmonics into the supply allows for a simplified passive filter design Consequently, the passive filter may be implemented as a power factor correction capacitor

Multilayer suspended stripline and coplanar line filters

Abstract: Using metallization patterns on both sides of a suspended stripline substrate or adding an additional dielectric and conductor layer to coplanar line circuits, additional degrees of freedom arise for filter design like an extended range of impedances, tightly coupled line structures or increased end coupling between lines of different metallization layers. In this way, very compact filter circuits with improved performances may be realized as it is shown for different types of filters using this technique, even including active elements to realize strongly frequency selective amplifiers or active filters. >

Input Filter Design for PWM Current-Source Rectifiers

Abstract: Pulse-width modulated (PWM) rectifiers are increasingly used because they allow the elimination of low-order harmonics, and therefore a reduction in input filter components. Filtering requirements for PWM current-source rectifiers are usually satisfied through the use of low-pass LC input filters. This paper offers a systematic and user-friendly approach to choosing the filter components. Design of LC filters involves the positioning of the resonant frequency to meet the harmonic attenuation requirements (THD), and introducing damping at the resonant frequency to avoid amplification of residual harmonics. The problem is further complicated by considerations related to cost, power factor, voltage attenuation, system efficiency, and filter parameter variation. The systematic approach proposed in this paper focuses on PWM rectifiers, but can easily be extended to other classes of converters. Practical design considerations are detailed and design equations derived. Simulated results are presented to validate the design approach

Review of models for low-loss filter design and applications

Abstract: The most frequently used models for surface acoustic wave (SAW) devices are the impulse model, the equivalent circuit models, the Coupling-of-Modes model, and the matrix models. While the impulse-model is only a first order model the other models include second order effects, e.g. reflections, dispersion, and charge distribution effects. The influence of diffraction and refraction on the transfer function of a SAW filter can be described by the angular spectrum of straight-crested waves model. A survey of these different models will be given. The simulation of low-loss filters requires flexible analysis tools, which can cope with different geometries and substrates. Operating with a parameter set, which depends only on the substrate crystal and not on the specific geometry of the SAW filter, is advantageous. Due to the high insertion attenuation of conventional transversal filters the requirements on the accuracy of the analysis are focused on S21, whereas for low-loss filters all elements of the S-matrix are important. The comparison of simulations with a P-matrix model, which fulfills the above mentioned prerequisites, and measurements of different types of low-loss filters, e.g. SPUDT, DMS, and transverse-mode coupled resonator filters are presented

Method and apparatus for reducing power consumption of a fan in a computer system

Abstract: A circuit for controlling power consumption of a fan within a computer system having a central processing unit (CPU) is described. The circuit includes a filter circuit coupled to receive a periodical pulse signal for detecting duty cycle of the periodical pulse signal by converting the periodical pulse signal into an analog signal. The analog signal has a voltage level proportional to the duty cycle of the periodical pulse signal. The periodical pulse signal is generated to control the CPU to be operational between predetermined intervals when the CPU is in an inactive state. A comparator circuit is coupled to the filter circuit for comparing the voltage level of the analog signal with a predetermined voltage level. When the voltage level of the analog signal is below the predetermined voltage level, the comparator circuit generates a switching signal. A switching circuit is coupled to (1) a power supply, (2) the fan, and (3) the comparator circuit for disconnecting the power supply from the fan when the switching signal is generated by the comparator circuit so as to substantially reduce the power consumption of the fan in the computer system when the CPU is in the inactive state. A computer system having the circuit for controlling power consumption of a fan in the system and a method for controlling power consumption of a fan in a computer system are also described.

A 3.3 volt electronically tunable active filter usable to beyond 1 GHz

Abstract: A very high frequency low voltage active filter is proposed which is based on the "log filters" introduced by Frey (1993). These filters have been shown to be a special case of exponential state space filters. Log filters are particularly well suited for high frequency applications since they are essentially current mode networks. They are also well suited to low power supply operation, not only because of their current-mode nature, but also because there is no overhead associated with linearization, since the intrinsic nonlinearity is an integral part of the design formulation. In this paper it is shown that log filter topologies are possible which function well at 3.3 volts. >

