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An E-band Cassegrain switched beam high-gain antenna concept for 5G backhauling systems is proposed in this article. The antenna requirements target the compensation of small misalignments (within ±1 degrees in both azimuth and elevation planes) in E-band backhauling links due to adverse weather conditions or thermal deformations. The intended antenna is able to realize beam-switching operations by using a feed-array architecture based on a 7 × 7 array of cavity-backed magnetoelectric (ME) dipoles, where every element is capable of providing a steering of ±0.33 degrees in both the elevation and the azimuth planes. The ME dipole illuminators combined with a Cassegrain reflector provide a gain of 52 dBi within the whole scanning range. Besides, they can be easily integrable with the front-end modules, thus being an easily implementable and low-cost alternative to other more complex solutions based on horns or lens antennas. [ABSTRACT FROM AUTHOR]

Sample size fluctuation and the restriction of measurements that demonstrate kinetics (typical of physiological processes) are two of the largest inferential constraints in studies on embryonic development in vitro. Thus, we hypothesize that a practical and robust way of aggregating knowledge on aspects of embryonic development in vitro is to use measurements based on the binary counting component. These are typically used to measure the germination process (intraeminal embryonal development). Our biological model was Dragon's blood (Croton lechleri Müll Arg.), a species native to the Amazon with great socioeconomic impact. Matrices originating from two populations (one native and another cultivated) were the source of biological material. From this material, we studied five sampling densities (5, 25, 50, and 100 embryos), forming a 2 × 4 factorial ANOVA. Among the measurements studied, the coefficient of variation of time, uncertainty, and the synchronization index were the most sensitive to sample-size fluctuation. The synchronization index, however, also proved to be an interesting measurement to detect the parental effect related to the place of occurrence of the matrices. The embryonic development ability, mean development time, and mean development rate were not affected by fluctuations in the sample size or the origin of the material, demonstrating highly conserved traits of the species. Finally, in general, the measurements based on binary counting demonstrated robustness for modeling embryonic growth. [ABSTRACT FROM AUTHOR]

Sample size fluctuation and the restriction of measurements that demonstrate kinetics (typical of physiological processes) are two of the largest inferential constraints in studies on embryonic development in vitro. Thus, we hypothesize that a practical and robust way of aggregating knowledge on aspects of embryonic development in vitro is to use measurements based on the binary counting component. These are typically used to measure the germination process (intraeminal embryonal development). Our biological model was Dragon’s blood (Croton lechleri Müll Arg.), a species native to the Amazon with great socioeconomic impact. Matrices originating from two populations (one native and another cultivated) were the source of biological material. From this material, we studied five sampling densities (5, 25, 50, and 100 embryos), forming a 2 × 4 factorial ANOVA. Among the measurements studied, the coefficient of variation of time, uncertainty, and the synchronization index were the most sensitive to sample-size fluctuation. The synchronization index, however, also proved to be an interesting measurement to detect the parental effect related to the place of occurrence of the matrices. The embryonic development ability, mean development time, and mean development rate were not affected by fluctuations in the sample size or the origin of the material, demonstrating highly conserved traits of the species. Finally, in general, the measurements based on binary counting demonstrated robustness for modeling embryonic growth.

In this article, we present a simple, low-cost solution for the gain enhancement of a conventional pyramidal horn antenna using additive manufacturing. A flat, metamaterial lens consisting of three-layer metallic grid wire is implemented at the aperture of the horn. The lens is separated into two regions; namely epsilon-positive and epsilon-near-zero (ENZ) regions. The structure of the ENZ region is constructed accounting the variation of relative permittivity in the metamaterial. By the phase compensation property imparted by the metamaterial lens, more focused beams are obtained. The simulated and measured results clearly demonstrate that the metamaterial lens enhances the gain over an ultra-wide frequency band (10–18 GHz) compared to the conventional horn with the same physical size. A simple fabrication process using a 3D printer is introduced, and has been successfully applied. This result represents a remarkable achievement in this field, and may enable a comprehensive solution for satellite and radar systems as a high gain, compact, light-weighted, broadband radiator. [ABSTRACT FROM AUTHOR]

One of the current trends in the integrated circuit (IC) development is the integration of antennas on-chip or in the package of the IC. This poses challenges in the production testing process of the packaged IC, as the antenna functionality has to be included and at least one of the signal ports cannot be accessed at a conducted manner. In order to measure the reflection coefficient of an integrated antenna, a contactless characterization method (CCM) can be used. In this paper, the practicality of a CCM is assessed, having the application of a cost-effective high-volume testing procedure for integrated antennas in mind. It is shown that the CCM yields accurate results for different imperfections in the measurement setup. Moreover, measurement results around 33 GHz using a connectorized patch antenna are shown, which experimentally verify the validity of using the CCM under near-field conditions. [ABSTRACT FROM AUTHOR]

Phase retrieval algorithm is an effective method to reconstruct the surface distortions for reflector antennas. As the traditional Fourier iterative algorithms usually stagnate at local minima, we previously proposed a global phase retrieval algorithm, named CMAES-HIO, based on the hybridization of hybrid-input-output algorithm and covariance matrix adaptation evolution strategy. We address the problem of selection of the Zernike order used in the phase parameterization for CMAES-HIO algorithm in this paper. By introducing a hybrid evaluation parameter, which combines the algorithm accuracy and time consumption, we utilize the Monte-Carlo method to simulate the algorithm performance under different random surface distortions. Simulation results show that for an unknown surface distortion, a Zernike order of 5 or 6 is probably the optimum for the comprehensive algorithm performance with respect to time and accuracy. [ABSTRACT FROM AUTHOR]

