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Showing papers in "International Journal of Antennas and Propagation in 2017"


Journal ArticleDOI
TL;DR: In this paper, the authors present an introduction and evolution of DGS and how DGS is different from former technologies: PBG and EBG, and several theoretical techniques for analysing the Defected Ground Structure are discussed.
Abstract: Slots or defects integrated on the ground plane of microwave planar circuits are referred to as Defected Ground Structure. DGS is adopted as an emerging technique for improving the various parameters of microwave circuits, that is, narrow bandwidth, cross-polarization, low gain, and so forth. This paper presents an introduction and evolution of DGS and how DGS is different from former technologies: PBG and EBG. A basic concept behind the DGS technology and several theoretical techniques for analysing the Defected Ground Structure are discussed. Several applications of DGS in the field of filters, planar waveguides, amplifiers, and antennas are presented.

273 citations


Journal ArticleDOI
TL;DR: In this paper, a comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented.
Abstract: A comprehensive review concerning the geometry, the manufacturing technologies, the materials, and the numerical techniques, adopted for the analysis and design of wideband and ultrawideband (UWB) antennas for wireless applications, is presented. Planar, printed, dielectric, and wearable antennas, achievable on laminate (rigid and flexible), and textile dielectric substrates are taken into account. The performances of small, low-profile, and dielectric resonator antennas are illustrated paying particular attention to the application areas concerning portable devices (mobile phones, tablets, glasses, laptops, wearable computers, etc.) and radio base stations. This information provides a guidance to the selection of the different antenna geometries in terms of bandwidth, gain, field polarization, time-domain response, dimensions, and materials useful for their realization and integration in modern communication systems.

106 citations


Journal ArticleDOI
TL;DR: Two different methods for wearable antenna fabrication are described in detail: the first resorts to the combined use of nonwoven conductive fabrics and of a cutting plotter for shaping the fabric, whereas the second considered fabrication method resorts toThe embroidery of conductive threads.
Abstract: Remote monitoring of the elderly in telehealth applications requires that the monitoring must not affect the elderly’s regular habits. To ensure this requirement, the components (i.e., sensor and antenna) necessary to carry out such monitoring should blend in with the elderly’s daily routine. To this end, an effective strategy relies on employing wearable antennas that can be fully integrated with clothes and that can be used for remotely transmitting/receiving the sensor data. Starting from these considerations, in this work, two different methods for wearable antenna fabrication are described in detail: the first resorts to the combined use of nonwoven conductive fabrics and of a cutting plotter for shaping the fabric, whereas the second considered fabrication method resorts to the embroidery of conductive threads. To demonstrate the suitability of the considered fabrication techniques and to highlight their pros and cons, numerical and experimental results related to different wearable antennas are also reported and commented on. Results demonstrate that the presented fabrication techniques and strategies are very flexible and can be used to obtain low-cost wearable antennas with performance tailored for the specific application at hand.

54 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a review of antennas suitable for picosatellite applications, including material and antenna topologies which have been used prior to the presentation of several deployable configurations.
Abstract: Cube Satellite (CubeSat) technology is an attractive emerging alternative to conventional satellites in radio astronomy, earth observation, weather forecasting, space research, and communications. Its size, however, poses a more challenging restriction on the circuitry and components as they are expected to be closely spaced and very power efficient. One of the main components that will require careful design for CubeSats is their antennas, as they are needed to be lightweight, small in size, and compact or deployable for larger antennas. This paper presents a review of antennas suitable for picosatellite applications. An overview of the applications of picosatellites will first be explained, prior to a discussion on their antenna requirements. Material and antenna topologies which have been used will be subsequently discussed prior to the presentation of several deployable configurations. Finally, a perspective and future research work on CubeSat antennas will be discussed in the conclusion.

