A Highly Compact Low-Profile Beam-Switching Transmitarray Antenna for ISM-Band Applications

This leter presents a novel, very low-profile transmitarray antenna (TA) designed specifically for applications in the 24 GHz Industrial, Scientific, and Medical (ISM) band. The design innovation lies in embedding the switchable feed antenna into the beam-focusing surface and adding a reflector, which effectively halves the antenna's size in the boresight direction. This compact antenna allows for easy beam switching through the use of microswitches, making it well suited for vehicular radar applications. A TA consisting of 829 units with an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F/D</i> ratio of 0.5 has been successfully engineered and fabricated for operation at 24.125 GHz. Notably, the antenna exhibits beam-switching capabilities at various angles, including 8°, 16°, and 24° in the negative <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i>-axis direction and 8°, 16°, 24°, and 32° in the positive <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i>-axis direction, in addition to the boresight direction. The maximum measured gain of the antenna is 19.85 dBi, and it can achieve a tilt of 32° with a gain reduction of approximately 3.52 dB compared to the boresight direction.