Showing papers on "Rise time published in 1970"

Time domain reflectometer

Abstract: A typical sampling time domain reflectometer (T.D.R.) apparatus is modified by the addition of an integrator which can be selectively switched into and out of the vertical signal path. The integrator is utilized to integrate signals reflected from any reactive discontinuity in a transmission line under test. The amplitude of the integrated signal is utilized to enable the accurate determination of the reflection coefficient. The derived results are substantially unaffected by variations in the rise time of the step function signal. In addition, the apparatus'' independence from the step function signal rise time enables the use of a longer rise time and thus the system''s bandwidth requirement is lessened to the point where a real time T.D.R. apparatus may be utilized.

Effects of acoustic rise time on heart rate response

Abstract: Effects of acoustic rise time on heart-rate (HR) response were tested in two experiments. With 50- and 75-dB tones, effects were not clear-cut, but, at 90 dB, fast onsets produced an initial acceleration and slow onsets an initial deceleration. Results were discussed in terms of orienting and startle responses.

A preliminary analysis of the dynamics of the pecking response in pigeons.

Abstract: The pecking response of pigeons is usually measured by a transducer that senses the presence or absence of a response. Typically, the response force as a function of time has not been accurately measured. Data were collected using a transducer specially designed to record the waveform of the pecking response in pigeons. Each response on the target surface of the transducer was reinforced and followed by a blackout. The response was stored on an oscilloscope screen and the peak force and duration of the response were recorded manually from the oscilloscope screen. The mean peak force of the response substantially exceeded the minimum criterion for reinforcement of 35 g (0.343 Newtons) of force. Photographs of the waveform of pecks on the transducer showed great variability in response force and demonstrated that the waveform produced by pecking the target surface was complex. The responses were frequently asymmetrical with the rise time shorter than the fall time, although no single verbal description could be applied to all of the waveforms. Bimodal peaks and double responses were observed and the first peck or response was usually larger than the second. A disadvantage of the transducer was that pecking produced oscillation of the transducer at its resonant frequency. In spite of this deficiency, the waveform of the peck was easily recognizable.

Experimental analysis for the large-amplitude high-efficiency mode of oscillation with Si avalanche diodes

Abstract: This paper presents the result of an investigation aiming to clarify the large-amplitude oscillation mechanisms of a Si avalanche diode with high efficiency, a part of which was already reported in [6], by varying circuit conditons and the shapes of applied voltage pulses. Applying a pulse resistive, transient voltage across and current through the diode have been observed by varying the rise time of the source voltage. As a result, variations of these waveforms have been revealed with decreasing the rise time and if the slope of the diode voltage at the breakdown is large than 100 V/ns, damping oscillation has been observed with the amplitude increasing proportionally to this slope. This damping oscillation plays a significant role in initiating the stable large-amplitude oscillation. Using a resonant cavity, voltage and current waveforms at various points have been observed and analyzed for various cavity lengths and applied source voltages. The analysis shows that the voltage wave-form across the diode coincides with the superimposed waveforms of the wave incident on and the wave reflected from the diode, the latter being delayed about 60 ps with respect to the former. This oscillation mechanism is considered to be very close to the TRAPATT oscillation. The details of experimental results, oscillation characteristics, and their analyses are explained.

