Showing papers in "IEEE Transactions on Instrumentation and Measurement in 1988"
TL;DR: The concept of orthogonal decomposition of the current in a nonlinear single-phase circuit, with a sinusoidal voltage source, into active, scattered, reactive, and generated components is extended to three-phase asymmetrical circuits in this article.
Abstract: The concept of orthogonal decomposition of the current in a nonlinear single-phase circuit, with a sinusoidal voltage source, into active, scattered, reactive, and generated components is extended to three-phase asymmetrical circuits. It is shown that the source current in such a circuit can be decomposed into five orthogonal components that depend on distinctively different phenomena. Four of them have the same meaning as in the single-phase circuit, with only a change in their mathematical characterization. An additional orthogonal component appears in the source current, because of the load asymmetry. >
332 citations
TL;DR: Waveform digitizers are analyzed which utilize interleaving/multiplexing and random equivalent time-sampling techniques and the monolithic A/D converter technology to extend their capabilities to analyze the harmonic distortion introduced in high-speed waveformDigitizers due to time-base errors.
Abstract: A digital spectral representation of a nonuniformly sampled signal is derived, and a spectrum analysis of a nonuniformly sampled sinusoid is presented. It is found that the spectrum of a nonuniformly sampled sinusoid comprises uniformly spaced line spectra; in addition, the signal-to-noise ratio is obtained in closed form. The theories are then applied to analyze the harmonic distortion introduced in high-speed waveform digitizers due to time-base errors. Specifically, waveform digitizers are analyzed which utilize interleaving/multiplexing and random equivalent time-sampling techniques and the monolithic A/D converter technology to extend their capabilities. Theoretical results are confirmed by experimental results with a real waveform digitizer. >
304 citations
TL;DR: In this paper, an algorithm is presented to minimize the peaks in the time domain of bandlimited Fourier signals, which has the ability to compress signals effectively without disturbing their spectral magnitudes.
Abstract: An algorithm is presented to minimize the peaks in the time domain of bandlimited Fourier signals. This method has the ability to compress signals effectively without disturbing their spectral magnitudes. A computationally efficient algorithm is presented that leads to strongly compressed signals (crestfactors of 1.41 compared to 1.67). The method is applicable not only to flat spectrum magnitudes but to any frequency domain energetic distribution. >
183 citations
TL;DR: The properties of ten different excitation signals are studied to analyze their suitability as excitation signal for fast Fourier transform (FFT)-based signal and network analyzers and the flexibility to create a customized amplitude spectrum is investigated.
Abstract: The properties of ten different excitation signals are studied to analyze their suitability as excitation signals for fast Fourier transform (FFT)-based signal and network analyzers. Their influence on the measurement time, accuracy, and sensitivity to nonlinear distortions is described. The flexibility to create a customized amplitude spectrum is investigated. With this information it becomes possible to select the best excitation signal for many applications. >
167 citations
TL;DR: The implications of strong signal compression for the signal-to-noise ratio lead to the formulation of a two-step optimal experimental setup for system identification and parameter estimation of linear systems.
Abstract: An overview is given of existing analytical and numerical methods for the comparison of the peaks of discrete, finite sum of sines. A novel method that compresses the signals optimally or almost optimally is presented. The algorithm is extended to the simultaneous compression of the input and output signals of a linear system. The implications of strong signal compression for the signal-to-noise ratio lead to the formulation of a two-step optimal experimental setup for system identification and parameter estimation of linear systems. >
104 citations
TL;DR: In this article, a stray-immune capacitance measuring instrument based on the charge transfer principle is described, which has a programmable measurement frequency up to several megahertz and is inexpensive and suitable for integration onto a single chip.
Abstract: A stray-immune capacitance measuring instrument based on the charge transfer principle is described. It has a programmable measurement frequency up to several megahertz and is inexpensive and suitable for integration onto a single chip. The effects of stray capacitances, including those of the switching components, have been eliminated by using a special switching arrangement, resulting in a baseline drift of 0.02 pF (at 1-MHz measurement frequency) over a 12-h period. >
91 citations
TL;DR: In this paper, the electronic configuration of a versatile computer-controlled measurement system that can be used to obtain AC and DC conductivity, Hall effect, and magnetoresistance data over the temperature range of 1.5 to 350 K is described.
