This paper aimed to take closer steps towards real wearability by investigating the possibilities of designing and fabricating highly efficient and fully flexible wearable microstrip patch antenna for operating frequency of 5.8 GHz as a center frequency. Two types of conducting materials have been used for conducting parts: conventional metal plane and woven electro-textile material, while a non-conducting jeans fabric has been used as antenna substrate material. The dielectric constant εr = 1.78, and loss tangent tanδ = 0.085 of the jeans substrate measured by using two different methods. Also, the electromagnetic properties of the electro-textile are studied in details. The conductivity of e-textile cell is equal to 2.5×106 S/m and the surface impedance of e-textile cell equal to 0.0395+J18.4 Ω. Furthermore, the proposed wearable antenna may be attached to human body, so the specific absorption ratio (SAR) must be calculated. Finally, the proposed design is simulated by CST simulator version 2016, fabricated using folded copper and measured by Agilent8719ES VNA.
A new structure design of a dual-band suspended microstrip meshed patch antenna integrated with a polycrystalline silicon solar cell for Ku-band satellite applications is proposed and presented. This antenna element is a basic building block for a Ku-band meshed array antenna used for two-way satellite internet and TV applications at rural and remote locations. The antenna covers the operating frequency range from 11.7 GHz to 12.22 GHz downlink band and from 14.0 GHz to 14.5 GHz uplink band allocated by the ITU to the Regions 1 and 2. While achieving 500 MHz bandwidth across each band, fully covering the Ku-band uplink and downlink frequency bands, the antenna offers a single element gain of 6.05 dBi in the downlink band and 7.61 dBi in the uplink band. The antenna has been fabricated and measured, and good agreement is achieved between the experimental and simulated results. In addition, a good compromise between RF performance and optical transparency is obtained. The overall visible light transmission is found to be approximately 87%. A compact low-profile antenna element is also achieved.
Intentional Electromagnetic Interference (IEMI) is one of the applications of High Power Electromagnetics (HPEM) for causing intentional interference in military targets such as C4I (Command, Control, Communication, Computer and Intelligence) targets and segments of civilian systems like critical VSAT's (Very Small Aperture Terminals), power grid and communication network, weather and air-traffic control radars etc. HPEM essentially consists of generation of intense electromagnetic waves either as High Power Microwave (HPM) or Ultra Wide Band (UWB) waves to cause electromagnetic interference. High power UWB waves are promising candidate for IEMI application. One such UWB source, developed for the purpose of radiating high intensity, fast rise time, short pulses, is the Half Impulse Radiating Antenna (HIRA) which covers a frequency range of 100 MHz to 6 GHz. In this paper, characteristics of UWB source i.e., HIRA, such as characteristics of electric field in both boresight and off-boresight, far field boundary and radiation pattern were computed. The UWB pulse dispersion through civil infrastructure and their coupling to power cables were studied experimentally.
A square-shaped complementary split ring resonator (CSRR) filtering structure for isolation improvement is presented in this paper. The proposed research work investigates the design and development of a simple and compact CSRR structure. In order to verify the performance of the proposed filtering element and improve the isolation among the closely placed antenna elements, arrays of configured CSRR structures are implemented between two antenna elements. An array of configured CSRR elements has been integrated with the printed antenna on the top and bottom layers. The proposed filtering elements offer an enhancement in isolation by 25 dB as compared to the simple array. The entire configuration has been simulated using the Ansoft HFSS simulator. Finally, the proposed design is fabricated and experimentally validated. In the experiment, coupling suppression of -51 dB at the operating frequency is successfully achieved, resulting in a recovery of the array pattern. The proposed antenna is highly efficient, which is suitable to be utilized for 5G communication.
This article studies the spatial domain and polarization domain characteristics of multipath channels in a subway-like tunnel environment. Experiments were performed by rotating a horn antenna with 30◦ half power beamwidth (HPBW) in the azimuthal direction for two different transmitter-receiver (Tx-Rx) distances. The time domain measurement is conducted when carrier frequency is set as 1.8 GHz. The cross-polarization discrimination (XPD) is studied, and it is found that the maximum depolarized signals are from sidewalls. The characteristics of power azimuth spectrum (PAS) of co-polarized and cross-polarized signals follow a multi-cluster Gaussian distribution. Ray-tracing method is employed to investigate the wave propagation in the tunnel environment. The results demonstrate that the main multipath components (MPCs) are around the line-of-sight (LOS) direction, and the reflected waves are from the other end of the tunnel (RWET). The correlation coefficient of co-polarized configuration pursues an increasing function with respect to the Tx-Rx distance and a decreasing function with respect to the cross-polarized configuration.