Design of active RLC integrated filters with application in the GHz range

Abstract: In this paper we discuss a method for making possible the active parallel-mode compensation of on-chip inductor and capacitor losses, and for making both the quality factor and the inductance value electronically tunable The application of this technique in filters is emphasized throughout, and is demonstrated in a 2nd-order bandpass filter The paper provides analytical results, discusses transistor-level circuits and presents experimental results from a linearity test on a breadboard >

Reception band switching circuit with variable attenuation control

Abstract: The invention provides a filter circuit for use in a double-conversion TV tuner exhibiting low diode insertion loss, in which intermodulation distortion does not occur even when an incoming signal has a large amplitude. In the filter circuit according to one preferred embodiment of the invention, there are provided three bandpass filters (BPFs) which allow corresponding RF signals in different frequency bands to pass through them, and six variable attenuation diodes whose impedance is controlled by an AGC voltage applied to an AGC terminal (16). There are also provided switching diodes (20) disposed between an input terminal (1) and the inputs of three BPFs so that the switching diodes (20) select exclusively one of three BPFs so as to apply an RF signal received at the input terminal (1) only to the selected BPF (it will be assumed hereinbelow that the BPF (21) is selected). In this arrangement, not only the impedance of variable attenuation diodes (22, 23) in the selected BPF (21) which provides the extracted RF signal, but the impedance associated with all variable attenuation diodes is controlled by the AGC voltage.

Peak accelerated compressor

Abstract: A peak accelerated compressor comprising a voltage controlled amplifier, a level detector and a peak accelerated filter circuit. The voltage controlled amplifier circuit is utilized for processing an input audio signal and producing an output audio signal. The level detector circuit is utilized for processing a sample audio signal which contains transient peaks and average waveforms. The peak accelerated filter circuit is coupled between the level detector circuit and the voltage controlled amplifier circuit for producing a control output signal to change the gain of the voltage controlled amplifier circuit in response to the transient peaks in the sample audio signal. The peak accelerated compressor effectively enhances the compression for transient peaks without adversely affecting the normal compression of average waveforms.

Hybrid phase locked loop

Abstract: A phase locked loop system or other second order feedback system whose natural frequency scales with its output and whose damping factor remains constant includes a filter circuit having a scaling channel for scaling the error, an integrating channel for integrating the error, and a summing circuit for combining the scaled error and integrated error; an integrator circuit responsive to the summing circuit to produce an output signal, the gain of the integrator circuit being proportional to its output signal; and a control circuit for controlling the gain of the integrating channel proportional to the output signal and maintaining constant the ratio of and scaling the product of the unity gained frequency and the zero frequency of the feedback system to keep constant the damping factor and to scale the natural frequency of the feedback system with the output signal, respectively.

Surface acoustic wave filter with multiple ground terminals

Abstract: In a surface acoustic wave (SAW) filter, on a 36° Y-cut X-propagation lithium tantalate substrate, series branch SAW resonators, which are connected in series between an input terminal and an output terminal, and parallel branch SAW resonators, which are connected between respective pairs of the series branch resonators by wirings and which are grounded, are provided Two series branch resonators and one parallel branch resonator are connected in a T shape, so as to form a fundamental unit In the SAW filter, three fundamental units are serially connected An interdigital transducer (IDT) included in each resonator is made of a metal film containing aluminum as the main component The thickness of the metal film is in the range of 8% to 10% of the electrode pitch of the IDT of the parallel branch resonator

Filter circuit with bandwidth varied as a function of bit error rate and luminance level

Abstract: An arrangement for enhancing an image corresponding to a television signal including a digital component includes a variable bandwidth filter and a control unit for controlling the bandwidth of the filter in response to the bit error rate (BER) of the digital component of the television signal. The control unit increases the bandwidth as the BER and therefore the signal quality increases and decreases the bandwidth as the BER and therefore the signal quality decreases. In one embodiment, the control unit is responsive to both the BER and the "darkness" of the image represented by the television signal so as to restrict the bandwidth more for relatively dark areas than for relatively light areas.

Reduced vlf overload susceptibility active noise cancellation headset

Abstract: The susceptibility of an active noise cancellation system to overloading due to very low frequencies is reduced by subtracting the low frequency components of an applied noise field from the residual signal. Low frequency components of the applied noise field outside the normal range of human hearing are detected by an external sensor (14) and isolated by a filter circuit (15). The isolated low frequency signal is subtracted from the residual signal, resulting in a modified residual signal with reduced low frequency components. The cancellation system thus eliminates very low frequency cancellation signals, without sacrificing bandwidth or system performance within the audible range.

