19-12-2012, 03:14 PM
Carbon Nanotubes for Small Antennas
Carbon Nanotubes.ppt (Size: 3.06 MB / Downloads: 519)
What is a Carbon Nanotube?
Single Wall Carbon Nanotube (SWNT)
Graphite sheet seamlessly wrapped to form a cylinder typically 1 nm in diameter
Properties
Higher electrical current density and thermal conductivity than any metals
BALLISTIC ELECTRON TRANSPORT – i.e., no backscattering of electrons,which is the a source of electrical resistance
McEuen (Cornell) measuring conduction vs. length of SWNT show ballistic length limited to ~1.2 microns
Mechanically stronger than most if not all other materials
ApplicationCNTs for Small Antenna Matching Networks
Concept - minimize resistive loss in tuning networks
Benefit from high conductivity and high current density of CNT
Application – Enable efficient electrically very short antennas
Resistance of regular inductor is much higher than antenna radiation resistance
Smaller batteries required for sensors or longer battery life
Challenges
Ballistic transport length
Current density inversely proportional to CNT length
Connection to RF circuitry
Bundling and associated behavior
Functionalization to Enhance Conduction Property of CNT’s
Objective:
Increase (>1.2 um) ballistic (lossless) transport length for SWCNTs
Chemically bond ligands to specific locations on sidewalls of CNT to modify low energy phonon spectrum
Analyze applicability to proposed RF applications (e.g., bending for toroid, helical inductor)
First Principles Quantum Mechanics – Professor Marzari of MIT
Efficient calculation of CNT band/ligand structure
Switch Design – Work Remaining
Complete Device Demonstration Steps with final device
Steps have been demonstrated with interim unit
RF measurements with final device
Develop circuit model for our switch design
Insert circuit model into antenna model to obtain antenna pattern and efficiency