Seminar: Breaking conventional bounds in electrically small antenna systems using direct antenna modulation
Speaker: Kurt Schab, NC State University
Title: Breaking conventional bounds in electrically small antenna systems using direct antenna modulation
When: Thursday 21/9 15.15-16
As an antenna becomes electrically small, its performance rapidly decays. This limitation has been a topic of heavy research and debate in the antennas and propagation community over the last 70+ years. This is because the bounded bandwidth of electrically small antennas can be a key limiting factor within a communications link as it directly limits the bandwidth of signals which can be transmitted or received. This research studies a new class of transmitting antenna systems with properties outside the normal assumptions used in deriving the bounds on electrically small antennas. Such systems utilize "direct antenna modulation" (DAM) wherein an antenna or its matching network is made non-linear or time-varying in order to enable the transmission of extremely high-bandwidth, high-data rate signals.
Our work has three main objectives in analyzing, refining, and realizing direct antenna modulation techniques in novel ways. First, we study the theoretical justification for simple, heuristic DAM schemes through comparison with derived optimal (yet non-realizable) solutions. Second, we exploit certain nuances of a popular computational electromagnetics technique (Method of Moments) to facilitate the simulation and evaluation of general DAM systems in a much faster and more efficient manner than was previously possible. These computational advances not only aid in the study of new and optimized DAM schemes, but also add physical understanding to phenomena previously lacking quantitative explanation. Finally, a key goal of this research is to validate the functionality of a DAM transmitter in a realized communication link. Promising experimental results show that conventional bounds are easily broken using direct antenna modulation, indicating this technology has the potential to be a major disruption to the established ways of using electrically small antennas.
This presentation will briefly cover background on direct antenna modulation, key results from our research, and future directions for the field.
Kurt Schab is a post-doctoral research fellow at North Carolina State University. He earned a B.S. in Electrical Engineering and a B.S. in Physics from Portland State University in 2011. He completed his M.S. and Ph.D. in Electrical Engineering in 2013 and 2016, respectively, from the University of Illinois at Urbana-Champaign. His area of research is applied electromagnetics, with particular focus on time-varying antenna systems and the intersection of numerical methods with antenna theory.
Seminar by Professor Yasuyuki Miyamoto “Tunnel FET for low power / high speed application”
Speaker: Professor Yasuyuki Miyamoto, Department of Electrical and Electronics Engineering, Tokyo Institute of Technology
When: september 15, 2017 at 10.15’
Short bio: Prof. Miyamoto has a long experience in transistor processing and characterization and he is very active in the Japanese as well as the international conference organizations.
Tunnel FETs with a sub-60-mV/dec subthreshold slope (SS) have been proposed as transistors for CMOS logic circuits. Since the high-speed operation of CMOS circuits requires a high drive current, introduction of heterojunctions in the tunnel FETs is an attractive option.
As high electron mobility provided by InGaAs channels can result in a high current density, we have studied the InGaAs/GaAsSb type-II heterojunction double-gate tunnel FETs. To obtain high current density, heavily doping in source is essential for low access resisitance. On the other hand, lower drain doping is effective to obtain low off-current as the minimum current of tunnel FETs is determined by the ambipolar behavior. Moreover, the reduction of the channel length of MOSFETs is attarctibe becuase it decreases the gate capacitance and lowers the dynamic power consumption. However, the direct source-to-drain tunneling increases in the case of short channels and it may be the dominant tunneling mechanism of off-state currents. Thus,we classified the tunneling current based on numerical simulations.
Present expermental status of InGaAs/GaAsSb type-II heterojunction double-gate tunnel FETs by top-down process is also explained..
For further scaling,body width of semiconductor is one of the limitation. Thus 2D-semiconductor, such as transition metal dichalcogenides (TMDs) is promisinng materials. Among the TMD materials, HfS2 has a high electron affinity so that type-II heterojunction can be formed with other TMD materials. Thus we experimentally demonstrated a vertical HfS2/MoS2 van der Waals (vdW) heterostructure transistor.
2017-06-19 Early summer IEEE CAMAD event hosted by EIT
Date: June 19-21, 2017
Place: E:A, E:3139
More info on the event with detailed program can be found here.