ABSTRACT. In this paper we propose closed-form formulas for the effective refractive index of a wave propagating along two parallel corrugated surfaces arranged in a glide-symmetric configuration, having a small groove compared to the period. This kind of structure has proved to suppress the frequency dispersion typical of periodic material when the gap between the surfaces is small. The closed-form expressions show analytically this property and prove it for the first time, by means of the lack of a frequency dependence.

ABSTRACT. In this work, an antipodal Vivaldi antenna optimized with different metalenses for wideband applications is designed. This light-weighted antenna is wideband and exhibits good gain in the whole bandwidth. The employment of metalenses with variable metamaterials dimensions allows to increase maximum gain of about G=2 dB in the frequency band f=7-10 GHz, without reducing the working bandwidth of the antenna. Prototypes have been fabricated and characterized, showing good agreements with simulations.

ABSTRACT. This paper discusses the dispersion diagrams of holey periodic metasurfaces, which have been computed by analyzing either the primitive unit cell or a supercell of the structure. Particularly, the connection of the dispersion diagram of the supercell to the standard diagram of the primitive unit cell is investigated. The appearance of additional “anomalous” modes is explained and exemplified in the case of a rectangular supercell composed of two or three square unit cells.

ABSTRACT. The replacement of pins by glide-symmetrical holes in gap waveguide structures is a possibility that is attractive from the point of view of manufacturing but complicates the design when dealing with complex structures. In this work, a discussion on the possibilities when employing holes for a realization of a gap waveguide structure, together with several examples of antenna designs based on these possibilities, are presented.

ABSTRACT. A novel multilayer dual band filter designed in wifi and 5G NR FR1 frequencies is proposed. For the implementation, a Substrate Integrated Waveguide (SIW) is loaded with Complementary Split Ring Resonators (CSRR). Evanescent mode is achieve below the cutoff frequency of SIW line. Resonators which are placed in different layers are tuned and optimized to fit the working frequencies. The center frequencies are reached in 2.4GHz for wifi applications and the second one at 3.5GHz for 5G NRFR1 communication.

ABSTRACT. This contribution presents the design of a 60-GHz planar antenna system for radiative near-field region line-ofsight (LoS) link, based on an orbital angular momentum (OAM) multiplexing. The antenna system is composed of a radial line slot array (RLSA) fed by a Butler network, made in post-wall waveguide technology, and located underneath the array. The network can launch different progressive phase states in the RLSA parallel plate waveguide (PPW) to radiate three different OAM beams. The design concept has been verified by prototyping and testing a 20 free-space wavelengths radius antenna. The measurements show that the proposed antenna can generate simultaneously the three OAM-mode states n = 0, －1, and +1.

ABSTRACT. A Luneburg lens quasi-optical beam-former is used to excite a leaky-wave antenna at 275 GHz. Both the lens and the antenna are fabricated on a Cyclic Olefin Copolymer (COC) substrate. The full system is etched on the polymer by photolithography. Numerical results show a reflection coefficient lower than −24 dB and a gain higher than 21 dBi over a 40% fractional bandwidth, spanning from 220 GHz to 330 GHz. The efficiency of the antenna is estimated to be 28% at the center frequency (275 GHz).

ABSTRACT. Transmit-arrays (TAs) can be a cost-effective solution for high gain steerable antennas using millimeter waves. For some applications these antennas can be a viable alternative to the extremely compact and agile phased-arrays counterpart. The main motivation is to reduce the high costs associated with the complex and lossy feeding networks of phased arrays - a fundamental factor when aiming for mass-market technology. Combining the flexibility of TAs with 3D printing can further enhance the low-cost potential of these antennas. This work focuses on apertures composed by a single dielectric material compatible with the affordable 3D printing technique, Fuse Deposition Modelling (FDM). However, the resulting aperture will be thicker and have higher losses comparing with printed circuit board (PCB) TAs. We show that, despite these limitations, the dielectric implementation of TAs performs well even for demanding designs. We present several dielectric realizations of a TA design capable of wide mechanical beam scanning (up 49 degrees) with a low profile (F/D=0.34) and 26 dBi maximum gain at 30 GHz. We assess how the performance of this antenna is affected by the way that the TA phase correction is crafted in the dielectric block.

