A 220 GHz Reconfigurable Reflectarray Antenna Using GaN HEMT Device

Reconfigurable reflectarray antennas (RRAs) at submillimeter and terahertz frequencies are critical for communications and imaging applications. This article examines, fabricates, and measures an RRA integrated with a gallium nitride (GaN) high electron mobility transistor (HEMT) device, operating at 220 GHz. A reflectarray element on a sapphire substrate, incorporating a GaN HEMT device and a matching circuit, is designed to achieve a 1-bit phase shift of the reflected wave. Detailed analyses of the HEMT device model and the submillimeter element design are conducted. The proposed RRA is fabricated using standard chip processes, resulting in a 16 x 16 element array on an 11.2 x 11.2 x 0.1 mm(3) chip. The 1-bit phase-shift performance is validated through two-state reflection coefficient measurements. Due to the fabrication challenges of element control, a column-control biasing network is implemented. The 1-D beam-scanning capability of the RRA prototype is experimentally demonstrated at 220 GHz, achieving a scanning angle of up to 40 degrees. The experimental results demonstrate strong agreement with theoretical predictions.