|Dr. Benoît Derat
Senior Director of Development (1SE)
EMC, OTA, Antenna and A&D Test Systems
Rohde & Schwarz GmbH & Co. KG
|Over-The-Air Testing Using Plane-Wave Synthesis: from Theory to Realization
Abstract & Bio
Near-field focusing techniques for antenna measurements started to develop in the late 50s. Plane-wave synthesis (PWS), which is utilizing a phased antenna array to generate a close to planar wavefront in a target region, belongs to this category of techniques. PWS presents two major features, giving it a unique benefit: (i) it allows a true emulation of a far-field condition, as perceived from the device under test (DUT); (ii) it reduces the necessary range length by a factor of 2 or more compared to a compact antenna test range (CATR) with similar quiet zone performance. With these advantages in mind, our group set out to create the first turnkey solution implementing this method, the R&S PWC200, with a specific focus on 3GPP over-the-air (OTA) conformance testing of 5GNR active antenna system (AAS) base stations (BS). Barriers were however much higher than expected and multiple inventive steps were required to turn this attractive concept into an accurate measurement system. This keynote retraces our bumpy engineering path, with a highlight on the main technical and scientific challenges (array calibration, phase shifter imperfections, high power handling, broadband frequency dispersion, etc…) and novel solutions which finally enabled the technology to an adequate level.
Dr. Benoît Derat started his career at SAGEM Mobiles as an antenna design and electromagnetics research engineer. During these years, he gained expertise in antenna measurements and simulations, and actively contributed to innovation and international standardization in near-field techniques for human exposure assessment to radiofrequency waves. In 2009, he founded the company ART-Fi which created the first vector-array SAR measurement system and initiated the IEC 62209-3 standard development. Dr. Derat operated as the CEO and President of ART-Fi until 2017, before joining Rohde & Schwarz at the Munich headquarters. He is now leading the R&D for EMC, OTA, antenna and A&D test systems, as Senior Director of Engineering. Dr. Derat is the author of more than 70 scientific conference and journal papers, as well as an inventor on multiple patents relating to antenna and electromagnetic field measurements.
EurAAP Invited Speaker
Prof. Giuseppe Vecchi
Politecnico di Torino, Italy
IEEE AP-S Invited Speaker
Prof. Mahta Moghaddam
University of Southern California
|Antenna Measurements beyond Nyquist |
Abstract & Bio
Antenna measurement is based on acquiring field samples according to well-known “Nyquist-like” sampling density criteria. In NF-FF systems, research has been done, and is still actively pursued, on optimizing the number of necessary NF samples, typically with non-uniform sampling schemes. Overall measurement time optimization may be somewhat trickier, as it also depends on the specific mechanical properties of the probe movement system. This research is intended to reach as close as possible to the ideal “Nyquist” limit. Going beyond this limit is not unphysical, though: it however requires to insert a-priori information into the algorithm that computes the radiated FF starting from the NF samples.
Effective ways to achieve under sampling will be the main topic of this talk. The approach has multiple application areas: drastic speedup of the measurement time for accurate characterization of antennas, both self-standing and mounted on platforms; verification of complex platforms where only a limited number of field samples can be obtained; verification of compliance for rapid testing (e.g. in-line).
The key ingredient is a meaningful way of exploiting whatever available a-priori information on the AUT into the NF-FF process. The process is two-phase: a model-building phase, and a phase, based on the available measurement, in which the model is matched to measured data to provide the field everywhere (both in NF and FF regions).
The first way to provide information is through knowledge of the geometrical structure of the AUT; this allows to carry out partial or full simulation of the AUT, prior to physical measurement; this gives rise to an important class of algorithms. Uncertainties in the knowledge of the AUT can be accommodated, at the expense of more computation. The technique can be applied both to precise measurements and to “sniff” testing, i.e. verification of compliance with very reduced sampling.
Other ways of providing information are relevant to fast testing. In a series production, information may be in the form of measurements of a certain number of sample AUT, or even in the form of the requirement mask alone.
The talk will also touch upon NF-FF on non-canonical grids, which is useful in some embodiment of the technique.
Giuseppe Vecchi received the Laurea and Ph.D. (Dottorato di Ricerca) degrees in electronic engineering from the Politecnico di Torino, Torino, Italy, in 1985 and 1989, respectively, with doctoral research carried out partly at Polytechnic University (Farmingdale, NY). He was a Visiting Scientist with Polytechnic University in 1989-1990. Since 1990 he is with the Department of Electronics, Politecnico di Torino, where he has been Assistant Professor, Associate Professor (1992 – 2000), and Professor. He was a Visiting Scientist at the University of Helsinki, Helsinki, Finland, in 1992, and has been an Adjunct Faculty in the Department of Electrical and Computer Engineering, University of Illinois at Chicago, 1997-2011. Since 2015 he serves as the Director of the Antenna and EMC Lab (LACE) at Politecnico.