Abstract: A description is given of the electronic configuration of a versatile computer-controlled measurement system that can be used to obtain AC and DC conductivity, Hall effect, and magnetoresistance data over the temperature range of 1.5 to 350 K. The system can process one to eight samples simultaneously in the resistance range from 0 to 10/sup 12/ Omega . >
83 citations
TL;DR: In this article, the structure of the harmonic components present in a digitally synthesized sine wave is analyzed using a table look-up method, and the frequencies, amplitudes, and phrases of all the spurious harmonic components are derived in closed form.
Abstract: For Part I see ibid., vol.37, no.2, June 1988. The author presents theories and applications of a digital spectrum analysis technique for a class of nonuniformly sampled signals. The structure of the harmonic components present in a digitally synthesized sine wave is analyzed using a table look-up method. The digital table look-up method offers several desirable features, such as high-frequency stability and precision control of both the frequency and the phase of the generated sine wave. However, undesirable spurious harmonic components are generated when one tries to tune to different frequencies by manipulating the memory-addressing mechanism rather than loading a new waveform sample into the waveform memory, which is generally time-consuming and sometimes infeasible. The frequencies, amplitudes, and phrases of all the spurious harmonic components are derived in closed form. >
81 citations
TL;DR: In this article, a rectangular section of the leaf is placed in the transverse plane in rectangular waveguide, and the magnitude and phase of the reflection coefficient are measured over the desired frequency band using a vector network analyzer.
Abstract: A practical technique for measuring the dielectric constant of vegetation leaves and similarly thin materials is presented. A rectangular section of the leaf is placed in the transverse plane in rectangular waveguide, and the magnitude and phase of the reflection coefficient are measured over the desired frequency band using a vector network analyzer. By treating the leaf as an infinitesimally thin resistive sheet, an explicit expression for its dielectric constant is obtained in terms of the reflection coefficient. Because of the thin-sheet approximation, however, this approach is valid only at frequencies below 1.5 GHz. To extend the technique to higher frequencies, higher-order approximations are derived and their accuracies are compared to the exact dielectric-slab solution. For a material whose thickness is 0.5 mm or less, the proposed technique was found to provide accurate values of its dielectric constant up to frequencies of 12 GHz or higher. >
79 citations
TL;DR: In this article, a method for estimating the parameters of linear systems and nonlinear systems is presented, where the linear systems are modeled by their transfer function, while the nonlinear system are described by a Volterra series.
Abstract: A method is presented for estimating the parameters of linear systems and nonlinear systems. The linear systems are modeled by their transfer function, while the nonlinear systems are described by a Volterra series. The estimator belongs to the class of maximum-likelihood estimators. During the estimation process, the Cramer-Rao lower bound on the covariance matrix of the estimates is derived. >
67 citations
TL;DR: In this article, a time-domain definition of power, using correlation techniques, is proposed to establish a method for fictitious power measurement and derive fictitious power compensation criteria in power systems with nonsinusoidal currents and voltages.
Abstract: The definitions of power are reviewed to establish a method for fictitious power measurement and to derive fictitious power compensation criteria in power systems with nonsinusoidal currents and voltages. A time-domain definition of power, using correlation techniques, is proposed. This leads to the proposal of a network parameter. A combination of digital and analog signal-processing techniques is proposed in the measurement and analysis of the components of power. The results of simulated and practical power measurements, the latter on an experimental electronic pulsewidth-modulated power converter, used for fictitious power compensation are given. >
TL;DR: In this paper, a technique for linearizing type-II transducer characteristic using a log-converter and a FET is presented, and its performance is compared with that of a simple single-stroke digital technique.
Abstract: Most of the practical transducers fall into two categories regarding their input-output characteristics: type I, with a characteristic that is exponentially rising, and type II, with a characteristic that is exponentially decaying. While type I is easily linearized using a logarithmic converter, type II needs additional inversion means for the purpose of linearization. A technique for linearizing type-II transducer characteristic using a log-converter and a FET is presented, and its performance is compared with that of a simple single-stroke digital technique. Examples and experimental results are presented and discussed. >
TL;DR: In this paper, a fiber-optic-conveyed, laser-induced fluorescence of a thermographic phosphor was used to measure the surface temperature of the rotor in an operating permanent magnet motor.
