This paper presents a loaded-waveguide nearfield probe based on 3D-printed Alumina for W-band applications. Conventionally, a standard air-filled waveguide is used as a probe to capture images (material mapping) and obtain information (device characterization) of RF devices. However, at millimeter-wave frequencies, the waveguide's metallic housing is usually bulky compared to the device under test, resulting in a distorted measurement field with low spatial resolution. Instead of an air-filled waveguide, we propose here an Alumina-loaded waveguide probe based on the 3D-printing technique. The high permittivity of Alumina down-scales the waveguide size, and its low loss tangent maintains an efficient signal transmission. Due to the smaller aperture size of the Alumina waveguide, it is minimal-invasive and offers a higher spatial resolution than standard waveguide probes. To employ this Alumina waveguide probe in a common measurement system that utilizes standard waveguide interfaces, a transition structure has been designed for the Alumina probe, which is integrated into a CNC-machined WR-10 waveguide adapter. It is shown that compared to a standard air-filled waveguide, our Alumina waveguide probe significantly enhances the spatial resolution of the measured field at the W-band.

We present a numerical study of a nanocoated whispering-gallery-mode (WGM) silica microdisk as a label-free platform for single-exosome detection and refractive-index–based health-state classification. The device is modeled as a fiber-coupled silica microdisk in water, functionalized with a thin nanocoating of either polystyrene (PS) or the metal-halide perovskite CsPbI3. Using full-wave driven-mode simulations in Comsol Multiphysics, we show that nanocoatings reshape the WGM field distribution and improve sensing-relevant figures of merit by enhancing surface-field confinement while preserving high-Qf operation. Beyond the field-pulling mechanism provided by polymer coatings, we demonstrate a distinct sensitivity enhancement enabled by perovskites: spectral alignment of the WGM with an excitonic resonance in CsPbI3 supports a hybrid excitonic–photonic mode that concentrates optical energy at the sensing interface and increases the transduction of minute effective-refractive-index (ERI) variations into measurable resonance shifts. To connect the exosome composition to the optical response, we introduce a physics-based workflow to estimate dispersive ERIs of individual exosomes from their protein and nucleic-acid content using a Barer-type relation and a core–shell geometry, and we map these ERIs to resonance-wavelength shifts for single exosomes at the sensing position. The resulting resonance signatures provide separable responses for healthy-like, borderline, and cancer-like exosomes, indicating that the proposed excitonically engineered WGM microresonator can not only detect single exosomes but also classify their health state, supporting a route toward non-invasive liquid-biopsy diagnostics.

Optical waveguides are key elements for high fidelity, long distance optical communications. Coupled waveguide arrays allow for higher information density, steerting the propagation direction, and for encoding information. However, due to the mixing of relative phases for short pulses containing multiple waveguide-mode frequencies, a process for retrieving an encoded input state once these signals undergo coherent propagation remains elusive. A concept is presented to extract with high fidelity the phase-encrypted input signal from spatio-temporal propagated states. As a realization, an array of coupled waveguides is suggested with the retrieval mechanism being realized by local phase shifts that comply with the identified retrieval concept. Three dimensional full-wave electromagnetic simulations for broadband optical signals in coupled dielectric waveguides confirm the validity of the scheme and the high fidelity of information retrieval pointing to potential applications, for instance in ultrafast coherent coding and decoding of information imprinted on pulse sequences.