A novel 1 × 4 phased array elliptical inverted T-shaped slotted sectored patch antenna with defected ground structure (DGS), resonate at proposed ultra-wide tetra band at 28, 43, 51, and 64 GHz with high gain and beam-steering capabilities is presented. An inverted T-shaped slotted stub is used with the sectored patch to achieve ultra-wideband properties. In order to resonate the antenna at four different bands, DGS of round bracket slot is etched on the ground. The 1 × 4 phased arrays are used at the top edge and bottom edge of mobile PCB with high gain. The simulation results show that the antenna has four ultra-wide bands: 25.8–29.7, 40.6–44.6, 49.2–53.1, and 62.2–74 GHz with a maximum gain of 16.5 dBi at 51 GHz. The phased array antenna is capable to steer its main beam within ±30° at the 26, 28, and 43 GHz, using appropriate phase shifts of each antenna element. The proposed millimeter wave antenna is particularly suitable for cellular infrastructures and can be a candidate for emerging 5G mobile applications. The availability of an additional 11.8 GHz (62.2–74 GHz) of contiguous unlicensed spectrum will allow the launching of new exciting wireless services. [ABSTRACT FROM AUTHOR]

This paper deals with a near-field to far-field transformation able to predict the radiation of UHF antennas located over a lossy ground. From in-situ near-field measurements, an equivalent set of dipole sources is obtained as a model of the characterized antenna. The paper details the main steps of the transformation and describes the specific experimental set-up designed for the application. Simple directional antennas (monopoles array) as well as more complex omnidirectional antennas (like a biconical antenna as a scaled-down model of a HF antenna) have been tested in realistic environments. This approach is very efficient for separating the contributions of the radiated waves: the sky wave and the surface wave. [ABSTRACT FROM AUTHOR]

The paper describes the design and development of a low profile wide scanned conformal active 1 × 32 phased array antenna for Ku-band SATCOM applications. The realized antenna is diagonally polarized and covers full transmit frequency band (i.e. 13.75–14.5 GHz) of Ku band SATCOM. All the developed sub-systems of the antenna, i.e. conformal radiating array, conformal transmit module, manifold network, and beam steering unit are described. The VSWR of the antenna is better than 1.65 over the complete transmit frequency band. The antenna has the beam steering capability of ±60° in the array plane. Designed antenna is best suited for airborne applications, where antenna profile contributes considerable aero drag and RCS to the host platform. [ABSTRACT FROM AUTHOR]

In this paper, the patch-type frequency selective surfaces (FSS) based on substrate-integrated waveguide (SIW) technology is proposed to improve the bandwidth (BW) and angular performance. The proposed FSS configuration overcomes the limitations of both conventional 2D and 3D FSS structures. A closely coupled cascaded mechanism is employed to combine two identical FSS elements separated by thin dielectric substrate results in incorporation of SIW technology; hence, named as 2.5D FSS. A derived equivalent circuit model is used to estimate the basic performance of proposed FSS–SIW elements, and the response of analytical expressions has been validated and final design is obtained using full-wave simulations. Two basic FSS elements viz. single square loop and a Jerusalem cross have been investigated to prove the enhancement in their BW and angular stability. The proposed technique evidently improves the BW and angular stability of FSS structures than in its established form. Besides, various important parameters that influence the performance characteristics of reported 2.5D FSSs are also studied. The important observations made on the thickness, as the thickness increases the bandstop FSS, can change to bandpass FSS. Finally, the proposed FSS structure has been fabricated and measured using free space measurement setup, to show the effectiveness of theoretical results. The measured results show good agreement with simulated results at normal and oblique incidence angle. [ABSTRACT FROM AUTHOR]

The measurement accuracy of low-frequency narrow-band antenna is heavily influenced by its environment, which is also difficult to remove the clutter with a time gating. This paper proposes a method to improve the measurement accuracy of low-frequency narrow-band antenna using signal processing technique. The method is to predict the unknown value out of received original signal with an auto-regressive model (AR model) based on modern spectral estimation theory, and the parameters in AR model are calculated by maximum entropy spectral estimation algorithm. Thus, a wideband signal compared with the original band is obtained, and then the time-domain resolution is enhanced. The time gating is more exactly to separate the antenna radiation signal from multipath signals. The simulation and experimental results show that about 50% extended data for each ends of original band can be obtained after spectral extrapolation, and the time-domain resolution after extrapolation is twice than the original narrow-band signal, and the influence of measurement environment can be eliminated effectively. The method can be used to improve accuracy in actual antenna measurement. [ABSTRACT FROM AUTHOR]

