Novel Asymmetric T-Shaped Radiating Element for Circularly-Polarized Waveguide Slot Arrays

Waveguide slot arrays are a widely used solution to attain linearly polarized high-gain antennas. In this article, an all-metal T-shaped radiating element is conceived with the aim to replace the usual rectangular slots and attain circularly polarized arrays, preserving their good properties. The polarization conversion is made possible due to the inclusion of a parasitic arm perpendicular to the main active slot. Due to the fact that this second arm is not directly fed by the waveguide but coupled to the active slot, the T-shaped element can be used in any array originally formed by metallic rectangular slots. The design of resonant shunt arrays has been addressed here for validation purposes. The experimental results of two sample linear arrays at 30 GHz demonstrate the design accuracy and manufacturing reliability, reporting an axial ratio below 2 dB within a bandwidth of 1.9 GHz and a peak efficiency around 98%.