Switchable T-Slot for Dual-Circularly-Polarized Slot-Array Antennas in Ka-Band

This letter presents two slotted array antennas working in the
Ka
-band with switchable circular polarization capability. The first prototype is a series-fed slotted-waveguide linear array composed of ten T-shaped slots. The second antenna is a 2-D array with 2 × 2 T-shaped slots fed by a corporate distribution network. In both cases, a reflection coefficient below
$-$
10 dB has been experimentally observed within the targeted frequency band between 29.5 and 30.5 GHz. Good polarization purity is achieved for both polarization senses and in both prototypes. The fundamental contribution of this letter is to propose a simple mechanism to switch the circular polarization sense in a low-cost, low-profile, and high-efficient antenna. The design and experimental results confirm that the solution is suitable for both one- and two-dimensional arrays in the millimeter-wave band.