Showing papers on "Rise time published in 2021"

AlGaInP optical source integrated with fiber links and silicon avalanche photo detectors in fiber optic systems

Abstract: This study has clarified aluminium gallium indium phosphide (AlGaInP) optical source integrated with fiber links and silicon avalanche photodetectors in fiber optic systems. The output spectral power, rise time, signal frequency and resonance frequency for AlGaInP laser diode. The laser diode rise time, output spectral power and resonance/signal frequencies versus injection current and ambient temperatures are sketched. The silica doped germanium fiber link pulse broadening and the signal fiber bandwidth are investigated against temperature variations. The signal per noise ratio is related to Q value and bit error rate (BER) at the receiving point (Si avalanche photodetector (APD)) are sketched with temperature.

Inaccurate Switching Loss Measurement of SiC MOSFET Caused by Probes: Modelization, Characterization, and Validation

Abstract: SiC metal–oxide–semiconductor field-effect transistor (MOSFET) has a fast switching speed and high slew rate. However, its ultrashort switching time approximates the rise time and propagation delay of the measurement instruments, which results in an inaccurate assessment of the switching loss and challenges the thermal design of the power converter. In this article, aiming to reveal the principles of accurate measurement for the switching behavior of SiC MOSFET, insightful models are proposed for baseline probes and transient trajectories to characterize the measurement error of the switching losses. By using the Gaussian function, the mathematical models for the rise time, bandwidth, and propagation delay of the measurement instruments are achieved, which is also confirmed by the surveyed specifications of commercial probes. Concerning the accurate measurement, the turn-on and turn-off losses of the SiC MOSFET influenced by the rise time and propagation delay of probes are comprehensively modeled and characterized. With respect to different current probes, voltage probes, and gate driver resistances, extensive experiments are demonstrated to confirm the validity of the proposed models. The experimental findings are in line with the conducted predictions of the proposed models. It is found that, due to the very fast switching transients of the SiC MOSFET, the limited bandwidth and inevitable propagation delay of measurement instrument may result in a prominent error of the switching loss and impede the widespread implementation of the SiC MOSFET.

Efficient target acceleration using underwater electrical explosion of wire array

Abstract: The results of experimental studies together with numerical and analytical modeling showed that the acceleration of a target by employing the shock compression and water flow generated by the underwater electrical explosion of a wire array can be considered an efficient (up to ∼20%) approach. In experiments, a pulse generator with stored energy of ∼6.5 kJ, current amplitude of ∼380 kA, and rise time of ∼1.2 μs was used for underwater electrical explosion of a copper wire planar array. Streak shadow imaging and photonic Doppler velocimetry were applied to study the time-resolved velocity of the shock in water and an aluminum target in air, respectively. The targets, having different thicknesses and designs, were positioned at variable distances from the array. Experimental results showed that the target velocity evolution is characterized by an ns-timescale rise time peak with a subsequent decrease, which transfers to a μs-timescale increase up to its saturated value. Target velocities of up to 1360 m / s were measured. The experimental, numerical, and analytical modeling results showed that a temporally unmovable barrier, located between the exploding array and the target, allows one to increase the pressure in that location, which leads to higher shock velocity in the target.

Nanosecond-Pulsed Perovskite Light-Emitting Diodes at High Current Density.

Abstract: While metal-halide perovskite light-emitting diodes (PeLEDs) hold the potential for a new generation of display and lighting technology, their slow operation speed and response time limit their application scope. Here, high-speed PeLEDs driven by nanosecond electrical pulses with a rise time of 1.2 ns are reported with a maximum radiance of approximately 480 kW sr-1 m-2 at 8.3 kA cm-2 , and an external quantum efficiency (EQE) of 1% at approximately 10 kA cm-2 , through improved device configuration designs and material considerations. Enabled by the fast operation of PeLEDs, the temporal response provides access to transient charge carrier dynamics under electrical excitation, revealing several new electroluminescence quenching pathways. Finally, integrated distributed feedback (DFB) gratings are explored, which facilitate more directional light emission with a maximum radiance of approximately 1200 kW sr-1 m-2 at 8.5 kA cm-2 , a more than two-fold enhancement to forward radiation output.

