Series-Fed All-Metal and Wide-Axial-Ratio-Bandwidth Circularly Polarized Leaky-Wave Antenna With Endfire Radiation

A series-fed and all-metal circularly polarized (CP) endfire leaky-wave array antenna with a wide axial ratio (AR) bandwidth is presented in this letter. The main component consists of a double-sided parallel stripline (DSPSL) and multiantenna elements. Based on the inherent 90° phase difference of complementary dipoles, the CP radiation can be achieved by the small loop and the short dipole that is regarded as the antenna element. Fed by DSPSL, the multiantenna elements can be excited to form an endfire radiation. By introducing the bending line between the loop and DSPSL, the electric current on the top flows through the bending line, the half-loop, the short pin, and the bottom half-loop to form a closed circuit, which makes the complementary dipole be stimulated simultaneously. The array factor is optimized by tuning the separation between adjacent antenna elements. One end of the DSPSL is connected to a coaxial SMA connector, and the other one is matched by load to form a traveling wave mode. A prototype of this antenna is fabricated and measured to verify the antenna concept, and experimental results show that it has an impedance bandwidth of 19.4%, AR bandwidth of 17.6%, and peak gain of 12.8 dBi.