Showing papers on "Rise time published in 1991"

Electrostatic discharge detection and clamp control circuit

Abstract: A switching element is connected to an integrated circuit for shunting an ESD pulse away from the integrated circuit features. A plurality of detection circuits responsive to typical ESD waveform characteristics provide logical control of the switching means. In the preferred embodiment, a NAND gate drives the switching element. The first input to the NAND gate is a first RC network having a first time constant that exceeds the characteristic rise time of the typical ESD pulse, but not the characteristic duration of the typical ESD pulse. The second input to the NAND gate is a feedback loop from the NAND gate output. The feedback loop includes a second RC network having a second time constant that exceeds the duration of a noise pulse, a third RC network having a third time constant that approximates the characteristic duration of the typical ESD pulse, and an inverter between the second and third RC networks. Application of the ESD pulse causes the first input to drive the NAND gate, thus turning on the switching element, and if the ESD pulse is still present when the second time constant is exceeded, the switching means is latched on via the second input until the third time constant is exceeded.

Short pulse microwave source with a high prf and low power drain

Abstract: This invention describes a high voltage, very short pulse, microwave radiating source using low-cost components, and capable of operating at high pulse repetition frequencies (prf). The source is activated by an ordinary video trigger commensurate with driving TTL logic. A trigger will cause a chain of N (where N may be 12 or greater) avalanche transistors connected in a Marx generator configuration to threshold resulting in a 1,200 volt or greater baseband pulse having a rise time of less than 100 ps and a duration of about 3 ns driving the input port of a dipole antenna. The dipole is excited by a balun. This invention achieves very short pulse duration broadband microwave radiation at pulse repetition frequencies as high as 30 kHz or greater.

Temporal processing in the dorsal medullary nucleus of the Northern leopard frog (Rana pipiens pipiens).

Abstract: 1. Single-unit responses to different temporal acoustic parameters were characterized in the dorsal medullary nucleus (DMN) of the Northern leopard frog, Rana pipiens pipiens. Our goal was to provide both a quantitative and a qualitative assessment of the neural representation of behaviorally relevant temporal acoustic patterns in the frog's DMN. 2. Acoustic stimuli included tone bursts having different durations, rise times, or rates of amplitude modulation (AM). Several metrics were used to compute temporal response functions for each of these, including mean spike count, average firing rate, and/or peak firing rate. Synchronization coefficients were also used to characterize responses to stimuli presented at different AM rates. 3. On the basis of mean spike count, the temporal response functions of DMN neurons with respect to signal rise time could be characterized as 1) all-pass, in which the mean spike count was largely independent of rise time, or 2) fast-pass, in which the mean spike count decreased with increasing rise time. Fast-pass response functions were of two types, those that decayed rapidly and those that decayed gradually from their peak values. 4. The minimum threshold varied with signal rise time for cells showing fast-pass but not all-pass response functions. Minimum response thresholds for fast-pass neurons were typically higher with slower signal rise time. 5. The filtering characteristics of cells displaying fast-pass rise time response functions were dependent on signal level, becoming all-pass when signal levels exceeded 30-40 dB above the minimum threshold. 6. Approximately 44% of DMN neurons exhibiting fast-pass response functions for signal rise time showed all-pass filtering characteristics when broadband noise rather than best frequency tones were used, thereby signifying an influence of signal spectrum on the pass-band characteristics of these cells. 7. All DMN neurons, regardless of discharge pattern, showed maximal instantaneous firing rates to signals having short (less than 25 ms) rise times. Response functions based on instantaneous firing rate were, therefore, fast-pass in nature. These responses were independent of signal level and spectrum. 8. There was an ordinal relationship between signal duration and the duration of tonic but not phasic unit discharges. This relationship was not intensity dependent. 9. On the basis of mean spike count, the temporal response functions of DMN neurons with respect to signal duration were characterized as 1) all-pass, in which the mean spike count was largely independent of signal duration, or 2) long-pass, in which the mean spike count increased with increasing signal duration.(ABSTRACT TRUNCATED AT 400 WORDS)

