| 1. |
- Anoshkin, Ilya V., et al.
(författare)
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Freeze-Dried Carbon Nanotube Aerogels for High-Frequency Absorber Applications
- 2018
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 10:23, s. 19806-19811
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Tidskriftsartikel (refereegranskat)abstract
- A novel technique for millimeter wave absorber material embedded in a metal waveguide is proposed. The absorber material is a highly porous carbon nanotube (CNT) aerogel prepared by a freeze-drying technique. CNT aerogel structures are shown to be good absorbers with a low reflection coefficient, less than -12 dB at 95 GHz. The reflection coefficient of the novel absorber is 3-4 times lower than that of commercial absorbers with identical geometry. Samples prepared by freeze-drying at -25 degrees C demonstrate resonance behavior, while those prepared at liquid nitrogen temperature (-196 degrees C) exhibit a significant decrease in reflection coefficient, with no resonant behavior. CNT absorbers of identical volume based on wet-phase drying preparation show significantly worse performance than the CNT aerogel absorbers prepared by freeze-drying. Treatment of the freeze-dried CNT aerogel with n- and p-dopants (monoethanolamine and iodine vapors, respectively) shows remarkable improvement in the performance of the waveguide embedded absorbers, reducing the reflection coefficient by 2 dB across the band.
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| 2. |
- Beuerle, Bernhard, 1983-, et al.
(författare)
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A CPW Probe to Rectangular Waveguide Transition for On-wafer Micromachined Waveguide Characterization
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A new transition from coplanar waveguide probe to micromachined rectangular waveguide for on-wafer device characterization is presented in this article. The transition is fabricated in the same double H-plane split silicon micromachined waveguide technology as the devices under test, requiring no additional post-processing or assembly steps. We outline the design and fabrication process of the transition for the frequency band of 220 – 330 GHz. A coplanar waveguide structure acts as the probing interface, with an E-field probe protruding in the waveguide cavity exciting the fundamental waveguide mode. Guard structures around the E-field probe increase the aspect ratio during deep reactive ion etching and secure its geometry. A full equivalent circuit model is provided by analyzing its working principle. RF characterization of fabricated devices is performed for both single-ended and back-to-back configurations. Measured S-parameters of the single-ended transition are obtained by applying a two-tiered calibration and are analyzed using the equivalent circuit model. The insertion loss of the single-ended transition lies between 0.3 dB and 1.5 dB over the whole band, with the return loss in excess of 8 dB. In addition to previously reported characterization of a range of devices under test the viability of the transition for on-wafer device calibration is demonstrated by characterizing a straight waveguide line, achieving an insertion loss per unit length of 0.02 – 0.08 dB/mm in the frequency band of 220 – 330 GHz.
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| 3. |
- Beuerle, Bernhard, 1983-, et al.
(författare)
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A CPW Probe to Rectangular Waveguide Transition for On-Wafer Micromachined Waveguide Characterization
- 2024
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-342X .- 2156-3446. ; 14:1, s. 98-108
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Tidskriftsartikel (refereegranskat)abstract
- A new transition from coplanar waveguide probe to micromachined rectangular waveguide for on-wafer device characterization is presented in this article. The transition is fabricated in the same double H-plane split silicon micromachined waveguide technology as the devices under test, requiring no additional post-processing or assembly steps. We outline the design and fabrication process of the transition for the frequency band of 220–330 GHz. A coplanar waveguide structure acts as the probing interface, with an E-field probe protruding in the waveguide cavity exciting the fundamental waveguide mode. Guard structures around the E-field probe increase the aspect ratio during deep reactive ion etching and secure its geometry. A full equivalent circuit model is provided by analyzing its working principle. RF characterization of fabricated devices is performed for both single-ended and back-to-back configurations. Measured S-parameters of the single-ended transition are obtained by applying a two-tiered calibration and are analyzed using the equivalent circuit model. The insertion loss of the single-ended transition lies between 0.3 dB and 1.5 dB over the whole band, with the return loss in excess of 8 dB. In addition to previously reported characterization of a range of devices under test the viability of the transition for on-wafer device calibration is demonstrated by characterizing a straight waveguide line, achieving an insertion loss per unit length of 0.02–0.08 dB/mm in the frequency band of 220–330 GHz.
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| 4. |
- Beuerle, Bernhard, 1983-, et al.
(författare)
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A Very Low Loss 220–325 GHz Silicon Micromachined Waveguide Technology
- 2018
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - : IEEE. - 2156-342X .- 2156-3446. ; 8:2, s. 248-250
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Tidskriftsartikel (refereegranskat)abstract
- This letter reports for the first time on a very low loss silicon micromachined waveguide technology, implemented for the frequency band of 220–325 GHz. The waveguide is realized by utilizing a double H-plane split in a three-wafer stack. This ensures very low surface roughness, in particular on the top and bottom surfaces of the waveguide, without the use of any surface roughness reduction processing steps. This is superior to previous micromachined waveguide concepts, including E-plane and single H-plane split waveguides. The measured average surface roughness is 2.14 nm for the top/bottom of the waveguide, and 163.13 nm for the waveguide sidewalls. The measured insertion loss per unit length is 0.02–0.07 dB/mm for 220–325 GHz, with a gold layer thickness of 1 μm on the top/bottom and 0.3 μm on the sidewalls. This represents, in this frequency band, the lowest loss for any silicon micromachined waveguide published to date and is of the same order as the best metal waveguides.
