Showing papers on "Electrical impedance published in 1975"

Asymmetric Coupled Transmission Lines in an Inhomogeneous Medium

Abstract: Terminal characteristic parameters for a uniform coupled-line four-port for the general case of an asymmetric, inhomogeneous system are derived in this paper. The parameters (impedance, admittance, etc.) are derived in terms of two independent modes that propagate in two uniformly coupled propagating systems. The four-port parameters derived are of the same form as those obtained for the symmetric case resulting in similar port equivalent circuits for various circuit configurations considered by Zysman and Johnson. The results obtained should be quite useful in designing asymmetric coupled-line circuits in an inhomogeneous medium for various known applications.

Voltage clamping with a single microelectrode.

Abstract: A technique is described which allows neurons to be voltage clamped with a single microelectrode, and the advantages of this circuit with respect to conventional bridge techniques are discussed. In this circuit, the single microelectrode is rapidly switched from a current passing to a recording mode. The circuitry consists of: (1) an electronic switch; (2) a high impedance, ultralow input capacity amplifier; (3) a sample-and-hold module; (4) conventional voltage clamping circuitry. The closed electronic switch allows current to flow through the electrode. The switch then opens, and the electrode is in a recording mode. The low input capacity of the preamplifier allows the artifact from the current pulse to rapidly abate, after which time the circuit samples the membrane potential. This cycle is repeated at rates up to 10 kHz. The voltage clamping amplifier senses the output of the sample-and-hold module and adjusts the current pulse amplitude to maintain the desired membrane potential. The system was evaluated in Aplysia neurons by inserting two microelectrodes into a cell. One electrode was used to clamp the cell and the other to independently monitor membrane potential at a remote location in the soma.

Method for determining battery state of charge by measuring A.C. electrical phase angle change

Abstract: Several embodiments for determining the state of charge of a cell or battery are disclosed. In accordance with one method of this invention, an A.C. voltage is applied to a cell or battery through a shunt. The phase angle between the A.C. voltage across the battery terminals and the A.C. current through the battery (measured as a shunt voltage) is continuously monitored. This phase angle is converted to an analog voltage which represents the A.C. component that is phase shifted by the impedance of the battery. The impedance and thus the phase angle changes with the state of charge of the battery. The analog voltage can be coupled to a meter that provides a phase angle reading or a state of charge reading. Further, the analog voltage can be used to control charge and discharge circuitry. In accordance with a second method, the state of charge of a battery is determined by taking phase angle readings based on input and output A.C. voltages.

Distribution network power line communication system

Abstract: A distribution network power line communication system which includes coupling means for applying a carrier current communication signal to the polyphase primary distribution conductors with a proportional relationship between the signal voltages applied to the various conductors selected to provide a predetermined propagation mode. Impedance elements are connected between the conductors at selected points remote from the coupling point, such as at the location of unbalanced loads, line taps, branches, capacitor banks, distribution transformers, and other line discontinuities which may cause mode conversion. The impedance elements are selected and connected to re-establish the predetermined propagation mode.

Mutual impedance of nonplanar-skew sinusoidal dipoles

Abstract: The mutual impedance of nonplanar-skew sinusoidal dipoles is presented rigorously as a summation of several exponential integrals with complex arguments.

The Equivalent Circuit of Some Microstrip Discontinuities

Abstract: The experimental characterization of some microstrip structures of common interest, including symmetrical T junctions, is described. Some results are compared with data derived from recent three-dimensiotial static theory and from the uniform plane-wave model. It is concluded that while the three-dimensional theory requires further improvement, it is generally in much better agreement with the measured data than the two-dimensional uniform plane-wave model.

A Technique for Determining the Local Oscillator Waveforms in a Microwave Mixer (Short Papers)

Abstract: A technique is described which enables the large-signal current and voltage waveforms to be determined for a mixer diode. This technique is applicable to any configuration where the impedance seen by the diode at the local oscillator (LO) frequency and its harmonics is known.

