Showing papers in "IEEE Transactions on Instrumentation and Measurement in 1977"

Phase Noise in Oscillators: A Mathematical Analysis of Leeson's Model

Abstract: This paper is devoted to one aspect of the study of phase noise in oscillators: how an oscillator reacts to internal noise that occurs in the active element. The following theoretical analysis will lead us to express the Leeson's model in a more general form.

A Precision Silicon Transistor Thermometer

Abstract: This article describes a mass-producible electronic thermometer employing an inexpensive transistor as a temperature sensor The instrument features ±01°C accuracy from -50 to + 125°C; ±002°C stability throughout a 1000-day 125°C temperature cycle test; and probes that are freely interchangeable with no calibration by user Probes need be factory-calibrated at only one temperature, and are based on a novel low-thermal-mass hermetic transistor package Also described are the theoretical analysis and experiments carried during development It is shown that sensor transistor Vbe will vary almost linearly with temperature if collector current is an appropriate quadratic function of absolute temperature Effects of various current functions on Vbe linearity are theoretically analyzed and experimental results given for comparison The technique used to find the optimum current function is explained, and the circuit which generates the function is described It is shown that using a more expensive function generator and a 3-point sensor calibration will yield ±001°C accuracy Also discussed is the degree to which different commercially available transistors conform to the theoretical predictions Criteria are given for selecting an appropriate transistor type

Thermistor Multivibrator as the Temperature-to-Frequency Converter and as a Bridge for Temperature Measurement

Abstract: The symmetrical multivibrator, one timing resistor of which is replaced by a network consisting of a thermistor and passive resistors, is analyzed. The circuit represents at the same time a linear temperature-to-frequency (T-f) converter and a multivibrator bridge (MB), both having the same linearity range at any thermistor network configuration. When the balancing state is reached at an inflection point, the sensitivities of the converter and the bridge are the same. The MB has higher sensitivity than the Wheatstone bridge (WB) and can be balanced independently of the inflection point in the wide range. The converter and bridge performances with practical thermistor transducers are analyzed theoretically and numerically.

A System for Locating Points, Lines, and Planes in Space

Abstract: A microprocessor-based system for locating points, lines and planes within a cubic space 50 cm on a side is described and its performance evaluated. The technique is based on measuring the transit times of a shock wave produced by a small electric spark to each of 3 linear orthogonal microphones. Arranging 3 spark gaps in a plane permits the determination of the orientation of lines and planes in space. A technique is described to compensate for air temperature variations which have a direct effect on system repeatability. The effect of random room air currents has been studied. The linearity of the system was measured and found to contain an error of ±0.12 percent of full scale. Overall worst case (99.73-percent confidence interval) system accuracy was found to be 0.08 ± 0.96 mm.

Reactive Power Meter for Nonsinusoidal Systems

Abstract: This paper describes a novel reactive power meter realized by electronic circuits that determine successively the terms of the equation Q = ?n=1?VrIrsin?r for n significant harmonics. The harmonic contributions to the total reactive power is determined by electronic simulation of the mathematical expression that sets the orthogonal condition of two functions in a periodical interval. Partial reactive power with its sign are stored and added in a circuit to get at the end of the cycle the total reactive power. A control system permits operation in a repetitive form.

Generation of EM Susceptibility Test Fields Using a Large Absorber-Loaded TEM Cell

Abstract: This paper discusses the development of an electromagnetic simulator for accurate generation of broad-band suspectibility test fields within a shielded environment. The simulator consists of a large, 3 m X 3 m X 6 m, rectangular transverse electromagnetic (TEM) transmission cell that is loaded with RF absorber to suppress multimoding at frequencies above the cell's waveguide cutoff or resonant frequencies. The paper describes the measurement facility and technique, and the experimental verification of pertinent test paramenters such as system VSWR, insertion loss, and test field uniformity. The measurement system is anticipated to provide swept, automated susceptibility measurements of electronic equipment to CW, pulsed, and EMP fields within the frequency band, 10 kHz to 1 GHz.

