Non-sinusoidal Voltage Excitation Research Articles

Vibration and noise characteristics of high-frequency amorphous transformer under sinusoidal and non-sinusoidal voltage excitation

The vibration test of silicon steel, amorphous and nanocrystalline magnetic rings shows that the magnetostriction of amorphous materials is much larger than that of silicon steel and nanocrystalline. This paper focuses on the measurement and analysis of the vibration and noise of a 5kVA/4.5 kHz amorphous high-frequency transformer (HFT) under sinusoidal and non-sinusoidal excitation. Comparing and analyzing the measured data of vibration and noise, the results show that the vibration of HFT under the non-sinusoidal excitation is much larger than that of the sinusoidal excitation. The vibration excited by sinusoidal excitation basically concentrates on the double frequency of the excitation. Most of the vibration under non-sinusoidal excitation is also on the double frequency, but contains many harmonics. The influences are analyzed of duty cycle of rectangular excitation and the natural frequency of HFT on the vibration and noise.

Investigation of Core Loss Calculation Methods for Nanocrystalline Core in Medium Frequency Range

Nanocrystalline core is often adopted in high-power medium-frequency transformer, whose excitation voltage is usually a rectangular wave with an adjustable duty ratio. In this paper, several kinds of methods are proposed for core loss calculation under non-sinusoidal voltage excitation by modifying the original Steinmetz equation (OSE). Firstly, these correction methods are compared in theory, and their analytical equations under rectangular voltage with an adjustable duty ratio are deduced. Then, a hysteresis loop measurement system is established to measure the core loss density of a nanocrystalline core. Based on the measured results of the core loss density under sinusoidal voltage excitation, the coefficients of OSE for the core are fitted. Finally, core loss calculation results using the proposed correction methods under different amplitudes and duty ratios are analyzed and compared with the measured values. The results verify the correctness of the theoretical analysis, that waveform-coefficient Steinmetz equation is the most suitable method for loss calculation of nanocrystalline core in medium frequency range when the excitation voltage is a rectangular wave with an adjustable duty ratio.

1.0 THz GaN IMPATT Source: Effect of Parasitic Series Resistance

The degradation of high-frequency characteristics of a 1.0-THz double-drift region (DDR) impact avalanche transit time (IMPATT) diode based on wurtzite gallium nitride (Wz-GaN), due to the influence of parasitic series resistance, has been investigated. A two-dimensional (2-D) large-signal (L-S) simulation method based on a non-sinusoidal voltage excitation (NSVE) model has been used for this purpose. A comprehensive model of series resistance has been developed by considering the influence of skin effect, and the said model has been incorporated in the 2-D L-S simulation for studying the effect of RF power output and DC to RF conversion efficiency of the device. Results indicate 24.2–35.9% reduction in power output and efficiency due to the RF power dissipation in the positive series resistance. However, the device can still deliver 191.7–202.9 mW peak RF power to the load at 1.0 THz with 8.48–6.41% conversion efficiency. GaN IMPATT diodes are capable of generating higher RF power at around 1 THz than conventional diodes, but the effect of parasitic series resistance causes havoc reduction in power output and efficiency. The nature of the parasitic resistance is studied here in the level of device fabrication and optimization, which to our knowledge is not available at present.

Large signal and noise properties of heterojunction AlxGa1−xAs/GaAs DDR IMPATTs

Simulation studies are carried out on the large signal and noise properties of heterojunction (HT) AlxGa1−xAs/GaAs double drift region (DDR) IMPATT devices at V-band (60 GHz). The dependence of Al mole fraction on the aforementioned properties of the device has been investigated. A full simulation software package has been indigenously developed for this purpose. The large signal simulation is based on a non-sinusoidal voltage excitation model. Three mole fractions of Al and two complementary HT DDR structures for each mole fraction i.e., six DDR structures are considered in this study. The purpose is to discover the most suitable structure and corresponding mole fraction at which high power, high efficiency and low noise are obtained from the device. The noise spectral density and noise measure of all six HT DDR structures are obtained from a noise model and simulation method. Similar studies are carried out on homojunction (HM) DDR GaAs IMPATTs at 60 GHz to compare their RF properties with those of HT DDR devices. The results show that the HT DDR device based on N-AlxGa1−x As/p-GaAs with 30% mole fraction of Al is the best one so far as large signal power output, DC to RF conversion efficiency and noise level are concerned.

