Radiation pattern reconfigurable single-arm spiral antenna
Pattern reconfigurable antennas have aroused intensive research recently because of their critical role in wireless communication and military applications. Phased arrays offer best beam steering ability but they are balky and costly built. Alternatively, cost effective solutions can be achieved by introducing switch circuitry into simpler antenna structures like ring antennas, slot antennas, and spiral antennas. This thesis focuses on single arm rectangular spiral antennas capable to steer the beam by switches attached on the spiral. Two novel beam steering spiral antennas operating at 3.3 GHz with wide beam coverage have been proposed. Simulation was conducted using Ansys HFSS. RF-MEMS varactors or PIN diodes are used as switches. Simulation results show wider azimuth plane coverage than existed designs because of the added bridges and extra switches. The location of the bridges and PIN diodes are determined by parametric sweep simulation process which has been detailed. In order to validate the simulation results, two antennas are fabricated using Rogers 4350 substrate and PIN diodes. They are center fed by SMA connectors with inner pin connecting the starting point of the spiral. Up to three DC biasing signals of both positive and negative voltages are required to achieve various cases for the switches. Since DC supplies are directly connected with spiral arm, biasing line, pad, and quarter wavelength stubs are needed to open circuit RF signals. Although the geometry and locations of them have been optimized, analysis indicates that these elements for biasing purposes generate errors and disagreements from simulation results. The wire connecting DC supply and range errors lead to discrepancy between simulation and measurement. Simulation and measured results for reflection coefficient, radiation pattern (both RHCP and LHCP), gain, and axial ratio are compared. Measurement methods by spinning source, two-orthogonal-cut, and cavity backed circular spiral antennas are detailed. In addition, a thorough review of ...
