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Item type:Publication, Access status: with files , Powering mobile sensor nodes in fluidized beds: A non-invasive RF energy harvesting proof-of-concept(American Chemical Society (ACS), 2026-10-16); ; ; ; Real-time monitoring within industrial processing vessels is essential for advancing process analytical technology. Flow-following sensors represent an ideal approach for delivering continuous, in-line data from the process stream. However, deploying these mobile sensors is constrained by the physical barriers of sealed metallic vessels and harsh, battery-hostile environments. To overcome these limitations, a non-invasive, retrofittable wireless power transfer system is presented. The metallic vessel is structurally repurposed into a 5.23 GHz multi-mode microwave cavity resonator by coupling microwave energy through existing standard flanges. Electromagnetic simulations validate that this method generates continuous energy coverage throughout dynamic flow zones, demonstrated using a fluidized bed granulator as an application example. To harness this energy, an omnidirectional antenna and a compact RF-to-DC rectifier prototype were developed. By enabling the continuous operation of autonomous, battery-free mobile sensor nodes, this framework provides a practical, scalable foundation for high-density spatial analytics and data-driven industrial optimization.Publicationtype: Journal Article18 9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Design and validation of a compact radio frequency measurement system for volumetric near-field scansThis work presents a modular near-field (NF) measurement system derived from the open-source 3-D printer project RatRig V-Core 3.1. Rather than requiring individual solutions for specific measurement tasks, the system at hand serves as a centralized measurement platform for a wide range of planar and volumetric measurements. It enables automated measurements in a controlled environment with a working volume of 510 × 450 × 910mm. Concepts from Cartesian 3-D printer mechanics are leveraged to achieve high positional accuracy, with positioning errors below 20 μm. The overall cost is significantly reduced compared to conventional measurement systems, using off-the-shelf components. The modular architecture allows for pairing the setup with different measurement instruments. The influence of moving cables is investigated, and amplitude and phase stability better than 0.6 dB and 5° at 60 GHz is maintained across the full scan volume. An exemplary NF measurement of a horn antenna in the V-band is conducted and compared to simulation, showing good agreement. The system is released as an open-source project (AntRig-Measurement-System) that provides mechanical design files, automation software, and instructions for assembly and use. The proposed measurement system combines a compact, portable, cost-effective, yet flexible implementation that is easy to replicate and use, and offers accuracy comparable to that of conventional solutions.Publicationtype: Journal Article2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Simulation framework for the evaluation of the radar channel transfer function in the near field of electrically large targets(Cambridge University Press, 2026-10-05); ; ; ; A simulation framework to evaluate the radar channel transfer function in the near field of electrically large targets is presented in this article. The framework is based on the concepts known from physical optics adapted to the near-field conditions. The impact of the radar antenna characteristics on the scattering, which is non-negligible in the target near field, is incorporated by means of the antenna’s far-field radiation patterns. The inputs of the simulation framework are an STL-file-based model of the target and the gain and phase patterns of the antenna. The required sampling density of the target surface is examined in the context of convergence. The framework accounts for absorption effects due to dielectric or ohmic losses. Because the framework relies on direct evaluations without the need to solve equations, it exhibits a low computational effort, leading to fast computations. The applicability of the simulation framework is validated by measurements with different antennas at 24 and 61 GHz.Publicationtype: Journal Article35 163 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Radarbasierte Erfassung von Herzratenveränderungen bei Schmerz- und DyspnoereizHintergrund: Die berührungslose und belastungsfreie radarbasierte Erfassung der Herzrate (HR) mit EKG-äquivalenter Genauigkeit konnte auf einer Palliativstation gezeigt werden ([1]). Hierbei zeigten sich Hinweise auf HR-Effekte durch Symptome. Im klinischen Setting unterliegt die HR verschiedenen Einflüssen. Standardisierte Modelle bei gesunden Probanden können helfen die radarbasierten