Ultra-low Profile Research Articles

Metal-only anisotropic impedance holographic metasurface

Abstract This paper presents a kind of metal-only anisotropic impedance holographic metasurfaces (MOAIHMs) made up of periodic wavelength size-variable meta-atoms. The proposed meta-atom has only two metal layers, i.e., a upper patterned layer carved with cylindrical hollows connecting by a narrow metal cuboid, and a lower grounded layer. The two metal layers are separated by an air gap. The anisotropy of this tensor impedance meta-atom can be skillfully realized by simultaneously controlling the radius of cylindrical hollows and the orientation angle of the narrow metal cuboid. The relationship between the geometrical parameters of the meta-atoms arranged in different positions and the impedance strips with alternating light and shade can be directly mapped based on the integration of the holographic theory and the leaky-wave principle. For proof of concept, two MOAIHMs are applied to design linearly polarized broadside pencil beam and dual linearly polarized pencil beams with different radiation angles in the C-band. There is good consistency between the measurements and the simulated results. The satisfactory performance and ultralow profile metal-only structure with reduced fabrication complexity/cost make this proposed design a competitive candidate for space applications.

Early and Mid-Term Results of Endovascular Aneurysm Repair with the Cordis Incraft Ultra-Low Profile Endograft: A High-Volume Center Experience.

Background/Objectives: In recent years, manufacturers have developed new low-profile stent grafts to allow endovascular treatment of abdominal aortic aneurysms (AAA) in patients with small access vessels. We evaluated the early and mid-term outcomes of the Incraft (Cordis Corp, Bridgewater, NJ, USA) ultra-low profile endograft implantation in a high-volume single center. Methods: Between 2014 and 2023, 133 consecutive endovascular aneurysm repair (EVAR) procedures performed using the Incraft endograft were recorded in a prospective database. Indications included infrarenal aortic aneurysms, common iliac aneurysms, and infrarenal penetrating aortic ulcers. Mid-term results were analyzed using the Kaplan-Meier method. Results: During the study period, 133 patients were treated with the Cordis Incraft endograft, in both elective and urgent settings. The Incraft graft was the first choice for patients with hostile iliac accesses, a feature characterizing at least one side in 90.2% of the patients in the study cohort. The immediate technical success rate was 78.2%. The intraoperative endoleak rate was 51.9% (20.3% type 1 A, 0.8% type 1 B, and 30.8% type 2 endoleak). Within 30 days, technical and clinical success rates were both 99.3%; all type 1A and 1B endoleaks were resolved at the 30-day follow-up CT-angiogram. After a mean follow-up of 35.4 months, the actuarial freedom from the re-intervention rate was 96.0%, 91.1%, and 84.0% at 1, 3, and 5 years, respectively. The iliac leg patency rate was 97.1%, 94.1%, and 93.1% at 1, 3, and 5 years, respectively. No statistically significant differences were observed between hostile and non-hostile access groups, nor between the groups with grade 1, grade 2, and grade 3 access hostility. Conclusions: The ultra-low profile Cordis Incraft endograft represents a valid option for the endovascular treatment of AAA in patients with hostile iliac accesses. The procedure can be performed with high rates of technical and clinical success at 30 days and the rates of iliac branch occlusion observed during the follow-up period appear acceptable in patients with poor aorto-iliac outflow.

Highly efficient meta-lens integrated holographic surface antenna

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.

Reintervention Rate after Treatment with the INCRAFT AAA Ultra–Low-Profile Stent Graft System

ObjectiveThe INCRAFT stent graft system is an ultra-low profile endograft for the exclusion of infrarenal aortic aneurysms. In the market approval studies, an increased rate of device-related complications was observed and the endograft was approved with mandated postmarketing investigations. Our aim was to analyze midterm outcomes of a real-world patient cohort treated with the INCRAFT endograft. MethodsConsecutive patients treated with the INCRAFT endograft between February 2015 and December 2022 at a single institution were included. In accordance with the Society for Vascular Surgery reporting standards, safety endpoints were reported and outcome endpoints included reinterventions, technical success, aortic-related and overall-mortality, endoleak, stent fracture, and endograft migration >5 mm. ResultsEighty patients (85% male) with a mean age of 76 ± 7 years were included. Fifty-two patients (65%) were treated within the endograft’s instruction for use (IFU). Mean aortic diameter was 59 ± 10 mm and 91% of the procedures were performed percutaneously. Mean follow-up was 37 ± 25 months and there was no aortic- or procedure-related mortality. Reinterventions occurred in 25 patients (31%) with a freedom from reintervention at 1, 3 and 5 years of 84%, 66% and 55%. The most frequent reinterventions were limb graft stenting (23%) and type II endoleak embolization (14%). Limb occlusion rate was 9% and in three patients (4%) distal endograft migrations >5 mm occurred. Persisting type II endoleaks were observed in 29% and aneurysm diameter was stable in 41% and had shrunk in 38%. Three type III endoleaks (4%) developed during follow-up and four open conversions (5%) were necessary. No known risk factors, including treatment outside IFU, were predictive for reinterventions. ConclusionTreatment of infrarenal aortic aneurysms with the INCRAFT stent graft system was safe and successful. Nevertheless, a substantial rate of reinterventions was necessary during follow-up to maintain endograft patency and prevent aneurysm growth.

