Showing papers in "IEEE Transactions on Antennas and Propagation in 2011"
TL;DR: In this paper, a sinusoidally-modulated reactance surface (SMRS) was designed for an arbitrary off-broadside angle, which allows for nearly independent control of the leakage and phase constants along the surface.
Abstract: A simple procedure for designing a sinusoidally-modulated reactance surface (SMRS) that radiates at an arbitrary off-broadside angle is outlined. The procedure allows for nearly independent control of the leakage and phase constants along the surface. Printing an array of metallic strips over a grounded dielectric substrate is discussed as a way to practically implement the theoretical SMRS. A method of mapping the gaps between metallic strips to a desired surface impedance is presented as an efficient alternative to mapping methods used in the past. A printed leaky-wave antenna with a sinusoidally-modulated surface reactance is designed using the procedure mentioned above. The TM-polarized antenna radiates at 30° from broadside at 10 GHz, and exhibits an experimental gain of 18.4 dB. Theoretical, simulated, and experimental results are presented.
364 citations
TL;DR: In this article, the authors proposed a CRLH leaky-wave antenna for antenna applications, which is realized by etching interdigital slots on the waveguide surface and the ground.
Abstract: Composite right/left-handed (CRLH) substrate integrated waveguide (SIW) and half mode substrate integrated waveguide (HMSIW) leaky-wave structures for antenna applications are proposed and investigated. Their propagation properties and radiation characteristics are studied extensively. Their backfire-to-endfire beam-steering capabilities through frequency scanning are demonstrated and discussed. These metamaterial radiating structures are realized by etching interdigital slots on the waveguide surface and the ground. The slot behaves as a series capacitor as well as a radiator leading to a CRLH leaky-wave application. Four antennas are fabricated, measured, and analyzed, including two balanced CRLH SIW designs characterized by single-side or double-side radiation, and two unbalanced HMSIW designs characterized by different boundary conditions. Antenna parameters such as return loss, radiation patterns, gain, and efficiency are all provided. Measured results are consistent with the simulation. All these proposed antennas possess the advantages of low profile, low cost, and low weight, while they are also showing their own unique features, like high directivity, quasi-omnidirectional radiation, miniaturized size, continuous beam-steering capabilities covering both the backward and forward quadrants, etc., providing much design flexibility for the real applications.
304 citations
TL;DR: In this article, a double-layer hollow-waveguide slot array is proposed, where a full-corporate feed waveguide is arranged in the lower layer to suppress the reflection over a wideband.
Abstract: In order to achieve a wide bandwidth characteristic of high gain and high efficiency antennas, a double-layer hollow-waveguide slot array is proposed, where a full-corporate-feed waveguide is arranged in the lower layer. This antenna can be built up easily by the process of diffusion bonding of laminated thin metal etching plates, which has high precision and is possibly a low cost technique. The radiating elements and the feed waveguide are designed to suppress the reflection over a wideband. The predicted bandwidth of the reflection less than -14 dB is 8.3% for a 16 × 16-element array antenna. A test antenna is fabricated in the 60-GHz band, and about 80% antenna efficiency with more than 32 dBi is achieved over 4.8 GHz.
296 citations
TL;DR: A numerically-efficient technique based on the Bayesian compressive sampling (BCS) for the design of maximally-sparse linear arrays is introduced, based on a probabilistic formulation of the array synthesis and it exploits a fast relevance vector machine for the problem solution.
Abstract: A numerically-efficient technique based on the Bayesian compressive sampling (BCS) for the design of maximally-sparse linear arrays is introduced. The method is based on a probabilistic formulation of the array synthesis and it exploits a fast relevance vector machine (RVM) for the problem solution. The proposed approach allows the design of linear arrangements fitting desired power patterns with a reduced number of non-uniformly spaced active elements. The numerical validation assesses the effectiveness and computational efficiency of the proposed approach as a suitable complement to existing state-of-the-art techniques for the design of sparse arrays.
