The objective of the here introduced method is to determine the linearity errors of each receiver in a vector network analyzer (VNA). By varying the source power and using different devices under test, one can identify these errors. Subsequently, the linearity errors of each receiver are used to estimate linearity errors in attenuation measurements. The application of this method resulted in upper bounds for relative linearity errors of 0.005 dB within an amplitude range of up to 50 dB at a frequency of 50 GHz.

We present a software extension for determining material parameters from on-wafer line measurements. This work covers deembedding algorithms for four different models of coplanar waveguides. Their inverse implementation enables material characterization including uncertainty propagation. An example of line measurements from 1-65 GHz on an alumina calibration substrate is provided to demonstrate the application and its ease of use. This extension facilitates material characterization and systematic studies of uncertainty contributions in the realms of on-wafer measurements. It is freely available, allowing industry and research institutions to benefit from an accessible and efficient tool for on-wafer material parameter extraction.

Numerous experimental parameters affect the accuracy of impedance measurements in scanning microwave micro-copy (SMM). Investigating their effects on the measured values is particularly challenging. Here, we present the development of a fully-numerical FEM-based environment as a digital-twin to the actual measurements in SMM. We demonstrate the application of a self-calibration procedure for the simulated measurements with a maximal deviation of ± 6 % relative to reference capacitances determined via electrostatic calculations. Furthermore, we show the possibility to simulate the effects of the tip apex geometry on the simulated SMM measurements.

METAS VNA Tools is a metrology-grade software suite developed to facilitate measurements using vector network analyzers. Its uncertainty analysis is founded on a comprehensive modeling of the entire measurement process and is implemented through multivariate uncertainty propagation via the METAS UncLib library, in accordance with GUM and EURAMET guidelines. Engineered to ensure traceability and compliance with ISO/IEC 17025, VNA Tools has been widely adopted by national metrology institutes, as well as calibration and industrial laboratories, owing to its robustness, transparency, and scientific rigor. As it is freely available, the software serves not only as a tool for the dissemination of calibration data but also enables advanced post-processing. Consequently, it provides added value that extends beyond the mere generation of calibration certificates, reinforcing both the seamlessness and integrity of the traceability chain.

This project is dedicated to the precise measurement of signals at low RF frequencies using advanced electrooptic whispering gallery resonators (WGRs) as field sensors. The primary goal is to enhance the accuracy and reliability of RF measurements. Electrooptic whispering gallery resonators are selected for their exceptional sensitivity and ability to confine light within a small volume, leading to strong interactions between the optical and RF fields. These resonators operate on the principle of total internal reflection, where light circulates within a dielectric material, creating a resonant condition. When exposed to RF fields, the induced change in the refractive index of the electrooptic material alters the resonance condition. This change can be precisely measured, allowing for accurate determination of the RF field strength. The project also investigates an alternative traceability route through calorimetric measurement. Calorimetric methods involve measuring the heat generated by the RF signals dissipated in a load. This approach provides a direct and absolute measurement of RF power, serving as a valuable reference for calibrating other measurement techniques. By comparing the results from the electrooptic WGRs and calorimetric methods, the project aims to establish a robust and traceable measurement system. Additionally, the development of a transfer standard based on a directional coupler is a key component of this project. The coupler is designed to have minimal insertion loss and high isolation. This transfer standard will facilitate the calibration and comparison of different RF measurement systems, ensuring consistency and accuracy across various measurement setups. The integration of electrooptic WGRs, calorimetric measurement, and directional couplers represents a comprehensive approach to RF measurement. The project addresses several technical challenges, including the optimized use of electrooptic materials, the design of the whispering gallery resonators, and the calibration of the measurement systems. Advanced simulation and experimental techniques are employed to refine the designs and validate the measurement methods. Preliminary results indicate that electrooptic WGRs offer high sensitivity, making them suitable for monitoring of RF signals. The calorimetric method provides a reliable reference, ensuring the traceability of the measurements. The directional coupler demonstrates excellent performance, enabling accurate transfer of calibration standards. In conclusion, this project presents a novel and integrated approach to RF measurement at low frequencies. The combination of electrooptic whispering gallery resonators, calorimetric measurement, and directional couplers offers a promising solution for achieving high precision and traceability in RF measurements. The outcomes of this project have the potential to significantly impact various fields, providing a reliable and accurate method for RF measurement that can be widely adopted in industry and research.

