K_a-Band Metal-Insulator-Graphene Diode-based Thin-Film Cascaded Reflective-Type Phase Shifter

This work presents the design, implementation, and characterisation of a K<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</inf>-band thin-film two-stage compact analogue phase-shifter. The design exploits a reflective-type configuration which utilizes four metal-insulator-graphene diodes as reflective loads. The fabricated prototype is realised on a 8.1 µm-thick flexible polyimide (PI) substrate and occupies less than 0.7 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of chip area including the contact pads. The assessment of the fabricated circuit reveals an S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> performance better than -13 dB and an S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</inf> measurement of -3.3 dB with a tolerance of ± 0.5 dB across the frequency band of 28 – 36 GHz with a tunable phase difference (∆ϕ) exceeding 70°. The introduced flexible thin-film technology promotes the realisation of flexible cost-effective beam steering for smart surfaces and biomedical applications.