286 citations
TL;DR: In this article, a triple-frequency microstrip-fed planar monopole antenna for multiband operation is proposed and investigated, which has a small overall size of 20 × 30 mm2, and operates over the frequency ranges 2.14-2.52 GHz, 2.82-3.74 GHz, and 5.15-6.02 GHz suitable for WLAN 2.4/5.8 GHz and WiMAX 3.5/5 GHz applications.
Abstract: A novel triple-frequency microstrip-fed planar monopole antenna for multiband operation is proposed and investigated. Defected ground structure (DGS) is used in this antenna, which has a rectangular patch with dual inverted L-shaped strips and is fed by a cross-shaped stripline, for achieving additional resonances and bandwidth enhancements. The designed antenna has a small overall size of 20 × 30 mm2, and operates over the frequency ranges, 2.14-2.52 GHz, 2.82-3.74 GHz, and 5.15-6.02 GHz suitable for WLAN 2.4/5.2/5.8 GHz and WiMAX 3.5/5.5 GHz applications. There is good agreement between the measured and simulated results. Experimental results show that the antenna gives monopole-like radiation patterns and good antenna gains over the operating bands. In addition, effects of both the length of the protrudent strips and the dimensions of the DGS for this design on the electromagnetic performance are examined and discussed in detail.
270 citations
TL;DR: Different kinds of spiral planar circularly polarized (CP) antennas are presented in this article, which are based on an interaction between a cylindrical surface-wave excited by an omnidirectional probe and a inhomogeneous surface impedance with a spiral pattern.
Abstract: Different kinds of spiral planar circularly polarized (CP) antennas are presented. These antennas are based on an interaction between a cylindrical surface-wave excited by an omnidirectional probe and a inhomogeneous surface impedance with a spiral pattern. The surface impedance interaction transforms a bounded surface wave into a circularly polarized leaky wave with almost broadside radiation. The problem is studied by adiabatically matching the local 2D solution of a modulated surface-impedance problem to the actual surface. Analytical expressions are derived for the far-field radiation pattern; on this basis, universal design curves for antenna gain are given and a design procedure is outlined. Two types of practical solutions are presented, which are relevant to different implementations of the impedance modulation: i) a grounded dielectric slab with a spiral-sinusoidal thickness and ii) a texture of dense printed patches with sizes variable with a spiral-sinusoidal function. Full wave results are compared successfully with the analytical approximations. Both the layouts represent good solutions for millimeter wave CP antennas.
270 citations
TL;DR: In this paper, a large electronically reconfigurable reflectarray antenna that has 160 × 160 reflecting elements was designed, fabricated, and evaluated so that it could be applied to a millimeter-wave imaging system operating in the 60 GHz band.
Abstract: A large electronically reconfigurable reflectarray antenna that has 160 × 160 reflecting elements was designed, fabricated, and evaluated so that it could be applied to a millimeter-wave imaging system operating in the 60-GHz band. To make it feasible to construct such a large reflectarray, the reflecting element structure had to be simple and easily controlled; therefore, a reflecting element consisting of a microstrip patch and a single-bit digital phase shifter using a p-i-n diode was employed. A large reflectarray antenna was fabricated using the reflecting elements. The measured radiation patterns and antenna gain were in good agreement with those that were calculated. Furthermore, the near-field beam focusing capabilities, which was required to image near-field objects, were also verified through an experiment. Finally, the response time for beamforming was measured, which was far less than the system requirements.
242 citations
TL;DR: A new compact planar ultrawideband (UWB) antenna designed for on-body communications is presented and shows very good performance within the 3-11.2 GHz range, and therefore it might be used successfully for the 3.1-10.6 GHz IR-UWB systems.
Abstract: A new compact planar ultrawideband (UWB) antenna designed for on-body communications is presented. The antenna is characterized in free space, on a homogeneous phantom modeling a human arm, and on a realistic high-resolution whole-body voxel model. In all configurations it demonstrates very satisfactory features for on-body propagation. The results are presented in terms of return loss, radiation pattern, efficiency, and E-field distribution. The antenna shows very good performance within the 3-11.2 GHz range, and therefore it might be used successfully for the 3.1-10.6 GHz IR-UWB systems. The simulation results for the return loss and radiation patterns are in good agreement with measurements. Finally, a time-domain analysis over the whole-body voxel model is performed for impulse radio applications, and transmission scenarios with several antennas placed on the body are analyzed and compared.