This article presents a new multiimpedance-state line (MISL) in situ scattering parameter (S-parameter) calibration technique using on-chip superconducting transmission lines at 4 K that enables cryogenic calibration in a fixed signal path without the need for cryogenic switches or a cryogenic probe station. The method uses coplanar waveguide (CPW) models based on various impedance states of niobium (Nb), which has zero dc resistance below 9 K and a monotonically increasing resistance from 10 K to room temperature. The different impedance states are accessed by heating the 4 K stage of a cryostat and injecting up to 245 mA of current into the line. Using these states, we solve for the unknowns in an eight-term error model through a least-squares analysis. We first validate the MISL calibration technique by comparing it with short-open-load-reciprocal (SOLR) calibrated measurements in a cryogenic probe station, finding transmission agreement within 0.2 dB and uncertainty overlap for nearly all frequencies up to 26.5 GHz. We then apply the method to calibrate Nb CPWs with and without embedded Josephson junctions (JJs), using a fixed wire bonded connection, and without the use of cryogenic switches or movable probes. Strong agreement with the CPW models is demonstrated, with uncertainty overlap and differences below 0.1 dB up to 4.6 GHz without JJs and up to 2.4 GHz with JJs; resonances cause interruptions beyond these frequencies.

This paper presents METAS VNA Tools Version 2.9.0, a metrology software suite designed to support the digital traceability chain in vector network analyzer measurements. Built on the METAS UncLib Version 2.9.0 uncertainty engine, the software enables rigorous modeling of the entire measurement process and comprehensive uncertainty evaluation. By encapsulating values, dependencies, and sensitivities in structured uncertainty objects, the software ensures that traceability and correlation information are preserved and propagated throughout complex calibration chains. This approach allows for seamless, modular uncertainty evaluation and supports the generation of digitally signed calibration certificates with embedded calibration data. The methodology enhances transparency, reproducibility, and interoperability, aligning with the goals of digital transformation in metrology. VNA Tools thus provides a robust foundation for implementing traceable, data-driven workflows across all levels of the metrological infrastructure.

In this work, we develop a numerical solver, efficiently and robustly treating highly nonlinear semiconductor device problems. Beyond the capabilities of commercial tools, the solver can compute the time-domain capacitance and the spectrum of the device current. The solver is based on the finite element method (FEM) and employs the successive under-relaxation scheme. Its capability has been assessed and validated in a study of an axisymmetric metal-oxide-semiconductor (MOS) structure, presenting an archetypal scanning microwave microscopy (SMM) calibration sample, with both n- and p-doped semiconductors, including different excitation sources. Excellent agreement was obtained, when testing the tool against features of a commercial tool. By computing the capacitance for the applied low-frequency (LF) bias, combined with a high-frequency (HF) probe signal, the spectrum of the current flowing in the structure was evaluated, revealing mix-product components. This allowed us to verify the solver against measurements, resulting in a very good agreement.

We present a hybrid measurement platform that integrates super-resolution fluorescence microscopy with an open-ended nano-coaxial scanning microwave microscope (SMM). We demonstrate this system on diamond particles, which simultaneously emit bright fluorescence from nitrogen-vacancy (NV) centers. The nano-coaxial apex structure consists of a fused silica dielectric (outer diameter: 5 mu m), a Pt inner conductor (similar to 1.2 mu m diameter), coated with a Cr/Au bilayer (10 nm/200 nm). This proof-of-concept study demonstrates simultaneous microwave and optical imaging of a new class of quantum materials, and may have applications ultimately in quantum state manipulation of qubits using nanoscale confinement of microwave pulses.

Scanning microwave microscopy (SMM) is a combination of an atomic force microscope with a vector network analyzer (VNA) to measure locally resolved impedances. The technique finds application in the realms of semiconductor industries, material sciences, or biology. To determine quantitative material properties from the measured impedances, the system must be calibrated. Transferring the calibration from the calibration substrate onto the material under test is strongly limited when using unshielded probes, as the electromagnetic coupling to the surroundings can reach several centimeters. This work reports the fabrication of coaxially shielded probes for a scanning microwave microscope and their integration into such an instrument. We discuss a calibration method with dielectric references, using a simulation-assisted 1-port VNA calibration algorithm. Uncertainty considerations of the measurement process are included and propagation throughout the algorithm is performed. The calibration is verified with an additional dielectric reference. As an application example, the results for a static-random-access memory sample are presented. We identified system-related drift and trace noise as the dominant contributors to the uncertainties of the calibrated results. The here presented shielded tips can broaden the application scope of SMM, as they are door-openers for measurements in liquids.

