A Millimeter Wave Multi-beam Transparent Transmitarray Antenna at Ka-band

International audienceThis letter presents a transmitarray antenna (TA) in the 27.5-29.5 GHz frequency band. The proposed TA is optically transparent, offers the possibility of steering the beam in the H-plane from -30° to 30°, and has a low profile and lightweight. One can achieve these properties using a novel unit-cell, composed of meshed double-circle rings printed on polymethylmethacrylate (PMMA) substrates, a plastic material transparent to visible light. This unit-cell provides a phase-shift of 300° for an insertion loss lower than 1 dB at 28.5 GHz. In turn, the TA sources consist of 2×2-element arrays of aperture-coupled stacked patch antennas. The choice of a patch array over a horn array allows one to reduce the total profile and weight of the TA. We have fabricated and tested a transparent TA with a diameter of 9.9 wavelengths at 28.5 GHz, yielding a broadside gain of 25 dBi and -1 dB gain bandwidth of 1.8 GHz, off-axis 30° beam presents a peak gain of 21.5 dBi and -1 dB gain bandwidth of 1.4 GHz. The measured results are in good agreement with the simulated ones all over the frequency band of interest