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Ultra-thin copper foil (UTCF) is the basic material for the electronic industry. However, most of them suffer common problem of low strength and wrinkles. Here, 5-µm UTCF with smooth surface (Rz = 1.68 µm) and high tensile strength (~ 340 MPa) was prepared on the surface of conventional 18-µm copper foil. The 18-µm copper foil acted as a supporting carrier and we call it carrier copper foil. We selected gelatin as the additive in the plating solution and deeply investigated its impact on the surface roughness and tensile strength of UTCF. The results suggest that gelatin refines the shape of the grain and is more favorable to the copper foil the orientation (111) texture which benefits the low profile and high tensile strength. The optimal concentration of gelatin is about 0.2 g/L. Its microstructures as well as the mechanical properties were further analyzed by scanning electron microscopy, electron backscattered diffraction and X-ray diffraction. [ABSTRACT FROM AUTHOR]

Summary: This article presents a novel wearable frequency selective surface (FSS) for shielding the communication link of implantable devices with the external environment. The proposed shield blocks a dual‐band frequency operating at 404 MHz and 2.45 GHz in the medical implant communication service (MICS) and industrial, scientific, and medical (ISM) bands. The two distinct stop bands provide a high‐frequency band ratio of 6.02 in an ultra‐miniaturized physical form factor of 0.024λo × 0.024λo, with at least 76.96% miniaturization when compared to the existing art. Each of the unit cells is imprinted on a conformal 50 μm polyester substrate in a symmetrical configuration. The polyester adheres with jean to realize its compatibility with wearable applications. The designed shield system offers a low profile of only 0.00146λo. By suppressing the grating lobe, the proposed shield achieves a high angular stability of 80° and polarization insensitivity of 90° in both transverse electric (TE) and transverse magnetic (TM) modes. The FSS is fabricated and measured results validate its performance. To evaluate the physical insight, an equivalent circuit model (ECM) analysis is done. To ensure durability, the proposed shield system is tested with Amitech SDR04. [ABSTRACT FROM AUTHOR]

A low-profile wide-angle coverage antenna for Ad Hoc communication networks is presented in this letter, which consists primarily of a rotationally symmetrical structure with a microstrip patch antenna positioned at its center. Utilizing two orthogonal coupling feeds, the microstrip antenna produces circularly polarized radiation in the broadside direction. Meanwhile, the rotationally thin structure is driven by the coupling of the microstrip patch, and a linearly polarized radiation out of the range of ±15° is generated. Due to this parasitic structure, the radiation of the whole antenna at the upper hemisphere is balanced greatly, which leads to the wide-angle coverage ability enhancement of the low-profile antenna. A prototype operating at 2.7 GHz is fabricated and tested, demonstrating an impedance bandwidth of 15% (2.4 to 2.8 GHz). Measurement results show a 6 dB difference between the maximum and minimum gain in the upper hemisphere. With an overall antenna height of just 6 mm, all gains in the upper hemisphere exceed −3.5 dB. [ABSTRACT FROM AUTHOR]

A compact dual-band circularly polarized (CP) shared-aperture antenna is proposed for satellite communication. The antenna enables simultaneous dual-band functionality and CP radiation with right-handed CP in the Ku band and left-handed CP (LHCP) in the Ka band. The shared-aperture is implemented by integrating two independent subapertures, which function through frequency-multiplexed, resulting in a minimized profile (0.04 $ {\lambda _0} $ λ0) and reduced complexity, making it an ideal choice for array applications. To enhance inter-frequency isolation, a circular arrangement of metal vias is incorporated. The measured results indicate that the antenna effectively encompasses a 3 dB axial ratio (AR) bandwidth of 15.6–16.5 GHz in Ku and 26.5–27.5 GHz in Ka bands. Additionally, it exhibits a broader 10 dB impedance bandwidth (IBW) and superior port isolation bandwidth exceeding 30 dB. [ABSTRACT FROM AUTHOR]

Based on the shortcomings of the current ultra wide band (UWB) array antenna research and the engineering requirements, a tightly-coupled UWB array antenna is designed. The antenna uses a tightly-coupled dipole array (TCDA) as the antenna radiator and is fed by Marchand Balun with gradual impedance. It has the characteristics of dual polarization, low profile and high gain. The antenna also uses a double-layer frequency selective surface (FSS) and a cross-shaped resistive absorbing material to improve the wide-angle scanning performance, especially the self-excited oscillation caused by the short circuit zero points at high frequency. Through the simulation analysis of the antenna by HFSS, it is concluded that the array has VSWR < 3 in the range of 2-18 GHz. The VSWR is less than 3.5 in the range of 40° angle scanning on the H plane and the VSWR is less than 3.3 in the range of 85° scanning on the E plane, which has excellent E plane scanning capability. The profile of antenna array is 15mm (0.1 llow), the polarization isolation is better than - 25dB, and the gain of 20x20 antenna array exceeds 20 dB,which can be used in airborne radar, spaceborne radar and other application scenarios. [ABSTRACT FROM AUTHOR]

In this article, a low-profile, high-gain meta-surface artificial intelligence process-based broadband microstrip patch antenna for 5G wireless communications is presented. The FR4 epoxy substrate material, with a dielectric constant of 4.4 and a thickness of 1.6, is used for the antenna to operate at a 20 GHz resonating frequency. The proposed antenna is simulated using the HFSS to design a simple antenna with a low profile and proper operational characteristics. Moreover, a new type of meta surface antenna with a modified patch is elongated on the surface of the antenna. The simulation of the proposed antenna highlights that the studied antenna has a maximum reflection coefficient of − 34 dB, and a bandwidth of 17–23 GHz. The proposed results, with a low profile and antenna size of 1.33λ0 × 1.33λ0 × 0.106λ0, were measured and fabricated. The meta surface appeared in the form of a mesh type of structure, fed by a microstrip patch antenna with coaxial feed cells, revealing a good arrangement with the simulated one. Moreover, the meta surface with artificial technology has empowered the arrival of new ideas and explanations in the strategy of antennas for the control of electromagnetic waves. The measured results show that the proposed antenna has the perfect axial ratio, along with a 10 dB impedance bandwidth achieved with a valued stable gain of 9–10 dBi. [ABSTRACT FROM AUTHOR]

