Showing papers on "Electrical impedance published in 1973"

Efficient Capacitance Calculations for Three-Dimensional Multiconductor Systems

Abstract: The design and packaging of integrated circuits requires the calculation of capacitances for three-dimensional conductors located on parallel planes. An integral-equation (IE) computer-solution technique is presented, which provides accurate results. The solution technique minimizes computer storage requirements while maintaining calculating efficiency computation times.

Output monitored electromechanical devices

Abstract: An electromechanical device comprises a pair of like transducer units affixed to a bar having with the transducers natural frequencies of vibration so that one unit is nearer a node than the other. An impedance is connected in series with each transducer unit, and the two series circuits are paralleled. The difference current through the two impedances is directly proportioned to the displacement of the vibrating bar, both at its mechanical resonance frequency and at its mechanical plus electrical anti-resonance frequency.

A computer simulation of the generation and distribution of cochlear potentials.

Abstract: A model for the generation and distribution of electrical potentials within the guinea pig cochlea was simulated by computer. Electrical impedances of the cochlear tissues and biological batteries in the stria vascularis and organ of Corti were modelled by a three‐dimensional network of resistors and batteries. It was assumed that cochlear‐partition movements caused electrical‐impedance changes in hair cells and resulted in modulation of steady‐state electrical currents normally flowing throughout the cochlea. The model response to a 1000‐Hz tone demonstrated that the amplitude envelope for the electrical current through the hair cells had the same shape as the mechanical traveling‐wave envelope, whereas the envelopes for the potential changes within cochlear scalae were broader and had their peaks nearer the basal end of the cochlea. Potentials generated by the model accurately reflected the amplitude and phase of the cochlear‐partition displacement only from the base to within about 3 mm of the peak of the traveling‐wave envelope. An important finding was that, when the impedance of a hair cell was decreased, current from adjacent hair cells was shunted through it, thus providing a possible excitation‐inhibition mechanism for neural sharpening.

Stimulation control apparatus for an ink jet recorder

Abstract: A drive circuit for a stimulation transducer suppresses generation of satellite drops in an ink jet recorder. The drive circuit is an oscillator which tracks the resonant frequency of the stimulation transducer. As the resonant frequency of the transducer changes during normal operation, the frequency of the driving signal also changes, so that the power output of the transducer remains essentially unchanged. This provides accurate regulation of the filament length for the jets being stimulated and unexpectedly also suppresses generation of satellite drops. The drive circuit comprises an amplifier, a load resistor and positive and negative feedback paths to the input terminals of the amplifier. The load resistor is incorporated within the negative feedback path as well as within the supply path for the stimulation transducer. In general the impedance of the stimulation transducer is minimum at the resonant frequency thereof, so that for any shifting of the resonant frequency there is an increase in the input impedence to the transducer. This produces a voltage variation across the load resister which in turn alters the negative feedback to the amplifier. Means are provided for adjusting the negative feedback signal so as to maintain the amplifier in a state of continuous oscillation. The frequency at which this oscillation occurs is the frequency at which the impedance of the transducer is minimum, and therefore the drive circuit tracks the resonant frequency of the stimulation transducer.

Automatic antenna coupler utilizing system for measuring the real part of the complex impedance or admittance presented by an antenna or other network

Abstract: An automatic antenna coupler is described which includes a matching network having adjustable reactive elements. Control for these elements is provided by a system for detecting the real part of the complex impedance presented by the antenna or matching network. A logic and control system for adjusting the reactive elements is operated in accordance with the real part detector output so as to provide the desired impedance match.

rf impedance of superconducting weak links

Abstract: The rf impedance of a superconducting weak link with negligible capacitance is calculated for a variety of operating conditions. It is shown that the impedance is always real between harmonic steps of the I‐V characteristic. The real part of the impedance is negative under certain conditions of bias for small rf signals, thus indicating the region of self‐oscillation of the weak link.