Accurate impedance characterisation is a prerequisite for reliable radiometric noise power measurements. This work is framed in an approach of non-contact temperature measurements of weakly conductive objects within enclosed cavities. The presented method adapts a de-embedding technique based on S-parameter analysis. The technique enables precise determination of the antenna and low-noise amplifier (LNA) input impedances. Both parameters are essential for scaling measured noise powers and accounting for intrinsic LNA noise. Printed circuit boards (PCBs) were fabricated as devices under test (DUT) and half devices under test (HUT). Reference capacitors were incorporated at defined planes to establish calibration conditions. The symmetry of the DUT was verified using vector network analyser measurements in the 0.2-1 GHz range. This ensures the validity of the de-embedding central reference impedances. The proposed algorithm was applied to experimental data and validated against analytically generated reference models. The results demonstrate excellent agreement between de-embedded and theoretical S-parameters. DUT and HUT structures provide a robust basis for calibration in a novel self-calibrating radiometer. This approach eliminates the need for repeated in situ impedance measurements, thereby enabling accurate, efficient, and scalable radiometric applications. Eine pr & auml;zise Impedanzcharakterisierung ist Voraussetzung f & uuml;r verl & auml;ssliche radiometrische Temperaturmessungen schwach leitf & auml;higer Objekte in geschlossenen Kavit & auml;ten. In dieser Arbeit wird eine De-Embedding-Methode auf Basis von S-Parametern vorgestellt, die eine exakte Bestimmung der Antennenimpedanz sowie der Eingangsimpedanz des rauscharmen Verst & auml;rkers (LNA) erm & ouml;glicht. Beide Parameter sind entscheidend f & uuml;r die Skalierung der gemessenen Rauschleistungen und die Ber & uuml;cksichtigung des intrinsischen LNA-Rauschens. Zu diesem Zweck wurden Leiterplatten (PCBs) als & bdquo;Device under Test" (DUT) und & bdquo;Half Device under Test" (HUT) gefertigt, in denen Referenzkondensatoren an definierten Ebenen zur Kalibrierung eingesetzt werden. Die Symmetrie des DUT wurde durch Messungen mit einem Vektornetzwerkanalysator im Bereich von 0,2-1 GHz nachgewiesen, wodurch ein valides De-Embedding der zentralen Referenzimpedanzen gew & auml;hrleistet ist. Der vorgeschlagene Algorithmus wurde sowohl auf experimentelle Messdaten angewandt als auch mit analytisch erzeugten Referenzmodellen validiert. Die Ergebnisse zeigen eine hohe & Uuml;bereinstimmung zwischen de-embedded und theoretischen S-Parametern. Damit wird best & auml;tigt, dass die entwickelten DUT- und HUT-Strukturen eine robuste Grundlage f & uuml;r die Kalibrierung in neuartigen selbstkalibrierenden Radiometern darstellen. Wiederholte In-situ-Messungen der Impedanzen sind nicht erforderlich, wodurch eine genaue, effiziente und skalierbare radiometrische Anwendung erm & ouml;glicht wird.

Topological textures in magnetically ordered materials are an important case studies for fundamental research with promising applications in data science. They can also serve as photonic elements to mold electromagnetic fields endowing them with features inherent to the spin order, as demonstrated analytically and numerically in this work. A self-consistent theory is developed for the interaction of spatially structured electromagnetic fields with non-collinear, topologically non-trivial spin textures. A tractable numerical method is designed and implemented for the calculation of the formed magnetic/photonic textures in the entire simulation space. Numerical illustrations are presented for scattering from point-like singularities, i.e. Bloch points, in the magnetization vector fields, evidencing that the geometry and topology of the magnetic order results in photonic fields that embody orbital angular momentum, chirality as well as magnetoelectric densities. Features of the scattered fields can serve as a fingerprint for the underlying magnetic texture and its dynamics. The findings point to the potential of topological magnetic textures as a route to molding photonic fields.

Terahertz (THz) technology provides precise monitoring capabilities in dynamic environments, offering unique insights into insect habitats. Our study focuses on environmental monitoring of European honey bees (Apis mellifera) through a combination of measurements and simulations. Initially, the dielectric material properties of honey bee body parts are characterized across the spectral range of 1-500 GHz to collect heterogeneous empirical data. To extend the study, honey bee mockups made from polyamide 12 (PA12) and epoxy resin are employed and validated as effective substitutes for real bees through comparative scattering analyses. The research further explores radar cross-section (RCS), imaging, and spectral properties using advanced THz technologies, including resonant tunneling diodes (RTDs) operating at 250 GHz and THz time-domain spectroscopy (THz-TDS) for frequencies exceeding 250 GHz. High-resolution imaging, utilizing a 450 GHz bandwidth, captures intricate anatomical features of both real and 3D-printed bees, showcasing the potential of THz technology for detailed environmental monitoring. Finally, simulations at 300 GHz assess the dosimetry and feasibility of non-invasive, continuous monitoring approaches based on the heterogeneous honey bee model.

