Introduction to the Summer 2022 Issue

Welcome to our July 2022 issue of IEEE Journal of Microwaves. This month we are back to our regular plus invited manuscript queue (our last issue contained only unsolicited papers). We are especially excited this month to bring you one of our special Microwave Pioneer series pieces highlighting the career and contributions of our current IEEE President, K. J. Ray Liu, with an emphasis on microwave time-reversal focusing and tracking. This is accompanied by three invited papers covering topics on microwave applications for high-Tc superconducting devices and circuits, oscillators with non-linear gain, and beamforming with metasurfaces. Our remaining regular manuscript contributions continue to provide broad outreach and significant advances in several areas. Of particular note are articles on high-gain beamforming with a scanning lens array, a MIMO radar formed from a sparse array, a holographic RFID SDMA system, several unusual filter papers, and a detailed analysis of an animal chamber for RF exposure studies. Our monthly submission and download count has remained steady and continues to bode well for our ultimate inclusion in non-IEEE databases. As of May 2022, we have received over 340 manuscripts and have an enviable usage per published article rate of 1023, putting us third out of over 272 established IEEE publications for this statistic! We are also anticipating a large pool of popular articles for our 70th Anniversary of the MTT Society special issue, which comes out in January 2023. In July, we will be introducing a special “Author Portal” that should significantly improve our author submission experience. Please continue to enjoy our new publication and consider submitting your latest research!


I. INTRODUCTION
In this, our third issue in Volume 2 of IEEE JOURNAL OF MICROWAVES we bring you 14 new manuscripts that are a combination of both Invited and Regular contributions. We are very pleased to report that our usage count per article published 1 is keeping us high up on the IEEE ranking for this statistic which, as of the beginning of May, sat at 1,065. This is down a bit from our 2021 total of 1,348, which placed us third out of 272 IEEE technical publications based on this statistic [1]. Our usage count is now above 160,000, and for the first time our May 2022 total exceeds that of our prior 1 Usage count is the number of times an individual article is either accessed directly online or downloaded to a user through IEEE Xplore. This usage count is recorded in the separate Publishing Operations Production Portal (POPP) Analytics database and updated at the start of each calendar month.
year count for the same month -by more than 2000. We are extremely pleased to see how popular our authors are becoming!
In looking for additional metrics to help us quantify our performance as a new journal, we tried to gauge the satisfaction of our current author pool through a recidivism rate. If we count all the papers submitted to us so far (181 in late March, when I compiled the statistic), and add up the number of authors and co-authors listed on these manuscripts, there are 809 names (an average of 4.5 authors per paper, in case you are interested). Of these, however, there are only 642 unique authors. 110 author names appear more than once (i.e. they are listed on more than one paper). These 110 repeat author names appear a total of 276 times (26 authors appear on three or more papers). This leads me to conclude that our recidivism rate (number of repeat authors out of all our listed This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/ authors 2 ) is 276/809 or a remarkable 34%! Given our status as a brand-new journal with only 15 months of published content, this is a very respectable percentage and implies that we must be doing something right to have so many authors send us additional manuscripts. To better track such statistics we added a "Have you or one of your co-authors submitted to IEEE JOURNAL OF MICROWAVES before," question on our manuscript submission sequence.
On the topic of author satisfaction, in early-July we are introducing a new "Author Portal" that we hope will significantly improve the paper submission experience. For those authors who are already in the process of having a paper reviewed, please continue to use the old system. For new papers (submitted after July 4 th ), submitting authors please go to: https://ieee.atyponrex.com/journal/ieee-jmw for your manuscript upload and review sequence process. The new Author Portal will track and automatically insert many of your repeated input fields, keep better statistics, and hopefully make it much easier and quicker to insert keywords, abstract text, upload reviewer or editor-specific files, and check on paper status. We will be working with authors to update and improve the input experience as we move forward.
And moving forward: Our October issue already has a large number of interesting submissions spanning the MHz to THz frequency range and we now have more than 25 committed papers for our 70 th Anniversary of the MTT-S special issue [2]. However, we are still seeking both original research articles on topics of notable and widespread interest, as well as overview and historic features on both the events and the individuals that have shaped our society and the microwave field in general. If you are interested in contributing an article, please contact our special issue Guest Editor, Professor Ke Wu or our Editor-in-Chief. The due date for initial manuscripts is October 3, 2022. You can check the status of the special issue as well as the current list of committed authors at: https://mtt.org/ publications/journal-of-microwaves/70th-anniversary-issue/.