50 citations


Journal ArticleDOI
TL;DR: Experimental results show that EFPA algorithm provides enhanced performance in terms of side lobe suppression and null control compared to FPA and other popular algorithms.
Abstract: In this paper, a new variant of flower pollination algorithm (FPA), namely, enhanced flower pollination algorithm (EFPA), has been proposed for the pattern synthesis of nonuniform linear antenna arrays (LAA). The proposed algorithm uses the concept of Cauchy mutation in global pollination and enhanced local search to improve the exploration and exploitation tendencies of FPA. It also uses dynamic switching to control the rate of exploration and exploitation. The algorithm is tested on standard benchmark problems and has been compared statistically with state of the art to prove its worthiness. LAA design is a tricky and difficult electromagnetic problem. Hence to check the efficacy of the proposed algorithm it has been used for synthesis of four different LAA with different sizes. Experimental results show that EFPA algorithm provides enhanced performance in terms of side lobe suppression and null control compared to FPA and other popular algorithms.

44 citations


Journal ArticleDOI
TL;DR: In this paper, four sensing approaches for the implementation of microwave sensors based on transmission lines loaded with metamaterial-inspired resonators are considered, and examples of applications are pointed out.
Abstract: Four sensing approaches for the implementation of microwave sensors based on transmission lines loaded with metamaterial-inspired resonators are considered in this review paper, and examples of applications are pointed out. In all the cases, sensing is based on the effects that the magnitude under measurement causes in the transmission properties of the resonator-loaded line. Such four strategies are (i) resonance frequency variation, (ii) coupling modulation through symmetry disruption (causing variation of the notch depth), (iii) frequency splitting (also exploiting symmetry properties), and (iv) amplitude modulation of a harmonic signal. Such sensors are useful in various scenarios, of interest in fields as diverse as characterization of dielectric materials for communication circuits, medical diagnosis and treatment with microwave technologies, and sensors for space applications, among others.

38 citations


Journal ArticleDOI
TL;DR: In this paper, the power law coefficients were determined to support the estimation of specific attenuation from the knowledge of rain rate at Ku and Ka bands for Koreasat 6 and COMS1 in South Korea.
Abstract: The attenuation induced by rain is prominent in the satellite communication at Ku and Ka bands. The paper studied the empirical determination of the power law coefficients which support the calculation of specific attenuation from the knowledge of rain rate at Ku and Ka band for Koreasat 6 and COMS1 in South Korea that are based on the three years of measurement. Rain rate data was measured through OTT Parsivel which shows the rain rate of about 50 mm/hr and attenuation of 10.7, 11.6, and 11.3 dB for 12.25, 19.8, and 20.73 GHz, respectively, for 0.01% of the time for the combined values of rain rate and rain attenuation statistics. Comparing with the measured data illustrates the suitability for estimation of signal attenuation in Ku and Ka band whose validation is done through the comparison with prominent rain attenuation models, namely, ITU-R P.618-12 and ITU-R P. 838-3 with the use of empirically determined coefficient sets. The result indicates the significance of the ITU-R recommended regression coefficients of rain specific attenuation. Furthermore, the overview of predicted year-wise rain attenuation estimation for Ka band in the same link as well as different link is studied which is obtained from the ITU-R P. 618-12 frequency scaling method.

36 citations


Journal ArticleDOI
TL;DR: In this article, a compact circularly polarized antenna operating at 915MHz industrial, scientific, and medical (ISM) band for biomedical implantable applications is presented and experimentally measured.
Abstract: A compact circularly polarized antenna operating at 915 MHz industrial, scientific, and medical (ISM) band for biomedical implantable applications is presented and experimentally measured. The proposed antenna can be miniaturized to a large extent with the compact size of 15 × 15 × 1.27 mm3 by means of loading patches to a ring-shaped microstrip patch antenna. An impedance bandwidth of 10.6% (865–962 MHz) for reflection coefficient less than −10 dB can be obtained. Meanwhile, the simulated 3 dB axial-ratio (AR) bandwidth reaches 14 MHz. Finally, the optimized design was fabricated and tested, and the measured results agree well with simulated results.

