Rise time

About: Rise time is a research topic. Over the lifetime, 4748 publications have been published within this topic receiving 47512 citations.

Physics of piezoelectric shear mode inkjet actuators

Abstract: This thesis describes work on piezoelectric shear modeactuators used in dropon- demand ink printing applications.These actuators comprise an array of ink channels micromachinedinto bulk Pb(ZrxTi1-x)O3(PZT) ceramics.During this study, a new pulsed spectroscopic technique wasdeveloped to investigate functional properties of a singlechannel wall of the actuator. The pulse technique is based onrecording the transient current in response to a short voltagepulse applied to the channel wall. An electric field appliedperpendicular to the polarization will cause a shear motion ofthe wall. If a voltage pulse with a fast rise time is highenough in amplitude to actuate the wall, it will act like atuning fork and oscillate at it’s resonant frequencies.Because of the piezoelectric effect, the mechanicaloscillations of the wall can be seen as oscillations in thetransient current.Beside the pulsed technique, dielectric spectroscopy,ferroelectric hysteresis loop tracing and stroboscopy were usedas characterization techniques. The results obtained arediscussed in respect to temperature dependence, frequencydispersion, ferroelectric fatigue and acoustic resonancemodes.Another field of interest was the temperature inside theactuator. An electric circuit, based on the voltage dividerprinciple, was built to monitor the ink temperature as afunction of the printing pattern.‘Dummy walls’,located at the beginning and the end of the channel wall array,were used as temperature sensing elements. Since the dielectricpermittivity of the PZT channel walls depends on temperature,the capacitance of the‘dummy walls’changes withtemperature. The information obtained by this measurementtechnique was used to investigate alternative materials for thepassive components of the actuator.A further part was the development of a new actuator designcalled a‘Chevron actuator’. Chevron actuatorsinclude an additional PZT layer with polarization in theopposite direction to the base plate polarization. Thus, thewhole channel wall is used as the active part instead of usingjust the upper half as in the standard actuator. The mainadvantage of this technique is a reduced power consumption ofthe actuator and therefore less heat dissipation.Different approaches were used to construct Chevronactuators. Experiments determined the efficiency of theactuators and these results were used to make improvements. TheChevron actuators were characterized by the above mentionedtechniques and compared with standard Xaar actuators.

High-speed large-area surface-normal multiple quantum well modulators

Abstract: Since 1998, the Naval Research Laboratory has been developing modulating retro-reflectors (MRR) for free-space optical (FSO) communication links. Using an MRR is beneficial for asymmetric links containing one node with weight or power constraints, such as ground-to-air links. An MRR configuration shifts most of the power, weight, and pointing requirements onto one node. To close an MRR link at any significant distance, the area of the modulator must be fairly large. Using a large area limits the data rate, since capacitance is proportional to area. Resistance also depends on device size, although not in the same manner. To increase the data rate, we designed a top metal contact that diminishes the effect of the semiconductor resistivity. Using this new top contact design decreases the rise time from approximately 2.6 μs to 60 ns using the same wafer structure. However, increasing the data rate increases the power input and results in self-heating, which changes the optimal operating wavelength of MQW modulators. Accordingly, a new coupled quantum well structure is designed. The new design lowers the required drive voltage, which in turn lowers the power consumption, increases yield, and simplifies drive circuitry. The lower power input also reduces the modulation rate dependence of the wavelength.

A high‐voltage pulser circuit with subnanosecond rise time

Abstract: A fast (≤1 ns rise time) high‐voltage pulser circuit was developed using 2N5551/2N5550 transistors in avalanche mode as switching elements. This circuit has transistors in series stack configuration and provides ∼2 kV amplitude and ≤1 ns rise time into 50 Ω with a 13 ns delay and <500 ps jitter. A simple arrangement to generate two symmetrical opposite polarity pulses from single pulse of either polarity is also presented.

Achieving a nonovershooting transient response with multivariable dynamic output feedback tracking controllers

Abstract: We consider the use of dynamic output feedback control to improve the transient response to a step input, for invertible multivariable systems. A method is given for designing a linear time-invariant output feedback controller to asymptotically track a constant step reference with zero overshoot and arbitrarily small rise time, under some mild assumptions.

Ultra-wide bandwidth measurement of partial discharge current pulses in SF6

Abstract: This paper presents ultra-wide bandwidth measurements of partial discharge (PD) current pulses. Using a 33 GHz bandwidth oscilloscope together with a direct, matched coaxial connection to the PD source, pulses have been characterized with a greater degree of accuracy than has previously been achieved, with a minimum observed rise time of 24 ps. The PD source consists of a sharp protrusion in pressurized sulfur hexaflouride (SF6) with a tip radius of 25 µm. Both positive and negative corona pulses were recorded, revealing previously indistinguishable frequency content and features such as the appearance of groups of multiple component pulses occurring within a nanosecond time scale. The upper bandwidth limitation of the complete measurement set-up was established. This was calculated by cross-correlating current pulses with corresponding pulses filtered at lower frequencies to determine their similarity. The tendency for multiple consecutive pulses to occur within a short time period was evident. The results provide valuable data for researchers investigating fundamental physical phenomena of SF6 ionization and PD activity.