Showing papers on "Rise time published in 1999"

Figures of merit to characterize the importance of on-chip inductance

Abstract: A closed-form solution for the output signal of a CMOS inverter driving an RLC transmission line is presented. This solution is based on the alpha power law for deep submicrometer technologies. Two figures of merit are presented that are useful for determining if a section of interconnect should be modeled as either an RLC or an RC impedance. The damping factor of a lumped RLC circuit is shown to be a useful criterion. The second useful figure of merit considered in this paper is the ratio of the rise time of the input signal at the driver of an interconnect line to the time of flight of the signals across the line. AS/X circuit simulations of an RLC transmission line and a five section RC II circuit based on a 0.25-/spl mu/m IBM CMOS technology are used to quantify and determine the relative accuracy of an RC model. One primary result of this paper is evidence demonstrating that a range for the length of the interconnect exists for which inductance effects are prominent. Furthermore, it is shown that under certain conditions, inductance effects are negligible despite the length of the section of interconnect.

Reliable, modular, production quality narrow-band high rep rate F2 laser

Abstract: The present invention provides a reliable modular production quality excimer laser capable of producing 10 mJ laser pulses in the range of 1000 Hz to 2000 Hz or greater. Replaceable modules include a laser chamber (211); a pulse power system comprised of three modules; an optical resonator comprised of a line narrowing module (206) and an output coupler module (216); a wavemeter module (213), an electrical control module (205), a cooling water module (203) and a gas control module (202). Improvements in the pulse power unit to produce faster rise time and improved pulse energy control include: sn increased capacity high voltage power supply with a voltage bleed-down circuit for precise voltage trimming, an improved commutation module (209) that generates a high voltage pulse from the capacitors charged by the high voltage power supply (20) and amplifies the pulse voltage 23 times with a very fast voltage transformer having a secondary winding consisting of a single four-segment stainless steel rod. The compression head (207) saturable inductor greatly reduces the quantity of oil required and virtually eliminates the possibility of oil leakage.

Time Course of Individual Ca2+ Sparks in Frog Skeletal Muscle Recorded at High Time Resolution

Abstract: Discrete Ca2+ release events (Ca2+ “sparks”) were recorded in cut segments of single frog skeletal muscle fibers using a video-rate laser-scanning confocal microscope operating in line-scan mode (63 μs per line). Fibers loaded with the Ca2+ indicator fluo-3 were voltage clamped at a holding potential of 0 mV, briefly reprimed at −90 mV, and then strongly depolarized with a large test pulse to activate any reprimed voltage sensors. Using this high time resolution system, it was possible to record individual Ca2+ sparks at ∼30-fold higher time resolution than previously attained. The resulting new experimental data provides a means of characterizing the time course of fluorescence during the brief (a few milliseconds) rising phase of a spark, which was not possible with the previously used 1.5–2 ms per line confocal systems. Analysis of the time course of individual identified events indicates that fluorescence begins to rise rather abruptly at the start of the spark, continues to rise at a slightly decreasing rate to a relatively sharp peak, and then declines along a quasi-exponential time course. The mean rise time of 198 sparks was 4.7 ± 0.1 ms, and there was no correlation between rise time and peak amplitude. Average sparks constructed by temporally and spatially superimposing and summing groups of individual sparks having similar rise times gave a lower noise representation of the sparks, consistent with the time course of individual events. In theory, the rising phase of a spark provides a lower bound estimation of the time that Ca2+ ions are being released by the sarcoplasmic reticulum Ca2+ channel(s) generating the spark. The observed time course of fluorescence suggests that the Ca2+ release underlying a spark could continue at a fairly constant rate throughout the rising phase of the spark, and then stop rather abruptly at the time of the peak.

