Showing papers on "Monopole antenna published in 2017"

A Dual-Band Inverted-F MIMO Antenna With Enhanced Isolation for WLAN Applications

Abstract: This letter presents a dual-band inverted-F multiple-input-multiple-output (MIMO) antenna with improved isolation, covering the 2.4/5-GHz wireless local networks (WLAN) band. The proposed MIMO antenna is composed of two symmetrical winding inverted-F antenna elements. The two antenna elements are closely spaced with about 0.115 λ 0 of the lower band. The high isolation is achieved by building two decoupling devices, a meandering resonant branch and an inverted T-shaped slot etched on the ground for the higher band and the lower band, respectively. Furthermore, two U-shaped slits achieving better impedance matching are etched on the 50-Ω feeding lines to broaden the bandwidth of the high band. The impedance bandwidth (S 11 <; -10 dB) of the proposed antenna covers 2.4-2.48 GHz in the lower band and 5.15-5.825 GHz in the upper band, and the proposed configuration obtains 15-dB isolation within the 2.4- and 5-GHz WLAN bands, which shows a significant improvement compared to the initial design of the MIMO antenna. The simulation and measurement results indicate that the proposed inverted-F MIMO antenna system is quite suitable for WLAN applications.

Broadband Printed-Dipole Antenna and Its Arrays for 5G Applications

Abstract: In this letter, we propose a broadband printed-dipole antenna and its arrays for fifth-generation (5G) wireless cellular networks. To realize a wide frequency range of operation, the proposed antenna is fed by an integrated balun, which consists of a folded microstrip line and a rectangular slot. For compactness, the printed dipole is angled at 45°. The single-element antenna yields an |S 11 | <;-10-dB bandwidth of 36.2% (26.5-38.2 GHz) and a gain of 4.5-5.8 dBi. We insert a stub between two printed-dipole antennas and obtain a low mutual coupling of <;-20 dB for a 4.8-mm center-to-center spacing (0.42-0.61 λ at 26-38 GHz). We demonstrate the usefulness of this antenna as a beamforming radiator by configuring 8-element linear arrays. Due to the presence of the stubs, the arrays resulted in a wider scanning angle, a higher gain, and a lower sidelobe level in the low-frequency region.

Compact Tapered Slot Antenna Array for 5G Millimeter-Wave Massive MIMO Systems

Abstract: A low-complexity metallic tapered slot antenna (TSA) array for millimeter-wave multibeam massive multiple-input multiple-output communication is proposed in this paper. Good beamforming performance can be achieved by the developed antenna array because the element spacing can easily meet the requirement of half-wavelength in the H-plane. The antenna element is fed by a substrate-integrated waveguide, which can be directly integrated with the millimeter-wave circuits. The proposed TSA is fabricated and measured. Measured results show that the reflection coefficient is lower than −15 dB Voltage Standing Wave Ratio ((VSWR) ≤ 1.45) within the frequency range from 22.5 to 32 GHz, which covers the 24.25–27.5-GHz band proposed by International Telecommunications Union (ITU) and the 27.5–28.35-GHz band proposed by Federal Communications Commission (FCC) for 5G. The gain of the antenna element varies from 8.2 to 9.6 dBi over the frequency range of 24–32 GHz. The simulated and measured results also illustrate good radiation patterns across the wide frequency band (24–32 GHz). A $1\times 4$ H-plane array integrated with the multichannel millimeter-wave transceivers on one PCB is demonstrated and excellent performance is achieved.

Compact 4G MIMO antenna integrated with a 5G array for current and future mobile handsets

Abstract: A novel integrated antenna solution for wireless handheld devices is proposed for the existing 4G standards and upcoming 5G systems for broadband, high data rate communications. The complete antenna system is a unique combination of a multiple-input-multiple-output (MIMO) antenna system at microwave frequencies and a millimetre (mm)-wave antenna array. The MIMO antenna system consists of two reactive loaded monopoles while the mm-wave array consists of a planar 2 by four slot antennas. The integrated antenna system covers the frequency bands from 1870 to 2530 MHz for 4G standards along with the upcoming 5G mm-wave band at 28 GHz. In addition, the integrated antenna system is planar and is designed for typical smart phone devices with a standard 60 mm by 100 mm by 0.965 mm back plane. Excellent field correlation values were obtained across the 4G band while realised peak gain values of 4 and 8 dBi were, respectively, measured for the MIMO and mm-wave antenna arrays. The proposed antenna design may also be useful for other compact implementations that support 4G and 5G communications.