On-wafer calibrations are critical for measurements of embedded devices at the correct reference planes. A major challenge in on-wafer calibrations is the development of accurate calibrations that cover a frequency range from MHz to THz. Another challenge facing on-wafer measurements is the lack of calibrations that are directly traceable to the SI. The multiline Thru-Reflect-Line (TRL) calibration is a promising approach for high-frequency traceable on-wafer measurements. However, space considerations limit this approach to higher frequencies. Here, we compare the performance of several calibrations with different footprint requirements. Specifically, we compare three calibration kits: TRL fabricated with Au conductors, TRL fabricated with Pt conductors, and a series resistor (SR) calibration kit with Au conductors. We find that both the Au and Pt TRL calibration kits perform well above approximately 100 MHz. Then, we compare the performance of the different TRL calibration kits with reduced numbers of lines to assess the impact of device footprint on calibration quality. We find that changing the conductor material to more resistive Pt does not substantially improve the quality of the TRL calibration at low frequencies, while increasing the length of the longest line does.

In this paper, a definition of the gain and added noise of impedance matching networks for scanning microwave microscopy is given. This definition can be used to compare different impedance matching techniques independently of the instrument used to measure the S-parameter. As a demonstration, impedance matching devices consisting of a Beatty line, a tuner, and interferometric setups with and without amplifiers have been investigated. Measurement frequencies up to 28 GHz are used, and the maximal resulting gain found was 9504.7 per Siemens.

This paper describes how to calculate S-parameters in a reference plane on a PCB with unknown access lines. The technique is based on two taps on a section of the transmission line on a PCB. The application of this technique is cost-effective on-wafer measurements and cryogenic on-wafer measurements. In this proof of concept, a coaxial to coplanar waveguide transition is measured and compared to calculated results. This yielded differences of less than 0.09 dB up to 20 GHz in transmission.

In this paper research activities developed within the FutureCom project are presented. The project, funded by the European Metrology Programme for Innovation and Research (EMPIR), aims at evaluating and characterizing: (i) active devices, (ii) signal- and power integrity of field programmable gate array (FPGA) circuits, (iii) operational performance of electronic circuits in real-world and harsh environments (e.g. below and above ambient temperatures and at different levels of humidity), (iv) passive inter-modulation (PIM) in communication systems considering different values of temperature and humidity corresponding to the typical operating conditions that we can experience in real-world scenarios. An overview of the FutureCom project is provided here, then the research activities are described.

Magnesium-ion batteries (MIBs) represent a promising chemistry to potentially substitute lithium-ion technologies in the e-mobility and stationary energy storage applications. This is due to the favourable properties of metallic Mg, such as: abundancy, non-toxic nature, high recycling rate 1 , low redox potential (-2.37 vs SHE), safety (smooth Mg 2+ electrodeposition), as well as divalent character of Mg 2+ cations which leads to higher theoretical volumetric capacity (3833 mAh/cm 3 ) than Li (2046 mAh/cm 3 ) and commercial graphite (760 mAh/cm 3 ). 2 However, the major obstacle in the further development of MIBs is the incompatibility of Mg metal anode with conventional electrolyte solutions, which are formed by mixing simple Mg-based salts (e.g Mg(TFSI) 2 , Mg(ClO 4 ) 2 , etc.) and polar aprotic solvents (e.g. acetonitrile, carbonates, etc.). These solutions decompose at the surface of metallic Mg forming an electronic and ionic insulating layer, leading to the passivation of the Mg anode and poor performance of the overall cell. Conversely, organoborate (Mg-tetrakis(hexafluorosisopropyloxy)borate in monoglyme, MgBOR) 3 or organoaluminate (1:2 AlCl 3 :PhMgCl in THF, APC) 4 ethereal solutions are known to prevent the passivation of the Mg metal anode, allowing the reversible electrochemical Mg 2+ electrodeposition onto its surface. Despite a great effort has been done in the development of MIB, 5 very little is known about the formation, evolution and degradation of the solid electrolyte interphase (SEI) formed at the interface between metallic Mg and electrolyte. This work, therefore, aims to investigate the interactions between Mg metal and passivating (Mg(TFSI) 2 in monoglyme:diglyme) and non-passivating (MgBOR and APC) electrolytes combining ex-situ and in-situ spectroscopic and microscopic techniques with electrochemical testing. The properties of the SEIs will be evaluated at different states of charge ( ex-situ ) and during cell cycling ( in-situ ). Raman, Fourier transformed infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies are used to identify the composition of the electrolyte interphases, as well as monitor their changes upon cell discharge-charge cycles. Scanning electron microscopy (SEM) is performed to analyse the interphase morphologies, whereas scanning microwave microscopy (SMM) 6,7 locally probes the impedance of the SEI layer. Atomic force microscopy (AFM) is also employed to evaluate the roughness of the Mg metal electrodes. Cyclic voltammetry (CV) and galvanostatic cycling with potential limitation (GCPL) are carried out in order to determine the electrochemical performance of bare Mg metal or covered with SEI layers. Furthermore, electrochemical impedance spectroscopy (EIS) is employed to probe the Mg 2+ diffusion coefficients through the SEI layers at different state of charge (e.g. open circuit voltage, etc.) and determine charge transfer evolution with cycling time of the Mg metal anode. As the first step, a successful polishing method was developed to remove the native oxide layer form the surface of Mg discs allowing to expose a bare Mg metal to the electrolyte solutions and to evaluate their interactions. The polishing method also enabled to perform SMM imaging of the Mg metal since a roughness between 1-2.5 µm was achieved. The Mg discs were then immersed in the electrolyte solutions and an initial deposition of interfacial species (few nanometre thickness) was observed by SEM when Mg(TFSI) 2 in monoglyme:diglyme was used, whereas a smooth surface was detected with MgBOR and APC electrolytes. This resulted in different electrochemical behaviours. In fact, symmetric cells (Mg||Mg) with MgBOR electrolyte showed a significantly higher cycling stability (> 250 h) than those with Mg(TFSI) 2 in monoglyme:diglyme solution. In addition, when the latter electrolyte was used, fluorinated by-products were identified by XPS. In order to study the SEI formation and growth further, in-situ spectroscopic techniques (e.g. Raman and SMM) were employed to establish a correlation between the chemical composition of the electrolyte, the voltage range of the electrochemical tests and cycling time. In particular, the SMM method was applied to MIB technologies for the first time in this work. References I. R. P. United Nations Environment Programme, (available at https://wedocs.unep.org/20.500.11822/8702); J. Niu, Z. Zhang, D. Aurbach, Adv. Energy Mater. , 2020 , 10 , 2000697; Z. Zhao-Karger, M. E. Gil Bardaji, O. Fuhr, M. Fichtner, J. Mater. Chem. A , 2017 , 5 , 10815–10820; D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, E. Levi, Nature , 2000 , 407 , 724; R. Dominko, J. Bitenc, R. Berthelot, M. Gauthier, G. Pagot, V. Di Noto, J. Power Sources , 2020 , 478 , 229027; A. Buchter, J. Hoffmann, A. Delvallée, E. Brinciotti, D. Hapiuk, C. Licitra, K. Louarn, A. Arnoult, G. Almuneau, F. Piquemal, M. Zeier, F. Kienberger, Rev. Sci. Instrum. , 2018 , 89 , 23704; J. Hoffmann, M. Wollensack, M. Zeier, J. Niegemann, H. Huber, F. Kienberger, in 2012 12th IEEE International Conference on Nanotechnology (IEEE-NANO) , pp. 1–4.