Noise in single injection diodes. I. A survey of methods

Abstract: A critical discussion is given of existing methods for the computation of noise in single injection space−charge−limited (SCL) devices: the salami method, the Langevin method, and the impedance field method. In addition, a new method is set forth, which in one form (finite volume divisions Δ3r) presents a lumped network description of noise and electrical parameters, whereas in another form (Δ3r→0) it presents a continuous media transport picture which is characterized by a transfer impedance tensor. The first form ties in with a modified salami method, whereas the second form is the substratum from which the more global impedance field formulas can be derived. A necessary and sufficient condition under which the noise is expressible as generalized Nyquist noise is obtained. For the simplest device, the thermal electron trap−free insulator, this is applied to one−dimensional as well as some three−dimensional geometries.

Computation of Coplanar-Type Strip-Line Characteristics by Relaxation Method and its Application to Microwave Circuits

Abstract: The characteristics of new strip lines [i.e., a single strip-conductor coplanar-type strip line (S-CPS), a two symmetrical strip-conductor coplanar-type strip line (T-CPS), and a coupled strip-conductor coplanar-type strip line (C-CPS), which consists of single two-center strip conductors or coupled strip conductors and ground plates on a dielectric substrate and outer ground conductor] are calculated by the relaxation method. The effect of the outer ground conductor and side wall on these lines is analyzed and the characteristic impedance and phase-velocity ratio are determined. The characteristic impedance is determined experimentally and the maximum values of the discrepancies compared with the calculated value of each of the lines are 2.0-3.0 percent. Application examples of the coplanar-type strip line to microwave transistor amplifier and parallel-coupled filter are shown. A transistor amplifier of small size, light weight, wide bandwidth, and improved reliability is achieved. A parallel-coupled filter small in size (reduction ratio is more than 50 percent), with good frequency symmetry and featuring easy resonance frequency fine tuning is obtained.

Spectral-Domain Calculation of Microstrip Characteristic Impedance

Abstract: This paper presents a hybrid-mode solution for the characteristic impedance of microstrip on Iossless dielectric substrate. A solution to the hybrid-mode equations is obtained by applying the method of moments in the Fourier transform domain. Numerical results are presented showing the frequency dependence of both wavelength and characteristic impedance for single and coupled strips. These results are compared with those of other investigators in the low-frequency range.

Automatic matching method and apparatus

Abstract: A high-Q load circuit is matched to a drive circuit with an L-type filter network including series and shunt reactances which are both either inductive or capacitive. While a first of the reactances is effectively removed from the network, the value of the second of the reactances is varied until the impedance magnitude of the load and network, as seen from the drive circuit, reaches a predetermined magnitude, and a predetermined relationship exists for the polarity of the phase of the voltage and current supplied by the drive circuit to the network. When the impedance magnitude seen by looking from the drive circuit into the network reaches the predetermined magnitude and the correct phase polarity exists, the first reactance is reconnected into the network and then varied until a predetermined relationship exists between the phase angle between the voltage and current applied by the drive circuit to the network.

Adjustable length center conductor for termination fixtures for electrodeless lamps

Abstract: A light source includes a source of high frequency power, an electrodelsss lamp and a termination fixture for coupling power to the lamp, the fixture having an outer conductor and an inner conductor whose length is adjustable for providing dynamic matching of the impedance of the lamp during the operating mode to the output impedance of the source. Variations in the power level from the source, such as is desirable in providing lamp brightness selectivity, vary both the real and imaginary components of the lamp impedance, and corresponding adjustments of the inner conductor length provide a tuning technique to compensate for these variations.

Fourier-series techniques applied to distance protection

Abstract: For distance-relay applications, the fundamental system impedance as seen from the relaying point is used as the basis for the decision to give the trip signal. This system impedance can be calculated from knowledge of the fundamental frequency components of the voltage and current waveforms, these, in turn, being determined by processing appropriate waveforms sampled at the relay point. Fourier-series analysis is one method suitable for processing the sampled waveforms and for determining their fundamental components. The analysis is designed for continuous, periodic waveforms and, in these circumstances, separates the various harmonic components of the waveform. Its behaviour under the nonperiodic conditions of fault incidence and transient interference will be demonstrated.