Again, we hope more of you will decide to submit your research to us in the future and we promise to do our best to make sure your experience is the best it can be. We welcome feedback and direct communication from both our authors and readers, so do not hesitate to write to any of our Editorial Board members or to our EiC directly at any time. We promise a quick, if not a satisfying, response!

II. CONTENT
We open the IEEE JOURNAL OF MICROWAVES, volume 2, issue 3 with a very special combined Pioneer and Microwaves 2 We note that it may be inaccurate to define a recidivism rate based on the total number of listed authors, but if we go by the corresponding author only or perhaps the last listed author on a group paper, this also distorts the actual repeat submission count, as often a technical group will submit multiple papers with different first or corresponding authors on each. Any co-author may also influence the decision as to where a paper is submitted. In order to get a more reproducible formula we therefore chose to use the total author list as indicated in the text. If you can suggest a better accessible statistic to use we are all "ears"! are Everywhere editorial feature article on 2022 IEEE President K.J. Ray Liu. Although Ray Liu is a household name in the signal processing field, his most significant technical contribution actually resides in the microwave realm and involves the very interesting, and now rapidly growing field (thanks to his contributions) of time-reversal (TR) focusing. Our article covers both Professor Liu's extremely interesting personal background, as well as his particular contributions to microwave communications applications with attention to the particular details of TR focusing.
Our first invited article this issue is from noted IEEE Fellow and prior Commonwealth Scientific and Industrial Research Organization (CSIRO) Director, Y. Jay Gao (now at Univ. of Tech., Sydney, Australia), in conjunction with post-doctoral fellow Ting Zhang at Univ. of Tech., Sydney, Australia, and Jia Du at CSIRO. The authors provide a comprehensive review of the use and performance of high-temperature superconductor devices, circuits, and systems, specifically targeted for commercial wireless communications infrastructure. Recent progress in this area is impressive and you will likely be pleased by how close we are finally coming to the use of high-Tc components in a widespread commercial application. Their paper is titled "High-Tc Superconducting Microwave and Millimeter Devices and Circuits -An Overview." Our second invited manuscript comes from noted antennas, metamaterials, and electromagnetics theorist Filippo Capolino and team at University of California, Irvine, "High-Sensitive Parity-Time Symmetric Oscillator in Coupled Transmission Lines with Nonlinear Gain." This paper discusses oscillators based on a novel degeneracy that produces a double pole (EPD, or exceptional point of degeneracy) that can be used to construct coupled transmission line resonators with very high sensitivity, suitable for a variety of microwave sensing elements.
The third invited contribution this issue is from Anthony Grbic and colleagues at University of Michigan, Ann Arbor: "Design of Planar and Conformal, Passive, Lossless Metasurfaces that Beamform." This paper looks at synthesizing specific beamforming characteristics using both planar and conformally shaped metasurfaces. Examples include a perfect aperture efficient metasurface antenna, a beam scanning reflect-array with controlled sidelobes, and a reflectarray using a conformal metasurface structure. Detailed synthesis and optimization techniques are discussed and examples of useful realizable structures are shown.
In "First Demonstration of Dynamic High-Gain Beam Steering with a Scanning Lens Phased Array," notable antennas expert, Nuria Llombart and the group of S. Bosma, N. van Rooijen, M. Alonso-delPino, and M. Spirito at Technical University of Delft, Netherlands, describe the first demonstration of a widely scanned sparse lens array. The configuration has ±20°scan range at W-band (75-110 GHz) and grating lobe levels are below 10 dB. The concept is based on a novel waveguide-fed leaky-wave antenna construct with very high lens illumination efficiency. Measured and calculated performance are compared and agree extremely well, especially for these high frequencies.
Elias Alwan and student M.N.A. Tarek at Florida International Univ., Miami, teamed up with R. Hokayem at Silicon Labs, Montreal, Canada and M.H. Novak at Novaa Ltd., Columbus, Ohio for "A Two-Stage Wideband RF Cancellation of Coupled Transmit Signal for Bi-Static Simultaneous Transmit and Receive System." This paper discusses a new self-interference suppression technique filter that provides more than 50 dB of isolation across 500 MHz of bandwidth centered between 1 and 1.5 GHz. The component implementation is aimed at improving the effectiveness of simultaneous transmit and receive systems in communications networks.
