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This study introduces a new design for an ultra-compact shared-aperture antenna utilizing a quarter-mode substrate integrated waveguide (QMSIW) cavity. The proposed antenna operates as a 4 × 4 multi-input multi-output (MIMO) system in three 5G/6G millimeter-wave (MMw) bands, while functioning as a single element antenna for a 5.5 GHz wireless fidelity Microwave (Mw) band. The antenna comprises four QMSIW cavity resonators; each QMSIW is loaded with dual slots to produce tri-band MMw operation at 28 GHz, 38 GHz, and 0.13 THz. The four cavities are arranged to reuse the entire aperture by creating a conventional open-loop antenna that operates at a frequency of 5.5 GHz. Simulation, measurement, and co-simulation results show that the proposed antenna has a quad-band operation and exhibits favorable characteristics. The measured scattering parameters validate the simulated ones over the four bands under consideration. The lowest values of the measured total radiation efficiencies are 80%, 73%, 62%, and 72% (co-simulation) within the four covered bands, respectively. The antenna peak gains are 1.8 to 1.85 dBi, 4.0 to 4.5 dBi, 4.3 to 4.5 dBi, and 6.5 to 6.6 dBi within the covered bands. Furthermore, the design satisfies MIMO and diversity conditions (envelope correlation coefficient and branch power ratio) over frequency bands of operation. All excellent results are achieved from an ultra-compact size in terms of footprint area (0.018λ02), where λ0 represents the free space wavelength at 5.5 GHz. The antenna boasts an excellent reuse aperture utilization efficiency (RAU) of 92% and a large ratio frequency of 23, making it an ideal candidate for compact devices. With its superior performance, the proposed design is well-suited for a range ofs wireless communication systems, including mobile devices and the Internet of Things.

A self-isolated 10-element antenna array operating in the long-term evolution 42 (LTE42) frequency band is proposed for 5G massive MIMO smartphone applications. The proposed antenna elements are placed in a 2D array configuration; they are placed symmetrically along the two long edges of the mobile chassis. The proposed antenna structure is a shorted loop antenna resonating at half-wavelength mode, which is rarely deployed by researchers due to its large size compared to other quarter wavelength antenna structures. It is a printed, shorted, and compact loop antenna of a total footprint area of $6\times6.5$ mm2 ( $\lambda /14.3\times \lambda $ /13.2, where $\lambda $ is the free space wavelength at 3.5 GHz). A small capacitive coupling flag-shaped strip is used to excite the proposed loop antenna. The compactness is achieved using an inward meandering that forms an internal loop in the element. The position and the dimensions of this loop are used to tune the resonant frequency and matching level at 3.5 GHz. The results (theoretical, simulated, and measured) show that the 3.5 GHz band (3.4-3.6 GHz) is achieved with impedance matching better than −10 dB, and total efficiency higher than 65%. A $10\times10$ MIMO system is formed and it has an excellent MIMO and diversity performance in-terms of the envelope correlation coefficient (below 0.055), and apparently it has the highest channel capacity (about 54.3 bps/Hz) among other MIMO systems of the same order. Simulation results of the specific absorption rate (SAR) demonstrates that the proposed antenna solution satisfied SAR criterion. Thus, the proposed ten-element MIMO antenna represent an excellent candidate for sub-6 GHz 5G smartphone applications.

A new, hybrid, nona-band antenna of the size 80 × 8 × 5 mm3 is proposed for recent metal-rimmed smartphone applications. The proposed design is composed of a metallic frame (external antenna) and an internal radiating structure. The proposed antenna is attached to the top part of the smartphone. It uses a microstrip feed as a direct coupling line for the internal radiating structure. The feed also represents a capacitive coupling feed for the overall metal-rim antenna structure. The metal rim with a small gap of 2 mm is connected to the system printed circuit board by two grounding points. The proposed antenna excites four coupled loop modes, three slot monopole modes, three dipole modes, and one monopole mode. By incorporating the excited modes, the proposed antenna covers all recent smartphone applications in the frequency range between 0.79 and 6.0 GHz. The proposed design is described with great details and both simulated and measured results are used to establish its validity. The antenna performance with mobile phone components is also investigated. The results demonstrate that the proposed antenna represents an excellent candidate for applications such as GSM850, GSM900, GSM1800, GSM1900, UMTS2100, LTE2300, LTE2500, LTE3500, and WiFi5500 bands.

