A Metamaterial-Based $S/X$ -Band Shared-Aperture Phased-Array Antenna With Wide Beam Scanning Coverage

This article proposes an ultralow profile S/X-band shared-aperture phased-array antenna (SAPAA), which can achieve wide beam scanning coverage in both the Sand X-bands. The SAPAA consists of an S-band array with a triangular placement that has 11 elements and a grid array with 8 × 16 X-band elements. To avoid grating lobes in wide beam scanning coverage, a metamaterial-based stacked mushroom structure is proposed to reduce the array spacing of the two bands, where an X-band patch antenna is stacked on a traditional mushroom structure. A 4 × 4 subarray of the stacked mushroom structure operates as a single antenna element in S-band. Consequently, each S-band element corresponds to a 4 × 4 subarray of the X-band element. Because a triangular arrangement in the S-band array and a square arrangement in the X-band array are employed, the array spacing of the two bands is 0.54λL0and 0.51λH0, respectively, which is suitable for wide beam scanning coverage. Moreover, the shorting pin of the mushroom structure is also the feeding pin of the X-band patch. This structure reuse technology reduces the whole profile to less than 0.04λ0. To verify this design, a prototype is fabricated through the multilayer printed circuit board process. It realizes ±50° beam coverage in both the Sand X-bands.