Showing papers on "Electronic filter published in 1968"

Power system filter

Abstract: A harmonic filter for an AC power system, particularly for converter installations, which provides damping to diminish the effects of parallel resonance. The filter consists of a plurality of conventional LC shunt filters tuned to the expected harmonic frequencies. The power system may also include static capacitors for power factor correction. Since the power factor capacitors and the harmonic filters are effectively in parallel with the inherent inductance of the AC system, a parallel resonance, which may occur at one of the lower harmonic frequencies, results. In order to reduce the effects of a parallel resonance, there is provided an additional filter tuned to provide damping at the harmonic frequency at which parallel resonance may occur. This additional filter comprises an LC filter with a resistor connected in parallel with the inductance. This resistor is connected to a blocking filter which presents a high impedance to the system fundamental frequency. The effect of this resistor is to provide damping which will reduce the amplitude of oscillations under parallel resonant conditions. Since this resistor is connected through a blocking filter, it provides damping without providing excessive additional loading at the fundamental frequency.

Electrical filter arrangement

Abstract: This invention relates to a highly selective electrical filter network composed of passive circuit elements and capable of attenuating or ''''notching'''' only selected frequencies from a band while freely passing without substantial attenuation the remaining frequencies in the band. Such a filter network comprises a plurality of series and parallel LC resonant networks or stages alternately disposed in circuit relationship with one another and designed to resonate at the ''''notching'''' frequency. The stages are interconnected by means of suitable matching transformers to permit the optimum use of the inherent Q of each inductor.

Low-pass active filter

Abstract: A LOW-PASS FILTER EMPLOYS AN ACTIVE FILTER PRECEDED BY A PASSIVE FILTER, THE ACTIVE FILTER BEING AC COUPLED IN SHUNT WITH THE PASSIVE FILTER THE PASSIVE FILTER CARRIES MOST OF THE CURRENT, THUS REDUCING THE CURRENT SUPPLIED TO THE ACTIVE FILTER AND PERMITTING THE COMPONENTS OF THE ACTIVE FILTER TO BE OF SMALLER SIZE

Direct-coupled resonator filters with improved selectivity

Abstract: A method is outlined whereby a narrow-band direct-coupled resonator filter may be derived from an elliptic-function low-pass prototype. The construction and performance of a three-resonator waveguide cavity filter designed on this basis is described.

Organizing a special-purpose computer to realize digital filters for sampled-data systems

Abstract: A special-purpose computer is organized to implement a programmable digital filter intended for use in sampled-data control systems. A canonical representation for the digital filter is selected and this form is implemented in functional blocks that are suitable for circuit integration. An analytical technique is discussed that helps determine acceptable quantization resolutions and round-off errors in the digital filter. Experimentation with the digital filter is performed in the pendulous integrating gyroscopic accelerometer control loop and in an analog computer simulation of the Saturn V thrust vector control system; the filter used as a digital compensator successfully stabilizes both sampled-data control systems. The performance of the digital filter is examined and organizational techniques to improve its characteristics are proposed.

Equal-resonator piezoelectric ladder filters

Abstract: Piezoelectric ladder filters with the following characteristics are described: A. The filter selectivity may be changed without changing the resonators and without requiring the frequencies of peak insertion loss to be changed. This type of filter will be referred to as ''''equal-resonator filter.'''' B. Except for the restrictions on the series resonant frequency of the shunt resonators and the anti-resonant frequency of the series resonators, the remaining resonator parameters are largely, within a range that will be explained, independent of the filter selectivity. This permits use of predetermined resonators for the design of filters with different selectivity characteristics. It includes filters where all the series resonators and all shunt resonators, respectively, are equal, as well as filters in which all the resonators are identical with each other. The latter type will be called ''''identical resonator'''' filters.

Phase-compensation in electronic gyrator circuits

Abstract: A method is indicated for frequency-independent compensation of the internal phase shift in electronic gyrator circuits intended for inductance simulation. Application of the compensation technique to filter circuits is also indicated.