A planar inverted F-Antenna with the dual band-dual polarization property is presented for medical body area networks applications. The designed antenna covers the 2.45 GHz industrial, scientific and medical, 4 G long term evolution (2.5–2.69 GHz) bands for ON body communication and Wi-Fi and WLAN (3.5–3.6 GHz) bands for OFF body communication. At the lower band, an equivalent offset fed magnetic microstrip type dipole has been utilized that generate field parallel to the surface of the body for supporting ON body communication. The broadside radiation pattern has been realized using the slotted patch counterpart for supporting OFF body communication. This technique has resulted in a design of dual band dual mode property using a single radiator. The footprint of the antenna is only 0.35λg × 0.17λg × 0.08λg. Owing to its compactness, lightweight, and easy mountable property (due to foam substrate), the proposed antenna is found to be robust for MBAN applications. The maximum permissible transmitted power for the 1st band is 25.78 and 20.3 dBm for the 2nd one to maintain standard specific absorption rate limitations of 1.6 W/Kg. Experimental investigations over human body showed minimal deviations from the free space conditions which makes it a potential candidate for body-centric communications. [ABSTRACT FROM AUTHOR]

Frequency- and time-domain characteristics as well as indoor propagation channel impulse response of a compact dual band-notched ultra-wideband (UWB) slot antenna are investigated in this paper. The antenna consists of a narrow rectangular radiation patch and a rectangular wide slot in the modified ground plane. A pair of L -shaped stubs are connected to the radiation patch to obtain band-notched property in WLAN band and a narrow straight stub is placed on the back side of the substrate to create band-notched characteristics in X-band downlink satellite communication system. Moreover, two small parasitic strips are added to the radiation patch to enhance the bandwidth (BW) of the antenna up to 14 GHz. A comprehensive study on time-domain and indoor propagation channel characteristics of the proposed antenna is also presented throughout the paper. A ray-tracing approach based on geometrical optics is applied to analyze the indoor channel characteristics. The designed antenna not only has a wide BW and compact size but also has appropriate radiation and time-domain characteristics over the antenna operating BW. The measured and simulated results are in good agreement. These advantages make the proposed antenna as a desirable option for UWB impulse radio applications. [ABSTRACT FROM AUTHOR]

This paper aims at investigating the dependence of the impedance and the radiation characteristics of a cylindrical dielectric resonator antenna (DRA), on the feed point of the DRA. It is demonstrated that the resonant frequency, bandwidth, radiation pattern symmetry, and cross-polarized radiation levels depend highly on the feed point. Three standard single-ended feed mechanisms such as the microstrip line, the microstrip slot, and the coaxial probe are taken as examples, to demonstrate the feed-point dependence of the DRA performance. Standard commercial EM simulation tools (ANSYS HFSS and CST Microwave Studio) are used for generating insightful results to help the discussion. This analysis also provides a functional comparison among the above said three feed mechanisms with respect to the feed-point dependence, which is further verified through measurements of DRA prototypes employing the three feeds. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel dual-band wearable compact flexible antenna for body-centric wireless communications (BCWCs). The design is based on a modified planar dipole with parasitic elements, meandered lines, and a rectangular reflector embedded into a hydrophobic rubber-textile multilayer substrate in order to get both good antenna performance and mechanical properties. The antenna's structure is analyzed and optimized in free space (FS), on a numerical and an experimental homogeneous flat phantom. The overall dimensions of the antenna are 50 mm × 40 mm × 4.6 mm and a prototype mass of 11 g, which makes it suitable for practical applications in BCWCs. The built prototype resonated at 2.47 GHz with a | S 11|−26.90 dB and at 5.42 GHz with a | S 11|−24.60 dB in the FS. The measured bandwidths are 500 MHz (2.2–2.7 GHz) and 1000 MHz (4.65–5.75 GHz) at lower and higher bands, respectively. The antenna exhibits a measured maximum gain of 1.17 dBi at 2.66 GHz and a radiation efficiency of 28.44% in FS. The 10 g average maximum specific absorption rate is 0.165 W/kg at 2.70 GHz and 0.520 W/kg at 5.24 GHz when the antenna is placed on the numerical phantom at net input power 0.1 W. [ABSTRACT FROM AUTHOR]

A coplanar waveguide slot antenna is herein presented. A rectangular slot is excited by a Y-shaped monopole etched on a single FR4 substrate. This structure exhibits two resonances due to the presence of the slot and the central monopole which can be used to design a dual-band or a wideband antenna. A parametric analysis is presented to describe the impedance matching mechanism for the two impedance bandwidths (BWs), as well as for the wideband antenna. The latter is fabricated and provides a measured impedance BW from 2.28 to 3.6 GHz, and gain larger than 2 dBi, yielding an outstanding BW/size trade-off. Finally, a 60 mm × 60 mm back metallic reflector is used to achieve a directive antenna with 6 dBi of measured gain, and an impedance BW from 2.16 to 3.59 GHz. [ABSTRACT FROM AUTHOR]

In this work, an UWB/narrow band reconfigurable elliptical-shaped monopole antenna for cognitive radio applications with sequential perception and operation modes is presented. The proposed approach consists in integrating a reconfigurable filter, in an UWB antenna ground plan, by the mean of four horizontal slots and integrated switches that allow inserting/removing/varying zeros and poles in the frequency response. By acting on the slot lengths in order to alter their resonance frequencies, the different switch configurations allow the antenna to switch between an UWB mode that could be used for the perception (sensing) and different narrowband modes, mono-band and dual-band, that could be used for the operation at 2.4 or/and 3.5 GHz. To validate the concept, an experimental prototype has been fabricated and a good agreement between the simulated and the measured S -parameters has been obtained. While the presented work uses the presence/absence of a perfect conductive strip (PEC) to model real switch operation, it is believed that the obtained results conjugated with previous work using real switches on a very similar structure allows validating approach. [ABSTRACT FROM AUTHOR]

