Circularly Polarized High Gain Coaxial Line Leaky Wave Antenna With Backfire Radiation

This communication presents a leaky wave antenna based on a standard rigid coaxial cable showing circular polarization (CP) in the backfire direction. Here, CP is achieved by using a sequential rotation scheme. Periodic slots are cut on the outer conductor of the cable leading to radiation from the
$n = -1$
th fast space harmonic. The circular geometry of the coaxial cable allows to easily obtain space quadrature by rotating the successive slots by 90° about the cable axis. The required time quadrature for CP is obtained by slot-to-slot separation along the propagation direction. The antenna is designed and fabricated for X-band applications using a low-cost coaxial cable and is excited using a standard SMA connector. The measured gain is 20.26 dBic with 3 dB beamwidth of 14° at 10.26 GHz. The measured axial ratio of the left-handed CP antenna is below 1.8 dB in the backfire direction.