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ABSTRACT The article explores a quad‐port compact (56 × 56 × 1.5 mm3) multiple‐input multiple‐output (MIMO) antenna developed on a colored resin fiber material encompassing enhanced isolation for wideband applications. The design antenna configuration incorporates four ground stubs positioned among antenna pairs on the upper section of the substrate and eight rectangular‐shaped ground slots to enhance antenna isolation. The antenna functions over a broad spectral range from 4.21 to 10.95 GHz, providing coverage for WLAN (5.15–5.35 GHz/5.725–5.825 GHz), C band uplink (5.925–6.425 GHz), downlink defense (7.2–7.7 GHz), and ITU band (8–8.5 GHz), with 88.91% fractional bandwidth. The antenna design ensures exceptional isolation, exceeding 21 dB among orthogonal antennas and 25 dB between oppositely placed antennas across the entire functioning bandwidth. Across the working band, the antenna showcases favorable diversity characteristics, including a lower envelope correlation coefficient (ECC < 0.085), higher diversity gain (DG > 9.95 dB), minimal channel capacity loss (< 0.39 bits/s/Hz), and negligible magnitude variation in mean effective gain among the antenna ports (< 0.1 dB). The acquired total active reflection (TARC) curve exhibits the antenna's robust resonance features over the application band and commendable time domain properties in the active spectral region. The findings of the simulation and measurements revealed a close alignment. [ABSTRACT FROM AUTHOR]

This paper presents a novel additively manufactured wideband dual circularly polarized (CP) open‐ended waveguide (OEW) antenna, which adopts a pair of wedge‐shaped outer ridges acting as a circular polarizer. Study found that compared to the con‐ ventional designs that employ internal polarization converting structures, such outer ridges are capable of achieving wider axial ratio bandwidth (ARBW) and better reflection coefficients. On each ridge, two rectangular slots are designed to suppress the higher order mode caused by the increased waveguide size, and further expanding the ARBW. The proposed antenna is fed by two differential ports. By switching the feeding ports, the CP states can be altered to either right‐handed CP (RHCP) or left‐handed CP (LHCP). In terms of configuration, the proposed antenna has a simple one‐piece structure and is fabricated by using dielec‐ tric 3‐D printing technology. To form the waveguide walls, its partial surfaces are coated by copper films through electroplat‐ ing. The proposed antenna features easy fabrication and light weight. Experimental results show that the proposed antenna has an impedance bandwidth of larger than 47.6% (8–13 GHz) with reflection coefficients lower than −15 dB, while the 3‐dB ARBW is 37.7% from 8.4 to 12.3 GHz. [ABSTRACT FROM AUTHOR]

We analyze square antennas with one and quasi-two sources to reveal the relationship between loop and plate antennas. First, using the moment method, one-source antennas with corner truncation are investigated versus antenna height above the ground plane. As the height increases, the CP wave bandwidth of the plate antenna increases 17% for a 3 dB axial ratio criterion, whereas the loop antenna's bandwidth remains less than 3%. Next, we study quasi-two-source antennas without corner truncation versus antenna height. The plate antenna's bandwidth is found to reach 30%, which is wider than that of a loop antenna by a factor of two. Last, the plate antenna with quasi-two sources is applied in an array antenna, whose properties are compared to those of the corresponding loop antenna array. We present experimental results to verify the simulated results. [ABSTRACT FROM AUTHOR]

In this paper, a planar low-profile wideband circularly polarized substrate-integrated waveguide (SIW) based antenna is investigated. The antenna comprises two substrates stacked over each other. The top layer of the antenna is loaded with a 4 × 4 array of parasitic square patches stacked over a spiral slot loaded in the SIW cavity. The spiral slot is utilized for the generation of narrow band circular polarization and to enhance the CP bandwidth, the parasitic patch array is excited through the electromagnetic coupling mechanism without any air gap between them. The antenna is fabricated and tested to validate the simulated results. A wide relative impedance bandwidth of 33% (8.25–11.55 GHz) and the axial ratio bandwidth of 8.55–9.70 GHz (12.60%) is exhibited. The broadside radiation characteristics are achieved with peak gain of 8.05dBic at 9 GHz. The overall size of the antenna structure is 0.8λ0 × 0.8λ0. The proposed antenna is suitable for various satellite applications. [ABSTRACT FROM AUTHOR]

Two concentric double-loop antennas were analyzed using the moment method to increase the 3 dB axial ratio bandwidth. Each antenna has a driven loop connected to a branched feedline that is vertical to the ground plane. First, a parasitic loop was added outside of the driven one with a spacing of S. It was found that the axial ratio bandwidth has a maximum value of 23% for S = 0.02 wavelengths. Next, we moved a parasitic loop inside of the driven one. It was revealed that the antenna shows an axial ratio bandwidth of 40%, which is three times as wide as that of a single-loop antenna. The analysis results were verified with experimental work. [ABSTRACT FROM AUTHOR]

A wideband circularly polarized (CP) planar endfire magnetic‐electric dipole antenna with single‐layer substrate integrated waveguide (SIW) is presented for millimeter‐wave (mm‐wave) communications. The antenna consists of an SIW feeding line, an electric dipole formed by two tilted shorted stubs and a magnetic dipole produced by an open‐ended SIW. Wideband CP radiation is implemented by simultaneously excited electric and magnetic dipoles in orthogonal phase, and its working principle is analyzed in detail by employing the traveling wave mode along the shorted stubs. The antenna prototype is fabricated and measured as a demonstration, which clearly demonstrates wide impedance bandwidth over 48.9%, wide axial ratio (AR) bandwidth of 46%, novel electric dipole structure, cost‐effective fabrication, and easy integration performance. [ABSTRACT FROM AUTHOR]