Dual-Band Dual-Mode Textile Antenna on PDMS Substrate for Body-Centric Communications

Abstract: A dual-band antenna for off- and on-body communications in the 2.45- and 5.8-GHz Industrial, Scientific, and Medical bands is presented. The two radiation characteristics, i.e., patch-like radiation for the off-body link and monopole-like radiation for the on-body link, are achieved by utilizing inherently generated TM $_{11}$ and TM $_{02}$ modes of a circular patch antenna. A shorting pin and two arc-shaped slots are employed to tune both modes to the desired operating frequencies. This approach allows a realization of a dual-band dual-mode antenna with a very simple structure, i.e., a single radiator with a simple feed. A further advantage of the proposed antenna is its realization using a silver fabric integrated onto a flexible polydimethylsiloxane substrate that makes it more practical for wearable applications. An experimental investigation of the antenna performance has been carried out in free space and on a semisolid human muscle equivalent phantom, which shows a robust performance against the human body loading effect. When placed on the phantom, the measured bandwidths of 84 and 247 MHz in the 2.45- and 5.8-GHz bands, respectively, are achieved with the corresponding peak gains of 4.16 and 4.34 dBi, indicating a promising candidate for body-centric communications.

Compact EBG-Backed Planar Monopole for BAN Wearable Applications

Abstract: This paper presents a planar monopole backed with a 2 × 1 array of electromagnetic bandgap (EBG) structures. The reflection phase of a single EBG unit cell has been studied and exploited toward efficient radiation of a planar monopole antenna, intended for wearable applications. The shape of the EBG unit cell and the gap between the ground and the EBG layer are adjusted so that the antenna operates at 2.45 GHz. The proposed antenna retains its impedance matching when placed directly upon a living human subject with an impedance bandwidth of 5%, while it exhibits a measured gain of 6.88 dBi. A novel equivalent array model is presented to qualitatively explain the reported radiation mechanism of the EBG-backed monopole. The proposed antenna is fabricated on a 68 × 38 × 1.57 mm 3 board of semiflexible RT/duroid 5880 substrate. Detailed analysis and measurements are presented for various cases when the antenna is subjected to structural deformation and human body loading, and in all cases, the EBG-backed monopole antenna retains its high performance. The reported efficient and robust radiation performance with very low specific absorption rate, compact size, and high gain make the proposed antenna a superior candidate for most wearable applications used for off-body communication.

A Broadband Dual-Polarized Base Station Antenna With Sturdy Construction

Abstract: A broadband dual-polarized base station antenna with sturdy construction is presented in this letter. The antenna mainly contains four parts: main radiator, feeding baluns, bedframe, and reflector. First, two orthogonal dipoles are etched on a substrate as main radiator forming dual polarization. Two baluns are then introduced to excite the printed dipoles. Each balun has four bumps on the edges for electrical connection and fixation. The bedframe is designed to facilitate the installation, and the reflector is finally used to gain unidirectional radiation. Measured results show that the antenna has a 48% impedance bandwidth with reflection coefficient less than –15 dB and port isolation more than 22 dB. A four-element antenna array with 6° ± 2° electrical down tilt is also investigated for wideband base station application. The antenna and its array have the advantages of sturdy construction, high machining accuracy, ease of integration, and low cost. They can be used for broadband base station in the next-generation wireless communication system.

Compact, Highly Efficient, and Fully Flexible Circularly Polarized Antenna Enabled by Silver Nanowires for Wireless Body-Area Networks

Abstract: A compact and flexible circularly polarized (CP) wearable antenna is introduced for wireless body-area network systems at the 24 GHz industrial, scientific, and medical (ISM) band, which is implemented by employing a low-loss composite of polydimethylsiloxane (PDMS) and silver nanowires (AgNWs) The circularly polarized radiation is enabled by placing a planar linearly polarized loop monopole above a finite anisotropic artificial ground plane By truncating the anisotropic artificial ground plane to contain only 2 by 2 unit cells, an integrated antenna with a compact form factor of 041 λ 0 × 041 λ 0 × 0045 λ 0 is obtained, all while possessing an improved angular coverage of CP radiation A flexible prototype was fabricated and characterized, experimentally achieving S 11 <− 15 dB, an axial ratio of less than 3 dB, a gain of around 52 dBi, and a wide CP angular coverage in the targeted ISM band Furthermore, this antenna is compared to a conventional CP patch antenna of the same physical size, which is also comprised of the same PDMS and AgNW composite The results of this comparison reveal that the proposed antenna has much more stable performance under bending and human body loading, as well as a lower specific absorption rate In all, the demonstrated wearable antenna offers a compact, flexible, and robust solution which makes it a strong candidate for future integration into body-area networks that require efficient off-body communications

