Showing papers on "Electronic filter published in 1976"

Direct SFG simulation of LC ladder networks with applications to active filter design

Abstract: The "leap frog" active synthesis technique is generalized to include simulations of more general LC ladder networks such that a one-to-one correspondence' between reactive elements and active integrators is maintained. This is accomplished through the introduction of two special "port reciprocators" which together with a set of basic signal flow graph building blocks and a set of interconnection rules forms a complete active synthesis technique. A design example is presented and a method of reducing the number of amplifiers required is outlined.

The design and operation of practical charge-transfer transversal filters

Abstract: Some of the design considerations for charge-transfer split-electrode transversal filters are discussed. Clock frequency, filter length, and chip area are important design parameters. The relationship of these parameters to filter performance and accuracy is described. Both random and tap weight quantization errors are considered, and the optimum filter length is related to tap weight error. A parallel charge-transfer channel, which balances both capacitance and background charge, and a coupling diffusion between split electrodes greatly improves accuracy. A one-phase clock is used to simplify the readout circuitry. Two off-chip readout circuits are described, and the performance of two low-pass filters using these readout circuits is given. Signal to noise ratios of 90 dB/kHz and an overall linearity of 60 dB have been achieved with this readout circuitry.

Design of active R filters using only resistors and operational amplifiers

Abstract: Active filters can be designed using only resistors and amplifiers as the circuit elements. The reactance for these filters is obtained from the parasitic capacitances associated with the amplifiers. The resonant frequency and Q of the poles and the location of the zeros can be controlled over a wide range by resistor feedback and feedforward circuits. General configuration for the first-, second- and third-order filter building blocks may be used in cascade to achieve any desired filtering function. The basic building block is constructed from only two amplifiers and three resistors. This circuit simultaneously exhibits low-pass, high-pass, and band-pass functions, respectively, at its three outputs. A simple summing network allows these outputs to be summed to obtain any second- or third-order filter function. In addition to simplifying the circuit configurations, the active R filter technique results in filters which may be operated at much higher frequencies than classical active RC filters. In fact, ...

Broadband microwave bias network

Abstract: For supplying a bias (modulation) signal, either AC or DC, to a microwave circuit, a network consisting of a low pass filter is provided which presents a high isolating impedance to an extremely wide bandwidth of microwave frequencies, while allowing low frequency bias or modulating signals to be supplied to the microwave circuit without significant attenuation. The network consists of two helical inductors, one within the other, plus a bypass capacitor. The inner small inductor presents a high, non-resonant impedance to high microwave frequencies and the outer, larger inductor presents a high impedance to lower microwave frequencies. The bypass capacitor cooperates with the outer inductor to complete the filter circuit for the lower microwave frequencies. The smaller inductor's proximity to and within the larger inductor provides a distributed shunt capacitance to ground so as to terminate the filter for the higher microwave frequencies at the smaller inductor.

Implantable receiver circuit

Abstract: In an implantable receiver circuit there is provided a tuned filter responsive to externally provided radio frequency energy bursts. The receiver also includes a pair of oppositely poled diodes for respectively providing positive and negative rectified versions of the energy bursts. The cathode of one diode is coupled through a low-pass filter circuit to an output capacitor and the anode of the other diode is coupled through a low-pass filter to the control electrode of a semiconductor switching device, the main electrodes of which are coupled between the output capacitor and the point of reference potential. With this connection the switching device is rendered conductive during the time no energy burst signals are applied to the tuned circuit thereby allowing the output capacitor to discharge during this time. During the time an energy burst is provided, the second rectifier circuit maintains the switching device non-conductive.

An insensitive active-RC filter for high Q and high frequencies

Abstract: An operational-amplifier filter circuit is presented, which can realize a high Q at high frequencies, with low sensitivity to both the passive circuit components and the operational-amplifier gain-bandwidth products. Unlike most of the reported high- Q high-frequency circuits, which use positive feedback, this is a negative-feedback circuit and is based on the principle of the two-integrator loop.

Horizontal AFC circuit in a television receiver usable with a video signal recording and reproducing apparatus

Abstract: A horizontal AFC circuit comprising a phase detector circuit supplied with a horizontal synchronizing signal separated from a television video signal and with a comparison signal and carrying out phase comparison, a filter circuit for filtering the output of the phase detector circuit, a horizontal oscillator circuit supplied with the output of the filter circuit and oscillating with an oscillation frequency controlled thereby, a horizontal deflection circuit for forming the output signal of the horizontal oscillator circuit into a horizontal deflection pulse, a wave shaping circuit operating upon being supplied with the output pulse of the horizontal deflection circuit to wave shape this output pulse and to supply the resulting output signal thereof as said comparison signal to the phase detector circuit, means for supplying a control pulse of a pulse width corresponding to a vertical blanking period of the television video signal, and loop gain control means supplied with the control pulse and operating to cause the loop gain of the horizontal AFC circuit to be relatively large in the pulse width duration and to cause the loop gain to be relatively small in a period other than said pulse width duration.