In recent years, millimeter wave (MMW) has received tremendous interest among researchers, which offers systems with high data rate communication, portability, and finer resolution. The design of the antenna at MMWs is challenging as it suffers from fabrication and measurement complexities due to associated smaller dimensions. Current state-of-the-art MMW dual-band antenna techniques demand high precision fabrication, which increases the overall cost of the system. Henceforth, the design of an MMW antenna with fabrication and measurement simplicity is quite challenging. In this paper, a simple coplanar waveguide (CPW) fed single-band MMW antenna operating at 94 GHz (W band) and a dual-band MMW antenna operating concurrently at 60 GHz (V band) and 86 GHz (E band) have been designed, fabricated, and measured. A 50 Ω CPW-to-microstrip transition has also been designed to facilitate probe measurement compatibility and to provide proper feeding to the antenna. The fabricated single frequency 94 GHz antenna shows a fractional bandwidth of 11.2% and E -plane (H -plane) gain 6.17 dBi (6.2 dBi). Furthermore, the designed MMW dual-band antenna shows fractional bandwidth: 2/6.4%, and E -plane (H -plane) gain: 7.29 dBi (7.36 dBi)/8.73 dBi (8.68 dBi) at 60/86 GHz, respectively. The proposed antenna provides a simple and cost-effective solution for different MMW applications. [ABSTRACT FROM AUTHOR]

The next generation of wireless networks (5G) employs directional transmission at millimeter wave (mmW) frequencies to provide higher bandwidth and faster data rates. This is achieved by applying antenna arrays with proper beam steering capabilities. Rotman lens has long been used as a lens-based beamformer in electronically scanned arrays and its efficient design is important in the overall performance of the array. Minimizing the phase error on the aperture of the antenna array is an important design criterion in the lens. In this paper, a 7 × 8 wideband Rotman lens is designed. Particle swarm optimization is applied to minimize the path length error and thereby the phase error. The optimized lens operates from 25 to 31 GHz, which covers the frequency bands proposed by the Federal Communications Commission for 5G communications. The proposed optimized lens shows a maximum phase error of <0.1°. The proposed Rotman lens is a good candidate to be integrated with wideband microstrip patch antenna arrays that are suitable for 5G mmW applications. [ABSTRACT FROM AUTHOR]

In this study, a new microstrip patch antenna with wideband radar cross-section (RCS) reduction is presented. The RCS of the proposed antenna was reduced by subtracting the current-direction slots of the patch, with the radiation performance sustained not only for the current-direction subtraction, but also for the no modification in the ground plane. Modified and reference antenna were fabricated and measured. The simulation and measurement results showed that the modified antenna reduced the in-band and out-band RCS simultaneously with no detriment to the radiation performance. In the frequency band from 3.9 to 8.1 GHz, the RCS of the modified antenna was reduced in the whole band compared with the RCS of the reference antenna. The maximum RCS reduction was 7 dB at a frequency of 6.7 GHz. [ABSTRACT FROM AUTHOR]

A compact and planar broadband circularly polarized (CP) eighth-mode substrate integrated waveguide (EMSIW) antenna is proposed in this paper. An isosceles right triangular waveguide with one electric sidewall (located on one of its catheti) and two magnetic sidewalls (located on the other two edges of the triangle) is presented to investigate the characteristics of the EMSIW. The closed-form mode solutions of the electromagnetic field components and the cut-off frequencies are derived for all propagating modes in this triangular waveguide. The simulated electromagnetic field distribution is consistent with the analytical results. The resonant frequencies of the EMSIW cavity are then determined. A CP antenna consisting of four EMSIW elements is designed, fabricated, and measured. The measured 3-dB axial ratio bandwidth of the antenna is 21.6% from 4.72 to 5.86 GHz. Within this frequency range, the measured reflection coefficient is below −10 dB, and the measured peak gain in circular polarization at broadside is 6.89 dBic at 5.1 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a technique to increase the bandwidth in substrate integrated waveguide (SIW) cavity-backed antennas, inspired by the design of cavity filters. The proposed structure consists of a slot antenna backed by two cavities, located one on top of the other and coupled through a slot. To demonstrate the bandwidth increase, a standard cavity-backed SIW antenna, with a rectangular slot etched in the top metal plane, has been designed, manufactured, and measured. Subsequently, a similar antenna was developed, by doubling the substrate thickness with the aim to improve the bandwidth. Finally, the new topology of two-cavity SIW antenna has been implemented and compared with the two previous ones. Simulation and experimental results show that the proposed two-cavity antenna exhibits a bandwidth twice as large as the standard SIW cavity-backed antenna. [ABSTRACT FROM AUTHOR]

A simple closed-form analytical formula is proposed to compute the probe reactance of an equilateral triangular patch antenna. The variation of the probe reactance with the variation of antenna dimension, substrate electrical parameters, and probe location is examined thoroughly. The computed values employing the present model show excellent agreement with experimental and simulation results. [ABSTRACT FROM AUTHOR]