ABSTRACT. Very few designs are reported in the terahertz range for realizing dynamic beam-steering of the antenna radiation pattern at a fixed frequency. In this work, we propose a one-dimensional leaky-wave antenna based on nematic liquid crystals (NLC). More specifically, an NLC cell is sandwiched between two foam layers, the top one patterned with a partially reflecting sheet (PRS), and the bottom one entirely metalized to have a ground plane. Two lateral perfect magnetic conductor walls allow for a dominant TM leaky mode propagating in the structure. The beam is then steered by applying a low-frequency driving voltage through the ground and the PRS. The trade-off among radiation efficiency, angular steering range, and gain that commonly affects any reconfigurable antenna is properly handled through a suitable choice of the design parameters. Full-wave results are finally provided to demonstrate the concept.

ABSTRACT. The capabilities of frequency-selective surface (FSS) as free-space filters for wireless communications in the 300 GHz band are here demonstrated experimentally. The presence of a filter plays a key role to protect wireless communications from out-of-band interference without resorting to computation intensive forward error correction schemes. An FSS filter is suitably designed to exhibit an almost linear phase and a low insertion loss over a 20 GHz bandwidth centered around 270 GHz. A method based on both full-wave simulations and numerical techniques is developed to predict the bit-error rate (BER) performance of a filter-based wireless communication when an on-off keying modulated signal is sent at 14 Gb/s. Results are corroborated through measurements and confirm that the filters marginally affect the BER within the operating bandwidth while it is capable of strongly rejecting out-of-band interferences. In future works, the performance of more elaborated filters and modulations schemes will be investigated in detail.

ABSTRACT. In this paper, we investigate the short-circuit calibration step of the open-ended coaxial probe (OECP) which is one of the major challenges when measuring complex dielectric permittivity (CDP) of a material under test (MUT). The effect of short-circuit inaccuracy can be mitigated by an alternative calibration approach by taking advantage of the calibration mathematical model of the OECP and using known liquid instead of the commonly used metallic short-circuit procedure. The CDP results of formamide as the MUT are compared using three known liquids acetone, butanol, and 2-propanol respectively, as the shorting material during the calibration procedure. The MUT and calibration liquids were simulated with Ansys HFSS simulation program from 0.5 to 6 GHz frequency range with a resolution of 0.25 GHz. The commercially available Speag DAK 3.5-mm OECP was replicated with similar material specifications and dimensions. In order to retrieve the CDPs from reflection coefficients (RCs) obtained from the probe-MUT interface, a multi-frequency Gauss-Newton inversion method based is implemented. The results demonstrate that it is important to select an appropriate calibration material during the calibration procedure to ensure reliable CDP results. The study also indicates that further numerical investigation is required to explain the relationship between the calibration mathematical model and CDP.

ABSTRACT. In the present work, we investigated the dielectric characterization of cylindrical shaped tissues via an open-ended coaxial probe. So long as biological tissues are not stiff, in this contribution we look for the minimum cylinder diameter and the related insertion depth in the tissue detectable by our probe. From numerical simulations, we derived the reflection coefficient probe aperture plane, and then we used it as input data in our Virtual Transmission Line Model (VTLM) based algorithm for dielectric properties reconstruction. Furthermore, we numerically analyzed the presence of a dielectric coating which hosts the tissue under test and wraps the coaxial probe itself. The aim is exploiting the sample shape derived from a core needle biopsy procedure which allows avoiding sample manipulation. The same dielectric coating allows reducing fringing field effect at the probe-to-tissue region thus enhancing probe dielectric reconstruction properties. The proposed system can be used in medical field as a decisional support in pre-pathological malignant tissue recognition purposes.

ABSTRACT. Magnetic resonance imaging (MRI) is widely used in several medical applications, which include the non-invasive and in-vivo investigation of the electrical properties of biological tissues. Such kind of inverse problem can be addressed by means of iterative methods, which are time and memory consuming and solution may converge to local minima. To accelerate the reconstructions and bypass the problem of local minima, we propose and compare two different learning methods to face the inverse problem underlying the MRI based electrical properties tomography, one based on supervised descent method and the other one on a cascade of multi-layers convolutional neural networks. Both methods are trained and tested using 2D simulated data of a human head model.