241 citations
TL;DR: In this paper, a substrate integrated waveguide fed cavity array antenna using multilayered low temperature co-fired ceramic technology is presented and designed at V-band (60 GHz).
Abstract: A substrate integrated waveguide fed cavity array antenna using multilayered low temperature co-fired ceramic technology is presented and designed at V-band (60 GHz). The 8 × 8 antenna array is designed with an enhanced bandwidth of 17.1% and a gain up to 22.1 dBi by reconfiguring radiating elements, feeding network, and the transition. The proposed array antenna also features the merits of compact size, stable performance, and high efficiency.
240 citations
TL;DR: In this paper, the authors proposed a multi-beam leaky-wave pillbox antenna based on three main parts: feeding part (integrated horns), quasi-optical system and radiating part.
Abstract: This work proposes a novel multi-beam leaky-wave pillbox antenna. The antenna system is based on three main parts: feeding part (integrated horns), quasi-optical system and radiating part. The radiating and input parts are placed in two different stacked substrates connected by an optimized quasi-optical system. In contrast to conventional pillbox antennas, the quasi-optical system is made by a pin-made integrated parabola and several coupling slots whose sizes and positions are used to efficiently transfer the energy coming from the input part to the radiating part. The latter consists of a printed leaky-wave antenna, namely an array of slots etched on the uppermost metal layer. Seven pin-made integrated horns are placed in the focal plane of the integrated parabola to radiate seven beams in the far field. Each part of the antenna structure can be optimized independently, thus facilitating and speeding up the complete antenna design. The antenna concept has been validated by measurements (around 24 GHz) showing a scanning capability over ±30° in azimuth and more than 20° in elevation thanks to the frequency scanning behavior of the leaky-wave radiating part. The proposed antenna is well suited to low-cost printed circuit board fabrication process, and its low profile and compactness make it a very promising solution for applications in the millimeter-wave range.
231 citations
TL;DR: In this article, two types of substrate integrated waveguide (SIW) long slot leaky-wave antennas with controllable sidelobe level are proposed and demonstrated and demonstrated.
Abstract: Two types of substrate integrated waveguide (SIW) long slot leaky-wave antennas with controllable sidelobe level are proposed and demonstrated in this paper. The first prototype is able to achieve an excellent sidelobe level of -27.7ndB by properly meandering a long slot etched on the broadside of a straight SIW section from the centerline toward the sidewall then back. But it is known that an asymmetrically curved slot would worsen the cross-polar level. To overcome this drawback, a modified leaky-wave antenna is proposed, which has a straight long slot etched on the broadside of a meandering SIW section. It yields an outstanding sidelobe level of -29.3 dB and also improves the cross-polar level by more than 11 dB at 35 GHz. Experimental results agree well with simulations, thus validating our design. Then, a two-dimensional (2-D) multibeam antenna is developed by combining such 14 leaky-wave antennas with an SIW beamforming network (BFN). It has features of scanning both in elevation orientation by varying frequency and in cross-plane direction by using the BFN. Excited at ports 1-10 of such a 2-D multibeam antenna at 35 GHz, angular region of 86.6° in azimuth can effectively be covered by 3 dB beam-width of ten pencil beams. Varying frequency from 33 GHz to 37 GHz, the angular region of 37.5° and 38.9° in elevation can be covered by 3 dB beam-width of those continuous scanning beams excited at ports 6 and 8 respectively.
TL;DR: The synthesis of simultaneous broadside sum and difference patterns, flat-top and narrow beam patterns, and steered multibeams is enabled as assessed by a set of selected results reported and discussed to show the potentialities of the proposed method.
