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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.

In this article, a miniaturized reconfigurable 4‐element ultra‐wideband (UWB) multiple‐input‐multiple‐output (MIMO) antenna is proposed to operate from 2.52 to 24 GHz, and studied using characteristics mode analysis (CMA). Initially, a 1‐element antenna is designed and then extended to 4‐element MIMO configuration. The MIMO antenna achieves design merits by orthogonally sorting fractal radiators for miniaturization, a Γ‐shaped slot for band‐notching and rotationally symmetric connected ground for isolation. CMA is explored to study the band‐notched behavior effect in antenna, which shows two operating modes, NM‐mode and NB‐mode (NM: normal‐mode, NB: Notched‐mode). The modal metrics is discussed for both modes giving an insights on the bandwidth and radiation potentials. Four RF p‐i‐n diodes are mounted at the Γ‐shaped slot orifice on each antennas, to control the band‐notched operation. At OFF‐state, the antenna is with wide‐band‐rejection from 3.7 to 8.87 GHz and at ON‐state, it works in pure UWB mode. To demonstrate its feasibility, a fabricated antenna of size 24 mm × 24 mm is experimented which are in good agreements with simulated results. [ABSTRACT FROM AUTHOR]

We propose a compact planar passband frequency selective surface (FSS) operating at the resonance frequency of 3.81 GHz. The proposed FSS is composed of single layer of the Archimedean spiral type with the interdigital capacitance between the corners of metallic patches printed on one side of the substrate. Compared to the operating wavelength, the size of the proposed single layer FSS is 0.066λ0 (λ0 is the free space wavelength at 3.81 GHz). The performance such as transmission and reflection coefficient of the proposed FSS demonstrates excellent resonance stability for different polarization and different incident angles. Finally, the optimized simulated results are validated with measured results by a fabricated prototype of 31×31 array elements on 170×170 mm2 substrate area.

A wideband and high gain dielectric resonator antenna (DRA) operating in hybrid HEM11δ mode is proposed. The investigated geometry employs one cylindrical dielectric resonator partially covered with a transparent dielectric superstrate and backed up by a single side metal coated dielectric reflector plane. The reflector is dedicated for gain enhancement while the superstrate is employed for merging of two resonant bands resulting in a single wide band. The dielectric resonator is excited by simple microstrip feed slot coupling technique and operates over X-band, ranging from 7.12 GHz to 8.29 GHz, that is, of 15.18% impedance matching bandwidth with 11.34 dBi peak gain. The different development stages like standalone DRA, DRA with superstrate, DRA with reflector, and DRA with both superstrate and reflector plane with respect to bandwidth and gain performances are analyzed properly. To the best of authors’ knowledge, this is the first time this type of combination of both superstrate and reflector plane is demonstrated in DRA engineering. An antenna prototype was fabricated and characterized and a very good agreement is achieved between the simulated and measured results.

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. [ABSTRACT FROM AUTHOR]

Metasurface (MS) absorbers with polarization-insensitivity and wide-angle reception features have attracted much attention due to their unique absorption property. A polarization-insensitive broadband MS absorber structure, having wide-angle reception based on square split-ring resonators (SSRRs) and loaded with lumped resistors, is proposed in this paper. The proposed MS unit cell consists of a fixed-thickness FR4 dielectric substrate and a variable air-thickness substrate. The simulation results show that the proposed MS absorber is stable across a wide angular range for both normal and oblique incidences. Furthermore, the simulated results show that some parameters, such as unit-cell geometry and lumped resistors, can be varied to improve the performance of the MS absorber. The experimental results indicate that the proposed MS absorber can be achieved an absorption higher than 90% across the frequency range from 1.89 GHz to 6.85 GHz with a relative bandwidth of 113%, which is in agreement with simulation results. Thus, the proposed MS absorber can be more suitable in RF energy harvesting or wireless power transfer applications. [ABSTRACT FROM AUTHOR]