A wideband shared-aperture antenna is designed for MIMO application based on asymmetric orthogonal-mode antenna pair. A symmetric T-shaped antenna and an asymmetric double-L-shaped antenna constitute the proposed antenna pair. Two co-planar antenna elements are configured above the ground (on the same substrate side). The wideband self-decoupling characteristic of the antenna pair is achieved via orthogonal modes. The proposed shared-aperture antenna demonstrates good impedance matching, high isolation, and good diversity performance over a bandwidth of 3.04–5.28 GHz, covering the 5G N77/N78/N79 bands, which is suitable for compact 5G MIMO terminals. Two such antenna pairs are arranged along the upper side of the ground to construct a 4-port MIMO antenna. The proposed MIMO antenna is fabricated and tested to verify its performance. Favorable results are realized, including impedance matching, isolation, efficiency, and ECC. The measured results are in good agreement with the simulated results. [ABSTRACT FROM AUTHOR]

This letter introduces a novel wideband, low profile, tightly coupled dipole subarray for wireless communication systems. The proposed subarray, composed of 3 × 3 unit elements, offers a planar structure with high aperture efficiency. The unit element is a bow-tie-shaped tightly coupled dipole antenna covered by a frequency-selective surface for wideband operation. Using power dividers with quarter-wave transformers, the proposed subarray achieved an impressive impedance-matching bandwidth of 28.6–41.6 GHz (37.8%). This wideband performance was maintained in a 4 × 4 array configuration as well. The antenna’s low-profile design (0.08λc) and high aperture efficiency (77.2%) set it apart from existing wideband patch array antennas, making it a promising candidate for future wireless communication applications.

This paper presents a compact wideband circularly polarized cross-dipole antenna with a low-pass filter response. It consists of two pairs of folded cross-dipole arms printed separately on both sides of the top substrate, and the two dipole arms on the same surface are connected by an annular phase-shifting delay line to generate circular polarization. A bent metal square ring and four small metal square rings around the cross-dipoles are employed to introduce new resonant frequencies, effectively extending the impedance and axial-ratio bandwidth. Four square patches printed on the middle substrate are connected to the ground plane by the vertical metal plates in order to reduce the antenna height. Thus, a compact wideband circularly polarized antenna is realized. In addition, a transmission zero can be introduced at the upper frequency stopband by the bent metal square rings, without using extra filter circuits. For verification, the proposed model is implemented and tested. The overall size of the model is 90 mm × 90 mm × 33 mm ( 0.37 λ 0 × 0.37 λ 0 × 0.14 λ 0 ; λ 0 denotes the center operating frequency). The measured impedance bandwidth and 3 dB axial-ratio (AR) bandwidth are 53.3% and 41%, respectively. An upper-band radiation suppression level greater than 15 dB is realized, indicating a good low-pass filter response. [ABSTRACT FROM AUTHOR]

This paper presents a wideband dual-polarized dipole antenna structure operating at 1.7–3.8 GHz (76.4%). For a traditional 4G dipole antenna that covers the band 1.71–2.69 GHz, it is difficult to maintain the satisfactory impedance matching and normal stable radiation patterns within the 5G sub-6 GHz band 3.3–3.8 GHz, mainly due to the fixed antenna height no longer being a quarter-wavelength. To solve this, a connected-ring-shaped metasurface structure is proposed and deployed to operate as an artificial magnetic conductor (AMC). As a result, stable antenna radiation patterns are obtained within the whole band 1.7–3.8 GHz. For verification, this wideband dipole antenna using AMC is implemented and tested. The measured results show that the proposed antenna has an impedance bandwidth of 80.7% (1.7–4.0 GHz). It has an average measured in-band realized gain of  7.0 ± 1.0  dBi and a stable  70 ± 5  half power beam width (HPBW) within the 4G/5G-sub 6GHz bands 1.71–2.69 GHz and 3.3–3.8 GHz. [ABSTRACT FROM AUTHOR]

It is necessary to have a reconfigurable antenna for multi-function radar. The same antenna can be used for search, tracking, and imaging applications across a wide range of frequencies. The monopole antenna is suitably etched in its patch to achieve ultra-wideband (UWB) performance, while the modification of the partial ground to have an electromagnetic band gap (EBG) structure and rectangle slots improves the operational bandwidth that extends between 2.7 GHz and 12 GHz. The inclusion of a stub in the microstrip feed along with partial ground brings size miniaturization up to 63%. The perturbation of "L"-shaped slots at the corners of the rectangular patch and loading of left-hand metamaterial (LHM) into the monopole antenna realize circular polarization and also increase the gain of the antenna to 5.68 dBi. The inclusion of a filter across the feedline of the proposed antenna modifies the antenna's frequency/bandwidth in some desirable fashion, which provides bandwidth reconfiguration. The proposed antenna uses a step feed that offers better impedance matching over the wide operating bandwidth. [ABSTRACT FROM AUTHOR]

A dual-wide-band triple resonance half mode substrate integrated waveguide (HMSIW) cavity-backed antenna with an extra shorting via is presented in this paper. Three modes of the HMSIW cavity are utilized to generate the dual-wide-band resonances. The HMSIW cavity along with three rectangular slots is fed coaxially which helps in achieving triple resonance and size miniaturization. An additional shorting via is loaded at the position of electric null between the 2nd and 3rd modes to bring the modes closer and couple them. The antenna exhibits one narrow band and one wide-band response. The dual-wide-band antenna is fabricated and tested on a low-profile substrate of 0.05 λg. A relative bandwidth of 1.03% (10.58–10.69 GHz) and 6.12% (12.47–13.25 GHz) is attained by the two bands. A stable broadside and unidirectional radiation pattern is achieved with a peak gain of 4.5 dBi, 5.81 dBi, and 6.18 dBi at 10.6 GHz, 12.68 GHz, and 13.2 GHz, respectively. Thus, the proposed dual-wide-band antenna can be effectively utilized for satellite applications. [ABSTRACT FROM AUTHOR]