Abstract: In this paper, the synthesis of simultaneous multibeams through time-modulated linear arrays is studied. Unlike classical phased arrays where the antenna aperture is usually shared to generate multiple beams, the periodic on-off sequences controlling the static excitations are properly defined by means of an optimization strategy based on the Particle Swarm algorithm to afford desired multiple patterns at harmonic frequencies to make practical application of these harmonic beams which are typically regarded as an undesirable effect in time-modulated arrays. The synthesis of simultaneous broadside sum and difference patterns, flat-top and narrow beam patterns, and steered multibeams is enabled as assessed by a set of selected results reported and discussed to show the potentialities of the proposed method. Comparisons with previously published results are reported, as well.
TL;DR: In this article, a novel antenna design that effectively covers three bands (the medical implant communications service (MICS) band at 402 MHz, and the industrial, scientific, and medical (ISM) bands at 433 MHz and 2.45 GHz) using a π-shaped radiator with a stacked and spiral structure is described.
Abstract: A novel antenna design that effectively covers three bands (the medical implant communications service (MICS) band at 402 MHz, and the industrial, scientific, and medical (ISM) band at 433 MHz and 2.45 GHz) using a π-shaped radiator with a stacked and spiral structure is described. The antenna has compact size of 254 mm 3 (10 mm by 10 mm by 2.54 mm). The proposed design is effective for triple-band biotelemetry with data telemetry (402 MHz), wireless powering transmission (433 MHz), and wake-up controller (2.45 GHz). An experimental prototype of the compact stacked rectenna was fabricated on a Roger 3210 substrate. This antenna was used in a rectenna (rectifying antenna) for 433 MHz wireless powering transmission, and provided a conversion efficiency of 86% when 11 dBm microwave power was received at 433 MHz with a 5 kΩ load. The optimal antenna was fabricated and tested in a minced front leg of pork. The simulated and measured bandwidths were 86 MHz and 113 MHz in the MICS band, and 60 MHz and 70 MHz in the ISM band, respectively.
TL;DR: In this article, a technique for designing low-profile planar microwave lenses consisting of numerous miniature spatial phase shifters distributed over a planar surface is presented, where the topology of each SPS is based on the design of a class of bandpass frequency selective surfaces composed entirely of sub-wavelength, non-resonant periodic structures.
Abstract: We present a new technique for designing low-profile planar microwave lenses. The proposed lenses consist of numerous miniature spatial phase shifters distributed over a planar surface. The topology of each spatial phase shifter (SPS) is based on the design of a class of bandpass frequency selective surfaces composed entirely of sub-wavelength, non-resonant periodic structures. A procedure for designing the proposed lenses and their constituting spatial phase shifters is also presented in the paper. This design procedure is applied to two different planar lenses operating at X-band. Each lens is a low-profile structure with an overall thickness of 0.08λ0 and uses sub-wavelength SPSs with dimensions of 0.2λ0 × 0.2λ0, where λ0 is the free-space wavelength at 10 GHz. These prototypes are fabricated and experimentally characterized using a free-space measurement system and the results are reported in the paper. The fabricated prototypes demonstrate relatively wide bandwidths of approximately 20%. Furthermore, the lenses demonstrate stable responses when illuminated under oblique angles of incidence. This feature is of practical importance if these lenses are to be used in beam-scanning antenna applications.
TL;DR: A new domain decomposition method (DDM) is introduced for the IE solution of EM wave scattering from non-penetrable objects and it provides a computationally efficient and effective preconditioner for theIE matrix equations.
Abstract: The integral equation (IE) method is commonly utilized to model time-harmonic electromagnetic (EM) problems. One of the greatest challenges in its applications arises in the solution of the resulting ill-conditioned matrix equation. We introduce a new domain decomposition method (DDM) for the IE solution of EM wave scattering from non-penetrable objects. The proposed method is a non-overlapping/non-conformal DDM and it provides a computationally efficient and effective preconditioner for the IE matrix equations. Moreover, the proposed approach is very suitable for dealing with multi-scale electromagnetic problems since each sub-domain has its own characteristics length and will be meshed independently. Furthermore, for each sub-domain, we are free to choose the most effective IE sub-domain solver based on its local geometrical features and electromagnetic characteristics. Additionally, the multilevel fast multi-pole algorithm (MLFMA) is utilized to accelerate the computations of couplings between sub-domains. Numerical results demonstrate that the proposed method yields rapid convergence in the outer Krylov iterative solution process. Finally, simulations of several large-scale examples testify to the effectiveness and robustness of the proposed IE based DDM.