Circuit for controlling the conduction of a switching device

Abstract: A circuit for controlling the conduction of a switching device, such as a silicon controlled rectifier, Thyratron tube, mercuryarc tube and the like, which turns on and off the switching device so as to produce a load voltage with a fast rise time, a fast fall time and a wide range of pulse widths at a high repetition rate. To obtain a fast rise time of the load voltage, the switching device is turned on in series with a direct current source with all elements interconnecting therebetween electrically decoupled. To obtain a fast fall time for the load voltage, a direct current voltage is applied in series with the switching device which is of a polarity opposite from the polarity of the direct current source used to furnish power to the load. This reverse voltage is of an appropriate magnitude and time duration for turning off the switching device, and in addition thereto, electrically decouples the load from any direct current source at the same time as the switching device is reversed biased. Toward this end, a reactive element is disposed in series with the direct current source and the switching device. It has been found that energy is stored in the reactive element during the turning off or the commutation period of the switching device. Such stored or trapped energy in the reactive element inhibits the succeeding application of the appropriate magnitude and time duration of reverse voltage to the switching device for turning off the switching device. Consequently, such stored trapped energy is a detriment to commutating the switching device in succeeding commutation intervals. Thus, one embodiment of the present invention is to dissipate the trapped energy stored in the reactive element before the next commutation period. Another embodiment of the present invention is to inhibit the accumulation of trapped energy in the reactive element. Both embodiments have a small commutation interval, and are therefore capable of high switching rates.

Low Noise Preamplifier for Simultaneous High Resolution Energy & Time Measurement with Semiconductor Detectors

Abstract: A new charge sensitive preamplifier permits state of the art timing with semiconductor detectors without compromising energy resolution. The compromises that are involved in previous methods of obtaining amplitude and time information are avoided by using a single input FET followed by fast, low noise circuitry. With the same input transistor the noise in the "energy" channel is the same to within a few per cent as for the best room temperature preamplifiers. There are two timing outputs. The faster of these is voltage sensitive and has a rise time of 2 nsec. The slower output, which is obtained from the output of the charge sensitive loop, has a rise time of less than 5 nsec for external input capacities up to 50 pF with 0.5 pF feedback capacitor. The leading edge response can be adjusted to approach an exponential function with a time constant as low as 6 nsec. This property is desirable when timing with thick detectors that have a fluctuating charge collection time, where it is necessary to trigger near the base line.

Universal Microwave Phase-Measuring System

Abstract: A 70-GHz microwave phase-measuring system, capable of detecting small as well as multiradian phase changes, is described The use of programmable, digital dividing circuits permits phase changes of up to 20 ? radians to be measured without ambiguity A 2-?s rise time of system output permits rapid phase changes to be detected The output voltage, which is directly proportional to phase change, can also be monitored by a digital voltmeter or a chart recorder for long time measurements Signal limiting makes the measurement relatively insensitive to a 20-dB change in microwave signal level

Pulse measurements with resolution time of 18 ps

Abstract: With a new self sampling system, based on a relay-generator with directional couplers as pulse formers, measurements of the transient response of a system with a time resolution of 18 ps without any jitter are possible. The rise time of the generator is better than 12 ps. The time-scaling factor is obtained by a distance measurement.

Theory of Nanosecond Pulse Generation by a Parallel Plate Capacitor Discharged in the Centre

Abstract: The discharge of a transmission line in the form of a plate capacitor is studied theoretically. The aim of the present investigation is to find out how to achieve a short rise time of the generated electromagnetic pulse. Applying Laplace transform technique the mixed initial boundary value problem for the wave equation is solved for the case where the resistance of the spark is a constant. The corresponding problem for a time dependent resistance is treated by means of a computer. It is demonstrated that the rise time of the pulse essentially depends on (a) the geometry of the system, (b) the dispersive properties of the insulating dielectric medium, and (c) the time dependence of the spark resistance.

Interference Characteristics of Streamer Discharges

Abstract: This paper discusses analytical and experimental results of a study on streamer formation, discharge waveforms, and RF noise levels. Measurements disclose typical pulse parameters as follows: rise time = 20 ns, discharge time = 80 ns, and pulsewidth < 600 ns (dependent upon test sample). A mathematical model is developed to represent electric field strength in the vicinity of the streamer with supporting measured values.

Electronic Collimation in Proportional Counter by Rise Time Discrimination

Abstract: A method of electronic collimation in the proportional counter was developed and its performance examined. The method utilizes the difference in the rise time of output pulses. The rise time is converted into pulse height using a rise-time-to-pulse-height converter, followed by a single channel pulse height analyzer. Choosing the pulses of the fastest rise time one can selectively register the energies of the particles parallel to the center wire (anode). The method is applicable to gas recoil fast neutron spectrometers.

