Wave Switching Research Articles

Oversized interference microwave switches with distributed power of a switching wave

These are the results of research of the oversized (multimode) interference microwave switch at operating mode TE01. The switch was produced from two H-plane T-junctions being connected to each other through straight arms (series connection). Two types of oversized tees were considered. One was based on an oversized waveguide with 25×58 mm2 in cross-section and another was a package of regular H-tees operating at TE10 mode with a mutual switched arm. The operating frequency was 9.15 GHz. The conducted simulation showed the conditions of the “proper” TE01 mode at “open” and “close” states of the switch. Moreover, the relations between the arm’ lengths and field intensity distribution were compared with the similar relations of a regular cascade microwave plasma switch. In additional, experiments were carried out at low power level.

High Speed Terahertz Modulator on the Chip Based on Tunable Terahertz Slot Waveguide

This paper presents an on-chip device that can perform gigahertz-rate amplitude modulation and switching of broadband terahertz electromagnetic waves. The operation of the device is based on the interaction of confined THz waves in a novel slot waveguide with an electronically tunable two dimensional electron gas (2DEG) that controls the loss of the THz wave propagating through this waveguide. A prototype device is fabricated which shows THz intensity modulation of 96% at 0.25 THz carrier frequency with low insertion loss and device length as small as 100 microns. The demonstrated modulation cutoff frequency exceeds 14 GHz indicating potential for the high-speed modulation of terahertz waves. The entire device operates at room temperature with low drive voltage (<2 V) and zero DC power consumption. The device architecture has potential for realization of the next generation of on-chip modulators and switches at THz frequencies.

Urban Electromagnetic Spider Web

Here design of electromagnetic spider webs imitating the actual spider web and trigram cropland structure, using the principle of bionics will combine Telluric Current, electricity, Atmospheric electronic, E-compass, 4G-GSM wave Switch, low and high frequency wireless transmitting and receiving devices. WIFI devices Switch. In theory, the electromagnetic spider webs induction method in Maxwell equation is adopted, and simple instruments and equipment are made by combining some software, such as wavelet transform, Mat-Lab simulation and configuration software. At ordinary times, all kinds of abnormal electromagnetic signals are detected at any time before the earthquake. In war, device can be used to detect all kinds of flying objects, such as stealth aircraft and cruise missiles, through the spider webs. Low equipment costs, reliable operation, we have forty years of wisdom crystallization [1].

The formation process of a bistable state in nanofluids

We study the theory of the dynamics of the concentration of nanoparticles in a liquid-phase environment under the influence of a light field. An exact solution for the nonlinear diffusion equation was found in the form of switching waves. It is shown that under the conditions of a stationary and nonlinear temperature coefficient of thermal conductivity of the medium, nanofluids become bistable.

All-optical THz wave switching based on CH3NH3PbI3 perovskites.

Hybrid structures of silicon with organic–inorganic perovskites are proposed for optically controllable switching of terahertz (THz) waves over a broad spectral range from 0.2 to 2THz. A 532-nm external laser was utilized to generate photoexcited free carriers at the devices and consequentially to control the terahertz amplitude modulation, obtaining a depth of up to 68% at a laser irradiance of 1.5 W/cm2. In addition, we compared the performances from three types of perovskite devices fabricated via different solution processing methods and suggested a stable and highly efficient THz switch based on a one-step processing. By this we demonstrated the possibility of perovskites as THz wave switching devices in addition to photovoltaics.

Ultra-compact terahertz switch with graphene ring resonators**Project supported by the Public Technology Research Project of Zhejiang Province, China (Grant No. 2015C31116).

We propose and numerically demonstrate a compact terahertz wave switch which is composed of two graphene waveguides and three graphene ring resonators. Changing the bias voltage of the Fermi level in the center graphene ring, the resonant mode can be tuned when the plasmon waves in the waveguides and rings are coupled. We theoretically explain their mechanisms as being due to bias voltage change induced carrier density of graphene modification and the coupling coefficients of graphene plasmon effect after carrier density change, respectively. The mechanism of such a terahertz wave switch is further theoretically analyzed and numerically investigated with the aid of the finite element method. With an appropriate design, the proposed device offers the opportunity to ‘tune’ the terahertz wave ON–OFF with an ultra-fast, high extinction ratio and compact size. This structure has the potential applications in terahertz wave integrated circuits.

