Showing papers on "Rise time published in 1986"

Stimulus rise time, intensity, and bandwidth effects on acoustic startle amplitude and probability

Abstract: The amplitude and probability of periorbital EMG responses were assessed for a variety of stimuli. In Experiment 1, 50-ms duration broadband noise (20–20K Hz) and tones (1000 Hz), at 95 and 100 dB(A), with rise/fall times of 2.5, 10, and 25 ms, were presented. Noise stimuli were more effective than tones for both response amplitude and probability. Stimulus intensity affected both measures for tones, but only response amplitude for noise. Increasing stimulus rise/fall time had no significant effect for noise, but resulted in lower probability for tones. In Experiment 2, 50-ms duration 1000 Hz tones, at 98 and 102 dB(A), with rise/fall times of 1, 2.5, 5, and 10 ms were presented. Response amplitude was not affected by rise/fall time changes, but increasing rise/fall time from 5 to 10 ms resulted in lower probability. These data show that the startle response can reflect manipulations of stimulus bandwidth, intensity, and rise/fall time, and that startle amplitude and probability reflect these manipulations in different ways. The two response measures may indicate the activity of partially independent underlying mechanisms, with a startle “trigger’ determining response probability and a startle “amplifier’ determining response amplitude for suprathreshold stimuli.

Frequency modulated (FM) time delay photoacoustic and photothermal wave spectroscopies. Technique, instrumentation, and detection. Part II: Mirage effect spectrometer design and performance

Abstract: FM time delay laser excitation has been implemented in a photothermal deflection spectrometric apparatus with fast rise‐time optics. The performance of the system was studied in both frequency and time delay domains. The spectrometer was further used in the study of thin quartz layers on an opaque substrate. In this work we have demonstrated the operation of the first frequency modulated (FM) time delay photothermal deflection (mirage effect) spectrometer with a ns rise time spectrally flat beam position detector unit. It was established by use of a blackbody reference that the spectrometer is responsive to impulsive heat sources in the sample with no measureable instrumental distortion of the frequency or time delay domain responses. The sensitivity of the device was tested successfully in the measurement of thermal parameters of thin quartz layers on absorbing backings. It was further shown that our spectrometer is sensitive to thin SiO2 layers on Si wafers. The data were largely consistent with Green’s...

Prepulse suppression in microwave pulse-compression cavities

Abstract: It is possible to generate high‐power microwave pulses with fast rise time by using resonant cavities to obtain power gain from pulse compression. In the usual case, especially when normal‐conducting cavities are used, the principal output pulse from a pulse‐compression device is preceded by a precursor signal that may be only 40 dB below the main pulse. For some applications this large a prepulse is unacceptable. We have developed a prototype normal‐conducting, x‐band, pulse‐compression cavity in which the prepulse is suppressed by more than 70 dB. When this cavity is driven by a 20‐kW source, output pulses with 200‐kW peak power, 5‐ns pulse width, and sub‐nanosecond rise time can be obtained. We have also built an s‐band cavity that has produced pulses of 5‐ns width, 200‐MW peak power, and under 3‐ns rise time. The s‐band cavity is typically driven at 5–10 MW and has a prepulse that can be more than 80 dB below the peak of the main pulse.

Transient Analysis of Single and Coupled Lines with Capacitively-Loaded Junctions

Abstract: Transient processes are studied for a single line or a pair of coupled lines consisting of line sections with different characteristic admittances and with capacitances loaded at the junctions of line sections. Equations for the Laplace transform of the reflection and transmission coefficients of single and coupled lines are derived for the general case. When the capacitances are loaded at regular intervals, the corresponding expressions of the transient response waveforms at different terminal ports of these lines for both a step and a ramp input are developed. Based on the theoretical analysis, we illustrate the transient responses to ramp signals on some simplified computer signal lines, such as parallel-plate lines with transverse ridges, and parallel striplines with perpendicular crossing strips sandwiched between common upper and lower ground planes. The numerical results suggest that signals with a rise time of t/sub r/<50 ps will cause too much distortion, and should not be used when the length of the line is longer than 2 cm.