Rational delay functions based on continued-fraction expansion of ex

Abstract: Rational approximations to the ideal delay function e−ts (where τ is the delay time, and s is the complex frequency) based on the continued fraction expansion (c.f.e.) of ex are studied in both the frequency and the time domains. Comparisons with other approximations show that the new approximations have the least ratios of rise time to delay time for the same order of the function and within certain tolerances of overshoot and undershoot in the step response.

Calibration and correction of magnetic loop detectors

Abstract: A PROCEDURE IS DISCUSSED FOR THE CALIBRATION AND CORRECTION OF MAGNETIC LOOP DETECTORS. THE NEED FOR SUCH A CORRECTION ARISES FROM THE FACT THAT THE RISE TIME OF THE DETECTOR SIGNAL IS AN APPRECIABLE PERCENTAGE OF THE TYPICAL DURATION OF THE SIGNAL. THE CALIBRATION AND CORRECTION WERE CARRIED OUT BY COMPARING SIGNALS FROM MAGNETIC LOOPS WITH "BENCHMARK" SIGNALS OBTAINED AT THE SAME LOCATIONS BY USING PHOTOCELL DETECTORS, WHICH HAVE A CONSIDERABLY SHORTER SIGNAL RISE TIME. BOTH LOOPS AND PHOTOCELLS WERE ARRANGED IN PAIRS, ABOUT 13 FT APART, FORMING A DETECTOR "TRAP" THAT PERMITTED MEASUREMENT OF SPEEDS AND LENGTHS OF VEHICLES. THE SIGNALS WERE RECEIVED AND PROCESSED BY USING AN ON-LINE COMPUTER SYSTEM. A REGRESSION FIT OF LOOP AND PHOTOCELL DATA YIELDED AN EFFECTIVE LENGTH OF THE LOOP TRAP AND CORRECTIONS ON THE PULSE PROFILES THAT COULD MATCH THEM AS MUCH AS POSSIBLE WITH THE BENCHMARK PROFILES. /AUTHOR/

Non-linear transmission line current driver

Abstract: There is disclosed herein an arrangement for developing a fast rise time current pulse in a transmission line. The pulse is produced in the line in steps until the final value of current is reached. By developing the drive current in incremental steps undesirable overshoot is eliminated.

Current pulses due to discharges in a gaseous cavity in solid dielectric

Abstract: Experiments using a technique incorporating a microstrip transmission line have shown that the rise time of the initial current pulses due to discharges in a gaseous cavity of depth 0.05 mm in solid dielectric is approximately 250 ps.

Laboratory Identification Of The Quality Factor Q: Comparative Presentation And Evaluation Of Spectral Ratio And Rise Time Methods

Abstract: Two different methods for evaluating attenuation through the quality factor Q are presented, tested and compared. Both methods are based on laboratory experiments of ultrasonic P waves propagation at "ad-hoc" rock samples. The advantages of each experimental method are discussed. The spectral method is a rather laboratory oriented methodology providing attenuation information over a range of frequencies and seems to be well adapted for intermediate attenuative media of propagation. Its outcome is strongly influenced by parasitic signal reflections, coupling functions and scattering effects. On the other hand, the rise time method, less influenced by scattering phenomena, is dependent on the coupling functions (role of interfaces) and the experimental set-up. For a given experimental set-up a linear relation can be determined between the rise time and the ratio of travel time over the quality factor (T/Q) when a known source signal is simulated by a realistic linear viscoelastic model of propagation.

