Broadband Measurements Research Articles

Determination of microwave material properties at cryogenic temperatures

Quantum information processing systems rely on cryogenic microwave electronics, and printed circuit board (PCB) laminates play an essential role, including integrating quantum chips and connecting microwave circuit elements. In this Letter, we report a method for accurately determining the microwave conductivity and complex permittivity of PCB laminates over a wide temperature range, from 4 to 300 K. The use of higher-order resonant modes of a balanced-type circular disk resonator (BCDR) enables broadband measurements ranging from below 5 GHz to above 20 GHz. Furthermore, a temperature-independent determination scheme is achieved by employing a pair of BCDRs and a cryogenic calibration technique. This method is demonstrated by measuring two commercially available PCB laminates. The results indicate that while dielectric loss is monotonically reduced at cryogenic temperatures, the reduction in conductor loss is strongly suppressed by the surface roughness of the copper foil. Additionally, the obtained conductivity as a function of frequency and temperature fits well with the Gradient Model, allowing for the evaluation of the root mean square roughness parameter.

Study on the Broadband Measurement Method of Electric Field Sensing Voltage Based on the Add-Window Technique

Study on the Broadband Measurement Method of Electric Field Sensing Voltage Based on the Add-Window Technique

Overview of Key Techniques for In Situ Tests of Electromagnetic Radiation Emission Characteristics.

With the growing number of electronic devices loaded and increasing influence from electromagnetic interference, large-scale systems or platforms are confronted with increasingly severe electromagnetic compatibility challenges. Due to the vast size of these systems and the multitude of electronic devices they contain, standard laboratory environments are often inadequate for meeting test requirements. This paper reviews the state-of-art in the area of field measurement techniques related to the checking of electromagnetic compatibility, and the key technologies of electromagnetic interference filtering and wide-bandwidth, large-dynamic, and rapidly transient signal extraction in the measurement field are analyzed. The research status of electromagnetic interference suppression, transient and broadband measurement, and environmental interference suppression combined with time-domain fast measurement and other technologies are summarized and analyzed. Based on a comparative analysis of the aforementioned technologies, the future development trends of field measurement technology are also discussed.

Design of a new wide frequency measurement method for power system

Abstract Aiming at the wide application and complex characteristics of the new power system, this paper proposes a design of broadband measurement method and realizes the application of broadband signal analysis and broadband measurement by improving the wavelet packet algorithm. As a multi-resolution analysis method widely used in the field of signal processing, the wavelet transform is unique in that it can perform local analysis in both time and frequency domains at the same time and has significant advantages in analyzing time-varying non-stationary signals. This paper will start from the algorithm requirements of electronic measurement devices based on the basic theory of wavelet transform, build a wide frequency measurement method, and comprehensively simulate and analyze the test signal. By combining the SVMD (Successive Variational Mode Decomposition) adaptive extraction algorithm with frequency band decomposition, the main sub-harmonic components in the frequency band are accurately extracted and measured, which verifies the feasibility and superiority of the algorithm.

Wideband microwave frequency response measurement based on optical phase-locked loop.

Frequency response measurement, or the forward transmission coefficient (S21) measurement for a two-port network, is the key function of a vector network analyzer (VNA). In this paper, a broadband and high dynamic range (DR) microwave S21 parameter measurement scheme based on an optical phase-locked loop (OPLL) is proposed. By heterodyning two phase-locked hybrid integrated ultra-narrow linewidth lasers, a microwave signal with low phase noise and spurious level is generated as the incident signal and reference signal, and the signal frequency can be easily manipulated over a wide range by tuning the master laser wavelength. In the receiver, the radio frequency (RF) signals are down-converted to intermediate frequency (IF) signals with the phase-locked lasers. By sampling and processing the IF signals the S21 parameter of the DUT can be acquired. A proof-of-concept experiment is performed, and with available photodetectors, phase modulators and phase-locked loops, a measurable range of 2 to 18 GHz is achieved. The demonstrated minimum frequency resolution of the OPLL-based RF signal synthesizer is 10 Hz. The system DR exceeds 68 dB at an equivalent resolution bandwidth of 1 kHz. The S21 parameters of a power divider and a bandpass filter are measured, and the results are well consistent with those of a commercial VNA. The DR and measurable range limit factors and possible extension methods are discussed. The proposed approach offers a high potential way to develop a wideband, high DR, and fully integrated VNA.