Messverfahren bezüglich der Symptomerkennung zu validieren. Fragestellung: Kann radarbasierte HR-Erfassung Effekte von Schmerz- und Dyspnoemodellen unter standardisierten Laborbedingungen bei gesunden Probanden im Vergleich zu Selbstreport (iPOS) und EKG reliabel erfassen? Methodik: 37 gesunde Proband:innen durchliefen eine Ruhephase (RP), gefolgt von Intervention (IV) 1, einer RP, einer zweiten IV und einer abschließenden RP. Schmerz wurde durch den Cold-Pressor-Test (CPT; Hand in Eiswasser) induziert, Dyspnoe durch laminar erhöhten Atemwiderstand mittels ausschließlichen Atmens durch einen Strohhalm. Die Abfolge der Interventionen war cross-over randomisiert. Die subjektive Symptomstärke wurde mittels iPOS erfasst und Gruppen gebildet (0–2 vs. 3–4). Die HR wurde kontinuierlich über ein sechs-Kanal-EKG sowie ein 61GHz-Radarsystem erfasst ([2]). Ergebnisse: EKG- und Radar-Messungen korrelierten stark (Bias: -0,26 bpm, SD: 4,44 bpm, Limits of Agreement: -8,96 bis 8,44 bpm). Im Median wurden Schmerz als 3 und Dyspnoe als 2 (iPOS) empfunden. Die HR zeigte Unterschiede zwischen Baseline und CPT (p<0,001) sowie zwischen niedriger und hoher Symptomstärke (iPOS 0–2 vs. 3–4, p=0,038). Für Dyspnoe waren Baseline vs. Intervention signifikant (p<0,0001), die subjektive Ausprägung nach iPOS zeigte keinen Unterschied (p=0,278). Schlussfolgerung: Es konnte bei gesunden Probanden ein Dyspnoemodell etabliert werden, das sowohl in psychometrischer Selbsteinschätzung als auch in physiologischen Parametern Atemnot darstellt. Schmerz- und Dyspnoereize erzeugen messbare Änderungen der radarbasierten Herzrate. Dies unterstützt die Interpretation von Daten, die in klinischem Setting an Patient:innen erfasst werden. Nächste Schritte umfassen die Untersuchung von Quereffekten und komplexen Interventionen.Publicationtype: Journal Article2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Digital predistortion of power amplifiers for quantum computing(Institution of Engineering and Technology (IET), 2026-09-01); ; ; Power amplifiers (PA) are essential for microwave-controlled trapped-ion and semiconductor spin based quantum computers (QC). They adjust the power level of the control signal and therefore the processing time of the QC. Their nonlinearities and memory effects degrade the signal quality and, thus, the fidelity of qubit gate operations. Driving the PA with a significant input power back-off reduces nonlinear effects but is neither power-efficient nor cost-effective. To overcome this limitation, this letter augments the conventional signal generation system applied in QCs by digital predistortion (DPD) to linearize the radio frequency (RF) channel. Numerical analysis of the qubit behavior based on measured representative control signals indicates that DPD improves its fidelity.Publicationtype: Journal Article15 5 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Electrical and morphological properties of tollens-deposited silver on photopolymer resin relevant to 3D-printed microwave componentsThis work presents the first systematic investigation of the fundamental electrical and morphological properties of Tollens-deposited silver on stereolithography (SLA) 3D-printed polymers. Instead of examining specific waveguides or components, the goal is to establish reliable superordinate process-property relationships for the Tollens-based metallization. Therefore, planar specimens were fabricated to allow quantitative characterization of the metallization. Fundamental process parameters: immersion time, temperature, surface cleaning, and surface pretreatment were systematically varied, and additional influencing factors including ultrasonic assistance, water purity, surface contamination, and repeated metallization were assessed. The characterization included measurements of layer thickness, electrical conductivity, sheet resistance, surface roughness, as well as morphological analysis by scanning electron microscopy and optical microscopy. Depending on the combination of process parameters, the conductivity and layer thickness show significant variations from 27.9 to 6.6 MS/m and 164 to 77 nm, respectively. The best result for a single metallization, 27.9 MS/m and 164 nm, was achieved using deionized water and ultrasonic assistance. The deposited silver thickness is markedly smaller than the surface roughness, and the silver layer is overlain by an island-like layer of irregular silver agglomerates, resulting in an atypical multilayer structure. The findings of this work establish a quantitative basis for the future assessment and optimization of loss and propagation characteristics in microwave components based on 3D-printed, Tollens-metallized photopolymers.Publicationtype: Journal Article23 2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Contactless HR monitoring and HRV assessment by attention-based fusion using a continuous wave radar