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A single-feed broadband quasi-isotropic antenna was designed for non-line-of-sight (NLOS) wireless sensor networks. The proposed antenna is based on a combination of fork-shaped crossed dipoles. It shows the broadband of quasi-isotropic radiation characteristics with high radiation efficiency. The electrical size ka of the proposed antenna is 0.94 with respect to its lower operating frequency. Its profile is also extremely thin at 0.0015λ. The impedance is matched from 1.8 to 4.3 GHz, or an 81.9% fractional bandwidth, whereas the maximum gain deviation ranging from 6.2 to 9.2 dB for the quasi-isotropic radiation is achieved from 1.8 to 3.6 GHz with a 10 dB criterion, which is close to the impedance bandwidth. The performance from the computed expectations is verified, as it shows a gain deviation of 8.4–9.8 dB from 1.9 to 3.3 GHz with an 80% fractional impedance bandwidth. The proposed antenna also shows good spatial coverage of circular polarization at high frequencies. Lastly, the received power level performance of the proposed antenna is tested under the NLOS condition, which shows a higher level compared to the linearly polarized, broadband omni-directional monopole antenna. [ABSTRACT FROM AUTHOR]

A single-feed broadband quasi-isotropic antenna was designed for non-line-of-sight (NLOS) wireless sensor networks. The proposed antenna is based on a combination of fork-shaped crossed dipoles. It shows the broadband of quasi-isotropic radiation characteristics with high radiation efficiency. The electrical size ka of the proposed antenna is 0.94 with respect to its lower operating frequency. Its profile is also extremely thin at 0.0015λ. The impedance is matched from 1.8 to 4.3 GHz, or an 81.9% fractional bandwidth, whereas the maximum gain deviation ranging from 6.2 to 9.2 dB for the quasi-isotropic radiation is achieved from 1.8 to 3.6 GHz with a 10 dB criterion, which is close to the impedance bandwidth. The performance from the computed expectations is verified, as it shows a gain deviation of 8.4–9.8 dB from 1.9 to 3.3 GHz with an 80% fractional impedance bandwidth. The proposed antenna also shows good spatial coverage of circular polarization at high frequencies. Lastly, the received power level performance of the proposed antenna is tested under the NLOS condition, which shows a higher level compared to the linearly polarized, broadband omni-directional monopole antenna.

This paper presents a very low-profile on-ground chip antenna with a total volume of 0.075 λ 0 × 0.056 λ 0 × 0.019 λ 0 (at f 0 = 2.4 GHz). The proposed design is a corrugated (accordion-like) planar inverted F antenna (PIFA) embedded in low-loss glass ceramic material (DuPont GreenTape 9k7 with ϵ r = 7.1 and tan δ = 0.0009) fabricated with LTCC technology. The antenna does not require a clearance area on the ground plane where the antenna is located, and it is proposed for 2.4 GHz IoT applications for extreme size-limited devices. It shows a 25 MHz impedance bandwidth (for S 11 < −6 dB), which means a relative bandwidth of 1 % ). A study in terms of matching and total efficiency is performed for several size ground planes with the antenna installed at different positions. The use of characteristic modes analysis (CMA) and the correlation between modal and total radiated fields is performed to demonstrate the optimum position of the antenna. Results show high-frequency stability and a total efficiency difference of up to 5.3 dB if the antenna is not placed at the optimum position. [ABSTRACT FROM AUTHOR]

We present electrically small, multi-band, metamaterial-inspired antennas with adequate radiation characteristics and isolation enhancement. The antenna element consists of a complementary split-ring resonator (CSRR) embedded in a small monopole that has a size of $\lambda /8\,\,\times \,\,\lambda /10$ at the lowest frequency band, while rectangular patches are placed underneath it to further improve the performance. The antenna operates at the 2.4-2.5/2.9-4.8/5.1-6.5 GHz frequency bands. Moreover, we propose a systematic, metamaterial-based approach in order to improve the isolation between two of these small, closely spaced antenna elements at the lowest and highest frequency bands. The proposed techniques reduce the coupling by up to 29 dB without increasing the size of the structure. In particular, the isolation enhancement at the highest frequency band of interest is remarkably wideband. The cable effect, which is a common concern during the measurements of small antennas, is examined as well. The proposed antennas are not only small but also densely packed and can be easily integrated with modern, compact communication devices with advanced functionality. Simulations along with experimental results validate the effectiveness of our design.