Sparse antenna arrays for automotive radars is the subject of the paper, "Sectorized FMCW MIMO Radar by Modular Design with Non-uniform Sparse Arrays," by C.A. Alistarh et al. at Heriot-Watt University, UK, Symon K. Podilchak and John Thompson at University of Edinburgh, Scotland, and Jaesup Lee from Samsung Advanced Institute of Technology in South Korea. The manuscript describes a very broad field of view (±90°), short range, sparse array, 3-sector radar construct with 6% bandwidth at 24 GHz (scalable to 77 GHz) and 2.2°object spacing resolution.
Martin Vossiek of Friedrich-Alexander University, Erlangen-Nürnberg, Germany, continues to impress with his many excellent contributions to our journal. In this issue, he and his group provide two papers on RFID. The first, "SAW RFID Tag Spatial Division Multiple Access Based on 3D Reflector Response Localization Using a Wideband Holographic Approach," discusses a method for deconvolving overlapping identification signals from closespaced surface acoustic wave radio frequency identification tags (SAW RFID). They use a 3D holographic technique based on synthetic aperture radar to provide individual tag signal collision suppression. The technique is experimentally verified and shows great promise for direct integration into existing SAW RFID systems. In a second paper authored by Patrick Stief, Ingrid Ullmann, Georg Körner, and Konstantin Root, and Martin Vossiek, titled, "Chipless RFID Polarimetric Radar Barcodes Encoded by Dipole Scattering Domains" a technique for implementing a fully passive microwave polarimetric barcode-based RFID tag is presented. The novel concept uses numerous dipole antennas in prearranged geometric patterns to produce a polarization-sensitive response. The authors test the system at W-band (75-110 GHz) using an imaging radar reader. They can achieve 30-bit data readout capacity on a 45x45mm tag without the need for an active chip or otherwise powered RFID device, demonstrating the radar equivalent of an optical barcode (QR) reader.
Our next two papers involve novel uses of liquid crystal structures. In "Reconfigurable Liquid Crystal Dielectric Image Line Leaky Wave Antenna at W-Band," noted microwave researcher Rolf Jakoby and students at Technical University of Darmstadt in Germany employ a liquid crystal (LC) substrate filler that can vary its permittivity (orientation of the mostly linear liquid crystal particles) through applied voltage and magnetic field. They place a linear-array based leaky wave metallic antenna over the variable LC-filled substrate and tune the frequency varied beam angle by changing the substrate permittivity from roughly 2.5 to 3.5. Measurements at W-band confirm the concept, with demonstrated beam steering of approximately 10 degrees induced by the LC applied voltage. In a second 3D liquid crystal applications contribution also from Rolf Jakoby, this time with colleagues from Kiel University and Otto von Guericke University in Germany, a 30 GHz tunable filter design is presented. Again the liquid crystal solution is injected into a holder which can change its relative permittivity by adjusting an applied voltage or magnetic field that affects the orientation of the mostly linear LC particles inside. The LC-filled chambers are placed in a waveguide style groove gap pin filter and shown to produce a bandpass response that can be tuned by 3.5% with 2 dB insertion loss and a return loss below 20 dB at 30 GHz using less than 100 V of bias for LC reservoirs.
"Ceramic Additive Manufactured Monolithic X-Shaped TM Dual-Mode Filter," from Michael Höft and student Daniel Miek at Kiel University in Germany, in conjunction with team members from Tesat Spacecom, Backnang, Germany, Lithoz GmbH, Vienna, Austria, and ESA, Noordwijk, Netherlands, present a 3D printed ceramic filter at 6 GHz. The ceramic filter has a greatly reduced volume (compared to a waveguide cavity filter) and a high-Q. 3D printing allows the filter structure to be manufactured with a very complex internal structure, in this case a 3D drooping cross design. The measured filter has very high temperature stability, low insertion loss, and a Q above 840.
