NTP Netzwerk Technische Partner LISA ES – EVALUATING LIQUID CRYSTALS AS PHASE SHIFTERS IN A DIRECT RADIATING HORN ARRAY ANTENNA (ISL K A -BAND) Investigations for electric beam forming / steering of the LISA lightweight intersatellite link antenna Baseline: LISA MS Mechanical antenna steering Incl. 2-channel, low loss waveguide rotary joint LISA ES additional publications and information: • Proceed.,IEEE Aerospace Conference 2013: Design Characterization of an Electronic Steerable Ka-Band Antenna Using Liquid Crystal Phase Shifters. • 43rd European Microwave Conference, 2013: A Light-Weight Tunable Liquid Crystal Phase Shifter for an Efficient Phased Array Antenna. • Electronics Letters 2013: Recent measurements of compact electronically tunable liquid crystal phase shifter in rectangular waveguide topology. • Proceedings, IEEE Aerospace Conference 2016: Simulation of an Electronically Steerable Horn Antenna Array with Liquid Crystal Phase Shifters. • Proceedings, 2017 IEEE Aerospace Conference: Manufacturing and Testing of Liquid Crystal Phase Shifters for an Electronically Steerable Array. Thanks to our consortium partners: 1 Technische Universität München - Lehrstuhl für Raumfahrttechnik (U.Walter) / Leichtbau (S.Endler, H.Baier), 2 Netzwerk Technische Partner, 3 Airbus Defence and Space, 4 Technische Universität Darmstadt–Institut für Mikrowellentechnik und Photonik (A.Gaebler, R.Jakoby), Hochschule München (D.Fasold, G.Strauss), IMST GmbH, Kamp-Linfort (M.Geisletr, M.Wleklinski, L.Wunderlich), Ingenieurbüro Letschnik (J.Letschnik). Merck KGaA, Darmstadt (proprietary high frequency Liquid Crystal mixtures). Precision milling / manufacturing GEWO Feinmechanik - Wörth-Hörlkofen and Markl Feinmechanische Werkstätten - Oberhaching, Galvanic by GalvanoT - Windeck/Sieg. Funded by DLR Raumfahrtmanagement, S.Voigt (FKZ 50YP1113 LISA ES ) und H. Ultes (FKZ 50YP1333 LISA MS ) Vision: LISA ES Electrical steering through beam forming using liquid crystal phase shifters 16x16 GEO horn array antenna, septum OMT (LHC, RHC) und 512 LC-phase shifters Smallest r (typ. 2.46) Largest r (typ. 3.18) Phase Shifter Characterization: LISA ES LC-phase-shifter based steering status: • Fundamental manufacturability and functionality demonstrated • Complex and high risk integrated phase shifter manufacturing challenges remain (vacuum, thermal expansion, robustness) • Large number of components (16 x 16 array = 512 P/S for two polarizations) • Still high losses in E-field electronics (power electronics) and phase shifters (RF-power) • Slow rate of change due to required phase ‚jumps‘, partially compensated due to optimization strategies 4x4 Array Demonstrator (w/o phase shifters) Liquid crystal (LC) – based phase shifter (P/S - working principle: • Controlled LC-orientation (E-field or H-field) affects r • Phase shift of 400° per 10 cm LC-cavity • Individual phase shifters in each waveguide pathway to each horn • Using film electrodes (±165 VAC) to generate variable E-field direction within P/S Liquid-Crystal filled phase shifters in waveguide distribution network Alexander Hoehn 1 , Matthias Tebbe 1 , Norbert Nathrath 2 , Michael Trümper 2 , Ralf Gehring 3 , Helmut Wolf 3 , Christian Weickhmann 4 38 th ESA Antenna Workshop on Innovative Antenna Systems and Technologies for Future Space Missions, 3-6 October 2017, Noordwijk, The Netherlands 8x8 LEO horn array antenna, septum OMT (LHC, RHC), low loss waveguide / rotary joint, mechanical / fast 2-axis steering Dynamic +/- 11° electric beam forming Obtaining required phase shift for GEO to LEO (± 11 ) application: Need approx. 2,700 phase shift for 40 x 40 cm LISA array in Ka-band With only 400 per P/S, use multiple phase numbers (7 – 8) P/S components: • LC-cavity (Rexolite) with thermal expansion / fill ports • Two (top, bottom) 50 m Kapton film electrodes with high impedance Titanium-electrodes, each with two supply wires and internal voltage divider • Used in split block (testing) or integrated with electroplated skin and flanges RF-pattern test with 4x1 horn row and 9° commanded shift Phase shift (steady state, dynamic) vs. applied voltage Losses and rate of change of phase shift vs. voltage and temperature ‘phase number jump’ optimization: modelled losses during LEO satellite tracking without (top) Losses with ‘jump’ optimization during ½ LEO orbit pass Losses w/o optimization Printed voltage divider LISA MS LISA ES Temperature dependency of transmission losses Temperature dependency to complete 360° ‘jump’ Time to steady state at room temperature