In this work, a compact quad-element multiple-input-multiple-output (MIMO) antenna system is proposed. The design consists of four annular slot-line based MIMO elements, printed on a commercially available RO4350 substrate with a total size of 60 × 120 × 0.76 m m 3 . Each annular slot has a rectangular slot inside it to increase its electrical length to further bring down the resonance frequency. Furthermore, a T-shaped defected ground structure is utilised to increase the isolation between the closely spaced antenna elements. Each element is loaded with a unique split ring resonator (SRR), which results in size reduction as well as multi-band operation covering 1.7–2.28, 2.35–2.85 and 2.9–3.1 GHz. Moreover, by using only a single varactor diode per element, fine frequency tuning over these bands is achieved. A wide frequency sweep over multi-band and a peak gain of 2.95 dBi with 82% maximum radiation efficiency is achieved. Low envelope correlation coefficient values are observed throughout the operating band, thus offering good MIMO performance. The overall planar antenna design is compact, low-profile and can easily be integrated with radio frequency front ends in second generation cognitive radios among many other applications.

An existing dielectric resonator antenna (DRA) shape synthesis technique is substantially extended to the multiple-port case in order to realize pattern reconfigurable (beam-steered) versions of such antennas. The shaping procedure is described through reference to a specific class of problem, namely the satisfaction of certain statistical coverage area requirements through pattern reconfigurability. The procedure delivers a shaped DRA that, given the size and location constraints set at the start of the shaping process, has the potential to provide the best coverage possible. At the conclusion of the shaping, which utilizes characteristic mode analysis as a facilitator, a post-shaping step is used to locate the actual feedpoint ports. How closely the best coverage performance can be realized depends on restrictions placed on the beam-steering circuitry by the designer.

A transmitarray far-field beam scanning performance is illustrated based on the behavior of its focal region fields. It is shown that the oblique incidence of a plane wave on a transmitarray surface, forces the near-field focal point to shift mainly laterally with respect to the transmitarray surface. This behavior is shown useful in investigating a transmitarray far-field beam scanning. A beam scanning of 30 degrees is shown possible with no more than 1dBi gain loss.

A 2-element MIMO antenna is presented for 5G standards covering both the sub-6 GHz and millimeter-wave (mm-wave) bands using the same radiating structure. The antenna consists of a five concentric pentagonal slots. For the sub-6 GHz band, the antenna is excited by a single open-end microstrip tramsmission-line, while eight transmission-lines, connected through T-junction excites the mm-wave band. Designed on a substrate of of size $\mathbf{120}\times \mathbf{60\ mm}^{2}$ , the antenna covers 1.4-1.58 GHz, 1.82-2.14 GHz, 2.48-2.9 GHz, 3.1-3.8 GHz, 4-4.5 GHz and 27.8-28.3 GHz. The antenna not only provides backward compatibility with 4G bands, it also covers the sub-6 GHz 5G bands and 28 GHz bands.

A novel millimeter-wave (MMW) hybrid isolator is presented to reduce the mutual-coupling (MC) between two closely-spaced dielectric resonators (DR) antennas at 60 GHz. The proposed hybrid isolator consists of a combination of a new uni-planar compact electromagnetic band-gap (EBG) structure and an MMW choke absorber. The design of the proposed EBG unit-cell is based on the stepped-impedance resonator (SIR) technique. The results show that the proposed EBG structure provides a wide frequency bandgap in the 60 GHz band with miniaturization factors of 0.79 and 0.66 compared to conventional uni-planar EBG and uni-planar compact (UC-EBG) structures, respectively. The proposed EBG is then placed between two Multiple-Input Multiple-Output (MIMO) DR antennas to reduce the MC level. As a result, an average of 7 dB level reduction is obtained. To further reduce the MC level, a thin MMW choke absorber wall is mounted vertically between the two DR antennas and above the EBG structure. An average of 22 dB MC reduction is achieved over the suggested bandwidth while maintaining good radiation characteristics. The measured isolation of the prototype antenna varies from -29 to -49 dB in the frequency range from 59.3 to 64.8 GHz. In fact, the proposed hybrid isolator outperforms other hybrid isolation techniques reported in the literature.

Effective spherical near-field (SNF) test time reduction approaches are presented for wireless base station antennas that have widely differing beamwidths in the azimuth and elevation planes. The geometry of these antennas allows for the optimization of the SNF angular sampling density by allowing a lower sampling density along one of the acquisition axes. This is validated experimentally and shown to reduce the SNF test time significantly without degrading the measurement accuracy.

