Project S01 - High-Speed Beamforming Concepts for THz Frequencies

Principal Investigator: Prof. Dr. Andreas Czylwik, UDE; Prof. Dr. Anna Lena Schall-Giesecke, UDE/IMS; Dr. Lisa Schmitt, RUB

Achieved results and methods

With respect to multi-source extremely wideband transmit beamforming concepts, different types of non-equidistant linear arrays had been compared. Simulation results show the possibility of a trade-off between a high angular resolution and low sidelobe level as can be seen below. The used spatial distributions of individual antennas are taken from [25,26].

During the 2nd phase of MARIE, prototypes of the MEMS reflectarray (Fig. 2b) were designed, fabricated, and characterized. As shown in Fig. 2a, each actuator system needs to perform a defined, individual, and stepwise displacement of the reflector. C12 realized a step-by-step micro-actuator [5] and an actuator based on a micro-mechanical digital-to-analog converter (M-DAC, Fig. 5) [4] with a maximum displacement of 234.5 µm, addressing a maximum of 27 individual positions. A detailed description is presented in section C12.3.1. The reflector thickness of 300 µm is realized by combining the device and handle layer of an SOI substrate [1]. A deep-reactive-ion etching process was developed to open an interface for the reflector which steers the THz wave. So, the reflector and the actuator system provide excellent preconditions for functionality from the MEMS- and HF-point of view.

Strategies for beamforming with a MEMS reflectarray have been analyzed theoretically by simulations which promised beamforming versus a wide frequency range and wide angle of deflection. It was shown that a height pattern optimized by a genetic algorithm shows a better performance than an optimized "blazed grating" known from [27]. To demonstrate the performance practically and to compare practical results with theory, a fixed (non-controllable) reflectarray consisting of silicon plates with optimized height pattern has been fabricated in project C12 as shown in Fig. 6.

The performance of the described reflectarray has been demonstrated by both, simulations and measurements of a static array which - as an example - has been optimized for a carrier frequency of 300 GHz and steering angles of 56.4° and 41.8°, respectively. The frequency-dependent radiation patterns are shown in Fig. 7 [2].

Key system demonstration

Within MARIE S01 a compact terahertz TDS system driven by a mode-locked laser diode has been developed. Furthermore, terahertz spectrum broadening by shaping the spectrum of a mode-locked laser has been demonstrated experimentally: A significant power gain at high frequencies could be achieved.

Selected project-related publications

  1. Schmitt, X. Liu, P. Schmitt, A. Czylwik, M. Hoffmann: Large Displacement Actuators With Multi-Point Stability for a MEMS-Driven THz Beam Steering Concept, In: IEEE Journal of Microelectromechanical Systems, 2023, [DOI: 10.1109/JMEMS.2023.3236145]
  2. Liu, L. Schmitt, B. Sievert, J. Lipka, C. Geng, K. Kolpatzeck, D. Erni, A. Rennings, J. C. Balzer, M. Hoffmann, A. Czylwik: Terahertz Beam Steering Using a MEMS-Based Reflectarray Configured by a Genetic Algorithm, IEEE Access, vol. 10, 2022, pp. 84458-84472 [DOI: 10.1109/ACCESS.2022.3197202.org]
  3. Liu, L. Samfaß, K. Kolpatzeck, L. Häring, J. C. Balzer, M. Hoffmann, A. Czylwik: Terahertz beam steering concept based on MEMS-reconfigurable reflection grating, Sensors, vol 20, 2020 [DOI: 10.3390/s20102874]
  4. Schmitt, P. Schmitt, M. Hoffmann: 3-Bit Digital-to-Analog Converter with Mechanical Amplifier for Binary Encoded Large Displacements, In: Actuators MDPI, 10, 182, 2021, [DOI: 10.3390/act10080182]
  5. Schmitt, M. Hoffmann: “Large Stepwise Discrete Microsystem Displacements Based on Electrostatic Bending Plate Actuation,” Actuators MDPI, 10(10), 272, 2021, [DOI: 10.3390/act10100272.org]
  6. Schmitt, P. Conrad, A. Kopp, C. Ament, M. Hoffmann: Non-Inchworm Electrostatic Cooperative Micro-Stepper-Actuator Systems with Long Stroke, Actuators, MDPI, 2023, 12(4), 150, [DOI: 10.3390/act12040150]
  7. Schmitt, Ph. Schmitt, M. Hoffmann: Highly Selective Tilted Triangular Springs with Constant Force Reaction, Sensors 2024, 24(5), 1677, [DOI: 10.3390/s24051677]
  8. Jiménez-Sáez, A. Alhaj-Abbas, M. Schüßler, A. Abuelhaija, M. El-Absi, M. Sakaki, L. Samfaß, N. Benson, M. Hoffmann, R. Jakoby, T. Kaiser, K. Solbach: “Frequency-Coded mm-Wave Tags for Self-Localization System Using Dielectric Resonators”, J. Infrared Millim. Terahertz Waves, Vol. 41, 908–925(2020), [DOI: 10.1007/s10762-020-00707-0]
  9. Kadera, J. Sánchez-Pastor, L. Schmitt, M. Schüßler, R. Jakoby, M. Hoffmann, A. Jiménez-Sáez, J. Lacik: Sub-THz Luneburg lens enabled wide-angle frequency-coded identification tag for passive indoor self-localization, In: International Journal of Microwave and Wireless Technologies, pp. 1 – 15, 2022, [DOI: 10.1017/S175907872200054X]
  10. Liu, K. Kolpatzeck, L. Häring, J. C. Balzer, A. Czylwik: “Wideband beam steering concept for terahertz time-domain spectroscopy: Theoretical considerations”, Sensors, vol 20, 2020 [DOI: 10.3390/s20195568]