Theory of positive corona in SF/sub 6/ due to a voltage impulse

Abstract: A theoretical examination is made of the mechanism of corona formation for a positive point-plane gap in SF/sub 6/ at 100 kPa. The impulse voltage applied has a rise time of 15 ns and peak value of 200 kV. Seed electrons are released 1 ns after the start of the voltage rise. For a 0.5-cm diameter positive sphere located 6.5 cm from a negative plane, the calculated circuit current initially consists of subnanosecond corona onset pulses, and then the current steadily rises to a maximum, as the voltage reaches a maximum, followed by a rapid fall in current. During the current rise a streamer moves out into the gap along a 100- mu m channel, with the electric field in the streamer trail E>E*, where E* is the critical field where ionization equals attachment. The light output during the discharge is predicted to be a maximum at the anode with only a minor pulse of light at the streamer head, making it hard to detect. After the current maximum, recombination rapidly reduces the numbers of positive ions, negative ions, and electrons, but the net charge density remains constant and thus so does the electric field. The electric field is E approximately E* in the streamer trail, but has a sharp maximum, E>>E* at the head of the streamer trail. The origin of mid-gap precursors, observed when the streamer channel reilluminates after some 100 ns, is attributed to this field maximum in the remnant electric field. The evolution of positive ions, negative ions, and electrons is described by one-dimensional continuity equations, with the space-charge electric fields determined by the disk method. The effects of ionization, attachment, recombination, electron diffusion, and photoionization are all included. New numerical methods allow resolution of the streamer head and the anode fall region to be obtained with a 1- mu m mesh, while following the streamer propagation for approximately 2 cm. >

Optical traffic preemption detector circuitry

Abstract: An optical traffic preemption detector detects pulses of light emitted by an approaching emergency vehicle and provides an output signal which is processed by a phase selector. The phase selector can request a traffic signal controller to preempt a normal traffic signal sequence to give priority to the emergency vehicle. A detector assembly is mounted in proximity to an intersection and can have multiple detector channels. A detector channel can have multiple photocells. Each photocell is provided with a rise time filter. If a detector channel has more than one photocell, the outputs of the respective rise time filters are coupled together. An output of a rise time filter, or coupled rise time filters, is first applied to a current-to-voltage converter and then a band pass filter. The band pass filter isolates a decaying sinusoid signal from a signal representative of a pulse of light. The decaying sinusoid signal is processed to produce a detector channel output signal that has a number of pulses for each pulse of light.

Airborne sound insulation of thick walls

Abstract: Approximate analytical solutions are presented for the transmission of airborne sound through a plate between two rooms. The rooms are placed above each other and are of different size. The area of the plate is larger than the area of either room. Simple formulas are derived from the Euler–Bernoulli plate theory for the transmission due to the forced as well as the resonant field of the plate. The most interesting result concerns the forced response at coincidence, which is shown to be heavily dependent on the size of the excited area. A “rise length” on the analogy of the rise time in a single-degree-of-freedom system is introduced. Within the rise length, which is often very large, the displacement is proportional to the trace length on the plate of the exciting sound ray. The mean transmission factor due to the forced response at frequencies above the critical frequency is for this reason dependent on the source room area, but not on the loss factor. The coupling between a diffuse sound field and the free waves is, on the other hand, loss factor dependent, but the dependence of the coupling on the angle of incidence is shown to be quite different from that in the corresponding case of an infinite plate.

Lead acid battery rejuvenator and charger

Abstract: An electrical power source, either AC or DC, lead acid battery rejuvenator and charger circuit switchable between rejuvenator and charger modes of operation. For the rejuvenator mode of operation a rejuvenator pulse signal generating circuit supplies voltage in the form of fast rise voltage pulses peaking at a voltage necessary to cause battery plate saturation that is 1:1 to 1:3 times the theoretical battery cell voltage. This is accomplished by use of very short duration pulses in the order of 5 micro seconds or less time width wise with extremely fast rise time in the order of 5 mega volts per second rise time with these pulses occurring in approximately the 2,000 to 10,000 times per second frequency range. The transfer of electrons between metal electrode and ions in battery lead acid solution is not instantaneous, and that therefore with the fast rise time pulse rising to 1:1 to 1:3 times battery cell voltage the instantaneous voltage is distributed over entire battery plate surfaces and lead sulphate deposits that have occurred on battery plate surfaces will be released, either going back into the solution or broken up.

