Showing papers on "Dipole antenna published in 2022"

Optimization of Subsurface Imaging Antenna Capacitance through Geometry Modeling using Archimedes, Lichtenberg and Henry Gas Solubility Metaheuristics

Abstract: Capacitive resistivity subsurface imaging of roads operating at very low frequency is susceptible to antenna characteristic capacitance dynamics that may cause unwanted signal reflection, coupling, and unfavorable effect on reception sensitivity. Antennas are conventionally modeled using a complex and repetitive default mathematical method that is prone to human error and discrete results. To address this emerging challenge, this study has developed a new technique for plate-wire antenna capacitance optimization through equatorial dipole-dipole antenna geometry modeling using genetic programming (GP) integrated with metaheuristic methods, namely Archimedes optimization algorithm (AOA), Lichtenberg algorithm (LA), and Henry gas solubility optimization (HGSO). GP was used to construct the antenna capacitance fitness function based on 241 combinations of wire antenna radius and elevation, and dipole plate elevation, length, width, and thickness measurements. Minimization of antenna capacitance (approaching 1 nF) to achieve quasi-static condition was performed using GP-AOA, GP-LA, and GP-HGSO. The 3 metaheuristic-based antennas were 3D-modeled using Altair Feko and compared from the default antenna’s electrical features. It was found that even with the smallest dipole geometry, hybrid GP-LA antenna model exhibited the most practical outputs at 5 kHz with correct directional propagation based on its radiation pattern, a realistic receiver voltage of -8.86 dBV which is close to the default model, and a high-power efficiency of 99.925%. While hybrid GP-AOA and GP-HGSO resulted in indirect coupled transceiver systems with unsuitable antenna characteristic capacitance inducing anomalous receiver voltages. The experimental results prove the validity of the developed technique for more accurate determination of optimal antenna geometry.

Compact planar magneto‐electric dipole‐like circularly polarized antenna

Abstract: A novel circularly polarized (CP) substrate integrated magneto-electric dipole (MED) antenna has been designed for appropriate wireless communication. The antenna comprises two printed radiating arc-shaped patches and a feeding strip on top, two rows of embedded metallic vias, and a ground plane. A coax probe is used to excite the patches and via rows simultaneously with the help of a printed feeding strip. Finally, the antenna design has been prototyped and its performance experimentally was verified in terms of impedance bandwidth, axial-ratio (AR), gain, efficiency, and radiation patterns. The measured impedance bandwidth (under −10 dB) and AR bandwidth (under 3 dB) are 6.15–7.01 (13%) GHz and 6.24–6.40 (2.53%) GHz respectively. Typically, the measured gain value within 3-dB AR bandwidth at 6.3 GHz is 4.5 dBic with average measured in-band antenna efficiency of 85.2%. Moreover, the proposed antenna shows an acceptable agreement with predicted counterparts, including unidirectional radiation patterns.

Dual-Polarized Filtering Magneto-Electric Dipole Antenna Arrays With High Radiation-Suppression Index for 5G New Radio n258 Operations

Abstract: In this communication, a dual-polarized filtering magneto-electric dipole (FMED) antenna and arrays are proposed for 5G n258 (24.25–27.5 GHz) operations. The FMED antenna was devised to incorporate filtering mechanisms using a built-in substrate integrated waveguide (SIW)-based filter plus slot-and-notch etching on the dipole element. As such, lower and upper radiation cutoffs and nulls were produced and tuned, independently. To overcome the problem of “high selectivity” of a filtering antenna that has not been correctly quantified and thus has no comparison, a new skirt measure metric named as radiation suppression index is initiated here. Design steps of the FMED element and novel feeding techniques are elaborated, where the SIW-based series-parallel slot-coupled feeders and the slot-coupled differential power divider were conceived for large-size array, to combat with the insertion losses. A prototype of 4 $\times $ 4 FMED array was implemented and tested for experimental verification. A high gain of 16.8 dBi ± 1.4 dBi with a 3 dB gain bandwidth of 24–27.7 GHz and a radiation efficiency of 78% were accomplished.

