Showing papers on "Output impedance published in 1981"

Battery testing techniques

Abstract: A system and method for testing a battery having an internal impedance by generating digital battery parameter values corresponding to the battery parameters at different points in time by means of current, voltage and temperature measurement circuits and an analog-to-digital converter. An electrical load is periodically placed on the battery and the battery is also charged between loadings in order to provide battery parameter values during different battery conditions. A microprocessor coordinates the testing of the battery and the measuring of the battery parameter values, as well as the calculation of test criteria based on those values in order to quickly and accurately analyze the condition of the battery.

Transcutaneous signal transmission system and methods

Abstract: Greater positioning tolerance is permitted in inductively coupled transmitter and receiver tuned circuits by achieving critical coupling therebetween. Critical coupling at a predetermined distance is obtained by selecting the appropriate quality, Q, of the tuned circuit, whereby the quality of the transmitter tuned circuit is preferably three times larger than the quality of the receiver tuned circuit. In a transcutaneous signal transmission system the critical coupling is realized by adjusting the spacing of the coils of the tuned circuits whereby the output impedance of the transmitter decreases to one-half the output impedance with no coupling.

Non-linear electrical properties of skin in the low frequency range

Abstract: This paper describes the non-linear electrical properties of the skin during the passage of a sinusoidal current from the standpoint of the constant-current method. The non-linearity occurs in the current dependency of the skin impedance and in Lissajous figures. It exhibits both rapid and slow variations. The concept of a non-linear impedance and its equivalent circuit are introduced for a sinusoidal voltage. With regard to the current dependency of the impedance it can be said that both the starting point and the degree of the dependency vary with frequency and impedance. The nonlinearity is more apparent with a larger current, a lower frequency, and a higher impedance. with an increasing current, the ionic conductance increases and the polarisation admittance decreases. Lissajous figures are formed when the voltage is distorted notably from the sinusoidal wave form. Detailed investigations are undertaken for the elliptic figures, third harmonics, rectification, and breakdown of the skin appearing with a decrease of the frequency and increase of the current. Finally, the special mechanism of the ionic conduction in the keratin layer is indicated as one of the causes for non-linearity.

Infinite available gain in a 115 GHz SIS mixer

Abstract: We report the observation of infinite available conversion gain at 115 GHz with an SIS mixer. The output impedance can be smoothly changed from positive, through infinite, to negative. The mixer consists of a series array of N = 14 thermally recyclable Pb-alloy tunnel junctions in a reduced-height waveguide mount. The best mixer noise temperatures measured are consistent with a quantum noise temperature of Nħω/k.

Fundamental Considerations and Impluse Impedance of Grounding Grids

Abstract: The impulse impedance of a grounding grid must be known for determining its performance while discharging impulse currents to ground if problems concerning lightning protection and transients under ground faults are to be accurately analysed. This paper out-lines the basic concepts required for this study, analyses the equivalent circuit ,21]of a grounding grid for its response to practical impulses like ramp (i.e. idealised lightning stroke) and double exponential wave inputs and establishes expressions for the impulse impedance. Its value is shown to be higher than the grid's power-frequency grounding resistance, decaying to this latter value with passage of time. Inductance of the grid is shown to be the governing factor contributing to its impulse impedance. Only those values of current which do not cause breakdown of the soil are considered

On-board vehicular network method for efficient generator utilization

Abstract: To utilize the full power capacity of alternators 1, the alternator phases are connected through a transformer 9 to the rectifier 4 which provides rectified output to a battery 8. The transformer 9 has tapped windings, the taps being placed in circuit with the alternator-rectifier network in dependence on a speed control signal, for example derived from the frequency of the alternator, to effect tap changing and matching of the internal impedance of the alternator 1 to the battery 8/load L combination. In accordance with one feature (FIGS. 2, 3), the taps are on the primary, and a-c switches such as triacs 15 are selectively energized as the speed of the generator changes; in accordance with another embodiment (FIGS. 4, 5), the taps are on the secondary of the transformer, and unilaterally conductive switches, such as thyristors or SCRs 48, can be used, in parallel with the rectifier diodes 47 of the rectifying array, and selectively fired as a function of speed. A nominal 35 A output alternator thus can provide secondary output currents which, in one embodiment (FIG. 3) may go to over 80 A or, in the other (FIG. 5), to over 55 A, the closeness of matching and eventual output power depending on the voltage rating of the alternator and the number of taps on the transformer, and hence the degree of match obtainable.