Genetically derived filter circuits using preferred value components

Abstract: In the realisation of discrete-component analogue electronic circuits it is common practice, because of costs, to specify passive component values from a set preferred of values. For the design of integrated circuits it can also be desirable to use a standard set of passive component values. For example, to obtain accurate ratio matching of integrated resistors and capacitors by stacking identical unit valued components. The usual design approaches produce circuits in which the permitted component values are assumed to be unrestricted. The circuit is then converted to a practical circuit by simple rounding of the exact component values to the nearest value in the permitted set. Of course, in general the circuit performance realised will differ from the ideal. It may then be necessary to repeat the design with a more stringent specification or to use a more closely spaced set of permitted values, both of which can have cost implications. However if other combinations of permitted values are considered, a better circuit performance may potentially be achieved than that obtained by simple rounding. The difficulty is that in all but trivially simple circuits the space of all feasible combinations to be searched is huge. Genetic algorithms (GAs) can be used to search this space. There the application is to a simple second order active filter specified by its transfer function parameters. The aim of the present contribution is to show that GAs can be successfully applied to more complex filter structures. Moreover the optimal search is carried out directly on the frequency-response template specification rather than on a specified approximating ideal transfer function, thereby avoiding this additional source of approximation. The next section outlines the basic GA and its implementation for the present application. Results are then given for practical filter examples. An all-pole low pass response is considered with template specified by a 1 dB pass band ripple with a pass band edge at 10/sup 5/ rad/sec, and stop band attenuation of -150 dB at a stop band edge of 10/sup 6/ rad/sec. The GA is used to generate both LC ladder structures and the more complex FDNR active RC structures. >

Differential saw filter including series coupled resonant/antiresonant tracks

Abstract: Resonant and anti-resonant inter digital transducers are coupled on acoustic tracks (302, 304, 306) of a piezoelectric substrate (301) to provide a balanced differential surface acoustic wave (SAW) filter (300).

Active DC filter for HVDC systems

Abstract: In pursuit of higher performance and lower cost for harmonic filtering in high-voltage direct current (HVDC) power transmission systems, a prototype of an active DC filter was developed and installed on the DC line at the Lindome converter station of the KontiSkan 2 HVDC link between Sweden and Denmark at the end of 1991. This installation provides practical evidence that an active filter is possible for high voltage transmission systems and that this could be a better and cheaper alternative than the conventional passive filter. The filter is described as is its control and protection. >

Power inverter for use in system interconnection

Abstract: A power inverter for use in the system interconnection of a direct-current supply with a commercial alternating-current supply includes an inverter circuit and a filter circuit. Feedback signals affecting the frequency of an output to be produced by the inverter circuit are taken from the filter circuit having frequency response characteristics such that the phase angle is reduced to 0° at three frequencies consisting of a higher frequency, lower frequency and commercial frequency, the last of which lies halfway between the first and second. Under the normal condition, the frequency of the output produced by the inverter circuit is equal to the commercial frequency. In the event of a power failure or power cut in the commercial alternating-current supply system, deviation from the commercial frequency is caused by the characteristics of the filter circuit.

Electronic Filter Analysis and Synthesis

Abstract: Electronic Filter Analysis and Synthesis helps you save time and effort in writing CAD and analysis programs for electronic filters, and provides explicit details on how to synthesize lowpass, bandpass, bandstop, and highpass realizations for passive, active, digital and switched capacitors.

Tunable filter circuit and method therefor

Abstract: A tunable filter circuit (340) has a ceramic block forming a portion thereof. Transmission lines (352', 372', 392', 412') are formed of resonating cavities which extend through the ceramic block, and variable capacitors (364, 384, 404, 424) capacitively load the transmission lines (352', 372', 392', 412'). By varying the capacitance of the variable capacitors (364, 384, 404, 424), the filter characteristics of the filter circuit comprised of the ceramic block and the variable capacitors is varied. The tunable filter circuit (340) may, for example, comprise a portion of a cellular radiotelephone operative in a TDMA communication scheme.

