Fractal Shaped Multi-Layer Unit Cell Design With Tunable Polarization Conversion Performance

A fractal shaped multi-layer unit cell design is proposed in this article to conceive tunable polarization conversion performance over the X-band frequencies for practical use. The multi-layer Minkowski-shaped unit cell structure is designed with a varactor diode element incorporated in it, whose capacitance values can be changed to obtain tunable polarization conversion performance in real-time operation. The structure offers 95% to 99% polarization conversion efficiency over the band of interest and can be tuned over a range of frequency values with a stable and finite granularity feature, justifying its utility for real-time applications. It also retains its polarization conversion performance along with the tunability characteristics over an angular region of 20 degree, when the structure is tilted to 10 degrees on both sides of normal incidence, highlighting its stability of performance for oblique incidence conditions. Detailed simulation results are presented to describe the process of choosing the optimal position of the via components and their diameter values, which quantitatively determine and maintain the conversion characteristics.