High-speed CdS 0.2 Se 0.8 photoconductor and its application to line-image sensors

Abstract: The photoelectric properties of CdS 1-x Se x (x = 0.4-1.0) photoconductor-type sensors were measured. The sensors were made by heat-treating an evaporated film under the influence of CdCl 2 vapor. The photocurrent J p is large, and the dark current J d is small; the S/N ratio derived from the J_{p}/J_{d} ratio reaches a value of more than 60 dB. With increasing x , the decay time of the photocurrent decreases, while the rise time increases. By addition of continuous light bias, the rise time is drastically reduced. Furthermore, the decay time is reduced by increasing the applied voltage. These effects are pronounced for a CdS 0.2 Se 0.8 sensor. Using this sensor, we constructed a contact-type line-image sensor (8 bits/mm, 1728 bits), and attained a scanning rate of 1 ms/line and a total time of about 2 s for reading an ISO A4 size document. The reading was performed under an application of 20 V, and an illumination of 7.5-µW/cm2light bias and 15 µW/cm2(∼100 lux) signal light using LED light sources (570 nm).

Optical correlation measurement of switching transients in high-speed semiconductor lasers

Abstract: Measurement of the large-signal transient response of a high-speed InGaAsP laser to an ultrashort rise time current pulse is reported. For complete time resolution, a measurement system which uses optical correlation techniques is implemented. Comparison is made between the optical correlation measurement and conventional electronic measurement using the fastest available detector and oscilloscope.

Magnetic head driving circuit

Abstract: PURPOSE:To shorten sufficiently the rise time of a current and to cause a driving power to be sufficient even when it is small by turning alternately on and off two switching elements and changing over the direction of a current to flow at a magnetic head. CONSTITUTION:A head coil to execute the magneto-optical recording has an inductance Lx. One edge of the coil 1 is connected through an auxiliary coil 2 to a direct current power source 3 and grounded through a switching element S11. Other edge of the coil 1 is connected through an auxiliary coil 4 to a direct current power source 5 and grounded through a switching element S12. Coils 2 and 4 have an inductance Ld sufficiently larger than the inductance Lx of the coil 1. Switching elements S11 and S12 are turned on and off based on the recoding signal and controlled so as to be turned on and off alternately. Thus, the rise time of the current can be sufficiently shortened and the driving power can be made sufficient even when it is small.

Faraday rotation in a multimode optical fiber in a fast rise‐time, high magnetic field

Abstract: A magneto‐optic Faraday rotation diagnostic was implemented on a Z‐pinch driven flux‐compression generator to measure line‐averaged, megagauss, axial‐magnetic fields up to 1.6 MG with rise times of 30 kG/ns. The axial‐magnetic field rotated the plane of polarization of a 2‐W argon laser beam in a 0.725‐mm‐diam, fused silica quartz fiber mounted coaxial with the Z pinch. The rapid rise time and the high radiation environment presented by the Z‐pinch plasma caused a high‐pressure impulse <100 kbar, to be coupled into the quartz‐fiber probe disrupting the polarization‐preserving properties of the fiber. The time scale for disruption was characteristic of a shock propagating radially through the fiber to its core. This paper will describe the response of the Faraday diagnostic under these conditions and present a simple model that describes the effects of fiber depolarization that is consistent with previous observations of stress‐induced depolarization in optical fibers.

Picosecond Electro-Optic Sampling

Abstract: The electro-optic sampling technique is a new characterization technique based on short optical pulses (picosecond or femtosecond) and the electro-optic effect. With this technique, electrical waveforms have been characterized with temporal resolution of less than 300 fs, corresponding to a 1 THz bandwidth. Since its inception in 1982, this method has been adapted to a variety of measuring situations, leading to a large number of embodiments. The electro-optic sampling was first used to study the dispersion of picosecond electrical pulses on transmission lines. Using a superconducting transmission line, it has been recently shown that conduction losses can be defeated’and single picosecond pulses propagated over a few millimeters. Additionally, Ultrafast transistors have been tested with single picosecond resolution that is, the transistor response was time-resolved as the gate was pulsed using a step function with a picosecond rise time. MESFET, TEGFET, and permeable base transistor (PBT) responses have been studied, and switching times as low as 5 ps have been directly measured for the PBT. Because GaAs exhibits the Pockels effect, the GaAs components and circuits can be directly probed in a noninvasive way. We will review the principle of electro-optic sampling in its various embodiments and applications to device and circuit characterization, as well as the direct investigation of velocity overshoot and ballistic and resonant tunneling transport.