Low-power wireless sensors will play a big role in smart city applications. These sensors require a power supply to function. Batteries are not optimal for such numerous sensor networks because of their limited life and need for regular maintenance; hence, they are not a universal solution. RF energy harvesting (RFEH) and wireless power transfer (WPT) techniques have the potential to be a green and sustainable solution for supplying power to various low-power devices by capturing ambient RF energy. The ubiquitous nature of RF energy makes it available to exploit and reutilize in power wireless sensor nodes, wireless body area networks, wireless charging systems, RFID tags, and the Internet of Things ,. displays a conceptual diagram of an RFEH/WPT system. To capture power from free space that is transmitted by the base station, the harvesting node needs a receiving antenna and rectifier to convert the power into dc signals. This dc output is then further utilized to feed a low-power device. shows that at 10-m distance from the cellular tower, a digital batteryless watch was powered by a rectenna operating at 1.8 GHz. This LCD watch (low-power device) required 1.5 V to function and was successfully powered up using the RFEH system. [ABSTRACT FROM AUTHOR]

Background: The irrational use of antibiotics has led to the emergence of multi drug resistant pathogens. The phenomenon of MIC creeps occurs when organisms start showing raised MIC but within susceptible range giving an indication of the prevalence of rise in resistant pathogens in an area Methods: A cross sectional study in a large tertiary care hospital in North India to observe the susceptibility pattern among uropathogens and the possibility of MIC creeps. The Antimicrobial Susceptibility Testing (AST) and Minimum Inhibitory Concentration (MIC) were conducted by Vitek Compact 2. The identification of Extended Spectrum Beta Lactamase (ESBL) producers and Carbapenem Resistant Enterobacteriaceae (CRE) among Escherichia coli were noted. The MIC 50 and MIC 90 for Nitrofurantoin, the most widely used antibiotic for lower UTI, was calculated to investigate the phenomenon of MIC creep. Results: In our study, a total of 2522 urine samples were analyzed: 1538 (61%) were positive with the commonest isolate being E. coli (n=736, 47.8%) followed by Klebsiella spp. (n=178, 11%). Less than 10% of resistance was observed for Fosfomycin, Amikacin, Nitrofurantoin, Imipenem, Meropenem and Colistin. ESBL producers and CRE E. coli were 528 (72% of 736) and 79 (11% of 736) respectively. Overall, 119/736 samples had an MIC =128. Amongst the ESBL producers, 96/528 had MIC =128 and amongst the CRE, 13/79 had MIC =128. Discussion: E. coli can be used to reflect the trends in development of resistance. In the current study, it was observed that E. coli showed a reduced susceptibility for Nitrofurantoin indicated by a creeping increase in MIC albeit within normal range. Conclusion: Trends in rising MIC should alert prescribers to use drugs such as Nitrofurantoin judiciously. Antimicrobial stewardship practices should be strongly implemented in hospitals to curb rising resistance and obtain better treatment outcomes for patients with infectious diseases. [ABSTRACT FROM AUTHOR]

In this research article, a wideband mobile antenna with defected ground structure (DGS) is designed using characteristics mode analysis. It consists of a modified crescent‐shaped monopole antenna (M‐mode), L‐shaped stub (S‐mode), and DGS element (slot modes). Here, the fundamental resonating modes of M‐ and S‐mode are induced to operate in the integration mode (I‐mode) to obtain good impedance bandwidth (IBW). The DGS is implemented in ground plane to get slot modes (1 and 2). By combining slot modes with M‐mode and S‐mode, it exhibits broadened IBW (i.e., C‐mode), is suitable for the coverage of mobile bands (sub‐6 GHz frequency bands). For the clarity, modal investigation is performed at each critical stages of antenna designing process and the modal metrics like modal significance, characteristics angle (βn), Eigen values (λn), modal currents, and modal patterns are extracted by using Computer Simulation Technology (CST) Studio Suite. The proposed monopole antenna operates in multiband for wireless applications, that is, 880–960 MHz, 2.3–2.4 GHz, 2.4–2.483 GHz, 3.3–4.2 MHz, 3.3–3.8 GHz, 5.15–5.85 GHz, and WLAN (IEEE 802.11 b/g/n) respectively with measured gain of 3–5.5 dBi. A prototype of proposed antenna is fabricated and measured, which shows good agreements with simulation. To validate, averaged specific absorption rate (SAR) is investigated with 3D voxel phantom human head and hand model. The observed SAR 1 g lies between 0.0014 and 0.0462 W/kg in the operating bands, which are under the limits prescribed by the Federal Communications Commission (FCC). From the above outcomes, it can be potentially used in the mobile handsets and also, can be extended to hybrid wireless cellular communication networks & potential applications like RF energy harvesting. [ABSTRACT FROM AUTHOR]

