Time-domain Measurement Technique Research Articles

Algebraic reconstruction and postprocessing in one-step diffuse optical tomography

The photon average trajectory method is considered, which is used as an approximate method of diffuse optical tomography and is based on the solution of the Radon-like trajectory integral equation. A system of linear algebraic equations describing a discrete model of object reconstruction is once inverted by using a modified multiplicative algebraic technique. The blurring of diffusion tomograms is eliminated by using space-varying restoration and methods of nonlinear colour interpretation of data. The optical models of the breast tissue in the form of rectangular scattering objects with circular absorbing inhomogeneities are reconstructed within the framework of the numerical experiment from optical projections simulated for time-domain measurement technique. It is shown that the quality of diffusion tomograms reconstructed by this method is close to that of tomograms reconstructed by using Newton-like multistep algorithms, while the computational time is much shorter.

Frequency-domain intermodal interferometer for the bandwidth measurement of a multimode fiber

A new bandwidth measurement technique for a multimode optical fiber (MMF) using a frequency-domain intermodal interferometer is proposed. We have demonstrated that the relative modal delay (RMD) of a MMF can be obtained easily and accurately based on an optical frequency-domain reflectometry (OFDR) technique by using an intermodal interference signal among the excited modes of a MMF. As an example, a photonic crystal fiber with a few modes is prepared and its RMD is measured by using our proposed measurement technique. Measurement results are compared with those from a previously reported frequency-domain method. We have also measured the RMD of a commercial MMF as a practical application and compared our result with the one obtained from a well-known time-domain differential mode delay measurement technique.

Antennas and Propagation Measurement Techniques for UWB Radio

The progressive development of Ultra Wide Band (UWB) antennas and microelectronics allows for a wide range of future UWB radio communication applications. The paper focuses on testing and measuring various antennas and propagation aspects important in UWB radio. The `Delft approach' of measuring UWB antennas using time-domain measurement techniques is explained including the diagnostics of antenna mismatch and wave scattering from the inside and the antennas environment. The approach is illustrated with measurements. The experimental time-domain set up allows instantaneous measurements up to 26GHz. After an overview of various UWB antennas some latest developments of a miniaturized antenna are reported. UWB channel measurements in `short-range radio' illustrates that good insight in the propagation of short radar pulses can be obtained.

Shielding of Electronic Systems against Transient Electromagnetic Interferences

Abstract. In order to protect electronic systems against the effects of transient electromagnetic interferences, shields made of electrically conductive material can be used. The subject of this paper is an electrically conductive textile. When applying the shield, a reliable measure is needed in order to determine the effectiveness of the shield to protect against electromagnetic pulses. For this purpose, a time domain measurement technique is presented using double exponential pulses. With these pulses, the susceptibility of an operating electronic device with and without the shield is determined. As a criterion of quality of a shield, the breakdown failure rate found in both cases is compared.

Review of time-domain polarization measurements for assessing insulation condition in aged transformers

This paper presents a review of the time-domain polarization measurement techniques for the condition assessment of aged transformer insulation. The polarization process is first described with appropriate dielectric response theories and then commonly used polarization methods are described with special emphasis on the most widely used (RV) measurement. Most recent emphasis has been directed to techniques of determining moisture content of insulation indirectly by measuring RV parameters. The major difficulty still lies with the accurate interpretation of return voltage results. This paper investigates different thoughts regarding the interpretation of RV results for different moisture and ageing conditions. Other time domain polarization measurement techniques and their results are also presented in this paper.

Time-domain measurement and modeling techniques for wideband communication components and systems

The measurement and characterization of RF and microwave components and systems has been dominated by a tone-based frequency-domain paradigm because of its simplicity and accuracy. This review article describes new and accurate time-domain techniques that are superior for application to wideband and nonlinear contexts. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13: 5–31, 2003.

Time-domain measurement of pulse-timing fluctuations in a mode-locked laser diode

Time-domain measurement techniques have been applied to the evaluation of pulse timing fluctuations in a monolithic mode-locked laser diode operating at 20 GHz. The time interval analysis and the time-domain demodulation techniques, both developed by the present author, are utilized for the evaluation of passively and hybrid mode-locked lasers, respectively. Phase noise power spectral densities have been measured from 2.5 to 34 MHz Fourier frequency with 300-dB dynamic range.

One-port time-domain measurement of the approximate permittivity and permeability of materials

Single-port frequency-domain measurements to determine the electrical characteristics of a material are often made for liquids or amorphous solids (water, dirt, biological material, etc.). Before yielding the desired property, the corresponding data-reduction procedure requires an assumption of the value of either the permittivity of permeability (often one chooses /spl mu//sub r/=1). This paper describes a one-port time-domain measurement technique that can yield the approximate broad-band frequency-dependent complex values of permittivity and permeability for a sample material. A description of the procedure is given, the governing equations are derived, and two examples (one with simulated data and the other with measured data) with representative waveforms and results are presented.