A Wide-Angle and Circularly Polarized Beam-Scanning Antenna Based on Microstrip Spoof Surface Plasmon Polariton Transmission Line

Abstract: In this letter, a wide-angle beam-scanning antenna with circular polarization (CP) characteristic is proposed. The antenna consists of two layers. Microstrip spoof surface plasmon polariton (SPP) is introduced on the bottom layer as a slow-wave feeding line. A series of circular patches are placed on the top layer as radiating elements. Simulated and measured results indicate that beam-scanning angle of the proposed antenna is improved and CP beam-scanning ability is obtained by introducing perturbation on the radiating elements. In the operating band of 11–15 GHz, measured scanning angle of the fabricated antenna is from –32° to +34°. The antenna axial ratio (AR) is below 3 dB at the corresponding beam direction, and gain is above 12.8 dBi over the whole band. It has potential applications in radar and wireless communication systems for simple structure, low-cost fabrication, wide beam-steering, and CP properties.

Wearable Button Antenna for Dual-Band WLAN Applications With Combined on and off-Body Radiation Patterns

Abstract: A new type of wearable button antenna for wireless local area network (WLAN) applications is proposed. The antenna is composed of a button with a diameter of circa 16 mm incorporating a patch on top of a dielectric disc. The button is located on top of a textile substrate and a conductive textile ground that are to be incorporated in clothing. The main characteristic feature of this antenna is that it shows two different types of radiation patterns, a monopole type pattern in the 2.4 GHz band for on-body communications and a broadside type pattern in the 5 GHz band for off-body communications. A very high efficiency of about 90% is obtained, which is much higher than similar full textile solutions in the literature. A prototype has been fabricated and measured. The effect of several real-life situations such as a tilted button and bending of the textile ground have been studied. Measurements agree very well with simulations.

A compact double-sided MIMO antenna with an improved isolation for UWB applications

Abstract: This paper presents compact size 4 × 4 cm 2 MIMO antenna for UWB applications. The proposed antenna consists of four symmetric circular elements printed on low cost FR4 substrate with partial slotted ground plane. The two sides of the substrate are symmetric and each side is consisting of two radiators with the partial ground planes associated to the two other elements mounted on the other side. The two elements of the front side are orthogonal to the two other elements of the back side in order to increase the isolation between elements. For further reduction in the mutual coupling between elements, decoupling structures are presented in the top and bottom layers of the substrate. The simulated and measured results are investigated to study the effectiveness of the MIMO-UWB antenna. The results demonstrate the satisfactory performance of MIMO-UWB antenna, which has a return loss less than −10 dB from approximately 3.1 GHz to more than 11 GHz with an insertion loss lower than −20 dB through the achieved frequency band, and a correlation less than 0.002. Moreover, the proposed MIMO model exhibits a nearly omni-directional radiation pattern with almost constant gain of average value 3.28 dBi.

A Fern Fractal Leaf Inspired Wideband Antipodal Vivaldi Antenna for Microwave Imaging System

Abstract: This communication presents a new approach to implement planar antipodal Vivaldi antenna design. A nature fern inspired fractal leaf structure is implemented here. Impedance bandwidth (−10 dB) of the proposed antenna is around 19.7 GHz starting from 1.3 to 20 GHz. The lower operating frequency of this antenna is reduced by 19% with the second iteration as compared to the first iteration of fractal leaf structure. The prototype antenna is fabricated and tested in frequency as well as in time domains to obtain various transfer characteristics along with common antenna parameters. Experimental results show that good wideband feature, stable radiation pattern, and promising group delay of less than 1 ns signatures are obtained, which agree well with the simulated data. The miniaturized proposed antenna structure becomes an attractive choice in microwave imaging applications because of its ultrawide fractional bandwidth at 175%, high directive gain of 10 dBi, and finally appreciably large fidelity factor above (>90%).

