Showing papers on "Electronic filter published in 1975"

New Active Filter synthesis based on Scattering Parameters

Abstract: Inductorless active filters which are derived from double terminated classical reactance filters, such as gyrator-capacitor filters and filters using the FDNR concept, are known to exhibit low sensitivity. Stimulated by the ideas underlying the method of wave digital filters the attempt has been made to establish a concept for the synthesis of active filters which is based on processing of wave quantities. In this paper the method leading to this new kind of active filters is presented and possibilities for practical implementation are shown. Some experimental results confirm the feasibility of the principle.

Low-sensitivity high-frequency tunable active filter without external capacitors

Abstract: An active filter is discussed which uses only resistors and two operational amplifiers represented by their single-pole model, but no external capacitors. The filter has very low sensitivities to all circuit parameters, is tunable over exceptionally wide frequency ranges, and is suitable for high-frequency and medium- Q applications. The usable frequency range is limited only by the validity of the single-pole model of the amplifiers used. The circuit may be used both as a lowpass and as a bandpass. Extensive room-temperature experimental results are presented.

A practical design for insensitive RC-active filters

Abstract: A systematic RC -active network synthesis procedure for the realization of second-order transfer functions is proposed. The realization employs three operational amplifiers and no isolation amplifiers are necessary. The sensitivity of the resulting networks to passive element variations has been found to be low. The sensitivity to variations in the active elements has been made very low. A design is given in which tuning can be achieved by trimming only resistors. The design is particularly attractive for high- Q realizations. The stability properties and the influence of the finite bandwidth of the amplifiers are examined. The proposed realization has been compared with those of Kerwin, Huelsman, and Newcomb, of Tarmi and Ghausi, and of Thomas, and found to offer several attractive features as compared to these realizations. The design procedure was used to obtain a sixth-order elliptic bandpass filter. Experimental results show close agreement between theory and practice. Further, these results indicate that these realizations are insensitive to temperature and power supply variations.

Design and evaluation of shifted-companion-form active filters

Abstract: Two techniques for designing a class of low-sensitivity, follow-the-leader, feedback-type active filters have been introduced by Hurtig and Laker-Ghausi. The FLF configuration consists of a cascade of second-and/or first-order sections, with feedback from each section back to the first. This paper presents an approach for designing FLF-type realization for all classes of filter functions. The technique is based on a shifted-companion form of the associated-state equations. Some salient features of Hurtig's primary resonator block, Laker-Ghausi's follow-the-leader feedback, and the shifted-companion-form techniques are presented below. (i) Hurtig's PRB realizes any all-pole (no finite transmission zeros) filter function. This includes the low-pass, high-pass, and symmetrical bandpass filters without finite zeros. Explicit design equations are available, and the individual sections in the array are identical. (ii) Laker-Ghausi's FLF realizes any symmetrical (including finite transmission zeros) bandpass filter function. The sections are not constrained to be identical, which allows optimization using this degree of freedom. Finite zeros are realized by a summation technique. (iii) The SCF realizes all types of filter functions, i.e., low-pass, high-pass, bandpass, all-pass, or band-reject filters. Explicit design equations are available. The first section can differ from the rest, thus allowing some optimization with standardization. Feed-forward as well as summation techniques can be used to realise the finite zeros. Two bandpass design examples using SCF, PRB, and/or Laker-Ghausi FLF techniques are given and compared with the low-sensitivity coupled (leapfrog) biquad, the conventional cascade biquad, and the passive ladder filter designs. The comparison shows that the passive filter gives

A novel second-order canonical RC-active realization of high-pass notch filter

Abstract: A high-pass notch filter with variable gain greater than unity is realized using a differential amplifier and only two capacitors that can be equal. The transmission zero and pole frequency are completely independent of the amplifier dc gain. Design formulas, sensitivity analysis, and measure and trim tuning process are presented. An example of a 60-Hz rejection filter is discussed, the response of which is within the required specifications even with a \pm 5-percent capacitance variation. Two modifications of the original structure can be used to realize the same filter, extending the available range of the gain to cover all requirements.

Single amplifier functionally tunable low-pass-notch filter

Abstract: The canonical network developed in this paper is an active RC negative feedback arrangement that uses a single op-amp and two capacitors to realize low-pass-notch filter characteristics. The filter parameters are adjustable through resistive trimming. This functional tuning process uses a signal generator, a dB-scale voltmeter and a phase meter. The analytical design procedure takes into account a single-pole amplifier model. The network has low-passive sensitivities and is suitable for moderate- Q applications ( Q \leq 5 ). An example is discussed giving the resistor's limits for a \pm 10 percent capacitance tolerance.

A reprogrammable filter bank using CCD discrete analog signal processing

Abstract: A multichannel filter using a 32-stage CCD analog shift register (ASR), will be described. The filter uses a recursive two-pole, one-zero network. The center frequencies, bandwidths and gains, are independently programmed using four quadrant multiplying digital-to-analog converters.