Deep sub-wavelength metamaterials for a wireless power transfer system (WPT) is still a challenge in design and optimization. We propose a large capacitor spiral metamaterial (LCSM) which involves inherent advantages of low operating frequencies and compact structures. The ratio of electromagnetic wavelength to the metamaterial scale can easily reach 1000 at the operation frequency of several megahertz. A hybrid search method, which combines a modified simulated annealing algorithm and a differential evolution algorithm, is applied to the accurate and automatic design of LCSM. The permeability of LCSM is evaluated by finite element analysis and then verified by experimental results. Finally, a small-size WPT system working at 6.78 MHz was constructed to evaluate LCSM. The results show that LCSM can enhance the transfer efficiency of the WPT system from 5.54% to 22.40% at a transmission distance of 15 cm.
A novel ultra-wideband CPW to CPS transition for TSA in landmine detection by GPR system is proposed. The structure is constructed on a 140x140 mm2 FR4 dielectric substrate. It is composed of 2 sections. The first is nonuniform tapered asymmetric coplanar waveguide (TACPW), and the second section is nonuniform Tapered Asymmetric Coplanar Strips (TACPS). Electromagnetic Band Gap (EBG) structure of coplanar circular patches exists near the transition open slot and aligned with the outer edge of the CPW ground to act as a capacitive loading. The design of the proposed transition is given in very simple four design steps. The CPW to CPS transition is analyzed theoretically and experimentally. To characterize this transition, back to back transition is constructed; besides, the equivalent-circuit model that consists of nonuniform transmission lines is established. The equivalent circuit is constructed by dividing both sections TACPW and TACPS into 35 sections and using ABCD parameters to characterize each section, and conversion to S-parameters is done using MATLAB Program. The selection criterion of the section length is to maintain a linear change in the characteristic impedance with the distance. The results based on equivalent-circuit model, CST simulation (CST studio ver.15), and measurements are compared. Several parameters are studied through simulations and experiments which are used to derive some design guidelines. The operational bandwidth for the CPW to CPS transition covers from 0 (DC) to almost 10 GHz with minimum return loss reaches -50 dB. For the GPR application (landmine detection) which extends from 0.4 to 3 GHz, the insertion loss of the proposed transition reaches almost -0.5 dB which satisfies the design requirements. The back to back transition performance was simulated and measured. Good agreement is found between numerical and experimental results especially for the GPR ranges of frequencies. The proposed transition has the advantages of compact size, ultra-wide bandwidth, and straightforward design procedure.
This paper presents a theoretical approach to compare the performance of a directive and a quasi-omnidirectional on-body antennas.Two canonical antennas, namely, a dipole and a rectangular aperture, are considered in the 60 GHz band. We first demonstrate that for this on-body configuration, the classically-defined far-field antenna gain depends on the observation distance. Consequently, we derive results in terms of radiation efficiency and link budget. To do so, the antenna input impedance computation is a preliminary step to normalize the input power to allow a fair comparison between the two antennas. The impedance over a lossy half-plane of an aperture illuminated by a TE10 mode normally polarized is therefore derived into a convenient easy-to-compute formulation, which to authors' best knowledge, is not available in the literature. In terms of link budget, it is obtained that the received power due to an aperture is generally higher than the one due to the dipole in the main lobe direction. A constant difference is observed along the distance, and this difference increases with the aperture width for antennas touching the body. Besides, it is shown that the standard aperture waveguide WR15 exhibits a slightly higher efficiency than a vertical dipole with the same vertical size when being placed at a distance less than 3 mm (i.e., 0.6λ) from the body phantom surface. Above this distance, the dipole and the aperture exhibit similar efficiency in the order of 60%.
Design and analysis of a novel wide-band covering, hetero triangle linked hybrid web fractal antenna is presented in this paper. The hetero triangle linked hybrid web structure has been designed through multiple iterations in the CST MICROWAVE STUDIO electromagnetic simulation tool and has been fabricated on FR4 dielectric of εr = 4.4 with height of 1.6 mm. The proposed antenna offers a comprehensive bandwidth of 18.055 GHz, covering from 1.945 GHz to 20 GHz. It supports various applications starting from 3G, LTE, ISM, Bluetooth, Wi-Fi, WLAN (2.4-2.48 GHz) and 5.2/5.8 GHz (5.15-5.35 GHz/5.72-5.82 GHz), WiMAX operating in the 2.3/2.5 GHz (2.305-2.36 GHz/2.5-2.69 GHz), 5.5 GHz (5.25-5.85 GHz) and Satellite communication (Ku band: Uplink of 14 GHz and Downlink of 10.9-12.75 GHz). The proposed antenna provides peak realized gain of 7.17 dB with efficiency more than 78% in the operating band. The antenna parameters such as reflection coefficient, gain and radiation patterns are determined through numerical simulation, and good matching is obtained with measured results.
