The method of moments (MoM) has been commonly used in discretizing the integral equations to solve electromagnetic scattering problems. This talk describes several advances on the topic made by our group in recent years. These advances are related to the fast dipole method (FDM), the adaptive cross approximation (ACA) algorithm, and the characteristic basis function method (CBFM). The talk also includes our current ongoing research: partial modification problems in computational electromagnetics.

In this talk, activities in the following topics will be introduced:

· Radar technology
· Communication technology
· Electromagnetic field and microwave technology
· Microwave photonics and system integration
· Image processing and computer vision
· IC design

In this talk, some dual-polarized antenna elements for base station applications are reviewed. A compact broadband dual-polarized antenna element for base station applications is proposed. The proposed antenna mainly comprises of two pairs of orthogonal dipoles, four couples of baluns, an octagonal pedestal and two kinds of plastic fasteners. A square aluminum sheet is placed between adjacent dipoles to widen the impedance bandwidth of the antenna. Simulated and measured results show that the proposed antenna element has a wide impedance bandwidth of 31.60% with VSWR < 1.6 from 698 to 960 MHz at both ports. High port-to-port isolation and stable radiation pattern with horizontal half-power beam width (HPBW) of 65 degree or so are achieved within the whole working band. The antenna is suitable for existing 2G/3G/4G base station applications.

The advent of the Internet of Things (IoT) and the fifth generation of mobile communication (5G) require a completely new approach to the development of wireless microwave systems. The next generation of microwave systems demands a technology that guarantees easy integration of complex wireless nodes, combination of multiple functions in a single device, low development cost, compact size and low weight. Among the available technologies for the implementation and integration of microwave components and systems, the substrate integration waveguide (SIW) technology looks a very suitable approach, able to satisfy the requirements of the future IoT/5G systems. In fact, SIW technology allows to implement a variety of passive components, active subsystems, and antennas in a simple and cost-effective way, and to integrate entire systems in a single dielectric substrate, thus avoiding complex transitions and undesired parasitic effects. Moreover, the choice of the substrate material represents another key point for the next generation of wireless systems: in fact, depending on the specific application, different requirements are posed. The use of paper, for instance, guarantees the implementation of eco-friendly systems (required in specific fields, e.g., agriculture), a very low material cost, and structure conformability. The use of textile, on the other hand, appears very suitable for the implementation of wearable systems, which can be directly integrated into garments (important, e.g., in biomedical applications). Finally, additive manufacturing techniques like 3D printing represent a rapidly emerging area, which allows the low-cost and ease manufacturing of fully three-dimensional structures.This presentation will cover the perspectives of microwave systems in the new scenario of the IoT/5G, with particular emphasis on implementation of SIW components and antennas with different features and substrate materials.

Energy harvesting is a key method to overcome the challenges associated with a limited battery life time. However, energy harvester systems consist of several components including antennas, filters, rectifiers, and matching networks. As a result, investigation of these components becomes important for development of high efficient and long lasting energy harvesting systems. In this talk, various antenna designs for energy harvesting applications is given.

From frequency selective surfaces (FSS) to electromagnetic band-gap (EBG) ground planes, from impedance boundaries to Huygens metasurfaces, novel electromagnetic surfaces have been emerging in both microwaves and optics. Many intriguing phenomena occur on these surfaces, and novel devices and applications have been proposed accordingly, which have created an exciting paradigm in electromagnetics, so called “surface electromagnetics”. This seminar will review the development of electromagnetic surfaces, as well as the state-of-the art concepts and designs. Detailed presentations will be provided on their unique electromagnetic features. Furthermore, a wealth of practical examples will be presented to illustrate promising applications of the surface electromagnetics in microwaves and optics.

