GaN power IC normally-on and normally-off transistors technology and simulation

GaN technology has been waiting to be widely adopted because of its specific technical requirements. Integration of transistor and driver in a single die will enable to overcome problems with gate driving, high cost of circuit and low device reliability. This paper demonstrates technology of GaN-on-Si normally-on and normally-off transistor with different p-GaN cap-layer thickness as well as simulation of these devices. The simulation data confirm experimental results. P-GaN cap-layer thickness affects the current channel density: the more p-GaN thickness, the less channel density. The fabricated transistors have a maximum drain current in open state of about 800 mA/mm.

Pulsed high-current discharge in water: adiabatic model of expanding plasma channel and acoustic wave

This paper presents the results of a theoretical and experimental study of the use of a pulsed discharge in water to obtain a strong acoustic wave in a liquid medium. A discharge with a current amplitude of 10 kA, a duration of 400 ns, and an amplitude pulsed power of 280 MW in water at atmospheric pressure created an expanding acoustic wave with an amplitude of more than 100 MPa. To describe the formation of the discharge channel, an isothermal plasma model has been developed, which made it possible to calculate both the expansion dynamics of a high-current channel and the strong acoustic wave generated by it. Our calculations show that the number density of plasma in the channel reaches 10^20 cm^(–3), while the degree of water vapour ionization is about 10%, and the channel wall extends with a velocity of 500 m/s. The calculations for the acoustic wave are in good agreement with measurements

The discharge initiation in vacuum gap by moderate intensity optical range radiation

The hypothesis of discharge initiation in vacuum gap by optical range radiation based on previously obtained experimental data. During the laser pulse interaction with electrode erosion products the glow discharge has ignited. In result of ioniza-tion-overheating instability the discharge has had current channel contraction and has transferred to arc. The dependences of material of target thermo dynamical parameters on the minimal and threshold laser pulse energy have demonstrated. The threshold laser pulse energy – the energy which enough to effective impact on the laser plasma.

CURRENT FLOW DYNAMICS IN PLASMA OPENING SWITCH

The electromagnetic fields and processes of current flow in the plasma channel of the plasma opening switch were considered in the electron hydrodynamics approximation. Taking into account the nature and features of the current flow through the plasma filled region of plasma opening switch allowed to obtain the structure of the current channel and its dynamics along the plasma. The current flow is a wave process. When this wave reaches the boundary of plasma it seems to be the break of current at this moment. The criterion of this break is obtained.

Implementation of the adaptive quantization method in digitally controlled measuring generators

Measuring generators with digital control, in particular power calibrators, used to calibrate electricity meters, contain a digital-to-analog converter (DAC) that converts codes of the generated signal into voltage. Signal codes are stored in the generator memory. A truncation discreteness error (quantization noise) arises caused by sampling (quantization) in time and by the level of signal samples in the DAC. A relative value of the quantization noise depends on the amplitude of the generated signal (relative to the reference voltage of the DAC): the larger the amplitude, the more significant bits of the DAC are involved in the conversion process, and the less the relative value of the noise. In generators, where the amplitude of the output signal changes over a wide range (high dynamic range) by changing the digital samples of the signal, the quantization noise at low signal amplitudes can become unacceptably large. This situation occurs in power calibrators where the output current changes hundreds of times since the error of the verified electricity meter is normalized in a wide range of current flowing through it. A new algorithm for generating samples of a sinusoidal signal in measuring generators with digital control called adaptive quantization is proposed. Adaptive quantization can significantly improve one of the selected signal parameters (the so-called optimality criterion), for example, reduce the error in reproduction of the first harmonic, or reduce the value of higher harmonic components. In addition, the proposed algorithm reduces the dependence of the selected parameter on the sampling frequency and on the number of DAC bits used, which makes it possible to expand the dynamic range of the generator (in the current channel) without using additional amplifiers with programmable gain (PGA). Studies carried out using computer simulation have confirmed the efficiency of the adaptive quantization algorithm.