We demonstrate the generation of highly directive circularly polarized beams by proposing a meta-lens to calibrate the near fields over the holographic surface. Such a design possesses the merits of ultra-low profile as a lens system on the basis of phase compensation of a specific radiating aperture rather than the conventional consideration of the lens focus, and the ratio between the overall height of the antenna architecture and diameter of radiating aperture is only 0.09. Especially, the proposed meta-lens integrated holographic surface also offers a satisfactory solution to improve the overall efficiency of holographic antennas, and the experimental results verify the proposed design with 27.6 dBic measured gain and 40.4 % aperture efficiency at 15 GHz. We expect the proposed strategy of integrating phase compensation lens closely over the holographic surface, pave the way for highly efficient meta-radiators with ultra-low profile. [ABSTRACT FROM AUTHOR]

A highly selective planar microstrip filtering antenna for point-to-point communication is proposed in this paper. The bandpass filter is composed of a rectangular split-ring coupling resonator, and a portion of the filter is equivalent to a microstrip monopole antenna. Two rectangular split-ring structures with their openings aligned generate resonant characteristics, and U-shaped microstrip coupling structures are wrapped outside to optimize the passband characteristics. One of the U-shaped microstrip structures is transformed into a one-side bent structure as a radiation unit and serves as the resonant structure of the final stage of the filter, reducing the connection loss between the filter and the antenna. The operating frequency band of the filtering antenna is from 6.38 to 6.63 GHz with a reflection coefficient of less than -10 dB, a fractional bandwidth of 3.8%, and a peak gain of 4.46 dBi. The filtering antenna has excellent frequency selectivity, good out-of-band suppression, high gain, and small device size, in addition to its low cost after system integration. The simulation results are consistent with the experimental test results. The filtering antenna as a novel radio frequency sensor can be applied to the point-to-point communication of automated guided vehicles in the logistics field. [ABSTRACT FROM AUTHOR]

In this paper, a patch array antenna with wideband circular polarization and high gain is proposed by utilizing a hybrid metasurface (MS). A corner-cut slotted patch antenna was chosen as the source due to the possible generation of CP mode. The hybrid MS (HMS), consisting of a receiver MS (RMS) arranged in a 2 × 2 array of squared patches and a linear-to-circular polarization conversion (LCPC) MS surrounding it was then utilized as the superstrate driven by the source. The LCPC MS cell is a squared-corner-cut patch with a 45° oblique slot etched, which has the capability for wideband LCPC. The LCPC unit cell possesses wideband PC capabilities, as demonstrated by the surface current analysis and S-parameter simulations conducted using a Floquet–port setup. The LP EM wave radiated by the source antenna was initially received by the RMS, then converted to a CP wave as it passed through the LCPC MS, and ultimately propagated into space. To further enhance the LCPC properties, an improved HMS (IHMS) was then proposed with four cells cut at the corners, based on the original HMS design. To verify this design, both CMA and E-field were utilized to analyze the three MSs, indicating that the IHMS possessed a wideband LCPC capability compared to the other two MSs. The proposed antenna was then arranged in a 2 × 2 array with sequential rotation to further enhance its properties. As demonstrated by the measurements, the array antenna achieved an S11 bandwidth of 60.5%, a 3 dB AR bandwidth of 2.85 GHz, and a peak gain of 15.1 dBic, all while maintaining a low profile of only 0.09λ0. [ABSTRACT FROM AUTHOR]

This work presents a novel design of a low-profile broadband circularly polarized (CP) metasurface (MS) antenna based on characteristic mode analysis (CMA) technique for potential use in C-band satellite communications. The proposed antenna is composed of a 4 × 4 array of truncated patch unit cells and incorporates an enhanced slot coupling feeding structure. CMA technique is employed to analyse and modify to improved CP performance. The proposed design exhibits good radiation characteristics including measured − 10 dB impedance bandwidth of 22.72% (4.8–6.05 GHz), a 3 dB axial ratio bandwidth (ARBW) of 16.3% (5.1–5.95 GHz), and a peak gain of 8 dBi within its operational frequency range. Furthermore, the antenna's metasurface design contributes to scattering suppression over a wide frequency span (4–18 GHz), with a notable peak reduction of 9.1 dB at 8 GHz. This characteristic holds potential significance for radar cross-section (RCS) reduction. [ABSTRACT FROM AUTHOR]

In this paper, a co-aperture dual-polarized antenna array is proposed. The frequency band covers the P-band (0.4–0.7 GHz) and the X-band (9.3–9.9 GHz). The P-band array is designed in the form of an all-metal Vivaldi, while minimizing the impact of the P-band antenna array structure on the X-band electrical performance. The final profile design for the dual-band antenna structure is only 0.12 λ0 (λ0 corresponds to the wavelength of 0.4 GHz). The X-band design adopts the miniaturized waveguide slot structure, which can be well embedded in the P-band array structure. In order to verify the feasibility of the scheme, prototype processing and testing were carried out, and the test results are consistent with the simulation results. The active VSWRs of the overall design are less than 2.0. Additionally, the dual-band antenna array has favorable radiation performance in each frequency band. It can be used in forest biomass measurements and other interferometric applications. [ABSTRACT FROM AUTHOR]

Traditional radome adversely influences the antenna performance besides protecting the antenna from the outside environment. In this work, one co‐design of a millimeter‐wave antenna and radome using parasitic patches is presented, featuring a low profile and high gain. First, the basic influence of radome on patch antenna is investigated on a transparent and low‐loss material cyclic olefin copolymer. Then, the electromagnetic interaction between the patches and the antenna is investigated in detail to reduce the adverse effect of field reflection and phase delay. One prototype of the co‐designed radome and antenna was fabricated for demonstration. The measured results show that the entire profile of the co‐designed radome and antenna is significantly reduced from traditional 0.5–0.2 λg and the gain is enhanced by 2.4 dB. [ABSTRACT FROM AUTHOR]

This article presents an optimized dual-polarized transmitarray antenna (TA) designed for MIMO applications at the Ka-band, capable of switching beams in two directions. The antenna aperture uses a small unit cell with three layers of Taconic RF-35 dielectric substrates, which can be easily fabricated using PCB technology. The unit cell achieved a 360-degree phase shift and a transmission magnitude exceeding–0.4 dB at 28 GHz. We used nine dual-polarized patch antennas in a cross shape, each with a 10.5 dBi gain at 28 GHz, to switch the beams in two directions without changing the feed location. We optimized the phase distribution in the TA aperture and adjusted the feed antenna’s $F/D$ and tilt to achieve a high-gain antenna with low-gain roll-off during beam switching. The fabricated TA exhibited excellent agreement with the full-wave simulation results. It achieved ±15 degrees and ±30 degrees beam tilts in the x- and y- directions, with less than 0.8 dB gain roll-off for both polarizations.