High speed control of reactive power for voltage stabilization in electric power systems

Abstract: In a multiphase alternating current electric power system subject to erratic and unbalanced reactive load current demand, reactive load current compensation is provided by a balanced multiphase reactive compensating impedance having equal but limited reactive current capability in all phases. To increase reactive current capability of any one selected phase of the reactive compensator in response to severe load unbalance a supplementary single phase compensating impedance is connected through a load current controlled switching bridge in parallel circuit relation with any one phase arm of the multiphase compensator. When any one such parallel connection is operative the switching bridge is prevented from connecting the supplementary impedance in any other phase arm of the multiphase compensator.

Impedance plethysmograph having blocking system

Abstract: An impedance plethysmograph has an oscillator for applying constant current to the thorax of a patient. A detector circuit connected to the patient provides an output corresponding to thoracic impedance. Circuits responsive to detected impedance provide signals corresponding to change of impedance and the first time differential of impedance. Means are provided to block the differential signal when it is meaningless, for example, due to respiration.

Electrical sensing circuitry for particle analyzing device

Abstract: The electrical sensing circuitry includes a power supply and a signal-detecting circuit which are coupled through the resistance of an electrolyte in a liquid in an aperture of a particle-analyzing device between sensing electrodes positioned on either side of the aperture. The liquid containing an electrolyte and the passage of a liquidborne particle through the aperture causes a change in the resistance of the aperture thereby generating a signal which is detected by the signal-detecting circuit. The parameters of the circuit elements are chosen to provide circuit relationships which render the particle-generated signal independent of the diameter of the aperture. This is achieved by utilizing a power source having a low output impedance and a signal-detecting circuit which has a low input impedance for both D.C. and A.C., namely, at the signal frequencies of the signals sensed. The electrical circuitry also may include a conductivity monitoring circuit which may utilize one or more of the sensing electrodes and/or additional electrodes for monitoring changes in conductivity of the electrolyte and for relating these changes in conductivity to the particle-generated signals sensed by the signal-detecting circuit to alter those signals so as to render them independent of electrolyte resistivity.

A Generalized Design Technique for Practical Distributed Reciprocal Ladder Networks

Abstract: A generalized design approach is presented for ladder networks consisting of a cascade of constituent two-port networks connected by short lengths of transmission lines. The design is made possible by the derivation of simple equations which define the inverter impedance and associated reference planes of any passive lossless reciprocal two-port. This enables the general ladder network to be equated to a prototype network at a reference frequency. An example is given of the design of a coaxial low-pass filter where fringing capacitances are compensated automatically.

Bistable impedance states in MIS structures through controlled inversion

Abstract: Metal silicon‐nitride n‐p+ silicon diodes have been fabricated with I‐V characteristics similar to those of a four‐layer diode. Switching between the two impedance states, whose impedance levels differ by a factor of the order of 106, can be accomplished in less than 5 nsec. The impedance of the device is controlled by the presence or absence of the inversion layer of the MIS structure. Both impedance states require a nonzero conductance of the insulator.

The generalized multiprobe reflectometer and its application to automated transmission line measurements

Abstract: The multiprobe reflector can perform the measurements usually performed with the slotted line without the need for mechanical adjustment, thus making it ideal for automated systems. Theory is presented showing how impedance data may be obtained from three or more arbitrarily placed probes; the spacing need not be at any particular fraction of a wavelength thus permitting very wide band operation. The use of additional probes permits measurement of frequency and also self checking of the system, thus providing accuracies comparable with the best slotted lines available. The simplicity of the hardware makes it easy to install in both standard and non-standard waveguides and transmission lines thus avoiding the use of adaptors with their attendant errors. A brief error analysis is included. Measurements of antenna impedance and wall loss, using a nonstandard size of waveguide, are presented and show an accuracy comparable with the best slotted lines.

