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Instrumentation and Measurement, IEEE Transactions on

Issue 5 • Date Oct 1989

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Displaying Results 1 - 18 of 18
  • Apparent diurnal effects in the global positioning system

    Publication Year: 1989 , Page(s): 991 - 997
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    Significant evidence is found indicating a systematic diurnal variation in the ephemeris and the propagation terms as transmitted from GPS (global positioning system) satellites. It is noted that the proper way to sort these out would be a two-frequency receiver. The presence of a similar diurnal variation even with a two-frequency P-code receiver is also indicated. The significance of using the P-code is that the chip rate of the pseudonoise code is 10 times higher, thus dividing by 10 the effect of multipath variations. It is also shown that a GPS clock can be characterized for periods of less than one day by removing the diurnal variation. It is assumed that the diurnal variation is a systematic error, not a feature of the clock. It is removed by taking only relevant fast Fourier transform values, inversely transforming them, and subtracting them in the time domain. The resultant (GPS-Global UTC(NIST)) data are presented with the Allan variance View full abstract»

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  • Frequency stability characterization from the filtered signal of a precision oscillator in the presence of additive noise

    Publication Year: 1989 , Page(s): 967 - 973
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    The authors present a generalized theory to express the frequency stability characterization of a precision oscillator when its signal, perturbed by additive noise, is filtered. The general expressions for the power spectral density of the amplitude and phase fluctuations of the filtered signal are calculated as functions of the oscillator amplitude and phase fluctuations, the additive noise, and the filter characteristics. The results obtained for the phase fluctuations of the filtered signal are used to characterize the frequency stability of the oscillator. The contribution of white additive noise to the generalized Allan variance is expressed in terms of a parameter, the equivalent bandwidth. The contributions of other types of noise are also calculated. For the first-order low-pass filter, the contributions of all types of additive, amplitude, phase, and frequency noise are given. Experimental results show excellent agreement with the theoretical predictions View full abstract»

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  • The generation of laser difference frequencies using the scanning tunneling microscope

    Publication Year: 1989 , Page(s): 1019 - 1021
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    Infrared laser radiation and radio frequency signals were coupled into the tunneling junction of a scanning tunneling microscope (STM), and the difference frequencies and their harmonics generated in the nonlinear junction were studied as a function of the tunneling parameters. Difference frequencies up to 9 GHz were observed. The importance of the results for the difference frequency mixing in metal-insulator-metal (MIM) diodes and for the STM is discussed. The experiments demonstrate that the tunneling junction of the STM can be used to generate difference frequencies of injected electromagnetic radiation in a similar way and with a similar efficiency to those of the MIM diodes. Due to the precise controllability of the tunneling parameters in the STM the frequency mixing process in its tunneling junction is highly reproducible View full abstract»

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  • An improved straddling method with triaxial guards for the calibration of inductive voltage dividers at 1592 Hz

    Publication Year: 1989 , Page(s): 974 - 978
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    Calibrated inductive voltage dividers (IVDs) with the smallest possible uncertainties are required for the determination, maintenance, and dissemination of the ohm and the farad. An improved straddling method is described which uses triaxial guards to decrease systematic errors due to screen currents. The relative uncertainty with which IVD voltage ratios can be determined is calculated to be 1×10-9 (1 σ) at a frequency of 1592 Hz View full abstract»

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  • MSCAN-a microwave field scanning system

    Publication Year: 1989 , Page(s): 948 - 953
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    A description is given of MSCAN (Microwave SCANning), a computer-controlled system designed to measure electric and magnetic fields in a liquid ambient medium. A two-axis positioning system moves a probe antenna, and the probe's output signal is measured by a Hewlett-Packard 8410B automatic network analyzer. The fields are normalized to a selected reference point. An analysis of the quantization error in the HP8410B has been made in order to estimate a bound on the accuracy of the system. MSCAN has been used to measure the normalized electric field radiated by an open-ended dielectric-filled waveguide antenna in a water ambient medium at approximately 3 GHz. Normalized scattered fields, found from the difference between total and incident fields, were measured from a dielectric cylinder. However, the results were poor when fields were weak compared to the noise floor of the HP8410B. The problems involved in performing such measurements are discussed View full abstract»

