Low-Profile High-Gain Endfire Antenna With Circular Polarization

A circularly-polarized (CP) traveling-wave endfire antenna featuring low profile, high gain, and simple feeding structure is presented in this communication. Offset parallel strips with proper dielectric loading are employed in a low-profile substrate to achieve two orthogonal electric field components with equal magnitude and 90 degrees phase difference for CP endfire radiation. Meanwhile, periodic phase-loading technique is used to achieve a proper phase constant for high endfire gain. A prototype is designed and fabricated to verify the proposed method. Experimental results demonstrate CP endfire radiation within a frequency band of 9.78-10.09 GHz. The average endfire gain is 10.3 dBic with an average efficiency of 62.5%.