Showing papers in "Progress in Electromagnetics Research-pier in 2013"

Wire troubleshooting and diagnosis: review and perspectives

Abstract: Electrical cables of all types are subject to aggressive environments that can create defects or accelerate aging. Many application domains require diagnosis methods and tools. Among many methods, re∞ectometry has proven to be the best candidate and can be easily applied to the detection and localization of hard defects, while only requiring one access point to the wire. But soft defects are more di-cult to track and require new powerful methods. This paper presents a review of the recent state of the art in the fleld of wired network diagnosis and shows the evolution of future activities in this domain. It provides new perspectives and new research domains are proposed.

Silicon Multimode Photonic Integrated Devices For On-Chip Mode-Division-Multiplexed Optical Interconnects

Abstract: Multimode spatial-division multiplexing (SDM) technol- ogy has attracted much attention for its potential to enhance the ca- pacity of an optical-interconnect link with a single wavelength car- rier. For a mode-multiplexed optical-interconnect link, the functional elements are quite difierent from the conventional ones as multiple modes are involved. In this paper we give a review and discussion on multimode photonic integrated devices for mode-multiplexed optical- interconnects. Light propagation and mode conversion in tapered waveguides as well as bent waveguides are discussed flrst. Recent progress on mode converter-(de)multiplexers is then reviewed. The demands of some functional devices used for mode-multiplexed optical- interconnects are also discussed. In particular, the fabrication toler- ance is analyzed in detail for our hybrid demultiplexer, which enables mode-/polarization-division-(de)multiplexing simultaneously.

Brain Mr Image Classification Using Multiscale Geometric Analysis of Ripplet

Abstract: We propose an automatic and accurate technique for classifying normal and abnormal magnetic resonance (MR) images of human brain. Ripplet transform Type-I (RT), an e-cient multiscale geometric analysis (MGA) tool for digital images, is used to represent the salient features of the brain MR images. The dimensionality of the image representative feature vector is reduced by principal component analysis (PCA). A computationally less expensive support vector machine (SVM), called least square-SVM (LS-SVM) is used to classify the brain MR images. Extensive experiments were carried out to evaluate the performance of the proposed system. Two benchmark MR image datasets and a new larger dataset were used in the experiments, consisting 66, 160 and 255 images, respectively. The generalization capability of the proposed technique is enhanced by 5 £ 5 cross validation procedure. For all the datasets used in the experiments, the proposed system shows high classiflcation accuracies (on an average > 99%). Experimental results and performance comparisons with state-of-the-art techniques, show that the proposed scheme is e-cient in brain MR image classiflcation.

Design of a novel super wide band circular-hexagonal fractal antenna

Abstract: In this paper, a novel circular-hexagonal Fractal antenna is investigated for super wide band applications. The proposed antenna is made of iterations of a hexagonal slot inside a circular metallic patch with a transmission line. A partial ground plane and asymmetrical patch toward the substrate are used for designing the antenna to achieve a super wide bandwidth ranging from 2.18GHz to 44.5GHz with a bandwidth ratio of 20:4 : 1. The impedance bandwidth and gain of the proposed antenna are much better than the recently reported super wideband antennas which make it appropriate for many wireless communications systems such as ISM, Wi-Fi, GPS, Bluetooth, WLAN and UWB. Details of the proposed antenna design are presented and discussed.

Isolation Improvement in a Dual-Band Dual-Element MIMO Antenna System Using Capacitively Loaded Loops

Abstract: A dual-band dual-element multiple-input-multiple-output (MIMO) antenna system with enhanced isolation is proposed. The MIMO antenna system is based on printed 4-shaped antenna elements. Dual band isolation is achieved by using an array of printed capacitively loaded loops (CLLs) on the top side of the board for high band isolation improvement and a complementary CLL structure on the GND plane of the antenna for lower band isolation improvement. The lower band of operation covers 827{853MHz and the higher band covers 2.3{ 2.98GHz. Two prototypes were investigated to access the efiect of the isolation mechanism. Measured isolation improvement of 10dB was observed in the lower operating band while the improvement in the higher band was approximately 2.5dB. The isolation improvement was at the expense of 5% reduction in e-ciency. The measured gain patterns as well MIMO flgures of merits such as the correlation factor, TARC and MEG were investigated as well.

