8 March 2022

Recognizing the role of women and girls in science, not only as beneficiaries, but also as agents of change, the 2022 UN theme for International Women's Day is "Gender equality today for a sustainable tomorrow". As highlighted in the UNESCO Science Report for 2021, women remain a minority in cutting-edge Industry 4.0 fields despite constant efforts for the recognition of women’s contributions in research and innovation and the elimination of stereotypes. Also, their work is underrepresented in high-profile journals. Data from the Antennas and Propagation (AP) Society reveal similar patterns; only 10.2% of the members are women. Female representation drops from 29.7% amongst student members to only 9.7% among professional members. Even though women are still outnumbered by men in science and technology, their achievements are equally significant and pioneering. In order to find sustainable solutions in the near future, given also the expected shortage of STEM skills, the inclusion of more women is the only option.

In this milieu, with the view to celebrate that more and more women are leading the way in engineering sciences and within the Antennas and Propagation field, in particular, we have curated a special collection of 27 articles, published in OJAP in 2021, in order to spotlight excellent contributions by female researchers. These articles span the entire range from antennas, arrays, and computational electromagnetics to emerging applications and inverse scattering.

Seven feature articles are highlighted in the collection to showcase novel AP research directed and/or performed by women engineers around the world. Fatma Elhouni et al., in their article “Liquid Antennas: Past, Present and Future”, provide a comprehensive review of liquid antennas, discussing state-of-the-art designs and current technical challenges, and suggesting the ways forward for the future. Chun-Mei Liu et al.’s article “Wideband Via-Loaded Cylindrical Open-Ended SIW Cavity Antenna” focuses on wideband and high-gain antennas with planar structures which are preferred in modern highly-integrated wireless systems, and presents an improved-gain wideband antenna with an acceptable dimension. In their article “Frequency-Dependent Feeding Methods for Broadband Vivaldi Arrays with Minimum Half-Power Beamwidth (HPBW) Variation”, Dimitra Psychogiou et al. propose new types of RF filter-based beamformers that enable the realization of ultra-broad antenna arrays with frequency-invariant HPBW. The introduced concept paves the way to high-performing spectrum sensing and antenna characterization systems with higher accuracy and small physical size. The article “Wideband Printed Half Bow-Tie Antenna Array Based on a Quad-Mode Reconfigurable Feeding Network for UAV Communications” by Ye-Yeong Jeong and Wang-Sang Lee presents an array with a wide beam coverage and a wide bandwidth as well as a miniaturized size, high gain, and a low-profile symmetrical structure.

Kazuko Fuchi et al.’s article “Design Optimization of Origami-Tunable Frequency Selective Surfaces (FSS)” reveals the power of folding with a systematic approach to designing origami for electromagnetic functionality, incorporating both structural and electromagnetic responses of the folded FSS in a coupled analysis. Martina Teresa Bevacqua and Tommaso Isernia discuss different smart rewritings of basic equations such to counteract the non-linearity of the problem and contribute to the development of reliable and effective algorithms to retrieve target EM properties in “Quantitative Non-Linear Inverse Scattering: A Wealth of Possibilities Through Smart Rewritings of the Basic Equations”. The article “Profile Inversion and Closed Form Formulation of Compact GRIN Lenses” by Francesca Maggiorelli et al. opens the possibility to realize a new type of all-dielectric Gaussian horn as an alternative to traditional metallic horns. By using the 3D printing technology, the proposed design achieves reduced size, weight, and cost while maintaining good antenna performance.

The Guest Editors would like to express their gratitude to all of the authors for providing the material for this special article collection dedicated to women’s contribution to OJAP with the wish that such actions encourage more female scientists to work in this very challenging research field.

Most Downloaded Article

A Review of Liquid Antennas: Past, Present, and Future | Fatma Elhouni et al.

The article presents a comprehensive review on liquid antennas, covering both metallic and non-metallic liquid antennas. A detailed discussion on state-of-the-art designs and current technical challenges is performed, and the ways forward for the future are suggested. As a special feature, an in-depth review of materials for liquid antennas is also provided. The challenges of liquid antennas for real-world applications are identified and discussed.

Feature Articles

Broadband Vivaldi Arrays with Minimum Beamwidth Variation | Dimitra Psychogiou et al.

The article proposes the design of frequency-dependent feed networks for linear antenna arrays with minimum half-power beamwidth variation in more than one octave of the frequency spectrum. The operating principles and design trade-offs of the concept are presented through ideal simulations of four- and six-element antenna arrays shaped by isotropic or directive radiators. It is shown that the operational bandwidth of the array can be increased by incorporating directive antenna elements and by spacing them non-uniformly.

Compact Wideband Improved-Gain Antenna for 5G | Chun-Mei Liu et al.

The article proposes a composite cavity-based antenna, based on the utilization of the via holes processing and multi-layer technique and the involvement of multiple modes towards achieving a wide bandwidth. The simple structure and the integration with other planar front-end circuits constitute benefits of the fabrication. Moreover, the transverse dimension is compact, which shows a great potential for the realization of future integrated systems.

Novel Antenna Based on a Feeding Network for UAV Communications | Ye-yeong Jeong et al.

The article presents a wideband printed half bow-tie antenna array based on a quad-mode reconfigurable feeding network for unmanned aerial vehicle communications (UAV). The proposed array has a wide beam coverage and a wide bandwidth as well as a miniaturized size, a high gain, and a low-profile symmetrical structure for ease of installation and aerodynamic drag reduction in UAV.

An Origami Designer that Sees EM Fields | Kazuko W. Fuchi et al.

The article introduces topology optimization formulations that identify origami fold-driven frequency selective surface (FSS) designs, possessing electromagnetic filtering properties at target frequencies. Both gradient-based and genetic algorithm methods are used to find optimal origami crease patterns and folded configurations. The proposed methods, and qualitative characterization of the EM origami design landscape, are applicable for RF devices other than FSSs and can also be adapted and expanded to include additional multiphysics applications.

Smart Rewritings of Equations for Quantitative Non-Linear Inverse Scattering | Martina Teresa Bevacqua et al.

The article reviews and describes under a common rationale various approaches which have been introduced for counteracting non-linearity in inverse scattering. Focus is placed on three rewritings of the Lippman Schwinger basic equation, which are compared and tested against different numerical examples, towards reducing the degree of non-linearity of the inverse scattering problem.

GRaded INdex Horn Antenna Optimized for 3D Printing | Francesca Maggiorelli et al.

The article presents new formulas for the design of cylindrical Graded-Index lens-antennas with integrated feeder. The possibility of integrating the feeder within the lens makes the system more compact and alleviates issues relates to complex mechanical design and alignment errors. The proposed formulation is successfully validated by using ray-tracing and full-wave simulations.

Discover the whole collection here.