Showing papers in "IEEE Transactions on Instrumentation and Measurement in 1982"

Monoion oscillator as potential ultimate laser frequency standard

Abstract: An individual atomic ion localized in the center of a small Paul RF quadrupole trap has potential as an ultimate laser frequency standard because the ion may be brought to `a state of complete rest in free space' by sideband cooling As a consequence, all Doppler shifts vanish, `Free Space' is approximated in so far as the electric trapping field vanishes in the center of the trap and there is no Stark effect Neither need there be a Zeeman effect as magnetic fields may be controlled down to the microgauss range There is also no transit time broadening Minute laser powers provided by harmonic generators suffice for saturation of optical transitions as strongly focused beams may be used A million-fold atomic amplification of the single-ion fluorescence from a metastable level may bring resolutions of 1 part in 1018 within reach

Equivalent circuit of an open-ended coaxial line in a lossy dielectric

Abstract: An open-ended coaxial line was used as a sensor in measurement of the permittivity of lossy dielectrics at radio and microwave frequencies. A simplified equivalent circuit related the permittivity to the measured input reflected coefficient. A more complete equivalent circuit is proposed and errors in the permittivity measurements resulting from the simplification are analyzed.

Continuous and discrete Fourier transforms of steplike waveforms

Abstract: A steplike waveform which has attained its final value is converted into a duration-limited one which preserves the spectrum of the original waveform and is suitable for discrete Fourier transform (DFT) computations. The method, which is based upon the response of a time-invariant linear system excited by a rectangular pulse of suitable duration, is first applied to continuous waveforms and then to discrete (sampled) waveforms. The difference (errors) between the spectra of a continuous waveform and a discrete representation of it are reviewed.

Modeling of the HP-1430A feedthrough wide-band (28-ps) sampling head

Abstract: The theory and construction of the HP-1430A feed-through sampling head are reviewed, and a model for the sampling head is developed from dimensional and electrical measurements in conjunction with electromagnetic, electronic, and network theory. The model was used to predict the sampling-head step response needed for the deconvolution of true input waveforms. The dependence of the sampling-head step response on the sampling diode bias is investigated. Calculations based on the model predict step response transition durations of 27.5 to 30.5 ps for diode reverse bias values of -1.76 to -1.63 V.

A phase-stabilized local-oscillator system for a synthesis radio telescope

Abstract: A system is described which delivers signals of precisely controllable frequency and phase to remote points. The system is used to provide local-oscillator signals at widely separated antennas in a synthesis radio telescope operating at 1.4 GHz. Phase accuracy is 1.1° rms. The system is a closed-loop phase-control circuit employing phase-locked loops. A reference signal is supplied to the system, and the phase of an oscillator at the remote location is tied to this reference. A single coaxial cable joins the central and remote components of the system. Feedback is employed to render the phase of the remote oscillator independent of the length of this cable. A detailed analysis of the sideband generators used in the system is presented. Analysis of overall system dynamics shows that stability is easily achieved and is not impaired by the time delay of the transmission path to the remote unit.

High-speed, low-crosstalk chip holder for Josephson integrated circuits

Abstract: Describes the construction and performance of a compact chip mount for making multiple, high-speed, low-crosstalk contacts to a Josephson integrated circuit. The mount has a rise time of about 32 ps and worst case crosstalk between lines of -33 dB.

Simultaneous measurement of partial discharge and radio-interference voltage

Abstract: A new instrument has been developed which allows simultaneous measurement of partial discharge (PD) and radio-interference voltage (RIV) in insulation of high-voltage power apparatus. A distinctive feature of this instrument is that it fulfills the low input impedance (150-Ω) requirement of the RIV measuring standard (NEMA 107) at 1 MHz and, at the same time, presents a high input impedance in the frequency bandwidth used for PD measurement; this high input impedance is required for acceptable measurement sensitivity of PD on power transformers. The instrument has shown stable measuring characteristics during the 16 months that it has been in service at the IREQ HV Laboratory where it is used to test power transformers, reactors, disconnecting switches, capacitors, current and voltage transformers, and other apparatus. The HV Laboratory personnel confirm that the device is practical and easy to handle during tests and saves a considerable amount of time.