Insertion loss studies on models of automotive exhaust systems

Abstract: Transmission loss, noise reduction, and insertion loss are the three main characteristics used to describe the performance of a muffler in an automotive exhaust system. Of these characteristics, insertion loss is the most useful. Unlike transmission loss and noise reduction, insertion loss is dependent on both source and radiation impedances. In this paper, source and radiation impedances were measured. The insertion loss of exhaust systems was predicted using theoretical values of radiation impedance and measured values of source impedance. Comparisons of predicted and measured insertion loss are given for various source and radiation conditions. So far the investigations are confined to an electroacoustic driver source and an expansion chamber muffler.

The impedance of an elliptical printed-circuit antenna

Abstract: A resonant circuit model for the input impedance of an elliptical printed-circuit antenna has been developed and the results compared with experimental data. The impedance and bandwidth were then calculated as a function of the size, eccentricity, and thickness of the radiator.

Impedance transforming three port power divider

Abstract: A modification of a Wilkinson combiner/splitter is described wherein, by means of selection of the characteristic impedance of the transmission media and the value of the combining impedance, the combiner/splitter may be matched to input and output impedance which are not the same.

Impedance of a loop surrounding a conducting cylinder

Abstract: The change in complex impedance between an ideal one-turn coil surrounding and coaxial with an infinitely long circular cylinder of conductivity δ and permeability μ and a similar coil without the core has been calculated. From the exact expression, a power series in the quantity δ/b (δ=skin depth; b=radius of core) has been developed. From this result, the change in impedance of a physically realistic multiturn coil can be estimated. The theory permits a rational approach to optimization of the design of eddy-current test coils and provides a possible means of detecting changes in the radius and conductivity of the cylinder.

Control system for transducer positioning motor

Abstract: A control system for a stepper motor utilized in positioning a transducer in relationship to a plurality of parallel tracks on a record media. Dual closed loop feedback systems are provided. A current control circuit is provided having a high output impedance and a voltage control circuit is provided having a low output impedance. A switch may select the control sensor when the transducer is making coarse adjustments in position and may select the voltage control sensor when the transducer is making fine adjustments in position. A seamless switchover may be achieved where the voltage control sensor has a time constant which matches the time constant of the stepper motor. Performance is further improved by providing an impedance cancellation circuit which eliminates the internal resistance of the motor in order to quickly damp motionally induced emf of the motor.

Apparatus for testing semiconductor devices and capacitors

Abstract: An apparatus is provided for testing semiconductor devices. The apparatus tests the impedance of the semiconductor devices in both conducting and non-conducting states to detect semiconductors whose impedance in the conducting state is too high or whose impedance in the non-conducting state is too low. The apparatus uses a battery source for low voltage d.c. The circuitry for detecting when the impedance is too high in the conducting state includes a lamp in series with the battery source and the semiconductor device, whereby the impedance of the semiconductor device determines whether sufficient current will flow through the lamp to cause the lamp to illuminate. A d.c. to d.c. converter is provided to boost the voltage from the battery source to a relatively high voltage d.c. The relatively high voltage d.c. can be connected by a switch to circuitry for detecting when the impedance of the semiconductor device in the non-conducting state is too low. The circuitry for detecting when the impedance of the semiconductor device is too low includes a resistor which senses the current flowing in the device and converts the current into a voltage proportional to the leakage current. This voltage is then compared against a fixed reference. Further circuitry is provided for providing a visual indication when the voltage representative of leakage in relation to the reference signal indicates that there is excessive current flow through the semiconductor device.