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| 5. |
- Beuerle, Bernhard, 1983-, et al.
(författare)
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Integrated Micromachined Waveguide Absorbers at 220 – 325 GHz
- 2017
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Ingår i: Proceedings of the 47th European Microwave Conference, Nuremberg, October 8-13, 2017. - 9782874870477 ; , s. 695-698
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Konferensbidrag (refereegranskat)abstract
- This paper presents the characterization of integrated micromachined waveguide absorbers in the frequency band of 220 to 325 GHz. Tapered absorber wedges were cut out of four different commercially available semi-rigid absorber ma terials and inserted in a backshorted micromachined waveguide cavity for characterization. The absorption properties of these materials are only specified at 10 GHz, and their absorption behavior above 100 GHz was so far unknown. To study the effect of the geometry of the absorber wedges, the return loss of different absorber lengths and tapering angles was investigated. The results show that longer and sharper sloped wedges from the material specified with the lowest dielectric constant, but not the highest specified absorption, are superior over other geometries and absorber materials. The best results were achieved for 5 mm long absorbers with a tapering angle of 23° in the material RS-4200 from the supplier Resin Systems, having a return loss of better than 13 dB over the whole frequency range of 220 to 325 GHz. These absorber wedges are intended to be used as matched loads in micromachined waveguide circuits. To the best of our knowledge, this is the first publication characterizing such micromachined waveguide absorbers.
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| 6. |
- Beuerle, Bernhard, 1983-, et al.
(författare)
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Low-Loss Silicon Micromachined Waveguides Above 100 GHz Utilising Multiple H-plane Splits
- 2018
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Ingår i: Proceedings of the 48th European Microwave Conference, Madrid, October 1-3, 2018. - : Institute of Electrical and Electronics Engineers (IEEE). - 9782874870514 ; , s. 1041-1044
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Konferensbidrag (refereegranskat)abstract
- For sub-millimeter and millimeter wave applications rectangular waveguides are an ideal transmission medium. Compared to conventional, metal-milled rectangular waveguides, silicon micromachined waveguides offer a number of advantages. In this paper we present a low-loss silicon micromachined waveguide technology based on a double H-plane split for the frequency bands of 110 – 170 GHz and 220 – 330 GHz. For the upper band a reduced height waveguide is presented, which achieves a loss per unit length of 0.02 – 0.10 dB/mm. This technology has been further adapted to implement a full height waveguide for the lower frequency band of 110 – 170 GHz. The full height waveguide takes advantage of the benefits of the double H-plane split technique to overcome the challenges of fabricating micromachined waveguides at lower frequencies. With measured insertion loss of 0.007 – 0.013 dB/mm, averaging 0.009 dB/mm over the whole band, this technology offers the lowest insertion loss of any D-band waveguide to date. The unloaded Q factor of the D-band waveguide technology is estimated to be in excess of 1600, while a value of 750 has been measured for the reduced height upper band waveguide.
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| 7. |
- Beuerle, Bernhard, 1983-, et al.
(författare)
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On-wafer Micromachined Waveguide Characterization with CPW Probe to Rectangular Waveguide Transition up to 500 GHz
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We report on coplanar waveguide to micromachined waveguide transitions for on-wafer device characterization. The transitions are designed in a silicon micromachined waveguide technology using silicon on insulator wafers together with the devices under test. A previous design at 220–330 GHz with in-band radiation characteristic is modified to eliminate the radiation and allow it to be scaled to higher frequencies. Simulation results for 220–330 GHz and 330–500 GHz are obtained, and the transition has an insertion loss of better than 0.5 and 1.2 dB, respectively. The transition is fabricated and characterized at 220–330 GHz, with an insertion loss of better than 0.7 dB and a return loss in excess of 10 dB over the whole band.
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| 8. |
- Campion, James, 1989-, et al.
