Aperture-coupled Feed Research Articles

A Novel Topology of a 3 × 3 Series Phased Array Antenna with Aperture-Coupled Feeding.

This paper presents a novel 3 × 3 phased array antenna optimized for 4 GHz operation, achieving a realized gain of 13.2 dBi and enabling 30-degree beam steering with a minimal capacitance variation of 1.5 pF. The design features a series aperture-coupled feeding mechanism that not only reduces the antenna's size but also simplifies the fabrication process, making the device both cost-effective and compact. Integrating cost-efficient quadrature-hybrid phase shifters and novel power splitters with cascaded quadrature hybrids ensures uniform power distribution and precise beam steering. The innovative use of these components addresses common challenges in phased array systems, such as space constraints, high costs, and complex power distribution.

Enhancing connectivity/mobility in WBAN applications through detachable wearable multi-band MIMO antenna

The connectivity and mobility of a miniaturized multi-band four-port textile leaky wave multiple-input multiple-output (MIMO) antenna designed on a layer of denim (εr = 1.6, tanδ = 0.006) is enhanced by integrating it with two detachable spiral buttons designed on circular PTFE substrate (εr = 2.1, tanδ = 0.001). The connectivity and mobility enhancement of the proposed antenna is evaluated in terms of radiation and diversity parameters. Nested hexagonal split rings behind the buttons, U-shaped slots on textiles, a comb-shaped neutralization network, and an aperture-coupled feed technique are utilized. The unique structure of the buttons on a rigid substrate and the leaky wave antenna on the textile and their integration, the periodic nested elliptical and circular split ring resonators (CSRRs) slots on the aperture coupled to ground, are to expand the connectivity and mobility of the proposed MIMO antenna by offering multiple bands, higher isolation, broadside radiation, and low specific absorption rate (SAR). The leaky wave and button antennas have dimensions of 40 × 30 × 1 mm3 and a diameter of only 13 mm, respectively. The operational bands are 0.86–2.75 GHz, 2.9–4.85 GHz, 5.75–6.15 GHz, and 8–9.85 GHz, covering the L, C, S, and X bands. Additionally, diversity performance is evaluated by defining the envelope correlation coefficient (ECC), diversity gain (DG), Channel Capacity Loss (CCL), and mean effective gain (MEG). The simulation and measurement findings are in good agreement. Following that, it offers a maximum gain of 8.25 dBi, low SAR (<0.05), an ECC below 0.05, DG above 9.85 dB, CCL< 0.25 bits/s/Hz, MEG <−3 dB, Circular polarization (CP), and strong isolation (>22 dB) between every two ports. These features make the proposed antenna an ideal option for MIMO communications and suitable for wireless local area network (WLAN) and fifth-generation (5G) communications.

Wideband high gain metasurface-based 4T4R MIMO antenna with highly isolated ports for sub-6 GHz 5G applications

This study presents the design of four 178×178\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$178\ imes 178$$\\end{document} (mm)2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{2}$$\\end{document} wideband, high gain, highly efficient metasurface-based 4T4R MIMO (Multiple-Input Multiple-Output) antennas with highly isolated ports, covering the middle and a portion of the upper bands of the sub 6 GHz 5G frequency spectrum for 5G-based systems, such as IoT (Internet of Things) applications, vehicular communications (e.g., rooftop antennas of cars or trains), smart industries (e.g., farms and factories). The radiating elements of these antennas use the aperture-coupled feeding technique with a dumbbell-shaped slot, a truncated square patch with two U-shaped slots, and a metasurface layer. The proposed MIMO structures place four identical radiating elements like a 2×2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2\ imes 2$$\\end{document} matrix with 90∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$90^\\circ$$\\end{document} successive rotations to produce orthogonal electromagnetic waves, improving the isolation between ports. Six-millimeter spaces are added between these elements, and two vertical and horizontal strip slots are carved on the ground as the decoupling structure to decrease the mutual coupling. Simulation results show that Antenna_1, Antenna_2, and Antenna_3 achieve gain values of 6.2 to 9.4 dBi, 8.2 to 11.6 dBi, 6.2 to 9.5 dBi, below − 35, − 25, and − 33 isolation and almost 10 dB diversity gain from 2.8 to 4.7 GHz, 2.8 to 4.5 GHz, and 2.7 to 4.9 GHz, respectively. As a prototype, Antenna_4 is manufactured, and measurements are performed. It achieves 6.28 to 10.45 dBi gain values, below − 23 dB isolation, and 0.001 envelope correlation coefficient over 2.7 to 4.3 GHz. The results confirm that the proposed MIMO antennas are compatible with the 5G essential requisites.