This paper presents a very low-profile on-ground chip antenna with a total volume of 0.075λ0× 0.056λ0× 0.019λ0 (at f0 = 2.4 GHz). The proposed design is a corrugated (accordion-like) planar inverted F antenna (PIFA) embedded in low-loss glass ceramic material (DuPont GreenTape 9k7 with ϵr = 7.1 and tanδ = 0.0009) fabricated with LTCC technology. The antenna does not require a clearance area on the ground plane where the antenna is located, and it is proposed for 2.4 GHz IoT applications for extreme size-limited devices. It shows a 25 MHz impedance bandwidth (for S11 < −6 dB), which means a relative bandwidth of 1%). A study in terms of matching and total efficiency is performed for several size ground planes with the antenna installed at different positions. The use of characteristic modes analysis (CMA) and the correlation between modal and total radiated fields is performed to demonstrate the optimum position of the antenna. Results show high-frequency stability and a total efficiency difference of up to 5.3 dB if the antenna is not placed at the optimum position.

This article presents the coupled shorted patch antennas (CSPAs), which exhibit dual-band operation of both broadside and conical radiation patterns and successfully overcome the major disadvantage of the large H-plane cross-polarization radiation of conventional shorted patch antennas (SPAs). The basic concept behind this breakthrough innovation is to create and explore the coupled TM0,1/2 modes. It will be shown that the CSPAs provide the horizontally polarized broadside radiation under the odd coupled TM0,1/2 mode for the low band and vertically polarized conical radiation patterns under the even coupled TM0,1/2 mode for the high band, respectively. The CSPAs have smaller resonant sizes when compared with those of the conventional SPAs for broadside radiation. The sum of the two resonant frequencies for the CSPAs is twice of that for the corresponding conventional SPAs based on a single microstrip. The ratio of two resonant frequencies depends on the odd and even mode impedances of the coupled microstrips. The calculated results are validated with the simulated and measured ones. [ABSTRACT FROM AUTHOR]

The main issue to tune controlled devices by the application of a DC magnetic field comes up against the high value of the field’s intensity required for their implementation. This work presents an implementation of magneto-dielectric materials (MDM) specifically manufactured for their integration in antenna devices operating in VHF band. The twofold objective is: (i) reduction in antenna size, (ii) frequency tuning of the antenna using a low intensity magnetic control. A notable permeability variation of MDM samples is observed when the symmetry of the lines of the control field, with an intensity less than 10 Oe, is consistent with the one of the structures in the magnetic domains. The MDM allows a miniaturization of 20% of an inverted-F antenna (IFA) antenna structure, and an agility of about 2.5% for a control field of 1.5 Oe.

Frequency-reconfigurable antennas seem a viable solution to achieve better performance and increased flexibility for integrated mobile phone antennas. Due to the lossy nature of many tunable components, the use of multiple combined tuning components in a single design seems attractive, as it can distribute the current over the components. However, many combinations of individual tuning component settings can result in an acceptable input match, while they will significantly vary in terms of radiation efficiency. It is challenging to distinguish between these radiating and nonradiating tuning component settings during the design procedure. In this paper, we propose a method to determine the component settings with the highest efficiency at a desired operating frequency. The method uses a single full-wave simulation, which is combined with circuit-level calculations. We discuss how to apply the method in detail and demonstrate its functionality with an inverted-L antenna sporting three tunable barium-strontium titanate capacitors. It is shown that the method can successfully predict tuning component settings for high antenna efficiency over a 1.4–2.8 GHz tuning band, with total efficiencies up to 35% and radiation efficiencies up to 50%. The method can easily be applied to any desired antenna geometry. [ABSTRACT FROM AUTHOR]

