Showing papers on "Rise time published in 1980"

Traveling wave optical modulator using a directional coupler LiNbO 3 waveguide

Abstract: Fabrication methods for low drive voltage and broad-band LiNbO 3 waveguide directional coupler optical modulator are described. Optical waveguides were prepared by conventionaly Ti in-diffusion into LiNbO 3 c -cut plate. To obtain wide-band frequency response, traveling wave electrodes were used. Electrode characteristic impedance measured by time domain reflectometry method coincided well with the calculated value by conformal mapping. Measured electrode conductor losses followed square root of frequency. To reduce electrode conductor losses, asymmetric and 3-μm thick Al electrodes were used. Directional coupler optical modulator frequency response was analyzed, using the phase difference average value along the propagation directions. Calculated value by this method coincided well with measured value obtained by a swept frequency technique. The characteristics of this modulator at the 1.317-μm wavelength are as follows: 100 percent modulation voltage is 4 V, extinction ratio is 17 dB, optical insertion loss is 5.4 dB, 3-dB bandwidth is 3.6 GHz, and rise time is about 400ps.

A Josephson ultrahigh‐resolution sampling system

Abstract: An ultrahigh‐resolution Josephson‐technology sampling system has been designed and tested. A complex test signal containing a 10‐ps rise time was measured and agreed very well with the signal expected from simulations. The intrinsic rise time (step response) of the sampling system is believed to be about 6 ps. External analog circuitry was used to automate the system.

Room Temperature Operation of the InGaAsSb/AlGaAsSb DH Laser at 1.8 µm Wavelength

Abstract: The In0.05Ga0.95As0.04Sb0.96/Al0.2Ga0.8As0.02Sb0.98 DH lasers, which can be operated at room temperature, were fabricated by the LPE method. Their emission wavelength and threshold current density at room temperature are 1.8 µm and 5 kA/cm2 respectively. Their characteristic temperature, defined as T0=ΔT/Δln Jth is 112 K, which is higher than those of InGaAsP/InP DH lasers. Optical output pulse response exhibited sufficiently short rise time, and the spontaneous carrier lifetime around the threshold current was estimated to be 3 ns at room temperature.

Current and neutron yield scaling of fast high voltage plasma focus

Abstract: Numerical and experimental studies have been made concerning an increase of the effective discharge current for the plasma focus from a bank of constant energy. From the higher discharge current an increased neutron yield is expected. Experimentally an 85 kV/12 kJ device with a current rise time of 600 ns was investigated. The obtained neutron yield was larger by a factor of 3 compared to devices of equal energy but low voltage. The geometrical and pressure variations necessary for optimization, are discussed. Using MHD-calculations and impedance considerations, various banks, including those with high voltage and low inductance, are compared with respect to plasma data and discharge current.

System and method for measuring ultrasonic return signals

Abstract: An ultrasonic return signal analyzing instrument and method including analog circuitry for making partial power measurements on two selected frequency bands of the frequency spectrum of an ultrasonic return signal waveform and digital circuitry for measuring selected features of the envelope of the ultrasonic return signal waveform. Digital waveform measurements are converted to analog signals and then combined in an algorithmic combining circuit to produce a test statistic signal. A decision circuit receives the test statistic signal and registers a decision on a characteristic of the structure under examination based on the value of the test statistic signal. The instrument includes a signal normalization circuit to normalize the ultrasonic return signal to a fixed peak value and includes a frequency up-converter in the normalizing circuit and frequency down-converters in the partial power measurement circuits for increasing the accuracy of peak detection in the normalizing circuit and envelope detection for the partial power band signals and the total power signal. The digital waveform feature measurement circuitry includes circuitry for measuring the rise time and duration time of the ultrasonic return signal envelope and logic is provided for handling two distinct return signal waveforms with rise time and duration time measurements being accomplished on the highest distinct pulse within the GATE signal window of the instrument. A GATE signal generated from the delayed GATE input of the pulser receiver of an ultrasonic instrument is utilized to GATE the various measurement functions so that measurements will be made only on the selected segment of the ultrasonic return signal waveform desired to be analyzed. A Fisher linear discriminant function is used as the algorithm in connection with analyzing ultrasonic return signals from stainless steel pipe having possible intergranular stress corrosion cracking conditions therein.