Comparison of magnetic-geared permanent- magnet machines

Abstract: With the advent of magnetic gears, researchers have developed a new breed of permanent-magnet machines. These magnetic-geared permanent-magnet machines artfully incorporate the concept of magnetic gearing into the permanent-magnet machines, leading to achieve low-speed high-torque direct-drive operation. In this paper, a quantitative comparison of three viable magnetic-geared permanent-magnet machines is flrstly performed, hence revealing their key features, merits, demerits and applications. Initially, the development of the magnetic gears, including the converted topologies and fleld-modulated topologies, is reviewed. Then, three viable magnetic-geared permanent-magnet machines are identifled and discussed. Consequently, the corresponding performances are analyzed and quantitatively compared. The results and discussions form an important foundation for research in low-speed high-torque direct-drive systems.

Compact EBG Structure for Alleviating Mutual Coupling Between Patch Antenna Array Elements

Abstract: The periodic structure like electromagnetic band gap (EBG) is a hot research topic in the academia and RF-microwave industry due to their extraordinary surface wave suppression property. This study involved in designing a compact uni-planar type EBG structure for a 2.4 GHz resonant frequency band. Double folded bend metallic connecting lines are successfully utilized to realize a low frequency structure while a size reduction of 61% is achieved compared to the theoretically calculated size. From the transmission response, the surface wave band gap (SWBG) is found to be 1.2 GHz (1.91-3.11 GHz) whereas the artificial magnetic conductor (AMC) characteristic is observed at 3.3 GHz. The FEM based EM simulator HFSS is used to characterize the EBG structure. The SWBG property is utilized for alleviation of mutual coupling between elements of a microstrip antenna array. A 2 x 5 EBG lattice is inserted between the E-plane coupled array which reduced the coupling level by 17 dB without any adverse effect on the radiation performances.

A Miniaturized Triple-Band Metamaterial Antenna with Radiation Pattern Selectivity and Polarization Diversity

Abstract: A novel triple-band single-fed compact microstrip antenna with varied polarization states and radiation patterns is proposed based on two-dimensional artiflcial metamaterial transmission line (TL). The TL element is composed of complementary split ring resonators (CSRRs) etched in the ground plane and a capacitive gap embedded in the stepped-impedance conductor line. By inserting a 2 £ 2 array of the original element in conventional patch and feeding the resultant structure with an annular-ring slot along the diagonal, an antenna working in three resonant modes (n = i1, n = 0, and n = +2) is engineered at three speciflc well-separated frequencies fi1 = 1:5, f0 = 2:4 and f+2 = 3:5GHz, respectively. As a result, both the numerical and experimental results illustrate that the antenna exhibits a patch-like radiation with pure linear polarization in the n = i1 mode, a monopolar radiation with circular polarization in the n = 0 and also an asymmetric quasi monopolar radiation with a hybrid linear polarization in the n = +2 mode. The antenna features compact whose patch occupying only an area of 0:246‚0 £ 0:246‚0 £ 0:03‚0 at fi1 and exhibits groups of advantages such as high radiation e-ciency. Moreover, the proposed prescription, free of any metallic via, perturbation structure and complicated feeding network, is of practical value and opens an alternative avenue toward new types of antenna with agile polarization capability and versatile radiation patterns.