The design of a novel differential shorted patch antenna (DSPA) from a normal single-ended shorted patch antenna (SPA) is presented. It is shown that the DSPA has a smaller electrical size than the SPA. A transmission-line model is proposed to explain the reduced resonant size of the DSPA. A size reduction ratio of the DSPA to the SPA is defined and evaluated. It is found that the size reduction ratio mainly depends on the substrate thickness and the patch shape and slightly on the substrate dielectric constant. The simulated and measured results are given for both DSPA and SPA. The size reduction of the DSPA with respect to the SPA was experimentally validated. [ABSTRACT FROM AUTHOR]

This article presents the design and realization of a compact ultra‐wideband (UWB) antenna with on‐demand WLAN band‐rejection. The antenna consists of a simple truncated rectangular patch with a U‐slot and a partial ground plane, which are both patterned on Taconic TLY‐5 substrate (εr = 2.2). The lower corners of the patch are truncated with a semicircle to realize wideband characteristic, while the notch is obtained by etching a U‐slot on the radiating patch. The proposed antenna outperforms the existing UWB antennas owing to its compact size, radiation stability, and very wide impedance bandwidth. Simulated and measured results show that the novel antenna has a very wide operating bandwidth of 2.9‐23.5 GHz with a VSWR <2, and a notch band from 4.9 to 6.1 GHz to reject IEEE 802.11a and HIPERLAN/2 frequency band. The antenna offers promising performances including moderate gain (Gmax = 6.1 dB), nearly omnidirectional stable radiation patterns, and a compact overall size of 13 × 22 × 0.8 mm3. Besides of the other advantages, this antenna design presents mechanical robustness, easy integration into circuit boards, and excellent low‐cost mass production suitability. [ABSTRACT FROM AUTHOR]

Abstract Smartwatches with wireless connectivity are becoming widely used and therefore, antenna engineering efforts are addressed to obtain small and efficient antenna systems. Since the space in a smartwatch is considerably small compared to other wireless devices, a non-resonant element of 12.0 mm × 3.0 mm × 2.4 mm for 2.4–2.5 GHz antenna system operation is proposed herein on a 30 mm × 30 mm ground plane. The ground clearance area is 14 mm × 5 mm, which leaves more space for facilitating the integration of other electronic components in the reduced ground plane area available for this kind of applications. Since the element is non-resonant, a matching network is used to match the antenna system when regarding the presence of a phantom hand. Several distances between the ground plane and the phantom hand are analyzed, from touching position to 6 mm distance. For each case, a new matching has been designed without the need of modifying the geometry of the antenna element. Measured total efficiency is in average (2.4–2.5 GHz) 15.1% for the worst case (touching position) and increases up to 37.0% for the 6 mm case. These results are of practical interest to design smartwatch devices. [ABSTRACT FROM AUTHOR]

• Antenna measurements are normally performed in expensive laboratories. • Laboratory-grade validation of performance is not always needed/justified. • Satisfactory responses can be obtained in non-anechoic conditions upon refinement. • Correction method for far-field measurements based on Hilbert filters is proposed. • The method automatically tunes filter parameters to ensure high-performance correction. One of the most important steps in the process of antenna development involves measurements of its prototype. Far-field performance of radiators is normally characterized in strictly controlled environments such as anechoic chambers which can ensure certification-grade accuracy. Unfortunately, they are also characterized by high construction costs which might not be justified for low-budget research and/or teaching-related activities. Alternatively, the radiation characteristics can be obtained in non-anechoic test sites which neglect the expensive components such as shielding and/or absorbing materials. Although the noise from external radiation sources and multi-path interferences renders direct measurements in such conditions useless for drawing conclusions on antenna performance, the quality of responses can be substantially increased using appropriate post-processing. Unfortunately, the existing techniques are difficult to set-up and prone to failure which makes them of limited use for day-to-day measurements. In this work, a correction framework for non-anechoic measurements based on a set of Hilbert filters automatically adapted to propagation conditions within the test-site has been proposed. The presented method has been validated based on three example antennas and a total of 25 experiments covering 15 unique frequencies of interest. A benchmark of the method against the state-of-the-art correction techniques has also been performed. [ABSTRACT FROM AUTHOR]

