Wideband Measurements Research Articles

Optimised implicit methods for audio rate wave-based acoustic simulation

Wave-based room acoustic computation at an audio rate (i.e., covering the complete range of audible frequencies) is computationally intensive. There is thus a great incentive to develop simulation methods that allow for "accurate" simulation at the lowest possible computational cost, taking into account requirements for massively parallel implementation. Though often formal measures of order of accuracy are employed, in this paper, we examine the optimisation of a locally-defined implicit family of schemes against wideband measures of accuracy, based on the minimisation of numerical dispersion over a specified frequency range. The resulting optimised scheme is defined over a Cartesian grid, and allows performance gains over standard schemes (such as the basic rectilinear scheme, or schemes defined over face-centered cubic grids, and other implicit designs presented in the literature). Numerical stability conditions are easily formulated, and can be built into the optimisation, alongside the computational cost of linear system solution. Simulation results and comparisons of computation times against other known methods are presented.

An application and discussion of wide-band signal processing technology in the primary calibration for hydrophones

Abstract Wide-band signals are potentially available in the measurement of transducers, which can obtain wide-band responses of electroacoustic parameters of them directly. The hydrophone of B&K 8103 is calibrated in a Φ 1.2 m×1.8 m small water vessel by wide-band signal processing technology in the frequency range of 3.15 kHz to 100 kHz. A thin pellicle co-vibrates with acoustic particle in the free-field, and its oscillation can be detected by a laser Doppler vibrometer, which can estimate the acoustic pressure distribution. The transfer function model is established in a small water vessel, and the wide-band frequency responses of the transfer impedance of transducer and hydrophone as well as the transfer impedance of transducer and pellicle in the small water vessel are calculated respectively. The wide-band signal processing technology of frequency domain filter process are used, which can isolate the reflecting acoustic wave from the boundaries and the surface of the water vessel. To verify the accuracy of the wide-band calibration measurements, the calibration results are compared with that using tone-burst signals in the water vessel and using free-field reciprocity method in the large water tank. The comparisons show that their calibration results are in a good agreement with each other, and the maximum deviation is 0.7 dB. All these demonstrate that the wide-band signal processing technology described is accurate and stable.

Automated Gain Measurement System for Wide-Band Antenna Based on Instruments Remote Access Techniques: Direct SCPI Commands

A novel approach to wide-band antenna gain measurement is presented in this article, offering practical solutions to address the challenges posed by traditional measurement methods. The proposed system enhances efficiency, reduces complexity, and improves accuracy, making it a valuable tool for antenna testing in research and industry settings. A discussion of the challenges and complexities involved in measuring the specifications of manufactured antennas is made. We are particularly focusing on wide-band antenna gain measurement. It highlights the need for special equipment and expertise to conduct these tests effectively, especially for wide-band antennas. The proposed automated measurement system aims to simplify and streamline the gain measurement process by remotely driving the necessary instruments and reducing the complexity of the measurement mechanism. The novelty of this new automated measurement system can be divided into two branches. The first branch improves the standard approach of wide-band antenna gain measurement. The second branch modifies the structure of the software of the traditional remote access applications by mixing the operational instructions of the instrument with the direct SCPI commands. The resulting software has the ability to remotely drive many instruments synchronically, reducing the number of experienced people needed to complete the measurement process.

Wideband Measurement Data Communication Protocol: Scheme Design, Hardware Implementation, and Field Application

Wideband Measurement Data Communication Protocol: Scheme Design, Hardware Implementation, and Field Application

Spectral-interferometry-based diff-iteration for high-precision micro-dispersion measurement

Precise measurement of micro-dispersion for optical devices (optical fiber, lenses, etc.) holds paramount significance across domains such as optical fiber communication and dispersion interference ranging. However, due to its complex system, complicated process, and low reliability, the traditional dispersion measurement methods (interference, phase shift, or time delay methods) are not suitable for the accurate measurement of micro-dispersion in a wide spectral range. Here, we propose a spectral-interferometry-based diff-iteration (SiDi) method for achieving accurate wide-band micro-dispersion measurements. Using an optical frequency comb, based on the phase demodulation of the dispersion interference spectrum, we employ the carefully designed SiDi method to solve the dispersion curve at any position and any order. Our approach is proficient in precisely measuring micro-dispersion across a broadband spectrum, without the need for cumbersome wavelength scanning processes or reliance on complex high-repetition-rate combs, while enabling adjustable resolution. The efficacy of the proposed method is validated through simulations and experiments. We employed a chip-scaled soliton microcomb (SMC) to compute the dispersion curves of a 14 m single-mode fiber (SMF) and a 0.05 m glass. Compared to a laser interferometer or the theoretical value given by manufacturers, the average relative error of refractive index measurement for single-mode fiber (SMF) reaches 2.8×10−6 and for glass reaches 3.8×10−6. The approach ensures high precision, while maintaining a simple system structure, with realizing adjustable resolution, thereby propelling the practical implementation of precise measurement and control-dispersion.