A CPW-Fed Dual Band-Notched UWB Antenna with a Pair of Bended Dual-L-Shape Parasitic Branches

Abstract: In this paper, a novel coplanar waveguide (CPW) fed dual band-notched ultra-wideband (UWB) antenna with circular slotted ground is proposed. In order to achieve two notched bands at 3.3{3.7GHz for worldwide interoperability for microwave access (WiMAX) and 5.15{5.825GHz for wireless local area network (WLAN) respectively, a pair of bended dual- L-shape branches are attached to the slotted ground. By optimizing the lengths and positions of the branches, the desired notch-bands of WLAN and WiMAX can be achieved. The prototype of the proposed antenna was fabricated and tested. The simulated and measured results show good agreement over the ultra-wideband. Besides these mechanical features, such as compact in size, easy in fabrication, the proposed antenna also shows good characteristics in its radiation patterns and time-domain behaviors. So it is a nice candidate for modern UWB communication systems.

Compact planar uwb antenna with band notch characteristics for wlan and dsrc

Abstract: In this paper, a compact ultra-wideband microstrip-fed annular ring antenna with band notch characteristics for wireless local area network (WLAN) and dedicated short-range communication (DSRC) is proposed. The proposed antenna comprises an annular ring patch and a partial ground plane with a rectangular slot. The notched frequency band is achieved by etching a partial annular slot in the lower portion of the ring radiator. The centre frequency and bandwidth of the notched band can be controlled by adjusting the width and position of the annular slot. Measured results show that the proposed antenna achieved an impedance bandwidth of 3{10.6GHz with a notched frequency band centred at 5.5GHz. Compared to the recently reported band-notched UWB antennas, the proposed antenna has a simple conflguration to realize the band notch characteristics to mitigate the possible interference between UWB and existing WLAN & DSRC systems. Furthermore, a symmetric radiation patterns, satisfactory gain and good time domain behaviour except at the notched frequency band makes the proposed antenna a suitable candidate for practical UWB applications.

3D Printed Lattices with Spatially Variant Self-Collimation

Abstract: In this work, results are given for controlling waves arbitrarily inside a lattice with spatially variant self-collimation. To demonstrate the concept, an unguided beam was made to flow around a 90◦ bend without scattering due to the bend or the spatial variance. Control of the field was achieved by spatially varying the orientation of the unit cells throughout a self-collimating photonic crystal, but in a manner that almost completely eliminated deformations to the size and shape of the unit cells. The device was all-dielectric, monolithic, and made from an ordinary dielectric with low relative permittivity (er = 2.45). It was manufactured by fused deposition modeling, a form of 3D printing, and its performance confirmed experimentally at around 15 GHz.

Full-vectorial parallel finite-element contrast source inversion method

Abstract: The multiplicatively regularized flnite-element contrast source inversion algorithm (MR-FEM-CSI) is used to solve the full- vectorial three-dimensional (3D) inverse scattering problem The contrast and contrast-source optimization variables are located at the centroids of tetrahedra within the problem domain; whereas the electric fleld is expanded in terms of edge basis functions on the same tetrahedra A dual-mesh is created in order to apply the multiplicative regularization To handle large-scale problems the inversion algorithm is parallelized using the MPI library, with sparse matrix and vector computations supported by PETSc The algorithm is tested using experimental datasets obtained from the Institut Fresnel database A synthetic example shows that the technique is able to successfully image moisture hot-spots within a partially fllled grain bin

Minimum Q for Lossy and Lossless Electrically Small Dipole Antennas

Abstract: General expressions for the quality factor (Q) of antennas are minimized to obtain lower-bound formulas for the Q of electrically small, lossy or lossless, combined electric and magnetic dipole ant ...

Multifrequency monopole antennas by loading metamaterial transmission lines with dual-shunt branch circuit

