Design of Frequency and Radiation Pattern Reconfigurable Antennas

Book excerpt: Reconfigurable antennas have been the focus of antenna engineers looking for compact size while enhancing the performance and capabilities of their antenna. Whether it's selecting different frequency ranges, switching radiation patterns, or changing the polarization of the antenna, reconfigurable antennas are a potential solution for an ever-evolving industry. In this project, a frequency reconfigurable bow-tie antenna (called the Butterfly), a radiation pattern reconfigurable circular patch antenna (called the Sunflower), and a frequency/radiation pattern reconfigurable bow-tie antenna (called the Hermes), were designed and simulated using Altair FEKO electromagnetic simulation tool. The Butterfly and Sunflower antennas were fabricated and tested, while the Hermes antenna was simulated only. Each antenna has multiple states (frequency or radiation) and is controlled by RF switches which could be implemented with PIN diodes (ideal switches were assumed for this project). The developed reconfigurable antennas are referenced to x previous work but evolved through re-design to include better manufacturing, lower cost, better performance, or new capabilities. The Butterfly antenna has 3-states with simulated operational frequency states: 1.76 GHz, 2.09 GHz, and 2.56 GHz, and measured operational frequency states: 1.742 GHz, 1.903 GHz, and 2.47 GHz. The difference between simulation and measured results are 3.52%, 8.95%, and 1.023%, respectively. The Sunflower antenna can direct the beam in eight different azimuth directions in steps of 45° based on the state of the switches. Each state of the Sunflower has a beamwidth of 49.4° in elevation and 159.1° - 186.4° in azimuth (depending on the state) at 2.584 GHz. The maximum gain of each beam is 5.85 dB - 6.14 dB (also depending on the state). The Hermes antenna has 3-states with the half power beam-width (HPBW) and maximum gain simulated at 3 GHz. HPBW in azimuth results in: state A = 70.52°, state AB = 102.4°, and state ABC = 188.48°. The maximum gain of the beam results: state A = 4.66 dB, state AB = 3 dB, and state ABC = 1.86 dB.