SAW Filter Sampling Techniques

Abstract: Surface acoustic wave filters are designed to r lize A. IXTRODUCTION the impulse response which corresponds to the passband specifications. In the past SAW transducers have been realized by identifying ESIGNS of SAW filters are typically determined by one line of an interdigital transducer with one half cycle of the speccalculating the theoretical impulse response for the ified impulse response. This Paper Pr'JPoses breaking from that conrequired passband and the11 identifying one interdigital cept and identifying each transducer element with a sample and varying the sample rate to best meet the fdter performance retransducer line for each half cycle in the impulse response transducer structure designed to accommodate the new concept are about the center frequency the resulting apodized transdescribed. ducers will have nonuniform line spacing, which is un1973. This work was supported in part by the Joint Services ElecThe technique described in this paper uses the calculated tronics Program (U. S. Army, U. S. Navy, U. S. Air Force1 under impulse response sampled a t various rates as t,he basis for Contract DAAB-07-72-C-0259. 13. J. Hunsinger is with the Coordinated Science Laboratory, generating the transducer design. The individual elemCntS University of Illinois, Urbana, 111. 61801. R. J. Kansy is with the Magnavox Company, Fort Wayne, Ind. of the multitap t,ransducer are each identified with one 46804. sample instead of with one half cycle of the impulse reD qkements. Four sampling variations and a modified interdigital Cl]. If the rewired frecluency response is not SYlnnIetrical Manuscript received November 4, 1974; revised February 19, desirable in some applications. HUNSINQER AND KANSY: SAW FILTER SAMPLING 271 Fig. 1. Oversam image responses. sponse. The resulting transducer has uniformly spaced element’s located a t a separation less than one half the center frequency wavelength. B. SAMPLED IMPULSE RESPOSSE SPECTRAL CHARACTERISTICS SAW filters with specified passbands are realized by designing transducers to generate the corresponding sampled impulse response (In) . Sampling the impulse response produces additional image frequency components dependent on the sampling rate. The time sampled frequency response H , ( W ) is the convolubion of the unsampled direct frequency response H ( W ) and the sanlpled frequency

Audio frequency power line control system

Abstract: An audio frequency power line carrier control system utilizing an inverter as the carrier control transmitter with the output phase voltages of the inverter fed to a distribution network through a series inductance, a filter circuit and a current transformer in which a starting control is provided which modulates the audio frequency pulses at the beginning of clock pulses for transmitting data using a control signal which is pulse width modulated, modulation being terminated when the pulse width of the control pulse width falls below a predetermined minimum duration thereby permitting small series inductances to be used.

Vertical deflection circuit

Abstract: This invention relates to improvements in a vertical deflection circuit employing a class D amplifier. The circuit comprises a pulse width modulator for converting a sawtooth waveform signal to a width modulated pulse train, a switch mode power amplifier for amplifying said width modulated pulse train, a demodulating filter circuit for demodulating said width modulated pulse train to the sawtooth waveform, a damping circuit for preventing a significant power loss in said demodulating filter circuit and a deflection yoke coupled to said demodulating filter circuit, thereby making it possible to reduce power dissipation in the circuit.

Controllable bandwidth IF filter circuit for radio receivers

Abstract: Controllable bandwidth IF filter circuit for radio receivers generally, but having particular application to quadraphonic radio receivers intended for use in a quadraphonic system that is compatible with existing monophonic and biphonic equipment, said filter circuit being automatically adjusted in a digital manner to exhibit one of several different bandwidths in response to a pair of transmitted control signals present in the quadraphonic transmission so as to provide optimum receiver operation for the particular mode of broadcast being received, especially in terms of an improved protection ratio and signal to noise ratio for the received signal. The noted bandwidth adjustments are accomplished by modifying the values for certain of the component in the filter's tuned circuit and coupling sections through their selective connection into the circuit by means of semiconductor switching devices operated in response to said pair of control signals.

Compensating circuit for use with filters - is used in phase shift keyed demodulators and uses phase sensitive detector to control VCO coupled to mixing circuit

Abstract: A filter circuit for use in a phase shift keyed demodulator and operating with a small band width is coupled to a compensating circuit to provide automatic control of the frequency. The filter circuit consists of two filters (12, 14) coupled in parallel over input and output switching circuits (10, 16). The switching circuits are operated with a square wave input signal of a constant mark/space ratio of 1:1. The input is multiplied (20) and is mixed with the output of a voltage controlled oscillator (VCO). The VCO generates an output proportional to the output of a phase sensitive detector (PSD) operating on the input to the filter and the output after passing through a limiting stage (28).