In this paper, the resonant frequencies, quality factors and bandwidths of high T c superconducting circular microstrip patches in the presence of a dielectric superstrate loading have been studied using Galerkin testing procedure in the Hankel transform domain. The exact Green's function of the grounded dielectric slab is used to derive an electric field integral equation for the unknown current distribution on the circular disc. Thus, surface waves, as well as space wave radiation, are included in the formulation. London's equations and the two-fluid model of Gorter and Casimir are used in the calculation of the complex surface impedance of the superconducting circular disc. Galerkin testing is used in the resolution of the electric field integral equation. Two solutions using two different basis sets to expand the unknown disk currents are developed. The first set of basis functions used is the complete set of transverse magnetic and transverse electric modes of a cylindrical cavity with magnetic side walls. The second set of basis functions used employ Chebyshev polynomials and enforce the current edge condition. The computed values for a wide range of variations of superstrate thickness and dielectric constant are compared with different theoretical and experimental values available in the open literature, showing close agreement. Results are showing that the superstrate parameters should always be kept into account in the design stage of the superconducting microstrip resonators. [ABSTRACT FROM AUTHOR]

This manuscript deals with the development of a novel configuration of a wide-band single-layer frequency selective surface (FSS) for wide-band rejection applications. The established unit cell is composed of a simple circular ring on the top side of the substrate and a combined conductive element on the backside. Such an inclusion of conductive elements and accurate tuning of their dimensions ends in the rejection of a wide frequency band extended from 6.3 to 16.3 GHz. Moreover, the proposed structure exhibits a stable response against different angles of incidence for both TE and TM polarizations. Detailed simulation and measurement studies are carried out to investigate the performance of the proposed FSS. The obtained results are discussed in depth. [ABSTRACT FROM AUTHOR]

A novel wideband circularly polarized printed antenna is proposed in this paper. It consists of asymmetrical ground and monofilar spiral stubs connecting to it. By employing an inverted L-shaped microstrip feedline to excite the slit etched in the ground and spiral stubs, a wideband culalry polarized performance of the proposed antenna is realized. After optimization, the measured results of the final structure demonstrate that a 10 dB bandwidth of 76.2% from 2.6 to 5.8 GHz and a 3 dB axial-ratio bandwidth for circular polarization of 72.9% from 2.7 to 5.8 GHz could be achieved which could completely cover the Wimax (3.3–3.8 GHz) band. [ABSTRACT FROM AUTHOR]

In this paper, a new miniaturized frequency agile filter-antenna with a wide reconfigurable frequency band is proposed for interweave cognitive radios (CRs). A tunable bandpass filter (BPF) composed of a symmetrical ring resonator is cascaded to the feed line of an ultra-wideband planar antenna. The structure of the proposed ring resonator BPF is simple and compact so that the total size of the proposed filter-antenna is smaller than that of a conventional system made of a separate antenna and BPF. The reconfigurability of the proposed filter-antenna is achieved by changing the operating frequency of the BPF by loading the ring resonator with a single varactor diode at its center. The fabricated prototype has successfully achieved a wide operational bandwidth of 1.43 GHz which covers continuous narrow bands from 4.65 to 6.08 GHz. Moreover, the operating tunable narrow bands have stable radiation characteristics. Good agreement between measurement and simulation results is demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, a high gain broadband low profile microstrip antenna with the dual-layered substrate and four parasitic metal elements is presented. The proposed microstrip antenna is mainly composed of four parts: four circular parasitic metal patches with dual arced breaches, a rectangular metal patch sandwiched between substrates, a square ground plane, and two-square substrates. The circular parasitic elements are the main radiation structure and determine the characteristics of the proposed antenna are closely related to the parasitic elements. The proposed antenna has been fabricated for experimental measurement. The reflection coefficient, radiation pattern, radiation efficiency, and gain have been studied in detail. The simulated and measured impedance bandwidth is 27.0% (3.30–4.33 GHz), the maximum realized peak gain reaches up to 6.52 dBi at the frequency of 3.65 GHz. The radiation pattern has a single peak which is perpendicular to the surface of the substrate. The proposed antenna is suitable to be applied in the 5G mobile or WiMAX wireless communication. Dual antenna with a pair of parasitic elements has been investigated numerically to explain the principle of the proposed antenna. [ABSTRACT FROM AUTHOR]

An integrated reconfigurable antenna capable of spectrum sensing along with various reconfiguration features such as polarization, frequency, bandwidth, and radiation pattern is proposed here. The proposed antenna senses the spectrum by UWB antenna from 2 to 11 GHz to identify the spectrum conditions. After identifying the direction of maximum traffic or interference, the proposed antenna accordingly reconfigures its radiation pattern in order to mitigate the interference using switchable shorting posts. The antenna can reconfigure its polarization state using a switchable slot in the circular antenna. Frequency reconfigurability is obtained by using a varactor diode from 2 to 4 GHz. The antenna can reconfigure its bandwidth from UWB to NB by switching the active ports state. Measured and simulated results of the proposed antenna shows very good agreement, hence, validating the proposed design. [ABSTRACT FROM AUTHOR]