This communication presents a wideband and a low-profile flexible wearable antenna intended to operate at a 2.45 GHz WBAN band. The suggested antenna comprises a CPW-fed monopole antenna backed by an artificial magnetic conductor (AMC) to act as a reflector. The latest AMC-integrated design uses R03003 as a dielectric substrate. The suggested design features an impedance bandwidth of 71.03% (1.87–3.93 GHz) with a gain value of 3.62 dBi and has a compact footprint of 40 × 40 mm2. The incorporation of wideband AMC with a monopole antenna leads to bandwidth enhancement and covers the 3.5 GHz WiMAX band. Simulation and experimental studies provide evidence that in the case of structural deformities and human body loading, the suggested AMC-integrated antenna is stable and shows superior efficiency relative to the traditional monopole antenna. Furthermore, numerical analysis demonstrates that the amount of radiation AMC-integrated antenna decreases tremendously in terms of specific absorption rate for various bodily attachment scenarios. Three body templates with various compositions and forms were used to study the effects of the antenna on bodily attachment. Extensive experiments on human body phantoms and bodily attachment are also conducted and the results are presented. The suggested AMC-integrated design thus confirms a promising contender for portable wearable wireless applications. [ABSTRACT FROM AUTHOR]

Summary: An ultra‐wideband dual circularly polarized (CP) slot antenna with high isolation is presented. Two L‐shaped probes are on the upper layer, both a ladder strip outside and a bent strip in the center on the bottom layer. The L‐shaped probes and the ladder strip result in four impedance resonance modes, and the bent strip moderates real and imaginary impedances to achieve an ultrawide impedance bandwidth. Furthermore, two L‐shaped strips on the ladder strip make two linear polarized Modes 1 and 2 into two CP modes at the low‐ and mid‐frequency bands. Meanwhile, the bent strip combined with the L‐shaped probes creates the third CP resonance mode at the high‐frequency band. The cutting corner and bent slots on the ladder strip change the amplitude and the phase of the electric fields Ex and Ey to realize ultra‐wideband CP radiation. In addition, the port–port isolation is enhanced because the currents are concentrated on the bent strip, and the coupling current path is cut off with the bent slot. The fabricated antenna achieves a −10‐dB impedance bandwidth of 111% (1.7–5.94 GHz), a 3‐dB axial ratio bandwidth of 101% (1.7–5.2 GHz), and a port–port isolation of better than 20 dB. Besides, our antenna obtains a high peak gain of 8.1 dBi and a lower profile of 0.004 λL, where λL is the lowest frequency wavelength of the operating bands in vacuum. These performances make the proposed design competitive for wireless communications. [ABSTRACT FROM AUTHOR]

A dual‐wideband magnetoelectric dipole antenna is proposed. The magnetoelectric dipole is fed by a hook‐shaped metal sheet. To increase the gain at the upper band, the radiation arm of the electric dipole is designed in stepped shape. To widen the impedance bandwidth of the lower band, stepped‐shaped metal walls are employed and placed along the edges of the ground plane. To further improve and stabilize the higher band gain, four parasitic umbrella‐shaped metals are utilized. By using this novel scheme, a magnetoelectric dipole antenna with dual‐wideband operation is designed. It introduces two wide bandwidths of 35.3% (0.698–1 GHz) for the lower band and 63% (1.52–2.9 GHz) for the upper band. The lower‐band gain is stabilized within 7.3 ± 0.6 dBi, while the upper‐band gain is stabilized within 9.2 ± 0.8 dBi. The antenna dimension is only 0.41λL × 0.41λL × 0.1λL (λL denotes the wavelength at 0.698 GHz in vacuum). [ABSTRACT FROM AUTHOR]

A dual-polarized broadband coupled feed dipole antenna loaded with artificial magnetic conductor (AMC) structure is proposed. The proposed AMC structure with 4x4 elements shown in this paper consists of four perfect electrical conductor (PEC) rectangular strips and a ring to reduce the profile height of the dual-polarized dipole antenna. In addition, the dual-polarization antenna adopts coupling feed microstrip to excite two pairs of bow-tie patch. The overall size of the coupling feed dipole antenna is 1.1λ0x1.1λ0x0.09λ0 at 5.5 GHz. Measured results shows that the proposed dual-polarization antenna loaded AMC exhibit a 25.2% common working bandwidth (4.75-6.12 GHz). The isolation is less than -14 dB, and the peak gain is 10.6 dBi. This dipole antenna with AMC structure has the virtues of low profile, wide band, and good radiation performance and it has the potential to be used in C-band communication. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a novel design for a high-gain, low-profile quad-feed folded transmitarray antenna (FTA) to enable a more compact system. The proposed antenna system consists of a transmitarray, a reflectarray, and four identical planar microstrip U-slot patch antennas placed on the same surface of the reflectarray with an adjacent distance greater than 1λ. To compare the effectiveness of our design, we developed three different antenna array systems with the same aperture size: a single-feed transmitarray antenna (TA) system, the proposed quad-feed FTA system, and a single-feed FTA system. Our experimental results demonstrate that employing four symmetrical feeders with an adjacent distance of 3.2λ effectively reduces the height by about 76.7 % in comparison to the height of a single-feed TA, and by 30 % when compared to the height of a single-feed FTA. We also present the design, fabrication, and testing of a prototype of the proposed quad-feed FTA operating in the Ku-band. The measured results of the prototype confirm the effectiveness of our design. [ABSTRACT FROM AUTHOR]