Charge-coupled devices for analog signal processing

Abstract: CCD's are inherently analog and can be used to implement a number of sampled data filtering functions in the analog domain. The CCD transversal filter is a particularly cost effective building block because of its versatility and simplicity. The limitations and applications of CCD transversal filters are summarized, and their cost advantages relative to digital filters are discussed.

Anti-aliasing pre-filter circuit for semiconductor charge transfer device

Abstract: An on-chip semiconductor pre-filter device is designed with a prescribed low frequency passband (0 to f) and a prescribed stopband (F±f), with a frequency roll-off therebetween. The pre-filter performs a weighted averaging of signal samples taken from an input electrical signal at a suitable sampling frequency and converts the weighted average into an equivalent charge packet for input by injection into a semiconductor charge coupled device (CCD) driven on the same chip by a clock of frequency F. In this way, the "reflected" parts (in band: F±f) of the frequency spectrum of the CCD are suppressed from the input to the CCD, thereby suppressing undesired aliasing in the CCD.

Electronic musical instrument having an electronic filter with time variant slope

Abstract: An electronic musical instrument capable of changing a slope portion of a filter characteristic continuously from start to completion of production of a musical tone. The inventive electronic musical instrument changes a filter slope in a frequency region above or below a cut-off frequency with lapse of time and, in order to achieve such change in the filter slope, changes a slope factor continuously from start to completion of production of the tone. The instrument is also capable of changing the cut-off frequency. An example of a low-pass filter is shown in which a desired form of a successively changing filter slope can be obtained by employing four slope factor values and three values representing a speed of change of the slope factors as well as three cut-off frequency values and two values representing a speed of change of the cut-off frequencies.

Tunable electrical filter network

Abstract: A tunable electrical filter is disclosed wherein an RC (resistor-capacitor) network comprising a plurality of switchable capacitors among the components determining the time constant of the filter provides a given minimum value of filter time constant and, therefore, a given minimum bandwidth, when all the capacitors are continuously connected in the network. Each capacitor is coupled to the network through the output means of an electronic switching means. A pulse generator connected to the input means of said switching means provides a train of pulses having an adjustable ON-time to OFF-time ratio. When all the capacitors are periodically switched by the output of the pulse generator, the effective filter time constant increases from said given minimum value as the ON-time compared with the OFF-time decreases. The pulse generator is provided with control means for adjusting the ON-time to OFF-time ratio. Operation of the control means will, therefore, enable the filter to be tuned within a predetermined range.

A reprogrammable filter bank using charge-coupled device discrete analog-signal processing

Abstract: A filter bank having up to 32 channels is formed by multiplexing a recursive two-pole delay line filter Thirty-two sets of filter constants are stored and addressed digitally while multiple delays are provided in analog form by a charge-coupled device (CCD) delay line The interface between the digitally stored constant and the delayed analog signal occurs in a four quadrant multiplying D/A where the delayed analog signal is weighted by the constant Sampling and clamping at the CCD interfaces insures accurate dipolar analog operation The filter hardware is described, the filter constants are derived, and the performance is documented

Voltage controlled electronic filter

Abstract: The response characteristics of an electronic filter are automatically adjusted as a function of the magnitude of an applied DC voltage to permit the same filter to be used for varying applications. Embodiments for varying the center frequency and Q of the filter are disclosed. The filter has particular utility in vibration monitoring systems wherein the center frequency may be selectively set at a value which is characteristic of the frequency of particular vibration signals of interest. In a disclosed vibration monitoring system incorporating the voltage controlled filter of this invention, which is particularly useful for monitoring vibration levels in gas turbine engines, the magnitude of the DC control voltage is varied as a function of gas turbine rotational velocity. In an alternate embodiment of the vibration monitoring system an adjustable feedback circuit is provided which may be set to reduce variations in phase shift as the center frequency of the filter is varied or alternatively to automatically track a particular center frequency.