ABSTRACT. In this paper, a preliminary review of the dielectric measurement methods as a function of both frequency and temperature is presented. In particular, the two most popular approaches for heating the samples up to ablative temperatures (i.e., water bath and antenna applicator) and two dielectric measurement setups (i.e. open-ended coaxial probe and resonant cavity) are analysed and compared, highlighting the pros and cons of each approach.

ABSTRACT. Low-cost and flexible passive RFID tag antennas for blood tracking (tubes and bags) are presented in this paper. The major challenge in designing such antennas for blood tracking is that the latter presents high dielectric permittivity and loss, which degrades the good impedance matching between the RFID chip and the antenna leading to a decrease in the performance of the RFID tag antenna such reading range. The main performance of the proposed RFID tag antennas has been evaluated numerically and experimentally. The measured results show that the reading range of the RFID tag antennas is more than 2.2 m, which makes them suitable for real blood tracking applications.

ABSTRACT. This paper presents a novel reconfigurable MIMO 4x1 microstrip patch antenna loaded with a mixture liquid crystal E7 resonating at 60 GHz for 5G and WiGig applications. The single proposed antenna is a rectangular patch antenna with a total grounded substrate fed with microstrip line. The mixture liquid crystal (E7) is injected in an optimal location underneath the patch and around it. Using the MIMO technology, the gain increases from 7.13 dB for the single antenna to 13.5 dB. Modifying the permittivity of the mixture liquid crystal (E7) allows the adjusting of the resonate frequency. The simulated results of the reflection coefficient show that the resonance frequency tuned from 62.28 to 69.14 Ghz, therefore the variation frequency ∆Fr= 6.86 GHz characterized with a suitable gain reaches a value of 13.5 dB. The liquid crystal ameliorates performances of the proposed antenna and offers tunability.

ABSTRACT. In this paper, some numerical results on the possibility to design a 3D-printable dielectric ReflectArray (RA) antenna with beam steering capabilities are presented. The adopted unitcell consists of a single-layer dielectric element perforated with a square hole, whose side is varied to change the phase of the reflection coefficient. Since the unit-cell behavior is quite stable with the direction of arrival of the incident field, it is used to design a 52x52 reflectarray working in Ka-band. Its numerical characterization proves that the RA is able to provide less than 2 dB of gain losses over a scanning range of +/-30° in the vertical plane.

ABSTRACT. In this paper, a new rat-race coupler, based on slow-wave coplanar stripline transmission lines, is proposed for 120 GHz applications. High quality factor transmission lines were employed. A parametric analysis targeting the geometrical variables of slow-wave is presented. A 19.6% area reduction for the core of the coupler is achieved thanks to slow-wave technique manifested in conductive ribbons placed under transmission lines. Simulation results show that isolation and reflection coefficients are preserved under 15 dB. Insertion loss value is 4.3 dB for the SW-CPS version at 120 GHz. Maximum amplitude impalance is 0.6 dB reported at 140 GHz. While, phase imbalance difference for the proposed structure doesn���t exceed 2.5�� for the whole bandwidth of interest.

ABSTRACT. An aperture coupled magneto-electric (ME) dipole for 5G Backhauling systems is proposed in this article. A substrate integrated waveguide (SIW) is used to fed the antenna. The electric dipole is formed by four identical patches, while the magnetic dipole is composed by four vertical metallic shorted vias. Moreover, a crossed strip is introduced to connect the four patches in the top metal layer to widen the impedance bandwidth and a cage of vias is added to suppress the generation of surface waves and to boost the radiating element gain. The simulated impedance bandwidth with |S11| < -10 dB for the proposed SIW-fed aperture coupled ME-dipole antenna fully covers the E-Band (71-86 GHz), with a fractional bandwidth of more than 20%. The simulated antenna peak gain is 10.8 dBi at 84 GHz and the 3-dB beamwidth is stable with a variation up to 1 dBi within the band of interest. The proposed E-band ME dipole antenna is very suitable for 5G backhauling systems, as it can be integrated into an array configuration for realizing beam-steering operations.