A low profile, vertically polarized, ultra-wideband array antenna with end-fire beams operating in an ultra-high frequency (UHF) band is developed in this paper. The array antenna consists of 1×16 log-periodic top-hat loaded monopole antenna arrays and is feasible to embed into a shallow cavity to further reduce the array height. Capacitance is introduced in the proposed antenna element to reduce profile height and the rectangular top hats are carefully designed to minimize the transverse dimension. Simulated results show that when the antenna array operates in a frequency range of 300 MHz–900 ​MHz, the end-fire radiation pattern achieves ±45° scanning range in the horizontal plane. Then prototypes of the proposed end-fire antenna element and a uniformly spaced linear array (1×2) are fabricated and validated. The end-fire antenna array should be suitable for airborne applications where low profile and conformal scanning phased antenna arrays with end-fire radiations are required. This design is attractive for airborne platform applications that are used to search, discover, identify, and scout the aerial target with vertically polarized beams.

Multichannel orbital angular momentum (OAM) generation based on metasurfaces has brought significant advancements in expanding communication capacity. However, the realization of truly integrated optics is still challenging and important aspects such as beam scanning and rapid electronic switching among OAM channels, which are crucial for broad‐area communication coverage, have received little attention until now. Herein, a novel concept for multichannel OAM vortex beams generation and switching is proposed, realized by a guided‐wave‐excited metasurface (GWEM) in conjunction with a single pole five throws (SP5T) RF switch. A holography‐based theory is developed and employed to complete the array synthesis and analysis procedure without the need for a 2π phase modulation. As a proof of concept, a prototype of the GWEM is experimentally demonstrated with high qualities, including the generation of five channels of OAM vortex beams with a scanning range of ±35° in the elevation plane, a measured OAM mode purity of up to 84.5%, and consistent maintenance of the topological charge l = 2 state from 25 to 27 GHz. The proposed strategy features cost‐effectiveness, compactness, and fast nanosecond‐scale electronic switching for multichannel OAM vortex beams, making it highly applicable in space‐limited automotive radar, imaging, and communication systems. [ABSTRACT FROM AUTHOR]

This paper proposes a broadband metasurface antenna with size‐varying patches. The metasurface radiator is fed by a microstrip line through a coupling slot on the ground. By varying two parameters of the square patches, great mode controllability can be achieved, resulting in wideband and stable gain. Furthermore, the added slotted metal square ring can effectively improve radiation gain. We designed and tested a C‐band wideband antenna consisting of 4 × $\times $ 4 novel radiator units. The measured impedance bandwidth and 2‐dB gain bandwidth are 59% (4.3–7.9 GHz) and 44.1% (4.6–7.2 GHz), respectively. The designed antenna has a low profile of 0.09 λ $\lambda $. [ABSTRACT FROM AUTHOR]

This letter presents the design principle and experimental verification of a Ku‐band wideband low‐profile dual‐circularly polarized (dual‐CP) reflectarray (RA) with independent control of left‐/right‐handed circularly polarized (LHCP/RHCP) beams. Both the dynamic phase (DP) and Berry phase (BP) compensating methods are employed in the design of the unit cell, achieving independent LHCP/RHCP phase modulation based on the single‐functional‐layer concept. A single‐layer unit cell is designed, offering a 3×3 $3\times 3$‐bit dual‐CP phase shift which facilitates the independent control of LHCP/RHCP beams. A prototype with asymmetrical dual‐CP beams is fabricated and tested. For LHCP and RHCP excitation, beam directions of (120∘,10∘ $12{0}^{\circ },1{0}^{\circ }$) and (135∘,−30∘ $13{5}^{\circ },-3{0}^{\circ }$) are realized, respectively, with sidelobe levels and cross‐polarizations both under −15 dB. The prototype exhibits a wide axial ratio (AR) bandwidth of over 36% with AR <2 $\lt 2$ dB. The overlapped 1‐dB gain and AR <2 $\lt 2$ dB bandwidth is 19.5% under LHCP input and 12.2% under RHCP input, with maximum aperture efficiency of 41.3% and 34.6%, respectively. The proposed dual‐CP RA exhibits broad band, pure chirality, high gain, low profile and independent polarization control, with single‐layer construction which is of low cost and easy processing. [ABSTRACT FROM AUTHOR]

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A low-profile Wi-Fi 6E antenna for laptop applications is proposed in this paper. The proposed antenna is electrically small covering 2.4/5/6 GHz Wi-Fi 6E frequency bands. A planar geometry is first introduced that is later conformed for achieving minimal area in the horizontal plane (x–y plane). A total size of 4 mm × 10.7 mm × 3.7 mm is obtained for conformal topology. A thin and flexible polyimide substrate of thickness 0.15 mm is used for attaining conformity. Regarding the antenna structure, it consists of a shorted and meandered monopole strip connected with a rectangular-shaped loop that is capacitively coupled by a Г-shaped driven trace. The meandered strip and the loop structure aid in the excitation of the fundamental 0.25-λ monopole mode and also 0.25-λ loop mode at 2.4/5 GHz, respectively. Moreover, the Г-shaped coupling strip produces the 0.25-λ monopole mode in the 6 GHz frequency band. The proposed antenna conforms to the Chu–Harrington limit with ka value of < 0.78 implying that the antenna is electrically small. In addition, the implementation of the antenna inside a commercial laptop is also illustrated. [ABSTRACT FROM AUTHOR]

In this letter, a wideband and low‐profile multipolarization reconfigurable antenna based on metasurface (MTS) is proposed. The antenna mainly contains two parts, an upper layer of MTS and a bottom layer of circular slot antenna. The MTS acts as a polarization controller, by mechanically rotating the MTS layer at a proper angle while keeping the circular slot antenna remain stationary, the polarization mode of the antenna can be switched to linear polarization (LP), left‐hand circular polarization (LHCP), and right‐hand circular polarization (RHCP). The experimented −10 dB impedance bandwidth of 37.8% and 54% for LP and circular polarization (CP) modes, respectively. The measured overlapped 3‐dB AR bandwidth is 22.2% for both CP modes, covering from 3.2 to 4 GHz. Moreover, the measured peak gain of the presented antenna reaches 9 dBi and 8 dBic for LP and CP modes, with a lower profile of 0.05 λ0. [ABSTRACT FROM AUTHOR]

