A Low-Profile and High-Gain Frequency Beam Steering Subterahertz Antenna Enabled by Silicon Micromachining

Abstract

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.

Ultra-Compact Micromachined Beam-Steering Antenna Front-End for High-Resolution Sub-Terahertz Radar

“…1. The frequency beam steering frontend is based on a parallel plate waveguide (PPW) leaky wave antenna (LWA) operating between 220 to 300 GHz and provides a continuous beam scanning in a 45° field of view (FoV) [4]. The LWA generates an unbound radiating mode with the periodic slot array on the top plate of the PPW [5].…”

Micromachined Silicon-Core Substrate-Integrated Waveguides at 220–330 GHz

“…A promising alternative fabrication technology is siliconmicromachining using deep reactive-ion-etching (DRIE), which allows for batch fabrication, has superior (micrometer) precision, enables high-complexity geometries, as well as nanometer surface roughness and thus better insertion loss. Impressive device performance has been achieved by micromachining in various sub-THz frequency bands, for instance, for waveguides [3]- [5], couplers [6], low-loss filters [7], [8], OMTs [9], antennas [10], [11], and MEMSreconfigurable devices such as waveguide switches [12] and phase shifters [13].…”

A 38 dB Gain, Low-Loss, Flat Array Antenna for 320–400 GHz Enabled by Silicon-on-Insulator Micromachining

“…These optical systems can achieve high-gain values and wideband operation, but they tend to be heavy, bulky, and involve careful alignment of the feed antenna. Quasi-optical systems have been developed as an alternative solution to optical systems [6], [7], [11]. They can integrate 1-D reflectors or lenses in parallel plate waveguide (PPW) technology, thus reducing the total volume and mass of the system but limiting the beamforming to one plane.…”

“…They can integrate 1-D reflectors or lenses in parallel plate waveguide (PPW) technology, thus reducing the total volume and mass of the system but limiting the beamforming to one plane. Therefore, quasi-optical systems need an additional beamforming network (BFN) in PPW technology to generate a pencil-shaped beam [11], making their fabrication still challenging in the THz range.…”

“…Silicon micromachining is a promising alternative to classical machining techniques for the implementation of waveguide components in the sub-THz frequency range. Silicon micromachining can be used to fabricate low-loss waveguides [12], high quality factor filters [13], and complex waveguide 3-D geometries such as turnstile orthomode transducers [14], switches and phase shifters [15]- [17], or antennas [5], [11], [18]. Campion et al [19] have also recently demonstrated the integration of monolithic microwave integrated circuits (MMICs) in a silicon micromachined platform where the RF, IF, and dc networks are homogeneously integrated.…”