Wideband Measurement Approach for EIS of Lithium-Ion Batteries Using Low-Frequency Concentrated Disturbance

Precise and rapid measurement for electrochemical impedance spectroscopy (EIS) is conducive to the working state monitoring and fault diagnosis of lithium-ion batteries (LIBs). Although using a wideband signal can effectively reduce measurement time, it will deteriorate the measurement precision due to the insufficient Signal-to-Noise Ratio. Considering this issue, this paper proposes a wideband measurement approach using low-frequency concentrated disturbance for the EIS of LIBs. This approach can obtain high measurement accuracy and a wide measurement bandwidth under a small current disturbance. Besides, it effectively reduces the measurement time. First, LIBs are stimulated by a low-frequency concentrated binary sequence signal to enhance measurement precision in a low-frequency region. Then, in the entire frequency region, an accurate EIS can be obtained by a fast Morlet wavelet transform and covariance-based impedance calculation. Finally, the effectiveness of the proposed approach is verified on a buck-boost converter-based EIS measurement platform, and comparative analyses with literature methods are conducted. The experimental results illustrate that the maximum Normalized Root Square Error of the two types of LIBs at different state-of-charge is 0.37% under the response voltage amplitude of less than 10mV. Moreover, this approach is approximately 20 times faster than commercial electrochemical workstations in measurement time.

Design and experiment of the simulated electronic corn ear based on UWB/IMU technology

In order to explore kinematic and dynamic parameters of corn ear in the process of threshing, and reveal threshing principle and grain impact damage mechanism, a simulation electronic corn ear was designed based on ultra wide band (UWB) and inertial measurement unit (IMU) technology. The spatial positioning algorithm and impact force analysis algorithm of electronic corn ear were studied, and a simulated threshing test bench was built. Then free fall impact force detection test and comprehensive performance test of the electronic corn ear were carried out. The experimental results showed that the average detection error of free fall impact force was about 0.69 N, with an accuracy more than 95 %, and the average detection error of impact force in the process of simulation threshing was about −0.27 N, with an accuracy more than 97 %. The spatial positioning accuracy of electronic corn ear was related to the number, layout and positioning algorithm of UWB positioning base station. Unscented kalman filter (UKF) tight combination positioning algorithm had the highest positioning accuracy (about 100 % probability of positioning error within ± 0.15 m) under the condition of non-line of sight (NLOS) (5 base stations, 3.2 m height difference). Extended kalman filter (EKF) tight combination positioning algorithm had the second highest positioning accuracy (about 100 % probability of positioning error within ± 0.2 m), followed by kalman filter (KF) loose combination, UWB single positioning and IMU single positioning algorithm. The results are helpful for obtaining kinematic and dynamic parameters in the process of ear threshing and separation, understanding the mechanism of efficient and low-damage threshing, and provide a basis for the segmented optimization design of subsequent devices.

Affordable wide-band measurement ecosystem for musical acoustics based on electro-dynamic transducers

The variability in responses of acoustic instruments can be attributed to a combination of fluctuations in critical parameters of wood, such as density, stiffness, and strength, and design features such as body shapes or bracing geometries. Recent studies have successfully implemented the sine sweep method with small exciters to measure the acoustic response of guitars, yielding frequency responses with high coherence over a bandwidth reaching up to 8 kHz. This paper proposes validating a cost-effective measurement system which integrates electro-dynamic transducers and wide-band test signals (sine sweep and noise) against the traditional impact hammer method in the case of unbraced plates. Data from four actuators of different size and power will be presented together with a simple strategy to assess reliable and neutral excitation points, thanks to two complementary models which describe the interaction between exciter and plate. The paper will then showcase the applications of this measurement system in two scenarios. The first case study will focus on a cost-effective method for selecting acoustic wood, while the second will explore experimental real-time spectral analysis using pink noise. These case studies demonstrate the measurement system’s adaptability and immediacy, providing valuable insights for enhancing the design and performance of acoustic instruments.