In this work a broadband Magnetoelectric (ME) dipole antenna for the Global Navigation Satellite System (GNSS) applied to nanosatellites is proposed. The antenna consists of a reflective cavity with open walls containing four gaps to enhance the axial ratio (AR) bandwidth. Additionally, it includes two ME dipoles formed by two pairs of vertical and horizontal copper plates, one of which is trapezoidal and a T-Γ-shaped cross-feeding structure. A prototype was designed and subsequently manufactured and measured. The experimentally obtained results exhibit consistent agreement with simulated outcomes, demonstrating that the antenna has a wide impedance bandwidth of 111.36% from 1.13 GHz to 1.62 GHz for the Voltage Standing Wave Ratio (VSWR) ≤ 2 and a 3 dB AR bandwidth of 120.45% from 1.10 GHz to 1.63 GHz. Within this range, high gain (≥8.5 dBi) and high radiation efficiency (90%) can be achieved. Furthermore, the antenna exhibits right-hand circular polarization (RHCP) and possesses good unidirectional radiation characteristics with a high front-to-back ratio (≥ 20 dB). [ABSTRACT FROM AUTHOR]

In this article, we present new design techniques to improve the gain and impedance bandwidth of short backfire antennas. For the gain enhancement procedure, our approach was to flare the rim of the antenna, which simultaneously led to an increase in the impedance bandwidth of the antenna. Parametric studies were carried out to obtain the optimal flaring angle. The peak realized gain was obtained as 17.2 dBi with an impedance bandwidth of 55% (2.4 dB and 28.6% increase in gain and bandwidth, respectively, compared to the unflared antenna). To further enhance the impedance bandwidth, an inductive iris was added to improve impedance matching at the waveguide aperture. We varied the width of the iris to obtain the optimal width that provided the best gain and impedance bandwidth result of 17.1 dBi and 66% (~40% increase compared to the unflared antenna without iris). To experimentally verify the work, prototypes were fabricated and tested. We found good agreement between simulation and measurement. The results of this study indicate that gain and bandwidth can be enhanced through optimized geometrical modification of the SBF structure. Furthermore, our 3D-printed technique demonstrates a mass reduction compared with conventional metallic structures. [ABSTRACT FROM AUTHOR]

This paper presents a planar multiple-input-multiple-output (MIMO) antenna with dual circular polarization (CP) and a simple geometry for millimetre-wave band. The proposed design is featuring a fully grounded coplanar waveguide (CPW) and a systematically perturbed feedline radiator. The symmetry of the electric field is disrupted using varying stub sizes and offsets between the stubs, resulting in wideband operation and circularly polarized waves. Following full optimization of the physical parameters, the numerical design is validate experimentally. The results indicate that the proposed antenna design achieves a −10 dB impedance bandwidth from 24.6 GHz to 32.1 GHz, with an axial ratio (AR) of 3 dB or less from 26 GHz to 31.8 GHz. The peak realized gain is 10.3 dBic, with steady broadside radiation. The envelope correlation coefficient (ECC) is 0.01, and the diversity gain is 10 dB across the operating band. The planar structure and the wideband performance of the proposed design makes it suitable for application necessitating fix beam applications in the mm-wave band.

Abstract In this work a broadband Magnetoelectric (ME) dipole antenna for the Global Navigation Satellite System (GNSS) applied to nanosatellites is proposed. The antenna consists of a reflective cavity with open walls containing four gaps to enhance the axial ratio (AR) bandwidth. Additionally, it includes two ME dipoles formed by two pairs of vertical and horizontal copper plates, one of which is trapezoidal and a T-Γ-shaped cross-feeding structure. A prototype was designed and subsequently manufactured and measured. The experimentally obtained results exhibit consistent agreement with simulated outcomes, demonstrating that the antenna has a wide impedance bandwidth of 111.36% from 1.13 GHz to 1.62 GHz for the Voltage Standing Wave Ratio (VSWR) ≤ 2 and a 3 dB AR bandwidth of 120.45% from 1.10 GHz to 1.63 GHz. Within this range, high gain (≥8.5 dBi) and high radiation efficiency (90%) can be achieved. Furthermore, the antenna exhibits right-hand circular polarization (RHCP) and possesses good unidirectional radiation characteristics with a high front-to-back ratio (≥ 20 dB).

A wideband wide-scan array based on dual-polarized elements is presented in this paper. The proposed element consists of two flared metallic wings and two shorting posts over a ground plane which is excited by a RF connector vertically. Without complex feeding network, the antenna element features wideband, low-profile, and high power handling capability. Besides, elements do not require electrical connection and can be arranged with gaps between neighbors, allowing for modular construction. The dual-polarized array in a square lattice can achieve wideband wide-scan performance. To verify the design, an $11\times 11$ prototype has been fabricated and measured. The measurements of this prototype are presented and are in good agreement with the simulations. The results reveal that the array element can achieve a relative bandwidth of 100% for VSWR $\le 3$ at scans out to $\theta \,\, = \,\, 45^{\circ }$ and an enhanced gain of 1 dB in lower frequency band. The array can obtain better than 20 dB polarization purity at 4 GHz and scan loss of lower than 3 dB over the band, respectively.

