Wideband Optically Transparent Transmitarrays With Fine Metal Line Structure

In this letter, we propose a wideband optically transparent transmitarray (TA) with fine metal line (FML) structure. The proposed TA elements achieve a transmission phase shift range of 394
$^\circ$
with a peak transmission magnitude loss of 3 dB. The adopted FML structure realizes a high measured optical transparency of 71.8% even with the three-layer structure. Two commonly used transmit phase shift implementations are cooperated with FML structure to realize optical transparency. The comparison with traditional transparent scheme shows the superiority of the FML structure. To validate the proposed scheme for transparent TA, we fabricated and measured a sample. The measured results agree well with the simulated ones. The measured realized gain at center frequency and 1 dB gain bandwidth are 24.28 dBi and 30.43%, respectively. The peak total efficiency is 44.35%. To highlight the novelty, a performance comparison with latest related work is carried on. We believe the FML structure can be a potential scheme for future transparent device.