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

A millimeter-wave (mmW) circularly polarized (CP) continuous transverse stub (CTS) leaky wave antenna (LWA) with a 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 a 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 the Jerusalem cross (JC) 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 (AR) is less than 2.9 dB and the maximum gain is 25.5 dBi. The insertion loss (IL) of LCP is lower than 1.1 dB.