A wideband ultra-low-profile Yagi-Uda type of solar-cell integrated antenna is presented. The proposed antenna consists of a driver, reflector, and director, and is also designed to function as a solar cell. An ultra-low-profile copper indium gallium selenide (CIGS) based solar cell is used as a driver, and a slit is cut from it to make a built-in solar-cell antenna. A CIGS solar cell-based reflector and director are added to increase the impedance bandwidth and gain of the proposed antenna. A narrow slit is used, and the spacings between the reflector, driver, and director are minimized to increase the solar-cell form factor. A coaxial-to-microstrip line transition type feeding structure is used to excite the antenna, which is printed under the second substrate. Three RF decoupler circuits are designed for the driver, reflector, and director to separate the antenna functionality from the solar cell. The antenna has overall dimensions of $0.71~\lambda _{o} \times 0.61~\lambda _{o} \times 0.006~\lambda _{o}$ at 3.2 GHz. Furthermore, the proposed antenna design possesses a wide measured impedance bandwidth of 56.7%, radiation efficiency of higher than 90%, a maximum measured gain of 5.67 dBi within the impedance bandwidth, and a solar-cell form factor of 89.7% with no optical blockage.

The growing prevalence of IoT devices has heightened the focus on minimizing energy consumption in low-power electronic systems. Ambient radio frequency (RF) energy harvesting allows self-sustaining electronic devices to operate in IoT networks without cables, batteries, or allocated energy sources. This paper presents an innovative printed dual-band dual-polarized antenna designed for ambient RF energy harvesting in IoT applications. The proposed antenna targets efficient RF energy conversion from the most prevalent cellular frequency bands (sub-1 GHz and 1800 MHz) and sub-700 MHz Digital Terrestrial Television. This antenna is a significant advancement in the field, boasting a wide circularly polarized 610-968 MHz bandwidth and a linearly polarized bandwidth covering the GSM/4G 1800 MHz band. The antenna’s integration with a rectifier circuit demonstrates its ability to convert ambient RF energy into electrical power, regardless of the source antenna orientation. This integrated antenna development significantly reduces battery dependency in low-power IoT devices, paving the way for more sustainable and versatile wireless networks. Specifically, this antenna is crafted to achieve broad CP and adequate impedance bandwidths across targeted frequencies, crucial for the diverse requirements of ambient RF energy harvesting. Such a design meets our primary objectives of capturing RF energy effectively, with its omnidirectional pattern enabling it to collect ambient RF signals from different polarizations and directions.

A wideband, high gain circularly polarized (CP) metasurface (MTS) based slot antenna is presented. The designed nonuniform slots provide wider bandgap regions and extra degree of freedom in tuning to obtain wider impedance bandwidth through improved mode coupling for fixed optimum feed location along with improved 3-dB axial ratio bandwidth and gain. The extra radiation edges provided by nonuniform slots within the unit cell help in improving mode coupling thus resulting in increased performance of the designed antenna. Improved mode coupling in case of the proposed antenna is explained and verified using characteristic mode analysis (CMA). The proposed antenna with a small size of 0.8 x 0.8 x $0.079~\lambda _{0}^{3}~(\lambda _{0}$ at 6 GHz) is designed. Based on the proposed analysis, an antenna having wide impedance bandwidth of 48.74% (5.74-9.44 GHz), and a 3-dB axial ratio (AR) bandwidth of 19.92% (6.19-7.56 GHz) with a peak gain of 9.35 dBi is designed. In addition, a 2 x 2 array of proposed MTS is designed and fabricated. The MTS array has a peak gain of 14.45dBi with a 3-dB AR bandwidth of 61.75% and impedance bandwidth of 71.71%. The proposed antennas find good use in WiMAX, C-band, and radars applications.

The present study provides a wideband high-gain monopulse antenna based on a dielectric lens operating in X- and Ku-bands, in which a wideband dielectric lens is designed and employed to fulfill the radiation pattern and bandwidth necessities of a monopulse antenna. The proposed configuration has four horns allowing for the simultaneous creation of $\Delta $ and $\Sigma $ designs in two perpendicular planes. The main advantages of the proposed dielectric lens are low cost, lightweight, and easy fabrication using 3-D printing technology. The measurement findings show that the peak gain of the sum pattern is 28.9 dBi with a peak aperture efficiency of 60% over the desired frequency bandwidth. The suggested design can produce a simultaneous sum and two distinct difference patterns in orthogonal planes, meeting the rigorous demands for speed and accuracy in tracking applications.

In this study, a dual-feed polarization diversity antenna with a broadside or conical radiation pattern is proposed for fifth-generation (5G)-NR applications. The antenna’s design incorporates a radiator created using a circular slot, segmented into two semicircular slots by a protruding stub. By adjusting the phase difference applied to these two semi-circular slots, different radiation patterns within the same frequency band can be achieved. A modified 180° rat-race coupler served as the feed structure. By analyzing current distribution and E-field distribution, the phase difference formed in the two semi-circular slots according to the input terminal is confirmed. The measurement results showed that the proposed antenna exhibited polarization diversity characteristics across a bandwidth of 12.7% ( $3.24\sim 3.7$ GHz), with isolation exceeding 25 dB between the two input terminals. In this case, the measured gains are 5.2 dBi for Port 1 and 3.5 dBi for Port 2.

