Time-domain Measurement Method Research Articles

Dynamic transient response measurement method for parity-time-symmetric LC telemetry sensors

Parity-time symmetry concept has been utilized to develop high precision LC passive wireless sensors. However, they often use the traditional frequency sweeping method for measurements, thus the measurement precision and speed are strongly influenced by the performance of the frequency domain analysis instrument. To solve this issue, herein we proposed a time domain measurement method and extracted sensing information from the transient response signals of the reader. Its measurement speed was much faster than that using the frequency domain analysis instrument. A distance sensing system was developed to demonstrate the feasibility of the new method. It showed a resolution of less than 300 nm for detections of centimeter range, and the measurement time was as short as 100 μs, which was at least 1000 times faster than that using the traditional method. This technology can be explored as an innovative strategy for LC passive telemetry sensing.

Continuous Time-Domain Measurement Method of Rayleigh Backscattered Light With Coherent Detection

This paper shows the results of continuous time-domain measurement of Rayleigh backscattered light. Experimental results show that we can measure the variation of the phase of the backscattered light from a specific point of the fibers where we applied sinusoidally varying stress at a frequency of 140 kHz. We expect that the method will find application to continuously measure the rapid variation of external perturbation in the time domain at a specific point in the fibers.

On-Chip Slow-Light SiN Bragg Grating Waveguides

Si photonic foundry fabricated cascaded and continuous spiral shaped silicon nitride (SiN) waveguides that incorporate Bragg grating structures were explored to produce an on-chip true-time delay line. A time-domain measurement method was used to characterize the delay time of the grating waveguides near their photonic band edge where it exhibits the strongest slow light effect. The highest group index extracted from cascaded SiN grating waveguides is 19.7 corresponding to a total delay time of 5.48 ns in a full length of 12.49 cm that consumes a surface area of 2.66 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . A continuous spiral SiN grating waveguide was also fabricated which produces a delay time of 3.78 ns in a length of 5.47 cm with a surface area consumption of 0.88 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Technology for the Detection of Ablation Defects in Buffer Layers of High-Voltage Cables

This article discusses the main structure of HV cables as well as the characteristics of buffer layers and detection of ablation defects. To effectively detect ablation defects in the buffer layer, two approaches, terahertz time-domain measurements and commercial computed tomography (CT), were used in the laboratory to evaluate samples of cable with these defects and compare different preset conditions for detecting defects. The test results showed that the terahertz time domain measurement method was more sensitive than CT to moisture intrusion into the cable, but terahertz wave energy was reflected on the surface of the aluminum sheath of the cable and could not penetrate the sheath, thus, it was difficult to use this method to detect internal defects. The commercial CT method used X-rays to penetrate the aluminum sheath, and it could effectively obtain data for the three-dimensional reconstruction of each layer of material, other than the copper core. The structure of the cable was mapped through three-dimensional reconstruction using VGstudio Max software, and the three-dimensional map and gray value analysis were combined. The results confirmed that defects with different densities in the buffer layer could be detected by commercial CT. Thus, commercial CT detection methods provide an effective solution for identifying hidden defects in cables and have profound practical significance for the development of methods to detect defects when cables are in use.

A measurement method for lossy capacitive relative humidity sensors based on a direct sensor-to-microcontroller interface circuit

A new time-domain measurement method for determining the capacitance and resistance values of lossy relative humidity capacitive sensors is presented. The method is based on a direct sensor-to-microcontroller interface for microcontrollers with internal analog comparators and timers. The interface circuit consists only of four reference resistors (two reference resistors if a microcontroller includes a voltage reference source), a given sensor and a microcontroller. A systematic error correction algorithm based on a correction dictionary and the M-multiple measurement approach are also proposed in the paper. Experimental investigations were carried out using a prototype device based on an 8-bit ATXmega32A4 microcontroller. The experimental research confirmed that the relative errors of measurement of capacitance introduced by the interface circuit are less than 0.71% (for capacitance values 100–286pF), and the relative errors of measurement of resistance are less than 0.74% (for resistance values 1–10MΩ).