Dynamic noise blanker circuit

Abstract: An FM receiver as used in communciations systems includes a blanking switch for deleting noise pulses and a delay device for delaying the detected pulses so that blanking can occur at the correct time. The circuit receives and detects noise pulses and amplifies them at several gain levels simultaneously. Each amplified pulse which passes a predetermined level causes a trigger signal pulse to be coupled to a ramp generator. The trigger signal pulses are coupled through a combination of flip-flops and voltage controlled switches, and each noise pulse enables a ramp signal of a predetermined maximum but having a rise time which is a function of the detected noise pulse amplitude. The ramp signal length is used to provide blanking switch control signals of an appropriate length to blank out substantially all significant noise pulses.

Characteristics of the discharge current in the nanosecond‐pulse breakdown

Abstract: The rise time and the peak of a pulsed discharge current are measured under various experimental conditions such as the change in capacitances of both storage and peaking condensers. It is shown that the peak of the discharge current can be determined by the law of the second voltage‐time area. The relation between the rise time and the peak is also made clear.

Multigigahertz beam current and position monitor for relativistic electron beams

Abstract: A self‐integrating magnetic‐loop device having a rise time of less than 175 ps has been developed to monitor the temporal behavior of the current and position associated with an electron beam. Beam current and centroid position are measured with a 2‐GHz bandwidth by combining the output of these loops with two 0°/180° hybrids. The improved monitors are essentially free of self‐resonances and spurious responses at bandwidths extended to 2 GHz. The probes are economical and easy to produce in volume for a wide range of applications.

High-speed response characteristics of GaAs optoelectronic integrated receivers

Abstract: The letter focuses on the measurement of pulse response characteristics of an optoelectronic integrated receiver in which a GaAs metal-semiconductor-metal (MSM) photodiode and a GaAs field-effect transistor amplifier are monolithically integrated on a GaAs substrate. The maximum parasitic capacitance was found to be negligible for the total capacitance at the amplifier input. We also verified a fast response of this receiver showing a rise time of 300 ps.

Monitor for a cyclically varying parameter

Abstract: A medical monitor for monitoring a cyclically varying parameter, such as the pressure in an airway of a ventilator used to assist patient breathing, comprises a transducer (1) for measuring the pressure as an electronic signal, means (18) for timing the electronic signal at two defined points in the cycle, storage means (22) for storing electronic set-up information relating to the time taken for the value of the electronic signal to depart from one of the points and arrive at the other point, means (24) for comparing current information relating to this time with the stored, set-up information, and means (28) for generating an alarm signal when the current information varies from the stored information by more than a predetermined amount. A base level of Bt and a peak level of Pt are stored as well as a standard pressure rise time of RTsu. If the rise time for the value to rise from Bt to Pt exceeds RTsu by a predetermined amount, such as the rise time RThc, this indicates a high compliance condition which causes the alarm signal to be generated. In a similar way, if the rise time is much shorter, such as RTob, this indicates an obstructed condition which likewise causes generation of the alarm signal.

Electronic device driving circuit

Abstract: PURPOSE: To enable accurate test and measurement, by controlling current values of first and second variable constant current circuits according to a slew rate value of a rear stage amplifier CONSTITUTION: In a range below the maximum slew rate value of a rear stage buffer amplifier 9, an output level setting circuit 7 controls current values I 1 and I 2 of first and second variable constant current circuits 3 and 4 according to a difference value between first and second DC voltages VIH and VIL so that the rise time or fall time of an output side signal waveform becomes constant When the difference value exceeds a value corresponding to a specified slew rate below the maximum slew rate value, the current values I 1 and I 2 are controlled to be constant so that the rise time or fall time of an output signal waveform becomes constant regardless of the amplitude of an output voltage Regarding the maximum slew rate value, this can bring the slew rate value to a fixed value close to the maximum thereof thereby making a test and measurement more accurate as conducted varying the amplitude of an output waveform COPYRIGHT: (C)1988,JPO&Japio

High‐speed response of a quasi‐graded band‐gap superlattice p‐i‐n photodiode

Abstract: The photoresponse to a short optical pulse of a GaAs p‐n junction containing an undoped asymmetric GaAs/AlAs superlattice is reported. The response to a light pulse of <400 fs duration has been measured and a rise time of 80 ps is observed. The trailing edge of the response exhibits a long time tail, which is thought to be dominated by the time taken to tunnel through the thickest barrier, being the Γ‐Γ separation of the GaAs and AlAs of a 3‐nm barrier.

