Dual wideband high‐efficient reflective linear‐to‐dual‐circular dual‐rotational polarization converter with two complementary twin‐split square‐ring resonators

Summary A high‐efficient linear‐to‐circular polarization (LP‐to‐CP) converter with dual‐band, dual‐rotational‐direction reflectivity using a single‐layer selective surface (FSS) with a thickness of at 3.5 GHz is designed and investigated. The unit cell, measuring 8 mm × 8 mm ( at 3.5 GHz), consists of two dual‐slotted square rings, with the outer ring providing two nonadjacent CP bands with two reflective resonances in each. The inner ring, with a 90° rotation and the ability to create different polarization and phase behavior, obtains two wide bands with high CP quality. Parametric studies and optimal results show an interesting fact that incident x ( y )‐direction LP wave is effectively converted into right‐hand CP, that is, RHCP (left‐hand CP, i.e., LHCP) wave at the former band and into LHCP (RHCP) at the later band. Finally, a practical 10 × 10 optimal array is fabricated which offers excellent axial ratio below 2 dB over two wide bandwidths: 3.46 to 5.96 GHz (53%: S and C bands) and 7.8 to 12.2 GHz (44%: X band). The converter is angularly stable over 45° and 30° in the stated bands, respectively. A good agreement between simulation and measurement and essential comparisons with literature are also proposed. The results demonstrate significant potential for different dual‐band CP applications with simultaneous isolated uplink and downlink.