In this study, we propose a sensor for partial discharge (PD) sensing based on an electrically small hybrid spiral antenna, measuring approximately 0.087 wavelengths in diameter at 200 MHz. The sensor utilizes a hybrid design that integrates equiangular and Archimedes spiral antennas. Spiral antennas encounter significant gain loss when the wavelength exceeds their circumference, limiting their low-frequency performance. This can impede the early detection of PD, as the initial electromagnetic (EM) PD signature is concentrated at the low-frequency end of the ultrahigh frequency (UHF) band. In addition, PD sensors are often enclosed within a metallic cavity to shield them from surrounding noise. However, this further exacerbates the challenges of low-frequency performance, with the band of interest potentially falling well below the cavity cutoff frequency. In this study, we alleviate this limitation by integrating a capacitively loaded ring resonator with the spiral antenna, thereby enhancing its low-frequency gain without increasing the antenna size. Experimental results from a prototype sensor with an aperture diameter of 130 mm demonstrate that the proposed ring resonator increases the realized gain in a relatively wide bandwidth from 220 MHz to 650 MHz by as much as 18.3 dB, with minimal impact observed at higher frequencies. Moreover, in situ PD detection test results demonstrate an improvement of 0.6 dB in the mean received power, along with a spectral efficiency improvement in the frequency range of 290–525 MHz, with a peak improvement of 21.2 dB in the received power spectral density (PSD) at 410 MHz.

This paper proposes a wearable reconfigurable antenna which can be operated in sub-6GHz, V-band and D-band. In the sub-6GHz band, the dual loop antennas are combined with a diode switch to achieve multi-mode switching. In the V-band, a controllable beam from 0 to 360 degrees is achieved by using six combined Vivaldi antennas with a diode switch to switch between beam directions. The diamond-shaped monopole antenna designed for the D-band achieves extremely high transmission rates at close range and has upward-facing directional radiation. The antennas are available in the sub-6 GHz bands such as 2–2.4, 2.9–3, 4.3–4.7, 5.75–6.05, and 6.6–6.9 GHz. The antenna design in the V-band can cover 19.78% (41-50 GHz) of the fractional bandwidth with a reflection coefficient below the −10 dB standard. In the D-band diamond monopole antenna, the reflection coefficient can reach −10dB standard covering 16.25% (139.6–164.3GHz) of the fractional bandwidth, and with directional radiation, the maximum radiation can reach 12dBi.

This work introduces a Ka-band coaxial horn antenna that incorporates a specialized dielectric supporting structure and a transition to a 2.4 mm connector. The inner and outer radii of the coaxial aperture were sized using an approximated model for an open-ended coaxial waveguide. The theory of small reflections was then used to account for the reflection coefficient resulting from an additional cascading cylindrical-conical section. A refined numerical model, representing more accurately a prototype, featured a transition region to standardized connectors and a dielectric structure that offers mechanical support for the inner conductor and impedance matching. Ansys HFSS full-wave electromagnetic finite-element method solver was used to compute the parameters of the antenna, and a genetic algorithm optimizer was employed to improve the performance of the complete coaxial horn. A prototype was fabricated using metal additive manufacturing for the inner and outer horn conductors, while the dielectric support was created using 3D polymer printing. Experimental measurements demonstrate that the prototyped antenna has an impedance bandwidth of above 79.36% (19–44 GHz), a peak realized gain of 11.53 dBi, and a maximum efficiency of 89.83%. Additionally, a sensitivity analysis was conducted to evaluate the potential impact of additive manufacturing imperfections and assembly errors on the antenna’s performance.

A multiband microstrip-fed wideband (WB) antenna with filtering notches is described for $3 \mathrm {G} / 4 \mathrm {G} / 5 \mathrm {G}$ applications. The proposed antenna comprises three notch bands by etching a modified inverted U-slot, a square ring slot, and an interdigital inductor slot on the patch element and feedline. The antenna resonates at $1.9,2.3$ , and $3.5 \mathrm {~GHz}$ due to the resonant components’ mutual interaction, which eliminates interference at other frequencies. The antenna’s measured $S_{11}$ are $18.79 \mathrm {~dB}$ at $1.9 \mathrm {~GHz},-24.8 \mathrm {~dB}$ at $2.4 \mathrm {~GHz}$ , and $-40.6 \mathrm {~dB}$ at $3.5 \mathrm {~GHz}$ , showing a multiband function with a band-reject level of $0.4 \mathrm {~dB}$ . The VSWR is less than two at all resonant frequencies. The effects of altering the notch dimensions on the $S_{11}$ and VSWR were explored. The antenna was developed and tested using a Rogers RT/Duroid 5880 substrate. The agreement between measured and simulated results was satisfactory. The $S_{11}$ result was validated using the ADS schematic and machine learning techniques. The proposed triband-notched antenna offers encouraging results, with radiation patterns exhibiting omnidirectional characteristics and effective performance within the required frequencies. Current distribution analysis reveals how notches disrupt surface current and lower radiation at specific frequencies. The antenna’s gain and efficiency performed satisfactorily in the stated frequency ranges.

A completely embedded, planar, dual-element dielectric based antenna directly fed by a substrate integrated insulated guide within the same layer in Sub-THz band is presented in this paper. A dielectric layer is employed to make the structure stable. The proposed structure is compatible with the standard planar millimeter-wave and terahertz manufacturing technologies. To minimize the reflection loss, matching air holes inside the guiding channel of the waveguide and air holes with a smaller perforation radius surrounding the antenna are created. The proposed compact antenna, which has been successfully tested, covers the frequency range of 234.5-278.1 GHz with a measured impedance bandwidth of 17.01%, a proper simulated average radiation efficiency of 93.6%, and a maximum gain as well as average gain of 16.08 dBi and 12.56 dBi from measurement results, respectively. Because of these features, the suggested antenna would be a great candidate for short-range wireless applications in Sub-THz frequency bands.