A Two-Port Dual-Band Dual-Circularly-Polarized Dielectric Resonator Antenna

A Two-Port Dual-Band Dual-Circularly-Polarized Dielectric Resonator Antenna

Phase delay through slot-line beam switching microstrip patch array antenna design for sub-6 GHz 5G band applications

Two, four, eight, and sixteen-element patch array antennas for beam switching are presented in this study. For a 1×2 array, an aperture-coupled feeding mechanism is used to feed patches while a slot line on the ground plane provides the phase delay between antenna elements. The 1×2 array is used to create the 2×2, 4×2, and 8×2 arrays, and an equal power divider provides the signal for each. For applications in the 5G sub-6 GHz frequency spectrum, the antennas are modeled. With -37.14 dB, -17.85 dB, -21.51 dB, and -26.03 dB return loss for two, four, eight, and sixteen-element array antennas respectively the simulation demonstrates that the antennas are properly matched at the resonant frequency. The antennas can switch its radiated beam to ±24&lt;sup&gt;o&lt;/sup&gt;, ±24&lt;sup&gt;o&lt;/sup&gt;, ±28&lt;sup&gt;o&lt;/sup&gt;, and ±26&lt;sup&gt;o&lt;/sup&gt; with gains of 8.97 dBi, 11.19 dBi, 13.23 dBi, and 16.24 dBi, respectively at the resonance frequency. The directivity of the proposed antenna is found to be 9.17 dBi, 11.20 dBi, 13.40 dBi, and 16.45 dBi respectively. The antennas are constructed with two 0.8 mm-thick Teflon substrate layers. The ground plane between the two substrate layers contains the aperture and the slot line that generates the phase delay.

Aperture Sharing Metasurface-Based Wide-Beam Antenna for Energy Harvesting

Since the available ambient power level is usually quite low for radio frequency energy harvesting, it is very desirable for an antenna to have both a high gain and a wide beamwidth. Usually, they cannot be achieved simultaneously. In order to overcome this limitation, a multi-port antenna using a nonuniform metasurface (MTS) is presented. In this MTS-based antenna, three modes with complementary radiation patterns are excited through one middle and two side aperture-coupled feeding ports. The first mode is the fundamental TM10 mode with in-phase current distributions on the MTS. It has a broadside directional radiation pattern with a high gain. The second and third modes are symmetrical to each other at a high mode. They have opposite current distributions on two sides of the MTS. These two modes have a directional radiation pattern with a tilted angle. These three modes share the same aperture but are excited by three different feeds. Each feed is connected to a rectifier. By combining direct current (DC) output to a single load, an antenna with a wide beam and a high gain can be effectively achieved, although each mode has the usual limitation of gain and beamwidth. The key advantage of this proposed rectenna is that the unit cells on the MTS layer can be reused to excite different MTS modes with different radiation patterns simultaneously. Thus, a wide beamwidth can be achieved. Three realized beams are oriented at −35°, 0°, and + 35° respectively. By combining the DC output from the three modes, the proposed rectenna has effectively achieved a beamwidth of 114° with a gain ranging from 8 to 9.8 dBi. The RF-to-DC conversion efficiency of the rectifiers is 3%-67% at 2.45 GHz when the input power ranges from −35 to 0 dBm. The proposed MTS antenna with an overall size of λ0 × λ0 × 0.03 λ0 can achieve 12% fractional bandwidth.

A 3-D Printed Ultrawideband Magnetoelectric Dipole Antenna With Ridged Waveguide Aperture-Coupled Feeding

A ultrawideband magnetoelectric dipole (MED) antenna fed by a ridged waveguide is presented in this letter. Different from the widely used Γ-shaped probe feeding structure, a novel ridged waveguide aperture-coupled feeding technology is employed to excite the MED antenna and an ultrawideband MED antenna with an impedance matching of 104% from 1.92 to 6.08 GHz and directional pattern is realized. To verify this design, an antenna prototype is fabricated using the metallic three-dimensional printing technology. The measured impedance bandwidth of VSWR < 2 is 104% from 1.99 to 6.14 GHz. The directional patterns with a stable gain varying from 5.5 to 7.5 dBi are achieved. Besides, high radiation efficiency of above 89% is obtained owing to its all-metallic structure, which avoids the dielectric loss.