This paper presents a low profile cylindrical cavity quadruple-mode dual-band bandpass filter. Five short-circuited metal pillars are loaded in a cylindrical cavity to change the electric field distributions of the original resonant modes. The changed TM010 mode and TM110+ mode form the first passband, and the changed TM110- mode and TM210+ mode form the second passband. The center frequencies of the two passbands are 3.05 GHz and 3.59 GHz, with relative bandwidths of 1.72% and 2.5%, respectively. The first passband can be adjusted independently, and the stopband range of the proposed bandpass filter is relatively wide. By using the degenerate modes, two transmission zeros are introduced to improve the selectivity of the proposed bandpass filter. The use of TMmn0 mode effectively reduces the height of the cavity. The fabricated cavity bandpass filter is measured, and the measured results are accordance with the simulated ones.

In this paper, a patch array antenna with wideband circular polarization and high gain is proposed by utilizing a hybrid metasurface (MS). A corner-cut slotted patch antenna was chosen as the source due to the possible generation of CP mode. The hybrid MS (HMS), consisting of a receiver MS (RMS) arranged in a 2 × 2 array of squared patches and a linear-to-circular polarization conversion (LCPC) MS surrounding it was then utilized as the superstrate driven by the source. The LCPC MS cell is a squared-corner-cut patch with a 45° oblique slot etched, which has the capability for wideband LCPC. The LCPC unit cell possesses wideband PC capabilities, as demonstrated by the surface current analysis and S-parameter simulations conducted using a Floquet–port setup. The LP EM wave radiated by the source antenna was initially received by the RMS, then converted to a CP wave as it passed through the LCPC MS, and ultimately propagated into space. To further enhance the LCPC properties, an improved HMS (IHMS) was then proposed with four cells cut at the corners, based on the original HMS design. To verify this design, both CMA and E-field were utilized to analyze the three MSs, indicating that the IHMS possessed a wideband LCPC capability compared to the other two MSs. The proposed antenna was then arranged in a 2 × 2 array with sequential rotation to further enhance its properties. As demonstrated by the measurements, the array antenna achieved an S11 bandwidth of 60.5%, a 3 dB AR bandwidth of 2.85 GHz, and a peak gain of 15.1 dBic, all while maintaining a low profile of only 0.09λ0.

A linearly polarized conformal phased array antenna with a low profile and a large scanning range is proposed, based on stacked patch antenna element fed by a coupled microstrip line. A backed compact cavity is designed in the antenna element, to reduce the mutual coupling between the elements. The prototype of the proposed conformal array, a conformal array composed of 4 × 4 elements which are axially mounted onto a cylindrical surface, is fabricated and measured, whose profile is as low as 0.072 λh (λh is the free‐space wavelength at the highest operating frequency). The experimental results demonstrate that the array achieves active VSWR below than 2.5 over the frequency band of 1.52–1.77 GHz (15%), within the wide‐scanning ranges of ±70° in the E plane and ±60° in the H plane, and the measured results are in good accordance with the calculation. [ABSTRACT FROM AUTHOR]

In this paper, a novel artificial magnetic conductor (AMC) reflector is proposed for gain stability enhancement of a low‐profile wideband bowtie antenna (operates at C‐band). Two AMC reflectors are investigated: the first one is based on a standard square patch cell while the second one is based on a novel cell geometry called modified cross shape (MCS). The two units' cell geometries are studied and optimized to achieve the desirable performances, namely; low‐profile, wide impedance bandwidth, and gain stability. The proposed antenna structure with 5 × 8 MCS unit cells is fabricated and measured. The results show a significant steady gain compared to similar work in the literature. The fabricated structure presents a low thickness of 0.084 λL (λL is the guided wavelength at the lowest frequency, i.e., 3.94 GHz) with 0.85 dB of gain variation over a wide impedance bandwidth of about 50% (3.94–6.61 GHz). [ABSTRACT FROM AUTHOR]

This paper presents a low profile cylindrical cavity quadruple-mode dual-band bandpass filter. Five short-circuited metal pillars are loaded in a cylindrical cavity to change the electric field distributions of the original resonant modes. The changed TM 010 mode and TM 110+ mode form the first passband, and the changed TM 110- mode and TM 210+ mode form the second passband. The center frequencies of the two passbands are 3.05 GHz and 3.59 GHz, with relative bandwidths of 1.72% and 2.5%, respectively. The first passband can be adjusted independently, and the stopband range of the proposed bandpass filter is relatively wide. By using the degenerate modes, two transmission zeros are introduced to improve the selectivity of the proposed bandpass filter. The use of TM mn 0 mode effectively reduces the height of the cavity. The fabricated cavity bandpass filter is measured, and the measured results are accordance with the simulated ones. [ABSTRACT FROM AUTHOR]

A low-profile high-efficiency transmitarray antenna (TA) for beamforming applications is proposed and investigated in this paper. The partial H-plane waveguide slot array antenna is employed as the compact low-profile feeding structure of the beamforming TA. The designed TA can achieve a high taper efficiency due to the multi-array sources and the compactness of the partial H-plane waveguide. Moreover, the proposed TA can inherently have a high spillover efficiency because the frequency selective surface (FSS) for beamforming is located just above the radiating slot. The FSS with a transmission phase variation of 2π is designed by a square patch array and used to manipulate the wave-front of the transmitted electromagnetic wave instead of a complicated feed network and phase shifters. To verify its beamforming characteristic, three types of FSSs to operate a forming angle of −40°, −20°, 0°, +20°, and +40° are designed at 12 GHz. The distance between the FSS and the slot array antenna is 0.1λ0, and the aperture efficiency is measured to be about 69%. The measured results, such as the reflection coefficient and the far-field radiation pattern, are in good agreement with the simulated results. From the measured results, the proposed TA is confirmed to have good beamforming characteristics and high aperture efficiency. [ABSTRACT FROM AUTHOR]

