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A compact metasurface-based circularly polarized (CP) dielectric resonator antenna (DRA) is proposed with wideband characteristics. The antenna forms a very simple structure, composed of a rectangular DR, a single coaxial probe, and plus-shaped unit cells-based metasurface. The metasurface is realized on a grounded FR-4 substrate. Next, a rectangular DR is loaded centrally over the metasurface. The DR is fed with a perturbed probe feed at an appropriate angle of ( $\theta $ =29°), along the diagonal line. Thus, a novel hybrid technique involving the angle of feed location from the center of DR, and the N $\times $ N unit cells-based metasurface is utilized for generating a wideband CP radiation. The resonance from the rectangular DR and surface waves along the $7\times $ 7 plus-shaped unit cells-based metasurface is exploited to achieve a wide 3-dB axial ratio (AR) and impedance matching bandwidth. The fabricated antenna prototype used for the validation of predicted results confirms the successful implementation of the proposed technique. Measured results demonstrate a wide impedance bandwidth of 32% (3.6 GHz - 7.0 GHz) and an overlapping 3-dB AR bandwidth of 20.4% (4.2 GHz - 5.2 GHz). Moreover, the antenna adopts a left-hand circular polarization (LHCP) with 6–7 dBic measured gain within the operational frequency range. Overall, the proposed antenna offers low-profile, simplicity, ease of design, and high performance.

Energy harvesting (EH) or scavenging is recognized as harvesting energy from ambient energy sources in the surrounding environment. This paper reports a literature review on radio frequency (RF) EH using different metasurface/metamaterial structures based on split-ring resonators (SRRs), electric inductive-capacitive (ELC) resonators, square-patch unit cells, square-ring unit cells, etc. The essential parameters in rectifying antenna (rectenna) design are included, such as receiving antenna efficiency, conversion efficiency, dimensions, supporting substrate properties, frequency band, and overall performance, etc. It is noted that rectenna design using conventional antennas such as microstrip antennas, monopole antennas, slot antennas, dielectric resonator antennas, etc. suffers from low power conversion efficiency with larger size. To overcome the above-mentioned constraints and enhance the conversion efficiency with smaller size, metasurface/metamaterial structures are used as EH collectors. An introduction to EH is discussed, followed by an overview of energy sources in the ambient environment. Several hypothetical and experimental studies on metasurface-based EH systems are summarized.

In this article, a low profile circularly polarized (CP) antenna with wide 3-dB axial ratio beamwidth (ARBW) is presented. Two-pair of parallel slots are etched on a circular patch and manifested as magnetic dipoles (MDs). These narrow slots are arranged symmetrically about the axes, and one pair is orthogonal to another pair of slots. The philosophy of CP radiation across a wide angular range strongly depends on the spacing between the paired-dipoles, for example spacing of $0.22\lambda _{0}$ , two-orthogonal far-field radiated components become equal across a wide-angle. Moreover, this particular spacing between the paired-dipoles provides a symmetrical electric field distribution along the periphery of the patch, which ensures the broadside LHCP radiation with wide 3-dB ARBW of 228° and 214° at the plane of $\varphi = 0^{\circ }$ and $\varphi = 90^{\circ }$ , respectively. The measured results from the fabricated prototype exhibit good agreement with the simulated results. The antenna has impedance bandwidth (IBW) and CP bandwidth (CPBW) of 2.6% (64 MHz), and 0.9% (22 MHz), respectively. The broadside radiation holds antenna gain higher than 5 dBic across the entire CPBW.

A miniaturized four-element antenna of 20 mm × 20 mm with edge-to-edge distance of 4.9 mm between the array antennas operating from 4.6–8.6 GHz is investigated in this article. The antenna consists of 4 × integrated dipole driven elements, and complementary split ring resonator (CSRR) metacells are loaded on the both sides of each dipole arms. The loaded meta-couplers magnetically couple to dipole drivers, and the induced resonance effect improves the 10-dB impedance bandwidth (IBW) to 60.6%. To improvise the isolation between antenna elements, metallic vias are implemented that trap electromagnetic (EM)-surface waves to condense into the ground. So, the meta-couplers induce electromagnetic (EM)-propagation as surface wave trapments for radiation and decouple near-field condensed currents, acting as couplers/decouplers. The maximum isolation achieved is >−22.5 dB without any external decoupling network. The diversity parameters indicate good attributes in isotropic, indoor, and outdoor channel environments with an envelope correlation coefficient (ECC) < 0.165 and realized gain of 5.5 dBi with average radiation efficiency of 80–90% in the desired operating bands. An equivalent circuit model using lumped components is designed for the proposed four-element antenna. For validation, a prototype antenna is fabricated and measured to be implemented in 5G applications, which shows good correlation with the full-wave simulated results.