Comparison between Time-domain and Frequency-domain Measurement Techniques for Mantle Shear-wave Attenuation

—We study the frequency- and time-domain techniques which have been used to measure shear attenuation in the mantle using long-period body waveforms. In the time-domain technique, waveform modeling is carried out and the attenuation model that best fits the data is chosen. In the frequency-domain technique, we solve for the attenuation model that best fits the spectra of the seismic waveforms. Though theoretically both these techniques are equivalent, modeling assumptions and measurement biases associated with each technique can give rise to different results. In this study, we compare these two techniques in terms of their accuracy in obtaining mantle shear attenuation. Specifically, we estimate the biases in constraining attenuation from differential SS−S and absolute S waveforms. We carry out these tests using realistic synthetic seismograms and we follow this with an analysis of recorded data to verify the results from the synthetic tests. For the SS−S waveforms, the primary biasing factors are interference with seismic phases due to mantle discontinuities and due to crustal reverberation under the SS bounce point. These factors can affect the t* measurements by up to 0.5 s in the frequency domain and more than 1.5 s in the time domain. For the S waveforms, the frequency-domain measurements are accurate to 0.3 s while the time-domain measurements can vary by more than 2.0 s from the predicted values. These errors are also manifested in the t* measurements made using teleseismically recorded waveforms and lead to comparatively larger noise levels in the time-domain measurements. Based on these results, we propose that in long-period body-wave attenuation studies, frequency-domain techniques should be the method of choice.

Time-domain measurement of the electromagnetic properties of materials

A time-domain measurement and data-reduction technique is presented that can yield the broad-band frequency-dependent values of a sample material's electrical properties (complex permittivity and permeability). The method uses the material's response to the spectral content of a fast rise-time pulse to determine the frequency dependence of the complex relative permittivity (/spl epsi//sub /spl tau//) and permeability (/spl mu//sub r/). The measurement procedure and data-reduction scheme are described, and the derived material values for a sample material are given. The advantages of this method include a potentially lower equipment cost and the avoidance of awkward calibration procedures that are inherent in frequency-domain methods. Though the material examined was nonmagnetic, the procedure is general and rigorous (for low-loss materials, low dispersion over the bandwidth) for the determination of both electrical and magnetic properties.

Time-domain envelope measurement technique with application to wideband power amplifier modeling

This paper presents a new time-domain measurement technique for repetitive microwave signals that is applied to modeling wideband power amplifiers. The measurement technique concept consists of recording the microwave signal after conversion to baseband using a calibrated downconverter, which improves measurement accuracy compared to measurements at the carrier frequency. The modeling section describes how such time-domain measurements can be used to model wideband signal effects in nonlinear power amplifiers. The commonly used memory-less envelope model is limited to use on narrowband signals. A new model is developed which includes a filter before the memory-less nonlinearity to capture the memory effects associated with wideband signals. It is demonstrated that the accuracy of wideband signal simulations can be improved by optimizing the model parameters based on time-domain measurements of wideband signals.

Design and evaluation of a coaxial transmission line fixture to characterize portland cement concrete

Electrical characterization of portland cement concrete (PCC) is necessary for reliable operation of many electromagnetic nondestructive evaluation (NDE) techniques. Examples of such techniques include ground penetration radar (GPR). For that purpose, PCC specimens were cast, and their complex permittivity and magnetic permeability were measured over a wideband of frequencies (1 MHz to 10 GHz) using both time domain and frequency domain measurement techniques. As part of an ongoing research project, three set-ups to measure the dielectric properties of PCC were designed. The measurements are carried out over a frequency range of 0.1 MHz to 10 GHz. The three different set-ups are parallel plate capacitor (0.1 MHz–40 MHz), coaxial transmission line (0.1 GHz–1 GHz), and TEM horn antenna (0.5 GHz– 10 GHz). This paper discusses the development of the coaxial transmission line fixture. It was designed to allow the evaluation of large PCC specimens and obtain an average effect of PCC components. A time domain reflectometry (TDR) setup was used in the design of the fixture and in testing its performance. A calibration scheme was developed and used to calibrate the fixture. Using a two-port S-parameter model, the complex permittivity and magnetic permeability of the PCC specimens were evaluated by frequency domain measurement. Time domain measurement techniques were based on one-port S-parameter model. Evaluation of the set-up using especially molded PCC specimens showed that curing status can be detected at a lower frequency using the imaginary component of the relative permittivity.