In this paper, a miniaturized implantable antenna with the dimensions of 8×8×1 mm³ has been studied for continuous monitoring of Blood Glucose Levels (BGL). The antenna performance is analyzed numerically for both the free space and implanted operation. The results show that the works excellently in both the scenarios. The antenna has the lowest resonant frequency of 3.58 GHz in free space with a gain 1.18 GHz while it operates at 2.58 GHz with a gain of 4.18 dBi. Good performance, small size and resilience to the human body effects make the antenna to have a good potential use in future implantable glucose monitoring devices. [ABSTRACT FROM AUTHOR]

This paper reports the extraction of electrical impedance at microwave frequencies of vertically aligned multi-wall carbon nanotubes (VA MWCNT) bundles/forests grown on a silicon substrate. Dedicated resonating devices were designed for antenna application, operating around 10 GHz and benefiting from natural inductive/capacitive behavior or complex conductivity in the microwave domain. As obtained from S-parameters measurements, the capacitive and inductive behaviors of VA MWCNT bundles were deduced from device frequency resonance shift.

A double layer spiral antenna with side length of 740~\mu \textm was fabricated by a multilayer electroplating process and bonded with an radio frequency identification chip by silver epoxy to form a microsensor chip. A theoretical power transfer model was built to optimize the power transfer efficiency. The resonant frequency of the microsensor was characterized inside a small coupling loop, exhibiting a high degree of agreement with theoretical results. A magnetically coupled communication and charging platform was developed to work with the microsensors. The reader antenna was composed of a coupling loop and a secondary coil with 40-mm diameter wrapped around a polycarbonate tube. To maximize the magnetic field generated inside the secondary coil, a lump circuit model was built and its resonant modes were analyzed. The maximum current inside the secondary coil was achieved at the serial resonant frequency, at which the current followed a sinusoidal distribution along the coil. The magnetic field distribution inside the coil was calculated to analyze the read-out of the reader antenna. The communication and power transfer was demonstrated with the microsensors flowing through the reader antenna by successfully retrieving the sensor ID. [2016-0318] [ABSTRACT FROM AUTHOR]

A MIMO antenna system with two non-resonant antenna elements operating at the high-bands of LTE (1.71GHz-2.69GHz) is proposed. To improve the isolation, a stub has been located between the two non-resonant elements in a smartphone platform. Results for measured multiplexing efficiency and isolation are compared with and without the stub. The main conclusion is that the stub not only improves isolation but also improves the average measured multiplexing efficiency by 1dB across the band. [ABSTRACT FROM AUTHOR]

ABSTRACT A Superstrate loaded miniaturized patch antenna is proposed for biomedical applications. The targeted operating frequency is (902-928 MHz) ISM band with a center frequency of 915 MHz. The antenna is designed to operate in close proximity with human-body with a size of 25 × 25 × 1.92 mm3. Parametric studies were conducted to specify the dominant parameters and to understand their effect on the antenna performance. Measurements show that the fabricated antenna resonates around 915 MHz with a 30 MHz impedance bandwidth. On-skin measurement results are presented for several spots on the human-body. Furthermore, the transmission coefficient (S21) of the fabricated antenna is measured using lean beef slices with various thicknesses and showed good agreement with simulation results. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1212-1218, 2017 [ABSTRACT FROM AUTHOR]