Microminiature integrated circuit impedance device including weighted elements and contactless switching means for fixing the impedance at a preselected value

Abstract: A microminiature terminal-adjustable integrated circuit impedance device comprising a substrate, a plurality of impedance elements formed on the substrate with each impedance element having an impedance, a first input terminal, an output terminal, a plurality of electrically permanently alterable contactless switching elements formed on the substrate, each of the switching elements being associated with one of the plurality of impedance elements and having initially a first switching state and being permanently alterable by application of electrical energy to an opposite switching state, an interconnecting means interconnecting the impedance elements and the switching elements in a first circuit configuration between the first input terminal and the output terminal such that the impedance between the first input terminal and the output terminal is of a first value, and a plurality of adjustment terminals each being connected to a different one of the plurality of switching elements for facilitating the application of electrical energy thereto to cause such switching elements to change to the opposite switching state, whereby the application of electrical energy to selected ones of the adjustment terminals causes a second circuit configuration having a preselected second value to be formed between the first input terminal and the output terminal. Each electrically permanently alterable contactless switching element is comprised of fusible conductive links or shortable diodes, singly or in combination. In the preferred embodiment the device comprises resistive elements fabricated with state-of-the-art thin film or monolithic integrated circuit technology and serves as a variable resistor or as a variable voltage divider performing the function of a fixable contactless trimming potentiometer.

Measuring cells for measuring electrical conductivity of liquids

Abstract: A measuring cell for measuring electrical conductivity of liquids having a bore which in operation is contacted by a liquid, the conductivity of which is to be measured and a plurality of electrodes spaced along the bore and forming part of the bore surface, the electrodes being of coaxial annular form and including a first and a fourth electrode which constitute current electrodes for connection to a controllable AC current supply, a second and third electrode between the current electrodes and constituting voltage electrodes for connection to a high input impedance amplifier provided with means for employing the amplifier output to control the AC current supply to maintain sensibly constant the voltage at the voltage electrodes and a fifth electrode of annular form coaxial with the first to fourth electrodes and for connection to the first electrode by way of a buffer amplifier presenting a high impedance to the first electrode and a low impedance to the fifth electrode and located on the side of the first electrode remote from the fourth and voltage electrodes.

Use of Ritz and Bubnow-Galerkin methods for calculation of inductance and impedance of conductors

Abstract: It is shown that the Ritz and Bubnow-Galerkin methods can be applied for the calculation of the inductance and the impedance, respectively. Moreover it is shown that the calculation of the impedance by the Bubnow-Galerkin method is a generalization of the calculation of the inductance by the Ritz method in the case of a nonhomogeneous Neumann boundary problem. For the illustration of these methods the inductance of a rectangular ferromagnetic conductor and the inner impedance of a rectangular conductor placed in a semi-closed slot are calculated.

High speed transmission line fault impedance calculation using a dedicated minicomputer

Abstract: An algorithim for calculating apparent transmission line impedance to the point of a fault is presented as an approach to distance type protection via a dedicated digital computer. Phase voltages and currents are sampled asynchronously approximately 24 times per cycle and operated on to yield apparent resistances and reactances. Descrimination between phase to phase, phase to ground and two phase to ground faults is considered. The effects of disturbances such as transformer magnetizing inrush currents, assymetrical currents, sensor response, as well as results which can be expected when the power system frequency is higher or lower than nominal are discussed. The reach accuracy of the system is reported using simple statistical measures obtained from simulating the operation of the digital relay on an IBM 360/65 computer. These simulations verify the approach is feasible.

High frequency excited electrodeless light source

Abstract: A light source includes an electrodeless lamp having an envelope for enclosing a volatile fill material which emits light upon vaporization and excitation, a source of power at a high frequency and a termination fixture coupled to the source. The fixture has inner and outer conductors which have dimensions such that the lamp is located in the high field region at the end of the conductors. When the high frequency power is applied to the fixture, a voltage standing wave is formed which initiates vaporization and excitation of the fill material. The termination load impedance which is that of the lamp changes from a lossy open circuit to a finite value when vaporization and excitation occur. An impedance matching device is provided for matching the running lamp impedance to the output impedance of the source.