Power supply for an ozone generator with a bridge inverter

Abstract: A full bridge switching power supply is coupled to an ozonator load via a series resonant circuit having a resonant frequency above the switching frequency Power output is controlled by varying the duration of the times when diagonal switches are conducting, and the output voltage has a longer rise time than fall time due to there being intervals between the conduction periods of diagonal switches during which one of the switches is turned on to permit resonant current flow The driving voltages for attaining this action are symmetrical rectangular waves of identical shape having different phases that are derived from out of phase pulses where width is varied by the timing of their trailing edges

1.4 ps rise‐time high‐voltage photoconductive switching

Abstract: We report on the generation of 825 V electrical pulses with 1.4 ps rise time and 4.0 ps duration using a pulse‐biased low‐temperature‐grown GaAs photoconductive switch triggered by an amplified femtosecond dye laser. Dependence of the pulse shape on both electric field and optical energy is observed and discussed.

High Gain Photoconductive Semiconductor Switching

Abstract: Switching properties are reported for high gain photoconductive semiconductor switches (PCSS). A 200 ps pulse width laser was used in tests to examine the relations between etectric field, rise time, delay, and minimum optical trigger energy for switches which reached 80 kV in a 50 /spl Omega/ transmission line with rise times as short as 600 ps. Infrared photoluminescence was imaged during high gain switching providing direct evidence for current filamentation. Implications of these measurements for the theoretical understanding and practical development of these switches are discussed.

Excitation mechanisms of oxygen atoms in a low pressure O2 radio‐frequency plasma

Abstract: Using a low‐pressure reactive ion etching reactor in a pulsed radio‐frequency (rf) power mode the rise time of the plasma induced emission of O at 777 and 844 nm was monitored on a ms time scale. With a two‐photon excitation scheme the rise time of the oxygen atom ground state concentration was followed by measuring the laser induced fluorescence (LIF) at 844 nm. An absolute density measurement was performed by comparing the LIF signal in the reactor to the LIF signal of a known concentration of O in a microwave discharge. Using these time resolved measurements the reliability of optical emission actinometry in low pressure O2 rf plasmas for a determination of relative atomic oxygen densities was examined. By comparing the rise times with the ignition time of the plasma it is concluded that both emission lines are caused by dissociative excitation. The consequences for the applicability of actinometry will be discussed. A comparison of experimental emission intensities to calculated ones suggests that highly energetic (e.g., secondary) electrons are responsible for the dissociative excitation of O2.

Simple sub‐50‐ps rise‐time high voltage generator

Abstract: This article relates to the development of an ultrafast (nanoseconds–picoseconds time scale) compact system(s) readily applicable to the field of EMP/radiation, x‐ray‐induced nondestructive testing, plasma fusion (energy) experiments, bioelectromagnetic (food‐drug) sterilization, drivers for x‐ray preionized XeCl laser and similar applications. The present work shows that the Marx and the Pulse forming section can be integrated into a single unit. The stray capacitance present in each stage acts as a peaking capacitor. For a charging voltage per stage of <40 kV, the rise time of the output pulse is below 50 ps at 200 kV into a 100‐Ω load. Work is in progress to extend the voltage amplitude to 1.6 MV while maintaining the relative pulse waveform. With a contemporary optical diagnostic technique it is believed that the present concept may achieve 1–10 ps rise‐time pulses at a megavolt level in ‘‘smart gas mixtures.’’ In addition a solution for the classical peaking circuit has been obtained and presented in...