Low-Profile Wideband Circular Polarization Metasurface Antenna With Characteristic Mode Analysis and Mode Suppression

In this letter, a wideband circular polarization (CP) metasurface (MS) antenna is proposed, which is composed of a centrosymmetric structure with a mode suppressor and an asymmetric aperture-coupled feed structure separated by dielectric substrates. Based on the characteristic mode theory, the aperture-coupled feed structure consisted of an L-shaped slot and a microstrip line is employed to excite two orthogonal modes, which have a 90° phase difference to obtain CP radiation. Meanwhile, two methods have been proposed to expand CP bandwidth: one is the direct suppression of characteristic mode by decreasing the overlap frequency of operating and nonoperating mode. The other one is indirect suppression using a mode suppressor. Finally, the MS antenna with a low profile of λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.075 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> at 5 GHz is fabricated and measured. The measured results show that the proposed antenna has a 3 dB axial ratio bandwidth of 45.2% from 4.1 to 6.5 GHz and an impedance bandwidth of 41.8% from 4.1 to 6.31 GHz, and a peak gain of 7.94 dBic at 5.9 GHz.

High-Gain Circularly Polarized Antenna Array for Full Incident Angle Coverage in RF Energy Harvesting

In this paper, a high-gain circularly polarized (CP) hexagonal antenna array is proposed for RF energy-harvesting applications. The hexagonal antenna array is intended to operate at the frequency of 5.8 GHz. It is composed of 6 multilayer substrate CP antennas excited by an X-shaped aperture-coupling feed structure. A frequency selective surface (FSS) was added to further improve the gain, resulting in a maximum gain of 12.7 dBi per element. The main advantage of the proposed hexagonal antenna array is the ability to cover 360 degrees in the azimuth plane with a high gain in all directions without the use of any additional circuitry, allowing the effective absorption of ambient RF energy. A prototype was fabricated and measured, and a good agreement with the simulation results is achieved. In addition, a rectifier is used to convert RF energy absorbed by the antenna into DC energy at the frequency of 5.8 GHz. The measured RF-to-DC conversion efficiency of 44.5% and a DC output voltage of 423 mV at -10 dBm are observed. The performance of the rectenna array with one and six rectifiers has been demonstrated. With the use of a DC combiner, the total RF to DC efficiency of the array is 67.75%, with a DC output voltage of 1.115 V from -10 dBm has been recorded. Due to the immunity to misalignment of the CP antenna, the proposed rectenna array is very suitable for wireless power transfer (WPT).

A Reconfigurable Patch Antenna With Linear and Circular Polarizations Based on Double-Ring-Slot Feeding Structure

This article presents a general design method for the aperture-coupled linearly polarized (LP) and circularly polarized (CP) reconfigurable antennas. A novel double-ring-slot structure is developed as an improved aperture-coupled feeding network. First, an LP antenna integrated with filtering radiation performance is investigated. The double-ring-slot feeding structure not only realizes a bandpass-type filtering response with two deep radiation nulls at passband edges but also ensures wideband antenna impedance matching. Second, by coupling an extra microstrip line to the double-ring slot as a virtual input port, a CP antenna is developed. Finally, by inserting a p-i-n diode as the switch to control the ON-OFF state of the virtual input port, an LP-to-CP reconfigurable antenna is realized. Since no intricate components, such as filter resonators or reconfigurable circuits, are involved, the proposed reconfigurable antenna features a very simple structure and high radiation efficiency. To reveal the design procedure, the working mechanisms of the LP filtering antenna and CP antenna functions are studied and presented individually. For demonstration, the proposed antenna is fabricated and measured. When it operates as an LP antenna, it realized a 35.3% measured impedance bandwidth, 8.2 dBi flat in-band gains, and more than 15 dB out-of-band radiation suppression level, whereas, for the CP antenna operation, 12.6% measured axial ratio (AR) bandwidth is obtained.

