Structured-Glass Waveguide Technology for High-Performance Millimetre-Wave Components and Systems

Abstract

This work presents a novel waveguide medium based on laser-induced structured-glass for the design of high-end millimetre-wave components and systems. The material properties, fabrication process and functional attributes of the structured-glass technology are first described and then applied in order to demonstrate a fourth-order bandpass filter prototype operating within the W-band frequency range, centered around 88 GHz with a narrow fractional bandwidth of 2.3%. The basic filter design, dimensional considerations, and assembly process are discussed in order to outline the fabrication process. The prototype filter, along with its associated feed-line transitions and split-block interface are measured and characterized in the laboratory in order to validate the design approach. The measured response is shown to be exceptionally accurate; the insertion loss is found to be approximately 1.43 dB -1.97 dB throughout the measured passband with a return loss of better than 22 dB and center-frequency offset of approximately 0.117%. A comparison to existing technologies is discussed in order to highlight the advantages of the proposed medium and to contrast the differences in both manufacture and achievable results for high-end components.

RF Glass Technology Is Going Mainstream: Review and Future Applications

“…Here, laser-induced bulk micromachining can be used to realized complex structures with the highest precision and feature sizes, in particular holes, as small as 30 μm. The authors of [131] present a glass-integrated W-band filter based on rectangular waveguide cavities (see Fig. 10).…”

Structured-Glass Waveguides (SGW) and TRL Calibration Standards

“…The transmission line section for measurement is specified as 14 mm. Similar to the feeding mechanism described in [1], the structured-glass component is held in a metallic split-block interface that houses UG-387/U waveguide flanges and feed the E-plane port transitions that are micromachined in the top wafer (cover) layer. In this work, wideband E-plane transitions are developed to feed the waveguide structure and reduce reflections throughout the frequency region of interest.…”

“…Work in the millimetre-wave regions have been dominated by computer numerical control (CNC) milling, deep reactive ion etching (DRIE) of silicon wafers, or SU-8 photo-resist micromachining, each of which has demonstrated varying results when applied to waveguide-based passive components. Albeit, in [1], a novel structured-glass waveguide (SGW) technology was demonstrated as a candidate for achieving high-performance and batch-producible components, where an 88 GHz filter was demonstrated with remarkable accuracy. This accuracy was enabled by the fabrication process and allows for vertical sidewalls to be produced, and ultimately, overcomes the issues of sidewall under-etching and scalloping as indicated in technologies such as DRIE.…”

Compact Triangular-Cavity Singlet-Based Filters in Stackable Multilayer Technologies

“…For the next generation of satellite communications, radar and deep-space exploration, filter designs must be continuously adapted to optimize performance while the allocation of frequency bands reaches beyond the radio-frequency spectrum. Although, different technologies such as high-precision milling [1], SU-8 [2], silicon micromachining [3] and structured glass [4] have been able to demonstrate the ability to reach well into the terahertz and subterahertz regions, progressive design solutions must be continuously explored to coincide with technological advancements.…”

“…In regards to simple manufacturing procedures for millimetre and sub-millimetre wave filter components, stackable technologies and multi-layer designs have been demonstrated using methods such as electronic-band-gap (EBG) [17], dif- fusion bonding of laminated metal plates [18], deep reactive ion etching (DRIE) [3], [5], and structured-glass waveguide (SGW) components [4]. However, miniaturization methods at the millimetre and sub-millimetre wave bands becomes increasingly difficult due to highly stringent dimensions combined with the need for precise alignment of multiple structural layers.…”