Abstract: The theory and design of a new family of multifrequency monopole antennas by smartly loading a set of complementary metamaterial transmission line (CMTL) unit cells are investigated The distributed CMTL elements, epsilon negative (ENG) or double negative (DNG) through incorporating additional capacitive gaps, contain a Koch-shaped extended complementary single split ring resonator pair (K-ECSSRRP) etched on the signal strip The K- ECSSRRP features dual-shunt branches in the equivalent circuit model, rendering a distinguished resonator with dual zeroth-order resonant (ZOR) modes By smartly controlling the element layout and loading difierent numbers of unit cells, ten antennas covering difierent communication standards (GSM1800, UMTS, Bluetooth, DMB and WIMAX) are designed and four of them are fabricated and measured At most of operating frequencies, the antennas exhibit impedance matching better than i10dB and normal monopolar radiation patterns Numerical and experimental results both conflrm that the single-cell or dual-cell ENG and DNG CMTL-loaded monopoles exhibit almost identical dual ZOR modes Moreover, the loaded elements also contribute to the radiation, which is the major advantage of this

Four - Band Polarization - Insensitive Metamaterial Absorber Based on Flower - Shaped Structures

Abstract: In this paper, a four-band metamaterial absorber (MA) based on ∞ower-shaped structure is proposed. The design, simulation, fabrication, and measurement of the absorbers working in four bands are presented. Simulation results show that the MA has four distinctive absorption peaks at frequencies 6.69GHz, 7.48GHz, 8.67GHz, and 9.91GHz with the absorptivity of 0.96, 0.99, 0.99 and 0.98, respectively. Experiment results matches well with the simulation. Both experiment and simulation results exhibit that the MA are polarization-insensitive for TE wave and TM wave. The ∞ower-shaped structure is also suitable for designing of a four-band THz and even higher frequency MM absorber, which would be a promising candidate as absorbing elements in scientiflc and technical applications.

Design of a compact ultrawideband meta- material antenna based on the modified split-ring resonator and capacitively loaded strips unit cell

Abstract: A new compact ultrawideband (UWB) patch antenna based on the resonance mechanism of a composite right/left-handed (CRLH) transmission line (TL) is proposed. The radiating element of the antenna is made from three left-handed (LH) metamaterial (MTM) unit cells placed along one axis, where each unit cell combines a modifled split-ring resonator (SRR) structure with capacitively loaded strips (CLS). An analysis of the eigenfrequencies of these unit cells yields one- and two-dimensional dispersion diagrams, which correspond to a one-unit cell antenna and the three unit cell antenna, respectively. A trident feed and a slotted-partial ground plane are used to match the right- and left-handed (RH and LH) modes of the antenna, respectively. In addition, an analysis of the surface current distribution of the antenna shows that slots on the metallic area reduce the Q-factor. This reduction in the Q-factor results in a wide bandwidth of 189% at 3.7GHz, which spans the UWB frequency range between 2.9{ 9.9GHz. The total footprint of the antenna at the lowest frequency is 0:2‚0£0:2‚0£0:015‚0, where ‚0 is the free space wavelength. The gain of the antenna ranges between i1 to 5dB throughout the frequency band.

Reverberation Chamber as a Multivariate Process: FDTD Evaluation of Correlation Matrix and Independent Positions

Abstract: This paper evaluates the mode-stirring e-ciency in terms of uncorrelated positions of a mechanical stirrer operating inside a reverberation chamber (RC). The actual RC is simulated and viewed as a multivariate random process: the chamber fleld is sampled in a lattice of spatial points distributed uniformly over a volume of arbitrary dimensions. By adopting such a grid, the stirrer e-ciency is then computed through the correlation matrix, accounting for the residual correlation between stirrer positions. The second-order statistics are calculated averaging over the sampling volume. Results are presented for two stirrers that move in both synchronous and interleaved mode. A comparison with the traditional circular correlation (CC) method, for the determination of the uncorrelated positions, is done showing how CC overestimates stirrer e-ciency.

A compact quad band-notched uwb monopole antenna loaded one lateral l-shaped slot

Abstract: A novel compact microstrip-fed planar monopole antenna with quad-notched bands is presented. The proposed antenna is based on one rectangular-stepped-patch. To achieve the higher resonance over the 12GHz, one lateral L-shaped structure is embedded in the ground. By inserting four U-shaped slots in the radiation patch, quad band-notched properties in the WiMAX (3.3{3.6GHz), INSAT (4.5{4.8GHz), lower WLAN (5.15{5.35GHz) and higher WLAN (5.725{5.825GHz) are obtained. Experimental results indicate that the designed UWB antenna can obtain broadband matched impedance values, good frequency selectivity over the notched bands, relatively ∞at group delay and nearly omni-directional transmission characteristics across the UWB frequencies. More importantly, the quad-notched bands can be reconflgurable by shorting the corresponding U-shaped slots.