The spectral mismatch correction factor estimation using broadband photometer measurements and catalog parameters for tested white LED sources

Using a modeled look-up chart developed in this work, we show that accurate photometric measurements of characteristics like illuminance or luminous intensity of test LED sources can be measured in one step. This is a simple broadband measurement that may substitute for complicated and costly spectral measurements currently in place. To develop the look-up chart, the typical minimum and maximum of the Spectral Mismatch Correction Factor (SMCF) for a given photometers was estimated in relation to catalog parameters of the LEDs such as correlated color temperature (CCT) and melanopic daylight efficacy ratio (mDER). This research was based on the unique and large dataset of real photometers spectral response srel(λ) collected and measured at accredited laboratories located at America, Asia and Europe and modeled LED's spectral power distribution (SPD) data. Independent look-up tables were developed for color-mixed LEDs (cm-LEDs) and white phosphor-converted LEDs (pc-LEDs), two common LED types.

Research on Broadband Measurement Method of Power System based on Wavelet Transform

This study delves into the exploration of broadband measurement techniques for power systems, utilizing wavelet transform as a foundational tool for signal analysis. The research rigorously evaluates the efficacy of several machine learning algorithms, namely Support Vector Machines (SVM), Artificial Neural Networks (ANN), K-Nearest Neighbors (KNN), and Random Forest, in interpreting and analyzing broadband signals within power systems. Through a detailed analytical process, the performance of each algorithm is meticulously assessed based on several critical metrics: accuracy, precision, recall, and F1-score. The research investigates broadband measurement methods for power systems using wavelet transform and evaluates the performance of Support Vector Machines (SVM), Artificial Neural Networks (ANN), K-Nearest Neighbors (KNN), and Random Forest. Results show SVM achieving an accuracy of 85%, precision of 86%, recall of 82%, and F1-score of 84%. ANN yields 82% accuracy, 84% precision, 78% recall, and 81% F1 score. KNN demonstrates 87% accuracy, 88% precision, 84% recall, and 86% F1 score. DT achieves 79% accuracy, 80% precision, 75% recall, and 77% F1 score. Overall, the study provides insights into machine learning algorithms’ effectiveness in broadband power system measurement.

Device for detection of activity-dependent changes in neural spheroids at MHz and GHz frequencies

Intracellular processes triggered by neural activity include changes in ionic concentrations, protein release, and synaptic vesicle cycling. These processes play significant roles in neurological disorders. The beneficial effects of brain stimulation may also be mediated through intracellular changes. There is a lack of label-free techniques for monitoring activity-dependent intracellular changes. Electromagnetic (EM) waves at frequencies larger than 1 × 106 Hz (1 MHz) were previously used to probe intracellular contents of cells, as cell membrane becomes “invisible” at this frequency range. EM waves interact with membranes of intracellular organelles, proteins, and water in the MHz – GHz range. In this work, we developed a device for probing the interaction between active neurons’ intracellular contents and EM waves. The device used an array of grounded coplanar waveguides (GCPWs) to deliver EM waves to a three-dimensional (3D) spheroid of rat cortical neurons. Neural activity was evoked using optogenetics, with synchronous detection of propagation of EM waves. Broadband measurements were conducted in the MHz-GHz range to track changes in transmission coefficients. Neuronal activity was found to reversibly alter EM wave transmission. Pharmacological suppression of neuronal activity abolished changes in transmission. Time constants of changes in transmission were in the seconds – tens of seconds range, suggesting the presence of relatively slow, activity-dependent intracellular processes. This study provides the first evidence that EM transmission through neuronal tissue is activity-dependent in MHz – GHz range. Device developed in this work may find future applications in studies of the mechanisms of neurological disorders and the development of new therapies.

One-Port Coaxial Line Sample Holder Characterisation Method of Dielectric Spectra.