Antenna time-domain measurement techniques

The results of an experimental study, in which time-domain pulses are used to measure the far-field characteristics of an antenna, are presented. Pulses with duration and rise time of the order of 50 ps are generated, in order to characterize the complete frequency (1-18 GHz) behavior of an antenna. An X-band standard-gain horn has been used to verify the overall performance of the measurement system. Excellent agreement between the time-domain and the frequency-domain measurements has been observed. This paper describes the antenna time-domain measurement (ATDM) technique, time-domain gating, the error sources, and the advantages and the disadvantages of such a measurement technique.

Measurement, modeling, and simulation of flip-chip CMOS ASIC simultaneous switching noise on a multilayer ceramic BGA

This paper presents the simultaneous switching noise (SSN) measurements, modeling, and simulation of a flip-chip complementary metal-oxide-semiconductor (CMOS) application-specific integrated circuit (ASIC) test chip on a multilayer ceramic ball grid array (CBGA) package. Technology and design features of the chip and package test vehicles are described. Time-domain noise measurement techniques and results are presented in detail. Circuit modeling and simulation methodologies are developed and validated by strong correlation between measurement and simulation results.

Fast time-resolved electrochemical impedance spectroscopy for investigations under nonstationary conditions

A new experimental technique for fast electrochemical impedance spectroscopy (EIS), compatible with both the frequency domain and the time domain measurement techniques, is described. It can be successfully applied for time-resolved EIS measurements under nonstationary conditions. Impedance spectra obtained in situ during the current relaxation in a potential step experiment, using Pt electrode in Fe 2 + Fe 3 + redox electrolyte, are presented as an application example.

Some theoretical foundations of analog signal shape design for measurement and testing

This paper considers the problems of analog signal shape design for the purpose of synthesis of new measurement and testing methods. Some general design principles are formulated: the transposition, the mirror-kernel-reflection, the complementary-matching and the signal-parameter-optimization principles. Theoretical foundations are illustrated by examples of measuring and testing methods based on shape-designed signals. The paper shows that the main effort of measurement may be transferred from the processing of an output signal to the synthesis of an input signal of proper shape. The results come to the conclusion that signal shape manipulation creates a new degree of freedom in the development of the time domain measurement technique.