A measurement method for capacitive sensors based on a versatile direct sensor-to-microcontroller interface circuit

In the paper, there is presented a new time-domain measurement method for determining the capacitance values of capacitive sensors, dedicated, among others, to capacitive relative humidity sensors. The method is based on a versatile direct sensor-to-microcontroller interface for microcontrollers with internal analog comparators (ACs) and with precision voltage reference sources, e.g. digital-to-analog converters (DACs). The reference source can be replaced by a resistive divider attached to the negative input of the AC. The interface circuit consists only of a reference resistor Rr, a given capacitive sensor working as a voltage divider, and a microcontroller (its peripherals: AC, timer, DAC, I/O pins). A prototype of the proposed complete solution of a compact capacitive smart sensor based on an 8-bit ATXmega32A4 microcontroller has been developed and tested. The maximum possible relative inaccuracy of an indirectly measurable capacitance was analysed, and experimental research was also performed. The results confirmed that the relative errors of value determination for a capacitive sensor are less than ±0.06%, which corresponds to a capacitance measurement accuracy of less than 0.1 pF for a range of measured capacity values from 100 pF to 225 pF, which in turn corresponds to at least a 0.5% relative humidity resolution for commercial capacitive RH sensors (e.g. TE Connectivity HS1101LF and Philips H1).

Time-domain measurement methods for R, L and C sensors based on a versatile direct sensor-to-microcontroller interface circuit

In the paper new time-domain measurement methods for determining values of resistive (R), inductive (L) and capacitive (C) sensors based on a versatile direct sensor-to-microcontroller interface for microcontrollers with internal analog-to-digital converters (ADCs) and analog comparators (ACs) are presented. The interface circuit consists of a reference resistor Rr working as a voltage divider, a given R, L or C sensor and a microcontroller (its peripherals: an ADC, an AC, a timer, I/O pins buffered by an inverter). A prototype of the proposed complete solution of a compact smart sensor based on an 8-bit microcontroller has been developed and tested. The maximum possible relative inaccuracy of an indirectly measurable resistance, inductance and capacitance were analysed. Also, experimental researches were made. The following relative errors of the sensor value determination were achieved: for the R sensor less than 3%, as well as very good results for the L sensor (less than 0.3%) and for the C sensor (less than 0.2%).

Analysis of Photonics-Based RF Beamforming With Large Instantaneous Bandwidth

Since the photonics-based true time delay could significantly broaden the instantaneous bandwidth of a phased antenna array system, solutions utilizing wideband signals could be enabled to considerably enhance the functionality and performance of RF systems. To investigate the features of the wideband beamforming, a comprehensive theoretical model is developed in this paper to analyze the photonics-based broadband beamforming network for uniform linear arrays. In the proposed model, the performance of the beamforming network over the operational frequency band is intuitively depicted through a two-dimensional spatial-temporal frequency response, in which both the spatial frequency (or the corresponding observation angle) and the temporal frequency are adopted as independent variables. In addition, cross correlation of the original signal and the signal that undergoes the beamforming network is calculated to define a wideband pattern and a new figure of merit, so that the waveform-dependent overall response over a large bandwidth can be evaluated. Based on the theoretical model, a time-domain method for pattern measurement is proposed and experimentally demonstrated, which offers the coincident result as the frequency-domain method but is more convenient to be conducted. Numerical results of several typical photonics-based beamforming structures are presented to investigate the impact of nonidealities on the two-dimensional response and the proposed figure of merit.

Application of LMS Algorithm to Measure Low-Frequency Transient Forces from Human Walking

Measurement and modeling of low frequency ground reaction forces (GRFs) from human walking have been the subjects of research in different fields from biomechanics to civil engineering and structural dynamics. Many of the existing models are developed based on experiments which alter natural walking by for example presence of force transducers, limitations in the speed and path of walking and replacing the real floor with a transducerfacilitated measurement rig. These alterations result in contact forces which do not represent real GRFs. In this study, a time-domain inverse measurement method based on LMS algorithm is used to measure low-frequency (<100 Hz) forces induced by human footsteps. The LMS-based force identification method is first validated for low-frequency excitations with less complexity in number of excitation positions and frequency content compared with the footsteps. The method is then applied to measure ground reaction forces created by human walking.

Research on Broadband Channel Characteristics and Hardware Testbed for Power Line Communication System

With the decision to construct the smart grids around China, the power line communications (PLC) on the low-voltage (LV) distribution networks have become one of the potential technologies to commute the information between the end users and the power provider. Comprehensive and well-founded knowledge of the LV power line channel is the foundation to establish realistic modeling of the channel characteristics. The growing power line communication (PLC) technology is providing new potential for emerging applications such as G3 and Prime. In this paper, we have proposed a OFDM based channel sounding test bed to measure PLC channel within frequency band 100 kHz-2 MHz. A souding signal for the PLC channel is designed and a time-domain measurement method for the time-varying PLC propagation is presented. The experimental results of PLC channel characteristics under different scenarios are and analyzed.