In this work, the design of a switched beam antenna array based on an optimized Butler matrix feeding network was done with a compact microstrip structure and a set of microchip antennas working at 2.45 GHz. The obtained antenna feeding network was tuned and optimized by using suitable unsupervised techniques to obtain a compact and efficient structure. A microstrip antenna array prototype composed by four elements was fabricated and experimentally tested. Good impedance matching and radiation properties have been experimentally verified with reference to the main beam steering capability.
Using uniform linear array (ULA), a passive localization algorithm is presented for mixed far-field (FF) and near-field (NF) signals scenarios. Based on the high-order cumulant (HOC) technique, a special Hermite matrix is constructed by three fourth-order cumulant matrices, which are calculated by dividing the ULA into two sub-arrays. Then, the special matrix of signals is decomposed to obtain the source subspace. According to ESPRIT algorithm, two transformation matrices of all sub-arrays can be obtained. Meanwhile, the two transformation matrixes could be used to calculate the range and angles of arrival (AOA) of NF sources, as well as AOAs of FF sources. Moreover, compared with twostage MUSIC (TSMUSIC) and four-order cumulant MUSIC method, the proposed algorithm has higher accuracy for localisation of both FF and NF sources without any spectral search.
This paper presents a Ka-band TDD transceiver system module for the secondary surveillance radar application with attractive temperature characteristic. Four multifunction chips and a MEMS filter are designed and fabricated in GaAs pseudomorphic high electron mobility transistor (pHEMT) process and MEMS technology in this work, respectively. These multifunction chips and MEMS filter with some other commercial chips are assembled in a compact cavity to form the transceiver system. The temperature characteristics of the designed chips and the whole transceiver module are measured respectively in this work. Benefiting from the designed temperature compensation circuits on the chips, the transceiver is able to work from -55˚C to +75˚C with little performance fluctuation. The noise figure of the receiver is less than 3.7 dB in the 400 MHz working bandwidth. Its dynamic range is more than 59 dB with more than 23.9 dB power gain. The maximum output power of the transmitter is larger than 30.3 dBm. The system only has two input/output ports and one control bus, which is suitable for the large-scale system integration.
A model-based inversion algorithm combined with the curl-conforming volume integral equation method is presented for the reconstruction of 3D anisotropic objects. The forward algorithm utilizes the curl-conforming volume integral equation method. The inversion algorithm is based on the Gauss-Newton method. The approach is applied to the reconstruction of the permittivities of 3D anisotropic objects. Moreover, sensitivity analysis of the data from different polarizations of transmitters and receivers to the anisotropic properties is performed. Numerical examples show the effectiveness of the inversion algorithm and demonstrate the sensitivities of data from different transmitter and receiver pairs to the anisotropy.
In this part, we develop an efficient algorithm for the computation of the complete transmitted and reflected electromagnetic fields in generic 2D arrays of carbon nanotubes (CNTs). The method relies on first approaching individual CNTs using an effective-boundary condition based on a proper quantum conductivity model. An exact eigenmode solution is obtained for this problem for both single-wall and multi-wall CNTs, which then is integrated with Floquet mode theory to handle periodic arrays of CNTs. The algorithm's convergence rate is accelerated using special methods and then applied to the analysis and design of various multi-layered CNT-based photonic crystals. It is shown that the proposed method can clearly demarcate the intrinsic resonances due to electronic transitions in individual CNTS and new sets of geometric resonances produced by the array environment. The algorithm can be used to analyze measured optical spectra of CNT composites and to design new optical bandgap devices.