A technique for solving the one-port closed coaxial transmission line sample holder scattering equation for complex permittivity inversion for lossy materials is presented. A non-linear least-squares procedure is used for the determination of parameters for the specification of the spectral functional form of the complex permittivity. The method allows for accurate retrieval of many low- and high-permittivity dielectric materials in the frequency range of 1 GHz to 3 GHz inserted into the coaxial cell. Using this method, the complex permittivity of a number of liquids and a Maltese soil known as Bajjad soil have been extracted by measurements using a short terminated coaxial transmission line sample holder. The proposed novel inversion method is mainly based on the reflection coefficient of the test material. The measured results of the complex permittivity of liquid dielectrics such as ethanol, methanol, and TX100 are validated and compared with previously published data obtained from measurements made by the National Physical Laboratory (NPL) using a two-port measurement setup made with the same commercial coaxial transmission line sample holder used in the one-port setup. Since the technique allows broadband measurements, it has been used to characterise the soil dielectric spectrum in the frequency range of 1-3 GHz, which is also compared with results from a two-port setup of the same coaxial line. The experimental results are a validation of the proposed approach for different types of materials.

Single-modulator, dual comb serrodyne spectroscopy.

Dual optical frequency comb spectroscopy allows for high speed, broadband measurements without any moving parts. Here, we combine differential chirp downconversion to probe large spectral bandwidths and serrodyne modulation to separate the positive and negative sidebands in a single modulator. As an initial demonstration, we apply this approach to measure a sharp cavity resonance to illustrate the system performance. We then measure methane transitions in the near-infrared and compare the resulting spectra to models based upon the current spectroscopic databases. The serrodyne method has lower hardware requirements compared to many existing approaches, and its simplicity enables a high degree of mutual coherence between the two combs. Further, this method is readily amenable to chip-scale photonic integration.

Evaluation and SAR Analysis of Low Frequency and Broadband Electric Field Exposure Measurement Values in the Home Environment

In this study, the effective value of low-frequency (50 Hz) and high-frequency (700–2500 MHz) broadband electric field exposures was measured for 24 h in four different selected environments in a house. All the statistical values of 1000 data points recorded with two measuring devices for 24 h in each environment are calculated, the most appropriate curves are fitted to the data, and the curves are plotted by expressing their changes with respect to time. All statistical and parametric values of the density and cumulative probability functions of the curves are calculated and plotted. In broadband measurements, the broadband is divided into fifteen sub-bands, but the data are available in only six of these sub-bands. The six-layer human head model is created by using the middle frequencies of the six sub-bands used, and taking the permittivity (εr) and conductivity (σ) of each layer into consideration. The specific absorption rate (SAR) value in the brain is calculated by using the total transmission coefficient of six layers. The SAR value surrounding the head is obtained. These SAR values are interpreted by considering the Federal Communications Commission (FCC) and the Community European (CE) occupational and general public SAR limits.

Photonic-assisted wideband microwave frequency measurement based on optical heterodyne detection

A photonic-assisted microwave frequency measurement (MFM) method based on optical heterodyne detection is proposed and experimentally demonstrated. In the proposed MFM system, a linearly chirped optical waveform (LCOW) from a three-electrode distributed Bragg reflector laser diode (DBR-LD) and a multi-wavelength signal from a Mach-Zehnder modulator (MZM), where the signal under test (SUT) is modulated on an optical carrier from a distributed feedback laser diode (DFB-LD), are heterodyne detected by the photodetector (PD). A bandpass filter then filters the detected signal, and the envelope is detected by an oscilloscope. Then, frequency-to-time mapping is realized, and the signal frequency is measured. Thanks to the fast tuning rate and large tuning range of the DBR-LD, the proposed MFM system has a high measurement speed and a broad instantaneous measurement bandwidth. In the experimental demonstration, a measurement error below 39.1 MHz is achieved at an instantaneous bandwidth of 20 GHz and a measurement speed of 1.12 GHz/µs. The MFM of a frequency-hopping signal is also experimentally demonstrated. The successful demonstration of the MFM system with a simple structure provides a new optical solution for realizing broadband and fast microwave frequency measurements.

Effect of the boson peak and the ionic resonance in the dielectric properties of silicate materials at mm-wave and THz frequencies

In this paper, a broadband measurement of the dielectric properties of silicates has been done to cover the seldom characterized mm-wave spectrum and the low THz spectrum. The dielectric properties, i.e. loss and permittivity, show a frequency independent response up to approximately 40 GHz and the loss monotonically increases to the THz frequency range. Two resonance peaks appear at THz frequencies: the first is the boson peak, and the second one corresponds to the ionic resonance of the network former, which in this case is silicon. Even though the materials belong to different groups in the silicate family (crystalline and non-crystalline, with different levels of purity), they seem to have the same overall tendency in the dielectric properties. Argand plots are used for the first time at THz frequencies to provide physical insight into the boson peak and ionic resonance. The complex plane analysis reveals details on the polarization mechanisms underlying silicate network vibrations through direct visualization of their characteristic signatures, and simplifies the process of modeling the dielectric response, leading to a better fit.