He has been an Associate Editor of the IEEE Transactions on Antennas and Propagation, Chairman of the IEEE AP/MTT/ED Italian joint Chapter, and member of the IEEE-APS Educational Committee.
Prof. Vecchi is a Fellow of the IEEE, a member of the Board of the European School of Antennas (ESOA), and a member of the IEEE Antennas and Propagation Standard Committee.
His main professional experience and research activities concern analytical and numerical techniques for antennas analysis, design, measurement and diagnostics.
| Role of Accurate Near- and Far-Field Antenna Characterization in Imaging
Abstract & Bio
It would be a trivial statement to say that we use antennas of all sorts to transmit and receive microwaves for imaging application. It is far from trivial, however, to characterize and account for the transmit/receive properties of these antennas in support of quantitative image formation, whether the antennas are in the far field – such as in remote sensing and radar applications – or in the near field – such as in medical imaging and nondestructive testing applications. This talk will cover some of our work on both remote and proximal microwave sensing, which, respectively, require detailed considerations of far-field and near-field antenna properties. In radar remote sensing, our goal is to quantitatively retrieve environmental variables, such as vegetation and soil characteristics, from a small number of polarimetric observations. The retrieval process is often formulated as an optimization problem in which the rather complex electromagnetics scattering models are simplified and parameterized in terms of a small number of unknown, allowing the estimation of the unknown geophysical variables via local or global iterative solutions. More recently, learning-based methods have also been proposed for the retrieval process. In medical imaging and nondestructive testing applications, our goal is to reconstruct the full 3D dielectric properties of the object domain. This is typically done by formulating the problem as a nonlinear inverse scattering problem, solving it by iterations on forward scattering models and/or by combinations of EM-based scattering and learning-based approaches. In both classes of problems, the success of the imaging and inverse scattering solutions hinges on the accurate knowledge of the scattered field or the scattering cross section, which in turn requires finesse in characterizing the transmit and receive behavior of the antennas and their interactions with their immediate environment. We will present examples of scenarios for both radar remote sending and medical imaging applications and the methods we have investigated to account for antenna behavior as an integral part of the imaging system.
Prof. Mahta Moghaddam is the Ming Hsieh Chair in Electrical and Computer Engineering, Director of New Research Initiative at the Viterbi School of Engineering, Co-Director of the Center for Sustainability Solutions, and Distinguished Professor at the University of Southern California, Los Angeles, CA. Prior to that she was at the University of Michigan (2003-2011) and NASA Jet Propulsion Laboratory (JPL, 1991-2003). She received the B.S. degree in 1986 from the University of Kansas, Lawrence, Kansas with highest distinction, and the M.S. and Ph.D. degrees in 1989 and 1991, respectively, from the University of Illinois at Urbana-Champaign, all in Electrical and Computer Engineering. She has introduced new approaches for quantitative interpretation of multichannel radar imagery based on analytical inverse scattering techniques applied to complex and random media. She was a Systems Engineer for the Cassini Radar and served as Science Chair of the JPL Team X (Advanced Mission Studies Team). Her most recent research interests include the development of new radar instrument and measurement technologies for subsurface and subcanopy characterization, development of forward and inverse scattering techniques for layered random media especially for root-zone soil moisture and permafrost applications, geophysical retrievals using signal-of-opportunity reflectometry, and transforming concepts of radar remote sensing to medical imaging and therapy systems.
Dr. Moghaddam is a member of the NASA Soil Moisture Active and Passive (SMAP) mission Science Team and a member of the NASA Cyclones Global Navigation Satellite System (CYGNSS) Science Team. She was the principal investigator of the AirMOSS NASA Earth Ventures 1 mission. She served as the IEEE Antennas and Propagation Magazine from 2015 to 2019 and is currently President of the IEEE Antennas and Propagation Society. Dr. Moghaddam is a member of the National Academy of Engineering.