Multiple-band large-signal characterization of millimeter-wave double avalanche region transit time diode

A large-signal method based on non-sinusoidal voltage excitation model is used to study the DC and RF characteristics of Double Avalanche Region (DAR) Silicon Transit Time diode. A large-signal simulation program based on drift-diffusion model is developed for this study. The simulation results show the existence of several distinct negative conductance bands in the admittance characteristics separated by positive conductance. Thus the DAR device is capable of delivering RF power not only at the design frequency but also at several frequency bands higher than the design frequency band in the mm-wave regime. A comparative study with DDR Si device designed to deliver RF power at a particular mm-wave frequency band shows that DAR Si device is capable of delivering significantly higher RF power not only at the designed mm-wave frequency band, but also at higher frequency bands.

Large-signal characterizations of DDR IMPATT devices based on group III–V semiconductors at millimeter-wave and terahertz frequencies

Large-signal (L-S) characterizations of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on group III–V semiconductors such as wurtzite (Wz) GaN, GaAs and InP have been carried out at both millimeter-wave (mm-wave) and terahertz (THz) frequency bands. A L-S simulation technique based on a non-sinusoidal voltage excitation (NSVE) model developed by the authors has been used to obtain the high frequency properties of the above mentioned devices. The effect of band-to-band tunneling on the L-S properties of the device at different mm-wave and THz frequencies are also investigated. Similar studies are also carried out for DDR IMPATTs based on the most popular semiconductor material, i.e. Si, for the sake of comparison. A comparative study of the devices based on conventional semiconductor materials (i.e. GaAs, InP and Si) with those based on Wz-GaN shows significantly better performance capabilities of the latter at both mm-wave and THz frequencies.

A Four-step Iterative Design Optimization Technique for DLHL IMPATTs

ABSTRACTA proposed four-step iterative optimization technique has been used to design a double low-high-low (DLHL) impact avalanche transit time (IMPATT) diode based on Si for 60 GHz operation. Initially the position of the charge bumps in both n- and p-epitaxial layers followed by the widths of those and the ratio of high to low doping concentrations have been varied to obtain the maximum large-signal DC to radio frequency (RF) conversion efficiency from the device. Finally the bias current density is varied within a specified range to obtain the optimum value of it for which the DC to RF conversion efficiency of the device is maximum. The above-mentioned four optimization steps have been repeated until the method converges to provide a stable optimized DC to RF conversion efficiency. A large-signal simulation technique based on non-sinusoidal voltage excitation model developed by the authors is used for this purpose. The large-signal properties of the optimized DLHL Si IMPATT have been simulated and those are compared with the experimental results reported earlier. The said comparison shows that the optimized DLHL diode is capable of delivering significantly higher RF power output with greater DC to RF conversion efficiency at 60 GHz as compared to its un-optimized counterpart.

IMPATT devices based on group III–V compound semiconductors: prospects as potential terahertz radiators

The potentialities of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on group III–V semiconductor material Wurtzite-gallium nitride (Wz-GaN) as possible millimetre-wave (mm-wave) and terahertz (THz) sources have been explored in this paper. A large-signal (L-S) simulation technique based on a non-sinusoidal voltage excitation model (NVSE) developed by the authors has been used to study the high-frequency properties of DDR Wz-GaN IMPATTs at both mm-wave and THz frequencies. Similar studies have also been carried out for DDR IMPATTs based on some other conventional semiconductor materials such as GaAs (group III–V), InP (group III–V) and Si (group IV). Results show that DDR Wz-GaN IMPATTs excel all other devices under consideration as regards radio-frequency performance at both mm-wave and THz frequencies.

Potentiality of semiconducting diamond as the base material of millimeter-wave and terahertz IMPATT devices

An attempt is made in this paper to explore the potentiality of semiconducting type-IIb diamond as the base material of double-drift region (DDR) impact avalanche transit time (IMPATT) devices operating at both millimetre-wave (mm-wave) and terahertz (THz) frequencies. A rigorous large-signal (L-S) simulation based on the non-sinusoidal voltage excitation (NSVE) model developed earlier by the authors is used in this study. At first, a simulation study based on avalanche response time reveals that the upper cut-off frequency for DDR diamond IMPATTs is 1.5 THz, while the same for conventional DDR Si IMPATTs is much smaller, i.e. 0.5 THz. The L-S simulation results show that the DDR diamond IMPATT device delivers a peak RF power of 7.79 W with an 18.17% conversion efficiency at 94 GHz; while at 1.5 THz, the peak power output and conversion efficiency decrease to 6.19 mW and 8.17% respectively, taking 50% voltage modulation. A comparative study of DDR IMPATTs based on diamond and Si shows that the former excels over the later as regards high frequency and high power performance at both mm-wave and THz frequency bands. The effect of band to band tunneling on the L-S properties of DDR diamond and Si IMPATTs has also been studied at different mm-wave and THz frequencies.

