Dual-band beam scanning reflectarrays and novel wideband and polarization diversified planar antennas

摘要

The reflectarray antenna has been considered as a suitable candidate to replace thetraditional parabolic reflectors because of its high-gain and low-profile features. Beamscanning capability and multi-band operation are the current trends of the reflectarraydesign. It is desired to implement these functionalities with simple and effectivetechniques. Narrow bandwidth is the main issue which restricts the applications of themicrostrip antennas. New microstrip slot antennas and polarization diversified planarantennas are introduced as the solutions to the issue of narrow bandwidth in thisdissertation.A dual-band beam scanning reflectarray has been developed. It is the first offset-fedreflectarray that has been ever practically developed to emulate a cylindrical/parabolictype of reflector. Unlike other beam scanning reflectarrays which integrate phase tuningdevices into the reflectarray elements and control the reflection phase, the beamscanning capability of this reflectarray is provided by its feed array. This methodsignificantly reduces the complexity of the design of the beam scanning reflectarray. A new dual-band reflectarray configuration is also developed to eliminate the possible toplayer blocking effects in the dual-layer reflectarray configuration. Perforated patchesloaded with slots on the ground plane and rectangular patches loaded with slots on thepatches are adopted as the low and high frequency bands, respectively. It is guaranteedthat no physical contact between any two elements will occur.The bandwidth of the conventional microstrip antenna is small. A new widebandcircularly polarized microstrip slot antenna is introduced in this dissertation. Very wide3-dB axial ratio bandwidth is observed for the proposed antenna. The antennas areassembled in triangularly arranged array with sequential rotation feed technique.Polarization polarity is an alternative solution to the narrow bandwidth. A reconfigurablecircularly polarized microstrip antenna is proposed. The antenna has both right-hand andleft-hand circular polarizations which are controlled by two piezoelectric transducers. Inaddition, a dual-band dual-linearly-polarized planar array is designed based on theconcepts of polarization diversity and multi-band operation.The research presented in this dissertation suggests useful techniques forreflectarrays and novel antenna designs. The results should have many applications forthe modern wireless communication and radar systems.