Varactor-Based Reconfigurable Intelligent Surface with Dual Linear Polarisation at K-Band

Full polarisation coverage is necessary for reconfigurable intelligent surfaces to be suitable for deployment in real-world wireless communication networks. This work explores a dual-linear polarisation unit cell design for operation at the European mmWave Pioneer band covering 24.25 - 27.5 GHz. A microstrip patch coupled to two orthogonally-arranged parasitic patches through two varactor diodes facilitate a 1-bit reflection response with a periodicity of 0.27λ
0
. A -40 dB cross-polarisation level is enabled across the band by offset-tuning varactor placement and vias. The reflection responses are ascertained with manufacturer-provided S-parameter component data to ensure realistic simulations.