35 citations


Journal ArticleDOI
TL;DR: In this article, a new method based on the energy function detection and band-pass filtering is proposed to suppress the ISRJ, which mainly consist of two parts: extracting the signal segments without ISR jammers and constructing bandpass filtering function with low sidelobe.
Abstract: Interrupted-sampling repeater jamming (ISRJ) is a new kind of coherent jamming to the large time-bandwidth linear frequency modulation (LFM) signal. Many jamming modes, such as lifelike multiple false targets and dense false targets, can be made through setting up different parameters. According to the “storage-repeater-storage-repeater” characteristics of the ISRJ and the differences in the time-frequency-energy domain between the ISRJ signal and the target echo signal, one new method based on the energy function detection and band-pass filtering is proposed to suppress the ISRJ. The methods mainly consist of two parts: extracting the signal segments without ISRJ and constructing band-pass filtering function with low sidelobe. The simulation results show that the method is effective in the ISRJ with different parameters.

33 citations


Journal ArticleDOI
TL;DR: In this article, the authors give a chronical review of the 3D printing technology from the time it was invented and suggest specific modeling of the surface roughness of 3D printed devices.
Abstract: The 3D printing technology is catching attention nowadays. It has certain advantages over the traditional fabrication processes. We give a chronical review of the 3D printing technology from the time it was invented. This technology has also been used to fabricate millimeter-wave (mmWave) and terahertz (THz) passive devices. Though promising results have been demonstrated, the challenge lies in the fabrication tolerance improvement such as dimensional tolerance and surface roughness. We propose the design methodology of high order device to circumvent the dimensional tolerance and suggest specific modelling of the surface roughness of 3D printed devices. It is believed that, with the improvement of the 3D printing technology and related subjects in material science and mechanical engineering, the 3D printing technology will become mainstream for mmWave and THz passive device fabrication.

33 citations


Journal ArticleDOI
TL;DR: In this paper, a wearable passive UHF RFID tag based on a slotted patch antenna comprising only textile materials (e-textile, textile substrate, and conductive yearn) is presented.
Abstract: We present a wearable passive UHF RFID tag based on a slotted patch antenna comprising only textile materials (e-textile, textile substrate, and conductive yearn). As a novel manufacturing approach, we realize the patch-to-ground and antenna-to-IC interfaces using only conductive thread and a sewing machine. We outline the electromagnetic optimization of the antenna for body-worn operation through simulations and present a performance comparison between the e-textile tag and a tag produced using regular electronics materials and methods. The measured results show that the textile tag achieves the electrical performance required in practical applications and that the slotted patch type antenna provides stable electromagnetic performance in different body-worn configurations.

Journal ArticleDOI
TL;DR: The proposed RF fingerprint method based on multidimension permutation entropy can achieve higher classification accuracy than that of the other two steady-state methods, and its performance under different SNR is evaluated from experimental data.
Abstract: Radio frequency fingerprint (RF fingerprint) extraction is a technology that can identify the unique radio transmitter at the physical level, using only external feature measurements to match the feature library. RF fingerprint is the reflection of differences between hardware components of transmitters, and it contains rich nonlinear characteristics of internal components within transmitter. RF fingerprint technique has been widely applied to enhance the security of radio frequency communication. In this paper, we propose a new RF fingerprint method based on multidimension permutation entropy. We analyze the generation mechanism of RF fingerprint according to physical structure of radio transmitter. A signal acquisition system is designed to capture the signals to evaluate our method, where signals are generated from the same three Anykey AKDS700 radios. The proposed method can achieve higher classification accuracy than that of the other two steady-state methods, and its performance under different SNR is evaluated from experimental data. The results demonstrate the effectiveness of the proposal.

