gopinath

This group is using MSI resources for three projects:

• RF Coil Design for Magnetic Resonance Imaging: The group is studying metamaterials and metasurfaces with the end goal of using them for the radio-frequency (RF) coils used for Magnetic Resonance Imaging (MRI). The coils provide the RF excitation for the protons at the location being imaged in the presence of the DC magnetic field and the DC field from the gradient coils. These researchers are investigating innovative coil designs based on metamaterial transmission lines using Ansys’s HFSS CAD program.
  • Metamaterials are an artificial class of materials which have negative permeability and permittivity, resulting in left hand propagation of electromagnetic waves. Metamaterial transmission lines have both the normal transmission line behavior, where both the phase and group velocities are positive, and behavior where the phase and group velocities in opposite directions. There are sections of the line which have fast wave solutions (phase velocity is greater than the velocity of light), which should radiate very efficiently, but experimentally these effects are not seen due to parasitics. This group is investigating using these lines for MRI RF Coils with some very good results and some poor results. They are looking at applications of these lines for reduced coupling.
  • Metasurfaces are planar metamaterials where a phase shift occurs when an electromagnetic wave of a specific frequency passes through. Thus it becomes possible to have printed antennas on very thin substrates with a metasurface between the antenna and the ground plane to simulate the quarter-wave substrate, so that the image adds to the far field radiation pattern. Initial results have shown have very exciting new results in simulations and further investigations are being carried out.
• Simulations for Antenna Phased Array Systems: The group is investigating an innovative array system. Instead of the phases of the array elements being altered, the amplitude is varied, which gives rise to scanning. They have the advantage that phase shifters are not required; they are used in numerous applications. Simulations on these will be performed before they are built for test purposes. Initial simulations show excellent performance and further investigations are in progress.