Dual-Band Dual-Rotational-Direction Angular Stable Linear-to-Circular Polarization Converter

A dual-band dual-rotational-direction reflective linear-to-circular polarization converter based on metasurface is designed, fabricated, and measured. The unit cell consists of an open ring and a square patch. The open ring creates two resonances, and the square patch is used to improve the axial ratio (AR). It is shown that this design can be working at two frequency bands, i.e., 29.0-41.5 GHz and 52.5-61.5 GHz. Interestingly, it is found that the linearly polarized wave in x(y)-direction can be converted into right(left)-handed circularly polarized wave at the former band, and into left(right)-handed circularly polarized wave at the later band. Compared to other designs in the literature, this design demonstrates 45 degrees angular stability for 3 dB AR over two operational bands. In addition, this design is realized on a single substrate, making it easier to be fabricated. Furthermore, the insertion loss can be as low as 0.5 dB, showing a very low-loss property. Lastly, the unit cell is less than 0.2 wavelength at the lower frequency band. The measured results show good agreement with simulation. Potential applications can be envisaged in dual-band and dual-polarization communication.