TL;DR: The design procedure, realization and measurements of an implantable radiator for telemetry applications, inserted in a body phantom, is presented and a good correspondence with theoretical predictions is registered.
Abstract: The design procedure, realization and measurements of an implantable radiator for telemetry applications are presented. First, free space analysis allows the choice of the antenna typology with reduced computation time. Subsequently the antenna, inserted in a body phantom, is designed to take into account all the necessary electronic components, power supply and bio-compatible insulation so as to realize a complete implantable device. The conformal design has suitable dimensions for subcutaneous implantation (10 × 32.1 mm). The effect of different body phantoms is discussed. The radiator works in both the Medical Device Radiocommunication Service (MedRadio, 401-406 MHz) and the Industrial, Scientific and Medical (ISM, 2.4-2.5 GHz) bands. Simulated maximum gains attain -28.8 and - 18.5 dBi in the two desired frequency ranges, respectively, when the radiator is implanted subcutaneously in a homogenous cylindrical body phantom (80 × 110 mm) with muscle equivalent dielectric properties. Three antennas are realized and characterized in order to improve simulation calibration, electromagnetic performance, and to validate the repeatability of the manufacturing process. Measurements are also presented and a good correspondence with theoretical predictions is registered.
TL;DR: In this paper, four compact asymmetric-slit microstrip antennas were proposed and studied for circular polarization by cutting asymmetrical slits in diagonal directions onto the square microstrip patches, the single coaxial feed microstrip patch antennas were realized for circularly polarized radiation with compact antenna size.
Abstract: Four compact asymmetric-slit microstrip antennas are proposed and studied for circular polarization. By cutting asymmetrical slits in diagonal directions onto the square microstrip patches, the single coaxial-feed microstrip patch antennas are realized for circularly polarized radiation with compact antenna size. The performances of the proposed antennas with several asymmetric-slit shapes onto the patch radiators are compared. The measured 10-dB return loss and 3-dB axial-ratio bandwidths of the antenna prototype are around 2.5% and 0.5%, respectively. The proposed asymmetric-slit configurations are useful for compact circularly polarized microstrip patch antennas and array design.
TL;DR: This communication presents a new antenna system designed for cognitive radio applications that has been simulated with the driving motor being taken into consideration and a good agreement is found between the simulated and the measured antenna radiation properties.
Abstract: This communication presents a new antenna system designed for cognitive radio applications. The antenna structure consists of a UWB antenna and a frequency reconfigurable antenna system. The UWB antenna scans the channel to discover “white space” frequency bands while tuning the reconfigurable section to communicate within these bands. The frequency agility is achieved via a rotational motion of the antenna patch. The rotation is controlled by a stepper motor mounted on the back of the antenna structure. The motor's rotational motion is controlled by LABVIEW on a computer connected to the motor through its parallel port. The computer's parallel port is connected to a NPN Darlington array that is used to drive the stepper motor. The antenna has been simulated with the driving motor being taken into consideration. A good agreement is found between the simulated and the measured antenna radiation properties.
TL;DR: In this paper, several linearlypolarized and circularly-polarised transmit-arrays are designed and demonstrated in the 60 GHz band and a theoretical analysis is presented for the optimization of the power budget with respect to the F/D ratio.
Abstract: Several linearly-polarized and circularly-polarized transmit-arrays are designed and demonstrated in the 60-GHz band. These arrays have a fairly simple structure with three metal layers and are fabricated with a standard printed-circuit board technology. The simulation method is based on an electromagnetic model of the focal source and the unit-cells, associated to an analytical modeling of the full structure. A theoretical analysis is presented for the optimization of the power budget with respect to the F/D ratio. Several prototypes are designed and characterized in V-band. The experimental results are in very good agreement with the simulations and demonstrate very satisfactory characteristics. Power efficiencies of 50-61% are reached with a 1-dB gain bandwidth up to 7%, and low cross-polarization level.