In this research article, a printed dual‐polarized metasurface (MTS) inspired printed monopole antenna using characteristics modes theory (CMT) is investigated for UHF RFID applications. A T‐shaped monopole with U‐shaped asymmetric stubs is designed to generate circular polarization (CP) radiation traits. The grounded MTS layer is constructed with array of unit cells and fixed at air‐gap of λo/4 with reference to the monopole radiator (λo is free‐space wavelength at CP frequency band, 945 MHz), offering good impedance bandwidth (IBW), stable CP boresight radiation gain, and high radiation efficiency. By using CMT, interpretation of CP characteristics is highlighted, that is, the resonating modes exhibit asymptotic nature at the designated CP band with symptotic nature above and beyond the designated operating bands. Dual‐polarized characteristics are observed in both principal planes, due to the effect of grounded MTS loading. The prototype antenna of 0.315λo × 0.315λo is designed and validated. It operates from 836 to 1066 MHz with 24.18% IBW, 5.23% 3‐dB axial ratio bandwidth (ARBW) from 905.1 to 950 MHz and attains >6.8 dBic as a CP peak gain with the total efficiency of >83%. Prior to the attainment of good CP attributes in UHF RFID bands, it can be used for RF energy harvesting and wireless power transmission. [ABSTRACT FROM AUTHOR]

Ludwig’s angina is a rapidly spreading, potentially fatal infection of deep fascial spaces of the neck leading to airway oedema and death. This, in recent times when associated with COVID-19 infection, possess treatment challenges making the patient susceptible to opportunistic infections with reduced healing potential. Owing to the multifactorial aetiology in our case and addressing them at the earliest, it is important to achieve favourable outcomes. The space infection that seeded with untreated trivial dental caries progressed to necrotising fasciitis of neck with mycobacterial growth on cartridge-based nucleic acid amplification test for tuberculosis testing. The presence of Mycobacterium organisms should be speculated in patients with pulmonary signs of tuberculosis (TB) because a suppurative TB lymphadenitis of neck could also have the same presentation. The decisive moment in successful outcome was identification of mycobacteria in COVID-19 infected patient, thereby allowing to initiate the antitubercular therapy along with surgical debridement. Thus, medical management of patient with cohabiting infections is difficult task and needs appropriate addressal. [ABSTRACT FROM AUTHOR]

A new technique is developed to increase the axial ratio (AR) bandwidth of circularly polarized stacked microstrip antennas (CPSMAs) to about 15.0% by optimizing the location of the C-type single feed and a few other parameters. The stacked microstrip antenna with a quasi-planar surface-mounted short horn (SMSH) has achieved 13 dBi gain, 15.5% 3 dB AR bandwidth, 0.37 dB minimum AR and 25.0% impedance bandwidth. The measured gain is more than 11.5 dBic over the impedance bandwidth. The proposed technique simplifies the design of wideband circularly polarized antenna for medium to high gain applications. Index Terms--Axial-ratio, circularly polarization, feed optimization, short horn, stacked microstrip antenna.