Abstract: The fiber-optic-conveyed, laser-induced fluorescence of a thermographic phosphor was used to measure the surface temperature of the rotor in an operating permanent-magnet motor. The technique uses a pulsed laser to interrogate a surface-bonded film of europium-doped lanthanum oxysulfide for the purpose of determining its temperature-dependent, exponential-decay lifetime. By using digital-delay circuitry to control the measurement systems timing, the authors achieved spatial resolutions of better than 2 mm at speeds of up to 700 rotations/s. The precision of the temperature measurements was 0.3 degrees C. The details of the measurement system are presented and discussed. >
TL;DR: A robot-arm positioning control that makes use of a microprocessor-based ultrasonic system and of a novel time-of-flight measurement technique and can be used in robotic applications in industrial environments, such as for orientation control or object grasping.
Abstract: A robot-arm positioning control is described. It makes use of a microprocessor-based ultrasonic system and of a novel time-of-flight measurement technique. The experimental system consists of a three aligned ultrasonic transducers mounted on a rod. Two transducers work as receivers, while the third works both as a transmitter and a receiver. The system achieves a positioning accuracy of +or-0.1 degrees in the field of +or-10 degrees of misalignment for a distance ranging from a few centimeters up to 200 mm. For a higher distance range up to 300 mm, the position accuracy is +or-0.4 degrees . The system also performs distance measurement, using the same group of transducers. The system can be used in robotic applications in industrial environments, such as for orientation control or object grasping. >
TL;DR: A simple method for linearizing analog electrical signals and transducer outputs as they are being converted to a digital format based on the ratiometric property inherent to the analog-to-digital converter is described.
Abstract: A simple method for linearizing analog electrical signals and transducer outputs as they are being converted to a digital format is described It is based on the ratiometric property inherent to the analog-to-digital converter The method gives satisfactory results in many cases, and the resulting circuits are simple and easily adjusted It can be applied to correct the output of a digital readout meter and can provide a convenient alternative to digital linearization of signals >
TL;DR: In this article, a ring cavity is proposed to minimize distributed cavity phase variations at the position of the atomic beam, providing only that the two sides of the ring and the T-junction feeding the ring are symmetric.
Abstract: In the design of cesium beam frequency standards, the presence of distributed cavity phase shifts (associated with residual running waves) in the microwave cavity, due to the small losses in the cavity walls, can become a significant source of error. To minimize such errors in future standards, it has been proposed that the long Ramsey excitation structure be terminated with ring-shaped cavities in place of the conventional shorted waveguide. The ring cavity will minimize distributed cavity phase variations at the position of the atomic beam, provides only that the two sides of the ring and the T-junction feeding the ring are symmetric. A model is developed to investigate the validity of this concept in the presence of the small asymmetries that inevitably accompany the fabrication of such a cavity. The model, partially verified by laboratory tests, predicts that normal tolerances will allow the frequency shifts due to distributed cavity phase variations to be held at the 10/sup -15/ level for a beam tube with a Q of 10/sup 8/. >
TL;DR: The implementation of two recently introduced variable digital filter schemes using a TMS320-series digital signal processor is presented and the measured frequency responses compare well with the theory.
Abstract: The implementation of two recently introduced variable digital filter schemes using a TMS320-series digital signal processor is presented. One is a method for updating the coefficients of an FIR (finite-impulse response) filter in a simple manner such that the cutoff frequencies can be controlled through a single parameter. The other is a method for tuning the cutoff frequency of an IIR (infinite-impulse response) filter with one parameter using a series expansion of the low-pass-low-pass frequency transformation. The measured frequency responses compare well with the theory. >
TL;DR: The problem of error reduction is studied, both synchronous and asynchronous samplings are considered, and a method for describing the error in the frequency domain is proposed.