Air-Filled SIW Remote Antenna Unit With True Time Delay Optical Beamforming for mmWave-Over-Fiber Systems

A low-complexity and efficient mmWave-over-fiber remote antenna unit (RAU) is proposed for broadband transmission and wide-angle squint-free beam steering in the full [26.5–29.5] GHz n257 5G band. It leverages an optical beamforming network (OBFN), implemented on a silicon photonics integrated circuit, and a broadband optically enabled 1x4 uniform linear array (ULA). The antenna elements (AEs) of the ULA are implemented in air-filled substrate-integrated-waveguide technology. They adopt an improved aperture-coupled feeding scheme to achieve high efficiency, high isolation and minimal back radiation over a broad frequency band. Each AE is compactly integrated and co-optimized with a dedicated opto-electrical transmit chain, maximizing the RAU’s performance, including beamforming flexibility and energy efficiency, while minimizing its size. The separately packaged OBFN implements true-time-delay beamforming by means of four switchable optical delay lines that are capable of discretely tuning the delay difference between AEs with a resolution of 1.6 ps, up to a maximum delay of 49.6 ps to fully exploit the ULA’s full grating-lobe-free scan range. The measured AEs are excellently matched in the [25.1–30.75] GHz band, exhibit high isolation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ &gt;$</tex-math></inline-formula> 15 dB) in the operating band, and feature a stable peak gain of 6.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.72 dBi with a beamwidth of at least 95 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> . Additionally, optical beamforming was successfully demonstrated by steering the RAU’s beam towards angles up to 51.8 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> without grating lobes. The optically enabled 1 × 4 ULA successfully establishes a 64-QAM wireless communication link at 2.2 Gbaud (13.2 Gbps) while beam steering up to 50 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ ^\circ$</tex-math></inline-formula> with an error vector magnitude below 7.6%.

Wideband planar coupled patch antennas with enhanced radiation pattern stability

This article tries to address the unstable radiation pattern issue of the planar-coupled patch antennas with two different methods. First, characteristic mode analysis (CMA) reveals that the coupled patch antennas generate three characteristic modes with distinctive radiation patterns. A slot-loading scheme is proposed to reshape the current distribution of the higher mode and reduce its sidelobe level significantly. Then a 13.4% bandwidth with consistent radiation patterns and high gain is achieved by exciting modes 1 and 3 while suppressing unwanted modes with an aperture-coupled feeding. Second, the radiation pattern stability of the coupled patch antennas is further improved by employing shorted parasitic patches. The presented antenna can be equivalent as the same magnetic current array model under the in-phase and out-of-phase modes, and thus the radiation patterns hardly get changed. Moreover, the non-radioative nature and high radiation quality factor of the higher mode improve the radiation performance in a new principle. It not only enhances the bandwidth up to 18.5% but also results in a sharp filtering edge of gain response.

Isolation Enhancement of UWB MIMO rDRA for 5G Outdoor Applications

In this paper, a two-port Ultra-Wideband Multiple Inputs Multiple Outputs (UWB MIMO) rectangular Dielectric Resonator Antenna (rDRA) is proposed for 5G sub-6 GHz outdoor applications. An edged hole is inserted at the rDRA edge for isolation enhancement purposes. The effect of edged hole radius on isolation is investigated. Both UWB MIMO rDRA with and without edged holes are investigated for both parallel and orthogonal feed schemes (four scenarios). Isolation better than -22 dB is obtained for orthogonal orientation and edged hole rDRA. Surface current density distribution is used to explain that isolation enhancement. UWB bandwidth and high efficiency are obtained on the operating bands due to the usage of an aperture-coupled feed system and edged hole rDRA. The proposed antenna has two -6 dB operating frequency bands, the lower band (2.25 GHz – 2.52 GHz) and the higher band (3.6 GHz – 5.7 GHz). The Envelope Correlation Coefficient (ECC) and diversity gain DG are used to justify the MIMO antenna performance. Good agreement is obtained between measured and simulated results.

