International Journal of Terahertz Science and Technology
  TST >> Vol.6, No.4, December 2013: PP. 212-222
 

(Invited paper) Multi-frequency notch filters and corrugated 200 to 400 GHz waveguide components manufactured by stacked ring technology

M. Thumm 1*, D. Wagner 2, E. de Rijk 3, W. Bongers 4, W. Kasparek 5, F. Leuterer 2, A. Macor 3, J.-Ph. Ansermet 6, F. Monaco 2, M. Münich 2, H. Schütz 2, J. Stober 2, H. v.d. Brand 4, and A.v. Bieren 3
1 Karlsruhe Institute of Technology (KIT), IHM and IHE, Karlsruhe, Germany
2 Max-Planck-Institut für Plasmaphysik (IPP), EURATOM-IPP, Garching, Germany
3 SWISSto12 SA, Science Park - EPFL, Lausanne, Switzerland
4 Dutch Institute for Fundamental Energy Research, EURATOM-DIFFER, Nieuwegein , Netherlands
5 Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie (IGVP) , Universität Stuttgart, Germany
6 Laboratoire de Physique des Matériaux Nanostructurés, EPFL, Lausanne, Switzerland
*1 Email: manfred.thumm@kit.edu

View Full Text: PDF

Abstract: Sensitive millimeter wave diagnostics need often to be protected against unwanted radiation like, for example, stray radiation from high power Electron Cyclotron Heating applied in nuclear fusion plasmas. A notch filter based on a waveguide Bragg reflector (photonic band-gap) may provide several stop bands of defined width within up to two standard waveguide frequency bands. A Bragg reflector that reflects an incident fundamental TE11 into a TM1n mode close to cutoff is combined with two waveguide tapers to fundamental waveguide diameter. Here the fundamental TE11 mode is the only propagating mode at both ends of the reflector. The incident TE11 mode couples through the taper and is converted to the high order TM1n mode by the Bragg structure at the specific Bragg resonances. The TM1n mode is trapped in the oversized waveguide section by the tapers. Once reflected at the input taper it will be converted back into the TE11 mode which then can pass through the taper. Therefore at higher order Bragg resonances, the filter acts as a reflector for the incoming TE11 mode. Outside of the Bragg resonances the TE11 mode can propagate through the oversized waveguide structure with only very small Ohmic attenuation compared to propagating in a fundamental waveguide. Coupling to other modes is negligible in the non-resonant case due to the small corrugation amplitude (typically 0.05·λ0, where λ0 is the free space wavelength). The Bragg reflector was optimized by mode matching (scattering matrix) simulations and manufactured by SWISSto12 SA, where the required mechanical accuracy of ± 5 μm could be achieved by stacking stainless steel rings, manufactured by micro-machining, in a high precision guiding pipe (patent is pending). The two smooth-wall tapers were fabricated by electroforming. Several measurements were performed using vector network analyzers from Agilent (E8362B), ABmm (MVNA 8-350) and Rohde&Schwarz (ZVA24) together with frequency multipliers. The stop bands around 105 GHz (-55 dB) and 140 GHz (-60 dB) correspond to the TE11-TM12 and TE11-TM13 Bragg resonances. Experiments are in good agreement with theory. The stacked rings technology has also been employed for manufacturing of oversized (I.D. = 15 mm) corrugated waveguides (propagating the balanced HE11 hybrid mode). The waveguides are for use in a 4 m long transmission line for Dynamic Nuclear Polarization Nuclear Magnetic Resonance applications in the 200 to 400 GHz band. A high performance flange connection system between the modules allows for modular path building. To validate the performance of the proposed system, a detailed characterization of all corrugated waveguide components has been performed using a Vector Network Analyzer operating in the 220 to 330 GHz range.

Keywords: Electron cyclotron heating, Gyrotrons, Plasma diagnostics, Bragg reflector notch filter, Dynamic nuclear polarization, Oversized Terahertz HE11-mode transmission line, Stacked rings manufacturing technology.

Received: 2013-11-30

Published: 2013-12-30

Cite this article:
M. Thumm, D. Wagner, E. de Rijk, W. Bongers, W. Kasparek, F. Leuterer, A. Macor, J.-Ph. Ansermet, F. Monaco, M. Münich, H. Schütz, J. Stober, H. v.d. Brand, and A.v. Bieren.(Invited paper) Multi-frequency notch filters and corrugated 200 to 400 GHz waveguide components manufactured by stacked ring technology[J]. International Journal of Terahertz Science and Technology, 2013, Vol.6, No.4: 212-222.  DOI:10.11906/TST.212-222.2013.12.15

URL: http://www.tstnetwork.org/10.11906/TST.212-222.2013.12.15

 

 
 

Print | close

Copyright© 2008 Scinco Inc. All Rights Reserved
P.O.Box 6982, Williamsburg, VA 23188, USA var cnzz_protocol = (("https:" == document.location.protocol) ? "https://" : "http://");document.write(unescape("%3Cspan id='cnzz_stat_icon_2409046'%3E%3C/span%3E%3Cscript src='" + cnzz_protocol + "s4.cnzz.com/stat.php%3Fid%3D2409046%26show%3Dpic' type='text/javascript'%3E%3C/script%3E"));