|Dr. Alan Fenn|
MIT Lincoln Laboratory
|Dr. Goutam Chattopadhyay
NASA Jet Propulsion Laboratory
|The MIT Lincoln Laboratory RF Systems Test Facility for Rapid Prototyping|
Abstract & Bio
The MIT Lincoln Laboratory RF Systems Test Facility (RFSTF) is a research and development rapid prototyping facility with resources to design, fabricate, and measure antennas, radar targets, and electromagnetic systems for surface, airborne, and space applications. The RFSTF is comprised of six anechoic chambers, a systems-integration lab (SIL), high-bay staging area / rapid prototype shop, and RF laboratory. The RFSTF is co-located with the MIT Lincoln Laboratory Flight Test Facility, which allows rapid integration of RF sensors with airborne platforms. The six shielded anechoic chambers (tapered, millimeter-wave, small near-field scanner, system-test, compact range, and large near-field scanner) allow for antenna, radar-cross section (RCS), and electromagnetic system measurements over a wide frequency range. The three large system-test, compact range, and planar near-field chambers can accommodate large, heavy, test articles, making use of an overhead crane (system-test chamber), rolling gantry with crane (compact range chamber), and reconfigurable rolling cart (large near-field scanner). The system test rectangular chamber provides far-field and spherical near-field scanning capability up to 20 GHz. Antenna and RCS measurements are performed in the compact range from UHF up to 100 GHz with a blended rolled-edge reflector. The large near-field scanner chamber is configured to calibrate and measure gain radiation patterns of large phased array antennas up to 50 GHz. In the tapered chamber, a dual-polarized ultrawideband feed allows measurements from about 250 MHz up to 3 GHz, and higher frequencies. The rectangular millimeter wave chamber operates from about 4 GHz to 100 GHz. The small near-field scanner chamber is used primarily for calibrating and testing small phased array antenna panels up to 26 GHz. The rapid prototyping shop has a wide variety of machining tools and 3D printers to fabricate antennas, target-mounting fixtures, and other mechanical pieces necessary to aid and assist in any testing in the facility. The shop also has a high-bay area with overhead crane, allowing for a wide range of mechanical work to be performed on larger devices and systems. The RF Laboratory is a general-purpose area that can be configured to support the needs of many different projects. Example RFSTF measurements of phased arrays and other antennas are described.
Dr. Alan J. Fenn is a Senior Staff Member in the RF Technology Group in the Advanced Technology Division at MIT Lincoln Laboratory. He is currently involved in the development of ultrawideband antennas and arrays for radar and communications applications. He joined Lincoln Laboratory in 1981 and from 1982 to 1991 was a member of the Space Radar Technology Group, where his primary research was in adaptive phased-array antenna development. From 1992 to 1999, he was Assistant Leader in the RF Technology Group, managing programs involving measurements of atmospheric effects on satellite communications. In 2000, he was elected a Fellow of the IEEE for his contributions to the theory and practice of adaptive phased-array antennas. He served as Technical Program Chair for the 2018 IEEE International Symposium on Antennas and Propagation He served as Technical Program Chair for the 2019 IEEE International Symposium on Phased Array Systems and Technology. He is an author of 5 books and numerous journal articles and conference papers on the subject of adaptive antennas and phased arrays. He received a B.S. degree from the University of Illinois–Chicago and M.S. and Ph.D. degrees from The Ohio State University, all in electrical engineering.
|Space Science and Instruments at NASA
Abstract & Bio
NASA’s Jet Propulsion Laboratory, which completed eighty years of its existence in 2016, builds instruments for NASA missions. Exploring the universe and our own planet Earth from space has been the mission of NASA. Robotics missions such as Voyager, which continues to go beyond our solar system, missions to Mars and other planets, exploring the stars and galaxies for astrophysics missions, exploring and answering the question, “are we alone in this universe?” has been the driving force for NASA scientists for more than six decades.
Fundamental science questions drives the selection of NASA missions. We develop instruments to make measurements that can answer those science questions. In this presentation, we will present an overview of the state of the art instruments that we are currently developing and layout the details of the science questions they will try to answer. Rapid progress in multiple fronts, such as commercial software for component and device modeling, low-loss circuits and interconnect technologies, cell phone technologies, and submicron scale lithographic techniques are making it possible for us to design and develop smart, low-power yet very powerful instruments that can even fit-in a SmallSat or CubeSat. We will also discuss the challenges of the future generation instruments in addressing the needs for critical scientific applications.
The research described herein was carried out at the Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA, under contract with National Aeronautics and Space Administration.
Goutam Chattopadhyay is a Senior Research Scientist at the NASA’s Jet Propulsion Laboratory, California Institute of Technology, a Visiting Associate at the Division of Physics, Mathematics, and Astronomy at the California Institute of Technology, Pasadena, USA. He received the Ph.D. degree in electrical engineering from the California Institute of Technology (Caltech), Pasadena, in 2000. He is a Fellow of IEEE (USA) and IETE (India) and an IEEE Distinguished Lecturer.
His research interests include microwave, millimeter-wave, and terahertz receiver systems and radars, and development of space instruments for the search for life beyond Earth.
He has more than 350 publications in international journals and conferences and holds more than fifteen patents. He also received more than 35 NASA technical achievement and new technology invention awards. He received the IEEE Region 6 Engineer of the Year Award in 2018, Distinguished Alumni Award from the Indian Institute of Engineering Science and Technology (IIEST), India in 2017. He was the recipient of the best journal paper award in 2020 and 2013 by IEEE Transactions on Terahertz Science and Technology, best paper award for antenna design and applications at the European Antennas and Propagation conference (EuCAP) in 2017, and IETE Prof. S. N. Mitra Memorial Award in 2014.