Broadband Dual-Polarized Aperture-Coupled Patch Antenna for 5G Applications

Abstract: This paper presents the design of a dual-polarized aperture-coupled microstrip antenna array for Sub-6GHz 5G communication systems. The antenna operates at 3.5 GHz and consists of 4×4 square patches. The proposed 4×4 array antenna feds by aperture-coupled feed line provide broadband bandwidth to operate in the N78 sub-6GHz 5G frequency band. The dualpolarized is presented, which gives two communications channels. The antenna consists of three layers and is designed on Rogers RO4003C substrate with a dielectric constant of 3.55 and substrate thickness of 0.8 mm. The final design of the antenna array with an overall size of 269 mm × 269 mm × 12.5 mm, and the results show that the 4×4 array has a 10dB bandwidth between 3.3-3.8 GHz and a maximum gain of 14.9 dB at 3.5 GHz, and the isolation between the two ports was 30 dB. The proposed antenna's gain, radiation efficiency, and bandwidth satisfy the requirements of 5G base station systems.

Differential-Fed, Dual-Aperture Based, Quasi-End-Fire 5G mmWave Antenna-in-Package Design

A low-profile, wideband antenna-in-package (AiP) design is proposed for 5G mmWave mobile applications. The aperture-coupled feeding incorporated with the microstrip feed line through the slots in the ground is used to excite the patch antenna. Firstly, a thin quarter-wave shorted patch antenna (QW-SPA) with the dominant <i>TM</i>^<i>z</i>_1/2,0,0 mode is realized. To broaden the operating band, the QW-SPA is extended along its resonant length so that the <i>TM</i>^<i>z</i>_1,0,0 mode can also be excited. The offset introduced into the two slots together with the additional shorting via wall are applied to enhance the beam tilt toward the end-fire direction. The proposed single-patch design shows a wide fractional bandwidth, covering the 5G mmWave band n257 (26.5&#x2013;29.5 GHz). Furthermore, to increase more beam tilt, the differential-fed, two-patch sub-array formed by two QW-SPAs spaced a half-wavelength at 28 GHz apart is also presented. Compared with the single-patch design, the beam-tilt enhancement of around 10&#x2013;27 degrees is obtained over the desired frequency band with the peak gain of around 8.2 dBi for the sub-array AiP design.

A Wideband Antenna for mm-Wave Antenna-in-Package Application

Antenna-in-Package has been widely applied for millimeter-wave systems that integrate the MMIC chip and antenna into one package. For organic substrate Antenna-in-Package solutions, probe feeding and aperture-coupled feeding patches are generally used as radiation units. In this work, a patch antenna is proposed using coupled resonation; a wideband, high-gain and compact 3-D antenna package integration is realized. An equivalent circuit model is analysed for the coupled structure. &#x03BB;/4 coupled line is adopted for impedance matching, the whole antenna is designed on the same thick radiation patch substrate, with less organic substrate lamination layers. For millimeter-wave Antenna-in-Package structures, vias are generally used for vertical interconnections, which function well in the lower millimeter-wave frequency range. For operation frequency higher than 100GHz, design difficulties may be encountered for via interconnection, with performance degeneration on impedance matching and transmission loss. This work integrates a H-shaped slot instead of vias on an organic substrate, realizing a high frequency and wideband mm-wave transition. An interconnection structure is also adopted to convert a microstrip line to differential microstrip line in the feeding network. Antenna prototype with 2&#x00D7;4 radiation array is designed for verification purpose at 20GHz frequency range with simulated bandwidth of 23%. The prototype is fabricated with separate PCB boards assembled with screws, measured antenna gain is 12.7dBi-13.5dBi. The proposed structure provides a wideband and low-loss solution for potential higher frequency mm-wave Antenna-in-Package applications.

Low-Profile and Wideband Circularly Polarized Magneto-Electric Dipole Antenna Excited by a Cross Slot

In this article, we present the design of a low-profile circularly polarized (CP) magneto-electric (ME) dipole antenna with enhanced CP bandwidth properties. The ME dipole antenna is excited by a simple microstrip line aperture-coupled feeding structure. The coupling aperture is composed of two crossed slots of unequal lengths to realize CP operation. Four identical inverted L-shaped parasitic elements, each consisting of a horizontal patch and a vertical metallic plate, are vertically positioned around the ME dipole. It was found that such parasitic elements can remarkably improve the 3 dB axial ratio (AR) bandwidth while retaining the wide impedance bandwidth. A prototype with a low profile of only 0.134λL (λL is the wavelength in free space at the lowest operating frequency) is fabricated and tested to verify the proposed design. The experimental results show that the prototype has an overlapping impedance bandwidth (|S11| ≤ –10 dB) and a 3 dB AR bandwidth of 3.16–5.36 GHz (51.35%) with a maximum broadside left-handed CP gain of 9.75 dBic. Additionally, nearly identical radiation patterns on two principle cutting planes are obtained over the operating band.