Filter circuit having an acoustic surface-wave filter device

Abstract: A filter circuit includes an acoustic surface-wave filter device having an input transducer comprised of a set of interleaved electrodes disposed on a first portion of a body of piezo-electric material adapted to propagate acoustic surface waves for producing an acoustic surface-wave signal in response to an input signal applied to the input transducer, and an output transducer comprised of a set of similar interleaved electrodes disposed on a second portion of the piezo-electric body spaced a selected distance from the first portion for receiving the acoustic surface-wave signals so as to produce a corresponding output signal having a selected frequency response. The frequency response (e.g., bandwidth) of the acoustic surface-wave filter device is controlled by selectively changing the number of conductor elements constituting the interleaved electrodes of the input and output transducers. An amplifier drives the acoustic surface-wave filter device, the gain and output impedance of the amplifier being changed as the frequency response of the acoustic surface-wave filter device changes, so as to compensate for corresponding changes in the insertion loss and input impedance of the filter device.

Electronic filter circuit

Abstract: An electronic filter circuit having controlled "Q" with variations in attenuation. A plurality of filter networks are connected in parallel between the output and the input of an amplifier in a manner such as to be capable of selectively providing negative feedback to the amplifier. Each filter network includes inductive, capacitive and resistive elements, with a potentiometer forming part of the resistance thereof. Each potentiometer is connected in series with a resistor having the same value thereas, the arm of the potentiometer being connected to its associated filter network such that the "cut" to which the potentiometer is set determines the total value of the resistance presented by the filter network in the feedback circuit. The potentiometers and associated resistors are each connected in series with each other, these series connected elements being connected in parallel between the input and the output of a unity gain amplifier. With the potentiometers in the "flat" positions, the feedback signals are zero and thus have no effect on the output of the main amplifier. Various amounts of frequency responsive attenuation are provided by various settings of selected potentiometers.

A useful sensitivity measure for second-order RC active filter design

Abstract: A new sensitivity measure is proposed 'that could be useful for comparison between or optimization of second-order filter cells. It can be related to the well-known Q - and \omega_{0} -sensitivities by a simple analytic expression, yet It Is a more realistic design criterion. Furthermore it is shown that high- Q cells should not be compared on basis of their Q - sensitivities only.

Engineering design and evaluation of s.a.w. pulse compression filters with low time sidelobes

Abstract: A linear f.m. pulse compression sub-system employing surface acoustic wave dispersive filters has been designed. When operated as a coherent pulse compression loop, this sub-system provides a compressed pulse with all time sidelobes suppressed by more than 40 dB. This demanding level of performance which is a significant improvement over previously reported sub-systems has been achieved by the development of a design procedure which permits compensations for the spectral ripples of the transmitted waveform to be incorporated in the design of the compression filter. Measurement of amplitude and phase characteristics of the compression filter indicates very good agreement with theoretical predictions.

Cascade synthesis of polylithic crystal filters containing double-resonator monolithic crystal filter (MCF) elements

Abstract: In crystal filter design the use of low-pass prototype networks containing frequency invariant reactances is well known. It is shown in this paper that if this concept is extended to the double-resonator monolithic crystal filter (MCF) section, then all the classical transmission zero producing networks, e.g., the Brune, Darlington C-type, and Darlington D-type, may be realized in a form containing low-pass prototype MCF sections. This result allows the techniques of reciprocal cascade synthesis to be applied to the direct synthesis of arbitrary lossless even degree transfer functions in crystal filter form. Explicit expressions are given by which the prototype MCF element values may be obtained

Measure-predict tuning of hybrid thin-film filters

Abstract: To achieve highly accurate filter characteristics in hybrid integrated active filter circuits, a new tuning procedure for Sallen-andKey-type hybrid filters has been developed and implemented. The proposed tuning procedure takes into account the loss factor of thin-film capacitors and nonideal amplifiers. An example that describes the tuning procedure in detail is presented for a second-order low-pass filter. It is also applicable in the same manner to all second-order functions. The new tuning procedure replaces a previous approach that was iterative and therefore time consuming when high precision was required. The new approach guarantees the pole frequency to within 0.2 percent in one tuning step, and the pole Q to within I percent in an additional step. The tuning procedure requires that the capacitors be measured to within 0.1 percent, the dissipation factor to within 10 percent, and the resistors to within 0.02 percent. With the aid of a computer, the procedure has been completely automated; it is therefore well suited for processing in manufacture. It is being used in on-line production of thin-film active filters.

Turbine-generator protection system with electronic sampling filter

Abstract: A system for protecting a turbine-generator power plant governed by signals representative of turbine mechanical power and generator electrical power to reduce at times the turbine mechanical power, with an electronic filter included therein for the purposes of filtering a periodic time varying component of the electrical power signal having a response time within adequate protective limits, is disclosed. More specifically, the electronic filter generates a train of fixed time durations wherein during each fixed time duration the maximum and minimum amplitudes of the electrical power signal are selected. A signal is sampled at the end of each fixed time duration and held constant for each next fixed time duration, said signal being representative of the average of the maximum and minimum amplitudes selected during each fixed time duration. In employing these sampled filter techniques, the electronic filer can respond to electrical power signal disturbances with a response time approximately equal to one fixed time duration while generating a sampled average signal of the electrical power signal free of the time varying component.