Large-signal characterization of DDR silicon IMPATTs operating in millimeter-wave and terahertz regime

The authors have carried out the large-signal characterization of silicon-based double-drift region (DDR) impact avalanche transit time (IMPATT) devices designed to operate up to 0.5 THz using a large-signal simulation method developed by the authors based on non-sinusoidal voltage excitation. The effect of band-to-band tunneling as well as parasitic series resistance on the large-signal properties of DDR Si IMPATTs have also been studied at different mm-wave and THz frequencies. Large-signal simulation results show that DDR Si IMPATT is capable of delivering peak RF power of 633.69 mW with 7.95% conversion efficiency at 94 GHz for 50% voltage modulation, whereas peak RF power output and efficiency fall to 81.08 mW and 2.01% respectively at 0.5 THz for same voltage modulation. The simulation results are compared with the experimental results and are found to be in close agreement.

Influence of skin effect on the series resistance of millimeter-wave IMPATT devices

An attempt is made in this paper to study the influence of skin depth on the parasitic series resistance of millimeter-wave IMPATT devices based on Silicon. The method is based on the concept of depletion width modulation of the device under large-signal condition. A large-signal simulation model based on non-sinusoidal voltage excitation is used for this study. The electric field snap-shots of 35 GHz Single-Drift Region (SDR) and 94 GHz Double-Drift Region (DDR) IMPATT devices are first obtained from which the series resistances are estimated by incorporating the effect of skin depth in the modeling and simulation. The series resistances of these devices are also obtained by neglecting the effect of skin depth. The values of series resistances obtained from the simulation are compared with the corresponding experimentally reported values. It is observed that the series resistance estimated by including the skin effect is in closer agreement with the experimental values as compared to that without including the same. Thus the skin effect plays an important role for determining the series resistance of IMPATT devices at millimeter-wave frequency bands.

Large-signal characterization of DDR silicon IMPATTs operating up to 0.5 THz

Large-signal (L-S) characterization of double-drift region (DDR) impact avalanche transit time (IMPATT) devices based on silicon designed to operate at different millimeter-wave (mm-wave) and terahertz (THz) frequencies up to 0.5 THz is carried out in this paper using an L-S simulation method developed by the authors based on non-sinusoidal voltage excitation (NSVE) model. L-S simulation results show that the device is capable of delivering peak RF power of 657.64 mW with 8.25% conversion efficiency at 94 GHz for 50% voltage modulation; whereas RF power output and efficiency reduce to 89.61 mW and 2.22% respectively at 0.5 THz for same voltage modulation. Effect of parasitic series resistance on the L-S properties of DDR Si IMPATTs is also investigated, which shows that the decrease in RF power output and conversion efficiency of the device due to series resistance is more pronounced at higher frequencies especially at the THz regime. The NSVE L-S simulation results are compared with well established double-iterative field maximum (DEFM) small-signal (S-S) simulation results and finally both are compared with the experimental results. The comparative study shows that the proposed NSVE L-S simulation results are in closer agreement with experimental results as compared to those of DEFM S-S simulation.

Effect of junction temperature on the large-signal properties of a 94 GHz silicon based double-drift region impact avalanche transit time device

The authors have developed a large-signal simulation technique extending an in-house small-signal simulation code for analyzing a 94 GHz double-drift region impact avalanche transit time device based on silicon with a non-sinusoidal voltage excitation and studied the effect of junction temperature between 300 and 550 K on the large-signal characteristics of the device for both continuous wave (CW) and pulsed modes of operation. Results show that the large-signal RF power output of the device in both CW and pulsed modes increases with the increase of voltage modulation factor up to 60%, but decreases sharply with further increase of voltage modulation factor for a particular junction temperature; while the same parameter increases with the increase of junction temperature for a particular voltage modulation factor. Heat sinks made of copper and type-IIA diamond are designed to carry out the steady-state and transient thermal analysis of the device operating in CW and pulsed modes respectively. Authors have adopted Olson's method to carry out the transient analysis of the device, which clearly establishes the superiority of type-IIA diamond over copper as the heat sink material of the device from the standpoint of the undesirable effect of frequency chirping due to thermal transients in the pulsed mode.