Assessing the vulnerability of solar inverters to EMPs: Port testing, PCI modeling, and protection strategies

Renewable energy sources are becoming an ever-larger contributor to the power grid. These renewable energy sources depend upon the power electronic devices, specifically inverters, being essential for connecting Photovoltaic (PV) generation to the grid. However, the Electromagnetic Pulses (EMPs) caused by the high-altitude nuclear explosions can generate fast broad-band pulses with nanosecond rise time, potentially causing damage or destruction to electronic components. To assess the vulnerability of PV inverters to high-altitude EMPs, the port testing and Pulsed Current Injection (PCI) modeling schemes are proposed based on the port impedance analysis. Wide-band frequency measurements are achieved by fusing impedance results from three vector network analyzers. Then, a PCI model is used to simulate the induced response to EMP, with two typical immunity levels of EC5 and EC8 tested. The experiment successfully excites the induced voltage and current under EMP, where the voltage and current can reach 1500V/40A and 8000V/150Aunder EC5 andEC8, respectively. The port vulnerability analysis results demonstrate that only some ports can survive under EC5. To defend against the impact of EMP, three protection strategies are discussed.

Frequency Scanning of Weakly Damped Single-Phase VSCs With Chirp Error Control

The chirp sweep is a go-to wide-band impedance measurement technique when speed and simplicity are of main concern. Additionally, the time-frequency trait of chirp scans provide unique benefits for systems exhibiting frequency couplings - a phenomenon often encountered in single-phase VSCs. Unfortunately, time domain interpretation of chirp responses are inaccurate if the VSC-based system exhibits weak damping, as the transient response induced by the chirp cannot be safely neglected. We quantify this error for linear(ised) time-invariant and time-periodic systems, with impedance representations of scalar transfer functions and harmonic transfer functions, respectively. An observer termed the Multiple Chirp Reference Frame Filter is proposed which enables real-time estimation of the harmonic transfer functions and their corresponding chirp errors. By controlling the relative errors to negligible values, the chirp exhibits low rate around resonances and high rate elsewhere. An experimental admittance sweep of a single-phase STATCOM operated by dispatchable Virtual Oscillator Control, consolidates the proposed approach as a simple frequency scan technique for weakly damped and frequency coupled systems.

A Linear-Scan-Based Wideband Single-Cut Near-Field RCS Measurement Technique With Wide Effective Angle Coverage

A linear-scan-based wideband near-field radar cross section (RCS) measurement technique for achieving wide effective-angle-coverage is proposed in this letter. Both the data preprocessing and linear near-field to far-field transformation (LNF2FFT) techniques are used to ensure the accurate measurement of wideband far-field RCS in a wide azimuthal angle range. With the linear-scan-based near-field sampling strategy, the object under test (OUT) keeps stationary during the measurement process, and the equipment of turntable is not required. Moreover, based on the 2D plane wave expansion, LNF2FFT is proposed to translate the linearly sampled near-field data into far-field RCS pattern. An adaptive time gating strategy is also proposed to deal with the varied background property in liner samplings. Serval important practical factors relating to the measurement accuracy, such as phase center calibration, background subtraction and calibration, are also discussed in detail. Two illustrative test examples are presented, in which RCS measurement with wide effective-angle-coverage of ±35° and the average wideband measurement errors less than 0.4 dB are achieved in 1 m limited measurement range.

Wideband TDoA Positioning Exploiting RSS-Based Clustering.