Analysis of Dynamic Interference Constraints in Cognitive Radio Cloud Networks

To analyze the security performance of a cloud network integrated with a cognitive radio. Cognitive Radio Cloud Network (CRCN) have a resilient potential for dynamic operation for energy saving. Integrating this Cognitive Radio Network (CRN) along with that of a cloud network produces great network exposure, spectrum usage and reduced power consumption. The problem arises for secure transmission and safe storage of huge amount of data in the cloud-based Cognitive Radio (CR) network. This paper, shows a study on preventing the CRCN from some advanced jamming techniques. An adversarial machine learning approach is introduced to launch jamming attacks on wireless communications and a defense strategy is presented. A cognitive transmitter uses a pre-trained classifier to predict the current channel status based on recent sensing results and decides whether to transmit or not, and then uses a Generative Adversarial Network (GAN), for generating synthetic data or false data, thus misleading the jammer to sense false data. The transmitter systematically selects when to take wrong actions and adapts the level of defense to mislead the jammer into making prediction errors and consequently increase its throughput. And to use the conventional cryptographic protocols for protecting the stored database in the cloud network from unauthorized users.

The Enhancement of Energy Storage Performances via Combining Relaxor Behaviors With the Crucial Point of Solubility Limit

(1-x)(0.96Na0.5Bi0.5TiO3-0.04BiMnO3)-xLaMnO3 ternary solid solution films were fabricated by Sol-gel methods. It takes advantage of the large polarization from 0.96NBT-0.04BMO limit solid solution at crucial point of solubility limit to enhance energy density. And LaMnO3 was introduced to improve the energy storage efficiency via the enhancement of relaxor behaviors. It is shown that the relaxor behaviors had been enhanced, and a large energy storage density of 87.9 J/cm3 and efficiency of 56.5 % were achieved for 0.85(NBT-BMO)-0.15LM films, with increase ratio of 4.9 % and 13.3 % respectively than 0.96NBT-0.04BMO solubility limit films. However, when LaMnO3 is beyond a certain limit, the breakdown strength is reduced due the formation of the current channel. Thus it suggests a alternative method that combining relaxor behaviors with solubility limit films, which provides a way to regulate the energy storage performances for film capacitors.

Breakdown Behavior of GaAs PCSS with a Backside-Light-Triggered Coplanar Electrode Structure

The competitive relationship between the surface flashover of the coplanar electrodes and the body current channel was investigated. Breakdown behavior of GaAs photo-conductive semiconductor switch (PCSS) with a backside-light-receiving coplanar electrode structure was studied in this paper. GaAs PCSS was triggered by the laser pulse with an extrinsic absorption wavelength of 1064 nm. Special insulating construction was designed for GaAs PCSS, while the surface of the electrodes was encapsulated with transparent insulating adhesive. Our first set of experiments was at a bias voltage of 8 kV, and the surface flashover breakdown of GaAs PCSS was observed with 10 Hz triggering laser pulse. In the second experiment, at a bias voltage of 6 kV, the body current channel breakdown appeared on the backside of the GaAs PCSS. Compared with these results, the existence of a competitive relationship between the surface flashover breakdown and the body current channel breakdown of the GaAs PCSS was confirmed. When the bias voltage is set within a certain range (just reaching avalanche mode), GaAs PCSS with a backside-light-receiving coplanar electrode structure will undergo the body current channel breakdown. This finding is also consistent with the simulation results.

Strategies for achieving high key rates in satellite-based QKD

Quantum key distribution (QKD) is a pioneering quantum technology on the brink of widespread deployment. Nevertheless, the distribution of secret keys beyond a few 100 km at practical rates remains a major challenge. One approach to circumvent lossy terrestrial transmission of entangled photon pairs is the deployment of optical satellite links. Optimizing these non-static quantum links to yield the highest possible key rate is essential for their successful operation. We therefore developed a high-brightness polarization-entangled photon pair source and a receiver module with a fast steering mirror capable of satellite tracking. We employed this state-of-the-art hardware to distribute photons over a terrestrial free-space link with a distance of 143 km, and extracted secure key rates up to 300 bits per second. Contrary to fiber-based links, the channel loss in satellite downlinks is time-varying and the link time is limited to a few minutes. We therefore propose a model-based optimization of link parameters based on current channel and receiver conditions. This model and our field test will prove helpful in the design and operation of future satellite missions and advance the distribution of secret keys at high rates on a global scale.