Two-dimensional simulation of plasma-based ion implantation

Abstract: A particle-in-cell simulation is used to study the time-dependent evolution of the potential and the electrical field surrounding two-dimensional objects during a high voltage pulse in the context of plasma immersion ion implantation. The numerical procedure is based on the solution of Poisson’s equation on a grid and the determination of the movement of the particles through the grid. Ion current density, implanted concentration, average impact energy, and impact angle of the ions were calculated using this method for two geometrical shapes, a square and an L-shaped object. The nonuniformity of the sheath potential near convex and concave corners is shown. The divergence of the electrical field in the vicinity of corners leads to dramatically reduced concentration of the incident ions. The simulation also shows that a large ion flux hits the surface during the rise time of the pulse. Directly after the rise time, more than 40% of the whole concentration is implanted. Hence, the average impact energy of t...

Dynamics of incomplete ionized dopants and their impact on 4H/6H-SiC devices

Abstract: The influence of incomplete ionization of dopants in 4H/6H-SiC on transient device behavior has been investigated numerically based on a self-consistent solution of the coupled system of Poisson's equation, the continuity equations of electrons and holes, and balance equations for each donor or acceptor level. If the rise time of a reverse bias pulse is equal or smaller than the characteristic ionization time constant, a dynamically enlarged extension of depletion regions is obtained which can result in a dynamic punchthrough (PT) within back-to-back junction configurations. The respective time constants of nitrogen (N), aluminum (Al), and boron (B) mere measured as functions of temperature in 4H- and 6H-SiC using thermal admittance spectroscopy (AS) and deep level transient spectroscopy (DLTS). At room temperature, for instance, we obtained 60 ps/2 ps, 300 ps/10 ps, and 100 ns/100 ns for N (cubic site), Al, and B in 4H/6H-SiC, respectively. As the time constants of N and Al are small, transient incomplete ionization turns out to be negligible, at least within today's high-power device operation areas. Boron, on the other hand, influences significantly the dynamic device characteristics. In order to demonstrate the implications of these effects, numerical device simulations of a 6H-SiC double-implanted MOSFET and a 4H-SiC thyristor were performed. These simulations allow a detailed analysis of the transient device behavior and the onset of dynamic PT which strongly depends on temperature, structure parameters, and the external excitation.

Time resolved Kerr microscopy: Magnetization dynamics in thin film write heads

Abstract: We have used a scanning Kerr microscope set-up with picosecond time resolution and sub-micron spatial resolution to directly measure the flux response in magnetic recording heads. The data rate limiting factor of a write head, which is the flux rise time at the gap, has been measured for different geometries and head materials in polar Kerr mode. Flux propagation in the yoke, which is governed by a combination of wall displacement and magnetization rotation, has been studied by one dimensional and two dimensional time response measurements utilizing the longitudinal Kerr effect. The local flux time response in the head was correlated to the respective micromagnetic structure as determined by static wide-field Kerr imaging. In addition to the intrinsic magnetic properties we have also studied the flux time response by looking at the system properties of the head/write-electronic and, by using a voltage source for excitation, information about classical eddy-current effects for different pole geometries have been derived. Further, non-stationary effects in the flux reversal process are shown to produce non-linearities in the response at the write gap which are contributing to non-linear transition shift in the write process.

High pulse rate pulse power system with fast rise time and low current

Abstract: A high pulse rate pulse power source for supplying controlled high energy electrical pulses at rates of 2000 Hz or greater. The source includes a pulse generating circuit including a charging capacitor, a solid state switch and a current limiting inductor. Pulses generated in the pulse generating circuit are compressed in at least two pulse compression circuits and a step-up pulse transformer increases peak voltage to at least 12,000 volts. A very fast regulated power supply is provided for charging the charging capacitor in less than 400 microseconds and a pulse control system including a programmed processor controls the charging of the charging capacitor to an accuracy of less than about one percent at a rate of at least 2000 charges per second.