Summary: Wireless body area networks (WBAN) is used to measure patients' health conditions continuously. Different kinds of sensors are required to measure health conditions. When such types of antennas are used on the human body, they are flexible with the movements. The usage of wearable devices is currently increasing in the biomedical field. The presented wearable antenna is suitable for biomedical applications. The presented ultra‐wideband (UWB) flexible parachute shape wearable antenna is fabricated on a jeans textile substrate. The prototype antenna has a −10 dB measured impedance bandwidth of 5800 MHz (7 to 12.8 GHz) with average radiation efficiency of 75.28%. The prototype antenna's size is 40 × 40 mm2 (1.32 × 1.32 λ02 at centre frequency 9.9 GHz) and a peak gain of 4.5 dB at 12.33 GHz. The fabricated antenna is suitable for biomedical applications in X‐band frequencies and can be implemented with a low‐cost manufacturing process. The radiating element is made by conductive copper tape. Muscle‐equivalent phantoms are used to analyze the body effect on antenna performance. The radiation effect emitted by the presented antenna on the human body is calculated by the specific absorption rate (SAR) value. The maximum SAR value of the proposed antenna is 1.84 W/kg at 12.33 GHz. This leads to promising results for wearable applications related to remote health care monitoring, such as biotelemetry and mobile health with a sensor‐driven approach. [ABSTRACT FROM AUTHOR]

A high-gain low-profile reflector antenna with dual-band radiation ability is presented in this paper. The antenna achieves a relative 2 dB gain bandwidth of 10% around fl, and a relative 2 dB gain bandwidth of 20%, around fh, where fl and fh are the center operating frequencies of the frequency bands of 29.4~32.4 GHz and 142~174 GHz, respectively. To achieve the dual-band radiation ability, a composite dual-band feed with an fh/fl ratio of around 5 is proposed as the feed for the reflector antenna, which includes a higher-band circular waveguide and a lower-band coaxial horn. The metallic elliptical surface serves as the subreflector (SR) in the higher band, while the SR is the planar reflectarray in the lower band. Due to the design of the dual reflector, the dual-band reflector antenna features a low focal-to-diameter (F/D) ratio of approximately 0.2. According to the simulated results, the proposed reflector antenna achieves efficiencies of 59.0% and 42.9% at fl and fh, respectively. For verification purposes, a Ku/E-band scaled prototype is manufactured. The measured VSWRs, radiation patterns, and gains are in reasonable agreement with the simulated ones, proving the correctness of the proposed design method. [ABSTRACT FROM AUTHOR]

Microstrip antennas are high gain aerials for lowprofile wireless applications working with frequencies over 100 MHz. This paper presents a study and design of a low cost slotted-type microstrip patch antenna that can be used in 5G millimeter wave applications. This research focuses on the effect of ground slots and patch slots which, in turn, affect different antenna parameters, such as return loss, VSWR, gain, radiation pattern, and axial ratio. The working frequency range varies from 24 to 28 GHz, thus falling within 5G specifications. A subset of artificial intelligence (AI) known as particle swarm optimization (PSO) is used to approximatively solve issues involving maximization and minimization of numerical values, being highly challenging or even impossible to solve in a precise manner. Here, we have designed and analyzed a low-profile printed microstrip antenna for 5G applications using the AIbased PSO approach. The novelty of the research is mainly in the design approach, compactness of size and antenna applicability. The antenna was simulated with the use of HFSS simulation software. [ABSTRACT FROM AUTHOR]

This paper presents the design, analysis, and experimental validation of a compact $2 \times 1$ MIMO antenna operating in two bands. Band 1 is Linearly Polarized (LP) with spatial diversity operating in the sub-6 GHz band for the Fifth Generation (5G). Band 2 is Circularly Polarized (CP) for polarization and pattern diversity with an axial ratio below 3 dB for WLAN, Wi-Fi 6E, and C-band applications. The proposed single antenna consists of a Squared Shape Modified Monopole with partially Defected Ground (SMMDG) fed by Co-Planar Waveguide CPW. The partial ground has a defect on its upper left side and an I-shaped strip on the right side. The two MIMO radiators are arranged in oppositely flipped shapes. The decoupling and common partial ground structure consists of an opposite, Double T-shaped strip (DTSS) with a common strip head that performs as a band-stop filter. The overall dimensions of the MIMO antenna are $31.5\times 45 \times 1.6$ mm3. The simulated impedance bandwidth of the first band with LP lies between 3.1 and 4.7 GHz, for which $\text{S}_{{11}}$ and $\text{S}_{{22}} < -10$ dB, while the measured values are between 3.45 GHz and 4.8 GHz. The simulated impedance bandwidth for the second band for $\text{S}_{{11}}$ and $\text{S}_{{22}} < -10$ dB lies between 5.24 and 7.9 GHz, while the measured one lies between 5.65 GHz and 9 GHz. The simulated 3-dB Axial Ratio Bandwidth (ARBW) within Band 2 is (5.6–8.5) GHz, while the measured 3-dB ARBW is (5.95–8.1) GHz. The minimum simulated isolation between the two ports is 17 dB in Band 1 and 26 dB in Band 2, while the minimum measured isolation is 21 dB in Band 1 and 26 dB in Band 2. Wi-Fi 6E (n96) (5.925-7.125) GHz is covered with right-hand circular polarization (RHCP) in the positive Z direction and left-hand circular polarization (LHCP) in the negative Z direction, covering Band 2 with an axial ratio less than 3 dB. Other crucial MIMO metrics are also calculated, such as the Envelope Correlation Coefficient (ECC), Mean Effective Gain (MEG), and Diversity Gain (DG). The antenna provides excellent MIMO diversity performance, which makes it an excellent candidate for many portable wireless applications.