A Direct Time-Domain Measure of Frequency Stability: The Modified Allan Variance

Abstract: A simple filter is shown to closely approximate the procedure used to compute the "Allan variance," an often used measure of the short term frequency stability of oscillators. This modified Allan variance is obtained by measuring the rms value of the instantaneous frequency waveform after filtering. Some advantages of the modified Allan variance include ease of implementation for short averaging times and better behavior when the instabilities include periodic components. The effect of the bandwidth of the measuring process on the minimum usable averaging time is also discussed.

Phase and Amplitude Modulation Effects in a Phase Detector Using an Incorrectly Balanced Mixer

Abstract: A very simple theoretical model of a phase detector using a double-or single-balanced mixer is described. The main characteristics of this device are depicted and the effect of the balance in the mixer is analyzed. Experiments show that the model describes the behavior of the unbalanced phase detector in a satisfactory way.

A Linear Position Transducer Using a Magnet and Hall Effect Devices

Abstract: Magnets and magnetic field sensing devices are often attractive in instrumentation because they are noncontacting, small, and independent of the media's dielectric constant. The nonlinearity of the magnetic field with distance is a problem, however. A circuit to remove this nonlinearity and also to reduce the effective temperature coefficient is described. The circuit is used in a clinical dental research laboratory to measure movements of the jaw.

Determination of Current Transformer Errors at Primary Currents up to 100 000 A

Abstract: A method is described for testing precision current transformers, particularly devices with very high values of rated primary current and rated secondary currents up to 200 A. It makes use of the well-known differential method (Arnold, Hohle), substituting, however, the common resistor with an electronic operational amplifier, thus yielding an almost negligible resistance and a very high sensitivity of 0.01 ppm. Results of ratio error measurements are reported at values of primary currents between 500 and 100 000 A.

Spectral Analysis of Synthesized Signals in the mm Wavelength Region

Abstract: In this paper some experimental results on the spectral purity along a multiplier chain from 5 MHz up to 600 GHz are reported. The measured points are compared to the numerical data which can be obtained from simple calculations considering the phase noise spectrum of the crystal oscillators used to drive the multiplier chains.

Advances in Monitoring of Velocities and Densities of Particulates Using Microwave Doppler Effect

Abstract: Recent advances in monitoring of velocities, densities, and mass flow rates of particulates using a microwave Doppler radar are presented. It has been found that the Doppler signal scattered by the flow field of particulates contains information not only about the mean velocity of the field (mean frequency of the Doppler signal) but also about the mean density of the field (rms value of the Doppler signal). Experimental results obtained using a X-band Doppler module are presented.

A Guided Radar System for Obstacle Detection

Abstract: This paper describes the operation of a guided radar system capable of detecting human targets or other obstacles along a guideway at ranges up to a quarter of a mile. The concept is based on the use of so-called leaky coaxial cables which were first developed for the communications field. Two cables, installed on either side of the guideway, act as the medium of propagation in the form of a surface waveguide. The instrument detects the presence of obstacles which perturb the EM field induced in the guideway. The system is centered around a minicomputer which controls the transmission of RF pulses down the guideway and the reception of the return signal. The computer also performs further processing of the return signal in the form of integration, filtering, and removal of stationary clutter, the result being a very sensitive instrument. Results of experiments are presented which demonstrate the usefulness of this instrument in determining the important electromagnetic characteristics of leaky cable waveguides.

Microwave Properties of Yarns and Textiles Using a Resonant Microwave Cavity

Abstract: Modified cavity perturbation methods for permittivity measurements of yarn and textile are described. A cylindrical cavity which is split into equal parts is designed to operate in the TE011 mode. The dielectric yarn is placed across the midplane of the cavity and a textile sample is placed in the cavity on a low-loss dielectric sheet in annular form. The shift in the resonant frequency and change in Q-factor are measured and the complex permittivity is calculated.