We demonstrate a low-profile, compact antenna consisting of a cross dielectric resonator on a microstrip patch and a quasi-planar surface mounted short horn (SMSH). The measurements show a 10 dB return loss bandwidth from 6.07 GHz to 7.52 GHz (21.3%) and a gain better than 9.0 dBi over this bandwidth. The total height of the antenna is only 8.61 mm and the aperture size is 48.1 mm x 43.1 mm. The cross-polarization level of the antenna at boresight is better than 28 dB in both E-and H-planes over the impedance bandwidth. Index Terms--Dielectric resonator antenna (DRA), high gain, hybrid antenna, microstrip antenna, wide bandwidth.

We present a fast and accurate closed-form model for interactive computer-aided design and optimization of circular microstrip antennas on suspended or composite substrates. The model facilitates the computation of the resonance frequency, input impedance and bandwidth. We compare the results obtained with the proposed model with those from commercial software (2D-Ensemble and 3D-Microwave Studio), previously published experimental results and previously obtained theoretical results using another full-wave method. The proposed model shows better agreement with experimental results as compared to the commercial two-dimensional and three-dimensional software. Although all theoretical results show reasonable agreement among themselves, the proposed model is at least one thousand times faster than full-wave software. Index Terms--Antenna, cavity model, circular, closed-form, composite, computer-aided design (CAD), microstrip, multilayer, patch, suspended.

In this letter, a low-profile circularly polarized (CP) narrow-slots slotted-patch antenna for wide 3 dB axial-ratio beamwidth (ARBW) performance is presented. It consists of two pairs of narrow slots along the diagonal lines of a square patch with a single feed. These pairs of narrow slots are conceived and placed to serve as magnetic dipoles with quarter-wavelength separation, forcing the amplitude of the orthogonal electric field components to be equal across a wide angle. The 3 dB ARBW of the CP antenna is a strong function of the mutual magnetic field, which is feasible to alter with different parameters of the slot. The location, dimensions, and gap between the slots are tuned to achieve wide 3 dB ARBW. Measured results of the fabricated prototype exhibit 3 dB ARBW of 226° with ARmin of 0.52 dB and 198° with ARmin of 1.61 dB in two principal planes at $\boldsymbol{\varphi } = \text{0}^\circ $ and $\boldsymbol{\varphi } = \text{90}^\circ $ , respectively. The antenna offers impedance bandwidth of 85 MHz (2.448–2.533 GHz) and CP bandwidth (CPBW) of 23 MHz (2.474–2.497 GHz). The minimum peak gain is 3.87 dBic in the broadside direction. [ABSTRACT FROM AUTHOR]

A tri‐port compact antenna loaded on hybrid metasurface (MS) with gain enhancement and pattern diversity is proposed in this article. The antenna consists of three analytically designed contorted radiators (Ant‐1, Ant‐2, and Ant‐3). A koch‐fed fractal aperture ground plane is used to improve impedance matching and port isolation, thus eliminating supplementary decoupling networks. Ant‐1 is 45° tilted, operating in wideband mode. Ant‐2 is one‐fourth, Ant‐3 is one‐half in electrical lengths with L‐shaped metallic contortions to achieve good matching characteristics and asserts pattern diversity. A hybrid MS (combination of conventional customized MS's) structure is loaded for gain enhancement of ≈ 8.93 dBi. Ant‐1 operates at (4.97‐10.63) GHz with 72.56% frequency bandwidth (FBW), Ant‐2 operates at (8.5‐10.4) GHz with 20.1% (FBW) and Ant‐3 operates at (7.2‐9.6) GHz with 28.57% (FBW). The differentiation in antenna electrical size assists compactness, reduction in mutual coupling (>17 dB), has uncorrelated radiation patterns at each port delivering far‐field diversity with low ECC < 0.1. A prototype antenna of size 28.6 mm × 28.6 mm is fabricated and experimented, which are in good agreements with EM simulation and equivalent circuit model response. The proposed tri‐port antenna can be a promising candidate for MIMO diversity applications. [ABSTRACT FROM AUTHOR]

