Simple Reconfigurable Circularly Polarized Antenna at Three Bands

Area of Science:

• Electromagnetics and antenna theory
• Wireless communication systems

Background:

• Circularly polarized (CP) antennas are crucial for mitigating multipath fading and polarization mismatch in wireless systems.
• Reconfigurable antennas offer flexibility in adapting to different communication standards and environments.
• Existing multi-band CP antennas often suffer from complex designs, high cost, or limited polarization switching capabilities.

Purpose of the Study:

• To design and demonstrate a simple, low-cost, triple-band circularly polarized (CP) antenna.
• To achieve reconfigurable polarization switching between right-hand CP (RHCP) and left-hand CP (LHCP) at distinct frequency bands.
• To validate the antenna's performance for potential use in WLAN and WiMAX applications.

Main Methods:

• A monopole loop antenna was utilized as the primary radiator.
• A parasitic loop was incorporated around the primary radiator to achieve an additional CP band.
• Two PIN diodes were employed to control the ON/OFF states for polarization reconfigurability.
• Fabrication and measurement of the proposed antenna prototype.

Main Results:

• The fabricated antenna achieved an impedance bandwidth of 52.6% (2.34-4.01 GHz).
• Axial ratio bandwidths for both RHCP and LHCP states were achieved at three bands: 3.5% (2.47-2.56 GHz), 6.6% (3.20-3.42 GHz), and 2.4% (3.74-3.83 GHz).
• Measured broadside gains ranged from 1.2 to 2.7 dBi within the axial ratio bandwidths.

Conclusions:

• The proposed antenna successfully demonstrates triple-band operation with reconfigurable dual-sense CP.
• The design offers a low-cost solution using only two PIN diodes for polarization switching.
• The antenna is well-suited for applications such as Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX).