Diode Voltage Research Articles

A V-Band Coaxial Relativistic Transit-Time Oscillator Operating in TM02Mode With Shallow Corrugated Output Structure

A V-band coaxial relativistic transit-time oscillator (TTO) with shallow corrugated output structure operating in TM₀₂ mode is presented. Compared with the deep corrugated output structure, the power handling capacity of the device with shallow corrugated output structure is higher. In particle-in-cell (PIC) simulation, a 403 MW output microwave at 59.10 GHz is obtained with beam voltage of 400 kV, beam current of 5.0 kA under the guiding magnetic field of 1.0 T. The maximum surface electric field in the device is 1.8 MV/cm. Compared with the maximum surface electric field in deep corrugated devices, the maximum surface electric field decreases by 38%. In experiment, a microwave output with power of 258 MW, frequency of 59.04 GHz and pulse duration of 16.0 ns is obtained with diode voltage of 410 kV and beam current of 5.1 kA. The microwave output power and pulse width are significantly improved compared with the previous deep corrugated structure.

Design and implementation of a fault detection method for a PV‐fed DC‐microgrid with power control mechanism

This paper presents practical implementation of a fault detection, localisation, and categorisation (FDLC) method in PV-fed DC-microgrid (DCMG). The DCMG is implemented by utilising a group of two DC nanogrids (DCNG) that have power control mechanism (PCM). The FDLC uses a voltage calculating circuit comprising a single voltage sensor and diode network. Moreover, the architecture is based on six statements extracted from the investigation of line to line (L–L) and line to ground (L–G) faults at a DCNG of the cluster. The PCM in the proposed system utilises a power triggering circuit for effective power flow among the different units of the DCNG considering the load demands and the resource availability. Experimentation is carried out by creating L–L/L–G faults at different points in the DCMG. Detection, localisation, and classification of faults is performed by utilising the sensor's voltage and power of the individual DCNG. FDLC offers less computational burden, perform fast detection of fault, and is capable of distinguishing between the L–L/L–G faults and uniform irradiance and partial shading conditions in the PV-array. The proposed FDLC technique and its six statements are verified through experimental results.

Broadband and Programmable Amplitude-Phase-Joint-Coding Information Metasurface.

Information metasurfaces have attracted much attention in recent years due to the capability to link the physical world and information science. However, most of the current information metasurfaces are either phase-only coding or amplitude-only coding, limiting their functions and applications. Here, a broadband and programmable amplitude-phase-joint-coding (APJC) information metasurface is proposed and experimentally demonstrated, from which the phase and amplitude of reflected electromagnetic waves can be independently controlled by adjusting the bias voltage of PIN diode integrated in the meta-atom. In particular, the reflection amplitude can be continuously controlled from 0.1 to 0.9, and the reflection phase can be switched between two states with about 180° phase difference. Thus, the proposed metasurface is capable of realizing independent 1-bit or multibit amplitude coding and 1-bit phase coding, and both of them can be reprogrammed in real time in broad band from 8 to 13 GHz. The abilities of the programmable APJC information metasurface in manipulating the electromagnetic waves are demonstrated by both numerical simulations and experiments, including to suppress the sidelobes of scattering beam, generate the diffractive waves with arbitrary magnitudes, and so on. These results show unique advantages of APJC information metasurface in real-time independent controls of energy allocation and wavefront tailoring of the electromagnetic waves in a wide frequency band.

Design of Savonius model wind turbine for power catchment

In this study, the fossil fuel usage by-product is carbon dioxide, which is known as the primary cause in global warming. Alternatively, wind energy is a clean alternative energy source compared the fuel consumption can cause smoke pollution. The goal of the work is to develop a pollution controller device model Savonius wind turbine to represent the characterized actual speed wind turbine concepts into convert kinetic energy into electric energy from campus and monitoring all output data display on the cloud. The wind speed operation is enabled through the use of ESP8266 as internet of things (IoT) platform and the alternating current (AC) direct current (DC) harvesting circuit into improve stability of the wind energy performance. Secondly, a magnet coil synchronous generator is used, which is a grid coupled through a diode rectifier and voltage source converter. The parameters that have been measured using wireless fidelity (Wi-Fi) module ESP8266 are considering wind speed, current, voltage and power. The wind speed with 7.8 MPH can produce a maximum output voltage and output current of 1.104 V and 4.321 μA, respectively. Blynk applications functional as role present performance monitoring kit wind turbine analysis with more precise and efficient in anywhere and anytime.

Thermo-electro-environmental analysis of a photovoltaic solar panel using machine learning and real-time data for smart and sustainable energy generation

The impact of meteorological parameters, including ambient temperature, wind velocity, ambient relative humidity, and solar radiation on photocurrent and thermal voltage of diode, as two main thermo-electrical parameters of a solar panel, is found. For this purpose, the experimental data obtained during a year, in addition to the post-processed images captured by an infrared thermal imaging camera, are used, and models for performance prediction by the artificial neural network are developed and validated. In addition, the impact of photocurrent and thermal voltage of diode on CO2 saving of the system is found. According to the results, for the investigated 320W polycrystalline panel, with 200.0% increase in the range of 500–1500 W m−2, solar radiation has the strongest impact on photocurrent. Moreover, the most effective meteorological parameter on the thermal voltage of diode is ambient temperature. Changing ambient temperature from 27 to 47 °C is accompanied by 9.36% growth in that parameter. The conducted sensitivity analysis also reveals that between photocurrent and thermal voltage of diode, the former is a more effective parameter on CO2 emission reduction of the system. When photocurrent values are 20% lower and 20% higher than the base case, the amounts of CO2 saving are 18.0% smaller and 14.6% greater, respectively. It means 32.6% variation within the range.

Theoretical calculation and particle-in-cell simulation of a multi-mode relativistic backward wave oscillator operating at low magnetic field

Increasing the dimensions of high power microwave devices is an efficient method to improve the power capacity. However, an overmoded structure usually results in mode competition and a low beam-wave conversion efficiency. In this paper, a multi-mode operation mechanism is used to avoid mode competition and increase the efficiency. The calculation results of nonlinear theory of beam-multimode interaction show that the optimized conversion efficiency is up to 48% when TM01 mode, TM02 mode, and TM03 mode are all considered. As only the TM01 mode, TM02 mode, or TM03 mode is taken into account independently, the corresponding efficiency is 38%, 22%, or 20%. Based on this, a multi-mode relativistic backward wave oscillator is proposed with the ratio of the mean diameter of the slow wave structure (SWS) to the wavelength of the output microwave to be 3.5. The non-uniform SWS is used to increase the beam-wave conversion efficiency, and a combined reflector is adopted to reflect partial of the mixed microwave modes and make the device compact. The particle-in-cell simulations show that as the diode voltage is 1.1 MV, the beam current is 22.8 kA, and the external magnetic field is 0.76 T, the conversion efficiency is 45%, and the output microwave of 11.3 GW is the mixed modes of TM01 mode, TM02 mode, and TM03 modes with the corresponding power ratio of 74%, 7%, and 19%, respectively.

Efficiency improvement by a beam filtering ring in a relativistic backward wave oscillator at low magnetic field

This paper presents a design method of the relativistic backward wave oscillator at low magnetic field, which can improve the efficiency by 29% in the particle in cell simulation. The core of this method is to introduce a beam filtering ring. The beam filtering ring takes the characteristic of the radial position change as the electron oscillates. The structure manipulates the axial current, so that a large proportion of the electrons expected to be in the accelerated phase in the slow-wave structure is absorbed by the structure. It greatly enhances the bunching of the beam in the RF field and improves the beam-wave conversion efficiency significantly. The particle in cell simulation results reveal that at a permanent magnet with a magnetic induction intensity of 0.68 T, the output microwave power of the relativistic backward wave oscillator with a beam filtering ring is 5.9 GW, and the conversion efficiency can be up to 54% when the diode voltage is 890 kV and the beam current is 12.2 kA.

Crosstalk Suppression Method for GaN-Based Bridge Configuration Using Negative Voltage Self-Recovery Gate Drive

In order to suppress the crosstalk in gallium nitride (GaN) based bridge configuration, a novel negative voltage self-recovery gate drive (NVSRGD) is proposed in this article. The resistor–capacitor–diode voltage divider is applied to establish the negative gate–source voltage and suppress the impact of positive crosstalk. The antiparallel diode is added to constitute a low-impedance Miller current path from the driver integrated circuit (IC) to the GaN device. It works together with the self-recovery gate–source voltage to suppress the negative crosstalk, which not only prevents the GaN device from the negative overstresses but also reduces the reverse conduction loss during the dead time. The NVSRGD is composed of a few passive components, which are suitable for integrating into the driver IC. The capacitors and resistors of the NVSRGD are designed to determine the negative voltage level and the restore time. Additive separate negative voltage power supplies or active devices are not needed. The double-pulse test based on GS66508B verifies the effectiveness of the proposed method for suppressing the positive and negative crosstalk of GaN devices.

Radial oscillation of intense relativistic electron beam in low-magnetic-field foil-less diode

The radial oscillation of an intense relativistic electron beam possesses two main features of the spatial period and the radial oscillation amplitude in a low-magnetic-field foil-less diode, and the large radial oscillation extremely limits the beam–wave conversion efficiency and stability of a high-power microwave device. Thus, the formation mechanism of the radial oscillation is analyzed in detail. The results show that the radial oscillation of an electron beam consists of a great number of electrons with different Larmor radii and guiding centers, and the large radial oscillation is mainly caused by the strong radial electric field and the directional difference between the electric field and the magnetic field in the anode–cathode gap. A low diode voltage or a proper large anode radius is beneficial to improve the beam quality. Considering that cathode plasmas have a dominant effect on the spatial distribution of electrons, the explosive emission model was improved with cathode plasmas, and the consistency between simulation and experimental results becomes better.

Study of switchable Luneburg lens reflector based on active frequency selective surface

In this article, a transmission and reflection states switchable Luneburg lens (LL) reflector based on active frequency selective surface (AFSS), namely LL-AFSS reflector, is proposed. The reflector is composed of a miniaturized AFSS reflector, which can change the working state, and a LL composed of six layers and five media from inside to outside. By changing the bias voltage of the PIN diode loaded on the AFSS reflector, the transmission and reflection working states of the LL reflector can be freely switched in the frequency range of 3.5–5 GHz. When the PIN diodes are in ON state, the incident electromagnetic wave will not be reflected through the LL reflector. When the PIN diodes are in OFF state, the radar cross section (RCS) generated by the LL reflector to the incident electromagnetic wave reaches about 15 dB within the angle range of −30 ≤ φ ≤ 30°. The electromagnetic numerical simulation and experimental sample verification of LL-AFSS reflector are carried out. The results show that the proposed design method is feasible and the RCS changes of transmission and reflection characteristics of LL reflector are obvious.

Conversion of Cherenkov Radiation to Transition Radiation by Electron Bunch Post-Acceleration for Extremely Efficient Beam–Wave Interaction

A super klystron-like relativistic backward wave oscillator (RBWO) is presented. In the device, the distributed Cherenkov radiation generated in the slow wave structure (SWS) is absorbed by the electron bunch in the last corrugation and re-accelerated, creating high-energy electrons that overcome the space-charge repulsion force to further compress the bunch length and maximize the fundamental harmonic current, contributing to the extremely efficient microwave generation in the extraction cavity through concentrated transition radiation. A novel elliptical extraction cavity is used to improve the power capacity. A soft magnet is inserted to precisely control the beam path, which provides a higher beam kinetic energy to be extracted and a stronger electric field that interacts with the tighter bunch. In the experiment, as the diode voltage was 585 kV and diode current was 7.5 kA, a microwave pulse with a power of 2.9 ± 0.3 GW measured in the radiation field, a frequency of 8.23 GHz, and a pulse duration of 22 ns was obtained. The corresponding efficiency is up to 66 ± 8%, which is an experimental record for GW-class relativistic vacuum electronic devices.

Multiport Relativistic Magnetron for Phased Array Application

A preliminary investigation on S-band multiport relativistic magnetron (RM) is carried out, which is targeted at the application of high-power microwave (HPM) phased array system. For such system, the phase synchronization and stabilization of sources are crucial. In the proposed multiport RM, the HPMs in four independent output ports are extracted from the same resonant system, thus having the same amplitude and phase naturally. Moreover, the output mode of such multiport RM is fundamental mode, which can achieve Gaussian radiation in the far field directly. Since mode convertors and phase-locked units are no longer necessary, it is beneficial to the miniaturization of HPM phased array system. To further control the phase of output signals, a wide side dimension adjustable phase shifter used for this multiport RM is designed, which could achieve 180° phase shift with a power handling capacity of 568 MW. Particle-in-cell (PIC) simulation of such multiport RM combined with phase shifters applied a diode voltage of 450 kV is carried out. When all output signals are adjusted to be in- phase, an average output power of 265 MW in each port can be obtained, corresponding to a power conversion efficiency up to 65%, and the relative phase differences are controlled within ±2.4%.

A Quintupler Boost High Conversion Gain Soft-Switched Converter for DC Microgrid

This study proposes a high conversion gain soft-switching quintupler boost non-isolated converter for DC microgrid. By inclusion of quintupler rectifier and coupled inductor with reduced duty cycle, high voltage gain is obtained. The leakage energy of coupled inductor is recycled through an auxiliary switch and the output capacitor improves further boost. Due to the active clamp and this recycled leakage energy, huge inductive voltage spikes across MOSFETs are alleviated and also, stress is reduced. Hence, low voltage rating (low <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{ds(ON)}$ </tex-math></inline-formula> ) switches can be utilized and minimize conduction losses. In addition, this clamp enables zero-voltage switching (ZVS) for both the MOSFETs, even at light loads. Quintupler multiplier rectifier reduces the voltage stress across diodes. This, in turn, reduces reverse recovery losses for multiplier diodes. Further, the coupled inductor leakage inductance in series with diodes provides for the snubbing effect to alleviate voltage spikes across quintupler diodes. Thus, the overall diode voltage rating reduces. This improves power density and improves the overall efficiency of the converter. Finally, a 400W prototype operates at 100kHz is developed to validate the converter performance. The measured peak efficiency is 96.43%.

Picosecond-range switching of high-voltage Si diode due to the delayed impact-ionization breakdown: Experiments vs simulations

The effect of delayed impact ionization breakdown initiated in a high-voltage Si or GaAs p+nn+ diode by a steep voltage ramp leads to 100 ps avalanche transient from the blocking to conducting state. Here, measurements of the voltage and current dependences in the Si diode exhibiting 100-ps kilovolt switching are presented together with simulations with focus on comparison. Device voltage and current are measured simultaneously and independently in a high-quality matched coaxial circuit. In simulations, we account for wave propagation and reflection processes in the coaxial driving/measuring circuit and for the inhomogeneity of the avalanche switching over the device cross section. This makes quantitative comparison with measurements possible. An agreement in switching time and transient characteristics can be achieved only under the assumption that a smaller part of the cross section is avalanching. The 100-ps switching time is formed not during the passage of superfast ionizing front in the “active” part of the device, as it is widely believed, but by the discharge time of the “passive part” over the conducting “active” part. The inner circuital current that flows within the device along the closed loop plays a dominant role in this process. Sources of initial carriers, the temperature dependence of the effect, and the limits of drift-diffusion transport model in describing the phenomenon of delayed breakdown are discussed.

Modular Integration of a Compact Ku-Band Relativistic Triaxial Klystron Amplifier Packaged With Permanent Magnets for High-Power Microwave Generation

To achieve modular integration of relativistic triaxial klystron amplifier (TKA) devices and reduce the energy consumption of the whole high-power microwave (HPM) system, a compact Ku-band TKA packaged with permanent magnets is proposed and investigated in this paper. By optimizing the electromagnetic structure and utilizing TEM mode energy coupling, the length of the uniform magnetic field area required for the Ku-band TKA is reduced from 32 cm to 19.6 cm, with a reduction rate of 39%. By utilizing the NdFeB-N50M mainly magnetized in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}$ </tex-math></inline-formula> direction, a permanent magnet guiding system weighing 90 kg is proposed. Besides, the length of the uniform zone is 20 cm with a longitudinal magnetic field of 0.5 T. Verified by the PIC simulation software CHPIC, an HPM with power of 430 MW and frequency of 14.25 GHz is generated when the diode voltage, current, and the injected microwave power are 340 kV, 4.2 kA, and 15 kW, respectively. The phase jitter of the output microwave is controlled within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\pm } 5{^\circ }$ </tex-math></inline-formula> , which is beneficial to the coherent power combination of modular integrated TKA devices

Влияние напряжения заряда емкостного накопителя на выходные параметры ускорителя на основе импульсного трансформатора

In the modern world an electron accelerator is a tool that provides the generation of an electron beam with specified parameters. A necessary description of any tool is its functioning parameters and output characteristics. In this work, the output characteristics of a pulsed electron accelerator (diode voltage and current pulse amplitudes, current and energy of the beam extracted into the atmosphere, and the spectrum of particle kinetic energies) are studied depending on the controlled charge voltage of the primary capacitive energy storage. An analysis was made of the energy transfer efficiency in the circuits of the accelerating voltage pulse generator according to the scheme high-voltage capacitive storage - commutator - pulse transformer - vacuum electron diode.