Journal ArticleDOI
TL;DR: In this paper, an improved reflectarray phase-only synthesis technique which employs the generalized intersection approach (IA) algorithm is described, which is formulated with the First Principle of Equivalence and takes into account a dielectric frame which is usually present to screw the reflectarray breadboard to the supporting structure.
Abstract: An improved reflectarray Phase-Only Synthesis technique which employs the generalized Intersection Approach (IA) algorithm is fully described It is formulated with the First Principle of Equivalence and takes into account a dielectric frame which is usually present to screw the reflectarray breadboard to the supporting structure The effects of the First Principle of Equivalence versus the Second Principle in the computation of the radiation patterns, as well as the dielectric frame, are assessed and taken into account in an efficient implementation of the generalized IA in order to obtain more accurate results Different strategies to speed up the synthesis process are presented and to improve convergence The technique is demonstrated through two examples for space and terrestrial applications: an isoflux pattern for global Earth coverage from a satellite and a Local Multipoint Distribution Service pattern for central stations of cellular systems, both with a working frequency of 255 GHz In addition, experimental results validate the approach described in this work with a prototype with an isoflux pattern working at 30 GHz

Journal ArticleDOI
TL;DR: In this paper, a triple-band electric metamaterial resonator (TBEMR) based on integration of open delta loops within square ring resonator was proposed. But the authors did not investigate the effect of the resonant frequency on the transmission and reflection response of the proposed subwavelength resonator.
Abstract: We report a new design of triple-band electric metamaterial resonator (TBEMR) based on integration of open delta loops within square ring resonator. This metamaterial resonator has three distinct -negative regions (ENG) over C, X frequency bands. The transmission and reflection response of the proposed subwavelength resonator is analyzed using full-wave electromagnetic solver Ansys HFSS to demonstrate the presence of electrical resonances within frequencies 4–12 GHz. Effective medium parameters permittivity and permeability are extracted from simulated complex scattering parameters to verify existence of ENG regions. The investigations are also carried out regarding dependence of resonant frequencies on design parameters of the TBEMR unit cell. The effective medium ratio for proposed subwavelength resonator is compared with various other metamaterial resonators to indicate its compact nature.

Journal ArticleDOI
TL;DR: In this article, the authors proposed a multiband PIFA (Planar Inverted-F Antenna) for mobile phones with four slots integrated in the radiating patch and ground plane.
Abstract: A new compact multiband PIFA (Planar Inverted-F Antenna) for mobile handset is proposed in this article. The proposed PIFA has a simple geometry with four slots integrated in the radiating patch and ground plane. The PIFA occupies a small volume of 51 × 14 × 7.2 mm3 and is placed on the top portion of mobile phone. The optimized PIFA is worked in the 790 MHz band (737–831 MHz), the 1870 MHz band (1794–1977 MHz), the 2550 MHz band (2507–2615 MHz), and the 3400 MHz band (3341–3545 MHz), to cover LTE700, LTE800, DCS1800, PCS1900, LTE1800, LTE1900, LTE2500, and WIMAX3400 bands. Each of the four operating bands can be controlled independently by the variation of a single parameter of the proposed design, with a wide control range. An omnidirectional radiation pattern to each resonant frequency is obtained with a maximum gain of 2.15 dBi at 790 MHz, 3.99 dBi at 1870 MHz, 4.57 dBi at 2550 MHz, and 6.43 dBi at 3400 MHz. The proposed PIFA is studied in the free space and in the presence of other mobile phone components such as the battery, LCD (liquid crystal display), camera, microphone, speaker, buttons, and a plastic housing. The distribution of specific absorption rate for both European and American standards for each operating band and at various distances between the antenna and the human head is also studied.