Both the radiation efficiency and bandwidth of electrically small antennas are dramatically reduced as the size decreases. Fundamental limitations on the bandwidth of small antennas have been thoroughly treated in the past. However, upper bounds on radiation efficiency have not been established even though it is also of significant importance. Here, radiation from a thin metallic shell is rigorously analyzed to establish fundamental limits on the radiation efficiency of resonant, electrically small antennas in terms of the size and the metal conductivity. Metallic losses are systematically introduced into the circuit model proposed by Chu, and several resonant antennas with maximum radiation efficiencies are analyzed. Resonant electric and magnetic dipole antennas both have maximum radiation efficiencies near 100% until the size is reduced below a critical value, at which point the efficiency scales as electrical size to the fourth power ( ( \mathrm ka )^4 ) . It is also shown that a helix antenna that resonantly couples the TM10 mode to the TE10 mode has a maximum radiation efficiency, and is about twice that of a resonant dipole or loop antenna. The closed form expressions reported here provide valuable insight into the design of small antennas with optimal efficiencies. [ABSTRACT FROM PUBLISHER]

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A compact antenna for UWB communication systems has been realized by employing a quasi-selfcomplementary structure together with a triangular notch on microstrip feed line in this paper. The optimal design of this type of antenna can offer an ultra wide return loss bandwidth with reasonable radiation properties. It features a quite small physical dimension of 16 mm x 25 mm, corresponding to an electrically size of 0.24 λ. A good agreement is achieved between the simulated and the measured antenna characteristics. The major parameters that influence the performance of the antenna are investigated numerically to gain an insight into the antenna operation. Time domain performance of the antenna is also examined in order to assess its suitability for impulse radio applications.

Small antennas and other modern communication applications are using increasingly higher frequencies while demanding shorter development time and very rapid testing cycles. A fast and accurate way to exhaustively determine antenna performance and/or investigate device malfunction is based on spherical near field measurement techniques combined with probe array technology. This paper describes the innovative design aspects of the StarLab portable antenna measurement system and present results from the validation campaigns including both passive and active measurements. The use of integrated diagnostic and analysis software modules for efficient antenna design and testing is also presented.

• Compact antenna measurements are normally performed in expensive test sites. • Non-anechoic sites require post-processing to obtain high-fidelity measurements. • Data can be refined using inefficient and difficult to set up time-gating method. • Low-cost, test-site calibration algorithm for time-gating method (TGM) is proposed. • Method improves fidelity and reduces the cost of measurement data acquisition. Non-anechoic sites represent a cheap alternative to measurements of antennas in dedicated facilities. However, due to a high noise—from the external EM signal sources and multipath interferences—the quality of radiation patterns obtained in non-anechoic conditions is poor. The characteristics can be corrected using a time-gating method (TGM), which involves filtering of the noise based on temporal analysis of the measured signals. Unfortunately, determination of appropriate TGM setup is prone to failure due to its manual, or semi-manual nature. In this work, an automatic TGM calibration algorithm for accurate measurements in non-anechoic environments has been proposed. The method involves calibration of the test site using the antenna with known accurate responses. The process is implemented as an optimization routine where TGM intervals are adjusted through a curve fitting of the on-site measurements to the reference radiation patterns. The proposed framework has been demonstrated using four compact radiators and validated against the state-of-the-art techniques. Applicability of the method for calibration of the measurements in distinct test sites, as well as the analysis of the aliasing and external noise on the quality of corrected measurements have also been investigated. [ABSTRACT FROM AUTHOR]

