INFLUENCE OF CHARACTERISTICS OF A NONLINEAR TRANSFORMER TO WORK THE INVERTER

The article deals with the modes of switching on an inverter with a sinusoidal output voltage when working with a nonlinear transformer. The study is implemented by simulation modeling in Simulink Matlab. Simulation is carried out using the SPS model of a nonlinear transformer with various core magnetization curves. It is shown that a soft start of the inverter, performed by a gradual increase in the sinusoidal modulating voltage, eliminates in-rushes of the primary current and the magnetization current, regardless of the modulation voltage switching angle. The process of forming a hysteresis loop for a given magnetic flux is considered. The time diagrams of the direct starting-up the converter are given at various values of the modulation voltage initial phase for a core with a hysteresis loop. It is shown that the statistical characteristics of the inverter do not depend on the type of the transformer’s core magnetization curve.

Frequency Tunable Non-Reciprocal Bandpass Filter and Diplexer Using Time-Modulated Microstrip λg/2 Resonators

This paper presents novel designs of frequency reconfigurable distributed non-reciprocal bandpass filter and diplexer based on spatio-temporally modulated microstrip λg/2 resonators. The modulation is achieved by loading both ends of the λg/2 transmission line resonators with time-modulated capacitors. To provide an inherent biasing isolation between the RF and the modulation signals, the modulation voltage source is connected at the center of the resonator, where there is a natural voltage null. A single inductor is used to further enhance such biasing isolation. The wideband nature of this isolation scheme enables the tuning of the devices over a wide frequency range. With more than 30-dB RF to modulation isolation, the proposed resonator structure also enables low insertion loss by eliminating RF signal leakage to the modulation ports. Two examples of a 3-pole bandpass filter and a diplexer are demonstrated with good agreement between the measurement and the simulation. The fabricated filter shows a minimal insertion loss of 3.9 dB, a 20-dB isolation bandwidth of 42 MHz at 1.0 GHz, and frequency tuning range of 885-1031 MHz. The measured diplexer has two non-reciprocal bandpass channels at 829 MHz and 997 MHz, respectively. The two channels can be independently reconfigured without affecting each other.

Frequency Tunable Non-Reciprocal Bandpass Filter and Diplexer Using Time-Modulated Microstrip λg/2 Resonators

This paper presents novel designs of frequency reconfigurable distributed non-reciprocal bandpass filter and diplexer based on spatio-temporally modulated microstrip λg/2 resonators. The modulation is achieved by loading both ends of the λg/2 transmission line resonators with time-modulated capacitors. To provide an inherent biasing isolation between the RF and the modulation signals, the modulation voltage source is connected at the center of the resonator, where there is a natural voltage null. A single inductor is used to further enhance such biasing isolation. The wideband nature of this isolation scheme enables the tuning of the devices over a wide frequency range. With more than 30-dB RF to modulation isolation, the proposed resonator structure also enables low insertion loss by eliminating RF signal leakage to the modulation ports. Two examples of a 3-pole bandpass filter and a diplexer are demonstrated with good agreement between the measurement and the simulation. The fabricated filter shows a minimal insertion loss of 3.9 dB, a 20-dB isolation bandwidth of 42 MHz at 1.0 GHz, and frequency tuning range of 885-1031 MHz. The measured diplexer has two non-reciprocal bandpass channels at 829 MHz and 997 MHz, respectively. The two channels can be independently reconfigured without affecting each other.

Multilevel Inverter for AC Drives with Less Number of Swiches

Multilevel inverter plays an important role at today's time. This gives us a good measure of voltage, reduces harmonic integrity, reduces energy loss and also gives us high levels of energy. The different types of topology that are produced takes reduce amount of power, voltage source and voltage switching as compared to traditional topology. This paper focuses on the variety of modes in the multilevel inverter, methods of modulation, voltage stress and how to eliminate the effect of total harmonic distortion. In the end the advantages and disadvantages of the review topology is concluded.

Deep Electrical Modulation of Terahertz Wave Based on Hybrid Metamaterial-Dielectric-Graphene Structure

A terahertz modulation structure based on hybrid metamaterial and graphene is proposed and demonstrated in this work. The metamaterial with a square slit ring array excites terahertz resonance in the slits and enhances the interaction between the terahertz wave and graphene. The graphene layer acting as the active material is tuned by the applied electrical field. With the separation by a dielectric layer between the graphene and the metallic structure, the resonant frequency and transmitted energy are both modulated by the graphene. Experimental result indicates that the modulation depth of the terahertz transmitted amplitude is 65.1% when the applied modulation voltage is tuned 5 V.