A compact, low profile and multiband dual-element folded strip monopole is presented for mobile phone MIMO applications. Both the compactness and the multiband operation are achieved by loading the folded strip with a split ring resonator (SRR). The antenna elements are placed on the same mobile PCB arm in order to achieve angle diversity that enhances ports isolation, especially below 1 GHz. The proposed antenna achieves isolation of higher than 12 dB, enveloped correlation coefficients (ECC) of less than 0.1, apparent diversity gain around 10 dB and total efficiencies of greater than 60 within the frequency band of interest (GSM850, DCS1800, PCS1900, and LTE2500).

A smart vision stick, used to powerfully help visually impaired people with new attractive features, is designed and tested. The stick comprises mainly of three parts namely, an indoor/outdoor guiding system, an emergency system and a smart detection system. The stick is designed such that the user can interact with it via a set of voice recognition commands that allow him to specify the destination name and then receiving a response from the stick immediately with full instructions that describes the directions and distances. For the outdoor guiding scenario a real time google map is used via a developed mobile application. The indoor guiding system is developed based upon a set of predefined locations with an accelerometer that help in measuring distances. Finally, a commercially available Global Position System (GPS) unit is used for the smart emergency system that ensures users' safety in any unusual condition.

This paper presents a full design and implementation process of a low-cost system that is used to clean solar panels automatically without using liquids. The system utilizes two microfiber brushes driven by two separate DC motors to clean the panels. Two more DC motors are used to control the machine movement. In addition, ultrasonic sensors are used to detect the edges of the solar panel to stop the motors at the proper time. The system also includes four relays that are connected to a microcontroller, which is placed at the gear box, to control the sensors, motors, and the brushes movement. Infra-red (IR) receiver, Infra-red (IR) remote and a 5V relay are used to switch on and off the system. The system is powered by a 12V lead acid DC battery.

A new MIMO antenna for metal-rimmed smartphone is proposed to cover four discrete wide bands of 0.79-0.965, 1.7-2.8, 3.3- 3.9 and 4.6-6.0 GHz. The antenna utilizes both the feed line and the metal frame to achieve multi-resonant modes. The feed line is modified with small radiating parts to create resonance modes in the mid and high frequency bands. The design operates with an acceptable isolation level without any isolation circuitry. The simulated results are used to confirm the MIMO antenna performance, the results shows that the proposed design represent a promising MIMO antenna solution for current metal-rimmed smartphone 4G applications.

The subject of whether or not it is necessary to include a feed field incidence angle in the design of main reflectarrays and subreflectarrays is discussed quantitatively in this article. The performance of reflectarray designs done with and without such incidence angle effects included are compared. The additional gain is achieved if the incidence angle is indeed included in the design process. The immunity of subwavelength elements to incidence angle effects is confirmed and illustrated using individual element patterns. Subreflectarrays designed with such subwavelength elements are shown to exhibit superior performance compared to those using half-wavelength ones.

Transmitarray work begins with the setting up of a database of transmission coefficients versus element parameters. This database has to be inverted as part of the design process. It is shown that inverse neural networks are well-suited to do this, even when the inverse relationships are multivalued.

The continued value of using two-dimensional (2D) approaches in computational electromagnetics is argued. We do this by first classifying the applications of such 2D analyses, and referring to examples in the literature where such analyses have proven useful. We then illustrate in detail the analysis of a 2D reflectarray, showing it as evidence of how such 2D analyses can be used to identify (and understand) the dominant operating mechanisms of complex electromagnetic structures. It is shown that, in spite of its 2D character, it exhibits the traits of a real 3D reflectarray.

The actual source of the “feed image lobe” in fixed-beam single-layer offset-fed reflectarrays composed of variable-size patch or dipole elements is diagnosed using a novel technique based on determining the individual contributions of the conduction currents on the reflectarray elements and the groundplane, to the reflectarray scattered fields. The behavior of the feed image lobe is studied over a range of frequencies about the center frequency, and this is used to establish the fact that both the elements and the groundplane are responsible for the presence of the feed image lobe. We show how to reduce or eliminate the feed image lobe at off-center frequencies in offset-fed reflectarrays through use of sub-wavelength reflectarrays instead of conventional reflectarrays with half-wavelength inter-element spacing. Measured and full-wave predicted results are used in all discussions.