Single Switch Module Type DC-DC Converter With Reduction in Voltage Stress

This paper proposes a new generalized switched-inductor-capacitor module for a non-isolated dc-dc converter with low voltage dc source applications. Further, the proposed module can be extended to an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> number of modules to achieve high voltage gain. The derived structure has low voltage stress on power components. This structure benefits the designer by allowing him/her to choose a low <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r_DS</i> (ON) switch due to the low voltage stress across the semiconductor devices, resulting in high efficiency and low cost. In most dc/dc converters, the voltage stress on the output diode will equal the output (high) voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_o</i> ). But in the case of the proposed topology, the diode voltage will be the difference between <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_o</i> and the input voltage ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_g</i> ), which eases the reverse recovery problem. The key metrics of the derived topology, such as component count, voltage stresses, and gain factor, are analyzed to compare with similar existing topologies. The scaled down prototype setup is developed for 200 W with an efficiency of 93%. Finally, various experimental results are discussed for the different duty cycles.

Implications of open circuit voltage of light-emitting diodes installed for plant cultivation

This study investigated a light sensor function of light-emitting diodes (LEDs), the use of which is expanding in plant cultivations. Unimodal spectral LEDs of four types with respective emission peak wavelengths of 464, 501, 634, and 849 nm, and a white LED with a bimodal spectrum with 455-nm primary and 574-nm secondary peaks were used for this study. Open circuit voltage (VOC) of up to 1-2 V was induced in the LEDs when they were irradiated with sunlight. The VOC value of the 634 nm LED saturated with a low photon flux density can be used for binary discrimination between daylight and night. Each LED had a VOC inducible threshold wavelength of incident light. By virtue of the wavelength threshold feature, existence of a plant leaf between a light source and the LEDs is detectable by comparing the VOC values of blue-green range LEDs (464 nm, 501 nm) and near-infrared (NIR) LEDs (849 nm). Under leaf shadow, the NIR LED VOC exceeded those of the blue-green range LEDs. Under natural incident sunlight, the VOCs of the blue-green range LEDs were greater than that of the NIR LED. Another function of LEDs in agricultural use has been demonstrated.

GaN Active Rectifier Diode

Active or synchronous rectification is used today to further increase the efficiency of mass-market power supplies by eliminating the turn-on voltage of rectifier diodes, thus reducing conduction losses. However, the active rectification is usually realized by two devices: a power MOSFET and a control circuit to imitate an ideal diode behavior. This paper presents a GaN active rectifier diode consisting of a 600 V power transistor, a control circuit with gate driver, and a supply generation, all monolithically realized in a GaN power integrated circuit (IC). This enables a true two-terminal device that can directly replace a rectifier diode. In order to evaluate the proposed conduction loss reduction by replacing a rectifier diode by an active diode, the theoretical limits at circuit level and at semiconductor level are analyzed. The GaN active rectifier diode is demonstrated in a half-wave rectification (110/230 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">AC</sub> , 50/60 Hz) up to a forward current of 6 A. A single-device realization of low-loss GaN active rectifier diodes is more cost-efficient than a multi-chip or package-integrated solution.

Ultra-thin ultra-wideband tunable radar absorber based on hybrid incorporation of active devices

Structural radar absorber has important application in stealth field for its ability to effectively absorb incoming radar wave and to bear the load at the same time. Metasurface absorbers can achieve nearly-perfect absorption of radar wave, and have characteristics of light weight and thin structure, but their bandwidth are usually narrow. To solve this problem, a new method of broadening the bandwidth of metasurface absorber is proposed in this work. With varactor and PIN diode integrated in a hybrid manner, the continuous tunning and discrete switching are combined together to broaden the effective absorption bandwidth of the absorber. Using this method, an ultra-wideband tunable metasurface absorber is designed and the absorbing mechanism is analyzed in depth. By changing the bias voltages of PIN diodes and varactors, the absorbing frequency can be continuously tuned within a wide band from 4.57 GHz to 8.51 GHz. Measured results verify the low radar cross section characteristics of the absorber and the effectiveness of the design method. The proposed method is simple and feasible, and can be extended to other broadband structure design.