Silicon-Micromachined High-Gain Multi-Beam Beam-Steering THz Graded-Index Lens Antenna Enabled by a Passive Beamforming Interposer

This paper presents, for the first time, a novel highgain beam-steering lens antenna operating in the 610 to 645 GHz range. The antenna, fabricated using silicon micromachining, is based on incorporating a Fresnel lens layer in combination with a frequency-dependent graded-index interposer that acts as a passive beamformer. Frequency-dependent narrow beams are generated using an open waveguide feed. The prototype implemented in this paper features the generation of 8 frequencydependent narrow beams with just two open waveguide feeds. These beams can be steered from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-30^{\circ}$</tex> to 2° in the azimuth. The prototype achieves a measured realized gain of 32.1 dBi with low beam-steering losses of just 0.8 dB. The antenna also exhibits a high radiation efficiency of −1.25 dB. The lens antenna is very compact, measuring only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$15.8 ~\text{mm} \times 15.8 ~\text{mm} \times 0.526$</tex> mm. This beam-steering antenna offers a promising solution for future high-gain, multi-beam THz communication systems.