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Compact silicon-micromachined wideband 220 – 330 GHz turnstile orthomode transducer
KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.ORCID iD: 0000-0002-8894-7930
KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.ORCID iD: 0000-0002-8264-3231
KTH, School of Electrical Engineering and Computer Science (EECS), Micro and Nanosystems.ORCID iD: 0000-0003-3339-9137
2018 (English)In: IEEE Transactions on Terahertz Science and Technology, ISSN 2156-342X, E-ISSN 2156-3446, Vol. 9, no 1, p. 38-46, article id 8542680Article in journal (Refereed) Published
Abstract [en]

This paper reports on a turnstile-junction orthomode transducer (OMT) implemented by silicon micromachiningin the 220 – 330 - GHz band. Turnstile OMTs are very widebandand allow for co-planar ports, but require accurate and complex geometries which makes their fabrication challenging at higher frequencies. The compact 10 mm x 10 mm x 0.9 mm OMT-chip presented in this paper is the first micromachined full-band OMT in any frequency range, and only the second turnstile OMT implemented above 110 GHz. The measured insertion loss(0.3 dB average, 0.6 dB worst-case) and the cross-polarization (60 dB average, 30 dB worst-case) over the whole waveguide band represent the best performance of any wideband OMT, regardless of design or fabrication technology, in the 220 –330 - GHz band. The return loss with 22 dB average (16 dB worst case) is comparable or better than previous work. The paper discusses design considerations and compromises of this complex 9 layer silicon micromachined device, including the influence of sidewall slopes, underetching, and post-bonding misalignment between the chips. It is shown that for a device which is very sensitive to geometrical variations, such as a turnstile OMT, it is necessary to anticipate and compensate for any fabrication imperfections in the design to achieve high RF performance.

Place, publisher, year, edition, pages
IEEE, 2018. Vol. 9, no 1, p. 38-46, article id 8542680
Keywords [en]
OMT, orthomode transducer, turnstile, silicon micromachining, DRIE, MEMS, millimeter wave, mmW, terahertz, THz
National Category
Telecommunications
Research subject
Electrical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-239727DOI: 10.1109/TTHZ.2018.2882745ISI: 000455919800004Scopus ID: 2-s2.0-85057820646OAI: oai:DiVA.org:kth-239727DiVA, id: diva2:1267249
Funder
Swedish Foundation for Strategic Research , SE13-007EU, Horizon 2020, 616846
Note

QC 20181217

Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2020-05-13Bibliographically approved
In thesis
1. Submillimeter-Wave Waveguide Frontends by Silicon-on-Insulator Micromachining
Open this publication in new window or tab >>Submillimeter-Wave Waveguide Frontends by Silicon-on-Insulator Micromachining
2020 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents novel radiofrequency (RF) frontend components in the submillimeter-wave (sub-mmW) range implemented by silicon micromachining, or deep reactive ion etching (DRIE). DRIE is rapidly becoming a driving technology for the fabrication of waveguide components and systems when approaching the terahertz (THz) frequency range. The conventional method to manufacture microwave waveguide components, CNC-milling, shows important limitations when used at sub-mmW frequencies or above, due to the reduced size of the waveguides. At the same time, the classic electromagnetic designs, oriented to CNC-milling, are often not suitable for their fabrication using alternative technologies. The work in this thesis aims to develop fabrication-oriented electromagnetic structures, making use of the full flexibility of silicon on insulator (SOI) micromachining, and enabling the implementation of complex RF frontends at a low fabrication complexity.

The first part of the thesis reports on a turnstile orthomode transducer (OMT) in the WM-864 band (220 – 330 GHz). OMTs are key components in the feed-chain for radio astronomy, communications, or radiometry applications. However, their complex geometry has often limited their use when approaching the THz range, where polarization diversity is commonly avoided, or optical systems are preferred.

The second part reports on a high-gain and broadband waveguide corporatefed array antenna in the WM-570 band (330 – 500 GHz). High gain and broadband antennas are required for the future generation of THz wireless communications. Reflector and lens antennas can meet these specifications, but their fabrication for the THz range requires precision machining, resultingin a high cost, low yield, and small scale production. The use of silicon micromachined antenna arrays overcomes these issues while providing a more compact frontend.

In the third part of the thesis, a parallel plate waveguide (PPW) leaky wave antenna (LWA) fed by a quasi-optical beamforming network (BFN) in the WM-864 band is presented. The antenna frontend generates a pencil shaped beam scanning in elevation. The compact design, large bandwidth, and beam steering capabilities make this antenna a suitable frontend for THz radar applications.