Dual channel dynamic line isolation monitor

Abstract: A line isolation monitor for indicating the maximum hazard current in an ungrounded power distribution system with conductor lines having leakage impedances. A signal proportional to the maximum voltage to ground of any of the conductor lines in the system is determined and used as a reference voltage for the monitor. Separate circuits each responsive to the reference voltage generate respectively a capacitive component signal and a resistive component signal which are combined and applied as a measurement signal across the system leakage impedances in parallel. The impedance voltage response to the measurement current is separated from the line voltage signal, phase shifted and compared to the reference voltage signal to produce a difference signal which is used to control the magnitude of both the capacitive component signal and the resistive component signal. The magnitude of the combined capacitive component signal and the resistive component signal represents the maximum hazard current.

Reactive power compensator

Abstract: Reactive current compensating apparatus for a multiphase electric power circuit comprises separately variable reactive impedance elements coupled to the power circuit in multiphase relation through phase shifting means such as a tertiary transformer winding When phase voltage supplied to the compensating impedance leads or lags the line-to-neutral voltage of the power circuit the compensating effect in respect to negative phase sequence line current components is enhanced as compared to direct conductive connection of compensating impedance to the power circuit

Digital thermodynamic flow-meter

Abstract: An apparatus is disclosed for measuring instantaneous rate of flow and total flow of a fluid. The data are obtained by measuring the quantity of energy necessary to replace an equivalent amount of heat dissipated from a temperature-sensitive transducer disposed in the path of the fluid flow. An error signal, resulting from a transducer impedence change due to a differential temperature, induced by fluid flow, is placed in digital form and fed back to the transducer in a closed feedback loop configuration. The feedback signal is in the form of discrete power pluses. The number of such pulses is proportional to the heat removed from the transducer by the flow and thus is proportional to the fluid flow rate. The output pulses are counted and displayed in associated digital equipment.

Force and electrical Thevenin equivalent circuits and simulations for thickness mode piezoelectric transducers

Abstract: A simple model is reported for thickness‐mode piezoelectric elements used as ultrasonic transducers in measurement systems. The model represents the excitation system and transducer as a Thevenin mechanical equivalent for the transmitting mode and a Thevenin electrical equivalent for the receiving mode. Computer programs based on the model have been developed, and computer simulations to study the effects of backing materials, element areas, and excitation sources are reported. The nature in which the source impedance alters the Thevenin mechanical output impedance and its importance in determining peak transmission frequency and in computing acoustic coating layers for matching was found. A total transfer improvement of 28 dB was shown for epoxy‐backed elements radiating into fluid with the transducer used as both transmitter and receiver by using high values of source and load impedances in contrast to low values. The model was found to agree closely with experimental data of a 2.7‐MHz transducer.Subject Classification: 85.40; 80.70; 85.52.

A computer based, four terminal impedance measuring system for low frequencies (designed for plasma membrane of living cells)

Abstract: A four terminal high precision measuring system is described for the determination of capacitance, C, and conductance, G, at very low frequencies (0.1-1000 Hz). The method, which offers both speed (close to the theoretical upper limit) and accuracy (phase +or-0.01 degrees , impedance amplitude +or-0.1%) was specifically designed for the investigation of the dispersion of C and G in the plasma membrane of living cells. The system, with minor modifications should, however, also find application elsewhere. The system described was designed around a small computer which is used, via analogue-digital and digital-analogue converters and digital interfaces to both control and measure the frequency and amplitude of the AC signals and to measure the AC potential appearing across the impedance under test. After the data for a complete set of programmed frequencies has been collected the analysis of the data points for current and voltage, which may be accumulated in memory over a specified number of cycles, yields the relative phase and amplitude of the current and voltage and hence C and G.