Sub-6 GHz and mm-Wave 5G Vehicle-to-Everything (5G-V2X) MIMO Antenna Array

Abstract: A multi-beam and multi-polarized Multiple-Input Multiple-Output (MIMO) antenna system, which operates at Sub-6 GHz and mm-wave frequency bands is realized for 5G Vehicle-to-Everything (5G-V2X) application. Since the vehicle needs to communicate in different scenarios with the others, e.g. vehicles, passengers, control units, and mobile networks, in the surrounding area, an antenna with 360° coverage area is required. In this paper, an eight-element MIMO antenna is designed and implemented for this purpose. Four elements are distributed evenly in a circular substrate placed in the azimuth plane. Meanwhile, the other four elements are printed on two orthogonal substrates which are fixed perpendicularly to the circular substrate. Each radiating component is a tapered slot antenna integrated with a dipole to operate at both microwave and mm-wave bands. The simulated and measured results demonstrate capability of the proposed design in covering the whole surrounding area (360° coverage in azimuth plane). The antenna achieves a realized gain of more than 9 dBi at the mm-wave range and 4 dBi at the microwave range.

A Wideband Circularly Polarized Magnetoelectric Dipole Antenna for 5G Millimeter-Wave Communications

Abstract: In this paper, a wideband circularly polarized (CP) magnetoelectric (ME) dipole antenna operating at 28 GHz band was proposed for 5G millimeter-wave (mm-wave) communications. The antenna geometry included two metallic plates with extended hook-shaped strips at its principal diagonal position, and two corners of truncated metallic plates at the secondary diagonal position. The pair of metallic vias connected the modified strips to the ground plane to create the magnetic dipole. The L-shaped probe feed between the strips was used to excite the antenna. The antenna showed stable gain and wideband characteristics. The simulated and measured results showed that the proposed CP ME dipole antenna had an overlapping (|S11|< −10 dB impedance and 3 dB axial ratio) bandwidth of 18.1% (25–30 GHz), covering the frequency bands dedicated for 5G new radio communications. Moreover, an average gain of 8 dBic was achieved by the antenna throughout the operating bandwidth. The measured data verified the design concept, and the proposed antenna had a small footprint of 0.83 λo × 0.83 λo × 0.125 λo (λo is free space wavelength at the lowest operating frequency), suitable for its application in 5G smart devices and sensors.

Asymmetrical fed Calendula flower-shaped four-port 5G-NR band (n77, n78, and n79) MIMO antenna with high diversity performance

Abstract: Abstract This research reports a four-port multiple-input-multiple-output (MIMO) antenna designed for 5G-NR band applications including n77: 3.30–4.20 GHz, n78: 3.30–3.80 GHz, and n79: 4.40–5.00 GHz. The proposed design is analyzed in two parts, one single-element asymmetrical fed Calendula flower-shaped antenna and the other four-port modified MIMO antenna with the connected ground. The evolution of the MIMO antenna is studied based on the characteristics and optimized single-element antenna. The measured 5G-NR bandwidth offers a very high matching of impedance for MIMO configuration and higher isolation in the same band. The MIMO antenna offers an average peak gain of 3.51 dBi with a radiation efficiency of more than 90%. The radiation patterns plotted at 3.51, 4.00, 4.50, and 5.00 GHz match with almost omni-directional and dipole patterns in H- and E-radiating planes respectively. The MIMO antenna also records good diversity performance (ECC, DG, CCL, MEG, and TARC) in n77, n78, and n79 5G bands.

Examination of Impedance Response of Capsule- Integrated Antennas Through Gastrointestinal Tract

Abstract: This work focuses on the investigation of the degree of possible detuning that may be observed in the impedance response of ingestible antennas during the transition through the gastrointestinal tract. For this investigation, two fundamental antennas are used: a meandered dipole antenna and a meandered loop antenna. The antennas conform to the inner surface of the biocompatible capsule shell. They are optimized in spherical homogeneous time-averaged gastrointestinal phantoms to operate at 3 different frequencies of interest: 434 MHz, 1.4 GHz, and 2.4 G Hz, resulting in 6 different designs in total. N ext, the optimized antennas are simulated in 3 different phantoms, each mimicking the electromagnetic properties of one of the tissues in the gastrointestinal tract (stomach, small intestine, and large intestine). The impedance response of each design in 4 different tissues is compared and discussed. The results show that the maximum shift in the operating frequency of the antennas is 7 MHz, indicating that the presence of the encapsulation layer makes the considered antennas robust against the changes in the electromagnetic properties encountered through the gastrointesti-nal tract.