High voltage nanosecond pulse generator based on avalanche transistor Marx bank circuit and linear transformer driver.

Abstract: Avalanche transistor Marx bank circuits (MBCs) are widely used in high voltage repetitive nanosecond pulse generators, but problems exist with respect to increasing the output voltage due to the limited pulsed current. Accordingly, a novel topology based on an avalanche transistor MBC combined with a linear transformer driver is proposed, the latter of which exhibits advantageous stress distribution and modular structure. A four-module prototype with four units in each module is developed in the laboratory. The output characteristics are investigated by varying important parameters such as the main capacitance, the number of conducting units, the number of cascaded modules, and the trigger signal time delay. The test results verify the validity of the proposed topology. For a 50 Ω resistive load, the prototype can generate pulses with an amplitude of 10.9 kV, a rise time of 3.3 ns, and a voltage superposition efficiency of 89%. The topology proposed in this paper may help to provide a method to further improve the output performance of avalanche transistor MBCs.

10-kV Transmission Line Experimental Platform for HEMP Immunity Test of Electrical Equipment in Operation

Abstract: To investigate the high-altitude electromagnetic pulse (HEMP) immunity of electrical equipment in operation, a 10-kV transmission line (TL) experimental platform is built in this paper. The conducted transient electromagnetic disturbance (TED) could be injected to the electrical equipment of 10-kV TL with power on or power off. The TED is produced by the pulsed current injection (PCI) generator, whose rise time is less than 20 ns and full width at half maximum is in the range of 500 ∼ 550 ns on short-circuit state with 60 Ω resistor. On the other hand, the 10-kV TL is equivalently designed in cross section to make its characteristic impedance being 330 Ω to conform to the value of practical case. The voltages and currents applied on the tested equipment can be measured at nano-second level simultaneously, which are of great use to learn the effect mechanisms and compare the results under different working conditions. Some 10-kV pin-type porcelain insulators are tested under different conditions, which shows the capacity of the proposed platform to test immunity of 10-kV electrical equipment.

Study of the electric field in a diffuse nanosecond positive ionization wave generated in a pin-to-plane geometry in atmospheric pressure air

Abstract: The dynamics of a nanosecond positive ionization front generated in a pin-to-plane geometry in atmospheric pressure air is simulated using a 2D axisymmetric drift-diffusion fluid model. For a 16 mm gap and a sharp pin electrode, the plateau of the applied voltage is varied between 40 and 60 kV and the rise time is varied between 0.5 and 1.5 ns or a DC voltage is applied. The discharge ignition time and the voltage at ignition are shown to depend mostly on the voltage rise time. The connection time, i.e. the time for the ionization wave to ignite, propagate and connect to the plane is shown to strongly depend on both the values of the voltage plateau and rise time. For all cases, the discharge has a conical shape with a maximal radius of about 8 mm as it connects to the grounded plane. The average propagation velocity of the ionization front is found to vary in the range 3.1 to 8.5 mm ns−1. These values are in rather good agreement with experiments. Temporal evolutions of the electric field are recorded on the symmetry axis at different positions in the gap. At each location, an increase and decrease of the electric field is observed as the ionization front, propagating from the pin to the plane, passes the studied point, in accordance with experimental observations. Finally, for a voltage plateau of 55 kV and a rise time of 0.5 ns, a temporal sampling of 100 ps is shown to be sufficient to capture the dynamics of the electric field during the ionization front propagation when it passes close to the middle of the gap. Conversely, a temporal sampling of 10 ps is required when the ionization wave is close to both electrodes, or during the fast redistribution of the electric field after the connection of the ionization front at the cathode.