Liquid crystal control circuit and driving method for liquid crystal panel

Abstract: PURPOSE:To shorten the response time at the rise time of a liquid crystal by comparing and computing the voltage value impressed at present to picture elements and the voltage value to be impressed to the picture elements in the next field and correcting the voltage value CONSTITUTION:The data corresponding to the voltage to be impressed to the liquid crystal subjected to A/D conversion is successively stored into field memories 205 to 207 for every field by a field memory switching circuit 201 A computing element 208 is connected to the field memories 205, 206 by field memory switching circuits 202, 203 and compares and computes the data corresponding to the voltage to be impressed to the same picture elements of the memories A data corrector 209 writes the corrected data to the addresses on the picture elements on the field 206 by the results of the calculation The corrected data is transferred to a D/A converter by successively executing the above-mentioned operation The rise of the liquid crystal, ie the response time is shortened in this way

Substrate with built-in capacitor

Abstract: PURPOSE: To reduce the occurrence of high-frequency switching noise which is generated when logic circuits are simultaneously switched by reducing the inductance between an LSI and a capacitor formed on a substrate. CONSTITUTION: A capacitor is formed so that the inductance between the bonding pad of an LSI mounted on a ceramic substrate 3 and the electrode 7 of the capacitor can be suppressed to 0.05nH. Since the inductance between the LSI and the capacitor is suppressed, the high-frequency component of the noise generated by power supply can be reduced. Therefore, the rise time of signals can be shortened and the operating can be increased. COPYRIGHT: (C)1992,JPO&Japio

LED pulse shaping circuit.

Abstract: An LED pulse shaping circuit (10) capable of providing improved rise time (using current peaking) and fall time (using charge extraction) comprises a conventional differential current switch ( 12, 14, 16) coupled to a pair of switching elements (24,26) and resistance elements (20,22). A first switching element (24) is activated at the beginning of a pulse to provide an initially increased drive current to the LED, depending on the value of a first resistance element (20). The current peaking thus decreases the rise time of the LED. The remaining switching element (26) and resistance (22) are utilized, in conjunction with the differential current switch, to provide a reverse current flow through the LED at the end of the pulse. The charge extraction thus decreases the fall time of the LED.

Microstrip proportional counters for X-ray astronomy

Abstract: Four position sensitive proportional counters will be delivered by the Danish Space Research Institute as focal plane instruments for the Soviet Danish Rontgen Telescope (SODART). These detectors will incorporate the novel microstrip electrode design. This design has been tested with xenon gas and an 55Fe X-ray source. The energy resolution is better than 14% FWHM up to gas gains of 104, the rise time of pulses from X-ray events is fast, 100 ns, allowing for efficient background rejection by rise time analysis. A position resolution of 1 mm FWHM is easily obtained by resistive charge division of the signals from the cathodes and from a wire grid placed in front of the microstrip plate. The detector performs without significant degradation of gain or energy resolution at fluxes exceeding 106/s cm2 and a total dose of 1011 photons.

Rise Time and Center-Frequency Effects on Auditory Brainstem Responses to High-Frequency Tone Bursts

Abstract: The effects of rise time and center frequency on the auditory brainstem response (ABR) elicited by high-frequency tone bursts were examined in six normal-hearing adults. Tone bursts with rise times of 0.1, 0.25, 0.5, and 1.0 msec, duration of 2 msec, and center frequencies of 8, 10, and 12 kHz were used in this study. The absolute latencies of waves I, III, and V were obtained in all subjects, and interpeak intervals of I-III, III-V, and I-V were calculated. As would be expected, rise time significantly affected the absolute latencies of waves I, III, and V, i.e., faster rise times shortened the absolute latencies, but did not affect the interpeak latencies. The tone-burst frequency significantly affected the latency of wave I but not the later waves. No significant differences were found in reliability of the response at different rise times or frequencies, within or across sessions. An estimate of the effective bandwidth of the stimulus suggests that frequency specificity of the response is maintained with fast rise time tone-burst stimuli.

Circuit providing dv/dt immunity

Abstract: A pulse filter (93) is connected between a high voltage level shift circuit (59) which produces output pulses in a pattern determined by an input logic circuit (50-58) and the high side output circuit (94-101) which controls the production of power MOSFET or IGBT gate signals or the like. The pulse filter (93) immunizes the circuit against false operation duo to the fast dv/dt transients. The pulse filter (93) includes inverters for squaring an input signal and a CR delay element for increasing the rise time of the pulse so that pulses derived from transients are too small to drive the following stage and hence blocked. A pulse generator (80) derives set and reset pulses from the logic level of inputs (at 10, 11) and level shifted (at 59). Elements (61-70) relate to low voltage switching circuit. High voltage switching circuit (100, 101) drive power MOSFET's or IGBTs in a load circuit. Detectors (102, 70) prevent operation when supply voltage is low.