Measurement of Static AM-PM Conversion in Frequency Multipliers

Abstract: The generation of very narrow spectral lines in the far-infrared by frequency synthesis from VHF precision sources requires very stringent specifications on the spectral purity of the source and on the phase noise introduced by the synthesizer. The dc measurements of the AM-PM conversion in different multiplier stages are presented in this paper: stages employing transistors, varactors and step-recovery diodes are examined. The results show that a few degrees per dB of input level variation are typical for the AM-PM conversion reported to the input in a simple, carefully built and well tuned multiplier stage employing any of the mentioned solid state devices. This value is shown to be unlikely to degrade more than the expected n2 factor the spectral purity of a signal with AM noise as low with respect to PM noise as it is in the output of a good quartz crystal controlled oscillator; however, such a conversion could become a source of phase noise, with degradation of the spectral purity, for a signal with a slightly worse AM noise.

Temperature-to-Time Converters

Abstract: In this short paper, two circuits [1], which employ operational amplifiers are considered for converting temperature to time A procedure, suggested in [2] is employed to obtain a wide range of temperature The theoretical deviation curves obtained show that these time converters have wide range of temperature for given slope and percentage of linearity

The Dynamic Response of a Resonant Frequency Tracking System

Abstract: A study of a resonant frequency tracking system, to be used in measurement systems where the sensing element is a resonant structure is presented. The tracking system was used to lock an oscillator to the resonant frequency of a cavity operating in the X-band. The resonant frequency of the sensor was assumed to be a function of the quantity being measured. A theoretical analysis of the resonant frequency tracking system was done for both linear and nonlinear operations resulting from the properties of the sensor. A model of the tracking system was designed and an analysis of the system response was performed using computer techniques.

Measurements and Computations of Electric Field Intensity and Power Density

Abstract: Conversion equations for converting the transmitting power, receiving power, or receiving voltage to electric field intensity and power density are derived and discussed. If the antenna factor, antenna gain, and the cable parameters are known, the electric field intensity or power density at some distance from the transmitting antenna may be determined by means of a specific conversion equation for a given signal frequency. The developed conversion equations may aid the electronics engineers to compute the electric field intensity and power density in a quick way.

Thermistor Multivibrator Bridge with the Variable Balancing Point Position

Abstract: This paper describes a thermistor multivibrator bridge and temperature-to-frequency converter for the case where the output characteristics have different balancing and inflexion points. The influence of the difference between balancing and inflexion temperatures (T0 - Ti) on sensitivity is analyzed.

Noise-Loading Analysis for a General Memoryless System

Abstract: An expression for the noise power ratio of a memoryless nonlinearity with finite output power is given. This generalizes previous results which were restricted to nonlinearities with finite Taylor series expansions. Simpler proofs of these earlier results are presented.

Automatic Monitor for Microwave Resonators

Abstract: An instrument was developed to simultaneously measure both the resonant frequency and the bandwidth (which is related to the loaded quality factor) of a resonant microwave cavity under continuous operating conditions. Voltages proportional to both parameters monitored are obtained at the output. The principle of operation, the main causes of error and the accuracy obtained for actual measurements are presented. This instrument could easily be connected to a digital data-acquisition system; it could also be adapted to study resonance phenomena at frequencies other than microwaves.

Optimization of the Wheatstone Bridge Sensitivity

Abstract: Analysis of the Wheatstone bridge has shown that the optimization of the maximum normalized bridge sensitivity can be achieved if the power dissipation in two of the four bridge elements approaches infinity for a given source voltage. Results also indicate that the power input to the bridge can be minimized as a function of maximum normalized bridge sensitivity.

Nanosecond Passive Voltage Probes

Abstract: Passive voltage probes with megohm input impedance at dc are traditionally understood as RC compensated dividers, but this is inadequate even for system rise times as slow as 100 ns. Qualitative understanding of faster probes is generally in terms of resistive damping of resonances, but this has been notably successful in practice only with the use of resistive conductor probe cable as introduced by Kobbe. This paper demonstrates that nanosecond probes can be understood and designed for a systematic transmission line viewpoint. The properties of the resistive conductor probe cable as a transmission line are an essential feature, and the original motivation for the use of resistive cable as damping of a resonance is seen to be largely irrelevant for nanosecond probes.