(författare)
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An Ultra Low-Loss Silicon-Micromachined Waveguide Filter for D-Band Telecommunication Applications
- 2018
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Ingår i: 2018 IEEE/MTT-S International Microwave Symposium. - : IEEE. - 9781538650677 ; , s. 583-586
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Konferensbidrag (refereegranskat)abstract
- A very low-loss micromachined waveguide bandpassfilter for use in D-band (110–170GHz) telecommunication applicationsis presented. The 134–146GHz filter is implemented in a silicon micromachined technology which utilises a double H-plane split, resulting in significantly lower insertion loss than conventional micromachined waveguide devices. Custom split-blocks are designed and implemented to interface with the micromachined component. Compact micromachined E-plane bends connect the split-blocks and DUT. The measured insertion loss per unit length of the waveguide technology (0.008–0.016 dB/mm) is the lowest reported to date for any micromachined waveguide at D-band. The fabricated 6-pole filter, with a bandwidth of 11.8 GHz (8.4%), has a minimum insertion loss of 0.41 dB, averaging 0.5 dB across its 1 dB bandwidth, making it the lowest-loss D-band filter reported to date in any technology. Its return loss is better than 20 dB across 85% of the same bandwidth. The unloaded quality factor of a single cavity resonator implemented in this technology is estimated to be 1600.
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| 9. |
- Campion, James, et al.
(författare)
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Elliptical alignment holes enabling accurate direct assembly of micro-chips to standard waveguide flanges at sub-THz frequencies
- 2017
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Ingår i: 2017 IEEE MTT-S International Microwave Symposium (IMS). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509063604 ; , s. 1262-1265
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Konferensbidrag (refereegranskat)abstract
- Current waveguide flange standards do not allow for the accurate fitting of microchips, due to the large mechanical tolerances of the flange alignment pins and the brittle nature of Silicon, requiring greatly oversized alignment holes on the chip to fit worst-case fabrication tolerances, resulting in unacceptably large misalignment error for sub-THz frequencies. This paper presents, for the first time, a new method for directly aligning micromachined Silicon chips to standard, i.e. unmodified, waveguide flanges with alignment accuracy significantly better than the waveguide-flange fabrication tolerances, through the combination of a tightly-fitting circular and an elliptical alignment hole on the chip. A Monte Carlo analysis predicts the reduction of the mechanical assembly margin by a factor of 5.5 compared to conventional circular holes, reducing the potential chip misalignment from 46 μm to 8.5 μm for a probability of fitting of 99.5%. For experimental verification, micromachined waveguide chips using either conventional (oversized) circular or the proposed elliptical alignment holes were fabricated and measured. A reduction in the standard deviation of the reflection coefficient by a factor of up to 20 was experimentally observed from a total of 200 measurements with random chip placement, exceeding the expectations from the Monte Carlo analysis. To our knowledge, this paper presents the first solution for highly accurate assembly of micromachined waveguide chips to standard waveguide flanges, requiring no custom flanges or other tailor-made split blocks.
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| 10. |
- Campion, James, 1989-
(författare)
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Exploiting the Terahertz Spectrum with Silicon Micromachining : Waveguide Components, Systems and Metrology
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The terahertz spectrum (300 GHz - 3 THz) represents the final frontier for modern electronic and optical systems, wherein few low-cost, volume-manufacturable solutions exist. THz frequencies are of great scientific and commercial interest, with applications as diverse as radio astronomy, sensing and imaging and wireless communications. Current THz technology is restricted by its expense, form-factor and performance limitations. Future exploitation of this spectrum requires the development of new technologies which support its use in high-volume applications. Any such technology must offer excellent mechanical and electrical performance and be compatible with industrial grade tools and processes. In response to this, this thesis presents the development of silicon micromachined waveguide components and systems for THz and sub-THz frequencies. Silicon micromachining offers a unique combination of small feature sizes and low surface roughness and manufacturing tolerances in a scalable process.At the core of this work lies a new silicon-on-insulator (SOI) waveguide technology which minimises surface roughness to provide low insertion loss. Waveguide filters and diplexers between 100–500 GHz are implemented using this technology, each with state-of-the-art performance. A new platform for waveguide systems is developed to enable fully micromachined systems to be realised. In contrast to previous solutions, this platform integrates of all DC, intermediate and radio frequency signals in a single medium. Two unique non-galvanic transitions provide interfaces to active components and metallic waveguides. Semi-automated industrial tools perform system assembly with high accuracy and are used to implement complete transceivers for wireless communication at 110–170 GHz. Commercial-grade silicon germanium integrated circuits are used for all active components. This represents the first step in the adoption of this new technology in an industrial scenario.Large-scale use of the THz spectrum necessitates a shift from discrete components to complete integrated systems, in a similar matter to that seen in digital electronics and will require accurate, high-throughput characterisation and verification infrastructures. To support this, two transitions from co-planar waveguide probes to rectangular waveguide are proposed to allow for device characterisation in an on-wafer environment from 220–500 GHz. The accuracy and precision of the SOI micromachining process, coupled with the mechanical properties of silicon, make it highly suited to the creation of precision metrology standards. By harnessing these properties, a new class of micromachined waveguide calibration standards is developed, the peformance of which exceeds current solutions. Traceability of the standards is documented through detailed mechanical, electrical and statistcal analysis of fabricated samples.This work presented in thesis enables the development of THz components and systems, and methods to test them, in an established, high-volume technology, enabling their use in a wide range of applications.
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