The Hydra Electron Beam Generator

Abstract: The Hydra electron beam generator was designed to simrultaneously produce two 1 MV, 0.5 MA, 80 nanosecond electron beams that could be combined to form a single beam. The machine, undergoing final developmental tests, has generated a 0.5 MA, 1 MV peak electron beam from each line. This accelerator consists of a low-inductance Marx generator, two water-dielectric pulse-forming (PF) and impedance-transforming transmission lines and two low-inductance, high-current diodes. A description of the generator is presented along with developmental studies and initial testing data. The Hydra machine is based on accelerator principles described in the literature. The Marx generator is submerged in transformer oil and separated from the transmission line water by a lucite interface. The Marx charges each coaxial PF transmission line which is deionized water insulated to 3 MV in 0.9 microseconds. At peak voltage, a 3 MV SF6 spark gap electrically connects the 4 ohm PF line to the impedance transforming (4 ohm to 2 ohm) transmission line. The pulse is transmitted through this line to the single radial insulator diode. A 30 kilojoule, 100 nanosecond duration electron beam is formed by a cold cathode in each diode.

Communicating over power lines

Abstract: An audiofrequency signal is applied to a power amplifier having an output impedance of considerably less than an ohm that is coupled through a network comprising at least a capacitor that presents a low impedance to this audiofrequency signal and much higher impedance to energy at the 60 Hz power frequency to a power line to provide an amplified signal that is transmitted to a receiver separated from the transmitter by at least one distribution transformer and having a high pass filter for rejecting the 60 Hz power frequency and a number of harmonics thereof while transmitting the audiofrequency signal. The system is especially advantageous for using ordinary power lines for transmitting information in connection with automatic meter reading.

Power Deposition in a Spherical Model of Man Exposed to 1-20 MHz EM Fields

Abstract: EN power deposition in a spherical model of man exposed to HF fields may be derived from a simple approximate equation where the absorbed power due to electric field coupling can be calculated separately from that due to magnetic coupling. The latter is an order of magnitude greater for a plane wave.

R. f. impedance bridge for measuring reflection coefficient

Abstract: A bridge for measuring the reflection coefficient of a twoterminal load, in which the insertion loss between an input port and an output port is proportional to the reflection coefficient of the load connected to a third port, and the constant of proportionality is substantially independent of frequency; includes a balun, a first two-terminal network connected in one arm of the bridge, a second two-terminal network connected in the opposite arm of the bridge, and a resistance equal to the reference resistance in the arm opposite the port to which the load is connected. The impedance of the second network is the inverse, relative to the reference resistance, of the parallel combination of the first network and the additional impedance to ground caused by the connection of the balun.

Dynamic ground detector

Abstract: A dynamic ground detector for monitoring a two-wire power distribution system, where both sides are nominally isolated from ground. A sampling bridge is connected between the lines, each shunt section of the bridge comprising a resistor and a capacitor having impedances in quadriture at the line frequency; and the junctions of the shunt sections of the sampling bridge are alternatively sampled by a switching network. The switching network connected through a phase shifting network comprising an RC filter to a detector network comprising a fullwave rectifier with suitable indicator and alarm apparatus. The rate of sampling is a multiple, including unity, of the line frequency. Additional circuitry may also be provided for sensing the direction and phase of any fault current caused by a fault to ground from either or both of the lines, so that the fault current may be opposed by insertion of another current having the same phase and opposite direction.

Method and apparatus for dissipating high frequency energy inside a material to be treated

Abstract: Method and apparatus for dissipating high frequency electromagnetic energy inside a material. The apparatus comprises a conductive jacket defining a resonant chamber, a coil inside said chamber connected to a coaxial cable supplied by a high frequency generator, the frequency of which is equal to the resonant frequency of the chamber. The impedance of the resonator and its contents is matched to that of the coaxial cable. Automatic means may be provided for altering the resonator impedance to compensate for changes in load impedance.

Method and apparatus for measuring the moisture content of wood

Abstract: A method apparatus for determining the moisture content of wood by measurement of the impedance of the wood utilizing an alternating current electrode sensor connected to a shielded conductor with the shield being ungrounded and driven in phase with the conductor.

