A K-Band Broadband Circularly Polarized Slot Antenna Based on L-Shaped Waveguide Cavity

A new broadband circularly polarized antenna is presented for K-band application in this letter. The circularly polarized radiation is realized by orthogonal-polarized slots based on a special structure of the L-shaped waveguide cavity. To verify the proposed idea, a single element and a 2 × 4-element array are designed, fabricated, and measured. The simulations are agree well with experiments. The results show that the single element achieves the 10 dB impedance bandwidth of 27.5% (18.5-24.5 GHz) and the 3 dB axial ratio bandwidth of 7.1% (19.6-21.2 GHz), while the 2 × 4 element array achieves the 10 dB impedance bandwidth of 27.1% (18.5-24 GHz) and the 3 dB axial ratio bandwidth of 18.7% (19.3-22.6 GHz). Moreover, all-metal structure of the proposed antenna is very appropriate for tough environment applications.