Planar tunable metamaterials for microwave applications, including matching circuits and leaky wave antennas based on liquid crystals

• Applicants: Professor Dr.-Ing. Christian Damm; Professor Dr.-Ing. Rolf Jakoby
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: from 2010 to 2014
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 167882667

• Final Report Year: 2016

Final Report Abstract

In this work, a liquid crystal based tunable composite right/left-handed leaky wave antenna working at the Ka-Band has been presented. The tuning of the liquid crystal is achieved both by magnetic and electric biasing techniques specifically designed for planar structures. Different prototypes have been designed and manuactured for each biasing technique. For the electric biasing, highly resistive NiCr lines are integrated in the unit cell layout. The tuning of the liquid crystal and comparison of both prototypes has been done by simulation and measurements of the S-parameters, dispersion characteristics and far field patterns. From the obtained S-parameters, the corresponding radiation angles are extracted and a beam scanning range of ±11° at 27 GHz is achieved for the magnetically biased prototype whereas the electrically biased LWA shows an beam scanning of ±16° around the broadside direction at 26.7 GHz. This is confirmed by the far field measurement that shows a beam scanning range of 14° for this frequency. The scanning range is lower in the LHB which limits the ability of the antenna for symmetrical beam scanning. This effect is currently under investigation. As it has been demonstrated, the electric biasing provides similar tuning behaviour as the magnetic one with the advantage of being easily integratable in the unit cell layout. This electric biasing technique can be easily applied to different types of planar voltage tunable components such as leaky wave antennas with continuous beam scanning capability but also tunable phase shifters and filters. Furthermore, this proof-of concept enables higher frequency applications, such as automotive radar at 77 GHz where continuous beam scanning is required. This is possible since the performance of LC increases with frequency. Nevertheless, using IDCs for LWAs at such high frequencies supposes a great technological and time consumig challenge, reason for why the authors strongly recommend the usage of other technologies for future investigations.

Publications

• “Liquid Crystal Based Tunable Composite Right/Left-Handed Leaky-Wave Antenna for Ka-Band Applications”, European Microwave Week 2013
  María Roig, Matthias Maasch, Christian Damm, Onur Hamza Karabey, and Rolf Jakoby
  
• “Planar Metamaterial with Separately Voltage Tunable Electric and Magnetic Dispersion based on Liquid Crystal”, Metamaterials 2013
  Matthias Maasch, María Roig, Christian Damm, and Rolf Jakoby
  
• ”Efficient Farfield Computation from Eigenmode Simulations for Leaky-Wave Antennas”, International Symposium on Antennas and Propagation 2013
  Matthias Maasch, María Roig, Christian Damm, and Rolf Jakoby
  
• ”Steerable Ka-Band Leaky Wave Antenna based on Liquid Crystal Material”, Metamaterials 2013
  María Roig, Matthias Maasch, Christian Damm, and Rolf Jakoby
  
• “Dynamic Beam Steering Properties of an Electrically Tuned Liquid Crystal Based CRLH Leaky Wave Antenna”, Metamaterials 2014
  María Roig, Matthias Maasch, Christian Damm, and Rolf Jakoby
  
• “Electrically Tunable Liquid Crystal Based Composite Right/Left-Handed Leaky-Wave Antenna at 26.7 GHz”, European Microwave Week 2014
  María Roig, Matthias Maasch, Christian Damm, and Rolf Jakoby
  
• ”Liquid Crystal based Tunable CRLH-Transmission Line for Leaky Wave Antenna Applications at Ka-Band”, International Journal of Microwave and Wireless Technologies, International Journal of Microwave and Wireless Technologies, volume 6, issue 3-4, pp. 325-330
  María Roig, Matthias Maasch, Christian Damm, and Rolf Jakoby