High Power Density Water Dielectric Switching

Abstract: Pulse forming networks for high current particle beam fusion accelerators must produce fast rise time, low jitter, low prepulse, and high voltage power pulses. Conventional water dielectric switching can provide the required rise time and jitter, but has limitations on prepulse and output voltage. A high power density, low prepulse, pulse forming line (PFL) configuration with self-breakdown water dielectric switches is presented. The design parameters and the results of switching experiments are described.

Methods and apparatus for generating microwave pulses and for the measurement and control thereof

Abstract: Picosecond duration microwave pulses are generated used a laser activated semiconductor switch. High voltages are switched with picosecond rise time and result in the establishment of microwave pulses of frequency spectrum commensurate with the rise time of the voltage and wave guide parameters of a wave guide in which the switch is disposed. The activating light pulse is synchronous with the microwave pulse. A system, including an antenna and radar receiver, is responsive to the light pulse and return signals from a target on which the microwave pulse is incident. Reflection measurements of the microwave pulses from a body of semiconductor material which is optically excited by the light pulses relatively delayed between the generation of successive microwave pulses, indicate the duration of the microwave pulses.

Count discriminating fire detector

Abstract: A detecting circuit is responsive to the change in a physical parameter indicative of a fire such as smoke, heat, flame or the like, and a comparator circuit connected to the detecting circuit produces detection pulses in synchronism with an oscillator circuit when the change in the physical parameter exceeds a predetermined amount. A counter circuit counts the detection pulses and produces an output which triggers a switching circuit when a predetermined number of consecutive detection pulses are counted. When triggered, the switching circuit transmits an alarm signal to an alarm receiving panel. Connected between the counter circuit and the switching circuit is a monostable multivibrator having a time constant which is equal to or smaller than the supply voltage rise time constant of the counter circuit so as to prevent the trigger signal from being applied to the switching circuit during the transition period immediately following the connection of the power source. A detection sensitivity validation means directs the detection pulses from the comparator circuit to the outside so as to facilitate the sensitivity adjustment.

Overvoltage-pulse analyzer

Abstract: A system for measuring and storing the amplitudes plus duration and/or rise times of overvoltage pulses occurring on a transmission line comprises a voltage divider working into a first and a second comparator respectively detecting an abnormal voltage exceeding a predetermined sensitivity threshold and discriminating among different amplitude levels above that threshold. The first comparator triggers an oscillator driving a pulse counter which measures the duration of an overvoltage pulse and also provides quantized information on rise time to the highest amplitude threshold surpassed by that pulse as determined by the second comparator. This information is stored in a memory with two groups of cells respectively assigned to combinations of amplitude with duration and combinations of amplitude with rise time, the occurrence of any such combination incrementing the contents of the respective cell. These cells are cyclically scannable and their contents can be selectively displayed on a visualizer such as an oscilloscope.

Circuit effects in time-of-flight diffusivity measurements

Abstract: A Monte Carlo procedure is used to examine certain effects that interfere with the determination of the diffusivity D from current rise and fall times in a time-of-flight experiment. It is found that electron bombardment time, sample capacitance, contact resistance, and oscilloscope rise time can cause considerable error in the measurement of D, especially near the threshold electric field. It is shown that a reasonable accounting for these effects can explain much of the difference between experimentally-and theoretically-determined D-E characteristics for GaAs.

Space-time response of a cloud communication channel to an optical signal

Abstract: An optical signal,an impulse in space and step in time,is incident on a plane,parallel fixed,homogeneous cloud. The incident signal is modelled as a stream of photons, each of them executing a random walk. A Monte Carlo simulation technique is applied to obtain the space-time response of the channel when an optical receiver with a specified field of view is located at a specified distance below the cloud. The response is obtained as angular, spatial and temporal dispersions. Various simulation steps are described. For thin clouds two variance reduction techniques, i.e. Russian roulette and forced collision, are used. It is shown that the bottom of the cloud tends to diffuse uniformly and the 3 dB exit beam width saturates. The rise time in this channel is found to be of the order of several nanoseconds.