In this article, a novel ultra wideband (UWB) small antennas based on the composite right/left-handed transmission lines structures are proposed. The antennas are presented with best in size, bandwidth and radiation patterns. Their physical size and the operational frequency depend on the unit cell size and the equivalent transmission line model parameters of the CRLH-TL. To realize characteristics of first proposed model, Q-shaped gaps printed into rectangular radiation patches are used. The antenna based on composite right/left-handed transmission lines is composed of two unit cells, each of which occupies only 10.8 × 8.6 mm and covers the 2.7–9.3 GHz bandwidth for VSWR < 2. The peak gain and radiation efficiency, are 5.78 dBi and 42.1% 9.3 GHz, respectively. Moreover, the second designed antenna has the same size and enhancement bandwidth, gain and radiation efficiency than the first proposed antenna with similar design procedure. It is constructed of the printed Q-shaped four unit cells. The length, width and height are 21.6, 8.6 and 1.6 mm, respectively, and it covers 4.1–11.7 GHz bandwidth for VSWR < 2 having highest gain (7.18 dBi) and radiation efficiency (92.69%) at 4.1 GHz.

A new small on-metal UHF Radio Frequency Identification (RFID) transponder, 18 \text mm \times 4 ~\text mm \times 2 mm in size, is presented. The read range of the transponder has been optimized by using the most efficient radiator within the given maximum dimensions and even more importantly, by conjugate impedance matching between the small antenna and the microchip, which has been achieved by using antenna-integrated components. As a commercially viable solution is targeted, the bandwidth and the sensitivity of the antenna to the dimensional variation of the fabrication process have been studied and solutions for improved robustness are presented. After the study and optimization of the transponder, a series of prototypes was fabricated on printed circuit board. The measurement results of the prototypes showed good consistency with the simulations and a read range of 3.0 m was measured for a prototype mounted on a metal plate. [ABSTRACT FROM PUBLISHER]

The design of electrically small antennas (ESAs) loaded with active non-Foster elements is a topic whose interest has grown in the last years. In this communication, a new strategy for the design of actively matched antennas loaded with non-Foster elements is presented. The analysis of different parameters, such as the sensitivity to non-Foster circuit placement, the overall antenna system stability, and current distributions, has to be considered in order to enhance the antenna performance. A design example using an ESA and its realization is presented to validate the proposed strategy. [ABSTRACT FROM AUTHOR]

A novel J shaped slot antenna for ultra-wide band (UWB) WiMedia is presented. The proposed antenna is designed using a microstrip to slot line cross transition on FR4 substrate with permittivity 4.4. Return loss of the antenna is from 2.8- 13GHz and occupies just 28x10 mm 2 on the PCB. Radiation patterns are stable and omni-directional. Antenna transfer function and impulse response are analyzed to study the pulse handling capability of the antenna. [ABSTRACT FROM AUTHOR]

This paper presents a small printed tri-band antenna with a reduced ground-plane effect for WLAN/M-WIMAX applications. The radiator and ground plane of the antenna are etched on a printed circuit board with an overall size of 25×24.5×0.762 mm3. A rectangular notch and a circular slot are cut from the radiator while an asymmetrical strip is attached to the radiator. The simulation and measurement suggest that the printed antenna achieves three operating bandwidths of 2.4-2.484 GHz and 5.15-5.35 GHz for WLAN, 3.3-3.69 GHz for M-WIMAX for a 10-dB return loss, and high gains on Y-Z plane of 2.1, 3.3 and 4.8 dB at 2.4, 3.5 and 5.2 GHz, respectively. In particular, the ground-plane effect on impedance performance is significantly reduced by minimising the size of the ground plane and then by cutting a notch and a circular slot from the radiator because the electric currents on the ground plane are significantly suppressed at all the operating bandwidths. In addition, a study on the geometrical and electrical parameters of the proposed antenna may be a useful reference for antenna engineers. [ABSTRACT FROM AUTHOR]

An open-slot antenna with a low profile of 7 mm to provide a triple-wideband LTE operation in the metal-framed tablet device is presented. With the low profile, the antenna can fit in the narrow region between the metal frame and the display panel of the metal-framed tablet device. The triple-wideband operation covers 698–960 MHz (low band), 1710–2690 MHz (middle band), and 3400–3800 MHz (high band). The antenna mainly has a rectangular open slot and an L-shaped metal strip embedded therein to provide two open slots of different resonant paths. Using a microstrip feedline having a step-shaped section across the two open slots, good excitation of multiple slot resonant modes is obtained. Details of the proposed antenna are presented. [ABSTRACT FROM PUBLISHER]

