Rise time

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

Solid State Pulsed Power Electronics

Abstract: Publisher Summary This chapter reviews some of the most typical semiconductors and topologies used for generating repetitive unipolar and bipolar high-voltage pulses based on semiconductor devices. The demand for high-voltage modulators to generate repetitive high-voltage pulses with optimized performance and characteristics, based in solid-state technology, still needs enhancement of the Volt–Ampere capabilities and switching speed of modern power semiconductors. The PIN diode-based Silicon Avalanche Sharpener (SAS) is a sharpening device that shortens the pulse rise time. It works normally reverse biased, a slow rise time, and short reverse pulse being applied to the SAS in order to avalanche it. The gate current after charging or discharging of gate stray capacitances is almost null, and therefore, needed gate power is very low. IEGT are IGBT-like structures with deep trench-gates and wider cell widths. Hole concentration in the P layer under the gate electrode is enhanced due to hole accumulation, similar to the conductivity modulation of a PIN diode, lowering the on-state voltage and increasing the efficiency specially in high-voltage devices.

Comparison of sonic boom rise time prediction techniques

Abstract: An important quantity in determining the loudness of sonic booms outdoors is the rise time. In the absence of turbulence, the rise time is dictated by frequency‐dependent loss mechanisms in the atmosphere including relaxation, viscosity, and thermal conduction. Two techniques have been used to predict rise times of sonic booms. The technique developed by Pestorius and Blackstock numerically steps a weak shock through the atmosphere accounting for frequency‐dependent absorption and time‐dependent wave steepening independently at each step. This technique has been extended by Bass and Raspet to include absorption and dispersion by the vibrational relaxation of N2 and O2 in the presence of H2O. The second technique is to apply the augmented Burgers’ equation to determine a steady‐state asymptotic shock profile. This approach is strictly valid only for a plane shock wave with a duration much greater than the rise time. This letter compares predicted rise times using these two approaches. The input waveforms were assumed to be N waves with a linear rise at the front and rear of the shock. These calculations show that N waves of duration greater than 100 times the rise time can be treated as steady‐state shocks. The rise time for shock waves of shorter duration cannot be determined using the steady shock assumption.

Investigation on push-pull polymer Mach-Zehnder interferometer electro-optic switches using improved 3-D mode propagation analysis method

Abstract: By introducing normalized mode excitation coefficient and total mode excitation coefficient, we improve the 3-D mode propagation analysis (MPA) method for convenient design and analysis of multimode interference (MMI) coupler. With the improved 3-D MPA method and point-matching method, we present a novel formulation technique to analyze the low- and high-frequency characteristics for the impedance-matched polymer Mach-Zehnder interferometer electro-optic (EO) switch based on MMI couplers. As an application, under 1550 nm, optimization and simulation performed for the designed device reveal low driving voltage of 1.375 V with short EO region length of 5 mm. The insertion loss and extinction ratio are less than 3.75 dB and more than 42 dB, respectively. The microwave characteristic impedance is about 49.6 Ω, and due to the less mismatch between lightwave velocity and microwave velocity, the estimated cutoff switching frequency is up to 263 GHz with the 10–90% rise time and fall time about 1.90 ps under the operation of step-style square-wave switching signal. This theoretical cutoff switching frequency is almost 1.53 times of that of our previous reported shielded EO switch with similar design technique.

A study of noncoherent rotational switching for thin magnetic films

Abstract: Thin magnetic film switching was investigated for fields near those needed for pure rotation. Experimentally the films were switched using <0.4 ns rise time field pulses. The resulting flux changes were detected in the easy and hard direction with a response time of 0.6 ns. Measurements were made for pulses both longer and shorter than the magnetization switching times. By analyzing the voltage waveforms and flux changes, it was concluded that instabilities and rapid rearrangements of the magnetization can occur within a few nanoseconds, causing anomalous results during switching. Equations of existing quantitative switching models-pure rotation, spin-wave, and stripe domain-were solved with a digital computer. To better compare theory and experiment, the solutions were modified to account for the sense system's finite rise time. It was found that none of the existing models adequately described the switching processes for low amplitude magnetic fields. However, qualitatively, the stripe domain model best fit the experimental data.

Conductance-transient analysis of thick-film tin oxide gas sensors under successive gas-injection steps

Abstract: Dynamically characterizing the electrical response of chemical sensors is a strategy to improve their selectivity. In this paper, the conductance transient of thick-film tin oxide gas sensors under successive step rises in the gas concentration is analysed. The transient response of three thick-film tin oxide gas sensors in the presence of organic solvent vapours (toluene, o-xylene and ethanol) has been measured. As a main result, it has been found that, although the first step in the conductance-transient rise time is concentration independent, for the second and successive steps, decreases and becomes concentration dependent. This behaviour has been modelled successfully with a nonlinear diffusion - reaction model. The measured set of rise times is characteristic for each sensor - gas pair and may give useful information for gas recognition. Furthermore, the successive injection of gas samples during the sensor-calibration procedure may be a time-saving technique.