Optically Transparent Circularly Polarized Reflectarray for Ka-Band Applications

An optically transparent right-handed (RH) circularly polarized (CP) reflectarray (RA) with 3940 cells is proposed in this communication. The overall structure is composed of a 0.125-mm-thick polyethylene terephthalate (PET) film with fine metal line (FML), quartz glass with a thickness of 0.5 mm, a 0.6-mm air layer, indium tin oxide (ITO) ground, and an RHCP feed horn. The overall size of the reflection plane is $170\times 170\times 1.225$ mm. The shaped pattern of a double arrow, two diamond, and a chain with three incomplete diamonds form the circuit of unit cell. The RA cell is miniaturized ( $2.4\times 2.4$ mm) by bending the corresponding current path with a linewidth of $40~\mu $ m. To compensate for the loss induced by the FML, we increased the resolution of the reflection plane, and the measured results showed that the peak gain and aperture efficiency (AE) reached 32.5 dBic and 54.9%, respectively. The 3-dB gain bandwidth (BW) reached 23.2% (28.5–36 GHz), and the axial ratio (AR) is less than 1.5 dB across the frequency band. These advantages, such as optical transparency, high directionality, and good circular polarization characteristics, make it a potential candidate for satellite communication applications.