Novel broadband angular stable linear‐circular and linear‐cross polarizer based on inductive grid loaded H‐dipole in both reflection and transmission modes

Abstract

A novel broadband linear-circular and linear-cross polarization converter for K to Ka-band applications is demonstrated in this work. The proposed structure primarily consists of an inductive grid in orthogonal with an H-shaped dipole as top Frequency Selective Surface (FSS) and a modified horizontal dipole as bottom FSS; a 1 mm thin FR-4 substrate is separating both. During transmission, it can convert the linearly polarized EM wave to a circular one, with Axial Ratio (AR) ≤ 3 dB from 13.08 to 25.13 GHz with 63.07% Fractional Bandwidth (FBW). In addition, this polarizer can work in reflection mode also when the bottom FSS is replaced by a Perfect Electrical Conductor (PEC), demonstrating the linear-circular polarization with AR (≤3 dB) from 16.94 to 18.64 GHz (RHCP/LHCP) and 24.5–40.32 GHz (LHCP/RHCP) with FBW 9.56% (Ku-band), and 48.81% (K- and Ka-band), respectively. Besides, linear-circular conversion, it performs linear-cross conversion in reflection mode with polarization conversion ratio (PCR) above 90% from 19.71–22.22 GHz, 43.57–48.81 GHz, 53.50–55.32 GHz with 13.89%, 11.34%, 3.32%, FBW, respectively. The equivalent circuit model of the proposed converter is extracted. Surface current distribution profiles at multiple plasmonic resonances are investigated to understand the reason behind the multi-polarization conversion. The performance is angular stable up to 45° for both transverse electric (TE) and transverse magnetic (TM) incidences for reflection as well as transmission modes. The unitcell is compact with periodicity 0.114λL × 0.114λL and a thickness of 0.044λL, where λL is the free-space wavelength of the lowest frequency. This design's novelty lies in dual-mode stable angular performance in both reflection and transmission cases. Also, highly miniaturized architecture and circular rotation switching in the consecutive bands make this design suitable for real-time scenarios.