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  • Eliminating the ambiguity in nonperturbation microwave measurements of permittivity

    Publication Year: 1989 , Page(s): 1010 - 1012
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    The authors propose a method for eliminating the ambiguity in the dielectric constant which appears in many measurement techniques at microwave frequencies. They describe the procedure in a general way and apply it to the TE cavity technique to measure the permittivity of liquids and to the short-circuited line technique. The viability of the procedure and its simplicity compared with commonly used methods are shown. Complicated calculations involved in the comparison of two sets of solutions of two transcendental equations are avoided, and the correct value of the dielectric constant is obtained from the root of a simple algebraic equation View full abstract»

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  • Determining complex permittivity by measuring the scattered waveform from a dielectric circular cylinder

    Publication Year: 1989 , Page(s): 1012 - 1014
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    The author describes a method of measuring complex permittivity by making use of a two-dimensional scattered wave from a dielectric circular cylinder. The far-field pattern in the plane perpendicular to the cylinder axis is examined when the dielectric is illuminated by a line-source antenna that is parallel to the axis of the cylinder. An automated measurement of the complex permittivity is compared with a computed result based on theory. When the loss factor is high, this method becomes competitive with other techniques. The complex permittivity can be determined by this method over a wide range except for the case where the dielectric loss is very small View full abstract»

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  • High precision phase measurement using adaptive sampling

    Publication Year: 1989 , Page(s): 954 - 960
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The conventional phase measurement techniques introduce error in the phase when the input signals are distorted by harmonics. A novel technique, known as adaptive sampling, for high-precision phase measurement is introduced. A digital signal-processing approach is used in this technique. The maximum sampling rate required for this technique is h+2 samples/cycle of the input signals, i.e. (h+2) f sampless, where h, is the highest harmonic present in the signals and f is the fundamental frequency of the signals. This sampling rate is way below the Nyquist sampling rate (more than 2hf samples/s) when h is a large number. In the adaptive sampling technique the sampling rate is started from three samples/cycle and then is gradually increased until the phase is correctly measured. This phase measurement technique has been verified using synthesized signals View full abstract»

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  • Integrated digital control and filtering for an electrodynamically compensated weighing cell

    Publication Year: 1989 , Page(s): 998 - 1003
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (456 KB)  

    An integrated digital control and filtering system (IDCFS) has been designed for a high-resolution electrodynamically compensated weighing cell. This system provides faster response time and higher robustness with respect to disturbances than current analog equipment. The basic concept of the IDCFS and major problems of its hardware and software design are discussed. In addition, an intelligent multifilter scheme is presented for high-precision measurement applications. Experimental results obtained for a prototype weighing cell equipped with an IDCFS are presented View full abstract»

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  • Estimation of Fourier coefficients

    Publication Year: 1989 , Page(s): 1005 - 1007
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    It is shown that the maximum-likelihood estimation or robust estimation of the Fourier coefficients may be preferable to Fourier transformation if the noise contains outliers or is otherwise not normally distributed. The reason is that, in that case, these estimators produce Fourier coefficient estimates and, therefore, system parameter estimates having a smaller variance View full abstract»

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  • Reconsidering natural binary encoding for absolute position measurement application

    Publication Year: 1989 , Page(s): 1014 - 1016
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    It is well known that absolute encoders using natural binary codes are prone to reading errors because more bits can change between adjacent scale sectors. Some solutions, such as V-scan, were proposed to solve this problem, but they required too many additional reading heads and decoding circuits to be competitive with the reduced complexity obtained when using the Gray code. The author describes a novel natural binary absolute encoder using an original scanning technique that solves more efficiently the problem of the inherent code reading errors. It is shown that for the same nominal resolution, the complexity of the encoder is similar to, if not better than, that of the Gray-type encoder View full abstract»

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  • Use of residue arithmetic for resolving ambiguity in phase measurements

    Publication Year: 1989 , Page(s): 1007 - 1009
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (256 KB)  

    A novel method for resolution of phase ambiguities by the use of the residue number system is presented. The contribution of noise is reduced compared to making phase measurements with little frequency difference. In addition, an error correction can be introduced to increase the robustness against noise. Computer simulations demonstrated the good performance of the method; the implementation is easy and straightforward View full abstract»