Millimeter-wave (mm-wave) beam-steering antennas are preferred for reducing the disruptive effects, such as those caused by high atmospheric debilitation in wireless communications systems. In this work, a compact broadband antenna array with a low loss feed network design is introduced. To overcome the short-range effects on mm-wave frequencies, a feed network – with a modified Butler matrix and a compact zeroth-order resonance antenna element – has been designed. Furthermore, the aperture feed technique has been utilized to provide a broadside stable pattern and improve the delivered gain. A Fabry-Perot layer without the height of the air layer is used. Taking advantage of this novel design, a broadband and compact beam-steering array antenna – capable of covering impedance bandwidths (from 33.84 to 36.59 GHz) and scanning a solid angle of about ~94°, with a peak gain of 17.6 dBi – is attained. [ABSTRACT FROM AUTHOR]

A compact printed quadrant shaped monopole antenna is introduced in this paper as a good prospect for ultra wideband- multiple-input multiple-output (UWB-MIMO) system. The proposed MIMO antenna comprises two perpendicularly oriented monopoles to employ polarization diversity. An open circuit folded stub is extended from the ground plane of each radiating element to enhance the impedance bandwidth satisfying the UWB criteria. Two ‘L’ shaped slots are further etched on the radiator to provide good isolation performance between two radiators. The desirable radiator performances and diversity performances are ensured by simulation and/or measurement of the reflection coefficient, radiation pattern, realized peak gain, envelope correlation coefficient (ECC), diversity gain, mean effective gain (MEG) ratio and channel capacity loss (CCL). Results indicate that the proposed antenna exhibits 2.9–11 GHz 10 dB return loss bandwidth, mutual coupling <−20 dB, ECC < 0.003, MEG ratio ≈ 1, and CCL < 0.038 Bpsec/Hz, making it a good candidate for UWB and MIMO diversity application. [ABSTRACT FROM AUTHOR]

A novel radio frequency identification antenna based on log-periodic dipole array (LPDA) antenna at 5.8 GHz is presented. The antenna design approach consists of two major steps. Firstly, the conventional primitive method is used to design a traditional LPDA antenna. The antenna structure is then miniaturized and its overall performance significantly improved. Dynamic scaling factor along with uniformly separated elements are introduced in this class of antenna, resulting in a 51.5% length reduction. To improve front-to-back (F/B) ratio a symmetrical folding technique is employed, leading to 21.5 dB F/B ratio for the fabricated prototype. An excellent level of input impedance matching (S11 = −28 dB) is achieved using a well-designed feeding system through a proximity coupling technique. The measured gain of the fabricated prototype is 6.2 dBi, and the overall dimension of the antenna substrate is only 30 × 45 mm2 (0.58λ0 × 0.87λ0). [ABSTRACT FROM AUTHOR]

This article presents a compact novel quasi-self-complementary semi-octagonal-shaped antenna for ultra-wideband (UWB) application. The proposed novel structure is fed by a microstrip line where different rectangular truncation is etched to the ground plane as an impedance matching element, which results for much wider impedance bandwidth (VSWR<2) from 2.9 to 20 GHz. In order to obtain band-notched characteristics at 5.5 GHz, an open-ended, quarter wavelength, spiral-shaped stub is introduced in the vicinity of the truncated part of the ground plane. An equivalent circuit model is adopted to investigate the band rejection characteristics of the ground plane stub. Sharpness of the rejection band can be controlled by maintaining the gap between stub resonator and the slotted periphery of ground plane. The proposed antenna design is validated by experimental measurements. [ABSTRACT FROM AUTHOR]

Compact broadband circularly polarized elliptical slot antenna arrays (CPESAAs) are devised based on 2 × 2 and 4 × 4 circularly polarized (CP) elliptical slot antennas and a sequential phase feed network. To realize the circular polarization, eight rectangular stubs are embedded in the feed structure to excite two orthogonal E vectors in 2 × 2 CPESAA configuration. Moreover, by taking four rectangular slots out from each array element, return loss and axial-ratio bandwidths are noticeably increased. The investigated simple array element has a compact size of 20 × 20 × 1 mm3. As well, 2 × 2 CPESAA occupies a compact size of 55 × 60 × 1 mm3, which operates within the frequency band 4.18–9.35 GHz. Thus, 76.4% of S11 < −10 dB and 51.4% of CP bandwidth (4.43–7.5 GHz) are covered. Moreover, proposed 4 × 4 CPESAA is printed on 110 × 110 × 1 mm3 FR4 substrate and covers the frequency band of 1.15–12.98 GHz with CP at 2.95–8.82 GHz. Throughout the study, the design process of the proposed antenna arrays are presented and discussed in detail. [ABSTRACT FROM AUTHOR]

This paper presents a procedure for the design of tensorial metasurface antennas radiating polarized beams through aperture field synthesis. The aperture field is generated using the surface wave to leaky wave conversion resulting from metasurface modulation. The design procedure of the feeder is presented with a description of the geometrical parameters affecting the antenna matching. Numerical solutions for single beam and multi-beam metasurface antennas working respectively, at 12.25 and 20 GHz are presented. In addition, a metasurface prototype working at 12.25 GHz is manufactured and measured. [ABSTRACT FROM AUTHOR]