Continuous-time filters using buffers with gain lower than unity

Abstract: Techniques for implementing very simple filters in integrated form are discussed. The only active elements used are buffers with voltage gain lower than unity. >

New design procedures and experimental results of SAW filters for duplexers considering wide temperature range

Abstract: New types of SAW filter called lextended SAW resonator coupled filterr using different substrates have been developed for 800 MHz cellular systems. Design and synthesis procedure for new SAW filters are discussed. Experimental frequency responses and temperature characteristics are also given for the filters used in an antenna duplexer of ETACS, EAMPS, and NTACS cellular systems

Digital vs. SAW matched filter implementation for radar pulse compression

Abstract: The implementation of a full-digital system for radar pulse compression is described. The use of a high-speed FFT processor allows the matched filter to operate in the frequency domain at a throughput rate of some MHz. FM signals having time-bandwidth products up to 512 can be processed. By using the sophisticated procedures developed for chirp waveform design in SAW filter implementations, the system is shown capable of providing compressed pulses with satiable levels in the 50 dB range. Significant experimental results are reported, and compared with those yielded by equivalent SAW compressors

Ultrasonic motor and electronic equipment with ultrasonic motor

Abstract: PROBLEM TO BE SOLVED: To stop a motor in a specific position without consumption of a current, make less likely of being affected by vibration or the like from the outside, by cutting the frequency components of specific frequency or higher, through a filter circuit in an input signal which is a command signal of positioning to a control circuit. SOLUTION: A drive circuit 18 receives a control signal to input a drive signal, based on the control signal to an ultrasonic motor 1. A moving unit 8 of the ultrasonic motor 1 or a self-propelled vibrating unit receives these flows to move to a designated position based on an input signal 15. Here, a signal processing circuit 16 is provided between the input signal 15 and a control circuit 17. The signal processing circuit 16 is formed as a filter circuit which cuts the components of specific frequency or higher of the input signal 15, or the control signal is output, only when a change width of the input signal 15 is a prescribed value or more, or the control signal is intermittently output in accordance with an averaged value of a number of detection samples of the input signal 15, so that vibration and unnecessary operation of a control system can be prevented.

Saw filter with a coupled saw impedance element

Abstract: This invention relates to an electronic device having a frequency dependent signal transfer characteristic which is electrically coupled to at least one SAW transducer. The SAW transducer acts as a SAW impedance element since it exhibits frequency dependent electrical characteristics. Such characteristics are utilised so that the transmission loss of the SAW impedance element is high in a relatively low signal transfer region of the signal transfer characteristic of the electronic device, and low in a relatively high signal transfer region of the signal transfer characteristic of the electronic device. This has the advantage that signals outside of the passband of the electronic device can be attenuated without increasing the transmission loss of the electronic device in its passband.

Balanced bridge saw filter

Abstract: The invention relates to a SAW filter comprising a first and second pair of substantially equivalent SAW transducers electrically coupled to form a bridge circuit. Each of the transducers of the first pair of transducers have a center frequency which is slightly different to the center frequency of each of the transducers of the second pair of transducers. The product of the static capacitance of the first pair is the same as the product of the static capacitance of the second pair. In use, signals input to the filter and having a frequency within the passband of the filter are coupled to the output of the bridge circuit via one or other or both arms of the bridge, as in normal bridge circuit operation. However, out of band signals are blocked since all the transducers are equivalent capacitors having the same capacitance (i.e., static capacitance). Thus, transmission of out of band signals through the filter is inhibited by the balanced nature of the bridge.

SAW electric part and frequency conversion circuit

Abstract: According to this invention, an SAW electric part includes an SAW filter and an SAW oscillator formed on a substrate having the same temperature characteristics as those of a substrate on which the SAW filter is formed. A frequency converter includes the SAW electric part, a second local oscillation circuit, a frequency converter, a first mixer, and a second mixer. The second local oscillation circuit oscillates a second local oscillation signal using the SAW oscillator. The frequency converter converts a frequency of the second local oscillation signal to generate a first local oscillation signal. The first mixer mixes the first local oscillation signal with an input signal to output a composite signal to the SAW filter. The second mixer mixes an output from the SAW filter with the second local oscillation signal to output a frequency conversion signal.