A Torsional-Mode Pole-Type Mechanical Channel Filter

Abstract: A torsional-mode pole-type mechanical filter is studied, with the aim of further miniaturization and economy of channel translating equipment. New torsional-mode transducers have been developed. These are built of piezoelectric ceramics disks with a high coupling constant k1.j and of bars of a constant elastic modulus alloy. As the capacitance ratio of the transducer is about 9-1 l, the filter does not need inductors to compensate for the clamped capacitance of the transducers. The distances between the resonators are adequately determined, therefore, the couplers are constructed of only few types of single straight wire lines. Finite attenuation poles are produced by two oblique bridging wires. In the passband region, the attenuation ripples of the filter fulfill the desired specification (CCITT 1/20) over the temperature range of 5°C to 45°C. Delay distortion and minimum group delay time are nearly equal to that of the LC channel filter being used in Japan. The filter contains 7 torsional-mode resonators and 2 torsional- mode transducers. The filter volume is about 5.3 cm3 and its weight is 13 g. These values are about 1/10 those of the LC channel filter.

Frequency shift modulated data transmission presence detector - has improved efficiency by replacing limiter noise with constant frequency

Abstract: Digital or sampled data is transmitted by frequency shift modulation of a carrier frequency. Limiter noise is replaced by a signal which does not affect the signal demodulator output and which is obtained by adding part of the received signal to a constant frequency. This improves efficiency of a presence detector. A receiver produces signals at an IF which is coupled to an adding circuit which also receives a constant frequency signal. A limiter is followed by filter circuits and detectors at the inputs to a comparator to obtain binary output signals. A presence detector comprises a rectifier circuit with a comparator to which a threshold level signal is applied. This level is adjusted as required for recognition of signal presence.

Realisation of active-R filters using amplifier pole

Abstract: A systematic-realisation technique of the 2nd-order active-R filter using an inherent amplifier pole is proposed. To realise such a filter it is shown that two operational amplifiers and three resistors are sufficient. Workede examples are given. The resultant filters are found to be suitable for high-frequency low-Q-factor applications.

Intermediate-band crystal filter with low-transient response

Abstract: An intermediate-band, low-transient crystal filter utilizing standard components. The filter is characterized by improved response and temperature stability and a size which is smaller than presently used LC filters, helical filters and wide-band crystal filters. This is achieved by an unusual partitioning of a low-pass prototype ladder network which yields a cascade of symmetric lattice sections and, hence, a realizable crystal filter. The cascade is composed of only two fundamental sections.

DC flow converter with setting elements with common output - has parallel power ccts. each of setting transistors, transformer, and filter cct

Abstract: The direct current flow converter has at least two pulse width controlled setting elements operating to a common output Parallel power circuits are formed each by a setting transistor, a transformer, and a filter circuit These circuits are uniformly loaded by the control of current division in the setting elements after comparison of a measuring criterion, tapped from all power components Preferably the mean value of the voltage pulses at the input of the filter circuits forms the measuring criterion for the control of the current division A common storage capacitor may be associated with all parallel power circuits One of these parallel circuits may be controlled via a regulating amplifier in dependence on the control deviation of the output voltage, while the other power circuits may be controlled each by a current division regulator

A.S.W. filter bank using a multistrip reflective array

Abstract: A new frequency-sensitive a.s.w. structure is presented. The device, operating by reflection of acoustic surface waves, is used as a filter bank.

The influence of non-linearity in active filters

Abstract: The influence of amplifier non-linearity on the transfer characteristic of active band-pass filters is investigated. An expression is derived for the amplitude transfer of signals at resonance frequency. Calculations are verified by experimental results.

Error compensation in sync. detector amplifier - alternatively switches signal to be detected between filtering and amplifying circuits

Abstract: The synchronous detector error compensation method sends alternatively the signal to be detected into two amplifying and filter circuits. The signal is sent to the two circuits via two gates which are controlled in phase opposition by a synchronising signal. At a frequency f1 the connection between the two amplification circuits is switched with the outputs of each of the two gates. Also at the frequency f1 the connection of the outputs of the two amplification circuits if switched with an output terminal. At this terminal can be observed the continuous synchronous detected signal resulting from the difference of the signals routed via the two gates. At the frequency f1 the correction of the gate controls are transposed by the synchronising signal and the outputs of the two gates connected to the inputs of the filtering and amplifying circuits.