Dielectric Decoupler for Compact MIMO Antenna Systems

Abstract: A novel decoupling method based on the superposition principle is proposed for compact multi-input-multi-output (MIMO) antenna systems in this work. A dielectric block is introduced to encompass all radiators in a compact MIMO system and works as a decoupler when the block is appropriately designed. Owing to the presence of dielectric-air boundary (DAB) introduced by the dielectric block, scattered paths show up for electromagnetic (EM) waves inside the block. For any two encompassed primary radiators, mutual couplings via the direct and scattered paths are superposed one on another. Because the scatted wave paths can be controlled by changing the shape and dimension of the DAB, mutual coupling between two encompassed primary radiators can be minimized with properly designed DAB. To illustrate this decoupling principle, the electric field distribution of a basic Hertzian dipole wrapped in a dielectric decoupler is first studied. Results show that this method can generate several field valleys inside the dielectric block and can lead to good isolation when a second radiator is placed at a valley. A dual-port antenna wrapped in a dielectric decoupler is then proposed for demonstration. By optimizing the DAB shape, this antenna can realize a measured 20-dB isolation bandwidth of 12.6%, covering the whole 3.3-3.7 GHz 5G FR1 band. Furthermore, a quad-port decoupled antenna is studied to show the generality of the proposed decoupling method. Using a hollow rectangular dielectric block, isolations among four ports of more than 21.5 dB can be obtained in the 3.3-3.7 GHz band with a 20-dB isolation bandwidth of 18%. The envelope correlation coefficients (ECCs) and calculated ergodic channel capacity (CC) results show that the proposed compact dual-port and quad-port antennas are competitive for MIMO applications.

Scalable Omnidirectional Dual-Polarized Antenna Using Cavity and Slot-Dipole Hybrid Structure

Abstract: This article proposes a scalable dual-polarized antenna using the compact cavity and slot-dipole hybrid structure for omnidirectional radiation. For the horizontal polarization, an open-ended cavity is uniformly excited at its TE1/2,0,0 mode to achieve omnidirectional coverage. Based on this thin cavity, a hybrid structure with slots and parasitic dipole stub pairs is designed for vertical polarization, providing an omnidirectional pattern in the azimuthal plane. The measured results show that dual-polarized radiations with port isolation higher than 25 dB and gain variations lower than 2.7 dB are achieved in the band of 2.39–2.49 GHz, covering the frequency band of wireless local area network (WLAN) system. Moreover, to validate the scalability of the proposed antenna, a cascaded array is contrived to realize high-gain omnidirectional radiation. Compared with the existing works, the proposed omnidirectional dual-polarized antenna has the advantages of both compact volume and array scalability, exhibiting promising usage for high-gain router applications.

Co- and Cross-Polarization Decoupling Structure With Polarization Rotation Property Between Linearly Polarized Dipole Antennas With Application to Decoupling of Circularly Polarized Antennas

Abstract: A decoupling structure with polarization rotation (DSPR) property is proposed to reduce the mutual coupling between co- or cross-polarized antennas. The proposed DSPR generates a neutralization wave with two orthogonally polarized components that can be controlled to cancel the original mutual coupling. The DSPR is placed above the arrays with orthogonal and parallel dipole elements. After applying the DSPR, the mutual coupling at the center frequency of 3.5 GHz is reduced to −40 dB for both arrays, and the overall mutual coupling is better than −26 dB within the band of 3.3–3.7 GHz, and the reflection coefficients remain below −12 dB. The antennas maintain stable radiation patterns within the operation bandwidth with a 0.5 dB increase of the realized gain. Since the DSPR can effectively reduce both co- and cross-polarization coupling, the mutual coupling between circularly polarized antennas in a $1 \times 4$ array is reduced to below −35 dB thanks to the DSPR. Finally, a prototype of the antenna array with orthogonal dipole elements loaded with the DSPR is fabricated and measured. The measured results are in excellent agreement with the simulated ones, demonstrating the effectiveness of the proposed DSPR for isolation enhancement between cross-polarized antennas.