A Two Concentric Slot Loop Based Connected Array MIMO Antenna System for 4G/5G Terminals

Abstract: In this paper, an integrated design with a multiple-input multiple-output (MIMO) antenna system for fourth generation (4G) and fifth generation (5G) applications is presented. The proposed design contains a two-element slot-based MIMO antenna system for 4G and a connected antenna array (CAA)-based two-element MIMO antenna system for a potential 5G band. Two rectangular loops are etched on the periphery of the ground plane. The top and bottom portions of the thin loops act as the two 4G MIMO antennas, while parts of their sides are acting as 5G arrays. The antenna system is fabricated on a commercially available Roger 4350 substrate with $\epsilon _{r}$ equal to 3.5, while the dimensions of the board are $100\times 60 \times 0.76$ mm3 representing a typical smart phone back plane size. The integrated antenna system covers multibands at 4G with a combined bandwidth of 1.565 GHz (−6 dB BW) in addition to the band between 16.50 and 17.80 GHz for 5G. The design is planar, low profile, simple, and compact in structure making suitable for wireless handheld devices and mobile terminals. The measured gain at 3.46 GHz was at least 2.22 dBi and at 17 GHz was 8 dBi for the 4G and 5G MIMO antenna systems, respectively. The envelope correlation coefficient was also calculated from the measured 3-D patterns and showed good MIMO performance. This is the first integrated 4G/5G MIMO antenna system with below 6 GHz and above 10-GHz covered bands using CAA.

Mutual Coupling Reduction in Dielectric Resonator Antennas Using Metasurface Shield for 60-GHz MIMO Systems

Abstract: An effective technique for reducing the mutual coupling between two dielectric resonator antennas (DRAs) operating at 60-GHz bands is presented. This is achieved by incorporating a metasurface between the two DRAs, which are arranged in the H-plane. The metasurface comprises an array of unique split-ring resonator (SRR) cells that are integrated along the E-plane. The SRR configuration is designed to provide bandstop functionality within the antenna bandwidth. By loading the DRA with 1 × 7 array of SRR unit cells, a 28-dB reduction in the mutual coupling level is achieved without compromising the antenna performance. The measured isolation of the prototype antenna varies from -30 to -46.5 dB over 59.3-64.8 GHz. The corresponding reflection coefficient of the DRA is better than -10 dB over 56.6-64.8 GHz.

Multi-Polarization Reconfigurable Antenna for Wireless Biomedical System

Abstract: This paper presents a multi-polarization reconfigurable antenna with four dipole radiators for biomedical applications in body-centric wireless communication system (BWCS). The proposed multi-dipole antenna with switchable 0°, +45°, 90° and −45° linear polarizations is able to overcome the polarization mismatching and multi-path distortion in complex wireless channels as in BWCS. To realize this reconfigurable feature for the first time among all the reported antenna designs, we assembled four dipoles together with 45° rotated sequential arrangements. These dipoles are excited by the same feeding source provided by a ground tapered Balun. A metallic reflector is placed below the dipoles to generate a broadside radiation. By introducing eight PIN diodes as RF switches between the excitation source and the four dipoles, we can control a specific dipole to operate. As the results, 0°, +45°, 90° and −45° linear polarizations can be switched correspondingly to different operating dipoles. Experimental results agree with the simulation and show that the proposed antenna well works in all polarization modes with desirable electrical characteristics. The antenna has a wide impedance bandwidth of 34% from 2.2 to 3.1 GHz (for the reflection coefficient ${\leq}$ −10 dB) and exhibits a stable cardioid-shaped radiation pattern across the operating bandwidth with a peak gain of 5.2 dBi. To validate the effectiveness of the multi-dipole antenna for biomedical applications, we also designed a meandered PIFA as the implantable antenna. Finally, the communication link measurement shows that our proposed antenna is able to minimize the polarization mismatching and maintains the optimal communication link thanks to its polarization reconfigurability.

Three-Element MIMO Antenna System With Pattern and Polarization Diversity for WLAN Applications

Abstract: In this paper, a three-element compact multiple-input-multiple-output (MIMO) antenna system having both pattern and polarization (linear/circular) diversity is proposed. The proposed MIMO system consists of a chamfered-edge square patch antenna with an offset feed that provides circular polarization in broadside direction. Furthermore, two printed dipole antennas are placed adjacent to it for providing linearly polarized endfire radiation. The three-element MIMO antenna system exhibits good isolation (>15 dB) without the use of any separate decoupling structure. The match between the simulated and measured results on fabricated antenna prototype suggests that the proposed antenna can be a good candidate for pattern-and polarization-diversity MIMO applications in the 5.8-GHz WLAN frequency range.