Passive control network for remote control of load output level

Abstract: A passive control network for connection between a pair of load output level setting terminals, as on a ballast for a dimmable fluorescent lamp in a lighting system, to provide a required variable impedance, where the magnitude of the impedance establishes the load output level. The passive control network includes an isolation transformer for coupling a periodic waveform at the load input terminals to the variable impedance component, the magnitude of which impedance is reflected through the transformer to provide the load level-setting impedance.

Wide band modem for high speed data transmission

Abstract: A method and apparatus are described for coupling a high-speed data communication modem to a communication line such as a coaxial cable with minimal transmission losses when the modem is not transmitting data. The transmitter coupling apparatus comprises a transformer, first and second transistors, biasing circuits for each of the transistors and a low-pass filter. The data signal to be transmitted is applied to the first transistor which is biased for linear amplification when data are being transmitted and for saturation when data are not being transmitted. The output of the first transistor is applied to the primary winding of the transformer where it is coupled to the secondary winding which is connected in series with the central conductors of the coaxial transmission line. When saturated, the first transistor grounds the winding terminal to which it is connected. The second transistor is biased so as to couple a power supply through the low-pass filter to the other terminal of the primary winding when data are being transmitted and to be non-conducting when data are not being transmitted. The low-pass filter and the first transistor provide a short circuit with respect to high frequency signals across the primary winding when data are not being transmitted. The receiver is likewise transformed coupled with its primary winding being in shunt across the transmission line. As a result of these connections, the output impedance of the transmitter can be made small enough so that the modem insertion loss is about 0.2 db.

Negative resistance and conversion gain in SIS mixers

Abstract: We report the observation of negative quasiparticle dynamic resistance on the DC I–V curves of superconductor-insulator-superconductor tunnel junctions. This negative resistance appears on the first few photon assisted tunneling steps below 2Δ/e when our tin-tin oxide-tin tunnel junctions are pumped with a 36 GHz microwave current source. We present a simple analytical model which shows that large (and also negative) dynamic quasiparticle resistance is expected for junctions with sharp I–V curves when the microwave source impedance is high. Because the dynamic resistance can be very large, an impedance-matched quasiparticle mixer should have unlimited gain. We have observed a net mixer gain of 4.3±1 dB at 36 GHz with a mixer noise temperature ≲10K.

Power source circuit

Abstract: A power source circuit having a reference voltage generating circuit for generating a DC reference voltage a current output circuit provides across output lines a current proportional to an input voltage, and an error voltage integration circuit is provided for integrating a voltage proportional to a difference between the DC reference voltage and the voltage across the output lines at a required integration time constant to apply the integrated output as the input voltage to a current output circuit. The integration time constant is set so that an output terminal connected to the output lines may have a low output impedance in terms of direct current to maintain a predetermined constant DC output voltage and have a high output impedance with respect to an AC signal applied to the output lines.

Phasor impedance measuring test set

Abstract: Test set apparatus for measuring the phasor impedance of a circuit under test, such as a telephone line. The test set apparatus also calculates for display the return loss of a circuit under test, against predetermined values of resistance or certain RC networks. To measure phasor impedance, the test set apparatus includes a signal generator providing a measurement frequency signal to a constant current source having an individual battery power source. The current source is connectable to measurement terminals, which provide for connection of a circuit under test, and produces measurement current flow through the circuit under test. During an impedance measurement, the battery-powered current source is connected to the measurement terminals and isolated from ground, thereby permitting operation of the test set apparatus to measure the impedance to a balanced circuit in the presence of externally-induced longitudinal voltages.

Variable impedance synthesis apparatus

Abstract: A variable impedance synthesis circuit is provided for generating a selected impedance, whether real or complex, at a predetermined port. The variable impedance synthesis circuit exhibits the selected impedance in response to control signals applied thereto.