Effects of Noise Burst Rise Time and Level on the Human Brainstem Auditory Evoked Response

Abstract: An experiment was conducted to examine the effects of noise burst rise time and level on the human BAER. Noise burst levels included 15, 30, 45 and 60 dB nHL, with linear rise times of 0, 0.5, 1.25 and 2.5 ms. With increasing noise burst level, there is a decrease in wave V latency and an increase in peak amplitude. With increasing noise burst rise time, there is an increase in wave V latency and a decrease in wave V amplitude. The slope of the latency/intensity function increases with increasing rise time. The slope of the latency/rise time function increases with decreasing noise burst level. The change in wave V latency associated with changing rise time is less than the change in rise time for all experimental conditions.

Multi-mode resonant gradient coil circuit for ultra high speed NMR imaging

Abstract: A multi-mode resonant gradient circuit is described for use in ultra high speed imaging techniques like echo-planar and echo-volumar imaging. The circuit behaves overall in a series resonant manner, but at a fixed number of discrete frequencies. By choosing the number of resonant modes, the circuit can be used to generate approximations to a square wave or a trapezoidal waveform. It it shown that trapezoidal waveforms of a given rise time may be described by a more convergent series expansion involving fewer harmonic components. Because the circuit exploits energy conserving principles, much faster current rise times can be achieved with a given driver amplifier and gradient coil than can be achieved by direct coil drive. Expressions are given for the choice of passive circuit components required to accommodate all odd harmonics up to seventh order.

Simple modification of Varian E‐line microwave bridges for fast time‐resolved EPR spectroscopy

Abstract: Modification of the popular Varian E‐line series of electron paramagnetic resonance (EPR) spectrometers for fast direct detection EPR spectroscopy is described. The overall time response and signal reproducibility of the spectrometer is improved by changing the values of two capacitors in the microwave bridge preamplifier circuit, with no alteration of instrument performance in normal field‐modulated experiments. The rise times are slew rate limited for large input signals. There is a propagation delay of 40 ns before any preamplifier response is observed. Signal‐to‐noise ratios for the direct detection EPR experiment with the modified and unmodified bridges are comparable. A test of the modified bridge using a biradical, formed within 20 ns by laser flash photolysis, shows a signal decay consistent with that measured by optical methods, in contrast to the unmodified circuit. Other factors influencing the time response of the experiment are discussed. While the preamplifier rise time is still the limiting factor, spectra as close as 70 ns to the laser flash can now be measured with adequate signal‐to‐noise ratios.

An electron‐impact ionization time‐of‐flight mass spectrometer using a simple high‐voltage square pulse generator

Abstract: A versatile electron‐impact time‐of‐flight mass spectrometer (EI‐TOFMS) in a pulsed molecular beam has been constructed. The instrument contains a fast rise time, square pulse generator, biased at high voltage, which simplifies the implementation of EI‐TOFMS. Power field effect transistors are used as the active switching element, which afford compact size and simplified circuit construction. The effect of the shape of the repelling pulse on the flight time and space focusing condition is estimated by numerical calculation. Preliminary test results are provided for pulsed molecular beams of ammonia and hydrogen iodide.

Microwave pulse compression from a storage cavity with laser-induced switching

Abstract: A laser-induced switch and a multiple cavity configuration are disclosed for producing high power microwave pulses. The microwave pulses are well controlled in wavelength and timing, with a quick rise time and a variable shape and power of the pulse. In addition, a method of reducing pre-pulse leakage to a low level is disclosed. Microwave energy is directed coherently to one or more cavities that stores the energy in a single mode, represented as a standing wave pattern. In order to switch the stored microwave energy out of the main cavity and into the branch waveguide, a laser-actuated switch is provided for the cavity. The switch includes a laser, associated optics for delivering the beam into the main cavity, and a switching gas positioned at an antinode in the main cavity. When actuated, the switching gas ionizes, creating a plasma, which becomes reflective to the microwave energy, changing the resonance of the cavity, and as a result the stored microwave energy is abruptly switched out of the cavity. The laser may directly pre-ionize the switching gas, or it may pump an impurity in the switching gas to an energy level which switches when a pre-selected cavity field is attained. Timing of switching the cavities is controlled by varying the pathlength of the actuating laser beam. For example, the pathlengths may be adjusted to output a single pulse of high power, or a series of quick lower power pulses.