Ultra-conformal epidermal antenna for multifunctional motion artifact-free sensing and point-of-care monitoring

Accurate acquisition of physiological and physical information from human tissue is essential for health monitoring, disease prevention and treatment. The existing antennas with traditional rigid or flexible substrates are susceptible to motion artifacts in wearable applications due to the miniaturization limitation and lack of proper adhesion and conformal interfaces with the skin. Recent advances in wearable radio frequency (RF) bioelectronics directly drawn on the skin are a promising solution for future skin-interfaced devices. Herein, we present a first-of-its kind epidermal antenna architecture with skin as the antenna substrate, which is ultra-low profile, ultra-conformal, ultra-compact, and simple fabrication without specialized equipment. The radiation unit and ground of antenna are drawn directly on the skin with the strong adhesion and ultra conformality. Therefore, this RF device is highly adaptable to motion. As a proof-of- feasibility, epidermal antenna can be freely drawn on demand at different locations on the skin for the development of temperature sensor, skin hydration sensor, strain sensor, glucose sensor and other devices. An epidermal antenna-based temperature sensor can offer accurate and real-time monitoring of human body temperature changes in the ultra-wideband (UWB) range. The results during the monitoring of hydration level with and without stretching show that the epidermal antenna drawn on the skin is motion artifact-free. We also designed an epidermal antenna array employing a horseshoe-shaped configuration for the precise identification of various gestures. In addition, the non-invasive blood glucose level (BGL) monitoring results during the in-vivo experiments report high correlation between the epidermal antenna responses and BGLs, without any time hysteresis. After the prediction of BGL by BP network, all the predicted BGL values are fallen 100% into the clinically acceptable zones. Together, these results show that epidermal antenna offers a promising new approach for biosensing platform.

Ultrathin Antenna-in-Package Based on TMV-Embedded FOWLP for 5G mm-Wave Applications

In this paper, a novel through mold via (TMV)-embedded fan-out wafer-level package (FOWLP) technology was demonstrated to manufacture the well-designed Antenna in Package (AiP) with ultrathin thickness (0.04 λ0). Double-sided redistribution layers (RDLs) were employed to build the patch antenna, while a TMV interposer was used to connect the front and back RDLs. By optimizing the AiP’s parameters, the patch antenna can achieve a wide impedance bandwidth of 17.8% from 24.2 to 28.5 GHz, which can cover the 5G frequency bands. Compared with previous works, the proposed AiP has significant benefits in terms of its ultralow profile, easy processing, and high gain. Hence, the TMV-embedded FOWLP should be a promising technology for fifth generation (5G) millimeter wave (mm-Wave) applications.

Dual-Polarized Phased Array With Ultralow Profile for Wide-Angle Scanning Application

Dual-Polarized Phased Array With Ultralow Profile for Wide-Angle Scanning Application

Graphene-based ultralow-profile microwave Fresnel lens

The development of ultrathin Fresnel lenses has revolutionized the lens technology and provided great prospects for the miniaturization of electromagnetic systems. Despite considerable advances in microtechnology, a scalable fabrication strategy to achieve ultralow profile microwave lenses is yet to be developed. Here, we report on a novel strategy to create ultrathin and essentially flat Fresnel lenses using graphene rings. We show that monolayer or multilayer graphene can be microstructured into a Fresnel lens to utilize the unique transmission properties of graphene. We design different Fresnel lenses and investigate their performance in the microwave regime both numerically and experimentally. It is shown that one can change the intensity of the focused wave without shifting the focusing point by altering the number of the graphene layers. The good agreement between our experimental results and the results of numerical simulations demonstrates the feasibility of atom-thick (about 10−7 of the operating wavelength) graphene-based lenses and shows their potential for ultra-compact integration.

