The growing demands of wireless communications stipulate the redesign of systems to cater to different needs over a very broad spectrum. These systems require compact, multifunctional and cost effective antennas and subsystems operating at different frequencies ranging from microwaves to terahertz (THz). The cost of having different antennas for different operations can be reduced by utilizing a single antenna having multifunctional capabilities. The first half of the talk proposes novel design concepts for compact multifunctional coplanar waveguide (CPW)-fed ultra-wideband (UWB) printed antennas. The talk will also cover recent requirements in designing MIMO antennas where issues like mutual coupling and cross-talk need to be mitigated. We will summarize recent efforts of the electromagnetic community on printed antennas with multifunctional characteristics to meet requirements for software defined radio and cognitive radio applications.
The second half of the talk will deal with THz antennas and associated system components. The THz frequency domain is a relatively unexplored region where applications like THz imaging have drawn great interest due to its higher resolution and non-ionizing effect. This is potentially less harmful to the human body and can be used for nondestructive evaluation, and medical and security applications. Wireless power transfer (WPT) using rectennas at THz frequencies is also touted as a potential field of future research. Since, in the THz regime thickness of conducting walls of the waveguide is comparable to the skin depth (δ), practical issues like roughness profile of the conducting walls, intrinsic process-related fabrication tolerances, etc., impose greater constraints to the system designers than at microwave and lower millimeter (mm) wave. Basic models will be highlighted including the Hammerstad and Bekkadal model and the Hurray model, which help in mapping the surface roughness profiles of waveguide based THz components into modified conductivity for improved practical realization. Several THz antennas having different structures have been presented recently in open literature. This talk will discuss such designs along with the limitations and constraints of THz antennas, in general. This webinar will also provide brief insight into the fabrication and characterization requirements of photoconductive antennas (PCAs) and the limitations, highlighting a few recent designs and successful realization. Several practical aspects for realizing PCAs such as, (i) the choice of the substrate with desired carrier mobility and minority carrier lifetime, (ii) photoconductive gap, (iii) position and orientation of the bias electrode and iv) gain enhancement, will be highlighted.