ABSTRACT. The present article describes the performance of a fourth-order cross-coupled bandpass filter using double-folded microstrip hairpin resonators for the improvement of skirt characteristics and harmonics suppression. The proposed filter is centered at 2.5 GHz with a fractional bandwidth of 4%. At first, the central folded pair of resonators of the unit hairpin-line cell has been modified with periodic trapezoidal corrugations to achieve improved skirt characteristics with the attenuation level of 40 dB and a compact circuit area with a size reduction of 11.36% over the conventional cross-coupled filter with the same specifications. However, the harmonics have not been suppressed significantly by this compact structure. Subsequently, trapezoidal-shaped meander spurlines have been incorporated in each coupled section of the adjacent folded hairpin-line cells for achieving modal phase velocity compensation. As a result, an extended stopband with a rejection level of 34 dB up to

ABSTRACT. Abstract: The talk will focus on the various aspects related to the writing of a technical paper. In particular, the preparation phase, the organization of the manuscript, the appropriate referencing, and some stylistic aspects will be discussed. Moreover, the peer review process will be presented in details, with specific reference to the IEEE journals, and, in particular, to the hands-on experience of the speaker. Last but not least, ethical issues related to the scientific research are also addressed.

Short bio

Luca Perregrini (M’97-SM’12-F’16) was born in Sondrio, Italy, in 1964. He received the “Laurea” degree in Electronic Engineering and the Ph.D. in Electronics and Computer Science in 1989 and 1993, respectively. In 1992 he joined the Faculty of Engineering of the University of Pavia, he is currently full professor of electromagnetic fields and responsible of the Microwave Laboratory. He has been a visiting professor at the École Polytechnique de Montréal, Québec, Canada in 2001, 2002, 2005, and 2006. He has been responsible of many research contracts with prominent international research centers and companies. His main research interests have been focused on the development of numerical methods for electromagnetics, and the design of microwave passive components and antennas. He authored or co-authored more than 100 journal papers and more than 300 conference papers, six book chapters, two textbooks, and co-edited the book Periodic Structures, (Research Signpost, 2006). Prof. Perregrini has been an invited speaker at many conferences, and has delivered invited seminar talks in Universities and research centers worldwide. He is a member ex-officio of the Administrative Committee of the of IEEE Microwave Theory and Technique Society (MTT-S), a member of the Board of Directors of EuMA, and a member of the Technical Committee MTT–15 (Microwave Field Theory) of MTT-S. He was a member of the General Assembly of the European Microwave Association (EuMA) from 2011 to 2013, and he served as a member of prize committees for several conferences/societies. In 2016 he has been elevated Fellow of the Institute of Electrical and Electronics Engineers (IEEE) “for contributions to numerical techniques for electromagnetic modelling”. He was the co-recipient of several best paper awards at international conferences. He was the Technical Program Committee Chair of the International Microwave Workshop Series on Advanced Materials and Processes (IMWS-AMP 2017), Pavia, Italy, in 2017, of the IEEE MTT-S International Conference on Numerical Electromagnetic Modeling and Optimization (NEMO2014), Pavia, Italy, in 2014, and of the European Microwave Conference, Rome, Italy, in 2014. He has been Editor in Chief of the IEEE Transactions on Microwave Theory and Techniques for the term 2017-2019. He was Associate Editor of the IEEE Microwave and Wireless Components Letters from 2010 to 2013, of IEEE Transactions on Microwave Theory and Techniques from 2013 to 2016, of the International Journal of Microwave and Wireless Technologies from 2011 to 2016, and of IET Electronic Letters from 2015 to 2016. He was Guest Editor of the IEEE Transactions on Microwave Theory and Techniques in 2015 and of the International Journal of Microwave and Wireless Technologies in 2015.

ABSTRACT. Philosophy is a reflective enterprise that aims to explicitly articulate and analyze the notions that other disciplines implicitly grasp and deploy. Here, I aim to explicitly articulate and analyze the notions of creativity and innovation by considering their role in engineering design in comparison with the roles they play in science and the arts. Such analysis will lead me to draw some considerations on the place of engineering, science, and the arts in the general framework of human culture, and to argue against the traditional separation between techno-scientific research and the humanities.