Scanning and impedance properties of TEM horn arrays for transient radiation

Abstract: A general concept for ultrawide-band array design using interconnected transverse electromagnetic (TEM) horns is described. At high frequencies (wavelength small compared to unit cell dimensions), the mutual coupling between elements is small and, consequently, the input impedance depends only on the lattice dimensions and not on either scan angle or frequency. At low frequencies (wavelength large compared to unit cell dimensions), the mutual coupling is purposefully made large, by interconnecting the elements to maximize the low-frequency performance. This paper presents the results of analyses using a periodic hybrid finite-element approach to calculate input impedance and scanning performance of generic TEM horn arrays. The limiting case, the planar bicone, is shown to have the frequency-independent property of a self-complementary antenna, making it a useful case for establishing the effects of feed region geometry. Although it radiates bidirectionally, it has the interesting property that its broadside-scan frequency response in the array environment is absolutely flat up to the grating lobe onset limit. A TEM horn array is more unidirectional, but as a consequence suffers both oscillatory variations in the input impedance with frequency and increased limits on minimum achievable rise time.

Accurate determination of pulsed current waveform in plasma immersion ion implantation processes

Abstract: This article reports on the measurement of the ion current in plasma immersion ion implantation. Our simulation results indicate that the total current peaks at the end of rise time of the applied voltage. However, our experimental data acquired using a Rogowski coil and digital oscillator show the highest current at the beginning of the voltage pulse. The discrepancy can be explained by a displacement current attributable to the changing voltage, sheath capacitance, circuit loading effects, as well as secondary electron emission.

Long-lived explosive-emission cathode for high-power microwave radiation generators

Abstract: The operation of cold explosive-emission cathodes having a current density of ∼104 A/cm2, fabricated using various materials, was investigated under a large number of switching cycles. The cathode voltage was ∼500 kV, the maximum current ∼5 kA, and the pulse duration ∼20 ns. It is shown that when the number of switchings is small (⩽103 pulses), cathodes having similar geometry exhibit similar emission properties. For most of the materials studied, as the number of switching cycles increases (⩾103 pulses), the current rise time increases (as far as the pulse duration) and the maximum vacuum diode current decreases. When a graphite cathode was used, the maximum current remained unchanged up to 108 switching cycles. The mass removed from the cathode was determined for various materials. The results were used to achieve continuous operation of a relativistic 3 cm backward-wave tube having an output power of 350–400MW and an almost constant power level during 108 pulses at a repetition frequency of 100–150 Hz.

System and method for approximating the coupling voltage noise on a node

Abstract: The present invention is generally directed to a system and method for approximating the coupling cross- a node in a circuit and determining whether the coupling voltage noise exceeds a permissible value. In accordance with one aspect of the invention, a method uses a first circuit model to obtain a total resistance value of a conductor extending between a driver configured to drive the node and a receiver, and uses a second circuit model to determine a total capacitance. The method also determines an aggressor coupling capacitance between the node and an aggressor signal using at least one criteria, and computes a ground capacitance by subtracting the aggressor coupling capacitance from the total capacitance. The method also determines the effective resistance of the driver, and a weighted average rise time for all aggressor signals on the node. Using a third circuit model, with the values determined above, the method simulates the third circuit model to determine whether the coupling voltage noise of the node exceeds a predetermined value.

Impluse response of a fiber optic probe hydrophone determined with shock waves in water

Abstract: The impluse response of a fiber optic probe hydrophone (FOPH) is determined through it’s step response obtained by using a self-focusing electromagnetic shock wave excitation. The experimental transfer function agrees well with the theoretical calculation of the transient response by diffraction of the acoustic wave at the fiber end face. A rise time of about 5 ns has been obtained for the shock front of the self-focusing shock wave generator by the deconvolution of the output signal of the hydrophone with it’s impulse response. The FOPH can be used as a standard hydrophone for the absolute wideband measurement of shock waves of lithotripters and of acoustic waves in liquids in general.