Microstrip antennas are high gain aerials for low-profile wireless applications working with frequencies over 100 MHz. This paper presents a study and design of a low cost slotted-type microstrip patch antenna that can be used in 5G millimeter wave applications. This research focuses on the effect of ground slots and patch slots which, in turn, affect different antenna parameters, such as return loss, VSWR, gain, radiation pattern, and axial ratio. The working frequency range varies from 24 to 28 GHz, thus falling within 5G specifications. A subset of artificial intelligence (AI) known as particle swarm optimization (PSO) is used to approximatively solve issues involving maximization and minimization of numerical values, being highly challenging or even impossible to solve in a precise manner. Here, we have designed and analyzed a low-profile printed microstrip antenna for 5G applications using the AI-based PSO approach. The novelty of the research is mainly in the design approach, compactness of size and antenna applicability. The antenna was simulated with the use of HFSS simulation software.

This paper presents a single-layer dual-polarized filtering antenna with good out-of-band suppression. By using inherent characteristic of the patch’s eigenmode and meanwhile merging four filtering strategies, i.e., parasitic patches, slot on the driving patch, and defected ground structure (DGS), a low-profile filtering antenna design with five radiation nulls has been realized. With the designed filtering antenna, a conventional 1×2 array with a spacing of 0.91λ is first developed. In order to reduce the sidelobe level of the array, a sharing patching scheme is introduced to decrease the interspace between the elements as 0.44λ, with the same physical size as the conventional array. In addition, a concept to measure total isolation between two kinds of the polarized ports in the array, i.e., SddVH, has been derived for the first time. The prototype of the proposed array is fabricated with a profile of 0.038λ. Measured results indicate that the designed novel array has an operational band of 3.53–4.06 GHz, SddVH better than 41 dB, a sidelobe level below −18 dB, and a suppression level above 20 dB with the stopband up to 0.5 GHz and 5 GHz.

In this work, a dual-band transmissive polarization conversion metasurface (PCM), with omnidirectional polarization and low profile, is proposed. The periodic unit of the PCM is composed of three metal layers separated by two substrates. The upper patch layer of the metasurface is the patch-receiving antenna, while the bottom layer is the patch-transmitting antenna. Both antennas are arranged in an orthogonal way so that the cross-polarization conversion can be realized. The equivalent circuit analysis, structure design, and experimental demonstration are conducted in detail, the polarization conversion rate (PCR) is greater than 90% within two frequency bands of 4.58–4.69 GHz and 5.33–5.41 GHz, and the PCR at two center operating frequencies of 4.64 GHz and 5.37 GHz is as high as 95%, with a thickness of only 0.062 λ L , where λ L is the free space wavelength at the lowest operating frequency. The PCM can realize a cross-polarization conversion, when the incident linearly polarized wave at an arbitrary polarization azimuth, which indicates that it has the characteristics of omnidirectional polarization. [ABSTRACT FROM AUTHOR]

A quad-band metamaterial absorber using a periodically arranged surface structure placed on an ultra-thin substrate is demonstrated in this paper. Its surface structure consists of a rectangular patch and four L-shaped structures distributed symmetrically. The surface structure is able to have strong electromagnetic interactions with incident microwaves, thereby generating four absorption peaks at different frequencies. With the aid of the near-field distributions and impedance matching analysis of the four absorption peaks, the physical mechanism of the quad-band absorption is revealed. The usage of graphene-assembled film (GAF) provides further optimization to increase the four absorption peaks and promotes the low-profile characteristic. In addition, the proposed design has good tolerance to the incident angle in vertical polarization. The proposed absorber in this paper has the potential for filtering, detection, imaging, and other communication applications. [ABSTRACT FROM AUTHOR]

Spiral antenna sensors are commonly used in partial discharge (PD) ultra-high frequency (UHF) detection in gas-insulated switchgears (GISs). However, most of the existing UHF spiral antenna sensors are based on a rigid base and balun, such as FR-4. The safe built-in installation of antenna sensors requires the complex structural transformation of GISs. To solve this problem, a low-profile spiral antenna sensor is designed based on a polyimide (PI) flexible base, and its performance is optimized by improving the clearance ratio. The simulation and measurement results show that the profile height and diameter of the designed antenna sensor is 0.3 mm and 137 mm, which is 99.7% and 25.4% smaller than the traditional spiral antenna. Under a different bending radius, the antenna sensor can maintain VSWR ≤ 5 in 650 MHz~3 GHz, and its maximum gre is up to 6.1 dB. Finally, the PD detection performance of the antenna sensor is carried out on a real 220 kV GIS. The results show that, after being built in, the PD with a weak discharge magnitude of 4.5 pC can be effectively detected by the antenna sensor, and the antenna sensor has the ability to quantify the severity of PD. In addition, through the simulation, the antenna sensor has potential for the detection of micro water in GISs. [ABSTRACT FROM AUTHOR]

A programmable metasurface antenna based on electrically tunable elements operating in 5G millimeter‐wave band, which has the features of low cost, easy manufacturing, low profile, easy integration with planar circuits, is proposed herein. The prototype consists of a 128‐element metasurface array, an 8‐channel beamforming chip as equal amplitude power divider networks, and a control network. Elements mounted with varactors to realize different states are controlled by DC bias signal from the back of a printed circuit board (PCB). By assigning different voltage values, array coding can be dynamically changed, thereby realizing beam steering. Both element dimensions and its location along substrate integrated waveguide (SIW) are optimized to better antenna performance. Experiment results show that the proposed metasurface can achieve not only the scanning range of ±70° for unidirectional beam in azimuth and ±40° in elevation but also ±50° for dual beam in azimuth. The whole prototype is fabricated based on PCB technologies, and good agreements among simulated and measured results are obtained. The proposed electrically tunable metasurface array is a good alternative to the traditional expensive phased array and has a great potential application prospect in radar and communication systems. [ABSTRACT FROM AUTHOR]