A class of dielectric filtering inverted-L antenna with reflective- and quasi-reflectionless-type radiation nulls is proposed to achieve wideband or dual-band operation. To this aim, a dual-function dissipative branch is exploited, which is in-parallel loaded at the feedline of the microstrip-fed dielectric inverted-L antenna. This absorptive branch, which is terminated in a grounded resistor, exhibits a quasi-complementary frequency response with regard to the one of the antenna. In this manner, it can mostly absorb the out-of-band RF-signal power not radiated by the antenna, hence creating quasi-reflectionless-type radiation nulls. Furthermore, the loaded branch can also generate a notch band giving rise to a reflective-type radiation null, which comes determined by the length of the branch and it is independent of the quasi-reflectionless radiation nulls. Thus, by controlling the spectral location of the notch band out of or within the operational frequency band of the dielectric inverted-L antenna, wideband or dual-band operational capabilities can be functionalized into it. For experimental-validation purposes, proof-of-concept prototypes for the two devised wideband and dual-band antenna approaches are designed, manufactured, and characterized. The measured results are in reasonably-close agreement with the simulated ones. The measured fractional impedance bandwidths of the two antenna prototypes are 28.3% (wideband one), 3.1% and 4.2% (dual-band one), respectively.

This paper introduces a novel filtering approach that employs integrated periodic structures with a conventional Vivaldi antenna to achieve a fully integrated bandpass filtering antenna. The approach results in a wide out-of-band suppression, high passband selectivity, adjustable operational bandwidth, and low insertion loss. The proposed filtering approach maintains the original size of the conventional Vivaldi antenna (base antenna) without requiring additional modifications. To validate the approach, we present two filtering Vivaldi antennas: filtering antenna I (center frequency: 18GHz, fractional bandwidth: 21%, insertion loss: 0.32dB) and filtering antenna II (center frequency: 6.5GHz, fractional bandwidth: 12%, insertion loss: 0.6dB). Their wide out-of-band gain suppression (typically $\geq 15$ dB) covers the conventional Vivaldi antenna’s frequency range (4-24GHz). A prototype of the filtering antenna I is manufactured. Its measurement results validate the proposed approach and show good agreement with the simulated reflection coefficient, realized gain, and radiation patterns. The features of the proposed filtering antenna approach, make it suitable for various applications requiring efficient frequency filtering.

A millimeter-wave wideband filtering on-chip antenna is proposed in this paper. Its operation frequency covers 32 GHz to 63 GHz, and the impedance fractional bandwidth reaches 63%. Based on the corner-fed patch antenna, the antenna in this work has a quasi-omnidirectional radiation pattern, and peak efficiency reaches 91.7%. By square slotting on the four sides of the patch and cross slotting on the center of the patch, the high-order mode is suppressed, which supports the wide operating frequency range with filtering characteristics. Split ring resonators are etched on the ground to strengthen filtering characteristics. Based on thin-film integrated passive device (IPD) technology, the proposed structure is applicable to the on-chip wideband and high-efficiency antenna array. [ABSTRACT FROM AUTHOR]

This work presents a printed Ka-band dipole array antenna with wide bandwidth for millimeter-wave communication applications. The operating band of the proposed antenna ranges from 27.8–38.2 GHz exhibiting a wide bandwidth of 10.4 GHz. A balun structure is designed with interlaced U-shaped bending lines on the upper and lower metal layers to feed the dipole differentially. Parasitic trapezoidal patches are exquisitely placed adjacent to the driven dipoles for coupling, which can enhance bandwidth significantly through multiple resonances. The low-frequency radiation is mainly contributed by the resonance of the dipole, while the high-frequency radiation is affected by both the dipole and the parasitic trapezoidal patch. Due to the trapezoidal patch, the equivalent path length of the resonant current becomes shorter, thus supporting high-frequency resonance. A prototype of the proposed 1 × 2 dipole array antenna was fabricated for validation. The measured –10-dB impedance bandwidth is up to 27.8∼38.2 GHz (or 31.5%) and the realized gain is as high as 8 dBi, which is suitable for advanced millimeter-wave communication applications. [ABSTRACT FROM AUTHOR]

In this work, a wideband compact circularly polarized (CP) antenna using a novel polarization‐rotated metasurface (MS) structure is presented. First, the polarization‐rotated MS structure is designed by using a complementary L‐shaped MS unit cell. By optimizing the width of diagonal gap and radius of corners, the amplitude and phase of its surface impedances along ±45° can be adjusted respectively, and then a large polarization‐rotated bandwidth of 44.4% can be obtained. Secondly, the modal behaviors of the proposed MS are also investigated by adopting characteristic mode analysis (CMA) to explore feasible CP radiation. Furtherly, the proposed MS is applied to construct a wideband CP MS‐based antenna by combining with a coupling slot. The experimental results show a large 3‐dB axial ratio (AR) bandwidth (~31.1%), a large 10‐dB impedance bandwidth (~41.8%) and a compact size of 0.63λ0 × 0.63λ0 × 0.08λ0, verifying that the proposed antenna can be applied to realize a high‐quality vehicular communication. [ABSTRACT FROM AUTHOR]

This letter presents a coplanar waveguide‐fed printed monopole antenna backed by an artificial magnetic conductor (AMC) reflector. The proposed monopole antenna achieves circular polarization by loading the monopole with a printed coil and using an asymmetric ground plane. In addition, the AMC increases the antenna gain while maintaining a wide axial ratio (AR) bandwidth. The unit cell of the AMC is based on a Minkowski‐like prefractal geometry. The antenna is fabricated and measured with a total size of 1.07 λ0 × 1.07 λ0 × 0.25 λ0 at the operating frequency of 8.5 GHz. The measured results show a wide −10 dB impedance bandwidth of 26.9% (7.12–9.38 GHz), a wide 3 dB AR bandwidth of 22.23% (8–9.89 GHz) as well as a peak gain of 8.3 dBi at 8.5 GHz. This is significantly better than comparable antennas in addition to this design being the smallest in size. [ABSTRACT FROM AUTHOR]