Abstract: The problem of error reduction is studied. Both synchronous and asynchronous samplings are considered, and a method is proposed for describing the error in the frequency domain. Its advantages are that the input signal does not need to be restricted to the band-limited hypothesis, and that a comparison of the various processing methods can be conveniently made. A compensation method for improving accuracy is discussed. >
TL;DR: In this paper, the Barnes-Jarvis 1/f noise generator with exponents gamma between -2 and 2 is derived and a simple and useful design method for a flicker-like noise generator is reported.
Abstract: The authors discuss the design of a noise sequence generator that provides a stationary process that follows a 1/f/sup gamma / law over a limited frequency band. The kind of noise is generated by passing a white-noise sequence in a digital filter characterized by a frequency-response-squared module proportional to 1/f/sup gamma /. The design of the digital filter is performed in a straightforward manner by applying the matched z-transform to the transfer function of a proper analog filter. The digitalization error is also discussed, and a simple and useful design method for a flicker-like noise generator with exponents gamma between -2 and 2 is reported. It is shown that the Barnes-Jarvis 1/f noise generator can easily be derived as a particular case with gamma =1. >
TL;DR: In this article, an exact non-uniform sampling scheme based on Cauchy's residue theorem was proposed for the processing of astronomical data and the error correction of high-frequency network analyzers.
Abstract: An exact nonuniform sampling scheme is proposed based on Cauchy's residue theorem. The noise behavior is studied and the consequences for possible applications given. An inherently nonuniform sampling instrument is built and used in experiments. The results of the application of the formulas for the processing of astronomical data and the error correction of high-frequency network analyzers are given. >
TL;DR: In this article, the statistical properties of the geometric mean of power (amplitude) spectra resulting from a discrete Fourier transform (DFT) are compared with those of arithmetic (RMS) averaging.
Abstract: The statistical properties of the geometric mean of power (amplitude) spectra resulting from a discrete Fourier transform (DFT) are compared with those of arithmetic (RMS) averaging. The statistical properties are verified by means of frequency-domain and time-domain simulations. It is shown that the asymptotic bias of the geometric mean is a function of the fourth-order moments of the measurement noise. >
TL;DR: In this article, an optically pumped Cs frequency standard aiming at a primary frequency standard was developed, and a Ramsey resonance spectrum was observed using this laboratory-type standard, and it has been shown that a laser power of about 1 mW is almost sufficient for two-frequency optical pumping.
Abstract: Describes development of an optically pumped Cs frequency standard aiming at a primary frequency standard. Using this laboratory-type standard, a Ramsey resonance spectrum was observed. It has been shown that a laser power of about 1 mW is almost sufficient for two-frequency optical pumping. It has also been shown that the C-field strength can be measured using Zeeman coils by establishing a population difference among the Zeeman sublevel with sigma /sup +/ polarized laser light. >
TL;DR: In this article, an operational-amplifier-based sine-wave oscillator applied in capacitance measurement was simulated using the SPICE program to study the behavior of the circuit under nonideal conditions, and to estimate the errors introduced in the measured capacitance and the frequency of oscillation.
Abstract: Errors introduced in an operational-amplifier-based sine-wave oscillator applied in capacitance measurement are considered. The errors due to the nonideal characteristics of the operational amplifier are addressed. The oscillator circuit was simulated using the SPICE program, and gives the opportunity to study the behavior of the circuit under nonideal conditions, and to estimate the errors introduced in the measured capacitance and the frequency of oscillation. It is shown that major sources of error are the gain-bandwidth product and the output resistance of the operational amplifier. Compensation techniques to reduce errors related to the gain-bandwidth product are presented. Experimental results confirming the error reduction are included. >
TL;DR: In this article, two open-ended coaxial sensors for in vivo measurements of the dielectric properties of biological tissues at low radio frequencies are described, and the high fringing-field capacitance of these sensors allows accurate measurements of high-water-content tissues at frequencies as low as 10 kHz.
Abstract: Two open-ended coaxial sensors for in vivo measurements of the dielectric properties of biological tissues at low radio frequencies are described. The high fringing-field capacitance of these sensors allows accurate measurements of high-water-content tissues at frequencies as low as 10 kHz. Each sensor is represented by two capacitances, which are calculated using the method of moments. Theoretical and experimental results for experimental sensors terminating a standard 14-mm coaxial line with a GR900 connector are presented. >
TL;DR: In this paper, a temperature measuring circuit using a thermistor in a specially designed pulse generator is used to obtain a highly linear relation between absolute temperature and frequency, where the use of a general-purpose operational amplifier and two switching transistors in the design of the pulse generator provides a temperature scale that is linear over a wide range of values on a high degree of sensitivity.