ABSTRACT A low-profile open-slot antenna capable of providing a triple-wideband LTE operation for the metal-framed smartphone is presented. The antenna has a low profile of 7 mm and can fit in a narrow region between the metal frame and the display panel of the metal-framed smartphone. The antenna comprises three branch slots sharing a same opening disposed at the top or bottom edge of the casing of the smartphone. Two branch slots are excited using a U-shape microstrip feedline with wideband matching circuits embedded therein while the third-branch slot is excited parasitically. With the proposed feeding arrangement, the antenna provides the triple-wideband LTE operation to cover the low band of 698-960 MHz, middle band of 1710-2690 MHz, and high band of 3400-3800 MHz. Details of the proposed open-slot antenna are presented and discussed. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2231-2238, 2015 [ABSTRACT FROM AUTHOR]

A comprehensive SAR study of low and high directivity antennas operated at distances greater than 25 mm but less than 200 mm from a large homogeneous elliptical phantom is presented. The study considers antennas, such as dipoles, monopoles, planar inverted-F antennas (PIFAs), IFAs, patches, patch arrays, and dipole arrays. SAR estimation methods for low directivity antennas for both near and far field conditions are proposed and elucidated. For directive antennas and arrays radiating directly towards the phantom interesting phenomena are observed that require more detailed investigation. [ABSTRACT FROM AUTHOR]

ABSTRACT A 10-antenna array operating in the 3.6-GHz band (3400-3800 MHz) for multi-input multi-output (MIMO) operation in the smartphone is presented. Each antenna in the proposed array is a microstripline-fed open-slot antenna with same small dimensions of 3 × 8 mm2 (0.036λ × 0.096λ, λ is the wavelength at 3.6 GHz). The proposed array consists of two symmetric five-antenna arrays disposed, respectively, along two long side edges of the system ground plane of the smartphone. The proposed array is expected to be placed in the narrow spacing between the display panel and the long side edges of the smartphone. Acceptable isolation (better than about 10 dB) and good envelop correlation coefficient (ECC) of less than 0.1 for any two antennas in the proposed array is obtained. The maximum channel capacity of the proposed array in a 10 × 10 MIMO system is calculated to reach about 47 bps/Hz at 20-dB signal-to-noise ratio, which is larger than four times that (11.5 bps/Hz) of the upper limit of an ideal 2 × 2 MIMO system with 100% antenna efficiency and zero ECC between antennas. Details of the proposed 10-antenna array are described, and the experimental results are presented and discussed. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1699-1704, 2015 [ABSTRACT FROM AUTHOR]

ABSTRACT Although traditional designs achieve performance requirements by placing antennas for separate radio applications far apart to minimize coupling, recent trends require antennas to be placed within close proximity of each other due to space constraints. To enable both near-field wireless powering and far-field data communication on a single device, this letter describes the design of small antennas with both Bluetooth and near-field communication capabilities. The results for three distinct antenna designs indicate that combining disparate field regimes into a single dual-band antenna can be used to optimize performance for the particular application. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1053-1056, 2015 [ABSTRACT FROM AUTHOR]

A multilayered metamaterial-inspired antenna with a pixel grid loading structure is introduced. The antenna consists of two patterned metal layers separated by a thin dielectric film. The first layer contains a folded monopole antenna surrounded by a metal pixel-based loading structure, whereas the second layer consists of a photoconductive pixel grid utilized to tune the antenna. Appropriate pixel configurations to produce a desired performance are implemented in simulation using a binary genetic algorithm (GA) and a MATLAB-HFSS (high-frequency simulation software) interface. HFSS simulations show that the antenna can be tuned over a wide frequency range by appropriate choice of pixel states on the second layer, using a variety of conductivities. As a proof of concept, the pixel grid on the second layer is initially made of a metal conductor. Multiple antenna configurations corresponding to a wide frequency range are constructed using a multilayer fabrication method. The measured reflection coefficients and radiation patterns are shown to be in good agreement with HFSS simulations, successfully demonstrating the ability to tune the antenna using the pixel grid on the second layer. [ABSTRACT FROM PUBLISHER]

