Multipactor ...

tipactor, Corona Discharge and passive intermodulation

Prof. Dr. Eng. Dr. h. c. mult H. L. Hartnagel

Dr. Ing. B. Nicolae

Dipl. Ing. D. Schönherr

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Non-linear electron effects in satellite systems gain importance for the development of modern multiplexer systems. Parasitic effects like passive intermodulation, corona discharge or multipacting decrease the channel performance or even disturb single channels or the entire satellite system. The modeling of these effects and their integration in design tools is a very challenging task in the framework of several projects.

Under several EU and ESA projects, software is being developed for the prediction of these phenomena. In particular, Passive Intermodulation in waveguide connections as well as the corona discharge and multipactor thresholds in rectangular-waveguide based microwave components like filters or resonators are being investigated.

Passive intermodulation occurs when a non-linear component in the system excite frequencies closed to the original ones. This is critical in Sat-com due to the power level difference between the outcoming and the incoming signals. In the case of waveguide junctions, the PIM level level is excited due to the presence of a contact resistance which results in a non-linear I-V characteristic.

Multipactor occurs in vacuum conditions similar to those present in the normal functioning of a satellite. It originates due electrons crashing into the metallic surfaces of a device. If resonant conditions between the electromagnetic field and the electrons are fullfilled an avalanche can start if the electric field is so high that the electrons are accelerated to energies that can extract electrons from the device walls.

Corona Discharge is a process consisting in the formation of an electron plasma due to the ionisation of the gas surrounding a zone of high electric field. In normal life one can see this phenomenon in lightnings or in the mast of a ship in a stormy day (St. Elmo's fire). Regarding milimeter-microwave technology, this phenomenon occurs, for instance, in waveguide filters where the high electric field reached is capable to ignite Corona for relatively low pressures (0.1-100 mBar). Corona normally occurs at intermediate-pressure levels (between 1 and 30 mbars) which, in atmospheric terms, comprises the Ionosphere (60 to 800 Km height).

Veröffentlichungen / Relevant Publications:

  • C. Vicente, B. Mottet and H.L. Hartnagel: PIM Analysis at Waveguide Flanges: A Theoretical Approach. 4th International Workshop in Multipactor, Corona and Passive Intermodulation in Space RF Hardware, 8-11 September 2003, ESTEC, Noordwijk, The Netherlands
  • C. Vicente, A. Cervello, B. Mottet, H. L. Hartnagel, M. Mattes, J. Mosig, D. Wolk and D. Raboso, AO-4026 ITT ESA – Multipactor and Corona discharge: Simulation and Design in Microwave Components. 4th International Workshop in Multipactor, Corona and Passive Intermodulation in Space RF Hardware, 8-11 September 2003, ESTEC, Noordwijk, The Netherlands
  • J. Gil, C. Vicente, M. Mattes, H.L. Hartnagel, J. Mosig and B. Casali: Integration of PIM in FEST 3.0. 4th International Workshop in Multipactor, Corona and Passive Intermodulation in Space RF Hardware, 8-11September 2003, ESTEC, Noordwijk, The Netherlands
  • D. Wolk, J. Damaschke, C. Vicente, B. Mottet, H.L. Hartnagel, L. Galan, M. Alfonseca and D. Raboso: AO-4025 ITT ESA – Surface Treatment and Coating for the Reduction of Multipactor and Passive Intermodulation (PIM) Effects in RF Components. 4th International Workshop in Multipactor, Corona and Passive Intermodulation in Space RF Hardware, 8-11 September 2003, ESTEC, Noordwijk, The Netherlands
  • C. Vicente: Intermodulation at waveguide flanges. Minor thesis, June 2002, University of Valencia, Spain
  • C. Vicente, D. Wolk, H.L: Hartnagel, B. Gimeno, V.E. Boria and D. Raboso. Experimental Analysis of Passive Intermodulation at Waveguide Flange Bolted Connections – In IEEE Transactions on Microwave Theory and Techniques, 2007. Vol. 55 no. 5 pages 1018-1028 May