Design of a shared-aperture antenna with a hashmark-shaped loop to improve electromagnetic transparent characteristics

In this paper, we propose a shared-aperture antenna with a hashmark-shaped loop to improve electromagnetic (EM) transparent characteristics. The proposed antenna consists of one S-band element and $3 \times3$ X-band elements with a dual loop structure. The S-band element has a hashmark-shaped loop, which can improve the EM transparent characteristics in the X-band without degradation of the antenna bandwidth. The measured fractional bandwidths in the S and X bands are 14.7% and 15%, respectively. The results demonstrate that the proposed antenna is suitable for multi-function radar applications.