Том 62, № 8 (2019)

Electromagnetic eigenwaves in a weak ferromagnetic with anisotropy of the “easy plane” under magnetization in this plane are investigated. It is shown that at frequencies of anti-resonances the weak ferromagnetic can be considered as environment with characteristic impedance close to zero. The polarization of eigenwaves in such environment is analyzed on the example of high-temperature weak ferromagnetics—hematite and iron borate. It is proposed to consider the weak ferromagnet-metal structure as an element of the metasurface with a controlled phase shift of the reflected wave. A tunable Fabry-Perot resonator with a weak ferromagnet-metal structure (ferromagnet is of sub-wave thickness) is considered and the corresponding frequency-field dependencies in the sub-terahertz range are studied. It is shown that such resonator combines rather high Q-factor with a possibility of magnetic tuning of its resonance frequency. The maximum local slope of the field dependence of the resonator frequency reaches 0.3 MHz/Oe using a hematite layer and 0.6 MHz/Oe using an iron borate layer of 10 µm thickness. The resonator unloaded quality factor for the main mode varies within 300–1400 and 250–1000, respectively.

In this article an S-shaped rectangular microstrip patch antenna (RMSA) is investigated for S-band applications using artificial neural network (ANN). The authors have done the parametric study of different radiating structures to obtain S-shaped RMSA. The size of inserted notches on the radiating patch for achieving wideband operation is computed through multilayer perceptron artificial neural network (MLP-ANN) over a desired range of its performance effecting parameters such as frequency, gain, directivity, antenna efficiency, and radiation efficiency. MLP-ANN model is trained and tested with seven different algorithms. The research found that Levenberg-Marquardt (LM) training algorithm takes less computational time with better accuracy for computation of notches size on radiating patch over a priory defined performance parameters. To verify the work, a prototype of S-shaped RMSA is physically fabricated on foam substrate and tested experimentally. The experimental results are in good agreement with the simulated results that are produced with ANN.

In the modern age, wireless communication has taken on a wide range of applications in different aspects of a human life. Ever increasing demand for higher data rates led the interest of research in FBMC (Filter Bank Multi-Carrier) as a new transmission system for the next-generation mobile communication system. FBMC is a multicarrier technique which utilized filters at the transmitting and the receiving side of the system. It is considered as one of the most promising waveform for fifth generation mobile communication system (5G). But, high value of Peak Average Power Ratio (PAPR) is considered to be one of the giant problems in FBMC. The PAPR reduction techniques used in OFDM cannot be utilized in FBMC due to its overlapping structure. Hence, new PAPR reduction techniques for FBMC have diverted the attention of researchers. In this work, dispersive selective mapping (DSLM) PAPR reduction technique is proposed. Further, the proposed technique is compared to selected mapping (SLM) and clipping PAPR reduction techniques. The simulation results show that the proposed DSLM technique gives the better performance in terms of bit error rate (BER), PAPR and complexity as compared to the SLM and clipping PAPR reduction techniques.