0.75 MA, 400 ns rise time LTD stage

Abstract: The LTD stage with following parameters was designed and tested: stored energy 14 kJ, output voltage 90 kV, current amplitude in secondary turn 0.75 MA, current rise time /spl sim/430 ns. The stage could be used as a base unit in generators driving PRS Z-pinch loads as well as in high current e-beam accelerators. As a storage elements the IK-100-0.17 capacitors are used, designed and produced by PKB of Electrohydraulics, Nikolaev, Ukraine. The multi channel, multi gap spark switches in air without of overpressure connect the capacitors to the stage circuit. The electrodes of the switch are made of a cylindrical spring, providing inductive insulation between the neighboring spark channels. A special scheme is developed for triggering the switch with large surface of the electrodes.

Method and apparatus for programmable adjustment of computer system bus parameters

Abstract: A system for programmatically adjusting electrical characteristics of a bus interface so as to modify bus operating and signaling parameters employs a control module or mechanism, responsive to a digital signal, for setting the characteristic's value. The electrical characteristic can be a voltage determinative, for example, of any of the following bus operating and signaling parameters: driver output rise time, driver output fall time, driver voltage limits, driver propagation time, receiver threshold voltage levels, or termination resistance. The digital signal can be generated, for example, by a computer-executable program, a controller, or other such device, that applies the digital signal to the control mechanism, for example, via a JTAG interface/controller.

Current-controlled output buffer

Abstract: A current-controlled output buffer circuit includes a control circuit (110), a charging circuit (120), and a discharging circuit (150). The control circuit is configured to receive a control signal (102), and in response produces a charging signal (106) and discharging signal (108). The charging circuit is configured to receive the charging signal and in response, supplies a charging current to an output terminal, the magnitude of the charging current producing a signal rise time. The discharging circuit is configured to receive the discharging signal and in response, sinks a discharging current from the output terminal, the magnitude of the discharging current from producing a signal fall time.

Performance limitations in the feedback control of a class of resonant systems

Abstract: There has been a large literature on the feedback control of flexible and resonant systems. Such systems arise naturally when system weight and or response speed issues push designers toward lighter, faster structures for a range of mechanical systems. Feedback control of such systems is often proposed to ameliorate the effects of the resonance. We investigate the extent to which the dynamic structure of a simple class of resonant systems limits the achievable feedback control performance for such systems. It turns out that in the class of systems considered, there is a trade off between three common control objectives, namely: (i) good initial transient response (that is the absence of large overshoot or undershoot in the initial rise time), (ii) fast response, (iii) good settling behaviour (that is, the absence of very slow modes in the step response).

Super-Resolution Effect of Semiconductor-Doped Glass

Abstract: Semiconductor-doped glass is proposed as a super-resolution layer for future ultra-high-density optical disc systems. It was confirmed that this material system showed very fast response and large transmittance change by laser-beam irradiation when CdSSe-doped glass was used. The rise time of the transmittance change was less than 10 ns and the transmittance change reached 30%. These optical responses were obtained at a power density of the pumped laser beam of 1 MW/cm2. This power density corresponds to the readout power in digital versatile disk-read only memory (DVD-ROM) and digital versatile disk-random access memory (DVD-RAM) discs. This material system is regarded as a potential candidate for a super-resolution readout layer that is applicable to both ROM and RAM discs.

Pulsed fiber laser using micro-electro-mechanical mirrors

Abstract: Two different types of micromirrors are integrated with a fiber laser to modulate the cavity Q-factor. Both systems operate at frequencies up to 60 kHz and generate a pulse peak power 100 times higher than the continuous emission. We simulate the emitted pulses and find a good agreement with the measured value for the period of relaxation oscillations. The simulations also show the necessity of a shorter rise time of the Q-factor modulation to achieve one single giant and narrow Q-switched pulse.

High voltage pulse generator

Abstract: A high voltage pulse generator provides a short, fast rise, high voltage pulse from a very low impedance suitable for initiating high energy electrical discharges in liquids and high pressure gases. Its low impedance allows extremely high currents from external energy storage capacitors to be conducted through the invention once the invention has initiated an arc. Its fast rise time is suitable for initiating multiple arcs or even sheet surface discharges in high pressure gasses under suitable conditions.

