[1] Univ Publ Navarra, Dept Elect & Elect Engn, E-31006 Navarra, Spain
[2] Univ Limoges, XLIM, CNRS, UMR 6172, F-87060 Limoges, France
[3] Univ Bern, Inst Appl Phys, CH-3012 Bern, Switzerland
[4] Rutherford Appleton Lab, STFC, Millimetre Wave Technol Grp, Didcot OX11 0QX, Oxon, England
[5] European Space Res & Technol Ctr ESTEC, European Space Res & Technol Ctr, Electromagnet Div, NL-2201 AG Noordwijk, Netherlands