A U-slot located symmetrically at the centre of the patch has been utilized to enhance the patch antenna's operating bandwidth compared to the standard conventional patch. The operating frequency range of the circumferential patch antenna is from 8.61 to 11.43 GHz, while the axial patch covers the frequency range 8.71 to 11.33 GHz (covering X band). The antenna shows excellent gain with minimal variation in both E and H-planes across the operating frequency range. Moreover, the antenna achieves less than −10 dB sidelobe levels in both E and H-planes across all frequencies and configurations. The co and cross-polarization plots are also depicted to show the excellent polarization purity of the antenna for the planar and cylindrical conformal configurations. The antenna may be suitable for airborne applications where the conformability to the Arial host body is of prime importance. [ABSTRACT FROM AUTHOR]

A new zigzag‐shaped bridge feeding structure (ZBS) for patch antennas is proposed in this letter. The feeding structure consists of a zigzag‐shaped strip and two metal piers (left one is coaxial feed pin, the other is short post connect to ground.) The length of the strip is approximately half wavelength to the low‐frequency resonance point, while the distance between the two piers is approximately half wavelength of higher resonance point. The ZBS can excite two resonances to enhance bandwidth. This letter provides an intuitive explanation of its working principle from the perspective of electromagnetic fields. A prototype patch antenna working in the frequency range of 2.42–3.22 GHz was designed, simulated, and manufactured. The results show that the designed antenna achieved a wide working bandwidth of 28% (|S11|<−10 dB), low cross‐polarization (<23 dB), and a good average gain of 8.3 dBi. [ABSTRACT FROM AUTHOR]

This article presents a 6×6 MIMO array optimized for sub-6 GHz mobile and wireless applications. Utilizing a partial ground plane (PGP), the array incorporates a single-element half-circle-slotted monopole antenna to achieve a wideband response. The compact design, measuring 75 × 150 mm² and only 0.508 mm thick, is engineered to fit 6.6-inch display smartphones. Operating between 2.82 and 5.95 GHz, the array offers a -10 dB bandwidth and a VSWR of less than 2. It also delivers port-to-port isolation less than -20 dB and a peak realized gain of 5.3 dBi, with an antenna efficiency of 71%. Comprehensive far-field radiation patterns are observed across all 6 ports. The array maintains an envelope correlation coefficient (ECC) under 0.004 and a diversity gain (DG) above 9.98, demonstrating robust performance. Specific absorption rate (SAR) results at 3.5 GHz confirms compliance with MIMO standards, with values as low as 0.13 W/kg. This high-performance MIMO array is a strong contender for sub-6 GHz 5G applications. [ABSTRACT FROM AUTHOR]

In this article, a novel low profile wideband high gain stacked microstrip antenna (MSA) array is proposed. This technique of enhancing gain and bandwidth of MSA array is novel and unique and not reported in literature to the best of authors' knowledge. Bandwidth of MSA array is enhanced using reactive impedance surface (RIS) and slotted artificial magnetic conductor (AMC) surfaces while gain of the antenna is improved using four parasitic patches (PPs) placed above the patches of 2×2 MSA array for the first time. Electromagnetic coupling among nearby resonant frequencies of patches of MSA array, RIS, slotted AMC and PPs, provide wide bandwidth. The proposed structure is simple to design and has low profile and smaller dimensions. The antenna provides 12.3 dBi peak gain and 24.6% bandwidth from 5.0-6.4 GHz, which covers 5G, WLAN, and satellite C-band. 1.52 0×1.52 0 × 0.1 0 antenna has Front to back lobe (F/B) ratio >20dB, side lobe level (SLL) <-20 dB and cross-polar level (CPL) <-18 dB. 0 is freespace wavelength at 5.7GHz. The structure offers better radiation parameters, smaller dimensions, and simple design techniques than the reported state of art antennas in the literature. The measured results of prototype fabricated antenna agree with simulated results. The proposed antenna is suitable for transceiver where the two WLAN bands can be used separately for transmission and reception, access point, 5G-V2X and satellite communication. [ABSTRACT FROM AUTHOR]

A wideband differentially fed circularly polarized (CP) antenna featuring a slotted patch design with a large beamwidth is presented. The final design of the differentially fed CP antenna, aimed at achieving high gain and a wide axial ratio (AR) bandwidth, involves coupling a differential bending dipole antenna to the slotted patch in the same plane. The presented differentially fed CP antenna demonstrates characteristics of a large AR beamwidth, as verified by simulation and experiment. The measured AR beamwidths of 132.3° in the xoz plane (phi = 0°) and 116.2° in the yoz plane (phi = 90°) are realized at 5.5 GHz. The measured result exhibits broadband performance with a −10-dB impedance bandwidth of 78.8% (3.81–8.76 GHz), a 3-dB AR bandwidth of 36.7% (4.78–6.93 GHz), and a maximum gain of 10.2 dBic.

The proposed antenna introduces a wideband double-resonance substrate-integrated waveguide (SIW) cavity-backed slot antenna with shorting vias. The antenna is compact and has a wide frequency range. By loading the SIW cavity slot with shorting pin/vias, the authors describe the mechanism of operation and electric field distributions of the double resonance antenna. By etching the HBT-CRS at the center of the cavity, which creates the dual modes. One is an upward shift in the lowest mode (TE 120 mode or TE 210 mode) and a downward shift in the highest mode (TE 320 modes/TE 230 modes), and these two are paired together. As a result, the fabricated antenna has a very large bandwidth and a strong sense of double resonance. The antenna is designed, and then prototypes are built and tested. The key benefits are compactness, low fabrication cost, performance, and ease of integration with planar circuitry. SIW antennas are impactful in present wireless communication systems. A simulated double resonance design antenna with a low profile of 0.05 λ0 (free-space wavelength) has a bandwidth of 1.854 GHz (frequency range varies from 12.58 - 14.38 GHz and fractional bandwidth of 13.93%) and a peak gain of 6.56 dBi across the whole bandwidth while measured bandwidth is 2 GHz (frequency range from 12.5 - 14.5 GHz and fractional bandwidth of 14.81%) and the gain over the entire bandwidth is 6.46 dBi. In addition, the antenna has outstanding unidirectional radiation characteristics for Ku band applications.