Metamaterials (MTMs) were introduced to the EM world by Veselago back in the 60’s, who wrote a seminal paper in which he argued that materials with DNG (double-negative) characteristics, whose andare both negative, would exhibit exotic properties such as super-resolution, when used in devices such as lenses. Since then other interesting properties of MTMs have been identified, and their applications to cloaking, performance enhancement of small antennas, and related areas, have been proposed. More recently, there has been considerable interest in the topic of Metasurfaces (MTSs), as opposed to volume-type materials, that have been employed to control the propagation of EM waves with applications to communication antennas.
Despite a flood of publications on MTMs and related topics—literally thousands during the last 10 years—the number of real-world applications in which MTMs and MTSs have been utilized have been rather limited. The primary reason for this is the lack of availability of the materials needed to fabricate devices such as those that reduce the size of antennas without compromising their performance in terms of gain, bandwidth, and efficiency, for instance, or shrouds (cloaks) that suppress the electromagnetic scattering from radar targets, to name just a few. A similar situation arises when one attempts to design an antenna, or a similar device, using Transformation Optics (TO), a relatively new concept which was recently introduced by Pendry, among others. In this approach, the transformation of one coordinate system to another is used to modify the geometry of an antenna, without altering its performance, by replacing the original material properties with new ones that can be rigorously determined by applying the principles of TO to Maxwell’s equations. An example of such a device is a flat Luneburg lens which is derived by transforming the conventional spherical Luneburg lens, to render it easier to fabricate. The caveat is that the TO algorithm calls for andmaterials that are not available naturally, e.g., MTMs. The same is also true for a wide variety of other devices, such as flat GRIN (graded index) lenses and Reflectarrays (RAs), which require materials that are unavailable off-the-shelf and, hence, must be synthesized artificially.
In light of this back ground on MTMs, this presentation will focus on the topic of artificial synthesis of materials with real-world applications in mind. We will review the different strategies that have been proposed, will identify the ones that have been successfully implemented, provide
several practical examples of the same, and go on to discuss the challenges that still need to be met--not the least of which is cost-effective fabrication--to satisfy the ever-increasing demands posed by emerging technologies, such as IoT and 5G.
The topic of Additive Manufacturing for low-cost fabrication of MTMs also being pursued a by several grouiips around the world will be covered, and some issues particularly related to this topic will be examined.

Increasing demand for faster information transport has driven a tremendous progress towards smaller, and faster. Plasmonic interconnects are superior to the electronic ones by virtue of their large operational bandwidth, and huge data transmission capability. An unprecedented synergy could be reached by integrating photonic, plasmonic and electronic devices into the same platform with fully exploiting the advantages of photonics, plasmonics and nanoelectronics technologies.
This presentation will touch on the CMOS based plasmonic devices and interconnects for on-chip nanoscale optical data transmission. To optically transmit data between electronic devices, we need to develop a number of plasmonic devices, such as plasmonic sources, modulators, waveguides, switches, filters and detectors. The studies show that the optical power can be efficiently coupled from the plasmonic waveguide to the plasmonic detector. The extremely small active area in the detector results sub-picosecond transit-time and atto-Farad internal capacitance, implying a potential THz-bandwidth.

From frequency selective surfaces (FSS) to electromagnetic band-gap (EBG) ground planes, from impedance boundaries to Huygens metasurfaces, novel electromagnetic surfaces have been emerging in both microwaves and optics. Many intriguing phenomena occur on these surfaces, and novel devices and applications have been proposed accordingly, which have created an exciting paradigm in electromagnetics, so called “surface electromagnetics”. This seminar will review the development of electromagnetic surfaces, as well as the state-of-the art concepts and designs. Detailed presentations will be provided on their unique electromagnetic features. Furthermore, a wealth of practical examples will be presented to illustrate promising applications of the surface electromagnetics in microwaves and optics.

RF-sensors and Radar systems found their way into civil and industrial applications decades ago. Since then, they reliably measure distances, velocities, and filling levels etc. contact free and with great accuracy. Lately, current trends and technological achievements pushed operating frequencies up to the millimeter wave range, which allows for the determination of various additional physical quantities. Consequently, these novel sensors can be utilized in numerous areas of process industry, civil protection, and daily life. Therefore, their main purpose will be the determination and investigation of environmental parameters that allow for the supervision of crucial system parameters and the interpretation of complex processes. The talk will give an overview on diverse RF‐sensors for different applications, which were explored at the Ruhr‐University Bochum within recent years. The presented sensor applications include: humanitarian demining, mmWave imaging, contact‐free gas sensing, plasma diagnostics as well as dust and particle determination for process industry and natural hazard protection. Next to the introduction of the numerous areas of application, the different sensor designs will be explained and their field applicability verified. Moreover, opportunities regarding student exchanges between Ruhr-University and NUS will be introduced and discussed.

Millimeter-wave antennas and arrays used for future wireless communications have attracted increasing attention. This talk will introduce a new type of wideband antennas designated as the aperture-coupled magneto-electric (ME) dipoles for high frequency applications. By applying the aperture coupling as the excitation scheme, the ME-dipole antennas with various polarizations can be realized easily. All the designs have good characteristics including wide bandwidth, high radiation efficiency, symmetrical radiation patterns, low back radiation, and low cross polarizations. Based on the proposed antenna elements, a high-gain wideband circularly polarized ME-dipole array and two multi-beam ME-dipole arrays with different polarizations are investigated. Additionally, the arrays can be fabricated by using low-cost printed circuit board (PCB) facilities.

The talk will focus on enhanced light-latter interactions on nanostructured surfaces. Light-matter interactions can be controlled by manipulating the electric and magnetic responses of a material. Specifically, uncooled detection of mid-IR photons, skin-like displays, neural sensing and infrared concealing/camouflage will be highlighted. The newly developed printing techniques enable large area printing of such nanostructured surfaces for low cost manufacturing.