An ultra-low profile reconfigurable multi-beam antenna based on impedance modulated metasurface

ABSTRACT A new ultra-low profile reconfigurable multi-beam antenna is proposed. It is based on impedance modulated metasurface fed with a one-divide-four electronically controllable feed network. By properly arranging the feed network, six beams at different azimuth planes are formed by controlling four diodes. The gain is enhanced through loading a cross metal strip in the middle of metasurface. The results indicate that the realized antenna has dimensions of 126 mm × 126 mm × 4 mm (equal to 2.1λ0 ×2.1λ0 ×0.067λ0, λ0, wavelength at 5 GHz). Its −10-dB bandwidth is larger than 30.0% (4.28 GHz − 5.79 GHz) when diodes I-V are turned on successively. And it can radiate beams pointing to (0°, 33°), (20°, 44°), (150°, 36°), (180°, 35°). Furthermore, the beams can be steered to (0°, 43°) and (180°, 43°) in case that diodes I&II or III&IV are switched on simultaneously.

Early Results of Elective Endovascular Repair of Infrarenal Abdominal Aortic Aneurysms With the MinosTM Stent-Graft System.

A variety of last-generation endografts are currently available for standard endovascular repair (EVAR) of infrarenal abdominal aortic aneurysms (AAAs). The purpose of this study is to report the preliminary clinical outcomes of the Minos trimodular stent-graft system, which was recently introduced to the European market. Between February 2020 and 2022, we treated 41 consecutive AAA patients (mean age 72.2±8.5, 37 males) with elective standard EVAR using the Minos. The mean maximum diameter of AAAs was 54.7±6.6 mm, the mean proximal neck's (PN) diameter was 24.8±2.7 mm, while the relevant length and angulation were 16.0 mm and 21.7°, respectively. Overall, 22 (53.6%) patients presented with shorter and angulated PN, according to the stent-graft's instructions of use, and in 6 (14.6%) patients the PN angulation >60° was combined with concomitant iliac angulation >60°. Eleven (26.8%) EVARs were performed with concomitant enormous iliac artery narrowing and tortuosity. Finally, in 19 (46.3%) AAAs, the distal iliac landing zone was aneurysmatic and they were treated with the bell-bottom technique in 17 patients and with limb extension to the external iliac artery in two cases. We evaluated technical and clinical success of the index procedures, which was based on the combination of five factors: freedom from EVAR-related mortality, from graft-related endoleak of any type, from migration at any part of graft as well the absence of notable increase AAA's sac maximum diameter and the patency of bifurcated stent-graft and of access vessels. Primary technical and clinical success of index procedures was 100%. During a median 12-month radiological follow-up the clinical success remained 100%. No type I or III endoleak, stent-graft migration, EVAR-related death, AAA rupture, or graft-related adverse events or reinterventions were documented. Four (9.8%) type II endoleaks were detected with stable AAA sac diameter. The overall incidence of sac regression was 34.1% (n=14). The preliminary results of our series showed that Minos provided excellent feasibility and safety features even through angulated and tortuous iliac vessels and in short and angulated PNs. The overall clinical success at 1 year suggests that performance of Minos follows very high standards. Further validation of these promising results with long-term data is acquired to complete the evaluation of this recently introduced stent-graft system. The current study explored the clinical performance of a new in market ultra-low profile bifurcated abdominal aortic stent-graft, the MINOS. The early and 12-month results of study suggest that implantation of this stent-graft in standard EVAR, even in hostile proximal aortic neck and iliac vessels conditions, follows very high clinical standards and encourage the further clinical use of MINOS.

Dual-Band Circular-Polarized Microstrip Antenna for Ultrawideband Positioning in Smartphones With Flexible Liquid Crystal Polymer Process

This article proposes a dual-band circular-polarized (DBCP) microstrip antenna using flexible liquid crystal polymer (LCP) manufacturing process for ON-smartphone ultrawideband (UWB) positioning application. To achieve dual-band circular polarization in a low profile, the proposed antenna is designed with a cross-slot-loaded patch with four L-shaped feeding probes and a sequential phase feeding network. A circle of capacitive via fence is loaded surrounding the patch for area miniaturization, which is adaptive for the limited space of flexible printed circuit (FPC) in smartphones. Based on the UWB positioning protocol, a three-element antenna array is constructed in a low profile of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.015\lambda _{0}$ </tex-math></inline-formula> with required isolation of 17 dB. Experimental results show the overlapped bandwidth of the efficiency and the axial ratio (AR) covering the demand bands of 6.30–6.80 and 7.75–8.10 GHz. With the properties of dual wideband operation, circular polarization, and ultralow profile, the proposed antenna exhibits feasible solutions for the UWB positioning application in space-limited smartphones.

