Wide Dual-Band Circularly Polarized Diecletric Resonator: Innovative Integration of a Single Hybrid Feed and Thin Grounded Metasurface.

This article presents an application of a grounded substrate-based metasurface for hosting dielectric resonators (DRs), enabling a wide dual-band circularly polarized (CP) operation. The antenna structure comprises centrally positioned rectangular DRs, one above the other, along with a 7 × 7 square-slotted metasurface. The metasurface and DRs are hosted above a grounded substrate, which is fed through a single coaxial feed placed at a specific angle, employing a modified upper probe of the coaxial feed. The proposed hybrid technique utilizes the combined benefits of the feed angle and a well-matched metasurface, resulting in performance improvement. Notably, a measured impedance bandwidth of 88.1% for |S11| is achieved within the frequency range of 4.0 GHz to 10.3 GHz. Furthermore, the antenna design exhibits two overlapping measured 3-dB axial ratio (AR) bandwidths: 23.62% from 4.25 GHz to 5.4 GHz and 5.12% from 7.6 GHz to 8 GHz. The peak gain of the antenna is measured at 8.4 dBic. Consequently, this innovative single-feed antenna design, characterized by its compact profile, holds significant potential for realizing multi-band operations. Furthermore, the developed antenna is well-suited for deployment in indoor radio links and INSAT applications.

Relative Permittivity Measurement of Microliter Volume Liquid Samples through Microwave Filters.

This paper proposes a concept of dielectric characterization of low-volume liquid samples using the coupling coefficient of filters. The concept is validated through a two-pole substrate integrated waveguide filter in which the liquid under test is mounted on the coupling section between the two resonators. Unlike the conventional resonator perturbation method reported many times in the literature, this technique uses the coupling coefficient for sensing. The liquid sample is collected in a capillary tube and carefully positioned on the coupling section of the filter; the coupling coefficient of the two resonators varies compared to the relative permittivity of the sample; thus, an empirical model is established. The proposed sensor has been tested to compute the permittivity of different alcohols. Binary solutions of ethanol and water have also been characterized to calculate the volume ratio and relative permittivity as a proof-of-concept. The obtained results show that the proposed sensing technique is capable of characterizing a low quantity of liquids (≈44 µL) with good accuracy, and a worst case measured error of only 6.8% is noted. The ease of integration with other circuitry, low cost, reusability with no deterioration, and adaptability of the proposed sensor makes it a suitable choice for the chemical as well as for the pharmaceutical industry.

Evaluation of Double-Faced Tubularized Preputial Flap versus Duckett's Procedure for Repair of Penoscrotal Hypospadias with Significant Penile Curvature: A Comparative Study.

Background: Proximal hypospadias, with significant curvature, is one of the most challenging anomalies. Great diversity and a large number of procedures described over the last 4 decades confirmed the fact that no single procedure has been universally accepted or successful. So, the aim of this study is to evaluate double-faced tubularized preputial flap (DFPF) versus transverse tubularized inner preputial flap (Duckett's procedure) as regards surgical outcomes, complications rate, and cosmetic results for repair of penoscrotal hypospadias with chordee. Patients and Methods. This was a prospective comparative study on 144 children with primary penoscrotal hypospadias with moderate or severe chordee, conducted at New Damietta and Assuit hospitals, Al-Azhar University, from March 2016 to March 2022. The patients were randomly divided into two equal groups; group A (n = 72) underwent DFPF, and group B (n = 72) underwent Duckett's procedure. Results: No significant difference was identified as regards demographic data. The follow-up period ranged from 20 to 66 months (mean of 28 months after DFPF and 31 months after Duckett's repair), and the complication rate was 20.1% (29 of 144 children). There were statistically significant differences between the two groups as regards the urethral stricture, penile rotation, and total complication rate. HOSE score was adopted for assessment of surgical outcomes, urine stream, and cosmetic results. Conclusions: The DFPF technique is feasible and reliable for one-stage repair of penoscrotal hypospadias with chordee and can be considered as a good option as it ensures better surgical and cosmetic outcomes with lower incidence of complications.

Compact Four-Port Circularly Polarized MIMO X-Band DRA.

A circularly polarized (CP) multi-input multioutput (MIMO) dielectric resonator (DR) antenna (DRA) with compact size and four ports is implemented. CP radiation was achieved using the deformed DR geometry excited with aperture coupled feeding. A CPDRA with a single and two ports is investigated. The defected ground structure (DGS) was incorporated into the antenna for improving the isolation between the ports. The DGS was incorporated in such a way that the required phase difference between the generated orthogonal degenerate modes is preserved. This concept could be utilized in implementing a compact four-port CP antenna. The MIMO antenna provides a 10 dB impedance bandwidth of 38% (8.5-12.5 GHz) and a 3 dB AR bandwidth of 9.32% (9.2-10.1 GHz). The gain of the implemented antenna was around 6 dBi in the band where CP radiation was achieved. The MIMO performance parameters were calculated, and their values remained within the acceptable limits. The implemented antenna could suitably be used in X-band applications.

Miniaturized Wideband Antenna Prototype Operating over the Ku-Band.

A wideband antenna is proposed based on three-dimensional printing technology. The antenna was designed using the PREPERM 10 material, with permittivity ϵr = 10, where the overall height of the proposed prototype was maintained as 12.83 mm (0.51λ), having a lateral dimension of 60 mm × 60 mm, at an operating frequency of 12 GHz (λ = 25 mm). The proposed antenna achieved a wide frequency bandwidth with a voltage standing-wave ratio (VSWR) of less than two, from 10 GHz to 15 GHz in the Ku-band, where the maximum directivity was 20 dBi over a reflection coefficient bandwidth of 50%. It showed a miniaturized non-uniform metasurface of 2.4λ × 2.4λ × 0.51λ that was placed at 16.5 mm (0.66λ) above the ground plane, which was 2.4λ × 2.4λ × 0.04λ in dimension. Thus, the overall height of the proposed antenna system from the feed source was 29.33 mm (1.17λ). The total weight of the system including the designed structures made of PREPERM 10 and ABS with copper-painted prototypes was 96 g and 79 g, respectively. The measured results were consistent with the simulated results, demonstrating the feasibility and effectiveness of the proposed method.

Tailoring polarization states of multiple beams that carry different topological charges of orbital angular momentums.

In the past few years, orbital angular momentum (OAM) has aroused great interest in the scientific communities, because it shows great potential for enhancing capacities of radio and optical communication systems. Here, we propose anisotropic metasurfaces to generate multiple OAM vortex beams at microwave frequencies. A phase compensation theory is presented, in order to determine the phase distributions on metasurfaces, This theory enables independent control of beam numbers, polarizations, orientations, and topological charges of OAM vortex beams, respectively. The metasurface is composed of anisotropic elements, whose reflection phases can be engineered separately in different polarization directions. The scheme is validated by both simulation and experimental results and shows great potential for the polarization division multiplexing in OAM communication systems.