The potential advantages of simultaneous wireless information and power transfer (SWIPT) applications have necessitated innovations in the associated circuits and systems. This article, therefore, explores the concept of cascaded resonators, for the first time, in the design of a compact‐size defected ground structure (DGS)‐based tri‐band wireless power transfer (WPT) system to advance the SWIPT technology. The design is augmented with a systematic design procedure that is preceded by the development of a new double‐elliptic DGS‐based tri‐band resonator. Initially, the analysis of the proposed resonator is performed to identify the impact of defect size on the bandwidth. Subsequently, the resonators are cascaded to achieve a tri‐band functionality and then utilized in the design of WPT. The designed WPT operates at 0.3, 0.5, and 0.9 GHz, and takes a compact size of 39 × 13 mm2. The measurement of the realized WPT with the transmitter and receiver, separated by the distance of 10 mm, provides an efficiency of around 60% at all three bands with the figure of merit values of about 0.5. Furthermore, the proposed design achieves a bandwidth of more than 3 MHz bandwidth at the frequencies corresponding to communication standards. [ABSTRACT FROM AUTHOR]

In this article, a novel dual-band multi-port compact rectenna design for RF energy harvesting is proposed. An E-shaped coaxial fed microstrip antenna combined with an inverted Lshaped structure is used to achieve a dual-band operation at 0.9 GHz (GSM900) and 2.4 GHz (WiFi) frequency bands with gains of 0.8 dBi and 4.4 dBi, respectively. A shorting post is incorporated in the design, which restricts the antenna size to 50mm × 47 mm, making the overall rectenna compatible with any sensor nodes. Further, a compact rectifier circuit covering both the frequency bands is designed to obtain a conversion efficiency up to 50% for an input power as low as -20 dBm. The matching circuit ensures that the nonlinear impedance of the rectifier matches with that of the antenna under varying operating conditions. Finally, the rectennas designed are combined and arranged together to form a cubical structure to produce an output voltage as large as 0.5V for an input power of -20 dBm. With 360? coverage and orthogonal polarization reception, the cubical antenna arrangement ensures improved harvesting efficiency making the proposed design suitable for powering low power IoT devices. [ABSTRACT FROM AUTHOR]

A compact composite right/left-handed (CRLH)-based dualband rectenna is proposed for electromagnetic (EM) energy harvesting at the operating frequencies of Wi-Fi (2.5 GHz) and Worldwide Interoperability for Microwave Access (WiMAX) (3.6 GHz) bands. The rectenna consists of a dual-band antenna and dual-band rectifier. The antenna is realized in a microstrip topology using a balanced CRLH transmission line (TL) with an open termination. It measures 0.36 # 0.2 # 0.00049 mo (mo is the free-space guided wavelength) at 2.5 GHz and operates at 2.5 and 3.6 GHz, with an operating bandwidth of 4.75 and 3.3%, respectively, and a peak gain of 2.6 decibels relative to isotropic (dBi) at 2.5 GHz and 1.6 dBi at 3.6 GHz. The dual-band rectifier is designed using a novel CRLH-based microstrip topology composed of microstrip lines and lumped components. The overall rectifier volume is 0.3 # 0.2 # 0.0005 mo at 2.5 GHz. The measured radio-frequency (RF)?dc conversion efficiency is more than 59% at 2.5 GHz and 41% at 3.6 GHz, for an input power of 2 dB milliwatts (dBm) in both cases. [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. [ABSTRACT FROM AUTHOR]