Wearable Antenna Integrated into Military Berets for Indoor/Outdoor Positioning System

Abstract: A wearable antenna integrated into a military beret for an indoor/outdoor positioning system is proposed. The antenna consists of a truncated patch and a circular ring patch with four conductive threads. The truncated patch antenna is designed for the Global Positioning System (GPS) L1 band for use in outdoor situations, and the circular ring patch antenna with four conductive threads operates at the TM41 higher-order resonance mode (915 MHz) with a monopole-like radiation characteristic for indoor positioning systems. The antenna is fabricated using textile materials and is integrated into a military beret. The effects of the antenna deformation due to the shape of the military beret and the effects of the human head are analyzed via both simulation and measurement. The simulated and measured 10-dB return-loss bandwidths of the antenna on the head phantom fully cover the 915-MHz industrial, science, and medical band and the 1.575-GHz GPS L1 band.

Wideband Circular-Polarization Reconfigurable Antenna With L-Shaped Feeding Probes

Abstract: A wideband circularly polarized reconfigurable patch antenna with L-shaped feeding probes is presented, which can generate unidirectional radiation performance that is switchable between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). To realize this property, an L-probe fed square patch antenna is chosen as the radiator. A compact reconfigurable feeding network is implemented to excite the patch and generate either LHCP or RHCP over a wide operating bandwidth. The proposed antenna achieves the desired radiation patterns and has excellent characteristics, including a wide bandwidth, a compact structure, and a low profile. Measured results exhibit approximately identical performance for both polarization modes. Wide impedance, 31.6% from 1.2 to 1.65 GHz, and axial-ratio, 20.8% from 1.29 to 1.59 GHz, bandwidths are obtained. The gain is very stable across the entire bandwidth with a 6.9-dBic peak value. The reported circular-polarization reconfigurable antenna can mitigate the polarization mismatching problem in multipath wireless environments, increase the channel capacity of the system, and enable polarization coding.

CPW-Fed Dual-Band Dual-Sense Circularly Polarized Monopole Antenna

Abstract: A novel design of a dual-band and dual-sense circularly polarized coplanar-waveguide-fed monopole antenna with two rectangular parasitic elements and an I-shape grounded stub is presented here. The monopole consists of a vertical and a horizontal section. Lower band is obtained due to 90° phase difference between currents in the two orthogonal branches of the monopole. Upper band is obtained due to the I-shape stub. Parasitic elements help in input impedance matching. The dual-band and dual-sense antenna provides wide 10-dB impedance bandwidth of 71.63% at 2.82 GHz. The 3-dB axial-ratio bandwidths are 27.45% at 2.55 GHz (right-hand circular polarization) and 7.1% at 3.53 GHz (left-hand circular polarization).

A New Technique to Design Circularly Polarized Microstrip Antenna by Fractal Defected Ground Structure

Abstract: A new technique to design single-feed circularly polarized (CP) microstrip antenna is proposed. The CP radiation is obtained by adjusting the dimension of the etched fractal defected ground structure (FDGS) in the ground plane. Parameter studies of the FDGS are given to illustrate the way to achieve CP radiation. The CP microstrip antennas with the second and third iterative FDGS are fabricated and measured. The measured 10-dB return-loss bandwidth of the CP microstrip antenna is about 30 MHz (1.558 to 1.588 GHz), while its 3-dB axial-ratio bandwidth is 6 MHz (1.572 to 1.578 GHz). The gain across the CP band is between 1.7 and 2.2 dBic.

A Compact Dual-Band MIMO Slot Antenna for WLAN Applications

Abstract: A very compact dual-band two-element multiple-input–multiple-output antenna for wireless local area network applications is presented in this letter. The antenna occupies an overall area of 24 × 25 mm2. A microstrip-line-fed antenna with two quarter-wavelength slots of different lengths, which radiate at 2.5 and 5.6 GHz, is used as an antenna element. The proposed antenna uses a simple decoupling network, based on a wide slot and a pair of narrow slots, to achieve good isolation (better than 20 dB) between the ports. Moreover, the envelope correlation coefficient of the proposed antenna is within the acceptable limit.