Small-signal characteristics of semiconductor punch-through injection and transit-time diodes

Abstract: The two terminal impedance characteristics of the semiconductor punch-through structure are examined for operation under low-field, i.e. constant mobility, conditions. It is shown that a straightforward analytical description can be obtained by the use of the complex number methods of alternating current theory. Various modes of operation are described as characterised by space-charge-limited injection, emission-limited injection and barrier-limited injection. Negative resistance is found in all cases and is due to the propagation of space-charge waves which move in anti-phase with the local field through a substantial volume of the device. The negative resistance effects are increased by the use of low-mobility material which increases the phase lag of current. Series resistance and series capacitance are calculated as functions of frequency and current bias for representative silicon devices. The magnitude of the available negative resistance is numerically small in the low-field structure and is unlikely to lead to practical applications. However, the analysis which is presented provides insight into the working mechanisms of the high-field structure and this device, known as the punch-through transit-time diode or BARITT diode, is already proving to have practical value in microwave systems.

A current-excited large-signal analysis of IMPATT devices and its circuit implications

Abstract: A large-signal analysis of a Read-type IMPATT diode is carried out with a sinusoidal current as the excitation. The results are compared with analyses that assume a sinusoidal voltage excitation. The large-signal impedance of the diode with current excitation is expressed in closed form. The circuit implications of choosing voltage or current as the excitation are discussed.

Perturbation theory for a resistivity shunted Josephson element

Abstract: We present a systematic perturbation theory, extendable in principle to all orders of magnitude, for the solution of the equations of motion of an ideal Josephson element shunted by a resistance and driven by a dc current source and a small time‐dependent source We present second‐order results for the case in which the time dependence is that of a single sinusoid, and these results are compared with other numerical and analytical calculations Near, but not on, the first constant voltage step where the perturbation theory appears divergent, the current‐voltage characteristic is calculated by means of a nonperturbative adiabatic procedure The impedance and responsivity agree with earlier results

Characteristic impedance of surface-strip coplanar waveguides

Abstract: The dependence of the characteristic impedance of a coplanar waveguide is measured as a function of slotwidth and substrate thickness. For alumina substrates (er= 9.2), it is shown that the substrate thickness should be at least twice the slotwidth for an accurate determination of this impedance.

DC Arc Model Including Circuit Constraints

Abstract: Digital computer techniques are used to simulate a steady-state d-c arc. The (longitudinal) input and (radial) loss powers to a section of the positive column are used to establish the positive column temperature and electron density. A power balance is also used to derive cathode conditions. Finally, current adjustment is made so that the positive column and cathode results agree. For given input conditions (voltage, arc length, gas), current and temperature are calculated; some input choices do not lead to valid arc conditions. Results are shown to compare well with experimental data.

Electromagnetic flight stability by model impedance simulation

Abstract: Impedance measurements on scale models can be an extraordinarily simple and effective technique for comparing the lift and drag forces and the static and dynamic stabilities of various vehicle‐guideway configurations for levitation by motion‐induced eddy‐current repulsion. The real and imaginary components of the input impedance of an inductive circuit are a measure of its power loss and magnetic energy storage, and the gradient of that energy is magnetic force. As a demonstration of the technique, we have applied it to variations of the magneplane system being developed by the MIT‐Avco‐Raytheon group.

Measurement techniques for antennas in dissipative media

Abstract: Methods used to simulate dissipative media environments for antennas are reported and special techniques developed to determine the electrical properties of antennas in such media are discussed Tank systems for simulating infinite homogeneous isotropic media characterized by ratios of \alpha/\beta in the range 0 are described along with the apparatus for determining the constitutive parameters \sigma and \epsilon of the media A new device for measuring antenna input admittance is presented which permits a simple measurement of admittance over a broad frequency range where conventional methods are cumbersome in field use Apparatus for measuring antenna current and charge distributions is described together with a discussion of the associated probing errors Measured admittances and current and charge distributions are compared with current theories for thin wire linear and loop antennas in the dissipative media and are found to be in good agreement

Controllable current source

Abstract: A circuit for providing a current the magnitude of which is determined by an externally generated control signal and which is substantially independent of the impedance of the load to which the current is applied. A current generating network generates an output current in accordance with the algebraic sum of the control signals applied to the inputs thereof. One of these inputs is energized by an externally generated control signal which sets the desired value of output current. A second of these inputs is controlled in accordance with a feedback signal indicative of the output current to assure that attempted deviations of the output current from the desired value are counteracted before they substantially affect the level of current through the load.