Abstract: A modification of an existing technique for thermistor linearization is presented. A temperature-measuring circuit using a thermistor in a specially designed pulse generator is used to obtain a highly linear relation between absolute temperature and frequency. The use of a general-purpose operational amplifier and two switching transistors in the design of the pulse generator provides a temperature scale that is linear over a wide range of values on a high degree of sensitivity. The result shows that an extremely high degree of linearity is achieved by this method. >
TL;DR: In this paper, radiofrequency (RF) and microwave heating techniques are reviewed for interstitial hyperthermia, ferromagnetic seed implant, local external hyperthermation, regional hyperthermic, and phased array hyper-thermia.
Abstract: Radio-frequency (RF) and microwave heating techniques are reviewed. Clinical applications touched on include interstitial hyperthermia, ferromagnetic seed implants, local external hyperthermia, regional hyperthermia, and phased-array hyperthermia. Examples of heating patterns of various applicators are shown to illustrate the complex energy deposition of RF and microwave energy. >
TL;DR: A comparison of three proposed six-port designs shows that the Engens four-port design presents the best performance for a given power measurement accuracy, while a maximum dynamic range of 60 dB seems to be a limit for six- port reflectometers using a good-quality power detector.
Abstract: A detailed analysis of the accuracy in complex-reflection coefficient measurement by the six-port technique is discussed. The expression of the relative error in amplitude measurement of the complex reflection due to power-reading errors are derived in worst-case situation using both the basic six-port and sensitivity analysis theories. The precision of measurement of any point in the Smith chart is obtained by reference to lines of constant errors (amplitude and phase) drawn on the Smith chart for various proposed six-port correlators (junctions). A comparison of three proposed six-port designs shows that the Engens six-port design presents the best performance for a given power measurement accuracy. A maximum dynamic range of 60 dB seems to be a limit for six-port reflectometers using a good-quality power detector ( alpha =0.1%). >
TL;DR: In this paper, the microwave drying of 13X zeolite is experimentally studied by continuously measuring the permittivity of a sample material during given microwave drying cycles, showing that the adsorbed water molecules are much less mobile than the free water molecules.
Abstract: The microwave drying of 13X zeolite is experimentally studied by continuously measuring the permittivity of a sample zeolite material during given microwave drying cycles. The results are interpreted in light of the dielectric theory of heterogeneous mixtures, making it possible to distinguish the water vapor in circulation within the zeolite structure from the water absorbed on the solid material. The results agree with previous data, showing that the adsorbed water molecules are much less mobile than the free water molecules. Time constants involved with the desorption and transport processes of water are obtained under microwave power heating conditions. >
TL;DR: In this paper, a visible LED-pumped, photoluminescent optical-fiber sensor was used to measure temperature using the crystal alexandrite, which is accurate to + or 1 degrees C over a range 20-150 degrees C, with a response time of 1 s.
Abstract: The development and calibration of a visible LED-pumped, photoluminescent optical-fiber sensor to measure temperature using the crystal alexandrite is reported. Utilizing the dependence of the fluorescent decay time on temperature, this instrument is accurate to +or-1 degrees C over a range 20-150 degrees C, with a response time of 1 s. >
TL;DR: In this paper, the tracking properties of feedback and using an integrator for a plant, the resulting error signal will approximate the derivative of the input, and the system is stable for positive values of the gain.
Abstract: The feedback properties of operational amplifiers are used in the construction of the differentiator. The basic concept, however is device-independent. Utilizing the tracking properties of feedback and using an integrator for a plant, the resulting error signal will approximate the derivative of the input. The system is stable for positive values of the gain. The signal-to-noise ratio (S/N) is controllable and is inversely proportional to the cubic power of the unity-gain bandwidth. The differentiator can have a higher frequency range of operation than is possible with other methods of design. >