A novel, fast, and accurate analytical method based on input impedance is proposed for antenna directivity determination. The detailed theoretical expressions are examined and presented to determine the directivity of the wire-dipole and biconical antennas. The proposed analytical directivity results of the antennas are compared with conventional methods and measurements as well as a commercial electromagnetic (EM) simulator. A good correlation is achieved between the proposed method, the CST full-wave EM simulator, and the measurements. Additionally, the proposed method can be used to determine the antenna directivity in complicated environments, i.e., large array, for which the antenna characteristics may be deviated under coupling effects. [ABSTRACT FROM AUTHOR]

A wideband and high gain dielectric resonator antenna (DRA) operating in hybrid HEM11δ mode is proposed. The investigated geometry employs one cylindrical dielectric resonator partially covered with a transparent dielectric superstrate and backed up by a single side metal coated dielectric reflector plane. The reflector is dedicated for gain enhancement while the superstrate is employed for merging of two resonant bands resulting in a single wide band. The dielectric resonator is excited by simple microstrip feed slot coupling technique and operates over X-band, ranging from 7.12 GHz to 8.29 GHz, that is, of 15.18% impedance matching bandwidth with 11.34 dBi peak gain. The different development stages like standalone DRA, DRA with superstrate, DRA with reflector, and DRA with both superstrate and reflector plane with respect to bandwidth and gain performances are analyzed properly. To the best of authors’ knowledge, this is the first time this type of combination of both superstrate and reflector plane is demonstrated in DRA engineering. An antenna prototype was fabricated and characterized and a very good agreement is achieved between the simulated and measured results. [ABSTRACT FROM AUTHOR]

We propose a compact planar passband frequency selective surface (FSS) operating at the resonance frequency of 3.81 GHz. The proposed FSS is composed of single layer of the Archimedean spiral type with the interdigital capacitance between the corners of metallic patches printed on one side of the substrate. Compared to the operating wavelength, the size of the proposed single layer FSS is 0.066λ0 (λ0 is the free space wavelength at 3.81 GHz). The performance such as transmission and reflection coefficient of the proposed FSS demonstrates excellent resonance stability for different polarization and different incident angles. Finally, the optimized simulated results are validated with measured results by a fabricated prototype of 31×31 array elements on 170×170 mm2 substrate area. [ABSTRACT FROM AUTHOR]

A composite right/left-handed (CRLH) structure-based high-impedance surface (HIS) is investigated to improve gain and front-to-back ratio of planar microstrip antennas. An unbalanced CRLH unit cell with a wide band-stop region from 2.0 to 6.44 GHz is modelled and designed for HIS to enhance the antenna performance. A novel via-less structure composed of an interdigital capacitor and four spiral arms is used for the microstrip implementation of the CRLH unit cell. The HIS is formed by the repetition of the unbalanced CRLH unit cells in two-dimensional form. The microstrip patch antennas operating at three different frequencies: 2.34, 3.77 and 5.64 GHz in the band-stop region of the HIS are designed with and without HIS to compare the antenna performances. An increase in gain of 1.91, 2.03 and 0.7 dB and an improvement in the front-to-back ratio of 4.9, 6.0 and 4.2 dB are achieved for the patch antennas operating at 2.34, 3.77 and 5.64 GHz, respectively. To demonstrate the effectiveness of HIS, a patch antenna over HIS is fabricated and measured results show good correlation with the simulated results. An overall antenna size at 2.26 GHz is 0.378λo × 0.303λo × 0.012λo. [ABSTRACT FROM AUTHOR]

A generalised stubs-integrated-microstrip (SIM) antenna with wide coverage circularly polarised (CP) radiation is proposed for radio-frequency energy harvesting applications. The antenna consists of a microstrip patch radiator with four integrated asymmetric/symmetric-stubs and a coaxial feed. Four stubs are integrated at the corners of a square microstrip radiator. The stub lengths or stub gaps from the microstrip radiator are optimised for wide-beam CP radiation. Four different combinations of asymmetric/symmetric based SIM antennas are designed, fabricated, and tested. The proposed antennas are able to cover upper-half area with CP radiation across the 3-dB axial ratio bandwidth. [ABSTRACT FROM AUTHOR]