Journal ArticleDOI
TL;DR: In this paper, two model-based inversion algorithms are exploited to tackle the imaging task, and their integration improves the quality of the overall tracking of the variations occurring in the target and surrounding regions.
Abstract: Microwave thermal ablation is a cancer treatment that exploits local heating caused by a microwave electromagnetic field to induce coagulative necrosis of tumor cells. Recently, such a technique has significantly progressed in the clinical practice. However, its effectiveness would dramatically improve if paired with a noninvasive system for the real-time monitoring of the evolving dimension and shape of the thermally ablated area. In this respect, microwave imaging can be a potential candidate to monitor the overall treatment evolution in a noninvasive way, as it takes direct advantage from the dependence of the electromagnetic properties of biological tissues from temperature. This paper explores such a possibility by presenting a proof of concept validation based on accurate simulated imaging experiments, run with respect to a scenario that mimics an ex vivo experimental setup. In particular, two model-based inversion algorithms are exploited to tackle the imaging task. These methods provide independent results in real-time and their integration improves the quality of the overall tracking of the variations occurring in the target and surrounding regions.

Journal ArticleDOI
TL;DR: A novel interpolation-free imaging algorithm based on wavefront reconstruction theory is proposed with the advantages of low computational cost and high precision and results show that accurate 3D image can be generated at a very high speed by utilizing the proposed algorithm.
Abstract: Three-dimensional (3D) microwave imaging has been proven to be well suited for concealed weapon detection application. For the 3D image reconstruction under two-dimensional (2D) planar aperture condition, most of current imaging algorithms focus on decomposing the 3D free space Green function by exploiting the stationary phase and, consequently, the accuracy of the final imagery is obtained at a sacrifice of computational complexity due to the need of interpolation. In this paper, from an alternative viewpoint, we propose a novel interpolation-free imaging algorithm based on wavefront reconstruction theory. The algorithm is an extension of the 2D range stacking algorithm (RSA) with the advantages of low computational cost and high precision. The algorithm uses different reference signal spectrums at different range bins and then forms the target functions at desired range bin by a concise coherent summation. Several practical issues such as the propagation loss compensation, wavefront reconstruction, and aliasing mitigating are also considered. The sampling criterion and the achievable resolutions for the proposed algorithm are also derived. Finally, the proposed method is validated through extensive computer simulations and real-field experiments. The results show that accurate 3D image can be generated at a very high speed by utilizing the proposed algorithm.

Journal ArticleDOI
TL;DR: In this article, a review of different technologies used to implement near-field focused antennas at the microwave frequency band up to a few tens of GHz is provided, including arrays of microstrip patches and printed dipoles, arrays of dielectric resonator antennas, reflectarrays, transmit antennas, transmit arrays, Fresnel zone plate lenses, leaky-wave antennas and waveguide arrays.
Abstract: This paper provides a review spanning different technologies used to implement near-field focused antennas at the microwave frequency band up to a few tens of GHz: arrays of microstrip patches and printed dipoles, arrays of dielectric resonator antennas, reflectarrays, transmitarrays, Fresnel zone plate lenses, leaky-wave antennas, and waveguide arrays.

Journal ArticleDOI
TL;DR: In this article, a compact frequency reconfigurable circular patch antenna with an arc-shaped slot loaded in the ground layer is proposed for multiband wireless communication applications, which can operate from 1.82 GHz to 2.46 GHz in DCS1800 (1.71-1.88 GHz) frequency bands.
Abstract: In this paper, a compact frequency reconfigurable circular patch antenna with an arc-shaped slot loaded in the ground layer is proposed for multiband wireless communication applications. By controlling the ON/OFF states of the five PIN diodes mounted on the arc-shaped slot, the effective length of the arc-shaped slot and the effective length of antennas current are changed, and accordingly six-frequency band reconfiguration can be achieved. The simulated and measured results show that the antenna can operate from 1.82 GHz to 2.46 GHz, which is located in DCS1800 (1.71–1.88 GHz), UMTS (2.11–2.20 GHz), WiBro (2.3–2.4 GHz), and Bluetooth (2.4–2.48 GHz) frequency bands and so forth. Compared to the common rectangular slot circular patch antenna, the proposed arc-shaped slot circular patch antenna not only has a better rotational symmetry with the circular patch and substrate but also has more compact size. For the given operating frequency at 1.82 GHz, over 55% area reduction is achieved in this design with respect to the common design with rectangular slot. Since the promising frequency reconfiguration, this antenna may have potential applications in modern multiband and multifunctional mobile communication systems.