Dual-Polarized Filtering Magnetoelectric Dipole Antenna Utilizing Intrinsic Highpass Filter Network and Integrated Lowpass Filter Network

This article presents an effective design method to integrate bandpass filtering response into an aperture-fed dual-polarized magnetoelectric dipole (ME-dipole) antenna. The antenna is composed of a traditional ME-dipole radiator and a modified aperture-coupled feeding structure. In one aspect, highpass filtering radiation response is realized by approximating the antenna radiator as a highpass filter network. In another aspect, by developing an improved aperture-coupled feeding structure with lowpass filter characteristics, the antenna obtains lowpass filtering radiation response. As a result, bandpass filtering radiation response is achieved. Since no intricate filter resonators are used, the in-band antenna gains are not degraded. The highpass/lowpass filter networks are studied and specific radiation nulls generated by the two networks are analyzed. For demonstration, a single-polarized model is presented first and its working mechanism is studied in detail. It realizes a 78.6% impedance bandwidth, flat in-band gains of 7.5–7.8 dBi, and more than 22 dB out-of-band radiation suppression level. Then, based on the same methodology, a dual-polarized antenna model i developed with 69.3% operating bandwidth, 7.1–9.3 dBi measured in-band gains, and integrated bandpass filtering radiation response.

An All-Textile Dual-Band Antenna for BLE and LoRa Wireless Communications

In this paper, a dual-band conductive textile-based wearable antenna operating at LoRa-868 MHz and BLE-2.4 GHz is presented. The proposed antenna is intended for accurate geolocation, tracking and communication applications in the military, industrial and telemedicine industries. The low-profile patch antenna is suitable for integrating into clothing. It is composed of three textile layers: top and bottom silver-ink-printed polystyrene fabrics, and a neoprene substrate. To utilize the flexible and restorable properties of these textile materials, the proposed antenna is directly fed by a flexible cable using an aperture-coupled feeding technique. This method not only eliminates the use of the conventional, bulky, and metallic SMA connector but also introduces a secondary resonance at 2.4 GHz, enabling the dual-band property. Using a thin coaxial cable fixed on the aperture slot for proximity coupling, a compact antenna size of 150 mm2 is obtained that can easily be attached and detached on existing cloths. The proposed structure has been fabricated and measured in an anechoic chamber to verify the performance. Measured gain of 3.28 dBi and 3.25 dBi was realized for LoRa and BLE at an antenna size of 0.61 λg × 0.61 λg × 0.012 λg (where λg is guided wavelength at 868 MHz) with a front-to-back ratio (FBR) of greater than 10 dBi.

High-Gain Millimeter-Wave Patch Array Antenna for Unmanned Aerial Vehicle Application.

A high-gain millimeter-wave patch array antenna is presented for unmanned aerial vehicles (UAVs). For the large-scale patch array antenna, microstrip lines and higher-mode surface wave radiations contribute enormously to the antenna loss, especially at the millimeter-wave band. Here, the element of a large patch array antenna is implemented with a substrate integrated waveguide (SIW) cavity-backed patch fed by the aperture-coupled feeding (ACF) structure. However, in this case, a large coupling aperture is used to create strongly bound waves, which maximizes the coupling level between the patch and the feedline. This approach helps to improve antenna gain, but at the same time leads to a significant level of back radiation due to the microstrip feedline and unwanted surface-wave radiation, especially for the large patch arrays. Using the SIW cavity-backed patch and stripline feedline of the ACF in the element design, therefore, provides a solution to this problem. Thus, a full-corporate feed 32 × 32 array antenna achieves realized gain of 30.71–32.8 dBi with radiation efficiency above 52% within the operational band of 25.43–26.91 GHz. The fabricated antenna also retains being lightweight, which is desirable for UAVs, because it has no metal plate at the backside to support the antenna.