Techniques to Improve the Performance of Planar Microwave Sensors : A Review and Recent Developments

Planar microwave sensors have become increasing developed in recent decades, especially in material characterization (solid/liquid) as they provide regions highly sensitive to the surrounding medium. However, when it comes to deciphering the content of practical biological analytes or chemical components inside a host medium, even higher sensitivities are required due to their minute concentrations. This review article presents a comprehensive outlook on various methodologies to enhance sensitivity (e.g., coupling resonators, channel embedding, analyte immobilization, resonator pattern recognition, use of phase variation, using coupled line section, and intermodulation products), resolution (active sensors, differential measurements), and robustness (using machine learning) of arbitrary sensors of interest. Some of the most practical approaches are presented with prototype examples, and the main applications of incorporating such procedures are reported. Sensors with which the proposed techniques are implemented exhibit higher performance for high-end and real-life use

Reprocessing the Indicators of Human Capabilities Development in the light of Imam Ali’s (peace be upon him) Order to Malek Ashtar

In addition to give an introduction on capability approach, in this study, according to instructions of Imam Ali’s (peace be upon him) letter 53 of Nahj al-Balaghah, authors tried to considered effective range of indicators in human capabilities development. In order to data collection, the precious text of letter 53 of Nahj al-Balaghah as a source of information has been coded and analyzed using thematic analysis. The results include twelve sub-themes on this subject which are: the philosophy of governance, human agency of people, the divine authority of human, reforming public affairs as an inalienable right, multiple stockholders, motivation, respecting positive authority, justice, equity, developing health and economic opportunities, developing supportive opportunities and reclamation and reforming cities and towns; and five main themes which are: central phenomenon of human capabilities development, the casual and intermediary conditions in capabilities development, and their underlying conditions and final consequences. Finally, using the main and subsidiary themes, a framework has been proposed to develop the human capabilities approach

Generalized Phase-Polarization Cancellation for Broadband Radar Cross-Section Reduction

This study presents a novel approach to decrease the radar cross-section (RCS) by integrating and expanding the phase cancellation and polarization conversion methods. In this proposed technique, only one unit cell, akin to the polarization conversion method, is utilized. The RCS reduction surface is comprised of arrays of this unit cell; each array is rotated by 90 degrees in relation to its neighboring arrays. Unlike previous RCS reduction methods, which employed periodic arrangements of unit cells that either kept the polarization of the reflected wave unrotated or rotated it by 90 degrees, the proposed generalized method enables the unit cells to rotate the polarization of the reflected wave arbitrarily. This is achieved by eliminating the symmetry requirement in the unit cell design. The mathematical theory for the proposed RCS reduction method has been developed. To demonstrate the method’s feasibility, a unit cell was designed using a pattern optimization method based on the pixelization of the cell surface, and a binary particle swarm optimization algorithm was employed as a proof of concept. A surface was formed by constructing $4\times 4$ arrays of $7\times 7$ designed unit cells, where each array was rotated 90 degrees relative to its side array. The measured results demonstrate a 10-dB monostatic RCS reduction bandwidth of 115%, from 2.8 GHz to 10.4 GHz, which is in excellent agreement with the bandwidth obtained using the developed theory

A Broadband Doherty Power Amplifier for Sub-6GHz 5G Applications

This paper presents a novel and accurate procedure for designing a Doherty power amplifier (DPA) for wireless systems. The method is based on a systematic approach to designing the matching networks of both Main and Auxiliary devices, which employs an optimization process to set their input impedance in the corresponding optimal regions obtained from the standard load- and source-pull simulations. To import the optimum regions of each device into the optimization algorithm, mathematical expressions are derived and graphically reported on the Smith chart. Besides this, we have developed an accurate method to account for the loading effect of the Auxiliary amplifier on the Main one at back-off when designing the Main PA. As a proof of concept, a symmetric DPA is designed, fabricated, and tested. The measurements showed a working frequency band of 3.3–3.9GHz (aimed at n78 band of 5G-NR), a minimum peak output power of 36W, drain efficiency between 48%–53.2% at peak and 34.6%–44.5% at 6dB back-off

Magneto-dielectric properties of Ni0.25Cu0.25Zn0.50Fe2O4–BaTiO3 and its application as substrate of microstrip patch antennas

This study explores the properties and potential of magneto-dielectric (MD) material Ni0.25Cu0.25Zn0.50Fe2O4–BaTiO3 as an antenna substrate for miniaturization and bandwidth enhancement. The MD material was synthesized using a solid-state method and different amounts of BaTiO3 (0, 5, 10, 15 and 20%) were added to improve its relative permittivity. Various investigations were carried out to analyze the crystallographic structure, microstructure, magnetic properties, permittivity, permeability, and losses of the samples at microwave frequencies. Results show that the MD composite with 5% BaTiO3 achieved a relative permittivity of 12.5 and a permeability of 2.9 at 0.7 GHz has enhanced the antenna’s operating bandwidth with a fractional bandwidth of 61.1% and directivity of 3.1 dBi. The MD material with 20% BaTiO3 showed potential as an antenna substrate for miniaturization, with a relative permittivity and permeability of 17.1 and 1.9, respectively. It also displayed better gain (- 8.9 dBi) and radiation efficiency (8%) compared to the antenna with 5% BaTiO3 (with a gain of - 14.4 dBi and radiation efficiency of 1.8%) as an antenna substrate. The findings of this study suggest that MD materials have significant potential as antenna substrates for miniaturization and bandwidth enhancement