Effects of Space Charge and Reactive Wall Impedance on Bunched Beams

Abstract: Space charge and reactive wall impedance create longitudinal forces inside the bunch which change the incoherent phase oscillation frequency, the bunch length and the size of the RF-bucket. These effects have been investigated with bunched beams in the ISR. By measuring the shift of the quadrupole mode phase oscillation frequency, the strength of the self-forces was determined. The inductive wall is dominant and its impedance (divided by the mode number) was measured to be |Z|/n z 26 Ohms. An increase of bunch length with current was measured. It can be explained by the inductive impedance up to a certain current; beyond that an excessive, unexplained bunch lengthening occurs. The reduction of the bucket size affects the stacking process. By correcting for it, an increased density of the stacked beam was achieved. Ez = -e az [4 g0 dz (1)

Signal attenuator circuit for TV tuner

Abstract: In a tuner for a television receiver, an attenuator circuit coupling a signal input to a signal output network includes a series connected controllable impedance and amplifier stage connected to a source of AGC potential whereby increased signal strength causes an increased AGC potential which reduces current flow through and increases the impedance of the controllable impedance while reducing the gain, and consequently the noise, of the amplifier stage coupled to the signal output network. In another aspect of the invention, a second attenuator circuit includes a second controllable impedance series coupling a signal input to the attenuator circuit and a third controllable impedance coupling the junction of the first and second controllable impedances to circuit ground for effecting an additional increased attenuation of a received signal.

Electrodeless light source utilizing a lamp termination fixture having parallel capacitive impedance matching capability

Abstract: A termination fixture for use in an electrodeless light source has an input impedance which is matched to the output impedance of a high frequency power source, even though the lamp which forms the termination for the fixture has a complex impedance when the lamp is in an excited state. The fixture has a pair of coaxial conductors of at least a quarter wavelength, the conductors being coupled to the source at one end and to the lamp at the other end. The conductors are shaped to create an impedance which matches the real component of the lamp impedance to the source impedance. A capacitor is formed across the inner and outer conductors at the source coupled end to compensate for the series capacitive reactance part of the lamp impedance at the lamp coupled end of the conductors.

Impedance characteristics of diodes operating in the self−pinch mode

Abstract: The impedance characteristics of large aspect ratio diodes employing hollow field emission cathodes operating in the self−pinch mode have been studied at electron kinetic energies between 400 and 800 keV and currents between 100 and 500 kA. The importance of correcting the anode−cathode gap spacing for closure due to plasma motion is recognized and taken into account in the definition of the diode aspect ratio in impedance calculations. With this correction, the impedance at peak diode voltage and current is found to be nearly independent of voltage and cathode surface area, and inversely proportional to the diode aspect ratio. Its amplitude is approximately 50% higher than that predicted by parapotential flow theory.

Saturable reactor current limiter

Abstract: A current limiter to protect circuit elements from excessive current caused by transient load impedance or power supply surges. A multiple branch element magnetic circuit includes at least one saturable branch element inductively coupled by a coil connected in series with the load of an external electric circuit. The magnetic circuit further includes lower permeance bias branch element which biases the saturable branch element in a low permeance, saturated state when current through the coil is below a predetermined threshold value, and which biases at least one saturable branch element in its high permeance, non-saturated state when current through the coil is in a predetermined range above and extending from the threshold value. A relatively high permeance shunt branch element provides a shunt path for magnetic flux. The coil provides a relatively high inductive impedance in series with the external electrical circuit when at least one saturable element is in its non-saturated state and provides a relatively low impedance otherwise.

Helical coupler for use in an electrodeless light source

Abstract: A termination fixture for exciting an electrodeless lamp with high frequency power matches a capacitive complex impedance of the lamp in an excited state to the output impedance of the high frequency source coupled to the fixture. The fixture has a pair of coaxial conductors which have a length of one quarter wavelength and which have a ratio of diameters effective to match the real impedance of the lamp to the impedance of the source. A helical coil couples the end of the inner conductor to the lamp. The purpose of the coil is to make the impedance of the lamp, as viewed, electrically, from the end of the inner conductor appear as having only the real component. The quarter wave fixture then matches the real impedance to the source impedance.