An Auto-Balancing Capacitance-to-Pulse-Width Converter for Capacitive Sensors

Abstract: A novel auto-balancing capacitance-to-pulse-width converter (CPC) that uses sinusoidal excitation, and operates in a closed-loop configuration, is presented in this paper. Unlike most of the existing CPCs, the proposed interface circuit is compatible with both single-element and differential capacitive sensors. In addition, it provides a pulse-width modulated (PWM) signal which can easily be digitized using a counter. From this PWM signal, a ratio output is derived when a single-element sensor is interfaced, and a ratiometric output is obtained for a differential sensor. The final digital output is independent of the nominal capacitance of the sensor and has a linear characteristic irrespective of the sensor characteristic being linear or inverse. The CPC is designed such that the PWM output depends on the change in the sensor capacitance alone. It is insensitive to parasitic capacitance and has very low sensitivity to the non-idealities of the components and ICs used. The effects due to some of the non-idealities are automatically corrected by the negative feedback based auto-balancing employed. The effect of component mismatch is significantly reduced by a one-time correction mechanism. These benefits are achieved without the use of any complex or expensive analog building blocks. The prototype exhibits a maximum non-linearity error of less than 0.7%, a resolution of 13.02 effective number of bits (ENOB), a signal-to-noise ratio (SNR) of 80.12 dB, and a rise time of 5 ms. Thus, the proposed simple, yet effective, low-power, low cost, auto-balancing CPC can be used to interface a wide range of existing and new capacitive sensors to digital systems

Response of 10-kV Metal-Oxide Surge Arresters Excited by Nanosecond-Level Transient Electromagnetic Disturbances

Abstract: Nanosecond-level transient electromagnetic disturbance (TED), including very fast transient overvoltage caused by operation of disconnectors, high-altitude electromagnetic pulse, and many other fast transients may interfere or even damage the electrical equipment. As one of the main overvoltage protective equipment, the protective performance of metal-oxide surge arresters (MOAs) under nanosecond-level TED should be investigated and then compared with that under microsecond-level TED, especially the lightning impulse. Based on a testing platform containing a 400-kV pulse generator with adjustable rise time from 5 to 100 ns, the behaviors of nonlinearity, fast impulse response, and converting impedances of three types of 10-kV MOAs under TED with different rise time were explored experimentally in this article. The peak residual voltages of 10-kV MOAs under TED with the rise time of 5 ns at 5 kA are 50.2–60.7% higher than those under the lightning impulse. The rise time of TED has significant influence on the peak voltage and impedance converting behaviors of MOAs. A circuit model of 10-kV MOAs under nanosecond-level TED is built and validated by experimental results, which can be applied in insulation coordination and design of protective devices against TED.

Antenna Array with TEM-Horn for Radiation of High-Power Ultra Short Electromagnetic Pulses

Abstract: An antenna array with short shielded transverse electromagnetic horns (S-TEM-horns) for emitting high-power radiation of ultra-short electromagnetic pulses (USEMP) has been created and researched. The antenna unit consists of an ultra-wideband antenna array with four S-TEM horns, with each connected to a two-wire HF transmission line, and these four lines are connected to an antenna feeder. This feeder is connected to a semiconductor generator with the following parameters: a 50 Ohm connector, 10–100 kV high-voltage monopolar pulses, a rise time of about 0.1 ns, FWHM = 0.2–1 ns, and pulse repetition rates of 1–100 kHz. The antenna array was designed and optimized to achieve a high efficiency of about 100% for the antenna aperture by using a 2 × 2 array with S-TEM-horns, with shielding rectangular plates for the return current. The transient responses were studied by simulation using the electromagnetic 3D code “KARAT” at the time domain and experimentally with the use of our stripline sensor for measurement of the impulse electrical field with a 0.03 ns rise time and a 7 ns duration at the traveling wave. The radiators were emitting USEMP waves with a hyperband frequency spectrum of 0.1–6 GHz. The radiation with an amplitude of 5–30 kV/m of the E-field strength at a distance of up to 20 m was successfully applied to test the electronics for immunity to electromagnetic interference.