Antennas with broadband radiation and small-size are highly required in wireless communication system. The trade-off relation between bandwidth and size became a difficulty when it comes to miniaturized antenna design. A method of realizing antenna miniaturization and bandwidth enhancement at the same time is needed. Monopole antennas are the most common used one in the devices of Internet of Things, Internet of Vehicles, and wireless access points et al. In this paper, a wideband low-profile top-loaded patch monopole antenna based on surface current engineering is proposed. The topology combines a center-fed circular patch with inductive vias. The patch is designed with patterns, which consists of four concentric annular rings and some strips in radial direction. In this way, three resonances are generated, and the pattern is optimized to bring three resonances close to each other. The number of the strips is specially designed to bring three resonances close to each other. By loading the inductive vias on the outermost rings, connecting to the ground, the resonance at low frequencies can be enhanced, as a consequence of the optimized impedance matching. The field distribution is analyzed to verify the operation principle. A prototype is fabricated, and the measured results agree well with the simulated ones. The relative −10 dB bandwidth is 69% and the omnidirectional radiation pattern is stable in the operating band. The antenna achieves a rather wideband radiation while maintaining a low profile. The method of antenna miniaturization and bandwidth enhancement based on surface current engineering paves the way for antenna design in low-profile ultra-wideband applications. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the safety and effectiveness of total percutaneous implantation of the Zenith Alpha Thoracic (ZTA) endograft in the treatment of diseases of the descending thoracic aorta. Materials and Methods: A retrospective cohort study of 56 consecutive patients undergoing total percutaneous ZTA implantation between 2018 and 2020 was performed in a single center. Patients' demographics, clinical characteristics, anatomical parameters, operative details, device features, and postoperative outcomes were assessed. The primary endpoint was ongoing clinical success. A Cox regression model was used to determine the predictive factors of worse postoperative outcomes. Results: Eighty-three ZTA endografts were implanted in 35 men and 21 women with a mean age of 69±11 years for the treatment of 26 degenerative aneurysms, 15 type B dissections, and 8 penetrating ulcers, among others. Primary technical success was 100%, with a 30-day ongoing clinical success rate of 94.6%. The 1-year ongoing clinical success rate was 91.1% (51 patients), and freedoms from all-cause mortality, type 1 and 3 endoleaks, and any unplanned reintervention were, respectively, 95.3%, 91.4%, and 88.2% at 1 year. During follow-up, there was one case of surgical conversion for an aorto-esophageal fistula. On the contrary, neither aneurysmal rupture nor significant aneurysmal expansion was recorded. Repair of ruptured thoracic aorta and a high ratio of sheath outer diameter to external iliac artery diameter were found to be independently associated with worse outcomes, with adjusted odds ratios of 4.4 [1.5-15.3] and 4.9 [1.1-23.9], respectively. Conclusion: The outcomes of total percutaneous implantation of ZTA endograft show excellent primary technical success and favorable midterm ongoing clinical success. Factors associated with worse outcomes include the repair of ruptured aorta and a high sheath to access vessel ratio. [ABSTRACT FROM AUTHOR]

Inspired by the design philosophy of information metasurfaces based on the digital coding concept, a planar 4-bit reconfigurable antenna array with low profile of 0.15λ0 (where λ0 is the free-space wavelength) is presented. The array is based on a digital coding radiation element consisting of a 1-bit magnetoelectric (ME) dipole and a miniaturized reflection-type phase shifter (RTPS). The proposed 1-bit ME dipole can provide two digital states of “0” and “1” (with 0° and 180° phase responses) over a wide frequency band by individually exciting its two symmetrical feeding ports. The designed RTPS is able to realize a relative phase shift of 173°. By digitally quantizing its phase in the range of 157.5°, additional eight digital states at intervals of 22.5° are obtained. To achieve low sidelobe levels, a 1:16 power divider based on the Taylor line source method is employed to feed the array. A prototype of the proposed 4-bit antenna array has been fabricated and tested, and the experimental results are in good agreement with the simulations. Scanning beams within a ±45° range were measured with a maximum realized gain of 13.4 dBi at 12 GHz. The sidelobe and cross-polarization levels are below –14.3 and –23.0 dB, respectively. Furthermore, the beam pointing error is within 0.8°, and the 3 dB gain bandwidth of the broadside beam is 25%. Due to its outstanding performance, the array holds potential for significant applications in radar and wireless communication systems.

As a device for missile-borne system to transmit and receive electromagnetic waves, the functions of missile-borne antenna are becoming more and more abundant. The shared-aperture antenna can improve the aperture utilization rate of missile seeker and can avoid radiation interference between antennas. This paper proposes a low profile circularly polarized shared-aperture antenna for missile seeker antenna based on the theory of microstrip circular polari-zed antenna. More specifically, the sequential rotation feed technology is adopted for the rectangular microstrip antenna in the high-frequency C-band part, while the orthogonal double feed technology is adopted for the cross microstrip antenna in the low-frequency S-band part. The nested shared-aperture antenna structure is adopted to realize the design of shared aperture antenna of 63 mm×63 mm×1.574 mm. The reflection coefficient is less than -10 dB in the frequency bands of 4.87~5.13 GHz and 2.49~2.51 GHz. The relative bandwidth of high-frequency antenna is 8.1% and that of low-frequency antenna is 0.4%. The axial ratio of the two antennas in the maximum radiation direction at the center frequency is less than 3 dB. The experimental data show that the shared-aperture antenna designed and applied to the missile-borne antennacan significantly improve the aperture utilization of the missile seeker, and can also eliminate the deterioration of the radiation performances caused by the mutual coupling of antennas.

Abstract In this article a low profile asymmetrical slotted Ultra-Wide Band (UWB) antenna is proposed for Wireless Body Area Networks (WBANs) applications. The antenna was fabricated using Printed Circuit Boards (PCBs). An improved radiation pattern was obtained with an optimized patch shape of the antenna that broadens the bandwidth and lowers the antenna’s profile. The proposed antenna is simulated in HFSS and CST Simulator, and the proposed antenna is fabricated on FR4 substrate with the reduced ground plane. In frequency ranges from 2.50 to 10.97 GHz simulation as well as measured results show that the reflection coefficient (S 11) of the antenna is below − 10 dB and increased impedance bandwidth of 126%. The proposed antenna has desired radiation pattern and gain for wearable application. The wearable performance of proposed antenna on chest, leg, and the arms of the human body is analyzed with Specific Absorption Rate (SAR). The maximum value of the SAR is 0.785 W/Kg which is less than threshold value of 1.6 W/kg. The time-domain behavior of proposed antenna is investigated with the time domain parameters such as Group delay, Fidelity factor and Mean realized gain. The time domain results are evident for the proposed antenna is capable of pulse signal transmission and reception.