Session Chair: Armand Soldera, University of Sherbrooke Session Chair: Sung-Soo Kim, Chungbuk National University
1:30pm - 2:00pm Invited
Ferrite Materials and Components in Electromagnetic Compatibility
Marina Y. KOLEDINTSEVA1, Konstantin N. ROZANOV2
1Oracle, United States; 2Institute for Theoretical and Applied Electromagnetics, Russian Federation
Soft ferrites and composites on their basis are important materials for solving various EMC-related problems. There are three major areas where soft ferrites are used. These are low signal level applications, power applications, and electromagnetic interference (EMI) noise suppression. Ferrites can be used in all kinds of shields to isolate a conductor, a component, or a circuit from an environment of radiated or conducted electromagnetic emissions; or to prevent electromagnetic emissions from leaking out of electronic units into surrounding space. Ferrites can be used to design low-pass filters which exhibit reactance and low loss at low frequencies, while are dissipative at higher frequencies. The present-day high level of digital electronics integration causes new EMI challenges. Novel silicon devices embed noise problems where they cannot be easily resolved – in the chip itself, bringing the problem to the PCB level. Therefore, the third, and the most common use of ferrites, is in PCB-level circuitry, or as standalone parts on component leads.
Depending on specific application, different types of ferrites are required. In this presentation, the main types of ferrite materials and components are overviewed, as well as their main electromagnetic characteristics for EMI suppression. Special attention is paid to ferrite materials characterization, including methods of measuring their electromagnetic parameters and modeling in systems, physics-based limits of their applicability, and as well as perspectives of overcoming these limits. General guidelines how to choose a proper ferrite component and material in electronics designs are given. Such types of ferrite components as ferrite beads; cable cores and chokes for common-mode filters; composite noise suppression sheet materials for near-field region; microwave ferrite-containing electromagnetic wave absorbers; and ferrites for some other EMC-related applications, e.g., wireless inductive charging, near-field communication and RFID, will be overviewed.
2:00pm - 2:30pm Invited
Metasurfaces for Electromagnetic Absorption
Sergei A. TRETYAKOV
Aalto University, Finland
We present an overview of thin engineered composite layers (metasurfaces) which operate as perfectly absorbing layers. Possible topologies of perfect metasurface absorbers are classified based on their operational principles. For most important classes, we present examples of particular realizations, discussing the advantages and disadvantages of various structures.
2:30pm - 2:45pm Oral
Polymer-derived Carbon Materials and Their Applications in Electrochemical Field
Junhua KONG1, Chaobin HE1, Xu LI1, Xuehong LU2
1Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), Singapore; 2Nanyang Technological University, Singapore
As one of the most popular and useful category in material science and engineering, carbonaceous material possesses unique electrical, thermal and mechanical properties, and has found extensive uses in rich variety of areas. Carbon can be produced in various methods, and depending on the preparing routes as well as the parameters that used, the morphologies and microstructures of the carbon differ from one another significantly. This enables precise control of the carbon properties for specific applications. As what is well known, polymers can be carbon precursors, and a simple annealing process in inert environment converts polymers into carbonaceous ones straightforwardly. Unique work about carbonization of polymers, combing with other specific morphology-controlled techniques, has been done in our lab. The derived carbon was then used in electrochemical areas. The above work, including nanofibrous polyacrylonitrile-derived carbon and polydopamine-derived carbon, as well as their electrochemical applications, will be introduced in this talk. This offers an insight to the carbon from carbonization of polymers, and facilitate their uses in other potential areas by interested researchers.
2:45pm - 3:00pm Oral
Quality Criteria for Radar Absorbers
Konstantin N. ROZANOV1, Marina Y. KOLEDINTSEVA2
1Institute for Theoretical and Applied Electromagnetics, Russian Federation; 2Electromagnetic Compatibility Design Engineering, United States
The presentation discusses quality criteria for radar absorbing performance. Most published reports on microwave properties of various composites are refer to radar absorbers as possible applications. The conventional approach is to measure the effective permittivity and permeability of a composite with certain concentrations of inclusions; calculate the frequency dependence of reflection coefficient of the composite slab backed by a metal substrate for the normal incidence of electromagnetic wave; and choose the slab thickness to minimize the reflection coefficient at a frequency of interest. The obtained deep minimum, typically of −30, −40 dB, or even −60 dB is considered as a proof for “a good absorbing ability” of the inclusions comprising the composite.
Simple analytical approximations are suggested for the reflection coefficient of radar absorbers. It is shown in the presentation that the problem of radar absorbing performance is not reduced to obtaining the absorbing ability, but is a problem of matching. Therefore, the depth of reflection minimum is not a suitable measure for the characterization of radar absorbers. To describe the quality of an absorber, other quality criteria are needed.
One of possible criteria is a characterization of the operating bandwidth. The width of the operating frequency range cannot serve for bandwidth quantification. Indeed, if the bandwidth is 2 GHz, the operating range may be 0.1 to 2.1 GHz or 18 to 20 GHz, which is a huge difference from the standpoint of designing a radar absorber. A correct approach to define quality of absorbers should use either the fractional bandwidth or the wavelength operating range. The use of one of these is of importance depending on if the absorber thickness is of prime priority or not.
An alternative characterization may be related to the angular absorbing performance, although no numerical criterion has been suggested in the literature so far.