Journal ArticleDOI
TL;DR: In this paper, an optically transparent antenna with directional radiation pattern is proposed, which consists of a radiation patch above the transparent glass substrate and a frequency selective surface acting as the ground of microstrip antenna on the back of the glass.
Abstract: An optically transparent antenna with directional radiation pattern is proposed in this paper. This antenna consists of a radiation patch above the transparent glass substrate and a frequency selective surface acting as the ground of microstrip antenna on the back of the glass. The frequency selective surface (FSS) performs well as ground in the working frequency range to achieve directional radiation pattern. A SMA connector is used to feed the antenna. The antenna can operate at the on-board dedicated short-range communication band from 5.725 GHz to 5.85 GHz. Simulations and measurements are carried out to study the antenna performances in terms of impedance matching, gain, and radiation patterns. Both of the simulation and measurement results are shown to illustrate the good performance of the proposed antenna. It is very suitable for car network communication scene.

Journal ArticleDOI
TL;DR: In this article, a 3D direct-write dispensing in the fabrication of passive UHF RFID graphene tags on a textile substrate is presented, where the tag antenna is deposited directly on top of the IC strap, in order to simplify the manufacturing process by removing one step, that is, the IC attachment with conductive glue.
Abstract: We present the possibilities of 3D direct-write dispensing in the fabrication of passive UHF RFID graphene tags on a textile substrate. In our method, the graphene tag antenna is deposited directly on top of the IC strap, in order to simplify the manufacturing process by removing one step, that is, the IC attachment with conductive glue. Our wireless measurement results confirm that graphene RFID tags with printed antenna-IC interconnections achieve peak read ranges of 5.2 meters, which makes them comparable to graphene tags with epoxy-glued ICs. After keeping the tags in high humidity, the read ranges of the tags with epoxy-glued and printed antenna-IC interconnections decrease 0.8 meters and 0.5 meters, respectively. However, after drying, the performance of both types of tags returns back to normal.

Journal ArticleDOI
TL;DR: In this paper, a frequency-tracking and impedance-matching combined system is proposed to improve the robustness of wireless power transfer for embedded devices, and the characteristics of the improved WPT system are investigated theoretically based on the two-port network model.
Abstract: One of the greatest challenges to power embedded devices using magnetically coupled resonant wireless power transfer (WPT) system is that the amount of power delivered to the load is very sensitive to load impedance variations. Previous adaptive impedance-matching (IM) technologies have drawbacks because adding IM networks, relay coils, or other compensating components in the receiver-side will significantly increase the receiver size. In this paper, a novel frequency-tracking and impedance-matching combined system is proposed to improve the robustness of wireless power transfer for embedded devices. The characteristics of the improved WPT system are investigated theoretically based on the two-port network model. Simulation and experimental studies are carried out to validate the proposed system. The results suggest that the frequency-tracking and impedance-matching combined WPT system can quickly find the best matching points and maintain high power transmission efficiency and output power when the load impedance changes.

Journal ArticleDOI
TL;DR: Channel measurements and simulations may be utilized for the design of wireless communications of future 5G radio systems at 6 GHz and show that CI model with the reference distance of 1 m provides more accuracy and stability in tunnel scenarios.
Abstract: Propagation measurements of wireless channels performed in the tunnel environments at 6 GHz are presented in this paper. Propagation characteristics are simulated and analyzed based on the method of shooting and bouncing ray tracing/image (SBR/IM). A good agreement is achieved between the measured results and simulated results, so the correctness of SBR/IM method has been validated. The measured results and simulated results are analyzed in terms of path loss models, received power, root mean square (RMS) delay spread, Ricean K-factor, and angle of arrival (AOA). The omnidirectional path loss models are characterized based on close-in (CI) free-space reference distance model and the alpha-beta-gamma (ABG) model. Path loss exponents (PLEs) are 1.50–1.74 in line-of-sight (LOS) scenarios and 2.18–2.20 in non-line-of-sight (NLOS) scenarios. Results show that CI model with the reference distance of 1 m provides more accuracy and stability in tunnel scenarios. The RMS delay spread values vary between 2.77 ns and 18.76 ns. Specially, the Poisson distribution best fits the measured data of RMS delay spreads for LOS scenarios and the Gaussian distribution best fits the measured data of RMS delay spreads for NLOS scenarios. Moreover, the normal distribution provides good fits to the Ricean K-factor. The analysis of the abovementioned results from channel measurements and simulations may be utilized for the design of wireless communications of future 5G radio systems at 6 GHz.

