High Scanning Rate Millimeter Wave Circularly Polarized CTS Leaky-Wave Antenna

A millimeter wave circularly polarized (CP) continuous transverse stub (CTS) leaky-wave antenna (LWA) with high scanning rate is proposed in this communication. The LWA is composed of an improved parallel plate waveguide (PPW) based CTS array and a compact power divider based linear source generator. The high scanning rate is obtained by alternatively arranging periodic ridges on both plates of bent PPW, which can be regarded as an interdigital structure and can extend the current path. A low profile single layer linear-to-circular polarizer (LCP) with wide-incident-angle is designed to realize CP radiation. In order to increase the incident angle of the LCP, a modified metasurface unit based on Jerusalem cross is presented. To verify the proposed design, a 12-element LWA with the LCP is simulated and fabricated. The measured results show that the LWA achieved a CP scanning range from -56° to 52° with the -10 dB impedance bandwidth (BW) of 11.7% (28.3 ~ 31.8 GHz). The scanning rate is 9.3°/%BW. Within the beam scanning range, the axial ratio is less than 2.9 dB, and the maximum gain is 25.5 dBi. The insertion loss of LCP is lower than 1.1 dB.