Investigation of the hexagonal lattice based reflectarray antennas

In this thesis, the hexagonal lattice based reflectarrays are investigated in terms of antenna performance and beam steering capability by comparing them with their square lattice based reflectarray counterpart. In addition, novel unit cell element designs are presented having improved reflection phase range and reflection loss. First of all, the phi-shaped unit cell element type is examined and re-designed to have an operating frequency of 8.23 GHz. The operating principle of the phi-shaped element is studied and novel unit cell elements are designed by using the experience gained from the examination of phi-shaped element. Then, the hexagonal and square lattice based reflectarrays are designed and fabricated by using 0.52λ inter-element spacing at 8.23 GHz to avoid grating lobes. Simulation and measurement results are compared and not any significant difference is observed between the antenna performances of both placement topology types. Moreover, the beam steering capability of the hexagonal lattice based reflectarrays are investigated at 8.23 GHz by designing a separate reflectarray for each scan angle. The square and hexagonal lattice based reflectarrays with inter-element spacing of 0.6λ are designed, fabricated, and measured to examine the effect of placement topology on beam steering capabilities. It is observed that, the measurement results of the all fabricated reflectarray antennas are in very good agreement with the simulation results. The comparison of the square and hexagonal topologies show that the beam steering capability can be improved by 50% for 0.6λ inter-element spacing by using a hexagonal topology.