An Electron-Beam Triggered Spark Gap

Abstract: The triggering of a high-voltage gas-insulated spark gap by an electron (e) beam has been investigated. Rise times of approximately 2.5 ns with subnanosecond jitter (~0.2 ns) have been obtained for 3-cm gaps charged at voltages as low as 50 percent of the self-breakdown voltage (varied up to 0.5 MV). The switch delay (including the e-beam diode) was 52 ns. The triggering e-beam pulse has a duration of 15 ns and a 0-50 percent rise time of 1.5 ns. The e-beam current is 0.5 kA, and the electron energy can be varied in the range from 80 to 145 keV. The working media were N2, mixtures of N2 and A, and N2 and SF6 at pressures of 1-3 atm. Voltage, current, and jitter measurements have been made for a wide range of gap conditions and e-beam parameters. Variations in the character of the discharge have been inferred using streak and open shutter photography. The photographs show that the discharge has a broad cross section and that its character varies for differing polarites and voltages. The effects of varying the e-beam width and the beam energy are discussed.

Waveform analyzing unit

Abstract: PURPOSE:To reduce the load of software and make the prallel wave form processing possible in a high speed by detecting the peak of input signals and setting an instrumentation level. CONSTITUTION:This unit is equipped with peak detector 12 which is operated by receiving an instrumentation command from computer 22 and performs the sampling hold of the peak value of input signals, instrumentation level setting equipment 14 which sets prescribed high and low levels in a range of the peak detection output, high and low comparators 17 and 18 which compare respective higher and lower set values with the input pulse signal value, AND gate 19 for cpmparison output, generator 20 which supplies clocks to the gate output, and counter 21 for clocks which pass through the gate. Then, the counted value of the counter is used to measure the rise time and the break time of a waveform, thereby performing waveform analysis.

Transit‐time considerations in short‐pulse photoconductivity

Abstract: Little attention has been paid so far on the transit‐time effects in the short‐pulse photoconductivity. This paper discusses the effect of transit time on the time evolution of carriers in short‐pulse photoconductivity. This is likely to effect the rise time of a fast‐switching device. It is concluded that, due to the transit‐time effects, a device using surface generation of carriers would have faster rise time than a device in which carriers are generated in the bulk, particularly when the specimen is thick.

Automatic adjuster circuit for reading pulse phase

Abstract: PURPOSE:To secure an automatic adjustment of the reading pulse to the optimum phase by regarding the reading pulse phase featuring the munimum code error detecting frequency as the optimum phase. CONSTITUTION:The error current value read out via reading address designation circuit 20 and memorized in memory circuit 11 is supplied sequentially to minumum value detection circuit 21, and only the minimum value is sent to reference error number setting circuit 22 to be added with a fixed number and then turned to the reference error number. The output of comparator 23 comparing the reference error number with the error count number holds the count value of counter circuit 24 relating phases corresponding to the fall and rise time at detection circuits 25 and 26 of the domain start and terminal each. In this connection, the output of differentiating circuit 27 and the differential inverse outlut of the comparison output are applied to circuits 25 and 26, and the output of the both circuits are supplied to phase setting circuit 28 via arithmetic mean calculatlation circuit 27 to be converted into the digital value of the control voltage corresponding to the optimum phase. As a result, an automatic adjustment is ensured for the reading pulse to the optimum phase.

Temperature and rise-time effects on dynamic strain measurement

Abstract: Strain pulses in a test specimen were measured over a temperature range of −73 to +149°C with foil and semiconductor strain gages. These tests were performed to determine if the rise time and amplitude of the gage output change as a function of temperature. The existence of a constant that should be added to the theoretical rise times of resistance strain gages, as suggested by Koshiro Oi, was reexamined. ‘Long’ rise-time strain pulses were produced in the test specimen by an impacting steel ball. The rise times of these pulses were on the order of 7 μs and the amplitudes were approximately 65 μm/m. The results of these tests show that the rise time and amplitude of the gage do not change as a function of temperature. ‘Short’ rise-time strain pulses of approximately 500 μm/m with a rise time of 2 μs were produced in a test specimen by a short pendulum-type hammer apparatus. The results of these tests showed that the amplitude of the gage output was relatively independent of test temperatures but exhibited a slight hysteresis effect. The rise times for these tests remained constant up to a temperature of 93°C, then started to increase. The rise times at 149°C were approximately 100 percent longer than at room temperature. Under optimum conditions, a pulse with a measured rise time of 0.18 μs could be generated. The results of these tests indicated that the theoretical rise-time additive constant of resistance strain gages is 0.05 μs or less. This is one-half the value that Bickle arrived at by reevaluating Oi's data. However, since the real rise time of the pulse was unknown, this additive constant is not necessarily a property of the gage.

