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In this letter a W -band small-size low sidelobe level (SLL) 6 × 16 microwaveguide slot array antenna is proposed based on the silicon micromachining technology. The feeding network within the limited available area consists of several stages of equal T-junctions and TE120-mode-cavity dual-layer power dividers able to build the desired tapering power distribution over a relatively wide bandwidth. The TE120-mode-cavity dual-layer power divider is at the end of the feeding network, which can implement the layer-to-layer transition and the power division simultaneously. Thus, the whole size of the array antenna can be reduced by about 25% compared with the conventional five-stage tree-like feeding network. The overall antenna size is 60 mm × 20 mm × 1.85 mm. The measured maximum gain is 26.1 dBi at 94 GHz, and the corresponding radiation efficiency is 69.2%. The measured SLL in E -plane is below than −18.5 dB within the frequency band from 92 to 96 GHz.

A THz 2-D frequency scanning planar integrated array antenna is developed in this letter. Eight THz leaky-wave antennas are combined with a true-time-delay (TTD) phase-shifting feeding network to steer the beam in two directions by sweeping the frequency. Several H-plane 90° bends with linearly increased length are adopted to achieve the scalable TTD phase shift. The feeding lines are closely spaced to reduce the phase-shifting network occupied area in this progressive phase-shifting scheme. Besides, the E-plane 180° bend is used to construct the double-layer phase-shifting network, maintain the number of multiple scanning sweeps and improve the aperture efficiency. Moreover, in the used microelectromechanical systems (MEMS) fabrication technique, the minimum height of the radiation slot is 0.2 mm, which is too thick and deteriorates the radiating performance. When the double-layer step-profiled radiating slot is used instead of the thick slot, a THz leaky-wave antenna with higher radiation efficiency and better gain flatness can be achieved. Finally, a prototype antenna is fabricated and experimentally validated. The operating frequency range is 325–400 GHz and the beam scanning range is 22.7° × 60° with a maximum radiation gain of 25.28 dBi.

A W-band decoupling structure sandwiched between a pair of high-gain step-profiled horn array antennas using the silicon micromachining technology is proposed. To suppress the surface wave, 18 choke slots with a depth of one quarter wavelength at 94 GHz are arranged in a triangular-grid array and the isolation can be averagely improved by about 7 dB with a range of 2–20 dB. This decoupling structure and two W-band coplanar array antennas are fashioned and fully integrated together by the silicon micromachining technique. Five 400 μ m thick and one 650 μ m thick silicon wafers are utilized and the total thickness of the antennas is 2.65 mm. Thanks to this technology, light weight, compact size, and high integration of the decoupling structure and array antennas can also be achieved. Additionally, the two array antennas share a common ground plane within a small edge-to-edge spacing of 6.05 mm where TM surface waves exist. Experimental studies validate the performance of the proposed triangular-grid choke slot array.