In this article, a novel ultra wideband (UWB) small antennas based on the composite right/left-handed transmission lines structures are proposed. The antennas are presented with best in size, bandwidth and radiation patterns. Their physical size and the operational frequency depend on the unit cell size and the equivalent transmission line model parameters of the CRLH-TL. To realize characteristics of first proposed model, Q-shaped gaps printed into rectangular radiation patches are used. The antenna based on composite right/left-handed transmission lines is composed of two unit cells, each of which occupies only 10.8 x 8.6 mm and covers the 2.7-9.3 GHz bandwidth for VSWR < 2. The peak gain and radiation efficiency, are 5.78 dBi and 42.1% 9.3 GHz, respectively. Moreover, the second designed antenna has the same size and enhancement bandwidth, gain and radiation efficiency than the first proposed antenna with similar design procedure. It is constructed of the printed Q-shaped four unit cells. The length, width and height are 21.6, 8.6 and 1.6 mm, respectively, and it covers 4.1-11.7 GHz bandwidth for VSWR < 2 having highest gain (7.18 dBi) and radiation efficiency (92.69%) at 4.1 GHz. [ABSTRACT FROM AUTHOR]

This paper introduces a general methodical approach for designing frequency reconfigurable antennas. This method was successfully used to design a novel coplanar waveguide (CPW)-fed slot frequency reconfigurable antenna capable of operating at four preselected frequency bands distributed over a wide frequency range from \sim59.5 MHz to \sim1000 MHz (i.e., \sim4 octaves of bandwidth) while keeping its overall size as small as possible. To add reconfigurablility to the antenna, optimally-designed and electronically-controllable PIN diode-loaded slots were used to strategically manipulate the flow of current path and consequently change the characteristics of the antenna. Designing for the lowest operating frequency (59.5 MHz), capacitor-loaded meandered slot lines and reconfigurable matching network were implemented to keep the size of the antenna as small as possible. The resulting overall size of the antenna is only 0.06\lambdaL\times 0.06\lambdaL where \lambdaL is calculated at 59.5 MHz. The measurement results verified that the antenna successfully operates at 59.25–59.75 MHz, 314–398 MHz, 430–496 MHz, and 792–950 MHz, all with an almost omnidirectional pattern and an acceptable gain. [ABSTRACT FROM PUBLISHER]

ABSTRACT A combined-type dual-wideband antenna with its lower wideband and higher widebands, respectively, contributed by two separate radiating portions thereof is presented. The two separate radiating portions (one low-band antenna and one high-band antenna) are easily combined into a compact structure for the 2G/3G/4G operation in the 698-960 and 1710-2690 MHz bands. In addition, for applications in the typical tablet device such as a tablet computer, the proposed antenna requires a very small ground clearance of 10 × 30 mm2 for the 2G/3G/4G operation. The low-band antenna for the 698-960 MHz band is an inverted-F antenna, with its radiating arm coupled to the antenna's feeding strip through a first chip inductor and its shorting strip embedded with a second chip inductor. The high-band antenna for the 1710-2690 MHz band is a monopole antenna formed by connecting a simple strip to the feeding strip and enclosed by the low-band antenna so as to achieve a compact antenna structure. A simple matching circuit disposed on the device ground plane can, respectively, widen the bandwidth of the antenna's lower and higher bands. The proposed combined-type antenna can easily achieve dual-wideband operation with a small antenna volume, and a promising antenna design for the 2G/3G/4G tablet device is presented. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2799-2805, 2014 [ABSTRACT FROM AUTHOR]