Idealized model for charged device electrostatic discharge

Abstract: An analysis is presented for a two-conductor problem in which the source conductor, a sphere with either constant charge or constant potential, approaches a ground plane. Capacitance coefficients are calculated; body potentials, energies, and charges are compared for typical geometries using the two models. In real charged device model events, the device potential and probability of discharge are a function of the charge on the device, its size, and position relative to a ground plane. Proposed test methods specify the potential of the device; the resulting charge on the device and the energy dissipated in the discharge can be lower compared to the actual event. Results are also presented which show the effect of the variation in the impedance elements of the discharge path on the peak value and rise time of the discharge current.

Prolongation of the rise time of the compression wave generated by a high-speed train entering a tunnel

Abstract: An analysis is made of the large–amplitude compression wave formed when a high speed train enters a tunnel whose entrance is ‘vented’ by perforations in the tunnel walls The vents are designed to increase the rise time of the wave in order to alleviate shock formation in a long tunnel by progressive nonlinear steepening of the wavefront The wave emerges from the far end as an impulsive ‘micro–pressure wave’, and the presence of shocks increases its propensity to cause significant structural damage and environmental annoyance Detailed predictions are given for a ‘tunnel’ consisting of a thin–walled circular cylinder, of the type frequently used in model–scale experiments A finite length of the cylinder entrance is perforated with an axisymmetric distribution of circular apertures The apertures are equivalent to a distribution of sources, and it is shown that the profile of the compression wavefront can be greatly extended, so that the wave amplitude increases smoothly and linearly, by ‘shading’ the aperture distribution to make the effective source strengths approximately uniform along the perforated zone The maximum compression wave rise time that can be obtained by this means is equal to the time of passage of the front of the train through the perforated section

Method and circuit arrangement for automatically parameterizing a quick-acting digital speed control loop

Abstract: A filter module inserted into a speed control loop to shorten the rise time of the loop. The filter parameters of the filters provided in the filter module and the controller parameters are calculated in such a way that instances of resonant rise. The amplification factors for the proportional controller branch and the integral controller branch are increased, which leads to a shorter rise time.

90 kV 1800 A 85 ps rise time electromagnetic shock line for UWB applications

Abstract: A ferrite-loaded coaxial line has been developed for operation with axial magnetic field bias at a 100 kV input pulse voltage. Output rise times of 85 ps are obtained at 90 kV into a 50 /spl Omega/ load. These results confirm that rapid shock wave switching based on the stimulation of damped gyromagnetic precession can be effectively exploited in relatively large diameter beads as a means of obtaining <100 ps rise times at high pulse voltages.

Limiting excitation of unmodeled high modes with negative input shapers

Abstract: Vibration of flexible structures can be greatly reduced by using properly shaped reference commands. Input shaping is a command generation scheme that filters the reference command in real time by convolving it with a sequence of impulses, called the input shaper. The resulting shaped command has a slower rise time than the unfiltered command. The rise time is increased by the time duration of the input shaper, so it is desirable to keep the duration as short as possible. To achieve very short durations, the shaper must contain negatively valued impulses. The improved rise time of negative input shapers comes with the potential drawbacks of actuator saturation, increased sensitivity to modeling errors, and excitation of unmodeled high modes. A method for controlling the potential excitation of unmodeled high modes is presented. Characteristics of the impulse sequence as a function of the limitation on high-mode excitation are presented. Simulations of a linear system with unmodeled high modes are used to demonstrate the important features of this approach.

Testing leak tightness of sensor containing oscillating component by forming quotient of deflection amplitudes, gradient of phase curve or rise time of sensor output signal

Abstract: The method involves exciting the oscillating component by subjecting it to a sequence of different frequencies, one of which is the resonant frequency of the component. An indication of the leak tightness is obtained by forming the quotient of signal values representing the deflection amplitudes of the component, or by determining a signal value corresponding to the gradient of a phase curve. To determine the phase curve at the different frequencies that lie in the range of the resonant frequency of the component, a phase detector is used to provide signals corresponding to the phase shifts. Alternatively, the rise time of the sensor output signal is determined. An Independent claim is included for an apparatus for testing the leak tightness of a sensor.