Journal ArticleDOI
TL;DR: In this paper, the authors address the subject of electromagnetic wave scattering in layered media, and cover the recent progress achieved with different approaches, including existing theories and models, classified, and summarized on the basis of their characteristics.
Abstract: This paper addresses the subject of electromagnetic wave scattering in layered media, thus covering the recent progress achieved with different approaches. Existing theories and models are analyzed, classified, and summarized on the basis of their characteristics. Emphasis is placed on both theoretical and practical application. Finally, patterns and trends in the current literature are identified and critically discussed.

Journal ArticleDOI
TL;DR: In this paper, an antipodal Vivaldi antenna installed at a transformer's joint is designed according to the structural features of 750kV transformers in China, and several effective structures, such as linear gradient microstrip and slot edge, are employed to improve the return loss and radiation characteristics.
Abstract: In recent years, extensive research has been conducted on the ultrahigh-frequency (UHF) method. Considering that acquiring a partial discharge UHF signal is the first step in a series of tasks, such as fault diagnosis and defect location, the UHF sensor plays an important role in the UHF method. An antipodal Vivaldi antenna installed at a transformer’s joint is designed in this study according to the structural features of 750 kV transformers in China. Several effective structures, such as linear gradient microstrip and slot edge, are employed to improve the return loss and radiation characteristics. A metal box is designed after analyzing the influence of the metal around the antenna. The metal box can effectively shield against electromagnetic interference and does not deteriorate the performance of the antenna significantly. Experimental data show that this antenna is much more sensitive than the rectangular plane spiral antenna. The proposed antipodal Vivaldi antenna is suitable for detecting partial discharge in large transformers.

Journal ArticleDOI
TL;DR: In this paper, a low profile pentagonal shaped monopole antenna is designed and presented for wearable applications, which can work efficiently in free space but also on the surface of the human body.
Abstract: A low profile pentagonal shaped monopole antenna is designed and presented for wearable applications. The main objective of this paper is to design a miniaturized ultrawide band monopole planar antenna which can work efficiently in free space but also on the surface of the human body. The impact of human tissues on antenna performance is explained using the proposed pentagonal monopole antenna. The antenna is designed with a pentagonal radiator and a matched feed line of 50 ohm and square slots are integrated on defected ground of FR4 substrate with a size of 15 mm × 25 mm to achieve ultrawide band (UWB) performance in free space and human proximity. This overall design will enhance the antenna performance with wide bandwidth ranging from 2.9 GHz to 11 GHz. Specific absorption rate (SAR) of the proposed antenna on dispersive phantom model is also measured to observe the exposure of electromagnetic energy on human tissues. The simulated and measured results of the proposed antenna exhibit wide bandwidth and radiation characteristics in both free space and human proximity.

