NTPNetzwerk

Technische Partner

LISAES – EVALUATING LIQUID CRYSTALS AS PHASE SHIFTERS IN A DIRECT RADIATING HORN ARRAY ANTENNA (ISL KA-BAND)

Investigations for electric beam forming / steering of the LISA lightweight intersatellite link antenna

Baseline: LISAMS Mechanical antenna steeringIncl. 2-channel, low loss waveguide rotary joint

LISAES 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: 1Technische Universität München - Lehrstuhl für Raumfahrttechnik (U.Walter) / Leichtbau (S.Endler, H.Baier), 2Netzwerk Technische Partner, 3Airbus Defence and Space, 4Technische 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 LISAES) und H. Ultes (FKZ 50YP1333 LISAMS)

Vision: LISAES Electrical steering through beam forming using liquid crystal phase shifters

16x16 GEO horn array antenna, septum OMT (LHC, RHC) und

512 LC-phase shifters

Smallestr (typ. 2.46)

Largestr (typ. 3.18)

Phase Shifter Characterization:

LISAES 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 Hoehn1, Matthias Tebbe1, Norbert Nathrath2, Michael Trümper2 , Ralf Gehring3, Helmut Wolf3 , Christian Weickhmann4

38th 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-bandWith 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) 50m 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

LISAMS

LISAES

Temperature dependency of transmission losses

Temperature dependency to complete 360° ‘jump’

Time to steady state at room temperature