The holographic technique is one of the simplest methods for designing antennas based on metasurface. This paper presents a spoof surface plasmon polariton (SSPP) leaky-wave antenna (LWA) based on the concept of impedance modulated metasurfaces by the anisotropic holographic technique. Instead of parasitic elements, anisotropic SSPP elements are exploited to achieve radiation with circular polarization. The characteristics of the SSPP elements are obtained by the aperture field estimate method. The hologram surface consists of hollow cross-bars unit cells. The anisotropy of each unit cell is achieved by combining the transformation optic method and the particle swarm optimization algorithm. A major challenge of the SSPP LWA based on modulated impedance surfaces is to find a suitable excitation technique. This study proposes a waveguide strip line launcher for excitation to minimize interference on the radiation pattern beam. The designed launcher provides a good impedance matching from 8 to 20 GHz, with an impedance bandwidth of 142%. The peak gain, radiation efficiency, axial ratio (AR) bandwidth, and side lobe level at the design frequency of 18 GHz are 19.7dBi, 93%, 11%, and − 12.1 dB, respectively. After optimizations and simulations are conducted using MATLAB and CST software, the proposed antenna is fabricated, and its radiation characteristics are measured. The measured results agree well with the simulated ones, indicating the high validity of the method.

This paper presents a calibration method for near-field probes (NFPs) based on the reaction theorem to determine the probe coefficient and isolation. These parameters are essential for optimizing the probe’s performance in plant stem monitoring. By integrating the calibrated NFP into a cylindrical positioning setup, the reconstruction of the internal structure of plant stems can be realized by fitting measured and simulated near-field data. Bamboo stem, due to its simple and rigid geometric properties, can serve as an initial test subject to validate the feasibility of the proposed approach.

A method for additive manufacturing of ceramic substrates with desired dimensions is proposed in which permittivity is tailored by varying the sintering temperature. Samples are used as dielectric substrates for a mm-wave bow-tie antenna. A wide tuning range, from 83 GHz to 93 GHz, in the operating frequency of the antenna can be achieved by simultaneously adjusting the substrate thickness and the permittivity, without changing the antenna structure itself.

This scientific paper is an outcome of the MARIE project (for more information, see https://trrmarie.de) [M03]. The contribution reflects our ongoing and planned research in the electromagnetic analysis and functionalization of complex surface systems and volume scattering structures at mm-wave up to THz frequencies. The research relies significantly upon the development of an ultra-fast, full-wave, electromagnetic (EM) simulator based on the Recursive Aggregated Centered T-Matrix Algorithm (RACTMA). Building on this foundation, we are now focusing on the functionalization of EM responses and signatures to enable the analysis and synthesis of reconfigurable volumetric structures through ultra-fast inverse problem solutions. An inverse solution is given in the framework of plant stem monitoring. This effort involves accelerating RACTMA via an n-layer T-matrix algorithm and leveraging massive parallelization in CPU/GPU implementations. The enhanced RACTMA frame-work will incorporate novel topological material representations, such as multiferroic and ferro-electric properties, to enable new EM responses and unlock unexpected device functionalities. A target application includes outdoor relaying using microfluidic reconfigurable scattering posts as realizations of reconfigurable intelligent volumes (RIV).

This paper presents the outcome of the MARIE project C05 (trrmarie.de). C05 carries out research on millimeter-wave (mm-wave) antenna systems for MARIE, which were evaluated with our spherical far-field measurement system. Usually, on-wafer probes are involved in such measurements. Compared to the sizes of most devices under test (DUTs), the on-wafer probe is huge, therefore disturbing the DUT’s far-field by shadowing, scattering, and parasitic radiation. In contrast, the near-field of the DUT is less influenced by the on-wafer probe. In this paper, we introduce different near-field probing concepts at mm-wave frequencies using passive or active probe heads, to solve not only the abovementioned issues for Over-The-Air (OTA) inspection of on-chip components, but also being well-suited for material mapping (together with project M03). In both cases, the near-field probing is done as close as possible to the DUT to capture most spatial harmonics, which vanish in the far-field. Thus, the probe shall be minimal-invasive, mitigating standing waves between the DUT and the probe head.