Impedance transformation network for a SAW filter

Abstract: The IF section of a television receiver includes an amplifier having an input terminal for receiving an IF signal and an output terminal at which an amplified version of the IF signal is developed and a SAW filter having two input terminals, one of which is connected to AC signal ground, for receiving the amplified IF signal and an output terminal for providing a modified IF signal having a bandpass characteristic determined by the SAW filter. An impedance transformation network is coupled between the output terminal of the amplifier and the input terminal of the SAW filter for increasing the effective load impedance of the amplifier and for decreasing the output impedance of the drive arrangement. The former aspect of the impedance transformation network allows a transistor with lower current supplying capabilities to be employed. The latter aspect of the impedance transformation network tends to reduce undesired voltages developed in response to reflections between the transducers of the SAW filter. Specifically, the impedance transformation network includes an inductor connected between the output terminal of the amplifier and the AC signal ground, a capacitor connected between the output terminal of the amplifier and the input terminal of the SAW filter and a resistor connected between the input terminal of the SAW filter and the AC signal ground. Desirably, the capacitance of the capacitor is in the same order of magnitude as the input capacitance of the SAW filter and the inductance of the inductor is selected to provide a resonance with the effective capacitance in the passband.

Coupled line section tunable microwave filter - has parallel resonators extending across rectangular resonant cavity and tuning provided by variable capacitor

Abstract: The filter includes a resonant metal cavity (1) inside which there is a set of parallel conductors forming resonators (Ri-Rn). The number of resonators varies according to the required filter characteristics. The filter also includes an input impedance adaptor (ZE) and an output impedance adaptor (XS). Each resonator is fixed by one end to the front face of the box, and by the other end to the back surface of the box via capacitive coupling (Ci-Cn). The capacitive coupling is provided by threaded shafts penetrating part way into each resonator. Each shaft is accessible from the outside so that it may be screwed in or out to tune the resonator. Input and output signals are applied and taken respectively from two points (E,S) on the front surface of the filter. The filter operates in the range 500 MHz - several GHz.

RF Laser array driver apparatus

Abstract: An RF laser array driver apparatus with a DC bias input and and RF input to modulate a diode array and provide a modulated optical output. The driver circuit comprises a series impedance which is in parallel with the diode array to provide a 50 ohm impedance to the RF input signal that is substantially constant with frequency.

Range switching device for electric meter

Abstract: A range switching device for an electric meter, e.g. voltmeter, having a pair of input terminals, an impedance converting operational amplifier high in input impedance but low in output impedance having its input connected to one of said input terminals, a variable resistance and fixed resistance are connected in series between the output of said amplifier and the other input terminal, and the terminals of an electric meter made high in the input impedance by an impedance converting amplifier are connected across the ends of the fixed resistance, wherein the variable resistance is the aggregate of a plurality of groups of serially connected individual resistors, the individual resistors of each such group having the same resistance value while the resistance values of successive groups are successive multiples to a common base number of the fixed resistance value, each such group having switching contacts between the individual resistors of each group and at the ends of each group for selective engagement by a switch connected to one end of the next group to vary the number of functional individual resistors in that group. The number of individual resistors in each group normally will be one less than the common base number except that the number in the group corresponding to a multiple of one preferably equals the base number less two.

Step motor driving circuit of analog electronic watch

Abstract: PURPOSE:To prolong the life of a battery by reducing the through currents of transistors P-Ch and N-Ch by controlling transistors P-Ch and N-Ch for step motor drive by different gates. CONSTITUTION:Once a pulse of waveform beta arrives at terminal beta, the gate voltage of step motor driving P-Ch transistor (TR) TN4 drops slowly as shown by waveform 2-a since the output impedance of N-ChTRTN4 is high in its rise, and the gate voltage of step motor driving N-ChTRTN1 falls quickly as shown by waveform 2-b since the output impedance of N-ChTRTN5 is low. At the fall of the pulse input to terminal beta, the gate voltage of TRTP1 rises rapidly like waveform 2-a since the output impedance of TRTP4 is low and that of TRTN1 rises slowly since the output impedance of TRTP5 is high. Consequently, the through currents of the driving transistors can be reduced to prolong the life of a battery.

Bias circuit for a field effect transistor

Abstract: A field effect transistor (1) bias circuit is presented which exhibits a low impedance for small signals and a high impedance for large signals. This circuit uses an operational amplifier (6) to provide a temperature compensated low inpe- dance voltage source for the gate bias which is optimal for small signal operation. In the presence of a large signal, the gate begins to draw current. This causes the operational amplifier to saturate and transforms the bias circuit into a high impedance source, which is optimal for large signal operation.