A measurement of very fast transition durations due to gap discharge in air using distributed constant line system

Abstract: Very fast transition durations (rising time in positive polarity and falling time in negative polarity) due to starting of gap discharge were investigated in time domain. The gap space was set very small for voltages below 1500 V as a simulation of the charged device model (CDM) electrostatic discharge (ESD) and the gap discharge of switch devices. The measurement system consists of a distributed constant line system with a tapered coaxial electrode, which has a matched impedance for the characteristic impedance of the distributed constant line system. The insertion loss of the tapered coaxial electrode was within -3 dB in the frequency range below 4.5 GHz. The atmosphere around the electrode is ordinary air. This experimental system enables one to measure the high-speed transients of about 100 ps due to gap discharge in time domain. As a consequence of the experiment, the relationship between the discharge voltage and transition duration was confirmed. The voltage rise time was slowed down gradually in positive polarity, while the voltage fall time was slowed down remarkably in negative polarity for the 0.1-mm needle.

Driving circuit of magnetic impedance effect element

Abstract: PROBLEM TO BE SOLVED: To reduce consumption power, eliminate difference of detection sensitivity which is due to the direction of an external magnetic field, and simplify structure. SOLUTION: This driving circuit is provided with a magnetic impedance effect element 5, an element driving circuit 3 applying a driving pulse to the element 5, a detection coil 10 wound around the element 5, a first sample-hold circuit 11 and a second sample-hold circuit 12 which hold a voltage detected by the detection coil 10, and a differential amplifier 9 outputting a voltage of difference between a voltage held by a first sample-hold circuit and a voltage held by the second sample-hold circuit 12. The detection coil 10 detects a voltage whose polarity is reverse at the rise time and the fall time of the driving pulse. A voltage of one polarity is held by the first sample-hold circuit 11, and a voltage of the other polarity is held by the second sample-hold circuit 12.

An 8 channel GaAs IC front-end discriminator for RPC detectors

Abstract: Although not traditionally considered for particle detector readout, circuit solutions based upon GaAs IC technologies can offer considerable performance advantages in high speed detector signal processing: high f T devices, such as the GaAs MESFET, allow the realization of front-end tuned amplifiers and comparators with the same detector time resolution. Such a feature is well-suited for RPC particle detectors, characterized by short pulse duration and constant shaping responses. A new design procedure shows the suitability of high speed narrow band GaAs amplifiers as voltage-sensitive input stages of front-end discriminators to perform the required voltage amplification for the following comparator, ensuring, at the same time, SNR optimisation, high gain and low power consumption. As an application of the proposed approach, a full-custom analog chip has been designed and realized using 0.6 μm GaAs MESFET technology from Triquint foundry. Eight channels of a front-end discriminator composed of a tuned voltage preamplifier followed by a high speed comparator have been realized with a resulting die size of 1.5×2.3 mm 2 . The chip turns out to be very stable, featuring high voltage gain (>1000), high gain-bandwidth product (10 11 ) and low sensitivity (∼50 μV), fast rise time (1.5 ns) and a power consumption of 25 mW per channel. It has been successfully tested as front-end stage in RPC trigger detectors.

A 6 kV–150 A, 8 ns rise time pulse generator for excitation of ferroelectric cathodes

Abstract: A pulse generator with the following characteristics is presented: the voltage ranges in the interval 0.1–6 kV, the maximum delivered current is 150 A, the pulse length ranges within the interval 100–300 ns, the rise time and the decay times are, respectively, 10 and 25 ns on 50 Ω resistive load and the repetition rate is higher than 1 MHz. The circuit has a source capacitor of 10 nF charged at the needed voltage, the capacitor feeds the load through a parallel of two fast and high voltage solid state switches. The nanosecond rise time and the square fashion of the pulse have been accomplished arranging all the components in cylindrical symmetry. A bipolar pulse is obtained coupling two circuits with opposite polarity.