An optically transparent and electrically small frequency modulation (FM) radio receiving antenna has been designed and fabricated from a mesh silver layer printed onto a glass substrate. The studied FM antenna consists of a transparent meandering monopole associated with a micrometric size MEtal Semiconductor Field Effect transistor. An optical transparency of 87% and a sheet resistance lower than 0.22 Ω/sq are obtained. The received signal strength indicator and the signal-to-noise ratio are both measured and compared with those of a commercial monopole antenna (a quarter-wave wire antenna). The transparent FM antenna exhibits similar radiofrequency performance with, in addition, a low visual impact. [ABSTRACT FROM AUTHOR]

A novel topology of high-gain millimeter-wave antenna compatible with substrate integration is presented. The antenna is composed of a planar discrete lens laid on top of a core dielectric, while the planar focal source is assembled on the bottom side. The antenna can be fabricated as a single, robust and compact module using standard low-cost PCB technologies, and is compatible with IC integration such as a transceiver circuit for fully integrated millimeter-wave front-end modules. The proposed architecture is studied with two compact V-band antennas (32 mm × 32 mm × 13.2 mm). The main design rules are demonstrated for unit cells, focal source, and planar lens at V-band. Promising performances in terms of gain (17.6 and 20.4 dBi), aperture efficiency (14 and 26%), and fractional 3-dB gain bandwidth (17 and 18%) are obtained experimentally for the two considered compact antennas. [ABSTRACT FROM AUTHOR]

This paper presents a broadband hybrid slot-dielectric resonator antenna for radiofrequency (RF) energy-harvesting application. The antenna geometry consists of a simple pentagon-shaped dielectric resonator antenna (PDRA) excited by a microstrip feed underlying rectangular slot with narrow notch. It is investigated that the bandwidth of the proposed PDRA is improved significantly owing to electromagnetic coupling between feeding slot and the dielectric resonator. The measured results demonstrate that the proposed PDRA achieves an impedance bandwidth of 110.8%, covering the frequency range from 0.86 to 3 GHz in addition of stable radiation pattern with peak gain of 6.8 dBi and more than 90% radiation efficiency throughout the band, showing its suitability for RF energy harvesting application. For this to be feasible, the developed antenna is matched with the rectifier at two public telecommunication bands of GSM-900 and GSM-1800 using a compact dual-band hybrid matching network. The measured result demonstrates that the proposed dual-band rectenna system provides the peak efficiency of 63 and 59% for a load impedance of 4.7 kΩ at 0.9 and 1.8 GHz, respectively. [ABSTRACT FROM AUTHOR]

By using a metasurface (MS) structure, a linearly polarized wave is converted to circularly polarized waves. Both right- and left-handed circular polarizations (RHCPs and LHCP) are obtained by a simple configuration in the proposed structure which consists of 16 unit cells arranged in a 4 × 4 layout. Each unit cell contains five horizontal and parallel strips embedded in a rectangular frame in which a single diagonal strip is placed from one corner to the opposed one. It is shown that the orientation of the diagonal line determines the handedness of the converted signal to be either LHCP or RHCP. In order to show the working conditions of the MS structure, scattering parameters are found for both co-polarized and cross-polarized responses. Axial ratio, an indicator for polarization conversion, is then obtained by dividing cross-polar response to co-polar response to demonstrate the transformation. The structure works for horizontally and vertically polarized linear waves in a wide band frequency range which is approximately 510 MHz. Since the suggested MS model is composed of a simple geometry for polarization conversion, it can be easily adjusted in any desired frequency bands for a variety of applications from the defence industry to medical, education, or communication areas. [ABSTRACT FROM AUTHOR]

A novel compact directional antenna with improved gain is proposed for microwave breast imaging (MBI) applications. The radiating fins are modified by etching several slots to make the antenna compact and enhance antenna performance in terms of bandwidth, gain, efficiency, and directivity. Several parameters are studied and optimized to frequency from 3.1 to 6.5 GHz, which is typically used in the breast imaging system. The electrical length of the antenna is 0.39λ × 0.46λ × 0.01l at the lower frequency band. The result shows that the antenna exhibits 210 dB impedance bandwidth of 4.3 GHz (2.7-7 GHz) with directional radiation pattern. The peak gain of the proposed prototype is 7.8 dBi and fractional bandwidth is 92%. The time domain results show that the fidelity factor for face to face is 0.92 and for side by side is 0.62, which prove the directivity and lower distortion of the signal. The proposed prototype is successfully simulated, fabricated, and measured. [ABSTRACT FROM AUTHOR]

This paper proposes a unique, first of its kind fabrication technique for the making of textile antennas. A novel method that provides scope for automation in textile antenna production is presented here. A completely integrated textile antenna fabrication method that eliminates the tasks of positioning and fastening of the various components of a patch antenna is discussed. The technique employs multilayer weaving for the production of a wearable antenna on a cotton substrate. Silver yarn is used for the conductive regions of the textile antenna. Two layers of woven cotton serve to isolate the radiating patch from the ground plane of the antenna. The designed antenna was chosen to operate at the frequency of 2.45 GHz for Wireless Local Area Network. The built prototype resonated at 2.43 GHz with a |S11|of 218.62 dB. The integrated textile antenna exhibited a gain of 1.06 dBi at 2.43 GHz. [ABSTRACT FROM AUTHOR]

