Frequency selective components for microwave and terahertz applications
Vegesna, Subash V.
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This dissertation presents novel design techniques to realize frequency selective components at RF/microwave and terahertz (THz) frequencies with improved frequency response characteristics. The improvements in the transmission frequency response characteristics for the proposed components include better selectivity, improved roll-off factor, compactness and suppression of spurious resonances. RF/microwave filters are used in almost all types of microwave communication circuits, multi-band wireless devices, radar systems and measurement systems. Filters play an important role in almost every electronic system which requires various types of filters to be implemented to allow a particular range of frequencies to pass and to reject other frequencies. Frequency selective surfaces (FSSs) are widely used in radar and satellite communications for filtering applications and have widespread use as filters, radomes, polarizers, beam splitters and sensors. Therefore, to address this huge demand for realizing frequency selective components with improved transmission characteristics, various design configurations at microwave and THz frequencies are proposed. This dissertation can be categorized into two sections. In the first section, design topologies to realize compact microwave filters such as (i) stacked two-layer bandpass filters, (ii) dual-band bandpass filters (iii) dual-band bandstop filters and finally (iv) compact microstrip bandpass filter using interdigitated fingers are proposed. In the second section, novel design techniques to realize frequency selective surfaces at THz frequencies such as (i) two-layer cascaded FSS with improved transmission characteristics (ii) reconfigurable single- to dual-polarized FSS and (iii) tunable bandpass FSS structures at THz frequencies are proposed. All simulations of the filters at both microwave and terahertz frequencies were performed using commercially available EM software (Ansys HFSS and Designer). Prototypes were fabricated and tested to validate the simulations. Excellent agreement between simulation and measurement results were obtained for all proposed structures.