Low‐profile miniaturized wideband circularly polarized (CP) monopole and multiple‐input‐multiple‐output (MIMO) antennas using characteristic mode analysis (CMA) are presented. The antennas are constructed with a microstrip feeding line, a slot, and a branch, which positions the transmission line perpendicularly to the branch to achieve CP. The CP characteristic is realized through a characteristic angle (CA) difference of approximately 90° at three mode significance (MS) intersections across four modes. CMA provides both theoretical analysis and design guidance for these antennas. The antennas were fabricated and tested, with dimensions of 0.48λ₀ × 0.48λ₀ × 0.03λ₀ and 0.47λ₀ × 0.47λ₀ × 0.03λ₀, where λ₀ represents the free‐space wavelength. Measurements indicate that the monopole antenna achieves a −10 dB impedance bandwidth (IBW) from 3.2 to 8.4 GHz (89.7% relative bandwidth), a 3 dB axial ratio bandwidth (ARBW) from 3.6 to 5.1 GHz (34.5%), and a peak gain of 6.6 dBic. The MIMO antenna has a −10 dB IBW from 3.1 to 8.2 GHz (90.3%), a 3 dB ARBW from 3.2 to 6 GHz (60.9%), and a peak gain of 5.1 dBic. Both antennas feature a low profile, ultra‐wideband IBW, broadband ARBW, and miniaturized design, making them suitable for wideband wireless communication applications. Key Points: Low‐profile miniaturized wideband circularly polarized (CP) monopole and multiple‐input‐multiple‐output (MIMO) antennas using CMAThe microstrip feeding line and slot and the branch, which makes the transmission line perpendicular to the branch to obtain the CPThe CP characteristic can be achieved by a CA difference of approximately 90° at three intersections of MS for four modes [ABSTRACT FROM AUTHOR]

Introduction: Dengue fever is a common mosquito-borne viral disease which has reached alarming size in the past few years. It is endemic in more than 100 countries and significant differences were found in clinical profile and atypical manifestation. Aim of the Study: A retrospective observational study of clinical profile and atypical manifestations in patients with dengue fever. Materials and Methods: Serum samples were collected from clinically suspected cases of dengue fever and it was confirmed by NS1 antigen, IgM, and IgG antibody by ELISA. Clinical details and atypical manifestations were recorded. Observation: During the study period, a total of 2502 patients were suspected to have dengue infection, of which 464 (18.5%) samples were found to be positive for dengue viral infection. A majority of the cases were males [268 (57%)] when compared with females [196 (42%)]. Fever was the most common clinical presentation seen in all the patients, followed by headache (78.4%), myalgia (61%), body pain (49.3%), vomiting (40%), joint pain (31.5%), dry cough (19%), nausea (14%), abdominal pain (8%), diarrhea (5.6%), retro-orbital pain (04%), burning micturition (2.4%), and rashes (0.6%). Among atypical manifestations, hepatomegaly [32 (7%)] was the most common, followed by splenomegaly [23 (5%)], bradycardia [18 (4%)], meningitis [6 (1.2%)], hemoptysis [5 (1%)], acalculous cholecystitis [4 (0.8%)], and acute pancreatitis [2 (0.4%)]. The study of hematological parameters showed thrombocytopenia was present in 179 (38.5%) patients, followed by leukopenia [77 (17%)] and raised hematocrit [29 (6.2%)]. Conclusion: During ongoing epidemics, the clinical profile and atypical manifestations in clinically suspected dengue patients should be investigated early so that severe forms can be treated promptly.