Study on an s-band rectenna array for wireless microwave power transmission

Abstract: The microwave power transmission is an approach for wireless power transmission. As an important component of a microwave wireless power transmission systems, microwave rectennas are widely studied. A rectenna based on a microstrip dipole antenna and a microwave rectifler with high conversion e-ciency were designed at 2.45GHz. The dipole antenna achieved a gain of 5.2dBi, a return loss greater than 10dB, and a bandwidth of 20%. The microwave to DC (MW-DC) conversion e-ciency of the rectifler was measured as 83% with 20dBm input power and 600› load. There are 72 rectennas to form an array with an area of 50cm by 50cm. The measured results show that the arrangement of the rectenna connection is an efiective way to improve the total conversion e-ciency, when the microwave power distribution is not uniform on rectenna array. The experimental results show that the highest microwave power transmission e-ciency reaches 67.6%.

Theory of zero-power rfid sensors based on harmonic generation and orthogonally polarized antennas

Abstract: In this paper a novel approach is proposed to solve the issue of the absolute accuracy required by the most of the passive chip-less RFID sensors. To this purpose the sensor information is encoded as the phase difierence between two signals, one of the two acting as the reference signal for the other one. First the tag receives a carrier at frequency f0, then two equal signals at frequency 2f0 are generated by means of a diode-based frequency doubler and a power divider. At this point one of the two signals is phase-shifted using a passive sensing element. Finally the 2f0 signals are re-irradiated by exploiting two orthogonally polarized antennas. With this approach the sensor information can be extracted by a suitable reader equipped with two complex (I/Q) receivers. The idea will be flrst developed from a theoretical basis and then verifled with several particular cases. The novel tag concept is compatible with paper substrate and inkjet printing technology since antennas diodes and passive sensing elements, i.e., all the main tag components, are going to be developed on paper materials.

A Family of Ultra-Thin, Polarization-Insensitive, Multi-Band, Highly Absorbing Metamaterial Structures

Abstract: The systematic design of size-conflned, polarization- independent metamaterial absorbers that operate in the microwave regime is presented in this paper. The novel unit cell is additionally implemented to create e-cient multi-band and broadband structures by exploiting the scalability property of metamaterials. Numerical simulations along with experimental results from fabricated prototypes verify the highly absorptive performance of the devices, so developed. Moreover, a detailed qualitative and quantitative analysis is provided in order to attain a more intuitive and sound physical interpretation of the underlying absorption mechanism. The assets of the proposed concept, applied to the design of difierent patterns, appear to be potentially instructive for various EMI/EMC conflgurations.

Fractal Koch Multiband Textile Antenna Performance with Bending, Wet Conditions and on the Human Body

Abstract: A multiband Fractal Koch dipole textile antenna is proposed for wearable applications. The antenna is designed to operate at 0.9GHz, 2.45GHz and 5.8GHz. Denim materials as the substrate are selected aiming to obtain robustness, ∞exibility and a lightweight textile antenna. The antenna model is designed, simulated, optimized and analyzed using Microwave Studio CST software. Two types of multiband antenna prototypes are fabricated and evaluated with difierent conducting elements (Shield It fabric and copper foil tape). Antenna performance is observed in terms of return loss, bandwidth, radiation pattern and realized gain. Three difierent comprehensive analyses are taken into consideration: measurement antenna with difierent bending sizes, on-body measurement and under wet conditions. The antenna performances are evaluated based on resonant frequency (fo) and bandwidth (BW). The antennas performance with bending on the human body (arm & forearm) is compared and investigated. A suitable placement on the body has been discovered between the chest and backside. The antennas have also been tested under wet conditions to ensure a stable characteristic under the in∞uence of water.