A Nonlinear Transmission Approach to Compressing Rise and Fall Time in Picosecond Pulse Generation

Abstract: This article presents the generation scheme of picosecond (ps) pulses based on both step recovery diode (SRD) topology and nonlinear transmission line (NLTL) scheme with a focus on simultaneous rise and fall time compression. First, the SRD topology is suggested and investigated for manifesting the capability of pulse compression. The SRD solution is then integrated with different NLTL schemes for alienating and achieving rise or fall time compression in the ps regime. It is observed that single NLTL integration only sharpens the rising or falling edge at the same time. To overcome this challenge, two NLTLs having different diode polarities are then integrated with SRD topology-based ps pulse generator to compress rise and fall time simultaneously. The theory of NLTL is developed in each case, and based on it, the shortest rise and fall time is selected for the final design. Several parameters that are responsible for waveform distortion are also investigated in detail as well. Finally, we have fabricated four different pulse generators in which the first three only compress the rise time whereas the fourth one is responsible for both rise and fall time compressions. The overall pulse duration for the first three generators falls within 80–95 ps having different ringing levels and they are based on rise time compression only. The pulse duration for the fourth pulse generator is almost 25 ps having a detailed ringing level of −14.24 dB and full-width at half-maximum (FWHM) of 10.1 ps based on both rise and fall time compressions. Finally, all these pulse generators are compared with the state of the arts in the literature where they utilize different techniques for sharpening and the superiority of our proposed designs is provided. These generators will find their key role and will be the best candidates for ultra-wide band (UWB) radars for electromagnetic imaging and sensing applications, ultrafast electronic techniques including edge sharpening, future oscilloscopes, comb, or pulse generators, and geophysical exploration.

Revisiting the Calculation of the Early Time HEMP Conducted Environment

Abstract: The early time high altitude electromagnetic pulse conducted environment calculation is revisited by using the transmission line (TL) theory and including high-frequency corrections that were not present in the earlier studies. Waveform salient parameters, such as the current peak, rise time, and pulsewidth, are studied as a function of a number of parameters involved in the calculation. The obtained cumulative distribution functions of the parameter probabilities are discussed and compared with the existing standards for the HEMP protection. The high-frequency correction to the TL model results in a decrease of the current amplitudes of 15–20%. For the highest currents, rise times in the range of 25 ns are obtained. A less significant impact was found in the calculation of the pulsewidth, which was increased to about 150 ns.

A High-Voltage Pulsed Power Supply With Online Rise Time Adjusting Capability for Vacuum Tubes

Abstract: Vacuum tubes such as gyrotrons and magnetrons require a specific range of high-voltage pulse rise time for their proper operation. Otherwise, unavoidable operation modes or even arcs may take place in the vacuum tubes. Hence, the capability of the adjustable output pulse rise time is very promising for pulsed power supplies when they are dedicated to vacuum tubes. This article proposes a high-voltage series stacked insulated gate bipolar transistor (IGBT) switch with rise time adjusting capability to evolve the pulsed power supply abilities. The rise time adjustment is carried out using a low-voltage ramped shape signal provided for all the IGBTs via a multi-winding transformer. In this way, the IGBTs are turned on as fast as possible with specific delays. The sequential turn on process of the IGBTs forms the output pulse rising edge. Unlike the extant strategies for controlling the turn on speed of the IGBTs, the dissipated power of the proposed method is negligible. The power associated with adjusting the output pulse rise time is recovered to the pulsed power supply using a simple and low-voltage dc/dc converter. The proper performance of the proposed structure is evaluated using simulations and experimental prototyping.

High power and high repetition frequency sub-nanosecond pulse generator with two-phase immersion cooling technique

Abstract: In this paper, a 60-stage Marx circuit with the two-phase immersion cooling technique is presented. The performance parameters of the pulse generator with phase change immersion cooling and forced air cooling are compared. The results show that the maximum repetition rate is increased from 80 to 260 kHz, the pulse drift is significantly reduced from 900 to 200 ps, and the temperature rise of transistors is controlled effectively to enhance the stability of the amplitude. We also studied the influence of temperature on the turn-on and turn-off processes of the transistors to show the importance of heat management under high repetition conditions. Finally, a pulse generator is developed with the repetition rate of 200 kHz, the rise time of 180 ps, and the amplitude of 2350 V on a matched 50 Ω resistive load, which can work for more than 30 min.