Investigation of fatigue behavior of Pb(Zr0.45Ti0.55)O3 thin films under asymmetric polarization switching

The fatigue of lead zirconate titanate (PZT) thin films was measured under repetitive switching using asymmetric square waves. The remnant polarization and coercive voltage were found to present regular changes in the initial 10 s, independent of the asymmetry or frequency of switching waves. We attributed the change to the relaxation of stress in the film and identified a coercive voltage V0 of 0.6 V for the stress-free film. By comparing the coercive voltage and V0, we found that a built-in electric field was induced by asymmetric switching, where the direction and magnitude were dependent on the degree of waveform asymmetry. Furthermore, the fatigue speed was suggested to be closely related to the generation rate of oxygen vacancies. It was confirmed by our result that a faster decay of remnant polarization can be obtained by applying square waves with a higher degree of asymmetry or symmetry of square waves with a lower frequency.

Switching terahertz waves with graphene-integrated split-ring resonator

In this paper, we design and numerically demonstrate an electrically controllable terahertz wave switch consisting of a graphene nanoribbon waveguide and three graphene split-ring resonators. By applying a bias voltage on the graphene split-ring resonators, this switch can dynamically control the amplitude of the transmitted terahertz wave at 9THz. Moreover, the calculated results show that the extinction ratio of this switch can be tuned from 30dB to 0.82dB when the chemical potential varies from 0.1eV to 0.2eV. The total size of the present device is only 3μm×2μm. This work may pave the ways for the further development of compact and integrated high-performance graphene-based terahertz wave devices.

Origin and stability of dark pulse Kerr combs in normal dispersion resonators.

We analyze dark pulse Kerr frequency combs in optical resonators with normal group-velocity dispersion using the Lugiato-Lefever model. We show that in the time domain the combs correspond to interlocked switching waves between the upper and lower homogeneous states, and explain how this fact accounts for many of their experimentally observed properties. Modulational instability does not play any role in their existence. We provide a detailed map indicating for which parameters stable dark pulse Kerr combs can be found, and how they are destabilized for increasing values of frequency detuning.

An Altered PWM Scheme for Single-Mode Seamless Control of AC Traction Motors for Electric Drive Vehicles

In an electric drive vehicle (EDV), the available voltage on a dc-link is limited, and so the inverter output voltage and, consequently, the line motor maximum speed are limited. The fundamental voltage of the inverter output is increased approximately 27% using a square wave (SW) switching pattern instead of a sine wave switching pattern. However, this pattern can only be used at high speeds, and at lower speeds a pulsewidth modulation (PWM) pattern should be used. In order to achieve proper control, the switching pattern should be changed seamlessly. In the present paper, a new PWM scheme for single-mode seamless control of Vernier motors is proposed. In the proposed scheme, the reference voltage is modified to change the switching pattern continuously so that the voltage changes smoothly from a high-frequency pattern to an SW and voltage discontinuity does not occur. Experimental results reveal that the inverter-switching pattern changes smoothly from a sinusoidal PWM pattern to an SW pattern, and so seamless control from the constant-torque region to the constant-power region, and vice versa, is achieved. Since the proposed scheme is a single-mode control, it is much simpler than current technologies, which are based on multimode controllers. Also the proposed method has a lower total harmonic disturbance (THD) as well as a lower harmonic distortion factor (HDF) compared to some existing methods.