The accuracy of radio-based positioning is heavily influenced by a dense multipath (DM) channel, leading to poor position accuracy. The DM affects both time of flight (ToF) measurements extracted from wideband (WB) signals-specifically, if the bandwidth is below 100 MHz-as well as received signal strength (RSS) measurements, due to the interference of multipath signal components onto the information-bearing line-of-sight (LoS) component. This work proposes an approach for combining these two different measurement technologies, leading to a robust position estimation in the presence of DM. We assume that a large ensemble of densely-spaced devices is to be positioned. We use RSS measurements to determine "clusters" of devices in the vicinity of each other. Joint processing of the WB measurements from all devices in a cluster efficiently suppresses the influence of the DM. We formulate an algorithmic approach for the information fusion of the two technologies and derive the corresponding Cramér-Rao lower bound (CRLB) to gain insight into the performance trade-offs at hand. We evaluate our results by simulations and validate the approach with real-world measurement data. The results show that the clustering approach can halve the root-mean-square error (RMSE) from about 2 m to below 1 m, using WB signal transmissions in the 2.4 GHz ISM band at a bandwidth of about 80 MHz.

Development of Wide-band Ground Impedance Measurement System based on LabVIEW for Grounding System Evaluation

Development of Wide-band Ground Impedance Measurement System based on LabVIEW for Grounding System Evaluation

Fast optical vector network analysis based on dual optical frequency comb

An ultrafast optical vector network analysis (OVNA) based on dual optical frequency comb (OFC) and I/Q demodulation technology is proposed and demonstrated. The responses of the DUT with broadband are characterized by propagating the signal OFC through the DUT, and then detecting interference signals using digital signal processor with retrieval algorithm. Without the need of the acousto-optic modulator or optical filter in the scheme, the frequency aliasing can be eliminated by using the I/Q demodulation module, so that the spectral utilization efficiency of the OFC is improved significantly. Meanwhile, the wideband measurement with high acquisition rates can also be achieved. In simulation process, the single spectrum of HCN molecule with linewidth of 1 GHz and bandwidth of 10 GHz can be rapidly measured, and the measurement time is only 1μs in theory. Our proposed OVNA opens the door to realize a real-time detection in the field of trace molecular sensing.

Measurement‐based omnidirectional millimetre‐wave and sub‐THz propagation analysis in a large cubicle office environment

AbstractFor 5G beyond and/or 6G mobile services, a new spectrum at frequencies above 100 GHz has received great attention lately. To characterise the similarities and the differences between frequencies below 100 GHz and above 100 GHz, this paper provides analyses of multi‐frequency propagation characteristics based on wideband measurements at 28, 38, 71, 82, and 159 GHz, with an emphasis on the sub‐THz (i.e. the 159 GHz) propagation characteristics. All the frequency measurements were conducted in the same cubicle office room environment by locating the transmitter and the receiver at the same positions. The measurement results show that the path loss and the shadow fading characteristics do not exhibit significant differences depending on the frequency range from 28 to 159 GHz. However, the delay spread shows a generally decreasing trend as the frequency increases. Additionally, angular domain analyses were conducted with the 159 GHz measurements.

Optimal Configuration of Distribution Network Wideband Measurement Unit Considering Wideband Measurement

With the large-scale integration of distributed generation (DG) and the increase in interaction with users, a large amount of wide-band information other than power frequency has been introduced into the distribution networks. The synchronous wide-band measurement is an important means to improve the situational awareness ability of the distribution network operation, hence, its optimization configuration has received more and more attention. To achieve the full observability of the network with the least measurement devices and achieve the goal of more accurate wide-band state estimation, this paper proposes a deployment method considering the wide-band information and the topology observability. Under the premise of ensuring that the network is completely observable, by comprehensively considering the redundancy of measurement and the conditioning number of the measurement matrix as well as the attenuation characteristics of the wide-band signal, the observability of the nodes considering wide-band information is re-determined and the topology matrix is modified. Simulation and analysis are carried out in the IEEE34 node distribution network system to verify the reliability and effectiveness of the proposed method.

Effects of Fire Plumes From Pine Needles on Small-Scale Fading in Radiowave Propagation