LTCC-Based Antenna-in-Package Array for 5G User Equipment With Dual-Polarized Endfire Radiations at Millimeter-Wave Frequencies

Abstract: An antenna-in-package (AiP) of endfire and dual-polarization at 28 GHz is presented. It is formed by four periodic antennas of broad bandwidth and high-isolation, fabricated by the low-temperature cofired ceramics technology. The dual-polarizations are realized by integrating a horizontal metal stripline-coupled dipole with a vertical magneto-electric monopole, incorporated into a multilayer architecture for compactness. The AiP skillfully implements vertical vias and horizontal strip lines in the cavities between antennas to improve isolation and polarization purity. This AiP has numerically been examined for endfire high gain and beam steering in user equipment (UE) applications. The prototype was measured to show good isolation lower than −25 dB from 26.5 to 29.5 GHz and agree with full-wave simulations. The antenna array is finally integrated with 1 $\times $ 4 boresight radiation microstrip antennas to form a complete UE AiP.

A Broadband Metasurface Antenna Array with Ultra-Wideband RCS Reduction

Abstract: In this paper, a metasurface-based antenna array with wideband radiation and broadband radar cross section (RCS) reduction is constructed. Without introducing additional radiators, the broadband radiation performance of the antenna array is achieved by inspiring the metasurface itself. In addition, the characteristic mode theory is introduced to analyze the radiation mechanism of the radiator elements and the proposed antenna array. Both simulations and measurements are carried out to verify the performance of the proposed antenna array. The results show that the impedance bandwidth and 3-dB gain bandwidth of the proposed antenna array are 5.1-9.0 GHz and 5.1-8.0 GHz, respectively, with a peak gain of 12.1 dBi. Monostatic RCS reduction more than 10 dB is achieved within the frequency band of 6.0-26.2 GHz.

Radio Antenna Design for Sky-Averaged 21cm Cosmology Experiments: The REACH Case

Abstract: Following the reported detection of an absorption profile associated with the 21[Formula: see text]cm sky-averaged signal from the Cosmic Dawn by the EDGES experiment in 2018, a number of experiments have been set up to verify this result. This paper discusses the design process used for global 21[Formula: see text]cm experiments, focusing specifically on the Radio Experiment for the Analysis of Cosmic Hydrogen (REACH). This experiment will seek to understand and compensate for systematic errors present using detailed modeling and characterization of the instrumentation. Detailed quantitative figures of merit and numerical modeling are used to assist the design process of the REACH dipole antenna (one of the two antenna designs for REACH Phase I). This design process produced a 2.5:1 frequency bandwidth dipole. The aim of this design was to balance spectral smoothness and low impedance reflections with the ability to describe and understand the antenna response to the sky signal to inform the critically important calibration during observation and data analysis.

28 GHz and 38 GHz Dual-Band Vertically Stacked Dipole Antennas on Flexible Liquid Crystal Polymer Substrates for Millimeter-Wave 5G Cellular Handsets

Abstract: Minimizing the size of mobile antennas is necessary for integrating the components inside a mobile device. Wideband and multiband antennas are also required to cover various 5G mobile communication frequency spectra. This article presents a vertically stacked dipole antenna array operating in the 28/38 GHz dual-band. The proposed antenna is small and satisfies the need for wide bandwidth in the form of a dual band. The antenna structure has symmetric 38 GHz band radiators positioned above and below a multilayer substrate, and a 28 GHz band radiator positioned on the middle plane, providing a dual-band antenna structure with small lateral width. Herein, two types of antenna structures are proposed, each with a single-ended and differential feed structure for compatibility with various RF front ends. The single antenna yields −10 dB bandwidth for return loss of 23.9% and 14.4%, and gain of 4.8 and 4.6 dBi at 28 and 38.5 GHz, respectively. The 4-element antenna array yields a gain of 9.0 dBi at 28 GHz and 10.3 dBi at 38.5 GHz. It was fabricated on a flexible substrate and can be bent and inserted into the lateral edge of the terminal. The proposed antenna elements and arrays satisfy the performance factors requisite for millimeter wave 5G communication including compact size, wideband, dual-band, and adequate gain.