Driving method and liquid crystal control circuit for liquid crystal panel

Abstract: PURPOSE:To shorten the response time to attain a target transmission quantity by setting the absolute value of the voltage to be impressed to an arbitrary picture element in the 2n(n is an integer)th field at the value smaller than the absolute value of the impressed voltage in the (2n-1)th field at the time of driving the active matrix type liquid crystal panel. CONSTITUTION:A brightness signal is subjected to a gain adjustment so as to meet the modulation range of a liquid crystal, then to double speed conversion by a scan converter 201. The converted voltage data is corrected by a correcting circuit 203 by which the response time of the liquid crystal is improved. The absolute of the voltage of this time is corrected in an increasing direction and is converted by a D/A converter 205 to an analog signal, thereby a reference voltage is outputted from a voltage generating circuit 103. The signal converted to a double speed in a switching circuit 104 and the reference voltage are switched in the middle of one field and the resulted signal is inputted to a phase splitting circuit 105 by which the two signals of a positive polarity and a negative polarity are obtd. These signals are thereafter applied to picture elements, by which the rise time of the liquid crystal is shortened and the tailing of the picture elements is eliminated.

Led pulse shaping circuit

Abstract: An LED pulse shaping circuit is disclosed which is capable of providing improved rise time (using current peaking) and fall time (using charge extraction). The pulse shaping circuit consists of a conventional differential current switch coupled to a pair of switching elements and resistance elements. A first switching element is activated at the beginning of a pulse to provide for an initially increased drive current to the LED, the value of a first resistance element used to determined the level of the increased drive current. The current peaking thus results in decreasing the rise time of the LED. The remaining switching element and resistance are utilized, in conjunction with the differential current switch, to provide a reverse current flow through the LED at the end of the pulse. The charge extraction thus results in decreasing the fall time of the LED.

Development of ferrite line pulse sharpeners for repetitive high power applications

Abstract: Pulse sharpening using ferrite material was first noticed in the mid-fifties during the development of storage devices for telecommunication and computer systems. Since that time various workers have explained how a switched ferrite can change the propagation characteristics of a transmission line to improve the rise time of an input pulse. In the paper the advantages achievable by imposing electron spin resonance and subsequent frequency enhancement, which has greatly improved the performance of these lines, are described for the first time. Experimental evidence of the benefits of spin conditions is provided and a simple transmission line model introduced to simulate the pulse sharpening effects.

Thin-film pulse propagation analysis using frequency techniques

Abstract: High-speed pulse (rise time=100 ps) propagation in a thin-film multichip package is analyzed. The thin-film lines are assumed to be 8 mu m wide, 4 mu m thick, 12 mu m above the ground, and made of copper embedded in a dielectric medium with a dielectric constant of 3.5 (e.g., polyimide). Weeks' algorithm is used to calculate the wideband line characteristics which include the skin effect of conductors and the proximity effect of the ground up to a frequency of 10 GHz. It is assumed that the dielectric imperfection and the conductor surface roughness are negligible. An inverse fast Fourier transform (FFT) algorithm is used to obtain the time-domain results. Line lengths studied ranged from 1 to 15 cm. and three types of terminations are treated: parallel, series, and open. Termination strategy for different line lengths is presented. The maximum line length allowable in the thin-film conductor system is then examined. Finally, crosstalk at various locations of the quiet lines with different terminations is discussed. >

Study of picosecond rise time in human-generated ESD

Abstract: Measurements of human-generated electrostatic discharge (ESD) were conducted during the Canadian winter under low humidity conditions. These measurements indicate the existence of ESD impulses with rise times shorter than 100 ps and peak current amplitude in excess of 50 A. The measuring system consisted of a current sensor with a calibrated bandwidth of 5 GHz and a TEK 7250 digitizer with numerically corrected bandwidth of 10 GHz. A bare hand, a blunt object (screwdriver), a sharp object (scriber), and a car key were used during the test. >