Wireless information networks

Preface. PART I INTRODUCTION TO WIRELESS NETWORKS. 1 Overview of Wireless Networks. 1.1 Introduction. 1.2 Network Architecture and Design Issues. 1.3 Key Trends in Wireless Networking. 1.4 Outline of the Book. Questions. 2 Evolution of the Wireless Industry. 2.1 Introduction. 2.2 Three Views of the Wireless Industry. 2.3 Three Generations of Cellular Networks. 2.4 Trends in Wireless Technologies. Questions. PART II CHARACTERISTICS OF RADIO PROPAGATION. 3 Characterization of Radio Propagation. 3.1 Introduction. 3.2 Multipath Fading and the Distance-Power Relationship. 3.3 Local Movements and Doppler Shift. 3.4 Multipath for Wideband Signals. 3.5 Classical Uncorrelated Scattering Model. 3.6 Indoor and Urban Radio Propagation Modeling. Questions. Problems. Projects. 4 Modeling and Simulation of Narrowband Signal Characteristics. 4.1 Introduction. 4.2 Modeling Path Loss and Slow Shadow Fading. 4.3 Doppler Spectrum of Fast Envelope Fading. 4.4 Statistical Behavior of Fast Envelope Fading. 4.5 Simulation of Fast Envelope Fading. Questions. Problems. Projects. 5 Measurement of Wideband and UWB Channel Characteristics. 5.1 Introduction. 5.2 Time-Domain Measurement Techniques. 5.3 Frequency-Domain Measurement Techniques. 5.4 Advances in Frequency-Domain Channel Measurement. Questions. Problems. Project. 6 Modeling of Wideband Radio Channel Characteristics. 6.1 Introduction. 6.2 Wideband Time-Domain Statistical Modeling. 6.3 Wideband Frequency-Domain Channel Modeling. 6.4 Comparison Between Statistical Models. 6.5 Ray-Tracing Algorithms. 6.6 Direct Solution of Radio Propagation Equations. 6.7 Comparison of Deterministic and Statistical Modeling. 6.8 Site-Specific Statistical Model. Appendix 6A: GSM-Recommended Multipath Propagation Models. Appendix 6B: Wideband Multipath Propagation Models. Questions. Problems. Projects. PART III MODEM DESIGN. 7 Narrowband Modem Technology. 7.1 Introduction. 7.2 Basic Modulation Techniques. 7.3 Theoretical Limits and Practical Impairments. 7.4 Traditional Modems for Wide-Area Wireless Networks. 7.5 Other Aspects of Modem Implementation. Questions. Problems. Projects. 8 Fading, Diversity, and Coding. 8.1 Introduction. 8.2 Radio Communication on Flat Rayleigh Fading Channels. 8.3 Diversity Combining. 8.4 Error-Control Coding for Wireless Channels. 8.5 Space-Time Coding. 8.6 MIMO and STC. Questions. Problems. Projects. 9 Broadband Modem Technologies. 9.1 Introduction. 9.2 Effects of Frequency-Selective Multipath Fading. 9.3 Discrete Multipath Fading Channel Model. 9.4 Adaptive Discrete Matched Filter. 9.5 Adaptive Equalization. 9.6 Sectored Antennas. 9.7 Multicarrier, OFDM, and Frequency Diversity. 9.8 Comparison of Traditional Broadband Modems. 9.9 MIMO in Frequency-Selective Fading. Appendix 9A: Analysis of the Equalizers. Questions. Problems. Projects. 10 Spread-Spectrum and CDMA Technology. 10.1 Introduction. 10.2 Principles of Frequency-Hopping Spread Spectrum. 10.3 Principles of Direct-Sequence Spread Spectrum. 10.4 Interference in Spread-Spectrum Systems. 10.5 Performance of CDMA Systems. Questions. Problems. PART IV SYSTEMS ASPECTS. 11 Topology, Medium Access, and Performance. 11.1 Introduction. 11.2 Topologies for Local Networks. 11.3 Cellular Topology for Wide-Area Networks. 11.4 Centrally Controlled Assigned Access Methods. 11.5 Distributed Contention-Based Access Control. Questions. Problems. Project. 12 Ultrawideband Communications. 12.1 Introduction. 12.2 UWB Channel Characteristics. 12.3 Impulse Radio and Time-Hopping Access. 12.4 Direct-Sequence UWB. 12.5 Multiband OFDM. Questions. Problems. 13 RF Location Sensing. 13.1 Introduction. 13.2 RF Location-Sensing Techniques. 13.3 Modeling The Behavior of RF Sensors. 13.4 Wireless Positioning Algorithms. Questions. Problems. 14 Wireless Optical Networks. 14.1 Introduction. 14.2 Implementation. 14.3 Eye Safety. 14.4 IR Channel Characterization and Data-Rate Limitations. 14.5 Modulation Techniques for Optical Communications. 14.6 Multiple Access and Data Rate. Questions. 15 Systems and Standards. 15.1 Introduction. 15.2 GSM, GPRS, and EDGE. 15.3 CDMA and HDR. 15.4 Other Historical Systems. 15.5 Wireless LANs. 15.6 Speech Coding in Wireless Systems. Questions. References. Index. About the Authors.

Optoelectronic transient characterization of ultrafast devices

Recent advances in state-of-the-art optoelectronic techniques applied to areas pertinent to transistor small-signal and large-signal characterization are discussed. The aspects of optoelectronic techniques for electrical signal measurement, generation, and transmission are studied. On the basis of these results, a large-signal digital-switching transistor characterization methodology is developed. This methodology is used to estimate the parameters of a high-electron-mobility transistor and to obtain the large-signal characteristics of this device on a picosecond time scale. The measurements are compared to a SPICE-based time-domain model. The time-domain measurement technique is extended to obtain two-port frequency-domain characteristics of another, similar transistor with a 100-GHz bandwidth. These results compare favorably to conventional HP8510 network analyzer measurements over a common frequency span of 40 GHz. >

Optoelectronic measurements of picosecond electrical pulse propagation in coplanar waveguide transmission lines

Observations are presented concerning the effects of coplanar waveguide transmission lines on the propagation of picosecond electrical pulses using an optoelectronic time-domain measurement technique. Effects of various test structure design factors such as substrate thickness, thickness of transmission line metallization, discontinuity spacing, ground plane width, pulser/sampler line length, and pulser/sampler geometry on picosecond electrical pulse propagation in microwave/millimeter wave coplanar waveguide transmission lines are discussed, and schemes for minimizing the adverse effects of each of the above factors are provided. >

Density dependence of noise in thin metallic longitudinal media

The dependence of noise in thin metallic longitudinal disks on the transition density is investigated. The medium noise is modeled in the time domain by assuming that the recorded transitions are subject to random variations in width as well as in position. A time domain measurement technique is developed to estimate the second order statistics of transition width and transition position as a function of recording density. The results indicate that the noise due to the transition width variations predominates over the noise resulting from the position jitter of the written transitions at high densities where the transition spacing approaches the transition width.