A highly miniaturized significant gain triple band patch antenna loaded with a new modified double circular slot ring resonator (MDCsRR) metamaterial unit cell is presented in this paper. Novel MDCsRR is a compact low frequency slot ring resonator. The principle of the proposed patch antenna element is based on adding series capacitance to decrease the half wavelength resonance frequency, thus reducing the electrical size of the proposed patch antenna. The transmission line model is used to analyze passband and stopband characteristics of the radiating bands. Circulating current distribution around MDCsRR slot with increased interdigital capacitor finger length causes multiple modes to propagate. The MDCsRR metamaterial unit cell consists of a new modified circular slot ring resonator (MCsRR) with metallic strip finger. The proposed structure is compact in size with radiating element dimensions of 0.20λ × 0.20λ × 0.008λ at first resonating frequency. The proposed antenna offers triple band operation with significant calculated antenna gain of 3.28 dBi at first center frequency of 3.2 GHz, 2.76 dBi at second center frequency of 5.4 GHz and 3.1 dBi at third center frequency of 5.8 GHz. The electrical size of the proposed antenna is miniaturized by about 68.83% as compared to the conventional patch antenna operating at first resonating frequency.
With the increase of low power devices, the design of a compact and efficient rectenna is essential for supplying energy to the devices. This paper presents a compact rectenna for high efficient WiFi energy harvesting. A novel fractal geometry is introduced in the design of antenna for miniaturization, and the ability to harvest WiFi energy is enhanced due to its characteristics of self-similarity and space filling. Besides, a single stub matching network is designed to achieve high conversion efficiency with a relatively low input power ranging from -20 dBm to 0 dBm. Simulation and experiments have been carried out. The results show that the proposed antenna features a good characteristic of reflection coefficient and realized gain at WiFi band. The highest RF to DC conversion efficiency of the rectenna is up to 52% at 2.48 GHz with the input power of 0 dBm. This study demonstrates that the proposed rectenna can be applied to a range of low power electronic applications.
The surface plasmon effect in metallic photonic crystals has been investigated. Band structure graph is the only graph that can be used to explain the characteristics of photonic crystals. In this work, band structure graphs have been used to describe these characteristics, which include the surface plasmon effect of photonic crystals. Recently, band structure graphs for frequency-dependent materials have been analyzed by several researchers. The surface plasmon effect has been found for these materials. This article reports the effect of surface plasmons which cause resonance state in the metallic photonic crystals when the relative permittivity is changed from band structure graphs. The numerical results from the commercial software show the magnetic field distribution of waves on the normal photonic crystals, and defect mode is added for each frequency.
This article proposes a beam focusing compact wideband microstrip antenna loaded with mu negative (MNG) metamaterial. The antenna is designed to operate in the frequency spectra of IEEE 802.11a wireless LAN 5.15-5.85 GHz. The controlling of the beam direction has been investigated using eight different switching combinations of 12 PIN diodes which are integrated in the metamaterial unit cells. The main beam is found to be focused in -ve y, +ve y and omnidirectional in yz plane in agreement with switching condition of the metamaterial unit cell. The maximum gain enhancement of 7 dB is obtained at 4.9 GHz as the beam of the power pattern is focused in the negative y direction. The basic antenna with patch dimension (0.14λ × 0.14λ) provides wide impedance bandwidth of about 40%. Two prototypes of basic and proposed antennas have been developed using a low profile FR-4 substrate. The simulation results are found in good agreement with the measurement ones.
This paper discusses the in fluence of simplifications in models used in the design of electromagnetic protection against indirect effects of lightning strikes. A real and complex test case such as the power plant of an A400M aircraft, simulated with the FDTD method, is chosen for this. The parameters studied are the inclusion/removal of installations, modification of electrical contacts, material properties, and changes in the cable characteristics. The simulations performed allow us to quantify the impact of different simplification approaches and, in consequence, to draw conclusions on the relative importance of different model features, being the most important ones to maintain the electrical contacts, to include installations and cables carrying high currents, to consider different materials, to respect the accurate cable routes or to take care of isolated equipment.
Design, simulation, implementation and measurement results of multiline and multilayer microstrip directional couplers are given with closed form relations. Step-by-step design procedure reflecting the design practice of directional couplers, which requires only information on coupling level, port impedances and operational frequency, is presented. The method based on the synthesis technique applied in the design of conventional two-line microstrip symmetrical directional couplers is adapted to design multilayer directional couplers with the aid of electromagnetic simulators using parametric analysis with curve fitting method. The proposed design method is compared with the measurement results and accuracy is verified. It has been also shown that the directivity of the couplers designed using the multilayer structure is improved significantly. A method such as the one presented in this paper can be used to design multilayer two-line and three-line directional couplers which can be integrated to the front end of an RFID systems to provide the required isolation between transmitter and receiver and prevent signal leakage due to use of conventional circulators.