A Novel Mobile Phone Antenna for Effectively Reducing Specific Absorption Rate

In this paper, a novel mobile phone antenna that can effectively reduce the harm of electromagnetic radiation to the human body is proposed. An inverted F-shaped antenna (IFA) is designed to reduce specific absorption rate (SAR) and all the measurements are done in over the air (OTA) test system. Measured results show that the proposed mobile phone antenna has excellent electrical characteristics such as reflection coefficient (700–870 MHz and 1710–2450 MHz), radiation pattern, total radiation power (TRP >17.5 dBm), hot spot map and low SAR values (< 1.4 W/kg). Due to these advantages, the proposed antenna is used to reduce SAR in the future mobile phone

Enabling Technologies towards 5G Mobile Networks

Future ,fith-generation (5G) mobile networks denote the next-generation mobile networks beyond the current 4G mobile networks. The 5G networks are provisioned by the Next Generation Mobile Networks Alliance to provide much higher capacity and support various types of emerging applications with stringent quality of service (QoS) requirements. The objective of this special issue is to solicit the state-of-the-art research contributions that present key and emerging results on 5G-enabling technologies to optimize spectrum efficiency and provide heightened security and privacy

An Ultra-Wideband Circularly Polarized Asymmetric-S Antenna With Enhanced Bandwidth and Beamwidth Performance

This paper introduces an ultra-wideband circularly polarized (CP) asymmetric-S antenna with wide axial ratio beamwidth (ARBW) for C-band applications. The proposed antenna is realized by bending a linearly polarized dipole into asymmetric-S shape with variable trace width, which achieves CP radiation. Unlike the reported symmetric-S antenna, the proposed antenna is constituted with two unequal curved arms to enhance the bandwidth and beamwidth performances. Compared with the symmetric-S antenna, the proposed antenna demonstrates much wider AR bandwidth and wider ARBW over broader frequency range. A prototype is fabricated to verify the design principle. The measured and simulated results are very consistent and both indicate that the proposed antenna has a wide impedance bandwidth (VSWR <; 2) of 70.2% (3.58 to 7.46 GHz), and a wide 3-dB AR bandwidth of 84.8% (2.75 to 6.8 GHz). Moreover, maximum ARBW of 153° is achieved, and a 3-dB ARBW of more than 100° is maintained within a wide operation bandwidth of 46.3% (3.65-5.85 GHz)

Wideband Circularly Polarized Tightly Coupled Array

Tightly coupled arrays (TCA) have received considerable interests recently. Although various TCAs have been reported, they are limited to single or dual linear polarizations. Considering the importance of circular polarization (CP) in various wireless systems, it is meaningful to design a CP TCA with a simple configuration. This paper presents a circularly polarized tightly coupled crossed dipole array (CP-TCCDA) with wide overlapped impedance bandwidth and axial ratio (AR) bandwidth. A tightly coupled crossed dipole unit cell is investigated and the comparison with an isolated crossed dipole of the same size indicates that the VSWR<3 bandwidth is increased from 3:1 to 7.1:1 while the 3-dB AR bandwidth is increased from 1.3:1 to 2.1:1. Analysisis given to explain the principles of AR bandwidth improvement and is verified by the comparison of radiated Efields between a CP-TCCDA and a conventional crossed dipole array. To verify the design concept, a 4×4 CP-TCCDA with feeding network is fabricated and measured. The measured results confirm that the proposed array achieves VSWR<3 bandwidth from 2.06GHz to 6.46 GHz (3.14:1) and 3-dB AR bandwidth from 2.35GHz to 5.6GHz (2.38:1), which are much wider than the bandwidth of an isolated element and a conventional array using the same element

Single-Layer Wideband Circularly Polarized High-Efficiency Reflectarray for Satellite Communications

This paper presents a single-layer circularly polarized (CP) reflectarray which achieves large bandwidth in terms of axial ratio (AR), gain, aperture efficiency and radiation pattern. By using a novel wideband S-shaped phasing element, an offset-fed reflectarray with 20° offset beam is designed based on the element angular rotation method. Theoretical analysis is given to analyze the effect of angular rotated elements on the performance of the reflectarray, which indicates that the AR bandwidth of the reflectarray can exceed the AR bandwidth of the feed horn. Furthermore, the influence of the differential spatial phase delay is analyzed quantitatively, and the performance of S-element-based reflectarrays with different aperture sizes are investigated and discussed. To verify these concepts, a 180mm×180mm prototype with 15×15 elements is fabricated and measured. The measured results confirm that the proposed reflectarray achieves a 68.5% 3-dB AR bandwidth (7.0 GHz to 14.3 GHz) and a 47.8% 3-dB gain bandwidth (8.6 GHz to 14 GHz). Moreover, the aperture efficiency is larger than 50% in a 33% bandwidth and larger than 30% in a 64% bandwidth

A Differential Broadband Dual-Polarized Base Station Antenna Element for 4G And 5G Applications

In this paper, a broadband differential feed ±45° dual-polarized base station antenna element is proposed for 4G and 5G mobile communications. The proposed antenna consists of two orthogonally placed dipoles, square patch and reflector, where each dipole adds six elliptical branches to broaden the bandwidth. Simulation results show that the proposed antenna element has the impedance bandwidth of 65% (1.84-3.6 GHz) within the operating frequency (S11 <; -15 dB and S21 <; -21 dB), and good radiation characteristics and high cross polarization ratio are also achieved

Machine Learning Models for Multiparametric Glioma Grading With Quantitative Result Interpretations

Gliomas are the most common primary malignant brain tumors in adults. Accurate grading is crucial as therapeutic strategies are often disparate for different grades and may influence patient prognosis. This study aims to provide an automated glioma grading platform on the basis of machine learning models. In this paper, we investigate contributions of multi-parameters from multimodal data including imaging parameters or features from the Whole Slide images (WSI) and the proliferation marker Ki-67 for automated brain tumor grading. For each WSI, we extract both visual parameters such as morphology parameters and sub-visual parameters including first-order and second-order features. On the basis of machine learning models, our platform classifies gliomas into grades II, III, and IV. Furthermore, we quantitatively interpret and reveal the important parameters contributing to grading with the Local Interpretable Model-Agnostic Explanations (LIME) algorithm. The quantitative analysis and explanation may assist clinicians to better understand the disease and accordingly to choose optimal treatments for improving clinical outcomes. The performance of our grading model was evaluated with cross-validation, which randomly divided the patients into non-overlapping training and testing sets and repeatedly validated the model on the different testing sets. The primary results indicated that this modular platform approach achieved the highest grading accuracy of 0.90 ± 0.04 with support vector machine (SVM) algorithm, with grading accuracies of 0.91 ± 0.08, 0.90 ± 0.08, and 0.90 ± 0.07 for grade II, III, and IV gliomas, respectively