A novel approach is proposed to suppress the frequency-dependent beam squint of offset-fed reflectarray patterns. The design comprises two offset feeds located at opposite ends of the reflectarray, in the plane of offset, simultaneously illuminating the reflectarray. This generates a single beam that does not squint from the desired design direction at off-center frequencies. The concept is validated by comparing the full-wave simulated patterns to measured counterparts.

The reason for the presence of unwanted sidelobes in multifeed single-beam reflectarrays and power combiners is shown to be a grating lobe phenomenon due to “amplitude clustering” of the scattered field over the reflectarray aperture. A means of controlling the level of these lobes is proposed and validated using full-wave analysis and measurements.

New observations related to the use of a dielectric substrate and an actual feed, in obtaining the interference pattern used in the synthesis of planar holographic antennas, are provided. It is demonstrated that the inclusion of the dielectric substrate, and actual feed effects, in holographic antenna realization, improves the antenna performance.

A planar holographic antenna with an integrated printed Yagi feed and two holograms separated by a foam spacer is presented. The design offers the advantage of a significantly higher aperture efficiency than other low profile planar holographic antennas with integrated feeds.

The basic design equations for symmetrical sub-reflectarrays are derived. These provide the required phase-distribution on the sub-reflectarray surface. Both ellipsoidal-type and hyperboloidal-type sub-reflectarrays are designed and fabricated using single-layer rectangular patch elements. Measured amplitude and phase patterns are shown for both types of sub-reflectarray, and compared to predictions. The behaviour of the ellipsoidal-type sub-reflectarray is furthermore compared to measured patterns of its solid subreflector counterpart. These experimental results show that the sub-reflectarrays indeed emulate the behaviour of their solid subreflector counterparts, and the validity of the basic design equations is thus established.

A full-wave receive-mode analysis is used to show that it is the shift in the location of the focal point with frequency (caused by nonconstant path delays over the surface of the reflectarray) that is principally responsible for the beam squint that occurs in offset-fed reflectarray antennas, and not the element type used or the lattice size. A similar transmit-mode analysis confirms that it is this focal point shift that implies noncoincidence of the focal point and the feed phase center at off-center frequencies, which results in a phase distribution over the reflectarray aperture with a slope other than that required to have the main beam in the desired direction. We further demonstrate this fact (computationally and experimentally) by showing that if the feed is physically moved to the shifted focal point at some off-center frequency, the main beam pointing direction at this frequency is restored.

The impact of important factors such as aperture size (D) and focal length (F) on the amount of focal point shift in offset-fed reflectarrays is investigated using a full wave receive-mode analysis.

Several authors have described the use of subwavelength inter-element spacing as a means of improving the performance of reflectarray antennas. This paper examines the use of such a sub-wavelength lattice for improving the performance of sub-reflectarray antennas. This does not yet appear to have been done by others. In addition to studying the scattered field patterns of such sub-reflectarrays on their own, we also inspect their performance when they are used to illuminate a main-reflector, as would be the case in practice.

The power combining efficiency of a dual-feed single-beam power combining reflectarray is shown to be substantially improved by reducing the spacing between the reflectarray elements. This improvement has been confirmed experimentally.

The full-wave analysis of a specific type of printed lens antenna is performed using the commercial code HFSS. This is done with the antenna operating in the receive mode and then in the transmit mode. The feasibility and usefulness of such computations is demonstrated.

Reflectarray operation is described by examining the contributions of its different components (the conducting patches, groundplane and dielectric substrate) to its far- and near-fields. It is shown how the fields, computed from a very complete full-wave model using the high-frequency structure simulator HFSS, can be separately post-processed to find the appropriate currents (not routinely available from HFSS) on the individual reflectarray components. The far- and near-field contributions of these currents are then used to assess the role played by these individual components in the overall reflectarray operation.

Several authors have described the use of reduced inter-element spacing as a means of improving the performance of reflectarray antennas. This paper discusses some additional aspects that complement their conclusions, and emphasizes some of the reasons for these improvements.

This paper describes the use of a two-dimensional (2D) method of moments analysis for electromagnetic scattering & radiation from objects comprised of both conducting and penetrable material (that is, composite objects). Such analyses are not available as existing commercial codes. Yet two-dimensional analyses are often able to reveal information about a situation whose 3D analysis is not feasible even by present day computational standards. We highlight a formulation that is accessible in the sense that a very complete version is available in such detail that it is relatively easily implementable, add some clarification of certain quantities, and describe some applications.