Journal ArticleDOI
TL;DR: In this article, a simple analytical method for synthesizing asymmetric side lobe pattern with a wide-angle steered null in the nonuniformly excited linear arrays is presented, where the difference in the side lobe levels on both sides of the main beam is achieved by varying just the phase excitations of the two-edge elements.
Abstract: In radar antennas, asymmetric side lobes are useful, where undesired signals such as noise and ground clutter should be minimized Also, for practical implementation, the feeding network of such antennas should be efficiently designed In this paper, a simple analytical method for synthesizing asymmetric side lobe pattern with a wide-angle steered null in the nonuniformly excited linear arrays is presented In this method, the difference in the side lobe levels on both sides of the main beam is achieved by varying just the phase excitations of the two-edge elements The major novelty of this paper lies in the fact that the required asymmetric side lobe pattern can be achieved by changing a single phase shifter resulting in a simple feeding network

Journal ArticleDOI
TL;DR: In this paper, a coplanar implant antenna was developed using full-wave electromagnetic simulator and measured in a liquid phantom mimicking the dielectric properties of the human head.
Abstract: Minimally invasive approach to intracranial pressure monitoring is desired for long-term diagnostics. The monitored pressure is transmitted outside the skull through an implant antenna. We present a new miniature (6 mm × 5 mm) coplanar implant antenna and its integration on a sensor platform to establish a far-field data link for the sensor readout at distances of 0.5 to 1 meter. The implant antenna was developed using full-wave electromagnetic simulator and measured in a liquid phantom mimicking the dielectric properties of the human head. It achieved impedance reflection coefficient better than −10 dB from 2.38 GHz to 2.54 GHz which covers the targeted industrial, scientific, and medical band. Experiments resulted in an acceptable peak gain of approximately −23 dBi. The implant antenna was submerged in the liquid phantom and interfaced to a 0.5 mW voltage controlled oscillator. To verify the implant antenna performance as a part of the ICP monitoring system, we recorded the radiated signal strength using a spectrum analyzer. Using a half-wavelength dipole as the receiving antenna, we captured approximately −58.7 dBm signal at a distance of 1 m from the implant antenna which is well above for the reader with sensitivity of −80 dBm.

Journal ArticleDOI
TL;DR: In this paper, a propagation path loss model for inland river is proposed by three improvements compared with the Round Earth Loss (REL) model for open-sea environment, which uses Okumura-Hata model in dB scale to replace the equation transformed from the free space loss in REL model; secondly, diffraction loss caused by the obstacles (e.g., large buildings, bridges, or some other facilities near the river bank) is also taken into account; mixed-path methodology as another improvement is used for Inland River (IR) model because the actual propagation environment between
Abstract: In this paper, a propagation path loss model for inland river is proposed by three improvements compared with the Round Earth Loss (REL) model for open-sea environment. Specifically, parameters optimization uses Okumura-Hata model in dB scale to replace the equation transformed from the free space loss in REL model; secondly, diffraction loss caused by the obstacles (e.g., large buildings, bridges, or some other facilities near the river bank) is also taken into account; mixed-path methodology as another improvement is used for Inland River (IR) model because the actual propagation environment between transmitter (TX) antenna and receiver (RX) antenna contains both land part and water part. The paper presents a set of 1.4 GHz measurements conducted along the Yangtze River in Wuhan. According to the comparison between path loss models and experimental results, IR model shows a good matching degree. After that, Root Mean Square Error (RMSE), Grey Relation Grade and Mean Absolute Percentage Error (GRG-MAPE), Pearson Correlation Coefficient, and Mean Absolute Percentage Error (PCC-MAPE) are employed to implement quantitative analysis. The results prove that IR model with consideration of mixed path and deterministic information is more accurate than other classic empirical propagation models for these scenarios.

Journal ArticleDOI
TL;DR: A deterministic method for the 3D synthesis of antenna arrays that jointly accounts for far-field pattern reconfigurability, polarization setting, dynamic range ratio reduction, and near-field control is proposed.
Abstract: This paper proposes a deterministic method for the 3D synthesis of antenna arrays that jointly accounts for far-field pattern reconfigurability, polarization setting, dynamic range ratio reduction, and near-field control. The conceived algorithm, which generalizes some existing solutions, relies on a weighted cost function, whose iterative minimization is accomplished by properly derived closed-form expressions. This feature, combined with the possibility of selecting the weighting parameters, provides a fast and versatile approach, whose capabilities are numerically checked by considering different synthesis problems and array structures in the presence of mutual coupling.