Design of a Shared-Aperture Dual-Loop Antenna Using a Mutual Complementary Shape to Improve an Electromagnetic Transparent Characteristics Between S/X-Band Elements

Abstract

In this paper, we propose an S/X-band shared-aperture array antenna with a mutual complementary design to improve the electromagnetic (EM) transparent characteristics. A unit-cell of the proposed antenna includes one dual-loop element for the S-band and 33 dual-loop elements for the X-band. To configure the shared-aperture structure in a limited space, the S-band element is stacked on top of the Xband elements. To solve the practical engineering problems of the shared-aperture antennas, novel design techniques such as using a mutual complementary structure, a coupling compensation array, an interface layer, and an antenna modularization are employed. To verify the antenna feasibility, the fabricated unit-cell extends into a 44 unit-cell array. The fractional bandwidth of the reflection coefficients for the proposed array are 14.7% and 15% in the S-and X-bands, respectively. In the S-band, as the steering direction of the main beam increases from 0 to 45, the maximum gain decreases from 14.6 dBi to 11.8 dBi. In the X-band under the same conditions, the maximum gain varies from 26.6 dBi to 25.3 dBi INDEX TERMS Array antennas, shared aperture antennas, radar, dual loop antennas, mutual complimentary design.