A very low-profile sub-THz high-gain frequency beam steering antenna, enabled by silicon micromachining, is reported for the first time in this paper. The operation bandwidth of the antenna spans from 220 GHz to 300 GHz providing a simulated field of view of 56 •. The design is based on a dielectric filled parallel-plate waveguide (PPW) leaky-wave antenna fed by a pillbox. The pillbox, a two-level PPW structure, has an integrated parabolic reflector to generate a planar wave front. The device is enabled by two extreme aspect ratio, 16 mm x 16 mm large perforated membranes, which are only 30 µm thick, that provide the coupling between the two PPWs and form the LWA. The micromachined low-loss PPW structure results in a measured average radiation efficiency of −1 dB and a maximum gain of 28.5 dBi with an input reflection coefficient below −10 dB. The overall frequency beam steering frontend is extremely compact (24 mm x 24 mm x 0.9 mm) and can be directly mounted on a standard WM-864 waveguide flange. The design and fabrication challenges of such high performance antenna in the sub-THz frequency range are described and the measurement results of two fabricated prototypes are reported and discussed.

Modern K/Ka-band satellite communications have become increasingly demanding in recent years with regard to the performance of the terminal antenna used in the link. These terminals should be high-gain and broadband, as well as guarantee polarization diversity over a large field-of-view. A lowprofile is also highly desired to integrate the antenna system into a variety of moving platforms such as aircraft and trains. An ultra-low-profile continuous transverse stub array is proposed here to tackle these challenges. The antenna array is realized in printed circuit board technology by adopting a contactless transition between the stacked-up layers without resorting to blind or buried vias. The proposed antenna is wideband (impedance matched within the band 19-31 GHz, i.e., ∼ 50%) and provides multi-beam radiation for polar angles as far as ±22.5 • . The peak value of the gain is 19.7 dBi and the maximum radiation efficiency equals 50%. Furthermore, the antenna array is combined with a dual-band polarization converter. The latter provides orthogonal circular polarization in two non-adjacent bands. The overall antenna system performs right-and left-hand circular polarization within the SatCom down-and up-links in the K/Ka-band, respectively. For each polarization, the axial ratio is below 3 dB over 9.47% and 4.42% fractional bandwidths, respectively.

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