Varactor Based Reconfigurable Reflectarray Antenna at Ka-Band

This paper presents a manufactured electronically reconfigurable offset feed reflectarray antenna at 25 GHz. The reflective surface consists of 144 elements arranged in a 12 by 12 square grid. Each element is constructed from two patch halves that are tuned by a varactor diode placed in between. Simulations show a phase tuning range of 315° at center frequency. As feed, an horn antenna is placed at a distance of 99 mm at an offset angle of 30°. Measurement results of the prototype show a maximum scanning loss of 4.5 dB for beam steering from -60° to 60° in horizontal plane. In the opposite angular direction of the feed, the steered beams experience degradation due to the presence of specular reflections. Furthermore, a reflecting surface loss of smaller than 2dB and an usable 3dB-bandwidth of 12% are determined.