A channelized broadband and high-resolution microwave instantaneous multi-frequency measurement system based on Fabry-Perot Filter and Stimulated Brillouin Scattering

A broadband high-resolution microwave instantaneous multi-frequency measurement (IMFM) system based on a Fabry-Perot filter (FPF) and Stimulated Brillouin Scattering (SBS) is proposed. In the system, the 14-line flat optical frequency comb (OFC) in the first branch is input to dual-parallel Mach-Zehnder modulator (DPMZM) for carrier suppressed single sideband modulation (CS-SSB), so that the microwave signal to be measured is loaded onto the sideband of the 14-line OFC. The FPF is employed for periodic filtering to roughly determine the frequency band of the captured microwave signal. Subsequently, the demultiplexer (De-mux) is utilized to channelize the captured frequency band, which serves as a pump light input to the high nonlinear fiber (HNLF). By setting the center frequency spacing between the OFCs in the second and third branches with the channelized pump light in the first branch is equal to the Brillouin frequency shift, the frequencies of the microwave signal under measurement are determined based on the fine frequency selection characteristic of the SBS effect. This achieves an enhancement in measurement resolution while ensuring measurement bandwidth. Simulation experiments indicate that by adjusting the frequency shifter and center frequency of the FPF, the proposed IFM system can realize measurement ranges of 0.6–13.5 GHz, 13.6–26.5 GHz, and 26.6–39.5 GHz, the measurement resolution is 0.1 GHz, and the measurement error is ±0.05 GHz.

Development of long-range conductivity mechanisms in glass-like carbon

The conductivity mechanisms in glass-like carbon synthesised from SU-8 3005 photoresist are explored as a function of pyrolysis temperature (between 700–750 °C) utilising microwave dielectric spectroscopy techniques. Broadband measurements using an open-ended coaxial probe (BCP) are used to investigate the complex permittivity and conductivity as a function of frequency and show the development of long range conduction and sp2 carbon chain formation. Fixed frequency resonance measurements using microwave cavity perturbation (MCP) methods are shown as a way of measuring this transition and change in Q-factor without requiring contacts and therefore acting as a effective method for non-destructive and non-invasive measurements. Using these methods we show a clear change in the AC conductivity of glass-like carbon at a pyrolysis temperature of ∼730 °C and demonstrate how microwave cavity perturbation (MCP) can be used as a non-contact method of dielectric spectroscopy for determining the transition of conductivity mechanisms in glass-like carbon from short to long range and therefore as a method for non-destructive material quality control. We demonstrate that both BCP and MCP dielectric spectroscopy methods are effective at clearly detecting changes in the structure and conductivity mechanisms of glass-like carbon over a small pyrolysis temperature range.

Parasitic mixing in photomixers as continuous wave terahertz sources

We present observations of parasitic frequency components in the emission spectrum of typical photomixer sources for continuous wave (CW) terahertz generation. Broadband tunable photomixer systems are often used in combination with direct power detectors, e.g., for source and/or detector characterization. Here, spectral components besides the intended terahertz emission at the difference frequency of the two excitation lasers can significantly distort the measurement results. In this work, the appearance of parasitic mixing signals is observed in broadband measurements with a broadband antenna-coupled field-effect transistor as terahertz detector (TeraFET). The measurements reveal weaker spectral absorption features than expected and also a signal plateau towards higher frequencies, both strongly indicating a background in the detection signals. The photomixer emission is investigated in detail with a terahertz Fourier-transform infrared spectrometer (FTIR). We relate the observed parasitic frequency components with good quantitative agreement with the mode spectra of the semiconductor lasers. We also present one possible approach to overcome some of the issues, and we emphasize the importance of our findings to avoid distorted measurement results. To our knowledge, the essential aspect of parasitic mixing has so far been largely ignored in the literature where terahertz CW photomixer emitters are widely used for spectrally resolved measurements.

5G NR launching in Greece: Preliminary in situ and monitoring network measurements of electromagnetic fields exposure levels at rooftops.