Ultra-High-Speed Methods of Measurement for the Investigation of Breakdown Development in Gases

Abstract: Several electrical and optical methods of measurement for the investigation of breakdown development in gases are described. Thereby not the sensitivity but the temporal resolution is emphasized. For this reason especially the fast voltage collapse at the gap and the corresponding current rise can be investigated. This is even true in highly compressed gases. Furthermore, the exact synchronization of electrical and optical test methods is described. By this way both the temporal and the spatial discharge development can be investigated simultaneously.

High-Resolution Shaft Speed Measurements Using a Microcomputer

Abstract: A Motorola 6800 microcomputer has been applied to the measurement of instantaneous angular velocity at one degree intervals on a pair of coupled shafts. Velocity is determined by accurately measuring the time intervals between pulses produced by shaft encoders. Variations in relative velocity can be detected when precision timing is available. Using an essentially software approach time can be measured in 30-?s increments. The number of instructions in the timing loop can be reduced by adding a small amount of hardware to permit parallel data acquisition. Time increments of 12?s were obtained using inputs from two shafts. The results of measurements on a pair of shafts coupled by noncircular gears is included as an example.

Junction Impedance Measurements of Diodes by a Simplified Lock-In Amplifier

Abstract: A lock-in amplifier with most parts of its functional components substituted by integrated circuits is described here. This amplifier is far from expensive and is free from the trobles arising from temperature compensations and impedance matchings such as usually occur in conventional transistorized amplifiers. This instrument, operating at frequencies from 20 Hz to 100 kHz, has a noise rejection ratio of 40 dB and is suitable for junction capacitance and resistance measurement of diodes under reverse or forward bias.

A Digital Method of Frequency Multiplication and Its Application to Numeric Spectrum Analysis of Periodic Signals

Abstract: A digital way to produce an integral multiple of the frequency of periodic trigger pulses is described. This procedure is used to generate the sampling pulses for the ADC of a time-series analyzer. The device which implements this method is called sampling frequency generator (SFG). A comparison is made between this digital method and the analog frequency multiplication method by means of a PLL.

Application of the Multiharmonic Fourier Filter to Nonlinear System Fault Location

Abstract: The Fourier Response Analyser (FRA) has become a widely used and accepted instrument with clearly defined noise and harmonic rejection characteristics. In a nonlinear system, however, the higher harmonics contain useful information on the system under test which this paper shows can be used by the test designer to assess system quality and pinpoint nonlinear fault locations if the system is classified as "sick." Backlash, saturation, and deadzone conditions are thereby detected in an analogue simulation model previously matched to a hardware servomechanism. The higher harmonic components are estimated by a special version of the FRA incorporating the Multiharmonic Fourier Filter (MFF) which is based on the same correlation principle as is used to detect the fundamental response.

The Use of Time-Domain Techniques for Microwave Transistor s-Parameter Measurements

Abstract: The determination of microwave transistor s parameters over a frequency band up to 10 GHz by means of timedomain techniques, involving Fourier analysis and deconvolution of transient response data, is described. Details of the measurement system are presented and advantages of such techniques over conventional network analyzer techniques are discussed. Results obtained for developmental ion-implanted/diffused-silicon bipolar transistors with ft values above 5 GHz are presented.

Doppler Microwave Cavity Monitor for Particulate Loading

Abstract: A real-time particulate loading monitor using a multimode microwave cavity is described and analyzed Microwave power in the cavity volume is scattered with a Doppler shifted frequency by particulates suspended in a gas flowing through the cavity Detection of the scattered radiation by beating it with the nonscattered radiation provides an indication of the particulate loading A proof-of-concept experimental setup is described with the obtained results The monitoring system is not very sensitive to particulates smaller than 1 ?m However, it is very well suited to operations where the effluent gas is under high pressure and temperature