Chaotic-based particle swarm optimization algorithm for optimal PID tuning in automatic voltage regulator systems

Abstract: Introduction. In an electrical power system, the output of the synchronous generators varies due to disturbances or sudden load changes. These variations in output severely affect power system stability and power quality. The synchronous generator is equipped with an automatic voltage regulator to maintain its terminal voltage at rated voltage. Several control techniques utilized to improve the response of the automatic voltage regulator system, however, proportional integral derivative (PID) controller is the most frequently used controller but its parameters require optimization. Novelty. In this paper, the chaotic sequence based on the logistic map is hybridized with particle swarm optimization to find the optimal parameters of the PID for the automatic voltage regulator system. The logistic map chaotic sequence-based initialization and global best selection enable the algorithm to escape from local minima stagnation and improve its convergence rate resulting in best optimal parameters. Purpose. The main objective of the proposed approach is to improve the transient response of the automatic voltage regulator system by minimizing the maximum overshoot, settling time, rise time, and peak time values of the terminal voltage, and eliminating the steady-state error. Methods. In the process of parameter tuning, the Chaotic particle swarm optimization technique was run several times through the proposed hybrid objective function, which accommodates the advantages of the two most commonly used objective functions with a minimum number of iterations, and an optimal PID gain value was found. The proposed algorithm is compared with current metaheuristic algorithms including conventional particle swarm optimization, improved kidney algorithm, and others. Results. For performance evaluation, the characteristics of the integral of time multiplied squared error and Zwe-Lee Gaing objective functions are combined. Furthermore, the time-domain analysis, frequency-domain analysis, and robustness analysis are carried out to show the better performance of the proposed algorithm. The result shows that automatic voltage regulator tuned with the chaotic particle swarm optimization based PID yield improvement in overshoot, settling time, and function value of 14.41 %, 37.91 %, 1.73 % over recently proposed IKA, and 43.55 %, 44.5 %, 16.67 % over conventional particle swarm optimization algorithms. The improvement in transient response further improves the automatic voltage regulator system stability for electrical power systems.

High voltage nanosecond pulse generator based on diode opening switch and magnetic switch

Abstract: Low-temperature plasma technology is widely used in various industrial fields, which require the plasma to be of large volume, diffuse, and stable. Furthermore, previous studies have shown that better plasma performance has been obtained by using generators with a high voltage, a high repetition rate, a fast rise time, and a short pulse duration. In this paper, a novel topology is proposed for such generators, which is based on magnetic switches and diode opening switches. A prototype is developed, and its output characteristics are investigated by varying essential parameters, such as the load resistance and the power supply voltage. The experimental results show that it can generate pulses with a voltage of 30.6 kV, a rise time of 7.1 ns, a pulse duration of 8.2 ns, and a maximum repetition rate of 12 kHz on a 300 Ω resistive load. The prototype has been successfully used to drive uniform plasma in ambient air. In the proposed topology, a diode is added to make the magnetic cores independent of each other, significantly simplifying the design calculation. It may help develop nanosecond solid-state generators.