A Wideband Circularly Polarized Complementary Antenna for Millimeter-Wave Applications

Abstract: This work presents a design of an aperture-coupled complementary antenna for realizing circularly polarized (CP) broadside radiation at millimeter-wave (mm-wave) frequencies. The proposed antenna constructively combines a patch dipole (electric dipole radiation) and a folded loop antenna (magnetic dipole radiation), which are differentially excited by a longitudinal slot etched on the top layer of the substrate integrated waveguide (SIW). The combination of the proposed patch dipole and the folded loop antenna results in a paralleled electric dipole and magnetic dipole which can generate two orthogonal electric field components and 90° phase difference in the far-field radiation when they are in-phase excited. The proposed antenna achieves a wide impedance bandwidth of 46% from 48.47 to 77.46 GHz and a wide 3 dB axial ratio bandwidth (ARBW) of 47.3% from 51.64 to 83.61 GHz with an overlapped bandwidth of 40%. To further enhance the antenna gain, sequential rotation technique is adopted to construct a $2 \times 2$ subarray, which is further employed in a $4 \times 4$ subarray. The $4 \times 4$ subarray is then used to construct an $8 \times 8$ antenna array, which achieves a wide impedance bandwidth of 33.8% from 56.11 to 78.95 GHz and a wide 3 dB ARBW of 38.8% from 53.57 to 79.32 GHz, with a maximum antenna gain of around 25.2 dBic. The proposed antenna element and array design would be a competitive candidate for future wireless applications operating at mm-wave spectrum.

Optically remote‐controlled miniaturized 3D reconfigurable CRLH‐printed MIMO antenna array for 5G applications

Abstract: A reconfigurable MIMO antenna array of a three‐dimensional geometry that is operating at sub‐6 GHz for 5G applications. The proposed antenna array provides a wideband with excellent matching impedance, S11 ≤ −10 dB, from 3.1 to 5.75 GHz. The proposed MIMO array is constructed from four antenna elements arranged on a cubical structure to provide a low mutual coupling, below −20 dB, over all frequency bands of interest. Each antenna element is excited with a coplanar waveguide. The proposed radiation patterns are controlled with two optical switches of light‐dependent resistors (LDRs). The antenna array is tested in terms of S‐parameters and radiation patterns. The maximum gain is found to be 3.6, 6.9, and 3.5 dBi at 3.6, 3.9, and 4.9 GHz, respectively. It is realized that the proposed array realizes a significant beam forming by splitting the antenna beam and changing the main lobe direction at 3.9 GHz after changing LDR switching statuses.

Millimeter-Wave Wideband Circularly Polarized Endfire Planar Magneto-Electric Dipole Antenna Based on Substrate Integrated Waveguide

Abstract: A wideband circularly polarized (CP) endfire planar magneto-electric dipole antenna based on substrate integrated waveguide (SIW) is proposed for millimeter-wave (mm-wave) applications. The antenna mainly consists of an open-ended rectangular SIW radiating like a magnetic dipole, a parallel electric dipole, and a double-sided parallel-strip line which connects the two dipoles and provides 90° phase difference between them to generate CP radiation. To increase the axial ratio (AR) bandwidth, a pair of triangular slots are etched at the end of the upper and lower broad walls of the SIW, and moreover, a specific bowtie-shaped electric dipole is used instead of the traditional linear one. It has been shown that both the slots and the bowtie-shaped electric dipole can regulate or tune the magnitude of the radiation field of the electric dipole, making it tend to balance with radiation field generated by the magnetic dipole, and hence, leading to a good CP performance. The antenna has a single-layer planar structure, and it shows a −10 dB impedance bandwidth of over 50%, a 3 dB AR bandwidth of 36.6%, and a peak gain of 9.3 dBic.