Exosomes are promising biomarkers for early-stage cancer diagnostics. We present a lab-on-chip biosensor capable of detecting and characterizing single exosomes using a 30 mu m silica microresonator coated with a tailored polystyrene nanoshell. The shell enhances the microresonator's sensitivity, enabling not only single-exosome detection but also characterization based on protein content relevant to cancer diagnostics. Simulation results show that the polystyrene coating increases the resonance wavelength shift by 52% in the presence of an exosome, allowing the detection of subtle variations in protein composition.

This paper presents a metal-only sinusoidal modulated metasurface (MTS) leaky-wave antenna (LWA) with an operating frequency of 18 GHz. Avoiding dielectric losses at high frequencies and withstanding harsh environmental conditions in space exploration are the advantages of metal-only antennas. In spoof surface plasmon polariton (SSPP) structures, the electromagnetic wave of the dominant TM mode is confined at the boundary of two environments. By utilizing the holographic technique and development of pseudo-periodicity in the SSPP structures and consequently stimulating the Floquet mode harmonics, the dispersion curve of the SSPP mode is located inside the radiation cone, and the leakage and radiation conditions of surface wave are provided. The proposed LWA is composed of cross-shaped unit-cells. The realized gain and efficiency of the LWA are 26.5 dBi and 86%., respectively.

This communication presents a dynamic metasurface antenna for electronic beam-steering over 100 GHz. The antenna consists of 40 liquid crystal (LC)-filled metamaterial unit cells, which interact with the guided wave and scatter the energy from the antenna aperture. The unit cells are individually addressable in coupling strength with external biasing voltages. Therefore, the aperture field can be manipulated to radiate directional beams. Experimental results show that the antenna has a beam-scanning range of 66 degrees in E-plane at 105 GHz. The half-power beamwidth theta(HPBW) and realized gain at 105 GHz are around 5 degrees and 5.7 dB, respectively. The response time for beam-steering is approximately 0.5 s with a 12-mu m-thick LC layer. The total thickness of the antenna is only 0.61 mm.

In this paper, a spoof surface plasmon polariton (SSPP) antenna with endfire radiation is inspired by the holographic technique. In contrast to the previous studies with optimization-based structures or using SSPP odd modes, we propose a simple method to design an endfire SSPP antenna based on the holographic principle that can maintain the stability of the endfire radiation over 23% of the impedance bandwidth. The proposed method includes twice modulating the structure with a 180° phase difference. This method eliminates the null in the endfire radiation pattern created by the conventional sinusoidally-modulated reactance surface (SMRS) technique. The proposed SSPP holographic antenna presents a stable endfire radiation pattern within the frequency range of 8-10 GHz. The realized gain and radiation efficiency at the design frequency of 9 GHz are 13.1 dBi and 95%, respectively. An antenna prototype is fabricated and measured in the anechoic chamber. The full wave simulation results of the CST software agree well with measured ones. This miniaturized endfire SSPP holographic antenna can be a potential candidate for wireless communication applications and integrated circuits.

This article introduces a 240-GHz multiple-input-multiple-output (MIMO) radar chipset, consisting of a 120-GHz voltage-controlled oscillator (VCO) monolithic microwave integrated circuit (MMIC) for generating the local oscillator (LO) signal and a 240-GHz transceiver (TRX) MMIC, doubling the frequency and containing one transmitter (Tx) and one receiver (Rx) channel. The Tx channel has a digital vector modulator (VM), allowing for phase adjustments. The 120-GHz VCO has a tuning range of 27.2 GHz (23.6%). The MIMO frequency-modulated continuous-wave (FMCW) system capabilities are demonstrated using a phase-locked loop (PLL)-based VCO stabilization generating wideband, 30-GHz FMCW chirps, which are radiated using a time-division multiplexing (TDM) technique. The MMICs feature a cascadable approach, enabling the scalability of the array size by placing multiple TRX MMICs close to each other using a daisy chain approach. Furthermore, a circular polarized on-chip antenna allows rotation of the MMICs, and the TRX MMIC can be connected to two adjacent edges of the VCO MMIC, creating a 2D array for detecting targets in 3-D space. In the demonstrator setup using eight MMICs, the eight Tx channels of the MMICs generate an equivalent isotropically radiated power (EIRP) of 0 dBm each, reflected from the target and received by eight Rx channels. Overall, the demonstrator system contains 64 virtual elements integrated on an array size of less than 10x10 mm(2).