A signal transmitting and receiving system

Abstract: 1,207,386. Pulse discriminators; laser radar. GENERAL ELECTRIC CO. 25 Oct., 1967 [15 Feb., 1967], No. 48609/67. Headings H3T and H4D. [Also in Division G1] A transmitting and receiving system for use in communication and ranging applications comprises a transmitter of rapid rise time pulses of coherent radiation in the visible to near-infrared range and a receiver, for selectively receiving these pulses, comprising a cone shaped P-N junction type detector to receive the pulses and biased to enable avalanche multiplication on detection of radiation, which is connected to a tunnel diode pulse amplifier circuit. The transmitter may be a semi-conductor injection diode e.g. of gallium arsenide operating as a laser to produce very short rise time pulses e.g. of 20 nanoseconds in the 0A9 micron range. The receiver circuit, shown in Fig. 2, comprises a cone-shaped semi-conductor detector 10 having a P-type outer face connected to earth and an N-type inner face. This is biased from terminal 19 with a high positive voltage. The tunnel diode 21 is biased near its low voltage peak current by diode 25, connected to supply terminal 22 through resistor 27. Slow rise time signals from the detector, due to ambient light variations, pass through ceramic capacitor 20 and are conducted to earth through inductor 24, resistor 32 and diode 25, the circuit comprising tunnel diode 21 and resistor 28 having a higher impedance to such signals. Rapid rise time signals however, due to pulses received from the transmitter, are not passed by inductors 24 or 23 but are amplified by tunnel diode 21, and transmitted to transistor amplifier circuit 29-36. An output amplifier 37 is also provided. In an alternative receiver circuit, Fig. 4, the transistor amplifier circuit 29-36 is replaced by another tunnel diode amplifier. The output amplifier 37 may also include a tunnel diode. In the communications application of the apparatus, the pulse code modulator is associated with the transmitter at one location and a pulse decoding means with the receiver at another location. A typical ranging application is illustrated in Fig. 1 (not shown), and includes a display oscilloscope.

The effect of pulse rise time on nanosecond switching in magnetic thin films

Abstract: Nanosecond switching in thin magnetic films is studied by the application of easy-axis pulses with rise times from 0.4 ns to 50 ns. Switching time data with selected hard-axis bias fields and with the rise time as a parameter are presented. The switching mechanism depends on the percentage of flux switched during the ramp portion of the pulse. A comparison between the experimental data and numerical solutions based on the rotational model and the corresponding transverse signals shows that for pulses with amplitudes larger than the experimental astroid values (coherent rotation with 0.4 ns pulses) but with rates of increase S Oe/s, the stray field interaction between partially switched and unswitched regions causes appreciable flux to switch incoherently.

A 3 KW square wave inverter using power transistors

Abstract: In order to eliminate the dead time of an audio frequency square wave inductively pumped argon laser, a 1 µs rise time square wave inverter capable of switching 150 volts and 18 amperes has been built. This 3 kW unit can be operated at an adjustable fundamental frequency from 2.5 to 25 kHz.

G.S.R. systems which aid data analysis.

Abstract: The system of extracting the responses without the use of a series capacitor operates reasonably successfully. The time constant of the delay/low pass filter is a compromise—if it is lowered below nine seconds some responses will have a reading reduced by a few per cent, if raised above nine seconds the trailing edge of a response is lengthened and a greater time elapses before equilibrium is reached. Response percentages can be checked using the basal trace which also gives a record of long term changes in subject resistance. The timing of the leading edge of a response is accurate, facilitating latency (Edelberg, 1967) and response rise time measurements. Any delay through the divider can be considered at most as a fewmicroseconds.

An Experimental Comparison Between Direct and Indirect PAM by a High-Efficiency Microwave Frequency Multiplier with Varactor Diodes (Correspondence)

Abstract: Two pulse amplitude modulation (PAM) methods by a high-efficiency frequency multiplier with varactor diodes are compared. Typical results achieved for an X-band to Q-band tripler prove that the direct PAM is better than the indirect one under the same conditions. The former acts as a pulse shaper (PS), and has an output rise time smaller than the rise time of the output voltage of the modulator chain.