Radio-transparent dipole antenna based on a metasurface cloak

Abstract: Antenna technology is at the basis of ubiquitous wireless communication systems and sensors. Radiation is typically sustained by conduction currents flowing around resonant metallic objects that are optimized to enhance efficiency and bandwidth. However, resonant conductors are prone to large scattering of impinging waves, leading to challenges in crowded antenna environments due to blockage and distortion. Metasurface cloaks have been explored in the quest of addressing this challenge by reducing antenna scattering, but with limited performance in terms of bandwidth, footprint and overall scattering reduction. Here we introduce a different route towards radio-transparent antennas, in which the cloak itself acts as the radiating element, drastically reducing the overall footprint while enhancing scattering suppression and bandwidth, without sacrificing other relevant radiation metrics compared to conventional antennas. This technique offers a new application of cloaking technology, with promising features for crowded wireless communication platforms and noninvasive sensing.

A Broadband Dual-Polarized Solar Cell Phased Array Antenna

Abstract: This study proposes a broadband dual-polarized solar cell phased array antenna. It is constructed by using crisscross distributed metal-meshed tie-shaped dipoles, an optical transparent glass substrate, feeding probes and ground probes, a solar cell, and a metal ground. The meshed tie-shaped dipoles are sputtered on the top surface of the glass substrate. Circular metal-meshed patches located at the crisscrossing points of the dipoles on the back surface of the glass substrate are introduced to extend the operational bandwidth of the solar cell antenna. The solar cell was placed on the ground of the antenna. We fabricated a sample of the solar cell antenna and measured the electromagnetic characteristics and its power output. The results of the measurements agreed with those of simulations. The proposed solar cell antenna array had a wide operational bandwidth of 2.5–5 GHz, a wide 2-D range of the phase scanning angle of ±45°, a high aperture efficiency of 68.9%–84.1%, and a high relative maximum output power ratio of 87.1% compared with a pure solar cell. It is scalable and can be used in a self-sustained 5G wireless communication system for sub-6 GHz applications.

Stretchable 3D Wideband Dipole Antennas from Mechanical Assembly for On-Body Communication.

Abstract: The development of wearable/stretchable electronics could largely benefit from advanced stretchable antennas with excellent on-body performance upon mechanical deformations. Despite recent developments of stretchable antennas based on intrinsically stretchable conductors, they are often affected by lossy human tissues and exhibit resonant frequency shifts upon stretching, preventing their applications in on-body wireless communication and powering. This work reports a three-dimensional (3D) stretchable wideband dipole antenna from mechanical assembly to simultaneously reduce the frequency detuning and enhance on-body performance. The large bandwidth is achieved by coupling two resonances from two pairs of radiation arms, which is well-maintained even when the antenna is directly placed on human bodies or stretched over 25%. Such an excellent on-body performance allows the antenna to robustly transmit the wireless data and energy. The design of the 3D stretchable wideband dipole antenna with significantly enhanced on-body wireless communication performance was validated by an experimental demonstration that features a small difference in the wirelessly received power between the on-body and off-body use. The combination of the mechanically assembled 3D geometries and the coupled mechanical-electromagnetic properties can open up new opportunities in deformable 3D antennas and other microwave devices with excellent on-body performance and tunable properties.

Broadband Printed Dipole Antenna with Integrated Balun and Tuning Element for DTV Application

Abstract: This paper presents the broadband printed dipole antenna design with an integrated balun and tuning element for DTV applications. The proposed technique is a unique tuning mechanism that is straddled between the gap of the proposed dipole antenna. This enables the frequency range of the dipole antenna to be adjusted to tightly cover the specified Digital TV band, thereby mitigating interference from signals outside the band that would otherwise degrade the quality of the DTV signal. The measured results confirm that the proposed antenna covers an impedance bandwidth of 414.5 MHz from 457.7 to 872.2 MHz, which covers the frequency band of DTV systems (470–862 MHz). Furthermore, the proposed antenna has excellent omnidirectional radiation with a maximum realized gain of 2.95 dBi. These results demonstrate the suitability of the antenna for DTV applications.