Enrico Terrone is Associate Professor of Aesthetics at Università di Genova and Principal Investigator of the ERC project “The Philosophy of Experiential Artifacts”. He was research fellow at the Käte Hamburger Kolleg (Bonn), Gerda Henkel fellow at FMSH (Paris), visiting researcher at Institut Jean Nicod (Paris), and Juan de la Cierva fellow at LOGOS (Barcelona). His main areas of inquiry are aesthetics and the philosophy of technology. He published papers in international journals such as The British Journal of Aesthetics, The Journal of Aesthetics and Art Criticism, Erkenntnis, Philosophy of the Social Sciences. His last book in Italian is Filosofia dell’ingegneria (2019).

ABSTRACT. Abstract: A compact range lined with rows of absorbers on all sides would offer a unique opportunity for the curious mind to study its diffraction effect even under very dim illumination [1]. An extended long object usually gives rise to a bright reflection (glint) when viewed near its surface normal. To take advantage of this phenomenon, a discrete Fourier transform (DFT) on RCS measurements would yield a spectrum of incident wave distribution along that object [2, 3]. Some interesting physics are discussed.

--- References --- [1]. P. S. P. Wei, “Scattering of the residual field above and beyond the quiet zone of a compact range,” Proc. 35th AMTA, Columbus, OH (2013). [2]. P. S. P. Wei, “Measurements on long and rigid objects for radar field probes" Proc. 34th AMTA, pp. 195-200 (2012). [3]. P. S. P. Wei, “Measurements on extended objects for radar field probes," Proc. 41st AMTA, pp. 199-204 (2019); Also presented at ICECOM-2019 (23rd International Conf. on Applied Electromagnetics & Communications), paper s_16_3, Dubrovnik, Croatia, Sept. 30, 2019.

ABSTRACT. A probe-compensated near-field to far-field (NF/FF) transformation with bi-polar scanning particularly suitable for dealing with a flat antenna under test (AUT) is proposed in this work. It properly exploits the non-redundant sampling representations of the electromagnetic fields to develop an efficient sampling representation of the voltage acquired by the measuring probe over the scanning plane, which uses a minimum number of NF bi-polar samples. A two-dimensional optimal sampling interpolation formula is then applied to precisely reconstruct the NF data needed by the classical NF/FF transformation with plane-rectangular scan from the knowledge of these samples. To properly account for the flatness of the AUT, a disk with diameter equal to the AUT maximum dimension is assumed as modeling surface. Such a modeling is much more effective from the NF data reduction viewpoint than the other modelings for quasi-planar AUTs (an oblate spheroid or a double bowl), since, shaping very well the AUT geometry, it allows one to reduce as much as possible the related volumetric redundancy. Numerical results are shown to assess the accuracy of the proposed NF/FF transformation.

ABSTRACT. This contribution presents designs, simulations, and characterizing measurements of Silicon based metamaterial structures. In order to realize a micromachined THz waveguide system on a Silicon wafer, mechanical fixtures to hold and to manipulate the waveguide are needed. If the dielectric constant of these structures is comparable to the waveguide itself, the field confinement is significantly reduced. Therefore, the material is structured as a metasurface using feature sizes that are much smaller than the wavelength. Thus, reducing the effective dielectric constant, while keeping a high mechanical stability. In this contribution the effective dielectric constant of this metamaterial is analyzed at around 300 GHz based on full- wave simulations and also investigated regarding its anisotropic behavior. The simulations are complemented and validated by measurements.

ABSTRACT. There are four main instrumental platforms capable of providing broadband terahertz measurements of optical materials properties. These are: time-domain spectroscopy, photonic-based frequency-domain spectroscopy, vector-network analyzer (electronic-based) spectroscopy, and Fourier transform spectroscopy. Here we present a review of these instruments and discuss their advantages and disadvantages for various applications.

ABSTRACT. We model a radiator/scatterer using an equivalent radiator. We determine shape and size of a radiating surface producing, on a region D, an electromagnetic field close to that generated by the primary radiator/scatterer. For a fixed equivalent radiator’s shape, we deal with the dimensioning issue only. The method exploits the Singular Value Decomposition (SVDs) of the operators relating the radiator/scatterer to the field on D and the equivalent panel to the field on D. The size of the equivalent radiator is determined by minimizing the maximum error between the primary radiated/scattered field and that radiated using D′. We show numerical test cases for a planar radiator with rectangular shape.