Birefringent Filter for Millimeter Waves

Abstract: A scale model (f/sub 0/ =20 GH/sub z/ of a Solc-type birefringent wave filter for millimeter wavelengths is described. The filter consists of five cascaded identical half-wave plates, or crystals, each composed of an artificial anisotropic dielectric medium with its reference axis tilted at some prescribed angle to the plane of the input polarization. The design and analysis of an individual plate, using Collin's second-order theory of the birefringence of artificial anisotropic dielectrics, and the analysis of multielement filters (filters composed of many plates), aided by Evans' matrix method, are discussed. The experimental filter was tested in the range of 18 to 33 GHz, and its measured performance was found to compare well with the theoretical performance over a major portion of the range of frequencies used in the tests. A synthesis procedure for optimum (equal-ripple stopband) response multielement filters is given, together with tables of plate angles for such filters. In this procedure, the Dolph approximation and the Harris synthesis are combined.

Analog network based on sampling for universal applications filter

Abstract: THE PRESENT FILTER FOR FILTERING ANALOG SIGNALS IS BASED ON THE USE OF ANALOG NETWORKS IN WHICH THE SIGNALS ARE INTEGRATED OVER TIME SO AS TO SELECT OUT A DESIRED FREQUENCY RANGE, AND IS CHARACTERIZED BY MEANS FOR INTEGRATING THE SIGNALS ONLY OVER SEPARATE TIME INTERVALS, THE MUTUAL TIME SPACING OF WHICH IS SHORTER THAN THE PERIOD OF THE SIGNALS IN SAID DESIRED FREQUENCY RANGE. IN THE CASE OF AN ELECTRICAL FILTER CIRCUIT COMPRISING AT LEAST ONE CAPACITOR THERE IS PROVIDED A SWITCHING ELEMENT EFFECTIVELY IN SERIES WITH EACH CAPACITOR, SAID SWITCHING ELEMENT BEING CLOSED DURING SAID SEPARATE TIME INTERVALS.

Differential spectral absorption analyser

Abstract: 1,237,547. Spectral analysis. STANDARD TELEPHONES & CABLES Ltd. Aug. 7, 1968, No. 37638/ 68. Heading G1A. [Also in Divisions G2 and H4] In a differential spectral absorption analyser a rotatable filter wheel, Fig. 2, is located together with a test sample, in the optical path from a radiation source to a photo-detector, and provides both an overall intensity modulation of the beam at a frequency f 2 and also a modulation of each of two particular wavelengths contained in the beam at a frequency f 1 , the photo-detector output component of frequency f 1 providing the analyser output while the f 2 component (f 2 > 2f1) is fed back to an amplifier associated with the detector to provide automatic gain control to eliminate source or detector fluctuations. The filter wheel comprises a plurality of equiangularly spaced filters, alternate ones of which form a first set having a different pass band from the second set. The filters 9, for example, will have a pass-band chosen to match a strong absorption band of the substance whose concentration is being measured, while the other filter set will have a pass-band located where the substance is transparent. Thus, presence of the substance in the optical path will result in the modulation of frequency f 1 . The overall intensity modulation at a frequency f 2 is provided by ruled lines 10. After amplification (2) and removal of the f 2 component (3, 6) the f 1 component is supplied to a synchronous detector (7) controlled by pulses generated from the filter wheel drive motor. The synchronized output is displayed on a meter which may also include means for indicating failure of the light source. A separate filter circuit (4) is provided in the feedback path to suppress the f 1 component. To measure the concentration of a specific vapour the two wavelengths are usually chosen in the infrared region.

Steady-state simulation of h.v. d.c. convertors by digital computers

Abstract: The paper introduces and develops a digital-computer technique for the steady-state simulation of h.v. d.c. convertors incorporating capacitive networks, such as filter circuits, damping circuits etc. The method involves the simulation of a single process of 60° starting from a valve firing, and, assuming steady-state and symmetrical operation, the relating of the conditions at the end of the 60° process to those at the beginning of the process. Since the system of differential equations constitutes a boundary-value problem, a digital solution is achieved by a finite-difference method which offers a most economical approach in computing time. The possibility of solution by iterative methods is also discussed. In the test network, including filter circuits, the a.c. system is taken to be inductive, but the method presented in the paper is suitable for further extensions in the network included. The simulation offers a facility for obtaining current and voltage waveforms in various circuit elements without excessive computing time, and could be useful in the design of filter circuits and damping circuits, in the assessment of convertor regulation and in checking the validity of simplified networks for the solution of steady-state convertor problems.