Ultrafast optical switching of terahertz wave transmission through semiconductor/metallic subwavelength slot antenna hybrid structure

We demonstrate ultrafast optical switching of electromagnetic waves through a metallic slot antenna in the terahertz frequency regime. The screening of the terahertz field due to the optical excitation of carriers in GaAs/AlGaAs multiple quantum wells is further enhanced due to the strong field confinement near the antenna, which results in the complete suppression of the far-field transmission of terahertz waves. The ultrafast rising time of the carrier population enables picosecond switching of terahertz transmission. A simulation based on a modified Rayleigh diffraction theory combined with the Drude model confirms that the fast decay of electromagnetic field within GaAs is responsible for the ultrafast optical switching.

Analysis of microwave interference switches with distributed power of switched wave and plasma gas-discharge switching

This paper reports on development of effective cascade type microwave interference switches using waveguide H-tees providing total transition attenuation value of about -50dB at the non-transmitting state, the power losses of -2-3dB at the transmitting state, and the working power compared to the one of a regular waveguide. These switches have different types of connections of two or three H-tees. Different designs provide different distributions of switched wave power between tees and provide different power levels of the switched wave. Characteristics of the switches made of tees matched from their side arms and of unmatched ones were calculated using the scattering matrix method. It was shown the matched tees used in the design allow decreasing by several times the power level of the switched wave and that increases the operating power and stability of the switching process. While some definite combination of unmatched tees allow increasing the power level of the switched wave and may provide effective switching of the transmitted wave at decreased power level. It was shown experimentally the cascade switches could be used as effective energy extraction device in an active resonant microwave compressor also.

Selección y Espaciamiento de Apartarrayos en Líneas de Distribución de 23 kV de la Zona Centro

En este artículo se analiza una red de distribución urbana de 23 kV típica de la zona central de México, para determinar la distancia máxima de separación entre apartarrayos de línea que permita reducir las salidas de los circuitos de distribución por descargas atmosféricas directas e indirectas. Con base en las características eléctricas, ambientales, ceráunicas y geográficas de la zona, niveles de cortocircuito y los sobrevoltajes provocados por maniobras rutinarias, se selecciona el apartarrayos siempre con el principal objetivo de determinar su espaciamiento adecuado sobre la línea para que funcione eficientemente. Esta investigación se lleva a cabo con la ayuda del software Alternative Transients Program (ATP) con el que se realiza desde el cálculo de los parámetros de la línea utilizando el modelo de K.C. Lee, hasta los análisis de sobretensiones transitorias de onda viajera y por conexión de capacitores. La motivación de este trabajo consiste principalmente en contar con un sustento teórico-técnico (actualmente escueto) para determinar el espaciamiento de apartarrayos en redes de distribución y que impacte en el aumento de la calidad del suministro eléctrico.

Joint experimental and theoretical study on vibrational excitation cross sections for electron collisions with diacetylene.

We have measured and calculated differential and integral cross sections for elastic and vibrationally inelastic electron scattering by diacetylene molecules at electron energies from 0.5 to 20 eV in the whole range of scattering angles from 0 to 180°. The calculations were carried out using the discrete momentum representation method (DMR), which is based on the two-channel Lippmann-Schwinger equation in the momentum space. The interaction between the scattered electron and the target molecule is described by the exact static-exchange potential. Correlation-polarization forces are included by a local density functional theory. Energy dependences of integral and differential cross sections are presented for all nine vibrational modes. A detailed comparison of theoretical and experimental electron energy loss spectra is presented for electron energies of 1, 5.5, 10, and 20 eV. The theory assigns symmetry of resonances that could not be determined by empirical analysis alone. The theory reveals, and quantitatively describes, the switching of partial waves accompanying excitation of nontotally symmetrical vibrations. Limitations of the theory in reproducing experimental data for the narrow π* resonance below 2 eV are mentioned.

Design of free-space optical interconnects using two Gabor superlenses

We propose a novel design of micro-optical devices based on multi-aperture compound insect eyes, which transfer a point-to-point multichannel free space signal combined with a diffraction grating. The system is inspired in the refractive superposition compound eyes configuration known as Gabor superlens (GSL) using microlens arrays. A switching function and wave division multiplexing are achieved by introducing a diffraction grating placed in the global focus of the system. The source characteristics, either coherent or incoherent, influence the device performance.