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  • Application of Fourier analysis to phase-Doppler-signals generated by rough metal particles

    Publication Year: 1989 , Page(s): 984 - 990
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    With the phase-Doppler-difference method the diameter and the velocity of spherical particles can be determined by measuring the frequency and the phase difference of burst signals detected by two or more photodetectors. A Fourier analysis method is described that extracts frequency and phase information from the Doppler signals. The system is designed around a TMS320C25 signal-processor board fitted into an AT computer. The performance of the frequency and phase estimator is examined. The method is particularly useful with noisy burst signals, such as those that occur in investigating a metal spraying process View full abstract»

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  • Ambiguity groups and testability

    Publication Year: 1989 , Page(s): 941 - 947
    Cited by:  Papers (29)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    An efficient method has been developed for determining component ambiguity groups which arise in analog circuit testing. The method makes use of the sensitivity model of the circuit. The ambiguity groupings are shown to depend on the test points selected and the measurement accuracy and are therefore a useful tool for determining where to add or delete test points. The concept of ambiguity groups can be used to refine the testability measure of a circuit. An example that demonstrates the effects of ambiguity groups on parameter estimation and performance prediction is presented View full abstract»

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  • Ultra-quiet high voltage source

    Publication Year: 1989 , Page(s): 1004 - 1005
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1512 KB)  

    A very simple, very inexpensive circuit is described for conditioning a high-voltage source to reduce supply ripple and noise from several volts p-p to microvolts, achieving a wideband supply noise level of better than -140 dB. The noise suppressor achieves its performance by taking advantage of the special nature of the problem-a few volts of ripple riding a large constant background. The device can be retrofitted to an existing supply with an immediate improvement in performance View full abstract»

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  • A Wigner spectral analyzer for nonstationary signals

    Publication Year: 1989 , Page(s): 961 - 966
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    The authors present computational algorithms for the design of an innovative spectral analyzer using the Wigner distribution. This spectral analyzer uses advanced digital signal-processing chips with associated hardware and software. Algorithms for the kernel generation, kernel transformation, and discrete Hilbert transform are discussed. Design strategies are focused on achieving high time-frequency resolution, precision, flexibility, and computational efficiency. Experiments show that spectral analysis using the Wigner distribution yields significantly improved results for nonstationary signals View full abstract»

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  • A current transfer method and its application to calibrating a current comparator

    Publication Year: 1989 , Page(s): 979 - 983
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    Current transfer by switching a comparison winding from a series to a parallel connection allows the error of an n:1 ratio comparator to be determined by self-calibration at a 1:1 ratio. The magnetic errors are shown to be the same for either comparison winding connection. The technique is limited to frequencies at which the magnetic error considerably exceeds the admittance error, i.e. typically up to several hundred hertz. The frequency range for which the method can be applied depends on the distribution of admittances to ground as well as the interwinding and shunt admittances, which cause the admittance error for a series section connection to be different from its value for a parallel section connection. The error characteristic also depends on resonances in the inductance circuits appearing in the comparator, on capacitances to ground, and on the interwinding and shunt capacitances View full abstract»

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  • A real-time adaptive lattice predictor using a digital signal processor chip

    Publication Year: 1989 , Page(s): 1016 - 1019
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    A real-time adaptive lattice predictor was implemented using a digital signal processing chip. The implementation comprises input-output units, a central processing and control unit, and supporting software. The performance of the hardware was verified by comparing an input signal and the one-step prediction signal calculated by the predictor. The maximum operating frequency for the four-stage lattice structure was 13.5 kHz View full abstract»

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Aims & Scope

Papers are sought that address innovative solutions to the development and use of electrical and electronic instruments and equipment to measure, monitor and/or record physical phenomena for the purpose of advancing measurement science, methods, functionality and applications.

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Editor-in-Chief
Prof. Alessandro Ferrero
Dipartimento di Elettrotecnica
Piazza Leonardo da Vinci 32
Politecnico di Milano
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alessandro.ferrero@polimi.it
Phone: 39-02-2399-3751
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