Cmos output buffer circuit

Abstract: PURPOSE:To attain the high-speed actuation of an output buffer circuit with reduction noises produced in a shift mode of the output state, by setting the different time points for both the rise and the fall of drive circuits of (P) and (N) channel MOS transistors of an inverter circuit respectively CONSTITUTION:A CMOS inverter consists of a (p) channel CHMOS transistor Tr6 and an NCHMOSTr7 of an output circuit of an LSI chip 1 The gates of both Tr6 and 7 are driven by a NAND circuit 3 and a NOR circuit 4 The rise time of the output signal E of the circuit is longer than the rise time of the output signal F of the circuit 4 when an external signal C is changed to '0' from '1' with the change of an input signal B Then the fall time of the signal E is longer than the fall time of the signal F For this purpose, both Trs constituting both circuits 3 and 4 are set properly Then the signal E has a rise and the Tr6 is turned off Then the Tr7 is gradually turned on Thus the through current flowing to an earth from a power supply is reduced and at the same time the time differential value of the earth current is reduced This can reduce the noise level

Contour correction circuit

Abstract: PURPOSE:To shorten a rise of an edge part of a picture signal without applying a preshoot nor an overshoot there and to improve a picture quality, by using a modulation signal as a writing clock of a delay element. CONSTITUTION:When a video signal A is supplied to a terminal 1, a secondary differential output B is obtained at an output terminal of a secondary differentiating circuit 7. While a clock signal C is delivered to a clock generating circuit 9. A frequency modulating circuit 8 modulates the frequency of the signal C with a differential output B and delivers a modulation signal D. A switch pulse generating circuit 5 delivers the switch pulse which is inverted every 1H. These switch pulses are supplied to switch circuits 4, 10 and 11. When the switch pulse is kept at a low level, the signal A is written to a delay element 2 with the signal D. While the element 2 is read out by the signal C when the switch pulse is kept at a high level. Then a video signal E is delivered to a terminal 6. As a result, the rise time tr of an edge part of the signal E is shortened compared with that of the signal A.

Development of a reliable fast response laser‐triggered dielectric switch

Abstract: Detailed performances of a laser triggered dielectric switch (LTDS) are described. Thin polypropylene films of 25 or 35 μm in thickness were used for insulation of the spark gap. Maintenance‐free operation was achieved by automatic winding of the film after each laser shot. A square optical pulse of 1 ns duration with a rise time of less than 350 ps was generated by using a fast Pockels cell driven by the LTDS with good reproducibility. The switching jitter was measured to be less than the detection limit of 100 ps. Using the LTDS, a single pulse was selected from a mode‐locked pulse train with the success probability of better than 95%. Comparison of the performance of the LTDS with other switching devices are given.

Effect produced by the charge collection time upon the time and energy resolution of semiconductor detectors

Abstract: The effect produced by the charge collection time upon the time and energy resolution of semiconductor detectors has been studied. It is shown that sampling of pulse rise times permits one to identify in coaxial detectors a group of pulses corresponding to the detection of radiation in surface layers of the detector. Choosing pulses with the maximum rise time rate allows one to improve the time resolution of the coincidence spectrometer and achieve 2τ = 1.65 ns, instead of the 2τ = 5.50 ns for coincidences of the 1332 keV gamma line and β− particles from 60Co.

A multiwire proportional counter for low energy X-ray imaging

Abstract: Development of a detector for a Bragg spectrometer experiment is described, including the test setup and the read out electronics. A few examples of the position resolution are presented.We have built and put into operation a computer controlled test-stand with: A collimated x-ray beam in the energy range of 0.5 to 6 kev and the width of 50 to 200 microns, an x-y translation table for positioning the detector,a gas system for recirculating and filtering of different gas mixtures and pressures and an electronics system using the charge division method for event position determination. Charge pulses from the detector are digitized and analysed in a micro-processor where the position and energy spectra are stored. Background rejection is determined by energy, position and rise time windows in the micro-processor software.

Method for writing of semiconductor non-volatile memory

Abstract: PURPOSE:To lower a maximum electric field applied to a thin oxide film, prevent a damage produced in a thin insulating film and increase the number of rewriting by making longer a rise time of an electric potential of a floating gate electrode to more than 300musec. CONSTITUTION:By using a fully slow rise pulse, before a control gate voltage reaches to a maximum control gate voltage VCGmax, an electron is injected into a floating gate electrode. Accordingly, even when a voltage of the control gate voltage reaches to the maximum value VCGmax, an electric potential of the floating gate electrode is not enhanced, so that a high electric field is not impressed to a floating gate oxide film 6, and therefore, a damage can be prevented. When the rise time of the writing control gate voltage pulse is above 300musec, a minimum drain writing voltage can be prevented from increasing.