Tunable terahertz wave Goos–Hänchen shift of reflected terahertz wave from prism–metal–polymer–metal multilayer structure

We propose a scheme to manipulate the Goos–Hänchen shift of a terahertz wave reflected from the prism–metal–polymer–metal interface via external voltage bias. By adjusting the external voltage bias, the refractive index of the nonlinear polymer can be changed, so the lateral Goos–Hänchen shift is dynamically tuned. The relation among the Goos–Hänchen shift, prism and the nonlinear polymer is investigated in theory analysis and simulation. Using this scheme, the Goos–Hänchen shift can be tuned without changing the original structure of the proposed device. Numerical calculation results further indicate that the proposed structure has the potential application for the integrated terahertz wave switch.

Design of Micro Power Consumption Synchronous Chopped Wave Power Supply Based on Fixed and Mobile Double Comparative Point

This paper proposes a design method of the micro power consumption synchronous chopped wave and low-power switching power supply based on fixed and mobile double comparative point. The output of this power supply ranges from 5V to 200V. It overcomes the residual voltage effect after the bridge rectifier by using fixed comparative point to limit the maximum output voltage, and stabilizes the voltage by using mobile point to produce the required output voltage. The circuit charges with nonlinear resistors pattern in the low voltage, thus improving the charging efficiency, and it has short circuit protection function, simple structure and low power consumption.

Numerical simulation of burning front propagation

In the context of a numerical experiment, it is shown that the switching wave described by the reaction-diffusion equation can be delayed at a medium inhomogeneity with a thickness Δ and amplitude Δβ for a finite time τ = τ(Δβ, Δ) up to a complete stop at it (τ = ∞). Critical values Δβc and Δc corresponding to the autowave stop are found. The similarity laws \(\tau \sim (\Delta _c - \Delta )^{ - \gamma _\Delta } \) and \(\tau \sim (\Delta \beta _c - \Delta \beta )^{ - \gamma _\beta } \) are established, and the critical indices and are found. The similarity law is established for critical values of amplitude and width of the inhomogeneity corresponding to the autowave stop Δβc ∼ Δc-δ where δ ≈ 1.

Fast-response terahertz wave switch based on T-shaped photonic crystal waveguide

We design an ultra-fast terahertz wave switch based on T-shape photonic crystal waveguide. The polymer rod is added in the junction as a point defect, the refractive index of which can be varied by adjusting the external pump laser intensity. The transmission spectrum is calculated by finite-difference time-domain method, which shows that the output energy of the two output ports is closely related to the refractive index of the polymer rod. By continuous wave excitation of the guided mode, the simulation results show that the T-shaped photonic crystal waveguide can flexibly tune the power in two output ports. The tuning rate of the device is about 0.3ns. These results provide a useful guide and a theoretical basis for the developments of terahertz wave functional components.

Detection of Fault in a 400 kV Transmission Line Using EMTP and ANN Method

Power transmission and distribution networks are important for the supply of quality power to the consumers. The rating of the protective device and the co-ordination play a vital role in improving the power quality in Electrical power systems. Since, generating stations exists far away from the load centers and the transmission lines have to run over long distances, the probability of occurrence of faults in transmission lines are very high. Due to such line faults, the system gets destabilized and requires immediate isolation. Therefore, fault analysis is very critical and essential issue in electrical power system with regard to fault clearance and power supply restoration with minimum interruption. In order to detect fault in transmission line, simulation of fault conditions has been carried out by dividing the total length of transmission line into large number of π sections. The π section comprises the series inductance and resistance of line and capacitance to ground. Single phase, double phase and three phase to ground faults are simulated at various distance from generator transformer and fault currents are calculated using electromagnetic transient programme (EMTP). Fault currents are also calculated by simulating faults at different points on wave to account for randomness of fault occurrence. Various time ~ current characteristics are used to train neural network and tested for detecting a specific fault using the untrained data of several faults at other distances. A comparison was made for efficiency of fault detection between time domain and frequency domain data. The neural network calculation was extended to currents determined from point- on wave switching for fault simulation