TL;DR: The main purpose of the System Fidelity Factor (SFF) is to incorporate frequency and time domain characteristics of an antenna system into a comparison method for ultrawideband (UWB) antennas.
Abstract: The main purpose of the System Fidelity Factor (SFF) is to incorporate frequency and time domain characteristics of an antenna system into a comparison method for ultrawideband (UWB) antennas. The SFF is an interesting tool because both simulations and measurements can be done in a simple and straight-forward manner. Simulations of a single antenna are combined into a two-antennas system analysis by means of a simple post-processing, where the transfer function of the transmitting and receiving antennas are calculated. Measurements of the SFF are done using a two port Vector Network Analyzer (VNA). The polar representation of the SFF allows an equitable comparison between antennas. The procedure to derive the SFF is described in detail in the paper. Two examples are given where the UWB performance of three antenna systems are compared. In the first example antenna systems of two identical monopoles are studied. In the second example the transmitting antenna is a Vivaldi and the receiving antenna a monopole.
TL;DR: In this article, the authors present ultra broadband channel measurements at 300 GHz for two distinct indoor scenarios, a point-to-point link of devices on a desktop and the connection of a laptop to an access point in the middle of an office room.
Abstract: Ultrabroadband Terahertz communication systems are expected to help satisfy the ever-growing need for unoccupied bandwidth. Here, we present ultra broadband channel measurements at 300 GHz for two distinct indoor scenarios, a point-to-point link of devices on a desktop and the connection of a laptop to an access point in the middle of an office room. In the first setup, measurements are taken with regard to distance, different antenna types and device displacements. Additionally, an interference constellation according to the two-ray model is examined. In the second setup, the focus is on the detection and characterization of the LOS- and the NLOS-paths in an indoor environment, including a maximum of two reflections. Temporal channel characteristics are examined with regard to maximum achievable symbol rates. Furthermore, ray obstruction due to objects in the transmission path is investigated.
TL;DR: The co-design approach for the integration of filter and antenna is introduced and the proposed structure provides good design accuracy and filter skirt selectivity as compared to the filter simple cascade with antenna and a bandpass filter of the same order.
Abstract: Synthesis and design of a new printed filtering antenna is presented in this communication. For the requirements of efficient integration and simple fabrication, the co-design approach for the integration of filter and antenna is introduced. The printed inverted-L antenna and the parallel coupled microstrip line sections are used for example to illustrate the synthesis of a bandpass filtering antenna. The equivalent circuit model for the inverted-L antenna, which is mainly a series RLC circuit, is first established. The values of the corresponding circuit components are then extracted by comparing with the full-wave simulation results. The inverted-L antenna here performs not only a radiator but also the last resonator of the bandpass filter. A design procedure is given, which clearly indicates the steps from the filter specifications to the implementation. As an example, a 2.45 GHz third-order Chebyshev bandpass filter with 0.1 dB equal-ripple response is tackled. Without suffering more circuit area, the proposed structure provides good design accuracy and filter skirt selectivity as compared to the filter simple cascade with antenna and a bandpass filter of the same order. The measured results, including the return loss, total radiated power, and radiation gain versus frequency, agree well with the designed ones.
TL;DR: The results of the two electromagnetics design problems illustrate the ability of CMA-ES to provide a robust, fast and user-friendly alternative to more conventional optimization strategies such as PSO.
