Design of a Low Profile Flexible Tri-Band Frequency Surface Applied in X-Band, K-Band and Millimeter-Band

A low profile flexible miniaturized tri-band frequency surface is proposed by cascading three layers of periodic arrays. The top and bottom layers have the same square patch structure embedded in the bending gap, whereas the middle layer has an interlaced metal grid structure. The medium between each layer is made of flexible polyimide material with a thickness of only about 0.2mm. The coupling of the three metal layers gives rise to a first X-band passband, with a central frequency of 10.6 GHz. The interlaced metal grid structure generates a second K-band passband, with a central frequency of 24.1GHz. The two-layer symmetrical planar cascade structure produces double-peak resonances at 39.4 GHz and 46.2 GHz, forming a third millimeter-wave passband. Compared with the traditional tri-band FSSs, due to the combination of bending technology and multi-screen cascade technology, the reported structure generates the first and second passbands with miniaturization and good angle stability, and the third passband with rectangular filtering characteristics. Besides fabrication and tests, the corresponding equivalent circuit model is also established in order to analyze the transmission characteristics. The test results are well compatible with the simulation results.