THz MEMS - micromachining enabling the large-scale exploitation of the millimeter and submillimeter-wave frequency spectrum


Since RF MEMS switches appeared more than 20 years ago, micromachining and micromechanics have been receiving large attention for enabling microwave devices with near-ideal electrical performance. MEMS switches and MEMS-switch based circuits have been through different development stages and are currently proving themselves commercially, among others for mobile-phone antenna-tuners. However, micromachining can do much more than “just” two-dimensional MEMS switches for planar transmission-line technology: Three-dimensional, deep-silicon micromachining allows for new microwave devices with unprecedented performance due to the excellent fabrication tolerances down to 1 um, and the very low surface roughness achieving very low loss perfoance. Therefore, this technology has the potential to become an enabling technology for volume-manufacturable, reconfigurable submillimeter-wave and THz systems. This paper provides an overview of 3D silicon micromachining capability and reviews the state of the art of micromachined-waveguide systems up to 2.9 THz. The main focus of the talk is on recent achievements in 3-D micromachined millimeter and submillimeter-wave devices and systems at KTH Royal Institute of Technology, Stockholm, Sweden. The talk presents the first MEMS-reconfigurable submillimeter-wave components, in particular a 3.3 bit MEMS phase shifter and a low-insertion loss / high-isolation MEMS waveguide switch operating at 500-750 GHz. Furthermore, a micromachined technology for very-low loss, high-complexity, multi-mode filters with transmission-zeros is presented, enabled by resonators with unloaded Q factors of 800 in the 220-330 GHz band. An example of a 1.85% fractional bandwith, 4-pole, 2-transmission-zero filter at 270 GHz achieved an insertion loss as low as 1.25 dB. Filters and diplexers for telecommunication-link applications in the 110-170 GHz are presented as well achieving unloaded Q-factors of 1600. Furthermore, a very low loss micromachined waveguide technology is presented, having only 0.02 dB/mm loss in the 220-330 GHz band, and 0.008 dB/mm in the 110-170 GHz band. This, to the best of our knowledge currently lowest-loss micromachined waveguide technology enabled a range of very-low loss waveguide components such as couplers, power combiners/splitters, and micromachined-waveguide integrated matched loads for multi-port devices presented in the talk. More complex components such as OMTs at 220-330 GHz, and integrated micromachined absorbers and loads for multi-port components will also be shown.

Short bio:

Joachim Oberhammer, born in Italy in 1976; M.Sc. EE from Graz University of Technology, Austria, in 2000; Ph.D. from KTH Royal Institute of Technology in Stockholm, Sweden, in 2004. Post-doctoral research fellow at Nanyang Technological University, Singapore, in 2004, and at Kyoto University, Japan, in 2008. Since 2005 leading radio-frequency/microwave/terahertz micro-electromechanical systems research at KTH; Associate Professor at KTH in 2010; Professor in Microwave and THz Microsystems at KTH since 2015. Guest researcher at Nanyang Technological University, Singapore, in 2007; guest researcher at NASA-Jet Propulsion Laboratory, USA, in 2014.

He is author and co-author of more than 100 reviewed research papers and holds 4 patents. In 2004, 2007, and 2008 he got an award by the Ericsson Research Foundation, a grant by the Swedish Innovation Bridge, and a scholarship by the Japanese Society for the Promotion of Science, respectively. The research work he is heading received six Best Paper Awards (five of which at IEEE conferences), and five IEEE Graduate Fellowship Awards (by MTT-S and by AP-S) since 2009. He served as TPRC member of IEEE Transducers 2009 and 2015, IEEE International Microwave Symposiums 2010-2017, IEEE Micro Electro Mechanical Systems 2011 and 2012, and IEEE Radio and Wireless Week 2015 and 2016. Dr Oberhammer is Steering Group member of the IEEE MTT-S and AP-S Chapers Sweden since 2009. In 2013, he received an ERC Consolidator Grant by the European Research Council. Since 2014 he is Steering Group Member of the Young Academy of Sweden. Since 2016 he is member of the General Assembly of the European Microwave Association.