A <i>Ka</i>-Band Antenna Array Based on Wide-Beamwidth Magnetoelectric Dipole

Abstract: A wide-beamwidth magnetoelectric (ME) dipole antenna for millimeter-wave (mm-wave) phased array applications is proposed in this letter. The antenna is fed by a substrate integrated waveguide. The electric dipole is formed by two patches, while the magnetic dipole consists of two apertures between the two patches. A short strip is introduced to connect the two patches, which can improve the impedance matching performance. The impedance bandwidth with | S ₁₁ | < −10 dB for the antenna element is 19.9% (28.11–34.32 GHz), as shown in the simulated results. And its half-power beamwidth in the xoz plane and yoz plane is wider than 82.1° and 81.8° over the operating band. To test the scanning potential of the ME-dipole antenna, a 4 × 4 phased array is constructed in high-frequency simulation software. The simulated scanning range of the phased array is beyond −41°∼41° at two sampling frequencies. Besides, a 4 × 4 antenna array is designed, processed, and measured. The array demonstrates a −10 dB fractional bandwidth of 15.3% (27.7–32.3 GHz) with a peak gain of 17.79 dBi at 30.4 GHz. The proposed ME-dipole antenna demonstrates good potential for 5G mm-wave phased array applications.

Low-SAR MIMO Antenna Array Design Using Characteristic Modes for 5G Mobile Phones

Abstract: A low specific absorption rate (SAR) multiple-input and multiple-output (MIMO) antenna array is designed for 5G mobile phones based on the theory of characteristic modes (TCMs). First, a geometrically symmetric dipole antenna is analyzed using TCM. The modal currents with symmetrical and reverse distributions are selected and excited to obtain the low-SAR antenna element. Then the antenna element is further optimized, and eight antenna elements constitute an MIMO array. The −6 dB impedance bandwidth of the proposed MIMO array is from 3.4 to 3.6 GHz. The isolations between different antenna elements are higher than 16 dB. Their total efficiencies range from 48% to 67%. Its envelope correlation coefficient (ECC) is lower than 0.08. The 1 g spatial-average head SAR and 10 g spatial-average body SAR of the proposed antenna are simulated and measured.

Wearable Pattern-Diversity Dual-Polarized Button Antenna for Versatile On-/Off-Body Communications

Abstract: A wearable dual-port button antenna that excites pattern-diversity dual-polarized waves is proposed for on-/off-body applications. Its simple structure comprises of two radiators and a common ground plane designed into two substrates. The crossed-dipole radiator is made by two symmetric bowtie dipoles printed on a circular-shaped semi-rigid substrate, which covers an ultra-wideband (UWB) application with circular polarization and directional radiation patterns, high gain, and high efficiency suitable for off-body communication. The annular-ring radiator and common ground plane are made by a conductive textile on the square-shaped flexible-felt substrate. The annular-ring radiator is shorted to the ground plane using four vias, which generates triple TM modes covering the 2.45/5.85 GHz wireless body area networks (WBAN) with omni-directional radiation patterns and a 3.8 GHz C-band with a directional radiation pattern suitable for on-/off-body communications. The fabricated antenna is verified by measurement in both free space and phantom body environment. Measurements agreed well with simulations. Simulated specific absorption rates (SARs) under US and EU standards are below the safe level, making the proposed antenna suitable for on-/off-body communications.

Broadband Circularly Polarized Magnetoelectric Dipole Antenna and Array for K-Band and Ka-Band Satellite Communications

Abstract: A circularly polarized (CP) magnetoelectric dipole (ME-dipole) antenna with wide impedance bandwidth and 3 dB axial ratio (AR) bandwidth is proposed. The antenna is fed by a microstrip line and coupled through a modified cross-slot on the ground plane. Based on the conventional linear-polarized (LP) ME-dipole, the proposed electric dipoles and the coupling slots are modified to generate the CP radiation. Simulated results of the antenna element show an impedance bandwidth of 72.8% from 16.35 to 35.08 GHz and a 3 dB AR bandwidth of 39.2% from 21.53 to 30.07 GHz. To enhance the gain of the antenna for practical application, a 4 × 4 antenna array with full-corporate feeding network is designed, fabricated and measured. The measured results show that an impedance bandwidth of 66.95% from 17.26 to 34.63 GHz and a 3 dB AR bandwidth of 41.1% from 19.25 to 29.25 GHz are achieved. The proposed antenna can be applied to K-band, Ka-band satellite communications or fifth-generation (5G) millimeter wave communications at n257 (26.5 -29.5 GHz) and n258 (24.25 -27.5 GHz) bands.