Measurement of the state of battery charge using an improved loaded voltmeter test method

Abstract: An improved loaded voltmeter test (ILVT) was developed based on the preparation of a table of voltage measurements of the tested battery with a constant resistor load as a function of the state of charge. The function is stored in the memory of the microcomputer; when a certain value of the charge is then needed, it can be found using the ILVT and the stored function. The action of the power system is not disturbed. A circuit based on this method was built and tested at Tel Aviv University, Israel. Half as many errors occurred when the ILVT was used as when the conventional loaded voltmeter test was used. Although the system consists of only lead-acid batteries, the ILVT is also suitable for testing other types of batteries.

The calibration of a DAC using differential linearity measurements

Abstract: The differential linearity adjustment procedure offers an accurate method of digital-to-analog converter (DAC) adjustment with only modest accuracy in the instrumentation. The author shows that the worst case error in linearity due to a differential linearity error (DLE) of e in the upper N bits is bounded by Ne/3. Self-heating effects and output drive asymmetry can cause superposition errors which also degrade the linearity of the DAC. The effect of the resolution of the instrumentation on the final gain adjustment is shown to increase exponentially with the number of bits corrected.

Microwave interferometer for measurements of small displacements

Abstract: Two microwave interferometer systems developed for noncontact measurements of small displacements in an electromagnetically semitransparent medium are described. Arrangements for testing the instruments and experimental results are presented. The principal characteristics of the systems, e.g. the output signal versus the displacement of the scattering object, are linear for the two-way losses in the medium between the antenna and the object below 60 dB. The maximum displacement of the object is limited to a half-wavelength in the test medium by the interference between the signal backscattered by the test object and the signal reflected from the antenna.

The automatic measurement of TV-port microwave junctions by means of the six-port technique

Abstract: An automated precision measurement method for determing arbitrary (passive, active, or nonreciprocal) TV-port microwave network parameters is reported in this paper. Incorporating TV separately calibrated six-port reflectometers, which are isolated from each other, the isolated TV-six-port ANA (INSPNA) can be used to measure any TV-port junction via a group of TV measurements at a group of TV calibrated excitations. The calibration procedure of INSPNA is very simple because of the isolation and the only standard needed is an unknown length of precision transmission line. The isolation needed between each two ports is about 60 to 70 dB plus the gain of the TV-port under test to keep the calibration error within 0.1 percent.

An improved automatic test system for VLSI parametric testing

Abstract: Automated and thorough characterization of MOS transistors has been made possible by using a minicomputer-based instrumentation system. A low-current circuit capable of forcing current levels down to the range of 10 pA has been designed on the personality board, allowing fast measurements of subthreshold characteristics. A comprehensive test program has been developed to extract device parameters, such as threshold voltage, subthreshold slope, intrinsic mobility, mobility degradation, effective-channel doping, body effect, ΔL, ΔW, series resistance, and carrier-saturation velocity. Data management software also provides detailed statistical analysis. The technique is found to be a powerful and essential tool for VLSI process development.

A stable and accurate current-comparator-based quadrature-current reference for power frequencies

Abstract: A current-comparator technique for obtaining a pure quadrature-current reference for power frequencies is described. The current in a solid dielectric capacitor of relatively high capacitance value or in an electronic inductor is compared, using the current comparator, to the current in a “lossless” gas-dielectric capacitor of relatively low capacitance value. The difference current derived from the output of the detection winding is added, through a feedback circuit, to the current in the solid dielectric capacitor or the electronic inductor resulting in a stable and pure quadrature current. The instability and loss angle of the quadrature current are not more than ±5 ppm and ±5 μrad, respectively. This quadrature current source is used to provide a reference current in an active/reactive power comparator bridge for calibration of active/reactive power meters.

A four-point probe method with increased accuracy for the local determination of the thickness of thin, electrically conducting layers

Abstract: The error analysis for an infinite thin conductive plate shows that a four-point probe resistivity-to-thickness ratio measurement method with circularly arranged contact tips based on two pairs of measured current and voltage values obtained by cyclical exchange of the connections yields extremely low measurement errors due to contact misalignment. Conventional four-point probe measurement methods are unsuitable if Schottky behavior occurs between the metallic contact and the sample. A novel four-point probe measurement method using an ohmic (alloyed) auxiliary contact at the edge of the sample for current feed-in is presented. Both methods were tested for thickness measurement on thin epitaxial InP and GaAs layers and compared with each other. The results showed very good agreement. The accuracy was about 3 percent.