Accuracy Analysis of Quality Factor Measurement Based on Time Domain Method for MEMS Resonators

To reduce the measurement cost and time, a time domain measurement method of quality factor for MEMS resonator is presented in this paper. The relation curve between quality factor and vacuum level is obtained. The results indicate that measurement error is larger under high vacuum level when the sampling frequency is lower. The reason causing the error is analyzed and measurement precision is improved by increasing the sampling frequency. The measurement results indicate time domain measurement is advisable and improvable for MEMS resonator measurement.

Infrared Optical Activity: Electric Field Approaches in Time Domain

Vibrational circular dichroism (VCD) spectroscopy provides detailed information about the absolute configurations of chiral molecules including biomolecules and synthetic drugs. This method is the infrared (IR) analogue of the more popular electronic CD spectroscopy that uses the ultraviolet and visible ranges of the electromagnetic spectrum. Because conventional electronic CD spectroscopy measures the difference in signal intensity, problems such as weak signal and low time-resolution can limit its utility. To overcome the difficulties associated with that approach, we have recently developed femtosecond IR optical activity (IOA) spectrometry, which directly measures the IOA free-induction-decay (FID), the impulsive chiroptical IR response that occurs over time. In this Account, we review the time-domain electric field measurement and calculation methods used to simultaneously characterize VCD and related vibrational optical rotatory dispersion (VORD) spectra. Although conventional methods measure the electric field intensity, this vibrational technique is based on a direct phase-and-amplitude measurement of the electric field of the chiroptical signal over time. This method uses a cross-polarization analyzer to carry out heterodyned spectral interferometry. The cross-polarization scheme enables us to selectively remove the achiral background signal, which is the dominant noise component present in differential intensity measurement techniques. Because we can detect the IOA FID signal in a phase-amplitude-sensitive manner, we can directly characterize the time-dependent electric dipole/magnetic dipole response function and the complex chiral susceptibility that contain information about the angular oscillations of charged particles. These parameters yield information about the VCD and VORD spectra. In parallel with such experimental developments, we have also calculated the IOA FID signal and the resulting VCD spectrum. These simulations use a quantum mechanical/molecular mechanical molecular dynamics (QM/MM MD) method and calculate the electric dipole/magnetic dipole cross-correlation function in the time domain. Although many quantum chemistry calculation approaches can only consider a limited number of geometry-optimized conformations of chiral molecules in a gas phase, this computational method includes the solute-solvent interactions and the inhomogeneous distributions of solute conformers in condensed phases. A subsequent Fourier transformation of the chiral response function produced a theoretical VCD spectrum in the entire mid-IR frequency range. Directly comparing theory and experiment, we demonstrate quantitative agreement between frequency-tunable femtosecond IOA measurements and QM/MM MD simulations of (1S)-β-pinene in CCl(4) solution. We anticipate that these direct IOA measurement and calculation methods will be applied to the studies of equilibrium chiroptical properties and structure determinations. These methods provide tools to investigate ultrafast structural dynamics of chiral systems with unprecedented time resolution.

Design Optimization of UWB Printed Antenna for Omnidirectional Pulse Radiation

The use of ultrawideband technology in many applications implies the use of a suitable radiating structure, especially for pulsed systems. The development of a triangular CPW-fed printed antenna with specific ground plane shape is presented. First the triangular element was optimized to minimize return losses and size of the antenna in the [3.1-10.6] frequency band. The evolution of radiation patterns with frequency was also studied, as changes in phase center position and radiation characteristics alter the integrity of transmitted pulses. Thus the antenna ground plane shape was modified in order to maintain almost constant radiation patterns over the entire bandwidth. Time domain measurement methods were used to characterize the antennas and validate these improvements. The procedure is presented and results are plotted in a 3D format and discussed.