Low-Mutual-Coupling 60-GHz MIMO Antenna System With Frequency Selective Surface Wall

Abstract: A new dielectric resonator antenna (DRA) for a millimeter-wave (mm-wave) multiple-input–multiple-output system is presented. Two approaches are exploited to reduce the mutual coupling between two antenna elements. First, a frequency selective surface (FSS) wall is inserted between the DRAs to reduce the free-space radiation. Then, two slots with different size acting like an $LC$ resonator are etched from the common ground plane of the structure to reduce the surface current. The designed FSS has a wideband characteristic from 40 to 70 GHz. The FSS is optimized for the desired frequency of 57–63 GHz. A high isolation of −30 dB is achieved when both FSS wall and slots are used. A prototype of the structure is fabricated and measured. The results give a low correlation coefficient ( $e$ –6) and a good agreement with simulation ones, indicating that the proposed antenna can provide spatial or pattern diversity to increase the data capacity of wireless communication systems at mm-wave bands.

A Miniaturized UWB Biplanar Yagi-Like MIMO Antenna System

Abstract: A novel 2-element ultrawideband Yagi-based multiple-input-multiple-output (MIMO) antenna system is presented based on loop excitation. Half of the driven loop element is implemented on each side of the substrate, which not only reduces the overall size of the antenna by 45%, but also increases its bandwidth significantly. The center frequency of operation is 5.8 GHz targeting WLAN applications. The proposed design has a wide measured bandwidth of 2.401 GHz covering 4.183-6.584 GHz. The proposed compact MIMO antenna system has an overall size of 50 × 80 × 0.76 mm 3 with a single element size of 50 × 40 × 0.76 mm 3 . The proposed Yagi antenna has high directional radiation characteristics with a minimum measured front-to-back ratio of 18 dB, minimum measured gain of 6 dBi, and directivity of 6.6 dB using a single director element only, at 5.8 GHz. It has a minimum measured isolation of 17 dB, measured maximum envelope correlation coefficient value of 0.0568, and measured total efficiency above 80% across the band of operation.

Easily Extendable Compact Planar UWB MIMO Antenna Array

Abstract: This letter presents a highly isolated compact four-element planar ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna array configuration. The main advantages of the proposed array configuration are that it requires no isolation/decoupling circuit and the configuration is easily extendable to larger size array. The array consists of novel miniaturized slotted annular ring monopole antenna and each element in the array is placed orthogonal to its adjacent elements. The fabricated structure provides good impedance bandwidth matching and high isolation between elements over the range from 3 to 15 GHz. The absence of decoupling circuit results in overall compact size of the proposed design. The prototypes are fabricated and tested. The simulated and measured results are in good agreement. Moreover, the envelope correlation coefficient and channel capacity loss of the array are calculated, which shows good MIMO performance. The proposed monopole antenna structure supports multielement UWB MIMO antenna array design with easy extension of elements and without any decoupling circuit. An example of eight-element array is also investigated.

A Wideband Circularly Polarized Conformal Endoscopic Antenna System for High-Speed Data Transfer

Abstract: In this paper, a conformal wideband circularly polarized (CP) antenna is presented for endoscopic capsule application over the 915-MHz Industrial, Scientific, and Medical (902–928 MHz) band. The thickness of the antenna is only 0.2 mm, which can be wrapped inside a capsule’s inner wall. By cutting meandered slots on the patch, using open-end slots on the ground, and utilizing two long arms, the proposed antenna obtains a significant size reduction. In the conformal form, the antenna volume measures only 66.7 mm3. A single-layer homogeneous muscle phantom box is used for the initial design and optimization with parametric studies. The effect of the internal components inside a capsule is discussed in analyzing the antenna’s performance and to realize a more practical scenario. In addition, a realistic human body model in a Remcom XFdtd simulation environment is considered to evaluate the antenna characteristics and CP purity, and to specify the specific absorption rate limit in different organs along the gastrointestinal tract. The performance of the proposed antenna is experimentally validated by using a minced pork muscle phantom and by using an American Society for Testing and Materials phantom immersed in a liquid solution. For measurements, a new technique applying a printed 3-D capsule is devised. From simulations and measurements, we found that the impedance bandwidth of the proposed antenna is more than 20% and with a maximum simulated axial ratio bandwidth of around 29.2% in homogeneous tissue. Finally, a wireless communication link at a data rate of 78 Mb/s is calculated by employing link-budget analysis.