Two-dimensional scattering of a Gaussian beam by a homogeneous gyrotropic circular cylinder is presented. The incident Gaussian beam source is expanded as an approximate expression with Taylor's series. The transmitted field in the homogeneous gyrotropic cylinder is expressed in terms of the series of wave functions based on the integral equation. The unknown coefficients of the scattered fields are obtained with the aid of the boundary conditions of continuous tangential electric and magnetic fields. Some numerical results are presented and discussed. The result is in agreement with that available as expected when the Gaussian beam degenerates to a plane wave incidence case. [ABSTRACT FROM AUTHOR]

An axially slotted cylinder coated with two different types of inhomogeneous coating layers is considered. These inhomogeneous coatings have decreasing permittivity profiles. The effects of various parameters of these coatings upon the gain pattern have been investigated using numerical simulations. It is studied that the gain at certain observation angles can be enhanced or diminished by controlling the inhomogeneity parameters of these considered profiles. It is further studied that for specific type of considered inhomogeneous coatings, the forward direction gain can be enhanced significantly. [ABSTRACT FROM AUTHOR]

In through-the-wall radar imaging, multipath propagation can create ghost targets, which can adversely affect the image reconstruction process. However, unlike genuine targets, ghost positions are aspect-dependent, which means their position changes with the transceiver location. This paper proposes efficient ghost suppression methods exploiting aspect dependence feature under compressive sensing framework. This paper proposes a generalized signal model that accommodates for the reflections of the front-wall and target-to-target interactions, making the scheme more practical, yet the knowledge of the location of reflecting geometry is not a requirement as in most of the recent literatures. In addition, the sensing matrix is greatly reduced making the methods more attractive. Moreover, this paper investigates the influence of array configurations by examining two antenna array configurations: multimonostatic, and single-view bistatic configurations. Results based on synthesized data and real experiment show that the proposed method can greatly suppress multipath ghosts and hence increase signal-to-clutter ratio. [ABSTRACT FROM AUTHOR]

The design and integration of penta-band planar antenna with a low noise amplifier (LNA) for vehicular wireless applications is discussed in this research. By integrating antenna with a LNA, the return loss can be kept low with the increased bandwidth compared with a passive antenna with the same design. The performance of the passive antenna, LNA, and integrated active antenna (IAA) are individually validated with the aid of vector network analyzer. The designed IAA covers navigational frequencies 1.2 and 1.5 GHz, wireless communication frequencies 2.4, 3.3 GHz and dedicated short range communication frequency 5.8 GHz, with LNA gain (>10dB) and noise figure (>2dB). The proposed design gives room for simultaneous reception of all the desired frequency bands with better performance for vehicular communications. [ABSTRACT FROM AUTHOR]

A new single-feed aperture-coupled, X-band microstrip patch antenna array with circular polarization (CP) is designed. CP is achieved using indented microstrip patches fed through the slots on a substrate integrated waveguide. The antenna has the high radiation efficiency more than 90% over the operating frequency. Impedance bandwidth (VSWR< 2) and axial ratio bandwidth (AR< 3 dB) of 11.8, and 10.9% is attained, respectively. Good agreement is achieved between simulated and measured results. [ABSTRACT FROM AUTHOR]

Multiple input multiple output (MIMO) antenna is at core of the presently available wireless technologies. The design of MIMO antennas over a limited space requires various approaches of mutual coupling reduction, otherwise gain, efficiency, diversity gain, and radiation patterns will be severely affected. Various techniques have been reported in literature to control this degrading factor and to improve the performance of the MIMO antennas. In this review paper, we have carried out an extensive thorough investigation of diversity and mutual coupling (correlation) reduction techniques in compact MIMO antennas. [ABSTRACT FROM PUBLISHER]

In this paper, a novel design of compact Coplanar Waveguide-fed planar monopole antenna with enhanced bandwidth and multiband characteristics has been proposed. Two rectangular rings have been incorporated in a rectangular patch to obtain multiband operation for Wireless Local Area Network (WLAN) (2.4/5.2/5.8 GHz) and Worldwide Interoperability for Microwave Access (WiMAX) (2.3/2.5/5.5 GHz) bands. A parasitic strip and meandering along with double-ringed structure have been used to achieve enhanced impedance bandwidth in WLAN (from 2.26 to 3.03 GHz) and WiMAX (from 4.48 to 6.85 GHz) bands. The parametric analysis is carried out to study effect of varying dimensions on antenna performance. The proposed antenna is optimized and prototype is designed and fabricated. Simulated and measured radiation patterns in elevation and azimuthal planes are also observed. The antenna shows significant gain of 7.33 dBi at 6.54 GHz frequency. [ABSTRACT FROM PUBLISHER]

A novel transmission line structure has been developed to facilitate the delivery of both adrenaline and microwave energy to achieve hemostasis. A proximal end impedance transformer and radiative tip have been designed and manufactured to provide good match between the novel hollow transmission line and the microwave source and tissue, respectively. Further consideration of the challenges and problems encountered along with evidence of successful microwave energy delivery at 5.8 GHz into porcine liver model providing a controlled and focused coagulation zone of approximately 5 mm. [ABSTRACT FROM PUBLISHER]