Millimeter-Wave Patch Antennas With Ultralow Profile of 20 μm on Flexible Substrate

In applications of flexible communication electronics, the requirement for ultralow profile of antenna is gradually approaching a limit. In order to achieve a higher flexibility, it is necessitated to limit the vertical distance to 10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> scale between the integrated antennas and the electrode ground (GND). Such a small Section height results in a severely reduced radiation efficiency and a narrowed bandwidth. In this article, the enhancement of radiation efficiency and bandwidth of a millimeter-wave (mmWave) patch antenna with 20 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> profile height are studied. On the metal GND, by properly opening two (or one) resonant slots with a width of 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> , strong resonance coupling between the patch antenna and the slots can be induced, leading to a greatly enhanced radiation efficiency. Meanwhile, the spectra width of TM10 mode of the patch antenna can also be effectively broadened by the mode coupling, giving rise to a greatly improved radiation bandwidth. The physical mechanism and the sensitive factors to maximize bandwidth, antenna gain, and front-to-back ratio are discussed.

Preparation of an ultra-low profile and high peel strength copper foil with rice-grain microstructures

Rice-grain copper nanoparticles of 420 nm diameter was obtained after micro-coarsening treatment, resulting in a 52% increase in copper foil surface area and a 10-fold increase in peel strength.

Novel Planar Ultra-Wideband Modular Antenna Array with Low Profile

A planar ultra-wideband modular antenna array with an ultra-low profile based on a tight coupling effect is proposed. The antenna array is composed of multi-layer printed circuit boards. Since its frequency operation can extend up to the grading lobe frequency, the number of T/R components for the antenna aperture is reduced to the greatest extent. Specifically, a horizontal “fin” structure is added on the parallel feeding lines, which assists in improving the impedance matching of the array. In order to break the bandwidth limitation of the low-frequency loop mode, a capacitive short-circuit probe is introduced to push the common-mode resonance point into the low-frequency band. Finally, subject to Active VSWR &lt; 3, the array can realize E-plane, H-plane, and D-plane ± 45° beam scan coverage across the 6:1 frequency band (3.48–20.97 GHz). A 128-element prototype was processed and tested to validate the design. This array not only has the advantages of low profile, modularity, easy assembly, and maintenance but also minimizes the number of T/R components and reduces the cost of phased array antennas.

UHF RFID reader antenna with switchable far‐field and near‐field working state

An ultra-low profile and high-performance UHF RFID reader antenna is proposed in this letter, which can be switched between far-field (FF) and near-field (NF) operative modes. This antenna is composed of four dipoles and a reconfigurable feed network. The four dipoles form a square, and the feed network is located in the centre. The feed network is a four-way power divider, and the phase of the output signal can be controlled by switching diodes. As a balanced structure, double-sided parallel-strip lines (DSPSLs) are used to feed four dipoles. Compared to the balun structure, the application of DSPSLs can reduce the area of the feed network, thereby reducing the influence of the feed network on the central magnetic field. Experimental results show that the proposed antenna can provide a NF reading area of 180 × 180 mm2, and the identification rate can reach 100% within 30–60 mm height. The FF gain of the antenna is 4.7 dBic, and the overlapping range of 3 dB AR bandwidth and −10 dB impedance bandwidth is 800–960 MHz. The good FF and NF performance of this antenna is conducive to its application in RFID systems.

Low-profile and wide-band RCS-reduction antenna array based on the metasurface polarization converter.

Antenna elements with a low profile and high front-to-back (FB) ratio mean that no additional reflective cavity is required when forming the array, which greatly helps to simplify and lighten the entire array system. In this paper, we enhance the FB ratio of the antenna to 35 dB while maintaining an ultra-low profile of 0.05 λ0 by attaching the broadband polarization conversion metasurfaces (PCMs) as the parasitic patches to the surface of the radiating patch. Meanwhile, the array formed by the proposed antenna is arranged in a checkerboard form, which makes it have a lower radar cross section (RCS) in the X- and Ku- bands. Even with PCMs loaded, the antenna element maintains a small size of 0.58 λ0 × 0.58 λ0, which ensures the proposed array can achieve the ± 45° beam scanning, making it suitable for the phased array. For verification, we propose a low-sidelobe array composed of the proposed antenna elements, which exhibits a low profile, high FB ratio, and broadband RCS reduction through simulation and measurement.