A Compact Four-Element MIMO/Diversity Antenna With Enhanced Bandwidth

Abstract: In this letter, a four-element wideband multiple-input–multiple-output (MIMO) configuration consisting of inverted L-monopole antenna (ILA) elements is proposed. An additional low-frequency operating mode arises in the MIMO system due to symmetric arrangement of elements with interconnected ground, apart from the resonance of the isolated ILA. Utilizing this mode, the proposed MIMO antenna operates in wide frequency range of $\text{2.70-4.94}$ GHz (impedance bandwidth $=58.6\%$ ). The proposed four-element MIMO system occupies compact total area of $0.13\lambda _{0}^{2}$ ( $\lambda _{0}$ = highest operating wavelength) and has no complex decoupling scheme. Satisfactory interelement isolation ( $\geq $ 11 dB) and directional pattern with average gain $\approx 4$ dBi are achieved throughout the operating band of the proposed MIMO antenna. Furthermore, envelope correlation coefficient $ and mean effective gain ratio close to 1 are obtained in the working frequencies, confirming satisfactory MIMO/diversity performance.

Generation of Plane Spiral OAM Waves Using Traveling-Wave Circular Slot Antenna

Abstract: Plane spiral orbital angular momentum (OAM) wave is a new form of OAM-carrying electromagnetic wave that propagates along the transverse direction. A traveling-wave circular slot antenna that can generate plane spiral OAM waves is developed and experimentally demonstrated in this letter. The antenna is excited by a 90 $^\circ$ hybrid coupler. In order to ensure that the OAM waves are propagating along the transverse plane, a ring horn is added outside the antenna. A prototype with OAM states l = $\pm$ 3 for 10-GHz operation is fabricated and measured. The near-field phase distributions clearly indicate the azimuth phase shifting, and the radiation patterns show the characteristic of transverse propagation, respectively. The proposed antenna provides a novel approach to implement an OAM wireless communication link that has no phase singularity or divergence problem.

A Low-Profile Reconfigurable Cavity-Backed Slot Antenna With Frequency, Polarization, and Radiation Pattern Agility

Abstract: A novel cavity-backed slot antenna, with the ability of reconfiguring the frequency, polarization, and radiation pattern, is presented. The reconfigurability is realized by electronically controlling the state of switches between two crossed slots etched on the surfaces of a substrate integrated waveguide cavity. The antenna is capable of simultaneously changing the radiation patterns between forward and backward directions, switching the polarization among two orthogonal linearly polarized (LP) and two orthogonal circularly polarized (CP) states, tuning between three frequency bands for LP states and between two frequency bands for CP states. A fully functional prototype is developed and tested, demonstrating the antenna with measured gains of approximately 4 dBi and stable unidirectional radiation patterns for all 20 states. In addition, the proposed design possesses a low profile of 0.01 free-space wavelength.

Design of filtering microstrip antenna array with reduced sidelobe level

Abstract: For the requirements of efficient integration and simple fabrication, a new codesign approach for a microstrip filter with an antenna array with reduced sidelobe level is introduced in this communication. The microstrip patch antennas and the stub-loaded resonators are used to illustrate the synthesis of a bandpass filtering antenna array. By controlling the coupling strength between the resonators, a uniform or nonuniform power divider network can be obtained. A nonuniform power division is used to reduce the sidelobe level. The equivalent lumped circuit model is developed and analyzed in detail. Two types of eight-element filtering antenna array with uniform and tapered power-distribution among the elements have been designed. Simulated and measured results provide a good verification for the theoretical concepts.

A Dual-Broadband, Dual-Polarized Base Station Antenna for 2G/3G/4G Applications

Abstract: A base station antenna with dual-broadband and dual-polarization characteristics is presented in this letter. The proposed antenna contains four parts: a lower-band element, an upper-band element, arc-shaped baffle plates, and a box-shaped reflector. The lower-band element consists of two pairs of dipoles with additional branches for bandwidth enhancement. The upper-band element embraces two crossed hollow dipoles and is nested inside the lower-band element. Four arc-shaped baffle plates are symmetrically arranged on the reflector for isolating the lower- and upper-band elements and improving the radiation performance of upper-band element. As a result, the antenna can achieve a bandwidth of 50.6% for the lower band and 48.2% for the upper band when the return loss is larger than 15 dB, fully covering the frequency ranges 704-960 and 1710-2690 MHz for 2G/3G/4G applications. Measured port isolation larger than 27.5 dB in both the lower and upper bands is also obtained. At last, an array that consists of two lower-band elements and five upper-band elements is discussed for giving an insight into the future array design.