All-solid-state bipolar pulsed generator based on linear transformer driver and push–pull circuit

Abstract: All-solid-state linear transformer drivers (LTDs) are widely used in high-voltage repetitive nanosecond-pulsed generators, and only a few LTD generators can output bipolar rectangular waves currently. Furthermore, owing to the large reverse overshoot when the output pulse width is long, fewer LTD generators can achieve a rectangular wave output with a microsecond pulse width. In this study, a bipolar LTD circuit topology based on a push–pull circuit is proposed for irreversible electroporation. In this topology, a single-stage LTD module has four push–pull branches in its primary winding to achieve a bipolar output and a short-circuited winding with two resistor–capacitor–diode snubbers to suppress forward/reverse overshoot. A single-stage LTD module and a 12-stage LTD have been tested, and the results show that they can output bipolar rectangular pulses with variable parameters. When the output pulse width is 100 ns to 1 µs, the maximum output voltage amplitude is 5.74 kV, the rise time is 29.1 ns, and the reverse overshoot at 1 µs is 2.9%. When the output pulse width is 1–8 µs, the maximum output voltage amplitude is 2.93 kV, the rise time is 24.3 ns, and the reverse overshoot at 8 µs is 11.3%.

Low-Power Area-Efficient LDO With Loop-Gain and Bandwidth Enhancement Using Non-Dominant Pole Movement Technique for IoT Applications

Abstract: A new Low Drop-Out (LDO) voltage regulator with off-chip capacitor for low power applications is presented. The LDO takes advantage of non-dominant pole movement technique to improve loop-gain and Unity Gain Frequency (UGF). Tangible improvements were obtained while supporting a large load capacitor and low-power consumption. The proposed LDO 1) consumes low quiescent current (47.3% current efficiency (CE) at $10~\mu \text{A}$ load current bias circuit inclusive), 2) is area-efficient (no multi-gain amplifiers), and 3) enjoys a short response time in the active-mode with its adaptive bandwidth expansion and loop-gain enhancement technique, while 4) maintaining 99.94% CE in the full-load condition. A prototype chip with TSMC 180 nm CMOS technology was fabricated for detailed characterisation. The measured output voltage of the LDO was 1.65 V with 1.8 V input, consuming $11~\mu \text{A}$ quiescent current including the bias circuit current. The load regulation was 10 mV when load current changes from 30 nA to 50 mA with fall and rise time of 10ns.

A Novel Avalanche Transistor-Based Nanosecond Pulse Generator With a Wide Working Range and High Reliability

Abstract: Avalanche transistor (AT)-based repetitive nanosecond pulse generators with high amplitude, fast rise time, narrow pulse width, and low jitter have been widely developed and applied in numerous fields. However, relatively little research has been carried out on the positive nanosecond pulse generation with high flexibility in a wide range of output voltage amplitude. In this article, a novel AT-based Marx circuit (MC) topology adopting base-triggering method is proposed to avoid the formation of current filamentation inside the transistors and resolve the contradiction between high-voltage output and high repetition rate operation. A $6\times 10$ -stage MC prototype is implemented with optimized parameters to validate the feasibility of the proposed topology. The conduction processes of transistors show that, with the injection of additional base current, the switched-ON modes are transformed, which contributes to reliable conduction of transistors even without sufficient overvoltage ramp. With the adoption of inner triggering loops, the minimum working voltage of the prototype is extended to 1150 V. The operation characteristics of the generator in the whole operation range are investigated in depth. Experimental results illustrate that, at the 75- $\Omega $ match-ended coaxial cable, the prototype is capable of generating positive pulses with an adjustable voltage amplitude in the range of 6.50 to 12.39 kV, a basically consistent rise time of 3.6 ns and pulse width of 19.5 ns. Over 107 successive pulses are generated at a maximum repetition rate of 1 kHz without any device failure.

Performance enhancement of ZnGa2O4 Schottky type deep-ultraviolet photodetectors by oxygen supercritical fluid treatment