A digital system for measurement of resonant frequency and Q factor

Abstract: A new automatic computer-controlled system for accurate measurement of the resonant frequency and Q factor of radio frequency and microwave resonant circuits was developed and tested. In this system, the inflection points of the resonance curve are identified through a process of mathematical evaluation using an on-line digital computer and utilized to calculate the resonant frequency and the Q factor. The primary advantage of the system is that the results are independent of the resonant circuit characteristics at the resonant frequency and the 3-dB points, amplitude and frequency drift of the signal source, as well as detector instabilities. An experimental system operating between 1 and 2 GHz was designed, assembled, and tested with a laboratory minicomputer PDP 11/34 used for data acquisition and processing, as well as for overall system control. The measured range of Q factors is 100–1500, with estimated uncertainties of 40 ppm in the resonant frequency and 7 percent in the Q factor for a resonant circuit with a Q factor of 1000.

A dynamic test method for high-resolution A/D converters

Abstract: A dynamic test method is described for A/D converters having up to 16 bits of resolution. The technique exercises the test converter with stepped input changes, simulating the output of an S/H amplifier. Dynamic errors as low as 4 ppm can be measured within 4 ss following a step change as large as 20 V.

Effect of shielded room on standard magnetic field

Abstract: The near-zone magnetic field generated by a small loop antenna has been used for sensitivity test of a radio receiver. When external interference fields exist around the antennas, the test must be carried out in a shielded room. The formulas to estimate the effect of the shielded room on the standard magnetic field are derived for the coaxial and the coplanar alignments of the loops. The differences between the values calculated from the formulas and measured ones were within ±0.15 dB up to 50 MHz.

Carrier-frequency estimation based on the location of the spectra peak of a windowed sample of carrier plus noise

Abstract: The frequency of an unmodulated (CW) carrier frequency transmission may be estimated by identifying the location of the peak value of the spectrum of a windowed sample of T-seconds duration. The authors quantitatively evaluate the effect of window shape and length (leakage) as well as the effect of additive broad-band noise on the accuracy of this method of estimation. An interesting result is that neither elaborate `shaping' of the window, nor the use of the `least mean-squared' error method will have much advantage over the use of the spectral peak in a rectangularly windowed sample, unless the signal-to-in-band-noise ratio is of the order of 50 dB or better.

A reliable microprocessor-based defibrillator analyzer

Abstract: A scheme for a reliable microprocessor-based defibrillator analyzer for accurate measurement of various parameters of a dc defibrillator is proposed. A defibrillator, being a life saving device, needs routine calibration since any errors can have deleterious effects on the myocardium.

Programmed data logging in forest harvesting using floating-aperture data compression

Abstract: A floating-aperture data compression algorithm has been employed in the design of a data acquisition and recording system for monitoring human and machine performance variables in forest harvesting operations. Use of the algorithm allows multiple analog and digital variables to be sampled but not necessarily recorded at 1/1000-min intervals. Data are only recorded when changes on a channel exceed a preset tolerance. Analysis of one of the analog channels recorded in the field illustrates a 52:1 data compression ratio compared with data both sampled and recorded at 1/1000-min intervals. The complete data acquisition and recording system was designed to meet the requirements of field operation and its field use has verified that it functions correctly.

A new approach to reducing power dissipation in thermistor probe for temperature/frequency converter based on astable multivibrator

Abstract: A novel approach to reducing power dissipation in a thermistor probe for temperature/frequency converting circuit based on IC op-amp astable multivibrator is described. The output/input relation is linear over a wide temperature range with sensitivity 35 Hz/K. Experimental results are given to support the theoretical conclusions.

Operation of a hydrogen maser with a state-mixed beam

Abstract: Operation of a hydrogen maser with a beam having equal populations of atoms in the (F=1, mF=1) and (F=1, mF=-1) hyperfine states is described. The elimination of the magnetic inhomogeneity shift by this means is confirmed. The effect of the state mixing on the frequency stability of the maser is investigated.

Microwave short-pulse generator for bed-level detection

Abstract: Describes the design and testing of a short-pulse microwave radar system which is simple both in design and operation. The radar can be used for measuring with accuracy targets which are very near the measurement system. A very simple step-recovery diode circuit is used to generate the radar pulses. Experimental testing has been conducted in the laboratory using metal and limestone targets.