Abstract: A new method of optimization recently made popular in the evolutionary computation (EC) community is introduced and applied to several electromagnetics design problems. First, a functional overview of the covariance matrix adaptation evolutionary strategy (CMA-ES) is provided. Then, CMA-ES is critiqued alongside a conventional particle swarm optimization (PSO) algorithm via the design of a wideband stacked-patch antenna. Finally, the two algorithms are employed for the design of small to moderate size aperiodic ultrawideband antenna array layouts (up to 100 elements). The results of the two electromagnetics design problems illustrate the ability of CMA-ES to provide a robust, fast and user-friendly alternative to more conventional optimization strategies such as PSO. Moreover, the ultrawideband array designs that were created using CMA-ES are seen to exhibit performances surpassing the best examples that have been reported in recent literature.
TL;DR: In this article, a metamaterial-inspired low-profile patch antenna is proposed and studied for circularly-polarized (CP) radiation, which is realized by exciting two orthogonally polarized modes simultaneously which are located in the left-handed region.
Abstract: A metamaterial-inspired low-profile patch antenna is proposed and studied for circularly-polarized (CP) radiation. The present antenna, which has a single-fed configuration, is loaded with the composite right/left-handed (CRLH) mushroom-like structures and a reactive impedance surface (RIS) for miniaturization purpose. The CP radiation is realized by exciting two orthogonally-polarized modes simultaneously which are located in the left-handed (LH) region. The detailed antenna radiation characteristics are examined and illustrated with both simulated and experimental results. The CP performance can be controlled in several different ways. This antenna exhibits an overall size of 0.177λ0 × 0.181λ0 × 0.025λ0 at 2.58 GHz and a radiation efficiency around 72%. Finally, based on the proposed CP patch antenna, a compact dual-band dual linearly-polarized patch antenna has also been designed and fabricated. Promising experimental results are observed.
TL;DR: It is found that effective adaptive matching can be easily achieved by tracking the split resonant frequency of a wireless power transfer system, and a modified frequency tracking method is proposed to extend the range over which the power is transmitted with high efficiency.
Abstract: Adaptive matching methods for a wireless power transfer system in the near-field region are investigated. The impedance and resonant frequency characteristic of a near-field power transfer system are analyzed according to coupling distance. In the near-field region, adaptive matching is necessary to achieve an effective power transfer. We compare the power transfer efficiencies of several schemes including simultaneous conjugate matching and frequency tracking. It is found that effective adaptive matching can be easily achieved by tracking the split resonant frequency. In addition, a modified frequency tracking method is proposed to extend the range over which the power is transmitted with high efficiency. The experimental results are in agreement with the theoretical results.
TL;DR: A flexible folded slot dipole implantable antenna operating in the Industrial, Scientific, and Medical (ISM) band (2.4-2.4835 GHz) for biomedical applications is presented in this paper.
Abstract: We present a flexible folded slot dipole implantable antenna operating in the Industrial, Scientific, and Medical (ISM) band (2.4-2.4835 GHz) for biomedical applications. To make the designed antenna suitable for implantation, it is embedded in biocompatible Polydimethylsiloxane (PDMS). The antenna was tested by immersing it in a phantom liquid, imitating the electrical properties of the human muscle tissue. A study of the sensitivity of the antenna performance as a function of the dielectric parameters of the environment in which it is immersed was performed. Simulations and measurements in planar and bent state demonstrate that the antenna covers the complete ISM band. In addition, Specific Absorption Rate (SAR) measurements indicate that the antenna meets the required safety regulations.
TL;DR: In this paper, a novel phased array is presented to extend array scanning range by using pattern reconfigurable antenna elements and weighted thinned synthesis technology, which is capable of reconfiguring its patterns from broadside to quasi-endfire radiation by shifting states of PIN diode switches integrated on parasitic strips.
Abstract: A novel phased array is presented to extend array scanning range by using pattern reconfigurable antenna elements and weighted thinned synthesis technology in this paper. The pattern reconfigurable microstrip Yagi antenna element is used as a basic element in array and it is capable of reconfiguring its patterns from broadside to quasi-endfire radiation by shifting states of the PIN diode switches integrated on parasitic strips. A weighted thinned linear array synthesis technique is analyzed and some interesting conclusions have been made. A linear array composed of eight pattern reconfigurable antenna elements is manufactured to demonstrate the excellent performance of the array. The active element pattern of each element is measured and pre-stored. Based on active element patterns and weighted thinned linear array synthesis technique, the pattern scanning performance of the novel array is synthesized. The results indicate that the array can scan its main beam from φ = -60° to φ = 60° in H-plane with gain fluctuation less than 3 dB while maintaining low side lobes, and the -3 dB beam width coverage is about from φ = -68° to φ = 68°. The performance is superior to the traditional phased array made of wide-beam elements.