In this article, radiowave fading caused by fire plumes due to the burning of heaps of pine needles is studied. Detailed characterization of the fire impact in terms of excess loss due to the yielded plumes at UHF frequencies, mainly in the L-band, when considering two different ignition sources, is also presented. The implemented small-scale fire scenario is composed of a 1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 1$ </tex-math></inline-formula> m metallic grid covered with a 0.6 kg pine needle fuel bed that was placed right above a circular and linear gas burner to mimic an underbrush scenario. The propagation phenomena were evaluated through specific wideband measurements as the fire developed while intersecting the radio path at the antennas’ boresight. Results demonstrate changes in the propagation medium that is strongly influenced by the plume, which ultimately becomes (partly) ionized. Deep fades of up to 12 dB below median levels at specific frequencies during a short period of time, when the fire is more intense, were measured. We also obtained an overall median excess loss due to fire of up to 2 dB in the frequency range from 0.6 to 2 GHz in a relatively short path (below 1 m). A time-domain analysis allowed us to expand these results yielding fading values of the direct component of more than 3 dB in the presence of fire. Extending the findings presented in this article to a real-scale fire scenario, in which median excess loss of more than 20 dB and deeper nulls are ought to be expected, sets the rationale and motivation to pursue future work on the topic, with practical relevance to future mission-critical communication networks planning, such as, but not limited to, LTE Public-Safety and specific 5G use cases.

Fundamental Concepts for Assessment and Interpretation of Wideband Acoustic Immittance Measurements.

Assessment of middle ear impedance using noninvasive electroacoustic measurements has undergone successive developments since its first clinical application in the 1940s, and gained widespread adoption since the 1970s in the form of 226-Hz tympanometry, and applications in multifrequency tympanometry. More recently, wideband acoustic immittance (WAI) is allowing unprecedented assessments of the middle ear acoustic mechanics thanks to the ability to record responses over a wide range of frequencies. The purpose of this article is to present fundamental concepts for the assessment and interpretation of wideband measures, including a review of acoustic impedance and its relation to the mass, stiffness, and resistance components of the middle ear. Additionally, an understanding of the middle ear transfer function reveals the relationship between impedance and middle-ear gain as a function of frequency. Wideband power absorbance, a WAI measure, quantifies the efficiency of sound conduction through the middle ear over a wide range of frequencies, and can serve as an analogous clinical measure to the transfer function. The interpretation of absorbance measures in ears with or without a conductive condition using absorbance measured at ambient pressure and pressurized conditions (wideband tympanometry) is described using clinical case examples. This article serves as an introduction to the fundamental principles of WAI measurements.

Wideband Measurement of Dielectric Properties of Wheat Flour

Use of electromagnetic (EM) fields in the food industry for food inspection as well as sterilization and drying is increasing. To develop such applications, the knowledge of the dielectric properties of food is fundamental. In the literature, there is scarcity of data on dielectric properties of powdered foods, with reported values that are usually at specific frequencies only. This article reports the development of an experimental framework to characterize the dielectric properties of powdered food over a wide range of frequencies. The used methodologies include the open-ended coaxial probe technique and waveguide systems: the first being intrinsically a broadband technique but strongly dependent on the type of material being tested, and the latter being a medium- to narrowband technique allowing a better control of the tested material. The proposed framework is then used to measure the dielectric properties of several types of flour between 500 MHz and 20 GHz. The measured properties are then characterized in terms of density and interpolated with a Cole–Cole dispersive model. From the measured results, the suitability of the proposed setup was demonstrated. Additionally, it was verified that the permittivity of flour does not depend on the brand and can be expressed as a function of the density of the material, following a mixture formula already proposed in the literature. Moreover, the proposed Cole–Cole fit is able to represent the frequency behavior of the real part of permittivity of flour with differences within 3% from the measured data.

Wideband Near-Field RCS Measurement Techniques With Improved Far-Field RCS Prediction Accuracies

Wideband near-field (NF) radar cross section (RCS) measurement techniques for improving the far-field RCS prediction accuracies are addressed in this article. Both the data preprocessing and NF-to-far-field transformation (NF2FFT) techniques are used to accurately measure wideband far-field RCSs in a wide azimuthal angle range. By utilizing the calibration set creation and some wideband data preprocessing techniques, including the vector background subtraction, the time-domain calibration and compensation, the time-gating steps, as well as the cylindrical mode expansion or the imaging-based NF2FFT techniques, the accurate wideband far-field RCSs in a wide azimuthal angle range can be obtained with the limited NF measurement range. Both the poor measurement accuracy and dynamic range as well as the main lobe distortion and angular undersampling effects existing in the NF measured raw data can be improved significantly. The proposed techniques are validated with an 8–12-GHz measurement of a 0.5-m-length cone target (in a 3-m measurement range, compared with the at least 30-m far-field range requirement), and the obviously improved RCS patterns and less than 0.5-dB average wideband measurement errors are achieved.