Super Compact UWB Monopole Antenna for Small IoT Devices

Abstract: This article introduces a novel, ultrawideband (UWB) planar monopole antenna printed on Roger RT/5880 substrate in a compact size for small Internet of Things (IoT) applications. The total electrical dimensions of the proposed compact UWB antenna are 0.19 λo × 0.215 λo × 0.0196 λo with the overall physical sizes of 15 mm × 17 mm × 1.548 mm at the lower resonance frequency of 3.8 GHz. The planar monopole antenna is fed through the linearly tapered microstrip line on a partially structured ground plane to achieve optimum impedance matching for UWB operation. The proposed compact UWB antenna has an operation bandwidth of 9.53 GHz from 3.026 GHz up to 12.556 GHz at −10 dB return loss with a fractional bandwidth (FBW) of about 122%. The numerically computed and experimentally measured results agree well in between. A detailed time-domain analysis is additionally accomplished to verify the radiation efficiency of the proposed antenna design for the ultra-wideband signal propagation. The fabricated prototype of a compact UWB antenna exhibits an omnidirectional radiation pattern with the low peak measured gain required of 2.55 dBi at 10 GHz and promising radiation efficiency of 90%. The proposed compact planar antenna has technical potential to be utilized in UWB and IoT applications.

A Self-Decoupling Method for Antenna Arrays Using High-Order Characteristic Modes

Abstract: In this article, a self-decoupling method is proposed for antenna arrays by exploring the coupling path through high-order characteristic modes (CMs) of the antenna elements. Mathematical formulas for coupling energy calculation are developed by combining the equivalent circuit of a receive mode antenna with the CM theory. With the CM analysis, radiating mode (RM) and decoupling mode (DM) of the antenna element are identified. An effective loading technique is proposed to enhance the modal significances of the DMs. The coupling between the DMs and the adjacent antenna element is enhanced, while the coupling with the dominant rms of the antennas is suppressed. Because of the coupling energy dispersion in the DMs, the corresponding unwanted induced currents flowing into the feed ports of the antenna element are suppressed, and the port isolations are efficiently improved. The decoupling structure composed of a simple metal ring and an impedance matching layer could be directly introduced into an antenna element, and the radiation performance of the previously optimized antenna element is preserved. Both simulated and measured results demonstrate that the port isolations are improved from 15 to 20 dB, and the radiation pattern distortion due to the mutual couplings is eliminated.

Dual-Wideband Dual-Polarized Dipole Antenna With T-Shaped Slots and Stable Radiation Pattern

Abstract: A dual-wideband dual-polarized dipole antenna for base-station applications is proposed. This antenna consists of a pair of crossed dipoles, a circular director, and a metallic reflector. The crossed dipoles are fed by two 50 Ω coaxial cables to achieve ±45° polarized radiation over a wide frequency band, while four T-shaped slots are cut in the dipole arms to produce two wide operating bands. The circular director is employed and located above the dipoles to enhance the impedance matching and further stabilize the radiation pattern at the higher frequency band. To further stabilize the pattern, four baffles are added along the edge of a square reflector. Measured results demonstrate that this antenna has two broad bandwidths of 47.8% (1.67–2.72 GHz) and 16.6% (3.3–3.9 GHz) for VSWR < 1.5 at the lower and higher frequency bands, respectively. Stable half-power beamwidths of 67.5°±8.5° for the lower frequency band and 64°±5° for the higher frequency band are obtained. The measured gains are stabilized at 8.1±0.5 dBi for the lower band and 8.35±0.25 dBi for the higher band. This antenna is potentially attractive for mobile communications.