Design of a Compact UWB Antenna Integrated with GSM/Wcdma/WLAN Bands

Abstract: In this research, a compact printed antenna design operating on ultra-wideband (UWB) and three extra wireless communication bands is proposed. An ellipse-shaped monopole is utilized to realize UWB application (3.1{10.6GHz). The modifled ground employs three folded Capacitive Loaded Line Resonators (CLLRs) to obtain triple relatively lower communication bands, including parts of global System for Mobile Communications (GSM) band at the centre frequency of 1.78GHz, Wideband Code Division Multiple Access (WCDMA) band at the centre frequency of 2.15GHz, and Wireless Local Area Networks (WLAN) band at the centre frequency of 2.4GHz. The CLLRs are designed with quarter- wavelength to control the corresponding frequencies independently. Good agreement is achieved between the simulation and measurement to verify our presented design. The basic, dual-, triple-band UWB antennas are also simulated and good results are obtained. Small group delay variations across UWB frequencies are obtained for the presented antenna and reference antennas, with some level of distortion observed.

A Substrate Integrated Waveguide Bandpass Filter Using Novel Defected Ground Structure Shape

Abstract: In this paper, a X-band wideband bandpass fllter based on a novel substrate integrated waveguide-to-defected ground structure (SIW-DGS) cell is presented. In the cell, the DGS is etched on the top plane of the SIW with high accuracy, so that the performance of the fllter can be kept as good as possible. Finally, the fllter, consisting of three cascaded cells, is designed and measured to meet compact size, low insertion loss, good return loss as well as smooth group delay. There is good agreement between the measurement and simulation results.

Giant circular dichroism and negative refractive index of chiral metamaterial based on split-ring resonators

Abstract: In this paper, a double-layer split-ring resonator structure chiral metamaterial was proposed which could exhibit pronounced circular dichroism (CD) efiect and negative refractive index at microwave frequencies. Experiment and simulation calculations are in good agreement. The retrieved efiective electromagnetic parameters indicate that the lower frequency CD efiect is associated with the negative refractive index property of the left circularly polarized (LCP) wave, and the upper one is to the right circularly polarized (RCP) wave. The mechanism of the giant CD efiect could be further illustrated by simulated surface current and power loss density distributions.

Asymmetric Transmission of Linearly Polarized Waves and Dynamically Wave Rotation Using Chiral Metamaterial

Abstract: The asymmetric transmission of the linearly polarized waves at normal incidence through the lossy anisotropic chiral structure is demonstrated. The proposed chiral metamaterial structure is composed of bi-layered discontinuous cross-wire-strips, and it is utilized in order to realize polarization rotation. Firstly, the theoretical relations between the incident polarization and the polarization rotation are derived using transmission matrices. Secondly, a strong and dynamically asymmetric transmission of linearly polarized electromagnetic wave through the chiral metamaterial has been demonstrated for microwave region, both by simulation and experimentally. The experiment results are in good agreement with the simulation ones. It can be seen from the results that the proposed chiral metamaterial structure can be used to design novel polarization control devices for several frequency regions.

Sparse Array Microwave 3-D Imaging: Compressed Sensing Recovery and Experimental Study

Abstract: Microwave array 3-D imaging is an emerging technique capable of producing a 3-D map of scattered electric flelds. Its all-weather and large scene imaging features make it an attractive powerful tool for target detection and feature extraction. Typically, a microwave array 3-D imaging system based on the classical sampling theory requires a large dense 2-D antenna array, which may sufier from a very high cost. To reduce the number of the antenna array elements, this paper surveys the use of compressed sensing recovery and sparse measurement strategies for microwave array 3-D imaging. Combining with the typical spatial sparsity of the underlying scene, we pose the sparse array microwave 3-D imaging as flnding sparse solutions to under-determined linear equations. Further, to reduce the computational of the compressed sensing recovery with the large- scale echoes data, we divide the underlying 3-D scene into a series of equal-range 2-D slices, and deal with these slices separately using the orthogonal matching pursuit (OMP) algorithm. Lastly, the performance of the presented compressed sensing approach is verifled by an X-band microwave array 3-D imaging system. The experimental results demonstrate that the compressed sensing approach can produce a better resolution 3-D image of the observed scatterers compared with the conventional method, especially in the case of very sparse activate antenna array.