Abstract: For semiconductor device applications such as FinFET, MEMS, 2D materials, and wide bandgap materials, reliability is one of the most powerful key factors for commercialization in the industry. ZnGa2O4 deep ultraviolet (DUV) photodetectors (PDs) have been studied for their reliability and hence have been examined using the accelerated life test (ALT), which has shown the poor reliability of the device and device degradation such as high leakage current and poor rise time falling time (Tr/Tf) ratios. Therefore, in this paper, we proposed a method to enhance device performance by a non-destructive post-treatment method with low temperature and high-pressure oxygen supercritical fluid (SCF-O) for DUV photodetectors. This method not only improved the device performance but allowed it to perform even better than the as-grown sample. X-ray photoelectron spectroscopy, X-ray diffraction, and atomic force microscope analyses corroborated better crystallinity with a smaller number of interstitial defects followed by mathematical modelling using density functional theory. The on/off ratio increased from 102 to 105 and had an improved rise time and fall time ratio (Tr/Tf). The responsivity for the SCF-O treated ZnGa2O4 PDs (@240 nm) increased to 639 A/W as compared with that (486 A/W) of as-grown sample. The first-principles DFT-GGA calculations were used to explain the relationship between the formation energies of defects in the oxygen treatment on the ZnGa2O4 epitaxial layers and agreed well with the experiment results. As per our knowledge, our study was the first to present this post-treatment method for DUV photodetectors, which could increase the lifetime of semiconductor devices.

A 3.6 mW 60 GHz Low-Noise Amplifier With 0.6 ns Settling Time for Duty-Cycled Receivers

Abstract: This letter presents the first duty-cycled low-noise amplifier (LNA) operating in the $V$ -band (40–75 GHz). The amplifier employs a two-stage cascode topology and focuses on low power consumption and therefore fast settling times. The switching is achieved by using inverters at the common-gate (CG) transistor of the cascode stage. This control technique enables adapting the duty-cycle and, therefore, the data rate depending on the required performance. The LNA can be operated in an oversampling mode fulfilling a wake-up function and consuming only $22~\mu \text{W}$ for a data rate of 294 kb/s or in continuous mode dissipating 3.6 mW. A settling time of 0.6 ns, a rise time of 19 ps, and a fall time of 27 ps have been experimentally demonstrated on a prototype fabricated in a 22 nm fully-depleted silicon-on-insulator (FD-SOI) technology. The measurement results include a peak gain of 18 dB, a 3-dB bandwidth of 18 GHz, an average noise figure (NF) of 4.9 dB within the 3-dB band, and an input 1 dB compression point (P1dB) at 60 GHz of −21.1 dBm.

Development of a High Peak Voltage Picoseconds Avalanche Transistor Based Marx Bank Circuit

Abstract: Avalanche transistor-based Marx bank circuit (MBC) is widely used to generate high voltage nanosecond pulses with high amplitude, high repetition rate, fast rise time, and low jitter. Researchers have tried to modify the circuit structure by using parallel or series avalanche transistors to increase peak power. However, in this work, the detailed process of analyzing and designing a compact Marx generator using avalanche transistors will be described. The purpose of this article is to report our experimental observations on the mechanism of operation of the MBCs. By studying the influence of amplitude and pulse width of the trigger circuit, a Gaussian pulse with a rising edge of 160 ps, full width at half maximum (FWHM) of 660 ps, and amplitude of 5000 V are obtained. The design improves the output voltage and pulse repetition frequency (PRF) effectively while reducing the use of the number of transistors. Based on the conventional principles of avalanche transistors and Marx circuit, a list of useful and interesting conclusions obtained from experiments will be reported.

Determining the Electrical Charging Speed Limit of ReRAM Devices

Abstract: Redox-based random-access memory (ReRAM) has the potential to successfully address the technological barriers that today’s memory technologies face. One of its promising features is its fast switching speed down to 50 ps. Identifying the limiting process of the switching speed is, however, difficult. At sub-nanosecond timescales three candidates are being discussed: An intrinsic limitation, being the migration of mobile donor ions, e.g., oxygen vacancies, the heating time, and its electrical charging time. Usually, coplanar waveguides (CPW) are used to bring the electrical stimuli to the device. Based on the data of previous publications, we show, that the rise time of the effective electrical stimulus is mainly responsible for limiting the switching speed at the sub-nanosecond timescale. For this purpose, frequency domain measurements up to 40 GHz were conducted on three Pt\TaOx\Ta devices with different sizes. By multiplying the obtained scattering parameters of these devices with the Fourier transform of the incoming signal, and building the inverse Fourier transform of this product, the voltage at the ReRAM device can be determined. Finally, the rise time of the voltage at the ReRAM device is calculated, which is a measure to the electrical charging time. It was shown that this rise time amounts to 2.5 ns for the largest device, which is significantly slower than the pulse generator’s rise time. Reducing the device’s rise time down to 66 ps is possible, but requires smaller features sizes and other optimizations, which we summarize in this paper.