The final part of this thesis reports on a novel waveguide single pole double throw (SPDT) switch in the WM-570 band. The switch is demonstrated in a two-port network configuration with two switching states (ON/LOAD), used for receiver calibration, or for avoiding backward waves in transmitter switching. A more complex 1×4 switching matrix is also designed for the implementation of an active radar antenna operating at 340 GHz.

Abstract [sv]

Denna avhandling presenterar nya radio frekvens (RF) frontend komponenter inom submillimeter våg (sub-mmW) bandet som kan implementeras med mikrofabrikationsteknik i kisel samt djup reaktiv jonetsning (DRIE). DRIE är en snabbt växande teknik som har blivit drivande för fabrikation av vågledarkomponenter och system som angränsar terrahertz (THz) frekvensbandet. Den konventionella tillverkningsmetoden för vågledarkomponenter, CNC-fräsning, påvisar stora begränsningar vid användning för sub-mmW bandet eller högre, på grund av de små dimentionerna av vågledarkomponenterna. Samtidigt är de klassiska elektomagnetiska konstruktionerna, som ofta är orienterade mot CNC-fräsning, inte lämpade för alternativa tillverkningsmetoder. Syftet med denna avhandling är att utveckla tillverknings orienterade strukturer genom att använda flexibiliteten av silicon on insulator (SOI) mikrofabrikationsteknik och att möjliggöra implementeringen av komplexa RF frontend med en låg tillverkningskomplexitet.

Den första delen av avhandlingen redogör för turnstile orthomode omvandlare (OMT) i WM-864 bandet (220 - 330 GHz). OMT är nyckelkomponenter i feedchain till radioastronomi, kommunikation och radiometritillämpningar. Likväl, har deras komplexa geometri ofta begränsat deras användning när THz bandet angränsas, där polariserings diversitet typiskt undviks, eller optiska systems är att föredra.

Den andra delen redogör för högvinst-, och bredbands,- parallellmatad arrayantenn i WM-570 vågledarteknologi (330 - 500 GHz). Högvinst- och bredbandsantenner behövs för den kommande generationens trådlösa THz kommunikation. Reflektor- och linsantenner kan uppfylla dessa specifikationer men deras tillverkning i THz bandet kräver mycket precis skärande bearbetning, vilket resulterar i höga kostnader, låg avkastning, och småskalig tillverkning. Genom användning av kisel mikrofabrikationstillverkade arrayantenner är det möjligt att övekomma sådana problem och samtidigt tillhandahålla en mer kompakt frontend.

I den tredje delen av denna avhandling presenteras en parallelplats-vågledar- (PPW) läckande-våg-antenn (LWA) matad av kvasi-optiska strålformande nätverk (BFN) i WM-864 bandet. Denna antenn-frontend genererar en pennformad strålskanning i elevations riktningen. Den kompakta utformningen, stora bandbredden, och strålstyrningsmöjligheterna gör denna antenn väl anpassad för THz radar tillämpningar.

Den sista delen i avhandlingen beskriver en ny vågledar-, single pole double throw (SPDT)-, omkopplare i WM-570 bandet. Omkopplaren påvisas i en tvåports- nätverkskonfiguration med två växlar (ON/LOAD) som används för mottagarkalibrering, eller för att undvika bakåtgående vågor i sändarväxlingen. En mer komplex 1 x 4 växlingsmatris utformas även för implementeringen av en aktiv antenn för en radar som opererar i 340 GHz.

Place, publisher, year, edition, pages
Stockholm: Kungliga Tekniska högskolan, 2020. p. 131
Series
TRITA-EECS-AVL ; 2020:28
Keywords
antenna, orthomode transducer, switch, waveguide, radiofrequency, beamforming network, submillimeter-wave, terahertz, silicon micromachining, deep reactive ion etching, silicon on insulator
National Category
Telecommunications
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-273332 (URN)978-91-7873-528-0 (ISBN)
Public defence
2020-06-12, https://kth-se.zoom.us/webinar/register/WN_CnNPt8geTBq7R54VGrXBVA, Stockholm, 16:00 (English)
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Supervisors
Note

QC 20200515

Available from: 2020-05-15 Created: 2020-05-13 Last updated: 2020-06-02Bibliographically approved

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