Low coherent hybrid detection technique for differential mode delay in a multimode optical fiber

We present a low coherent hybrid detection technique for the differential model delay (DMD) measurement of a conventional optical multimode fiber with a modified Mach-Zehnder interferometer. A low coherent hybrid detection technique enhances mode coupling between guided modes and the reference mode to easily resolve the modal distribution. An optical spectrum analyzer and a broadband source were used to obtain time-resolved optical beat signals. The measured interference signal was Fourier transformed to obtain time-delay information. A scanning offset launching method was used to excite every available mode in a multimode fiber (MMF). Measurements of a conventional 8-m-long MMF demonstrated the validity of our proposed method. The experimental results of our proposed method agree well with results obtained using a conventional time domain measurement method. Our proposed method can be used to measure the DMD in a short length of optical MMF with a temporal resolution better than 0.72 ps when using an 8-m-long single-mode fiber as a reference.

Frequency-domain modal delay measurement for higher-order mode fiber based on stretched pulse interference

We propose and demonstrate a novel modal delay measurement technique for a higher-order mode fiber (HOF) based on optical frequency-domain reflectometry (OFDR) using an extremely simple, entirely passive, and ultrafast wavelength sweeping mechanism, namely, dispersion-induced optical pulse stretching. We obtained a high temporal resolution of approximately 1.12 ps, which was sufficient for discerning the four excited modes in an HOF with a length of only approximately 5 m. The results from our measurements were very consistent with those obtained by using a traditional time-domain measurement method and a conventional OFDR measurement based on a tunable CW laser. Our proposed technique can be also easily adapted to perform conventional time-domain modal delay measurements for very long HOFs.

Fourier-domain low-coherence interferometry for differential mode delay analysis of an optical fiber

We propose a novel mode analysis and differential mode delay measurement method for an optical fiber using Fourier-domain low-coherence interferometry. A spectral interferometer based on a Mach-Zehnder interferometer setup was used with a broadband source and an optical spectrum analyzer to detect relative temporal delays between the guided modes of a few-mode optical fiber by analyzing spectral interference signals. We have shown that experimental results of the proposed method agree well with those results obtained by using a conventional time-domain measurement method. We have demonstrated that this new mode analysis technique has high sensitivity (<60 dB) and very good resolution (<1 ps/m).

An Overview of Electrical Characterization Techniques and Theory for IC Packages and Interconnects

This paper reviews current approaches to the electrical characterization and modeling of IC packages and interconnects. An overview of both frequency and time-domain measurement methods and summaries of equivalent circuit model selection and extraction methodologies are included. Additionally, an overview of numerical methods for electromagnetic modeling is included for completeness. Finally, relevant case studies from the literature are summarized to further supplement the discussed techniques. The focus is primarily on high-frequency signal related characterization and power integrity issues are not directly considered in this paper. This paper is presented in the context of the growing requirement for package and interconnection electrical models for high-speed and miniaturized systems.

Determination of the differential mode delay of a multimode fiber using Fourierdomain intermodal interference analysis

We present a novel differential mode delay (DMD) measurement method for a multimode optical fiber (MMF) based on Fourier-domain lowcoherence interferometry (fLCI) for the first time. An optical spectrum analyzer and a mode scrambler are used to obtain the intermodal interference signal in spectral domain after light passes an MMF. The MMF is used as a common path interferometer by itself without using any reference arm in an interferometer. Instead of using an offset launching technique, we present an effective method to obtain all available intermodal interference signals at a single shot by using a mode scrambler. The measured results using the proposed method are compared with those obtained using a conventional time-domain DMD measurement method.

Time Domain Measurement of Moving Object Speed Using Acceleration Sensor

In this study, we proposed a time-domain measurement method of moving object speed with a commercially available acceleration sensor. The sensor of this kind is normally used to measure the acceleration of a stationary vibration object, while it is not applicable to the measurement of a transient moving object due to the frequency response of the sensor itself. An impulsive sensor response was derived from the free-drop movement of a metallic sphere. The deconvolution allows the sensor to measure the acceleration in the time domain, which was validated through the measurement of the speed of a hand-held metal piece approaching a target.

Mode Analysis and Modal Delay Measurement of a Few-Mode Fiber by Using Optical Frequency Domain Reflectometry

A novel mode analysis method and differential mode delay measurement technique for a multimode optical fiber based on optical frequency domain reflectometry has been proposed for the first time. We have used a conventional OFDR with a tunable external cavity laser and a Michelson interferometer. A few-mode optical multimode fiber was prepared to test our proposed measurement technique. The differential mode delay (DMD) of the sample fiber was measured to be 16.58 ps/m with a resolution of 1.5 ps/m. We have also compared the OFDR measurement results with those obtained using a traditional time-domain measurement method.