In our next to last paper, we present a contribution from Kamal Samanta of Sony Europe, London, UK, and Shiban Koul and student S. De of IIT Delhi, India: "Low Profile Dielectric Rod Tuned Reconfigurable Band Pass Filters." The paper describes a simply fabricated tunable band pass filter implemented in substrate integrated waveguides (SIW). Inserted and movable dielectric rods provide the variable filter bandpass characteristics. Their design procedure and realized structures represent a very cost-effective passive solution for a ubiquitous component in communications systems, and are especially intended for remote area deployment and operations.
Our final paper this issue involves extremely detailed characterization of an animal RF exposure chamber to relate the position-dependent electric field strength to the total animal exposure level. The idea is to correlate directly with the Specific Absorption Rate (SAR) and elucidate any errors. The paper, "Quantification of Exposure Level in a Reverberation Chamber for a Large-Scale Animal Study," submitted by Ryota Ito of Nagoya Institute of Technology and colleagues in Japan and Korea, supports a long-term small animal toxicity study conducted in the USA on the effects of mobile phone radiation at 900 and 1900 MHz. The paper gives a measured uncertainty in the whole-body SAR derived in the USA study of 16% and also presents supporting finite difference time domain analyses for the USA study and an ongoing duplicate study being conducted jointly by groups in Japan and Korea. This concludes our paper queue for volume 2, issue 3 of IEEE JMW. We hope you enjoy, download, and cite these manuscripts. We will return in October with an equally exciting set of regular papers, as well as several invited and special series articles that we know you will appreciate.

III. OUR EDITORIAL TEAM
Our twenty-four Topic Editors have been selected from the Chairs, Vice-Chairs, and key participants of all twenty-six active technical committees 3 within the Microwave Theory and Technology Society. In addition to technical expertise and academic, governmental, and industrial backgrounds, we also have significant publications experience and leadership skills on our Editorial Board, which includes three former and three current IEEE journal Editors-in-Chief, a former MTT-S AdCom President, and twelve current and former IEEE journal Associate Editors. Our technical efforts are aided by a senior Administrative Editor, Kara McArthur, and a very experienced Assistant Editor, Sharri Shaw. Our veteran IEEE Production Editor is Joanna Gojlik. A group of us met for the first time in person at the recent Panel of Editors workshop in New Brunswick, New Jersey this past April, where we discussed our philosophy, exchanged ideas, and caught up on details relevant to our management of the journal as we move into year two. Much of our Editorial Board will also meet in person at the 2022 MTT-S International Microwave Symposium in Denver, Colorado on June 21 st when we plan to hold an in person board meeting as well as an open panel session and "Get to Know our Journals" reception [3]. We hope to see some of you as well! Photos and short bios of our team can be found at the end of this editorial introduction.

ACKNOWLEDGEMENT
This quarter we would like to especially acknowledge Elsie Vega and Erin Dolan for supporting our "Get to Know Our Publications" event at the IEEE MTT-S International Microwave Symposium, and Rob Caverly (one of our own TE's and EiC of Microwave Magazine), for helping to advertise both the IMS Publications Event and our upcoming special 70 th Anniversary of the MTT Society Special Issue. 3 The Dr. Siegel has been recognized with 75 NASA technology awards, ten NASA team awards, NASA Space Act Award, three individual JPL awards for technical excellence, four JPL team awards, and IEEE MTTS Applications Award in 2018. He is honored to continue the responsibilities in 2022 as the Founding Editor-in-Chief IEEE JOURNAL OF MICROWAVES, which he hopes will invigorate the microwave field. Among many other functions, he was the Founding Editor-in-Chief of IEEE TRANSACTIONS ON TERAHERTZ SCIENCE AND TECHNOLOGY, from 2010 to 2015, and the Founder, in 2009, Chair through 2011, and elected General Secretary since 2012, of the International Society of Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), the world's largest non-profit society devoted to THz science and technology. and mmWave imaging, stand-off THz sensing, multistatic radars, advanced signal-processing techniques, terahertz technology, and last but not least, automotive radar design and characterization. Over the past decade, he pioneered the body scanner technology with the first fully electronic multistatic millimeter wave imaging systems, which are being deployed worldwide today at airport checkpoints. In the recent years, he has been advancing the qualifications of automotive radars, towards autonomous driving capabilities.  He held/holds visiting/honorary professorships with various universities around the world and has graduated more than 73 Ph.D. and 95 M.Sc. students. He has authored or coauthored more than 1400 refereed papers, and a number of books and book chapters and filed more than 50 patents. Prof