Speed control system for step motor

Abstract: PURPOSE:To smoothly permit the starting and the halt of step motor by a method wherein the excitation phase switching time of the step motor for the rise time and the fall time is previously stored as data in the memory element such as the read only storage or the like. CONSTITUTION:The binary-coded value of the excitation time of 1 step divided by the cycle of the clock b is stored in ROM2. The counters 1, 3 are set by the output j of the flip-flop 5 which is set by the starting signal a, and the ROM2 is read out by means of the address signal d of the counter 1. The output e is counted up at the counter 3 by means of the clock b to emit the carry signal f. The signal f develops into the signal g synchronized with the clock c through the D flip-flop 4 to enter the counter 6. And the step motor 8 is accelerated according to the data of ROM2. In case of the reduced speed time, the sequence of read of ROM2 becomes reverse.

Spatial change of rise time of spectral line intensities in hollow cathode discharge tube.

Abstract: The local dependence of the rise time of the emissive line intensities of Ne in a cylindrical hollow cathode has been measured as a step toward studying the mechanism of emission. Several new interesting results were observed: In a special range of gas pressure, the temporal change of the intensities at the central axis portion shows a clear initial peak enhancement and then a decrease to the stationary state. The rise time of the intensity at the central axis portion is always a few microseconds faster than the edge portion. The precision of the time resolution of our apparatus is qualitatively discussed.

Generation of nanosecond high-voltage pulses with high repetition rate

Abstract: The letter presents a circuit for the generation of 50 V pulses with 1.2 ns rise time, 2.5 ns duration and a variable pulse repetition frequency up to 3 MHz based on the effect of avalanche multiplication. The use of standard epitaxial silicon planar transistors instead of selected avalanche types permits safe operation with low sensitivity to temperature variations.

An Investigation of Fast Low Power Charge Sensitive Preamplifier Design

Abstract: As nuclear measurement instrumentation becomes more and more sophisticated, there is an increased interest in reducing the rise time in charge sensitive preamplifiers, e. g., to allow precision spectroscopy with narrow pulse shaping or to reduce jitter in timing measurements. For charge sensitive amplifiers with a FET input, the phase shift produced in the FET is found to approximate a delay which is seen to be the most significant limitation on the amplifier closed loop bandwidth. Loop stability constraints limit the achievable rise time to 1 to 2 times the overall loop delay which can approach that of the FET. Three design approaches and circuit examples are given using one, two, and three voltage gain stages preceding an output buffer.

Pulse driver circuit

Abstract: PURPOSE:To maintain the phase and period of an output in a normal state even while a synchronizing signal is cut off, by measuring a difference in rise time between an output pulse from a free-running oscillator and then by controlling a ratio of division of a free-running oscillation output by the output. CONSTITUTION:A pulse from free-running oscillator 2 drives counter circuit 14 and is divided by 1/N-divider circuit 15, whose output is made into a pulse of duty 50% by FF16 and then outputed from terminal 4. By exclusive-OR circuit 5, OR circuit 6, monostable circuit 7, and AND circuit 8, a period when an external synchronizing signal differs in rise part from an output signal from oscillator 2 is separated and this length is subtrated by up-down counter 9 when the rise of the output signal lags or added when leading, by using as a unit pulse obtained by dividing 10 the output of oscillator 2 by a number 2 or greater. As a result, when the output signal lags, circuit 15 performs division by a number smaller than usual and when leading, division is done reversely, thereby making a shift in a direction where it agrees with the external synchronizing signal.

The influence of stimulus spectral content on rise time effects in cortical-evoked responses.

Abstract: A tone burst with a fast rise time elicits a large-amplitude cortical response which reduces markedly as rise time is increased. This effect is not observed with white-noise bursts. It is suggested that where changes in rise time affect the spectral content of the stimulus, a change in response amplitude is encountered. The increase in the latency of the response with increase in rise time is found to be the same for both tone and noise bursts, hence independent of spectral composition.