Intrusion warning system

Abstract: An intrusion warning system for indicating the presence of an intruder to a given area includes an antenna provided around the area and which is insulated from the ground. An oscillator is provided for feeding an alternating current signal to the antenna, and a coupling impedance is connected between an output of the oscillator and the antenna. The coupling impedance includes an arrangement to vary the impedance to an appropriate value such that the voltage fed to the antenna is approximately 50% of the voltage fed from the oscillator to the coupling impedance. By this arrangement the detection sensitivity is always kept at an optimum. The system also includes a signal processing apparatus for producing an output signal responsive to a change in the voltage of the alternating current on the antenna exceeding a predetermined level.

Circuit and operation thereof for generating an electrical discharge in the nsec range

Abstract: Circuit and operation thereof for generating an electrical discharge in the nsec range with a steep rise and drop for generating a mechanical surge wave used for comminution of concrements in bodies of living creatures, characterized in that an electrical pulse is applied to an RF cable (1) which leads to an underwater spark gap (6) and is adapted in terms of impedance at the input (2) and the output (4), which electrical pulse flows to the outlet (4), ignites across the spark gap (6), as a result sets the output impedance abruptly to zero, is itself substantially reflected and is destroyed in the input resistor (3).

Voltage controlled resistor

Abstract: A voltage controlled resistor includes an operational transconductance amplifier (OTA) including first and second linearizing diodes which not only optimize signal-to-noise distortion levels but also represent the AC impedance from the inverting input to ground. The OTA turns on and off in response to the amount of gain control current being supplied thereto. A Darlington transistor is coupled to the output of the OTA for providing a low impedance buffered output. A first resistor provides current flow through the diodes. A feedback resistor supplies and controls bias current to one of the diodes. A third resistor maintains bias to the Darlington pair when the OTA output approaches open circuit output impedance conditions.

Automatic gain control circuit for optical receiver and amplifier

Abstract: PURPOSE: To permit use without reference to modulation systems by bringing the output of a preamplifier which amplifies a light input under automatic gain control on the basis of variation in DC component. CONSTITUTION: A light input converted by a photodetector 1" is amplified by a preamplifier 2", whose output is divided through a resistance R" and the drain- source impedance of an FET11". The DC potential VA at this division point is applied to an expander 9" through a resistance R" 2 . Since the output of the expander 9" controls the grid of the FET11", AGC is exercised to compress variation in potential VA at the division point. Therefore, the AC component at the division point also corresponds to the impedance of the FET11" and its variation is compressed to obtanin a stable output signal from an amplifier 10". Thus, the AGC is exercised on the basis of variation in the DC component of the preamplifier output, so the control circuit is usable without reference to modulation systems. COPYRIGHT: (C)1983,JPO&Japio

Heat dissipating device for power amplifier

Abstract: PURPOSE:To control air flow rate and air cool with low noise by controlling the rotating speed of a DC motor in response to the internal impedance value or output of a temperature detector. CONSTITUTION:The temperature of a heat dissiplating unit 2 is detected by a thermistor 3, is compared with a reference power supply 6 by a comparator 7, and a blower 9 is intermittently operated or continuously varied in rotation in response to the result so as to control the air flow rate by a controller 8. Fine air flow level can be obtained under on-off control to determined the power supply 10 at low voltage. It can be considerably increased in continuous control. When the amplifier produces a lower output, the heat dissipating unit can be also lower temperature rise, and a fan 11 can be accordingly rotated at low speed to perform low noise at low output power. At high output time the noise does not relatively become in trouble, but heat dissipation can be increased importantly so that the continuous fan rotating speed may be particularly effective. If the output of the thermistor 5 is lower than the reference voltage 6 during continuous control, the blower 9 is stopped to lower the power supply voltage 10, and when the maximum power is controlled by the controller 8, the noise at low power time is reduced to zero so as to decrease the electric power consumption.