Power source for electromagnet

Abstract: PURPOSE:To prevent the increase in capacity of a power source transformer and a smoothing circuit and improve the quick-responsing property of current flow by a method wherein power is enabled to be mutually fed to load using two diodes and two switching elements respectively. CONSTITUTION:When a current rises, the rise time of current is cut down by turning transistors 19 and 20 to ON state and feeding the voltage obtained by adding two DC voltage of VF and VR to load 23, the transistor 19 is turned OFF and switched to the ordinarily required low voltage VR. Also, as the DC voltage VF can be applied to the load 23 with the polarity reverse to the direction in which a load current is running by turning both transistors 19 and 20 to OFF state when the operation of the power source is stopped the attenuation of load current can be accelerated. As the title power source can be selectively used by giving ON or OFF position on the two switching elements as above- mentioned, the increase in transformer capacity and smoothing circuit of the power source can be prevented, thereby enabling to obtain the power source of excellent quick-responsing property of current to be used for the electromagnet.

Pulse width converting circuit

Abstract: PURPOSE:To attain the conversion of a short pulse width by connecting a transistor (TR) between input terminals of inverters of the prestage and the pose-stage in a pulse width converting circuit comprising two-stages of inverters having a resistor and a load capacitor at the midpoint. CONSTITUTION:When input terminals 6,9 reach a high level, FETs6,9 are turned on to bring the level of nodes 41,42 to a low level. When the node 42 reaches the low level, since it is discharged directly by the FET9, the signal fall time is decreased. When the node 42 goest to the high level, it is charged up via a resistor R2 and the FET9 does not give any effect on the rise time. Since the minimum pulse width possible for conversion depends on the signal fall time, it is possible to convert the short pulse width.

Measuring arrangement for determining the optimum reaction between electromagnetic waves and gravitation, and method for evaluating this measurement for medical and biological applications

Abstract: Optimum reaction between electromagnetic waves and effects based on gravitation are produced in biological systems and in the human body by applying a swept UHF oscillation to the system or the body in such a way that the saw-tooth sweep voltage has a minimum slope of the wave front, the sweep frequency is approx. 160 Hz (or a multiple of this frequency), the swept UHF oscillation being in the region of 200 - 400 MHz, 400 - 800 MHz (or a multiple of these frequencies). The position of the range of effectiveness of these oscillations, and the optimum magnitude of the control voltage, whose ratio of fall time to rise time is at least 10:1 are determined in a special measuring arrangement. The latter consists of a control unit for generating the sweep voltage, a UHF sweeper, a wideband measurement receiver and a dual-trace oscilloscope for comparing the control signal to the AF output signal of the measurement receiver.

Digital signal generator

Abstract: PURPOSE:To make high-speed operation possible without overshoot and spike though a diode switch output stage is provided, by superposing a signal, which is changed in accordance with the amplitude of an output signal, to compensate an operating current at the transition time of high level/low level output switching. CONSTITUTION:When a low level set power source A2 is switched to a high- level set power source A1, the difference between set voltages Vih and Vil of power source A1 and A2 is processed by a differentiating circuit consisting of a resistance R2 and a capacitor C1 of an output current compensating circuit CC1. An N-type transistor TR 1 is turned on by the differential output, and the compensating current which is changed in accordance with the amplitude of the output signal with diodes D1 and D2 as the switching output stage is superposed to the current from a current source CS1 to compensate it at the transition time of output level switching. The similar operation is performed when the power source A1 is switched to the power source A2; and thus, the rise time and the fall time of the signal are shortened to perform the high-speed operation though the diode switch output stage is provided, and the occurrence of overshoot and spike is prevented.

Optical rise time and frequency chirping predictions for (forward-biased) optical absorption modulators

Abstract: The modulation characteristics of the (forward-biased) semiconductor travelling-wave absorption modulator, a prime contender for monolithic-integration with an injection laser, is analysed. It is found that, as a consequence of the distribution of charge carriers along the length of the device, the modulator output rise/fall times are limited for practical devices to greater than ∼500 ps, corresponding to a maximum bit-rate of the order of 2 Gbits/s. Moreover, phase modulation in the device resulting from fluctuations in the refractive index (linked to the change in absorption) results in unwanted frequency modulation (chirping) of the order of several GHz. These figures suggest that, although easy to fabricate, this device offers little performance advantage over direct modulation of the laser itself.