TL;DR: A technique for array diagnosis using a small number of measured data acquired by a near-field system is proposed, which gives satisfactory results in terms of failure detection with a reduction in the number of data of two orders of magnitudes compared to standard back-propagation technique and of one order of magnitude compared to thenumber of elements of the array.
Abstract: A technique for array diagnosis using a small number of measured data acquired by a near-field system is proposed. The technique, inspired by some recent results in the field of compressed sensing, requires the preliminary measurement of a failure-free reference array. The linear system relating the difference between the field measured using the reference array and the field radiated by the array under test, and the difference between the coefficients of the reference and of the AUT array, is solved using a proper regularization procedure. Numerical examples confirm that the technique gives satisfactory results in terms of failure detection with a reduction in the number of data of two orders of magnitudes compared to standard back-propagation technique and of one order of magnitude compared to the number of elements of the array, provided that the number of fault elements is small. This result is relevant in practical applications, since the high cost of large array diagnosis in near-field facilities is mainly caused by the time required for the data acquisition. Accordingly, the technique is particularly suitable for routine testing of arrays.
TL;DR: In this article, a compact coplanar waveguide (CPW)-fed zeroth-order resonant (ZOR) antennas are designed on a CPW single layer where vias are not required.
Abstract: This paper presents the design and analysis of compact coplanar waveguide (CPW)-fed zeroth-order resonant (ZOR) antennas. They are designed on a CPW single layer where vias are not required. The ZOR phenomenon is employed to reduce the antenna size. The novel composite right/left-handed (CRLH) unit cell on a vialess single layer simplifies the fabrication process. In addition, the CPW geometry provides high design freedom, so that bandwidth-extended ZOR antennas can be designed. The antenna's bandwidth is characterized by the circuit parameters. Based on the proposed bandwidth extension technique, symmetric, asymmetric, and chip-loaded antennas are designed. The ZOR characteristic and bandwidth extension are verified by a commercial EM simulator. Their performances are compared with those of previously reported metamaterial resonant antennas. They provide further size reduction, higher efficiency, easier manufacturing, and extended bandwidth.
TL;DR: In this article, a novel printed crossed dipole with broad axial ratio (AR) bandwidth is proposed, which consists of two dipoles crossed through a 90°phase delay line, which produces one minimum AR point due to the sequentially rotated configuration.
Abstract: A novel printed crossed dipole with broad axial ratio (AR) bandwidth is proposed. The proposed dipole consists of two dipoles crossed through a 90°phase delay line, which produces one minimum AR point due to the sequentially rotated configuration and four parasitic loops, which generate one additional minimum AR point. By combining these two minimum AR points, the proposed dipole achieves a broadband circularly polarized (CP) performance. The proposed antenna has not only a broad 3 dB AR bandwidth of 28.6% (0.75 GHz, 2.25-3.0 GHz) with respect to the CP center frequency 2.625 GHz, but also a broad impedance bandwidth for a voltage standing wave ratio (VSWR) ≤2 of 38.2% (0.93 GHz, 1.97-2.9 GHz) centered at 2.435 GHz and a peak CP gain of 8.34 dBic. Its arrays of 1 t 2 and 2 t 2 arrangement yield 3 dB AR bandwidths of 50.7% (1.36 GHz, 2-3.36 GHz) with respect to the CP center frequency, 2.68 GHz, and 56.4% (1.53 GHz, 1.95-3.48 GHz) at the CP center frequency, 2.715 GHz, respectively. This paper deals with the designs and experimental results of the proposed crossed dipole with parasitic loop resonators and its arrays.