This paper investigates physical dimension limits associated with the low-cost, polymer-based masked stereolithography apparatus (MSLA) 3-D printer, with 50 µm pixels defining the minimum print feature size. Based on the discretization properties of our MSLA 3-D printer, multi-step quantization predistortion is introduced to correct for registration errors between the CAD drawing and slicing software. This methodology is applied to G-band 5 th order metal-pipe rectangular waveguide filters, where the pixel pitch has an equivalent electrical length of 8.5 • at center frequency. When compared to the reference Chebyshev filter, our chained-function filter exhibits superior S-parameter measurements, with a low insertion loss of only 0.6 dB at its center frequency of 182 GHz, having a 0.9% frequency shift, and an acceptable worst-case passband return loss of 13 dB. Moreover, with measured dimensions after the 3-D printed parts have been commercially electroplated with a 50 µm thick layer of copper, the re-simulations are in good agreement with the S-parameter measurements. For the first time, systematic (quantization) errors associated with a pixelbased 3-D printer have been characterized and our robust predistortion methodology has been successfully demonstrated with an upper-millimeter-wave circuit. Indeed, we report the first polymer-based 3-D printed filters that operate above W-band. As pixel sizes continue to shrink, more resilient (sub-)THz filters with ever-higher frequencies of operation and more demanding specifications can be 3-D printed. Moreover, our work opens-up new opportunities for any pixel-based technology, which exhibits registration errors, with its application critically dependent on its minimum feature size.
This work demonstrates the hybrid integration of a complementary metal-oxide-semiconductor (CMOS) radio frequency integrated circuit (RFIC) into a host 3-D printed metal-pipe rectangular waveguide (MPRWG). On-chip Vivaldi antennas are used for TE 10 -to-thin-film microstrip (TFMS) mode conversion. Our packaging solution has a combined measured insertion loss of only 1 dB/transition at 126 GHz. This unique packaging and interconnect solution opens up new opportunities for implementing low-cost subterahertz (THz) multichip modules.
Polymer-based additive manufacturing using 3-D printing for upper-millimeter-wave (ca. 100 to 300 GHz) frequency applications is now emerging. Building on our previous work, with metal-pipe rectangular waveguides and free-space quasi-optical components, this paper brings the two media together at G-band (140 to 220 GHz), by demonstrating a compact multi-channel front-end subsystem. Here, the proof-of-concept demonstrator integrates eight different types of 3-D printed components (30 individual components in total). In addition, the housing for two test platforms and the subsystem are all 3-D printed as single pieces, to support plug and play development; offering effortless component assembly and alignment. We introduce bespoke free-space TRM calibration and measurement schemes with our quasi-optical test platforms. Equal power splitting plays a critical role in our multi-channel application. Here, we introduce a broadband 3-D printed quasi-optical beamsplitter for upper-millimeter-wave applications. Our quantitative and/or qualitative performance evaluations for individual components and the complete integrated subsystem, demonstrate the potential for using consumer-level desktop 3-D printing technologies at such high frequencies. This work opens-up new opportunities for low-cost, rapid prototyping and small-batch production of complete millimeter-wave front-end subsystems.
This work demonstrates the integration of a lowpass filter into a 90 • waveguide twist at W -band (75-110 GHz), manufactured using polymer-based 3-D printing. For the first time, a 1-D periodic electromagnetic bandgap (EBG) structure is incorporated within a waveguide twist. Unlike conventional filters, implemented using irises and septa, EBG structures employing hollow cavities are structurally robust and mechanically insensitive to 3-D printing. The measured average passband insertion loss is only 0.48 dB at the W -band while using our unconventional split-block solution (H-plane a-edge split with raised lips). A nontwist thru filter has also been demonstrated, as a reference. Our approach demonstrates the potential for the low-cost manufacture of compact and high-performance multifunctional integrated waveguide components at millimeterwave frequencies.
This paper demonstrates the current state-of-the-art in low-cost, low loss ruggedized polymer-based 3-D printed G-band (140 to 220 GHz) metal-pipe rectangular waveguide (MPRWG) components. From a unique and exhaustive up-to-date literature review, the main limitations for G-band split-block MPRWGs are identified as electromagnetic (EM) radiation leakage, assembly part alignment and manufacturing accuracy. To mitigate against leakage and misalignment, we investigate a 'trough-and-lid' split-block solution. This approach is successfully employed in proof-of-concept thru lines, and in the first polymer-based 3-D printed 90° twist and symmetrical diaphragm inductive iris-coupled bandpass filters (BPFs) operating above 110 GHz. An inexpensive desktop masked stereolithography apparatus 3-D printer and a commercial copper electroplating service are used. Surface roughness losses are calculated and applied to EM (re-)simulations, using two modifications of the Hemispherical model. The 7.4 mm thru line exhibits a measured average dissipative attenuation of only 12.7 dB/m, with rectangular-to-trapezoidal cross-sectional distortion being the main contributor to loss. The 90° twist exhibits commensurate measured performance to its commercial counterpart, despite the much lower manufacturing costs. A detailed time-domain reflectometry analysis of flange quality for the thru lines and 90° twists has also been included. Finally, a new systematic iris corner rounding compensation technique, to correct passband frequency down-shifting is applied to two BPFs. Here, the 175 GHz exemplar exhibits only 0.5% center frequency up-shifting. The trough-and-lid assembly is now a viable solution for new upper-mm-wave MPRWG components. With this technology becoming less expensive and more accurate, higher frequencies and/or more demanding specifications can be implemented.
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