Pin‐loaded ultrathin magnetoelectric dipole antenna with unidirectional radiation

AbstractA wide‐beam magnetoelectric dipole antenna with an ultralow profile of 0.01λ0 is proposed in this letter. The magnetic dipole (M‐dipole) is formed by placing a turnstile‐shaped patch above a circular ground, establishing the foundation of a thin profile. Then, a pair of crossed strips with one end shorted is introduced, exciting the electric‐dipole without affecting the radiation of M‐dipole and increasing the antenna profile. In that way, stable wide‐beam unilateral radiation in both the E‐ and H‐planes can be achieved. At the same time, a high front‐to‐back (F/B) ratio of 22 dB is obtained for the measured result. Besides, by adjusting the number and position of shorting pins, the proposed antenna shows beam steering capability, which makes it quite promising for future scanning applications.

Early Experience with Ovation Alto Stent-Graft

Alto is the latest generation of the Ovation stent-graft platform for endovascular aneurysm repair (EVAR). Its ultra-low profile and its proximal sealing zone close to the lowest renal artery (≥7mm) increase standard EVAR eligibility. We report early clinical and technical outcomes with the Alto stent-graft in our University Hospital Center after CE Mark approval in August2020. Seven patients (all male, mean age 76.1±6.2years) underwent EVAR with Ovation Alto stent-graft between June 2021 and February 2022. All the EVAR procedures were performed by a team of vascular surgeons experienced on EVAR with previous generation of Ovation platform. Follow-up consisted of duplex ultrasound examination at 1, 3, and 6months and of a 1-month control computed tomography angiography (CTA). Patients treated gave consent to participate in this case series and publication. A descriptive analysis of variables was performed. SPSS (version 25) and Excel were used for statistical analysis. Most of the patients had a fusiform abdominal aortic aneurysm (n=5; 71.4%). The median maximal transversal aortic diameter was 5.06cm (range, 3.98-6.99). Because of hostile aortic neck anatomy, on-label EVAR was considered feasible only with Ovation Alto stent-graft. Narrow iliac arteries (<6mm) were also present in 2 cases. All procedures were performed according to the instruction for the use of the device. Technical success was achieved in all cases. No type IA/IB/III endoleak occurred at completion angiography. No distal migration (>10mm) but 2 distal displacements (≥2mm) were observed at control CTA. During follow-up, duplex ultrasound and CTA showed no type I/III endoleak, no stent-graft migration (>10mm), and no proximal aortic neck variations (P=not statistically significant). Three patients (42.8%) are under strict surveillance because of low-flow type II endoleak not associated with sac variations. Our early experience shows promising technical and clinical success with Alto stent-graft. The proximal relocation of the proximal sealing rings and the ultra-low profile delivery system allow on-label EVAR in a wider range of aortic anatomies. Notwithstanding, further studies, meta-analysis, and prospective registries are mandatory to evaluate mid- and long-term efficacy and safety of this latest Ovation platform.

Study of limiting radial vehicle tire deformations

The purpose of this work is to determine the values of limiting radial deformations of modern car tires. The geometric and load parameters of more than 400 "Continental tires" of regular, low and ultra-low profiles were analyzed. It has been established that the relative tires deformations in relation to the profile height are not related to their dimensions and load capacity. It is shown that the relative tires deformations in relation to the free radius are linearly related to their dimensions and load capacity. Deformation limits have been obtained for both conventional tires and low and ultra-low profile tires. Keywords: vehicle tire, motion modeling, relative radial deformations, limit values

On the Design of Ultralow-Profile Broadband Absorber Based on Non-Foster Circuit

In this letter, a novel and effective method for non-Foster active absorber with ultralow profile and wide absorption band is proposed. The three-layer absorber consists of a square loop frequency selective surface array printed on the FR-4 dielectric substrate, a non-Foster matching layer, and a backed metal plane.Equivalent circuit model for the active absorber is proposed and analyzed, providing great insight into the effect of non-Foster matching layer on breaking the Rozanov limit effectively. A 1×10 absorber absorbing structure sample is fabricated.It is shown by measurement that the absorber has a fractional bandwidth of 36.0%, with a total thickness of only 0.008 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ_L</i> (wavelength at the lowest absorption frequency). The simulation and experimental results are in good agreement in the operating band, which verifies the accuracy of the design method.