Rise time control circuit for amplifier

Abstract: PURPOSE:To improve the rise by installing the circuit which charges the decoupling capacitor CONSTITUTION:Potential E2 at middle point M between voltage division resistances 12 and 13 is set lower than steady active voltage EC of front-step amplifier 2 and higher than action start voltage E0 each With the make of power switch 11, the charging is given to decoupling capacitor 7 from point M of the voltage division resistances and through diode 14 The circuit can secure the operating state quickly since the time constant is shorter than the charging given through decoupling resistance 8 At the same time, no reverse current flows at the normal state due to diode 14 thus to secure the steady state

Laser diode single mode oscillation device

Abstract: PURPOSE:To make it possible to realize single mode oscillation even at the time of modulation, by providing a reflecting element having wavelength selectivity on the axis of beam of a laser diode. CONSTITUTION:Band stop filter 5 as a reflecting element is provided on one end surface of laser diode 4. Band stop filter 5 has the characteristic of reflecting strongly only the mode of wavelength lambdao. Consequently, the reflection factor of the end surface of laser diode 4 becomes 8 maximum at lambda=lambdao, and the loss of the mode of wavelength lambdao becomes small compared with other modes. In the case of general laser, the rise time of each mode is delayed, and after a certain time, all rise at the same time. But, when the loss of a specified mode is made small, the rise time of the specified mode becomes fast, and the rise of other modes is checked. Hence, it is possible to obtain single mode oscillation even at the time of modulation. Band stop filter 3 may be placed vertically on the axis of the beam of laser diode 4.

Zero Cross-Over Timing with Coaxial Ge(Li) Detectors

Abstract: The performance of zero cross-over timing systems of the constant fraction or amplitude rise time compensated type using coaxial Ge(Li) detectors is analyzed with special attention to conditions that compromise their energy-independence advantage. The outcome is verified against existing experimental results, and the parameters that lead to minimum dispersion, as well as the value of the dispersion to be expected, are given by a series of charts.

Method of suppressing selffoscillation of electromechanical converter

Abstract: PURPOSE:To abruptly displace a bimorph without self-oscillation in an electromechanical converter by superimposing second drive voltage having the same period, amplitude and 180 deg. of phase difference as and from the self-oscillation components in the first drive voltage to the first drive voltage. CONSTITUTION:When predetermined voltage 22 is stepwisely applied to a bimorph, it can respond with a wave 23 of T/2 with self-vibration period T until the initial peak value due to the transient theory. When the Q factor of the bimorph is approx. 10, the excessive amount is approx. 1, and the amplitude sigmat1 is twice the ideal displacement sigmas1. Accordingly, the bimorph is displaced by sigmas1/2 by the pulse 24. The response of the bimorph for the pulse waveform 24 is the synthesized negative and positive stepwise voltage 25 and 26, and the responses to the respective voltage becomes self-oscillation with the period T and the amplitude sigmas1. Therefore, when synthesizing them by taking into consideration with the symbolts, the bimorph responds with the waveform 29. When it is now driven by the synthesized waveform 20 of the pulse 24 and the stepwise voltage 22, the transient response of the bimorph becomes the waveform 31. After the rise time of the T/2 period the displacement sigmas1 becomes constant to abruptly displace without self-oscillation.

Automatic frequency discriminating circuit for commercial power supply

Abstract: PURPOSE:To discriminate a commercial power supply frequency automatically by comparing and discriminating the outputs of a frequency pulse generator circuit corresponding to a power supply period and a comparison pulse generator circuit selected in connection with a different power supply frequency CONSTITUTION:Commercial power of 50Hz or 60Hz is supplied to binary circuit 4 A pulse is generated from differential circuit 5 at the rise time of the output and from differential circuit 10 at the fall time This is connected to clock pulse generator 1, and a train of pulses corresponding to the power supply period is formed By the output of differential circuit 5, frequency divider circuit 2 starts counting, comparison pulses are formed and are compared with the output of differential circuit 10 in discriminator circuit 11, and an output is obtained in detector circuit 9 via 50-Hz counter 7 and 60-Hz counter 12 Consequently, output i and output l become 1 respectively at 50Hz and 60Hz, so that it is possible to switch those circuits automatically by this value when their switching is required