An optimized low loss feed network of a compact Vivaldi antenna array for high quality radar imaging system

A low cost 8×1 antipodal Vivaldi subarray with low dispersion and almost constant gain has been developed for high quality imaging applications. The array antenna is fed by a low-loss SIW feed network with elegant use of vias to minimize insertion loss over 8–12 GHz band. The feed network is an 8-way divider fed by a novel wideband GCPW transition, and directly connected to the antipodal Vivaldi elements. The SIW feed is comprised of various T and Y junctions where the vias´ numbers, locations and shapes are optimized to achieve less than 1 dB insertion loss, ±4° and ±0.9 dB phase and amplitude imbalances, respectively. Measured results of the subarray performance are consistent with our simulation; it has 9–13 dB gain, −14 dB SLL, and better than 20 dB front-to-back ratio and occupies 10cm×6cm. Images obtained using the developed array demonstrated significant improvement compared to previously developed feeds with microstrip or unoptimized SIW splitters.