Two concentric double-loop antennas were analyzed using the moment method to increase the 3 dB axial ratio bandwidth. Each antenna has a driven loop connected to a branched feedline that is vertical to the ground plane. First, a parasitic loop was added outside of the driven one with a spacing of S. It was found that the axial ratio bandwidth has a maximum value of 23% for S = 0.02 wavelengths. Next, we moved a parasitic loop inside of the driven one. It was revealed that the antenna shows an axial ratio bandwidth of 40%, which is three times as wide as that of a single-loop antenna. The analysis results were verified with experimental work.

This paper discusses the design and performance of a frequency reconfigurable antenna for Internet of Things (IoT) applications. The antenna is designed to operate on multiple frequency bands and be reconfigurable to adjust to different communication standards and environmental conditions. The antenna design consists of monopole with one PIN diode and 50Ω feed line. By changing the states of the diode, the antenna can be reconfigured to operate in a dual-band mode and a wideband mode. The performance of the antenna was evaluated through simulation. The antenna demonstrated good impedance matching, acceptable gain, and stable radiation patterns across the different frequency bands. The antenna has compact dimensions of (26×19×1.6) mm³. It covers the frequency range 2.95 GHz -8.2 GHz, while the coverage of the dual- band mode is (2.7-3.8) GHz and (4.57-7.4) GHz. The peak gain is 1.57 dBi for the wideband mode with omnidirectional radiation pattern. On the other hand, the peak gain of the dual-band mode is 0.87 dBi at 3 GHz and 0.47 dBi at 6 GHz with an omnidirectional radiation pattern too. [ABSTRACT FROM AUTHOR]

A low‐profile Ku/K band circularly polarized phased array antenna based on crossed dipole and four parasitic elements is presented. Four parasitic patches and the outline of dipole arms which are designed as an exponentially gradual curve are intended to broaden impedance bandwidth. For better integrated design, the plated through holes at the bottom of substrate replaces the metal cavity, aiming to enhance the radiation characteristics of the positive z ${\boldsymbol{z}}$ direction. The small angle sequential ro0tation tech is adopted to further increase the axial ratio (AR) bandwidth. The 8 × 8 antenna array is operated from 15.5 to 23.5 GHz (41%), with the size of 56 mm × 56 mm × 2.54 mm. In the operating frequency, the array demonstrates an average peak realized gain of 24.3 dBic and has a 3‐dB AR beamwidth with scanning angle from −60° to 60° in the plane of ɸ = 0° and ɸ = 90°. [ABSTRACT FROM AUTHOR]

In this study, a novel microfluidic frequency reconfigurable and optically transparent water antenna is designed using three-dimensional (3D) printing technology. The proposed antenna consists of three distinct parts, including a circularly shaped distilled water ground, a sea water-based circular segmented radiator, and a circularly shaped distilled water-based load, all ingeniously constructed from transparent resin material. The presented antenna is excited by a disk-loaded probe. The frequency of the antenna can be easily tuned by filling and emptying/evacuating sea water from the multisegmented radiator. The radiator consists of three segments with different radii, and each segment has a different resonant frequency. When the radiator is filled, the antenna resonates at the frequency of the segment that is filled. When all the radiator segments are filled, the antenna operates at the resonant frequency of 2.4 GHz and possesses an impedance bandwidth of 1.05 GHz (40%) in the range of 2.10–3.15 GHz. By filling different radiator segments, the frequency could be tuned from 2.4 to 2.6 GHz. In addition to the frequency-switching characteristics, the proposed antenna exhibits high simulated radiation efficiency (with a peak performance reaching 95%) and attains a maximum realized gain of 3.8 dBi at 2.9 GHz. The proposed antenna integrates water as its predominant constituent, which is easily available, thereby achieving cost-effectiveness, compactness, and transparency characteristics; it also has the potential to be utilized in future applications, involving transparent and flexible electronics. [ABSTRACT FROM AUTHOR]

The proposed antenna introduces a wideband double-resonance substrate-integrated waveguide (SIW) cavity-backed slot antenna with shorting vias. The antenna is compact and has a wide frequency range. By loading the SIW cavity slot with shorting pin/vias, the authors describe the mechanism of operation and electric field distributions of the double resonance antenna. By etching the HBT-CRS at the center of the cavity, which creates the dual modes. One is an upward shift in the lowest mode (TE 120 mode or TE 210 mode) and a downward shift in the highest mode (TE 320 modes/TE 230 modes), and these two are paired together. As a result, the fabricated antenna has a very large bandwidth and a strong sense of double resonance. The antenna is designed, and then prototypes are built and tested. The key benefits are compactness, low fabrication cost, performance, and ease of integration with planar circuitry. SIW antennas are impactful in present wireless communication systems. A simulated double resonance design antenna with a low profile of 0.05 λ 0 (free-space wavelength) has a bandwidth of 1.854 GHz (frequency range varies from 12.58 - 14.38 GHz and fractional bandwidth of 13.93%) and a peak gain of 6.56 dBi across the whole bandwidth while measured bandwidth is 2 GHz (frequency range from 12.5 - 14.5 GHz and fractional bandwidth of 14.81%) and the gain over the entire bandwidth is 6.46 dBi. In addition, the antenna has outstanding unidirectional radiation characteristics for Ku band applications. [ABSTRACT FROM AUTHOR]