Fail-safe active band-pass filter

Abstract: This disclosure relates to an improved fail-safe electronic filter circuit including a common-emitter transistor amplifier having a feedback path. The feedback path includes an R-C twin-T network which is imperfectly nulled to only provide regeneration at a preselected frequency. An emitter-follower circuit operates to isolate the series resistance branch of the R-C twin-T network from the collector of the transistor amplifier so that an output signal is only available during the presence of a signal having the preselected frequency and in the absence of a critical component or circuit failure.

Saw Filters for TV Receivers

Abstract: The surface acoustic wave (SAW) technology has existed in many laboratories for a number of years. It has already found a place in many military and professional systems. Perhaps its most successful application to date has been in providing pulse compression filters for chirp radar. Recently, however, SAW bandpass filter design has reached the state where a single device can perform all the filtering necessary in the I.F. stage of colour T.V. receivers. The added advantages of the SAW solution over traditional LC methods are immediately obvious. No manual alignment is necessary. The SAW filter is compact, rugged and reproducible.

Electronic filter circuit

Abstract: To eliminate the high frequency portion of an input signal while permitting low frequency and DC portions to pass, the electronic filter utilizes an n-1 order active network in combination with a capacitor to generate a shunt current, thereby providing a low pass filter having n-order operating characteristics. Included in the active network is an active element, such as an operational amplifier, which responds to an input signal by creating a voltage across the capacitor, resulting in a shunt current that in turn provides the desired filter characteristics. In certain special cases the n-order active filter can utilize a differentiating element in combination with n-2 order active network along with the capacitor to achieve n-order operating characteristics.

Quartz crystal compensation circuit

Abstract: A compensation circuit is provided for a piezo-electric quartz crystal in a filter circuit for reducing the influence of the secondary resonance frequencies of the crystal on the filter characteristic. The Q-value of the crystal at one or several secondary resonance frequencies is reduced by connecting to the crystal a two-terminal network the impedance of which has a real and an imaginary part so that the real part gives an ohmic contribution which at the resonance frequency of the imaginary part reduces the Q-value of the crystal.

Computer-aided optimal synthesis of bandpass filters

Abstract: A method is developed for the computer-aided synthesis of a particular case of linear, lumped, passive, bilateral, lossless bandpass ladder filters. It involves the numerical values of the open-circuit immittance functions in three sets of equations referred to as the terminal, the remainder, and the junction algorithms. The filter model comprises two chains of LC sections, each of which contains one arbitrary component value and a finite frequency rejection circuit. The response of this model is exact, save for roundoff errors. The possibility of placing boundary values on all component values is then investigated through a systematic permutation of all finite frequency rejection circuits and by varying all arbitrary component values in a programmable number of steps. The process is applied to the example case design of a 70-MHz 14th-order filter.

A tunable filter using amplifier pole

Abstract: A circuit consisting of two periodically operated switches, potentiometers, resistors, and compensated operational amplifiers, but not containing external capacitors, is proposed for the realization of a second-order bandpass and low-pass filter. The filter is electronically tunable and the natural frequency of the filter varies linearly with the width of the pulses controlling the FET switches.

Active filters: Some simple design methods for biomedical workers

Abstract: Some simple techniques for designing electronic filter circuits are described. Filters that use inexpensive, readily available components are suitable for reducing the noise in a range of biological signals

Applications of charge-coupled device transversal filters to communication

Abstract: The paper discusses the computational power of state-of-the-art charged-coupled device (CCD) transversal filters in communications applications. Some of the performance limitations of CCD transversal filters are discussed, with attention given to time delay and bandwidth, imperfect charge transfer efficiency, weighting coefficient error, noise, and linearity. The application of CCD transversal filters to matched filtering, spectral filtering, and Fourier analysis is examined. Techniques for making programmable transversal filters are briefly outlined.

Electromechanical measuring transformer - esp for path-voltage conversion, has data pick-up and half bridge of two inductances

Abstract: A rectifier and filter circuit (7, 11), converts the alternating voltage at the inductances into a direct voltage and a potential divider is connected via the rectifier circuit in parallel with the inductances and contains two ohmic resistances. The output signal is the potential difference between the junction point of the inductances and the potential divider tap. In addition to the rectifier circuit and between the two resistances of the potential divider (8, 10) there is connected a diode (9) with polarity in the direction of the current flowing through the resistances. Connected in parallel with this diode is the series connection of two more ohmic resistances.

A realization of high-Q insensitive RC active filters using all-pass networks

Abstract: The paper describes an approach for realizing high-Q, insensitive RC active filters. The network is shown to have extremely low sensitivity to variation in active and passive parameters. The interesting feature of the network is that the filter can be tuned to any desired resonant frequency without affecting the pole-Q. The filters are shown to have minimum dependence on the bandwidth of the operational amplifiers, and are thus capable of operating over a wide range of frequencies with relatively stable Q and resonant frequency.