Focus Session: THz.NRW

Wednesday, 8:20 – 9:50 in the Room “Zoo Duisburg”

08:20    Introduction to THz.NRW

Dirk Nüßler

Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) | Germany

08:30    Terahertz-Based Non-Contact Vital Sign Measurements

Svenja Nicola Kobel, Christian Wiede, Karsten Seidl

Fraunhofer Institute for Microelectronic Circuits and Systems (IMS) | Germany

As digital health and wearable technologies become increasingly important in society, the demand for non-invasive and convenient monitoring of vital signs has increased significantly. Vital signs play a crucial role in assessing a person’s physiological state and overall health. While traditional contact-based methods have been the norm, recent advances in terahertz technology offer a promising approach for non-contact vital sign measurements. Terahertz technology, situated between microwave and infrared wavelengths, has gained attention due to its ability to penetrate materials such as clothing and biological tissues, making it particularly suitable for contactless measurements. This characteristic positions terahertz technology as an innovative solution for addressing the limitations of traditional vital sign monitoring methods. In this work, terahertz-based reflection measurements are used for the non-contact determination of heart rate and respiratory rate. By utilizing the unique properties of terahertz waves, reflection measurements offer the possibility to precisely measure distances. In this way, the minute movements caused by blood flow during the cardiac cycle and the movements during respiration can be detected. The methodology includes signal processing tailored to the respective vital signs. The measurement points investigated included the finger, wrist, arm bend, and thorax. In an initial pilot study, the method was successfully implemented and demonstrated. The highest accuracy was achieved when measuring the respiratory rate on the thorax, while the arm bend proved most accurate for measuring the heart rate. The results indicate that terahertz waves can accurately detect and monitor changes in heart rate and respiratory rate, representing a promising alternative to conventional methods. This study emphasizes the potential of terahertz technology as a non-invasive and non-contact method of measuring vital signs. The results contribute to the growing body of knowledge that supports the role of terahertz technology in advancing healthcare monitoring modalities.

08:50    MMICs for mm-wave to THz Joint Communication and Sensing (JCS) 

Jan Wessel, Till Stephan Ziegler-Bellenberg, Steffen Hansen, Dominic Funke

Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) | Germany

The increasing demand for smart mobility and a higher degree of automation brings out the strong need for novel concepts on hardware as well as on software and system design site. One promising approach is the combination of sensing and communication to reduce hardware complexity by a higher level of integration and simultaneously maintaining or even increasing functionality. This talk addresses the novel concept of harmonic tag-based joint communication and sensing (JCS) as well as monolithic microwave integrated circuits (MMICs) that provide frequency modulated continuous wave (FMCW) radar functionality and also high data rate communication. A strong focus is set on the ranging accuracy so that the radar key performance is not impaired by the extension with communication features pursuing an assisted radar track. To meet the demands on high resolution ranging as well as high data rate communication, the presented integrated circuits operate in the millimeter to terahertz frequency domain to take advantage of the large bandwidth available. Therefore, the concepts for JCS and their requirements imposed on the MMICs are explored based on three examples operating at 120 GHz, 240 GHz and 300 GHz, respectively. Further aspects regarding sensor fusion for enhanced radar performance or data transmission for identification, status reporting etc. are analyzed.

09:10    A D-Band VNA Frequency Extension Module Based on a Single SiGe MMIC

Justin Romstadt

Ruhr University Bochum | Germany

Current research in the broad academic and industrial communities is enabled by the increasing availability of high-quality measurement technology for the frequency range above 100 GHz. In particular, vector network analysis, which is used to characterize discrete and integrated circuits, systems, antennas, or materials, has an important role. As the frequency range of vector network analyzers (VNAs) is insufficient, vector network analyzer extension modules are needed. Commercially available options consist of discrete components, which increases the size and price of such modules.

Therefore, a compact and cost-effective VNA extension module, which combines most of the functions on a single SiGe-MMIC, will be presented in this presentation. The talk will include design considerations of the whole system and single components integrated into the MMIC. To demonstrate the functionality of the module, a comparison with a state-of-the-art extension module based on measurements of different DUTs will also be shown. Here, the focus lies on the dynamic ranges, magnitude- and phase stability and identified problems and limitations of the innovative design approach.

09:30    Mobile Terahertz Spectroscopy Systems Enabled by Mode-Locked Laser Diodes

Kevin Kolpatzek

University of Duisburg-Essen, Chair of Communication Systems (NTS) | Germany

Modern fiber-coupled terahertz time-domain spectroscopy (THz-TDS) systems have found widespread use in fundamental research and are currently finding their way into real-world applications. However, their bulk, weight, and power consumption make them suitable only for stationary applications. One way to overcome this limitation is the replacement of the fiber laser that is at the heart of the THz-TDS system with a suitable semiconductor light source. Although first solutions based on multi-mode laser diodes have been demonstrated as early as 1999, their bandwidth and dynamic range leave a lot to be desired.

More recently, it was shown that monolithic mode-locked laser diodes (MLLDs) can be used for the same application. A key characteristic of a THz-TDS system that is driven by an MLLD is its unusually high pulse repetition rate of several 10 GHz. We now call this approach ultra-high repetition terahertz time-domain spectroscopy (UHRR-THz-TDS). Through careful system analysis, leading to several innovations in system design and signal processing, we are now able to construct mobile shoebox-sized UHRR-THz-TDS systems with a peak dynamic range in excess of 100 dB, and we see first promising results for achieving spectral update rates of several 100 spectra per second.

This talk gives an overview of the state of the art in UHRR-THz-TDS, compares it to other measurement techniques in the terahertz frequency range, and discusses promising new applications.