Abstract:
In this thesis, a most recent technique for designing low profile frequency selective
surface (FSS) with second-order band-pass response is utilized. The FSS designed using
this technique utilizes non-resonant sub-wavelength constituting unit cells with unit cell
dimensions and periodicities on the order of 0.15λ0. It is demonstrated that using this
technique, second-order FSS with an overall thickness of approximately λ0/30 can be
designed. This thickness is considerably smaller than the thickness of second order FSS
designed using traditional techniques (i.e. approximately λ0/4) and could be particularly
useful at lower frequencies with long wavelengths. Designing of FSS with frequency
response that is insensitive to angles of incidence and polarizations is a challenging job. In
this technique of designing FSS, combination of small thickness and miniaturized unit cell
dimensions ensures that the frequency response of the structure does not significantly vary
as a function of the angle of incidence. To facilitate the design of this structure, an
equivalent circuit based synthesis method is also presented in this thesis. Different bandpass
FSSs operating at X and Ku bands were designed and simulated. Out of these two
designs FSS operating at X-band was fabricated and tested. A free space measurement
setup is used to thoroughly characterize the frequency response of this prototype for both
the TE and TM polarizations and various angles of incidence. By the comparison of
simulated and measured results, it is observed that there exists a high insertion loss in the
measured result, and in the measured result the desired frequency band is also shifted
backward. This high insertion loss and band shifting in the measured result are due to the
absence of required measurement setup and variations in the dielectric constant of FR4
substrate. A detailed design procedure, principles of operation and simulated and
measured results are presented and discussed in this thesis report.