Electrochemical impedance spectroscopy (EIS) is a widely used method for battery tests in manufacturing and automotive field applications. As such, accurate measurement of the impedance over a broad frequency spectrum is of high relevance, also requiring specific calibration methods and evaluation of error bounds. Here, we report for the first time a comprehensive uncertainty analysis of calibrated EIS for batteries. We aim to identify two uncertainty sources, the fixture repeatability and measurement noise, and evaluate their effect on the measured impedances. To this end, an error model assigned to each of them and the real and imaginary parts of the model parameters are characterized in the frequency range of 100 mHz–5 kHz by performing specific impedance measurements on a shunt resistor and a short standard. We demonstrate how different uncertainties are combined with the measured impedances, incorporating also the impedance calibration procedure. The errors are propagated through the calibration and correction functions by applying the linear error propagation method provided by the UncLib package from METAS. The error bounds are derived from uncertainty propagation in the shunt standard and the prismatic battery cell EIS and verified by conducting a series of measurements. Thereby, the uncertainty is shown as ellipsoids in every frequency point of the Nyquist plot. For instance, at 1 Hz, the 34-Ah prismatic cell shows a calibrated real-part impedance and two standard deviation error bounds of 1.07 $\text{m}\Omega $ ± $26~ \mu \Omega $ .

Measuring the material parameters with a vector network analyzer (VNA) usually requires time-domain gating and complicated free-space calibrations. At terahertz frequencies, classic calibrations become more problematic and uncertainty calculation for time gating is not clearly defined. The here investigated method skips these steps and is based on normalization to a “Thru” connection and analyzing error terms and multiple-reflection phenomena (ripples). It is shown that at specific frequencies, the ripples are very small. Based on this, the “standard load” method is introduced, which simplifies the error correction for transmission and reflection measurements for the whole frequency range. Results are presented in 75-110- and 500-750-GHz bands with a quasi-TEM free-space setup. Various material slabs (thin, thick, lossy, and low-loss) have been tested to show the reliability and general usefulness of the method. This method that is initially based on a “Thru” connection only provides a simple and low-cost alternative to the conventional standards (Line, Match, Short, and so on) and calibration techniques.