system(IEEE, 2026-07-14); ; ; Continuous wave (CW) radar is an alternative to gold-standard electrocardiography (ECG) for contactless heart rate (HR) monitoring and heart rate variability (HRV) analysis. This work aims to monitor HR and HRV using a deep learning (DL) model with a 61 GHz CW radar system. We employed attention-based DL fusion model to combine information from radar heart sound (HS) and radar pulse wave (PW) signals. Additionally, we compared attention-based fusion with alternative fusion methods, including data fusion, feature fusion, and decision fusion. To evaluate the performance of the proposed method, a dataset of approximately 20 hours was collected from 20 participants in varying body positions. Using attention-based fusion, we achieved the overall highest F1 score of 97.15% for heartbeat detection, which outperformed solely HS-based or PW-based model, as well as other fusion methods. F1 scores exceeding 96% were obtained for all analyzed body positions. A high correlation of 97.11% and an RMSE of 28.99 ms were achieved for the estimation of the interbeat interval (IBI). In addition, we extracted HRV in time, frequency, and nonlinear domains. Low relative errors were achieved, e.g. 14.04% for TRI, 6.14% for LF, 6.35% for alpha2, and 10.93% for ApEn. The proposed approach achieved high-level performance for HR monitoring and HRV estimation using a CW radar system, showing great potential for various healthcare applications.Publicationtype: Journal Article44 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Determination of the radar channel transfer matrix in the near field of electrically large targets based on physical optics principlesThis contribution deals with the determination of the radar channel transfer matrix in short-range radar applications. In these, the radar antennas are often located in the near field of an electrically large target, in which the scattering properties, in contrast to far-field relationships, depend on distance as well as the antenna. Based on physical optics and the antenna radiation pattern, a bistatic complex-valued transfer function between the feed of a transmit antenna and the output port of a receive antenna is derived. For multiple antennas, it extends to a channel matrix, which allows to predict the radar response of multiple-input multiple-output (MIMO) systems as well as antenna arrays. Measurements of the channel matrix in the case of a disk target conducted with horn and open-ended waveguide antennas at 24 GHz prove the validity of the proposed approach. It accurately predicts near-field effects such as power level fading and nonlinear phase distortion for MIMO radar configurations.Publicationtype: Conference Paper28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , A novel concept for a wake-up receiver for LoRa communication with improved selectivityThis work presents a novel approach for the implementation of a wake-up receiver for LoRa communication. It is designed to exploit the LoRa modulation based on chirp spread spectrum and is inherently less susceptible to false wakeups caused by interfering signals. The theory of the concept is presented indicating key parameters. For validation, a proof-ofconcept implementation is developed with exemplary measurement results.Publicationtype: Conference Paper34 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Open sync board – an open-source tool for hardware synchronization of multimodal physiological sensor setups(University of Western Ontario, Western Libraries, 2026-05-01); ; ; The fusion of multimodal sensor data gains increasing importance in medical and psychological research. In particular, the analysis of multi-modal data contributes to a broader understanding of human well-being. When experimenting with different sensing modalities, precise synchronization of recorded data is a crucial problem that needs to be addressed. We have developed a hardware-based solution capable of synchronizing up to seven arbitrary measurement modalities. These modalities can be mounted to a PCB with various connectors to be either triggered synchronously or receive simultaneous synchronization signals. In the latter case, data can be aligned after the measurement. All PCB outputs are galvanically decoupled to avoid interference and ensure safe usage in human-centered research. In this project, we put particular emphasis on flexibility, high usability, and accuracy. Thus, different synchronization signal options are provided to suit short- as well as long-term measurements. Settings can be configured easily with an accompanying graphical user interface. Additionally, we ensured a high precision of the output signals is ensured with an estimated maximum delay of 125 μs between the output ports. This enables sub-sample synchronization accuracy for sensors with up to 8 kHz sampling rate.Publicationtype: Journal Article12 5