A proposed simulation technique to study the series resistance and related millimeter-wave properties of Ka-band Si IMPATTs from the electric field snapshots

A large-signal model and a simulation technique based on non-sinusoidal voltage excitation are used to obtain the electric field snapshots from which the series resistance and related high-frequency properties of a 35 GHz Silicon Single-Drift Region (SDR) Impact Avalanche Transit Time (IMPATT) device have been estimated for different bias current densities. A novel method is proposed in this paper to determine the parasitic series resistance of a millimeter-wave IMPATT device from large-signal electric field snapshots at different phase angles of a full cycle of steady-state oscillation. The method is based on the depletion width modulation of the device under a large-signal condition. The series resistance of the device is also obtained from the large-signal admittance characteristics at threshold frequency. The values of series resistance of a 35 GHz SDR IMPATT diode obtained from the proposed method and the large-signal admittance method are compared with experimentally reported values. The results show that the proposed method provides better and closer agreement with the experimental value.

Dynamic magnetic properties of the Fe-based alloys under non-sinusoidal excitation

Dynamic magnetic properties of a new FeCoNbBP alloy were measured under four types of voltage excitation: sinusoidal, triangular, square and ramp. Samples were prepared in a form of toroidal cores wound from melt-spun amorphous ribbons and subjected to suitable thermo-magnetic treatment in a transverse magnetic field. The measurements were carried out within a frequency range from 1 to 50 kHz using a computerized hysteresis loop tracer fitted with the function generator enabling non-sinusoidal voltage excitation. It was found that the core losses for this material clearly depend on excitation conditions and over the frequency range studied they were generally higher at triangular waveform and lower at square waveform compared to sinusoidal excitation. At the square wave voltage excitation, the differences were reaching 19%.

A simplified method for estimation of iron loss in wound toroidal cores energised by pulse width modulated voltage sources

Recently the strip wound toroidal cores have increasingly been used in switching mode and uninterruptible power supplies for a wide range of industrial applications. Therefore, the prediction of iron loss increase in such magnetic cores energised by non-sinusoidal voltage excitation is important step in the design of electromagnetic devices. In this investigation, a loss increase was estimated by determination of unknown constants in a previously developed loss separation model using genetic algorithms. Also the skin effect of flux density was taken into account for estimation of power loss under pulse width modulated voltage sources. The results obtained are in good agreement with the measured results in wound toroids at various flux densities.

Flux penetration and losses in steel plate with nonsinusoidal magnetisation

The cyclic magnetisation of steel plate with either nonsinusoidal magnetising force or nonsinusoidal voltage excitation is examined. The influence of the phase and the magnitude of the harmonic component of excitation is determined, together with profiles of flux density, voltage and magnetising force, at different depths and for a wide range of plate thicknesses and frequencies. A digital simulation technique, previously described, is used to compute theoretical values which include both hysteresis and eddy-current effects in the ferromagnetic material. Measured values of loss, flux/magnetising current loops and voltage waveshapes show good agreement with predicted values. A companion paper examines the cyclic magnetisation of non-grain-oriented low-loss steel laminations with nonsinusoidal excitation and computes theoretical values of loss, flux density and magnetising current waveshape.

Digital Simulation of PWM Induction Motor Drives for Transient and Steady-State Performance

In this paper, the influence of nonsinusoidal voltage excitation applied to a squirrel cage induction motor is investigated using direct three-phase machine simulation method. Computer packages are developed to generate various types of inverter modulation techniques, namely the sine, step, and current impressed schemes. These packages together with a three-dimensional plotting subroutine are used to investigate the characteristics of an inverter-fed induction motor system. The effects of switching frequency ratio, overmodulation, and start-on machine waveform characteristics are investigated. Harmonic distortion comparisons between sine and step modulation schemes are presented. A vector controller-driven current-impressed scheme are simulated. The effect of varying hysteresis band in a current-impressed scheme is discussed.