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This paper proposes a single-stage direct AC to high-frequency (HF) AC resonant converter based on LLC configuration for induction heating (IH) systems or HF applications. Unlike conventional converters for IH systems, the proposed topology converts the utility frequency to HF AC in a single stage without using a DC link inductor and capacitors and takes the advantages of LLC configuration. Additionally, it improves the power factor to 0.9–1, lowers the THD (3.2% experimentally), and protects against the high-frequency components. An embedded control scheme was designed to keep the HF current oscillating at a resonant frequency, ensuring zero-voltage switching. The operating principle of the proposed topology was investigated using mathematical equations and equivalent circuits. Finally, it was verified using computer simulation, and an experimental prototype of 1.1 kW was developed to demonstrate the proposed topology's uniqueness. [ABSTRACT FROM AUTHOR]

A dual output dual-frequency (DODF) resonant converter-based AC-AC induction heating (IH) by using asymmetrical duty cycle (ADC) control is presented in this paper. The proposed scheme gives two outputs with independent power control, which improves input power factor and achieves zero voltage switching (ZVS) with a wide range of operations. It includes two pairs of two half-bridge series resonant converters, each pair having one common capacitor along with various resonant frequencies. These converters are modulated with the ADC control scheme to obtain smooth operation. The proposed topology doesn't use the DC stage; it is directly connected to the power supply to produce high-frequency AC output. With the use of direct connection, the converter components are reduced when compared to conventional converters. There will be a reduction in voltage drop, power losses, cost of the converter and which will result in improved efficiency. Simulation results are obtained from PSIM 11.1.7 software. This scheme controls two different loads with an efficiency of 98.25%. [ABSTRACT FROM AUTHOR]

In this article, a graphene-dielectric resonator-based antenna is designed in the THz frequency regime. Circular polarization is achieved by feeding the cylindrical-shaped ceramic using a perturbed square-shaped aperture. Graphene loading over the alumina ceramic provides the frequency reconfigurable feature. In order to overcome the difficulty of simulating the THz antenna (i.e., very large simulation time), machine learning algorithms such as the artificial neural network (ANN) and random forest are used to effectively predict the performance of the designed antenna. The proposed antenna works effectively in between 5.0 and 5.5 THz with a 3 dB axial ratio frequency range from 5.1 to 5.35 THz. There is good correlation found between the predicted, measured, and simulated reflection coefficient and axial ratio. Due to stable radiation properties and good diversity performance within the operating frequency band, the proposed antenna can be employable for different wireless applications in the THz frequency regime.