Exposure optimization in indoor wireless networks by heuristic network planning

Abstract: Due to the increased use of indoor wireless networks and the concern about human exposure to radio-frequency sources, exposure awareness has increased during recent years. However, current-day network planners rarely take into account electric-fleld strengths when designing networks. Therefore, in this paper, a heuristic indoor network planner for exposure calculation and optimization of wireless networks is developed, jointly optimizing coverage and exposure, for homogeneous or heterogeneous networks. The implemented exposure models are validated by simulations and measurements. As a flrst novel optimization feature, networks are designed that do not exceed a user-deflned electric-fleld strength value in the building. The in∞uence of the maximally allowed fleld strength, based on norms in difierent countries, and the assumed minimal separation between the access point and the human are investigated for a typical o-ce building. As a second feature, a novel heuristic exposure minimization algorithm is presented and applied to a wireless homogeneous WiFi and a heterogeneous WiFi-LTE femtocell network, using a new metric that is simple but accurate. Field strength reductions of a factor 3 to 6 compared to traditional network deployments are achieved and a more homogeneous distribution of the observed fleld values on the building ∞oor is obtained. Also, the in∞uence of the throughput requirement on the fleld strength distribution on the building ∞oor is assessed. Moreover, it is shown that exposure minimization is more efiective for high than for low throughput requirements and that high fleld values are more reduced than low fleld values.

The use of a human body model to determine the variation of path losses in the human body channel in wireless capsule endoscopy

Abstract: Presently, wireless capsule endoscopy (WCE) is the sole technology for inspecting the human gastrointestinal (GI) tract for diseases painlessly and in a non-invasive way. For the further development of WCE, the main concern is the development of a high- speed telemetry system that is capable of transmitting high-resolution images at a higher frame rate, which is also a concern in the use of conventional endoscopy. A vital task for such a high-speed telemetry system is to be able to determine the path loss and how it varies in a radio channel in order to calculate the proper link budget. The hostile nature of the human body's channel and the complex anatomical structure of the GI tract cause remarkable variations in path loss at difierent frequencies of the system as well as at capsule locations that have high impacts on the calculation of the link budget. This paper presents the path loss and its variation in terms of system frequency and location of the capsule. Along with the guideline about the optimum system frequency for WCE, we present the difierence between the maximum and minimum path loss at difierent anatomical regions, which is the most important information in the link-margin setup for highly e-cient telemetry systems in next-generation capsules. In order

Dual-Band Polarization Independent Metamaterial Absorber Based on Omega Resoanator and Octa-Star Strip Configuration

Abstract: Dual-band metamaterial absorber (MA) with polarization independency based on omega (›) resonator with gap and octa- star strip (OSS) conflguration is presented both numerically and experimentally. The suggested MA has a simple conflguration which introduces ∞exibility to adjust its metamaterial (MTM) properties and easily re-scale the structure for other frequencies. In addition, the dual- band character of the absorber provides additional degree of freedom to control the absorption band(s). Two maxima in the absorption are experimentally obtained around 99% at 4:0GHz for the flrst band and 79% at 5:6GHz for the second band which are in good agreement with the numerical simulations (99% and 84%, respectively). Besides, numerical simulations validate that the MA could achieve very high absorption at wide angles of incidence for both transverse electric (TE) and transverse magnetic (TM) waves. The proposed MA and its variations enable myriad potential applications in medical technologies, sensors, modulators, wireless communication, and so on.