Influence of Rise Time and Fall Time on Surface Discharge Characteristics of PEEK Under Positive Repetitive Square Voltage

Abstract: In this paper, the surface discharge current pulses of PEEK (polyether-ether-ketone) under positive repetitive square voltage are measured The effects of voltage rise time and fall time on pulse parameters of discharge current, instantaneous voltage of discharge and time-lag of discharge are analyzed in detail The results show that the amplitude of discharge current and the instantaneous voltage of discharge decrease, and the time-lag of discharge and the dispersion of time-lag increase with the increase of voltage rise time With the increase of voltage fall time, the amplitude of discharge current decreases and the instantaneous voltage of discharge, the time-lag of discharge and the dispersion of time-lag increase To analyze the influence mechanism of voltage rise time and fall time on surface discharge, the accumulation of surface charge under repetitive square voltage is regarded as a periodic process Besides, the correlation between forward discharge and back discharge in the process of discharge is analyzed, and the development of discharge is analyzed by using the time-lag theory Furthermore, the relationship between instantaneous discharge voltage and voltage slew rate is revealed, and the surface charge accumulation processes under different voltage rise times and fall times are compared to reveal the influence mechanism of rise time and fall time on the surface discharge under positive repetitive square voltage

Multi-objective genetic algorithm optimization of linear proportional solenoid actuator

Abstract: Linear proportional solenoid (LPS) is widely applied in different linear motion control systems as the electromagnetic actuator since its high reliability and low cost. LPS is difficult to optimize by changing a single variable due to amounts of structural design parameters, and each design parameter has a nonlinear relationship with the static electromagnetic force. This paper aims to improve LPS’s push force and response performance through magnetostatic finite element analysis (FEA) by ANSYS MAXWELL. This study compares FEA 2D model, 3D model and measurement results underrated coil current to verify the accuracy of FEA 2D model. In order to reveal the nonlinear relationship between shape design parameters and electromagnet design objectives, this study compares the influence degree of each variable on each design objective by conventional type LPS 2D FEA model. And for the purpose of improving LPS’s push force and response performance, a multi-objective optimization method has been proposed in this study based on genetic algorithm (GA) and magnetostatic FEA 2D model for optimizing the shape design parameters. All the study results were validated in both static conditions and dynamic conditions. The comparison between manufactured optimal type and conventional type results shows that the static push force in working stroke is improved 30.1%, displacement step response rise time is reduced 5.2% and 43.4%, and force step response rise time is reduced 20.5% and 44.6% with different return spring stiffness. Above all, LPS static and dynamic performance has been improved directly and the validation of proposed optimization method is verified in this paper.

On the Junction Temperature Extraction Approach With a Hybrid Model of Voltage-Rise Time and Voltage-Rise Loss

Abstract: Temperature sensitive electrical parameter (TSEP) approaches are widely employed in the junction temperature ( $T_{j}$ ) detection and prediction of power devices, especially the switching parameter. In this article, the voltage-rise time and its loss during the turn-off process are used as the TSEP index for the detection of junction temperature because of the coupling relationship with the maximum junction temperature. In addition, the effect of junction temperature on the current-fall time and its loss is compared. The theoretical analysis is verified by SABER simulation and H-bridge inverter circuit platform. It is established that the model based on voltage-rise time ( $t_{\mathrm {rv}}$ ) and voltage-rise loss ( $E_{\mathrm {rv}}$ ) is a viable model with good linearity, fixed sensitivity, and offers nondestructive insulated gate bipolar translator (IGBT) junction temperature extraction.