A Compact CRLH Circularly Polarized Leaky-Wave Antenna Based on Substrate-Integrated Waveguide

A compact single-radiator circularly polarized (CP) leaky-wave antenna (LWA) based on composite right/left-handed (CRLH) transmission line is presented. The proposed antenna is based on substrate-integrated waveguide (SIW), and its unit cell consists of a T-shaped interdigital slot, which provides a CRLH property, a proper CP, and also effective compactness for the full-length LWA. The proposed LWA provides beam scanning from -19 degrees to +84 degrees over the frequency range of 7.35-10.15 GHz, while maintaining a good CP. By providing the balanced condition for the CRLH unit cell, a continuous backward-to-forward scanning including broadside is achieved. The maximum gain of the LWA is 8.95 dB which is satisfactory, considering the compactness of the antenna. Moreover, the radiation efficiency has an average of 85.7% over the operating frequency hand. The measurement results are in good agreement with the simulation ones and show considerable advantages over the SIW-based CP LWAs proposed in the recent literature.