Microwave assisted chemical reactions have attracted interests because of their benefits for enhancement of reaction rates. However, the problems, such as hot spots and thermal runaway, limit the application of microwaves in the chemical industry. This presentation introduces the dielectric polarization in polar-molecule reactions in the liquid phase theoretically. On the basis of the modified Smoluchowski equation, the polarization can be described with the rotational diffusion vector and component concentration vector. Then, the new equation of electromagnetic wave propagation in a unimolecular reaction is derived. Moreover, a 1D mold is used to predict some new and interesting propagation characteristics.

The speaker will report on a hypoallergenic electronic sensor that can be worn on the skin continuously for a week without discomfort. It is so light and thin that users forget they even have it on. The elastic electrode constructed of breathable nanoscale meshes holds promise for the development of noninvasive e-skin devices that can monitor a person’s health continuously over a long period [1].
[1] Akihito Miyamoto, et al., Nature Nanotechnology (2017); doi:10.1038/nnano.2017.125.

Fibered laminates involving in each of their layers glass or graphite fibers embedded in periodic fashion within a given material matrix suffer from damages at production and in usage, and electromagnetic testing is a way to get proper information on them. This requires reliable computational modeling of undamaged and damaged structures, to understand their behavior and acquire synthetic data to input into imaging algorithms, properly developed as well, a first step before controlled laboratory studies and, upon proof of concept, real world. Tools, both of modeling and imaging, will be summarized in the exposé, and a host of examples given, from low frequency to resonance, as encountered in practice as a function of the structures to be tackled. Parallels with photonics will be drawn. Guidelines for further exploration in the realm of non-destructive testing and evaluation will also be provided.

Progress in the Terahertz region of the spectrum is now such that real engineering applications can be discussed. A large bandwidth is available, unlike X-rays, etc. it is safe for humans and non-destructive. However the radiation is absorbed by water and so not useful for long distance transmission. It may be approached as extending the r.f. spectrum upwards or extending the optical spectrum downwards. 0.3 to 3 THz is also called the submillimetre waveband, and above that is called ‘super THz’. CMOS devices are moving up into the THz range, and applications being found in non-destructive testing and in weapons and security. It is possible to use FET techniques to generate THz frequencies or else two optical frequencies may be mixed in a non-linearity and the THz difference frequency extracted.

Towards the end of the Moore's law and device scaling limit, many emerging devices are under extensive investigation for their potential to extend the benefit from technology scaling. To evaluate the advantages of these devices in different applications, a compact model for each device is necessary to allow computer simulation before the physical hardware is implemented. In this talk, aiming to two devices in recent research hotspots, i.e. GaN HEMT and JL FinFET, we present the latest research progress on developing surface potential based models in the traditional approach. However, developing physical based compact models is expensive and very time-consuming. It is thus demanded that the compact model can be generated automatically from measured or T-CAD simulation data. In the end, we will introduce one modeling methodology for generating compact, non-physical based models for emerging devices in which machine learning technique is applied.

In this seminar, an overview of design of Pulse Power Technology (PPT) and High Power Microwave (HPM) sources will be introduced. In Part 1 of the talk, the design and assembly of a compact Marx generator for the generation of a high power pulse are presented. The design of peaking switch to enhance the rise time of the pulse is also discussed.  In Part 2 of the talk, the design and analysis of high power radiators such as Impulse Radiating antenna (IRA) and Half TEM horn and their performance characteristics will be discussed. The seminar will also highlight the software modeling of Compact Marx generator Impulse radiating antenna. The best numerical techniques to solve high frequency EM problem such as FIT, MoM for design of UWB antenna and suitable software will be discussed. This seminar is useful for those who have interest in applied electromagnetics, high power microwave applications.

The talk will give a historical review as well as outlook of the popular processes to implement antennas for millimeter-wave (mmWave) and THz applications. Investigations go into the aspects of design, process, and packaging. Great cost reduction is achieved when the LTCC process is replaced by the LCP, while equal performance remains. Methods to overcome the intrinsic drawbacks of both LTCC and LCP materials are discussed. The 3D printing technology is eye-catching nowadays, while most focuses are on the non-metallic 3D printing technique. Here, we, for the first time, manage with successful demonstration to implement antennas by metallic 3D printing technology up to the H-band (220-325 GHz). Information will be given on the design precautions and process-related surface roughness of the 3D printed antennas. 

The internet-of-things (IoT) promises the connection of machines, sensors and other objects to the internet so that they can become part of our information network. The IoT is predicted to bring a revolution in the way we monitor our health, environment and infrastructure and allow enhancements in efficiency, performance and services. There are many challenges in enabling this revolution and in this talk we consider the issue of the power source for the devices or things in IoT. In many instances the devices will be portable and wireless and need battery power which has a finite life and therefore needs to be replenished periodically. To overcome this challenge, we describe approaches to harvest ambient RF energy using multiple antennas and novel matching techniques. A continuous power source for sensors and devices for IoT can be found using ambient RF energy radiated from Wifi, cellular and other wireless access points and basestations. While the power collected is low, combining ambient energy harvesting with the latest low power technologies and electronics can allow the development of standalone wireless devices that do not need batteries. One of the key elements in the approach presented is using multiple antennas to collect ambient energy. By combining the individual antenna elements after rectification and at DC, high gain, wide beam width rectifying antennas can be formed which are able to collect ambient RF energy from a broad range of directions, increasing the collection efficiency of the harvesting. In addition by using ladder matching networks instead of single point matching networks more power can be collected in compact multiple antenna configurations while still providing good bandwidth.

This talk presents two recent developments for the enhancement of the capability and performance of computational electromagnetics methods. The first development is related to the finite element analysis of highly complicated materials that involve fine geometrical features. The traditional finite element analysis would require a finite element mesh that is conformal to all fine geometrical details. Generating such a mesh is highly challenging and very time-consuming for objects such as microvascular composite materials. It is also a bottleneck in the automatic optimization of electromagnetic devices where the shapes of the devices have to be modified in each iteration. To overcome this problem, an interface-enriched generalized finite element method (IGFEM) is developed, which requires only a background mesh without resolving fine geometrical details. To model the effects of these details, the IGFEM introduces a set of interface basis functions to enrich the basis set on the background mesh. The method is shown to be robust and accurate. The second development is aimed at electromagnetic modeling of highly complex objects, which consist of different parts with different material properties. In this so-called multi-solver scheme, the entire computational domain is first decomposed into multiple non-overlapping subdomains. Each subdomain is then modeled with the most suited method, such as the finite element or moment method. The equations in the subdomains are then coupled into a multi-solver system through either the Robin transmission condition or the combined-field integral equation applied at the subdomain interfaces. Finally, the combined system is solved iteratively with the application of a preconditioner based on an absorbing boundary condition and the multilevel fast multipole algorithm.

The problem of placing one or more user-specified antennas on a complex platform, e.g., the chassis of a mobile device, the topside of a naval vessel, or a UAV, is often encountered in real-world scenarios. Recently, the Characteristic Mode Analysis (CMA), has been recognized as a powerful and systematic approach to potentially handle this challenging problem.
This talk will begin by reviewing the existing literature on CMA, and then go on to discuss the problems of excitation of Characteristic modes on a complex platform, as well as the realization of desired radiation patterns using the Characteristic mode analysis (CMA) and related techniques. Next, the problem of placing user-specified antennas on a complex platform to realize a desired pattern will be discussed by using a new approach based on the use of Characteristic Basis Function (CBF). Illustrative example dealing with some representative real-world problems will be included in the presentation.

GaN is one of the third-generation semiconductor materials, which has move from research hotspot towards key products technology in recent years. Due to its unique properties - high breakdown voltage, high frequency operation and high power density, it is excellent for the design of wideband, high-efficiency, high-power RF, microwave and THz circuits. 2D materials such as Black Phosphorus (BP) are another new up-and-coming main research focus from material towards devices and circuits. Most recently the quantum chip moves to silicon based and brain-computing chip research open another wave in the ECE socity. In this talk, LS GaN modeling cum PA design with emphasis on traping effects will be presented. the most recently early staege BP device and modeling effort, as well as quantom chip and brian chip research activities wiill be shared.

The U.S. Defense Advanced Research Projects Agency (DARPA) has had a remarkable history of successful innovation over its 56-year history. Much of its success can be attributed to a rigorous programme development process initially used by Dr. George Heilmeier, DARPA Director 1975-77 and retained by DARPA to this day. The process begins with answering nine difficult questions starting with “What problem are you trying to solve?” In practice, DARPA Program Managers often spend 6-12 months answering these questions. Prof Polla who has spent 11 years at DARPA and its sister agency IARPA will share the DARPA Innovation Model and its applicability in the Singapore environment. A*STAR has now used the model in defining two major new research initiatives and its management principles in the Pharos Programme. Prof Polla will describe its application in several emerging thematic programme areas of interest under the RIE2020 AME Domain.

Metal surfaces are able to support electromagnetic (EM) resonances usually called surface plasmons. However, the fact that they can sustain these confined modes only at visible wavelengths prevents the transferring of plasmonic capabilities to lower frequency domains. In this talk we will show how structured metal surfaces can mimic plasmonic abilities (such as high confinement and amplification) at low frequency ranges of the EM spectrum, as they support spoof surface plasmon modes even when the metal behaves as a perfect conductor. Importantly, as a difference with their optical counterpart, spoof surface plasmons have a purely geometric origin, allowing more flexible designs.