In Greece, 5G New Radio (NR) has started launching in the end of 2020, at the 3400-3800 MHz (FR1) frequency band. Focusing on 117 Base Stations (BSs) which were already equipped with 5G NR antennas, in situ broadband and frequency selective measurements have been conducted at minimum three points of interest, at adjacent rooftops (when accessible). The points have been selected according to the sweeping method and the electric field strength (E) value has been stored on the selected worst-case scenario point. Spectrum analysis was conducted in the FR1, for the allocated spectrum that corresponds to each mobile communication provider, in order to get preliminary results concerning the contribution of the 5G NR emissions in the general public exposure levels. The vast majority of the in situ measurements has been conducted in urban environments from the beginning of 2021 until the mid of 2022, since in Greece 5G NR services launching started from the big cities. Additionally, a 5G NR BS, installed in a suburban environment (in the city of Kalamata) is thoroughly investigated during its pilot and regular operation, based on broadband and frequency selective measurements data derived by the National Observatory of Electromagnetic Fields (NOEF) monitoring sensor network. Insitu measurement data within the 5G NR frequency range are verified via the NOEF's output. The 5G NR contribution to the total E-field levels is assessed in time, from pilot to regular operation of the BS. In all cases, compliance with the reference levels for general public exposure is affirmed.

Frequency-Resolved High-Frequency Broadband Measurement of Acoustic Longitudinal Waves by Laser-Based Excitation and Detection.

Optoacoustics is a metrology widely used for material characterisation. In this study, a measurement setup for the selective determination of the frequency-resolved phase velocities and attenuations of longitudinal waves over a wide frequency range (3-55 MHz) is presented. The ultrasonic waves in this setup were excited by a pulsed laser within an absorption layer in the thermoelastic regime and directed through a layer of water onto a sample. The acoustic waves were detected using a self-built adaptive interferometer with a photorefractive crystal. The instrument transmits compression waves only, is low-contact, non-destructive, and has a sample-independent excitation. The limitations of the approach were studied both by simulation and experiments to determine how the frequency range and precision can be improved. It was shown that measurements are possible for all investigated materials (silicon, silicone, aluminium, and water) and that the relative error for the phase velocity is less than 0.2%.

Temperature Evolution of Magnon Propagation Length in Tm3Fe5O12 Thin Films: Roles of Magnetic Anisotropy and Gilbert Damping.

The magnon propagation length, ⟨ξ⟩, of a ferro-/ferrimagnet (FM) is one of the key factors that controls the generation and propagation of thermally driven magnonic spin current in FM/heavy metal (HM) bilayer based spincaloritronic devices. For the development of a complete physical picture of thermally driven magnon transport in FM/HM bilayers over a wide temperature range, it is of utmost importance to understand the respective roles of temperature-dependent Gilbert damping (α) and effective magnetic anisotropy (Keff) in controlling the temperature evolution of ⟨ξ⟩. Here, we report a comprehensive investigation of the temperature-dependent longitudinal spin Seebeck effect (LSSE), radio frequency transverse susceptibility, and broad-band ferromagnetic resonance measurements on Tm3Fe5O12 (TmIG)/Pt bilayers grown on different substrates. We observe a significant drop in the LSSE voltage below 200 K independent of TmIG film thickness and substrate choice. This is attributed to the noticeable increases in effective magnetic anisotropy field, HKeff (∝Keff) and α that occur within the same temperature range. From the TmIG thickness dependence of the LSSE voltage, we determined the temperature dependence of ⟨ξ⟩ and highlighted its correlation with the temperature-dependent HKeff and α in TmIG/Pt bilayers, which will be beneficial for the development of rare-earth iron garnet based efficient spincaloritronic nanodevices.

Coherent field sensing of nitrogen dioxide.

We introduce a portable dual-comb spectrometer operating in the visible spectral region for atmospheric monitoring of NO2, a pollution gas of major importance. Dual-comb spectroscopy, combining key advantages of fast, broadband and accurate measurements, has been established in the infrared as a method for the investigation of atmospheric gases with kilometer-scale absorption path lengths. With the presented dual-comb spectrometer centered at 517 nm, we make use of the strong absorption cross section of NO2 in this spectral region. In combination with a multi-pass approach through the atmosphere, we achieve an interaction path length of almost a kilometer while achieving both advanced spatial resolution (90 m) and a detection sensitivity of 5 ppb. The demonstrated temporal resolution of one minute outperforms the standard chemiluminescence-based NO2 detector that is commercially available and used in this experiment, by a factor of three.