Improvements in or relating to electrical filter devices

Abstract: 1,210,181 Measuring displacement electrically RANK ORGANISATION Ltd April 9, 1969 [April 10, 1968], No 17260/68 Heading GiN A profile testing system comprises a transducer T which is rotated around the profile W to be examined and a high pass filter system F, B which selects harmonics of the signal generated by the transducer, the harmonics selected depending on the true shape of the profile If the true profile is circular, filter F passes only the DC component and the fundamental of the signal which is subtracted at B from the complete signal to yield only the harmonics The output from B is fed to meters M and also to a plotter P, CR which plots the profile A mean radius signal may also be fed to the plotter to trace the true shape Suitable filters giving an impulse response which follows a predetermined low are described (see Division H3)

Low pass active filter

Abstract: A filter circuit for connection between a direct current power supply and a load which has incorporated in the series line running between the input and output terminals of the filter circuit a network that presents a high impedance to alternating current components that appear at either end of the filter, such network presenting relatively small resistance to direct current load currents that flow through the filter. The network shown has a transister with its emitter and collector elements connected in the filter series line, and the base element of the transistor is connected to (i) a bias resistor that has its opposite end joined through a diode with the transistor collector, and (ii) a smoothing capacitor that has its opposite side joined with the transistor emitter.

Improved apparatus for weighing vehicles in motion

Abstract: 1,123,356. Measuring weight of moving vehicles electrically. W. & T. AVERY Ltd. Nov.9, 1965 [Nov. 21, 1964], No.47486/64. Heading G1N. To obtain the static weight of a moving vehicle 1 (Fig. 2) its weight is sensed by load cells 4 (strain gauges on a D.C. bridge) supporting a rail section 3 over which the vehicle passes and the initial peak value of the load cells' output voltage (Curve A Fig. 1) is sensed and therefrom is formed an estimate of the static weight. It's assumed that the ratio of the peak value of curve A to the correct static load weight (voltage level B Fig. 1) would be constant at approximately 3:2. The cell output is fed via a filter inductance Z 1 to charge a capacitor Z 2 of the filter circuit. The response of the filter to the wave form A is illustrated by curve D. To enable the filter output to approach the correct weight level B more rapidly, so that in a time T, before the first set of wheels pass from the rail 3, it will be close to the correct weight value, the capacitor Z 2 is pre-charged rapidly to a point B on a curve E, and approximating the correct weight value during a period, determined by a pulse operated transistor switch circuit 11, immediately following the peak of curve A. When the switch circuit 11 is closed in response to the arrival of the leading wheels on to the section 3, the capacitor Z 2 is precharged from a short time constant circuit including an attenuator 8 and a peak detector and peak storage circuit 7, and via Z 1 from the load cell output. The transistor switch 11 then opens terminating the pre-charge and the strain gauge bridge output operates to charge the capacitor Z 2 via Z 1 only, substantially to the voltage level B at the time T. The voltage across capacitor Z 2 at the instant T is representative of the weight carried by the vehicle wheels which are passing over the rail section 3, and may operate an indicator or recorder. A time delay circuit (28) Fig. 3 (not shown), may be used to generate a pulse which disconnects the filter circuit from the load cells just before the moving load leaves the weight section 3 and which connects the filter output Z 2 voltage to an indicator.

Electrical filter circuit

Abstract: An electrical filter comprises an amplifier with a pair of pushpull terminals on its input and/or output side. A frequencyselective network forms a negative feedback from the output to the input of the amplifier. A bridge circuit constituted by circuit components of the network as well as by the pair of pushpull terminals, has branches whose respective reactive impedances differ from one another as regards their dependence upon frequency so as to conjointly define a pair of null points for the damping function of the transmitting attenuation of the filter.