Single Layer Multi-Band Transmissive Type Linear to Circular Polarization Converter With Wide Angular Stability for C-, X-, and Ku-Band Applications

This paper presents a linear-to-circular polarization converter (LCPC) used for multi-band functionality. The LCPC surface features symmetrically printed copper strips on a single-layer substrate and is surrounded by a square substrate integrated waveguide (SIW) cavity arranged periodically in two dimensions. The study successfully utilizes the LCPC surface to achieve a desirable axial ratio (AR) band width (BW) below 3 dB in multiple frequency ranges, specifically: 1) 4.51-4.80 GHz, 2) 6.51-6.80 GHz, 3) 9.01-9.20 GHz, 4) 10.90-12.40 GHz, and 5) 17.05-17.49 GHz. The LCPC induces a change in polarization as the wave propagates through it. In the first ( $f_{31}$ ) and fourth ( $f_{34}$ ) frequency bands, the initially linearly polarized (LP) wave transforms into a left-hand circularly polarized (LHCP) wave. Conversely, in the second ( $f_{32}$ ), third ( $f_{33}$ ), and fifth ( $f_{35}$ ) frequency bands, the wave converts into a right-hand circularly polarized (RHCP) wave. Measurement results indicate that the LCPC provides circularly polarized (CP) wave bandwidths of 12.72%, 4.8%, 2.4%, 11.39%, and 3.15% across frequency ranges of 3.9 - 4.43 GHz, 6.21- 6.52 GHz, 8.9-9.08 GHz, 10.51-11.78 GHz, and 16.85-17.39 GHz, respectively. This characteristic renders the LCPC suitable for utilization in the C (4-8 GHz), X (8-12 GHz), and Ku (12-18 GHz) frequency bands.