Response linearization of a diode detector type radio frequency electric field probe

Abstract: An EPROM-based linearization circuit with a resolution of 0.1 percent of full scale has been designed to linearize the response of an orthogonal dipole electric field probe terminated with diodes. Design approach, performance, and probe characteristics are discussed. The nonlinear transducer response is first modeled with a fourth-order polynomial which fits the log-transformed calibration data. The equation is then evaluated at discrete points determined by the memory size and the A/D converter resolution. The antilog of the dependent variable is loaded into an EPROM memory for subsequent readout with a D/A converter and summing network. The response of other nonlinear transducers can be linearized by this method.

Two-phase frequency-conversion type spectrum analyzer for low-frequency noise measurement

Abstract: An improved analog spectrum analyzer, which is suitable for noise analysis at very low frequencies, is presented. It is composed of two multipliers, two squarers, a summation circuit, and an integrator. This analyzer has half the value of the statistical error compared with that of the conventional analog analyzer. The design principle, actual circuit, and examples of the measured noise spectra at 0.05-1000 Hz are given. Certain specific measurement errors are also discussed theoretically.

An alternating current bridge for comparing four-terminal-pair impedances at ω = 10 4 rad/s

Abstract: An AC bridge has been developed for comparing capacitances from 10 to 1000 pF and resistances from 1 to 100 kΩ with a relative uncertainty of about 6×10-8 at ω=104 rad/s using an inductive voltage divider (IVD) with a nominal ratio of 1:10. Apart from these two quantities the difference in the dissipation factor of the capacitances can be determined with an uncertainty of about 9×10-8 and the difference in the time constants of the resistances with an uncertainty of about 2×10-11 s. It is proved that the uncertainty, particularly in the measurement of capacitances and resistances, can be considerably reduced, because it mainly depends on the errors of the IVD. This bridge has been developed to derive the SI unit ohm from the SI unit farad at the Physikalisch-Technische Bundesanstalt (PTB).

Utilization of the tunability of the lead-salt diode laser for a fast and local measurement of specific gas density

Abstract: In the optical gas monitoring method using a lead-salt diode laser, a spectral scanning operation of the diode brings an immunity against spectral interference which has limited the sensitivity of prevailing methods. Local, sensitive, and noncontacting features as well as quickness are attained simultaneously. Experiments for atmospheric methane showed a sensitivity of 0.3 ppm over a path length of only 1 m. Density data were obtained at every 4 s and the immunity for spectral interference was demonstrated. Theoretically, a sensitivity of 0.015 ppm for 1 m is expected.

Error analysis of phase-insensitive coherent (homodyne) detectors

Abstract: The phase and amplitude errors of a phase-insensitive coherent (homodyne) detector are analyzed. The detector consists of two balanced mixers which are fed in quadrature phase by one of the RF inputs, followed by a phase-quadrature combiner. Inherent detection errors due to an unwanted carrier in the double sideband modulated signal are analyzed first. Then errors due to the amplitude and phase unbalance of the two mixers and phase unbalance of the combiner are analyzed. For narrow bandwidths it is shown that all errors except those due to the unwanted carrier can be mitigated with careful design of the combiner, using appropriate trim adjustments.

Noise equivalent circuit of linear passive two-ports with applications to transmission lines

Abstract: A new representation of the thermal noise of linear passive two-ports, expressed in terms of the Thevenin equivalent circuit and convenient to circuit designers, has been derived. This representation is applied to the determination of the contribution of the noise of a transmission line (a special case of a two-port) to the total noise of a noise thermometer system. Preliminary experimental results from measurement of temperature with a noise thermometer connected via a long transmission line encourages further development of practical noise thermometers.

A frequency-compensated high-voltage current-comparator-based capacitance bridge for shunt reactor loss measurement

Abstract: A current-compensating technique for making a high-voltage current-comparator-based capacitance bridge insensitive to frequency fluctuations when used for measuring shunt reactor loss is described. A compensating current, proportional to twice the change in the current through the reference capacitor due to frequency fluctuations, is forced into the comparator winding through which the current from the reference capacitor passes resulting in a current in that winding having frequency characteristics similar to those of the reactor current. This compensating current is derived from a reduced replica of the applied high voltage or from the current through the reference capacitor. It need not be supplied with great accuracy for it is only a small fraction of the reference current. Thus the effect of frequency fluctuations on the inductive balance of the bridge is eliminated without sacrificing the inherent high accuracy of the high-voltage current-comparator-based capacitance bridge.