Showing papers on "Spectrum analyzer published in 1985"

Real-time eeg spectral analyzer

Abstract: An electroencephelograph (EEG) signal analysis system automatically determines and displays, on a real-time basis, the frequency content of spontaneous EEG signals from the brain. The analog EEG signals from a plurality of channels are sampled and converted to digitized EEG waveforms during a continuing sequence of epochs of predetermined time duration. The digitized EEG waveform for each epoch and channel is transformed from the time domain to the frequency domain to produce a frequency spectrum representing amplitude of the EEG signal as a function of frequency. The digital data is screened both prior and subsequent to the transformation to identify those epochs which contain artifacts. During each update period, the frequency spectra for each channel from the artifact-free epochs are averaged. The amplitudes of each averaged frequency spectrum for frequencies in each of four basic frequency bands are then summed. The result is an amplitude value for each of the four frequency bands at each channel. The four amplitude values are used to update a display which contains a graphical representation of the amplitude in each of the four bands in a different color. The amplitude values are also compared with previously recorded base line values, and an audible or visual warning indication is provided when predetermined variances from the base line values occur.

Measurements of acoustic impedance in a free field with two microphones and a spectrum analyzer

Abstract: A technique is presented for evaluating the normal acoustic impedance at the surface of a panel of absorbing material in a free field. The evaluation is achieved by measuring the pressure and the acoustic velocity with two microphones set very close to the panel. This technique allows measurements of impedance for panels of area about 1 m2, the two microphones being located very close to the panel so that, contrary to other methods, the effect of the finite dimension of the panel is negligible. Because of the very small spacing between both microphones, this technique allows precise measurements only for frequencies higher than 500 Hz.

The measurement of acoustic noise generated by moving artificial sediments

Abstract: Laboratory measurements relating to the acoustic detection of marine sediment transport are reported. A series of underwater measurements have been conducted on agitated artificial sediments, and the acoustic noise generated by interparticle collisions monitored. Measurements of the total acoustic pressure and spectral pressure levels were made on a wide range of particle diameters for different values of the mass of agitated material, the collision velocities, and the swept bandwidth of the spectrum analyzer. The objective was to relate the total pressure level to the mass of mobile material and ascertain if there was an acoustic spectral signature unique to particle size. This information could then be used to guide the interpretation of acoustic measurements of bedload transport taken in the marine environment and provide specifications for the development of an acoustic system to monitor remotely the material moving along the seabed.

A Fast Response Continuous Analyzer for Halogenated Atmospheric Tracers

Abstract: A fast response version of the continuous SF6 analyzer originally introduced in 1976 has been developed. The new continuous analyzer has a response time constant of 0.36 s, which is 4–30 times faster than previous analyzers. The very fast response of the new analyzer allows it to be used to investigate the fundamental nature of atmospheric turbulence and diffusion processes. The new design has been thoroughly tested in laboratory and field conditions over an ambient temperature range from 4° to 40°C and an elevation range of 265 to 2130 m above sea level. The reproducibility in the response of the new analyzer was approximately ±15% over a one-month period. In automobile and aircraft sampling platforms, the reproducibility in response was less than ±12% for periods as long as 7.5 h and elevation changes exceeding 1800 m. The rate of baseline change was <1 ppt min−1 in the laboratory, <10 ppt min−1 in an automobile platform, and 15 ppt min−1 in an aircraft platform. The size, weight, and power con...

An analyzer for in-line measurement of expiratory sulfur hexafluoride concentration.

Abstract: An infrared analyzer for the inert tracer gas sulfur hexafluoride (SF6) is described and evaluated. The analyzer consists of a transducer and a processor unit. It is designed to operate in a nonrebreathing system with a ventilator and a computer. The transducer, which is placed over a cuvette with windows in the ventilator tubings, reads the SF6 concentration in the airway during the expiratory phase. At the end of the inspiratory phase, the zero level of the instrument is automatically reset. The response time and linearity of the analyzer were tested, and interference by other gases was assessed. Full response was reached within 20 ms after a sudden introduction of 0.5% SF6 into the cuvette. The analyzer-computer system had adequate linearity below 0.5% of SF6. Oxygen, nitrogen, and humid air had no influence on the analyzer signal. One hundred per cent nitrous oxide, 4% enflurane, 4% isoflurane, and 4% halothane caused signals corresponding to 0.010, 0.023, 0.022, and 0.043% SF6, respectively. Due to the method for zero reset, the importance of interference from these gases is greatly reduced when inspired and expired concentration approach each other. The disturbance from CO2 (10% CO2 gave a signal corresponding to 0.020% SF6) can be compensated for by including a CO2 analyzer in the set-up. The rapid response and the high sensitivity of the analyzer may make it useful for studies of pulmonary gas mixing and for measurements of lung volume during mechanical ventilation.

Astronomical polarimeter with 2-D detector arrays.

Abstract: It is shown how fast (50–100 kHz) piezoelastic modulation of the full Stokes vector can be used in combination with large CCD-type detector arrays with long integration times. The technique is to use an optical demodulation system (replacing the lockin amplifiers in corresponding single-channel detector systems). This allows the CCD detectors to be used with integration times and readout rates as in ordinary photometry. Including an optical phase switch in the system, the effect of the large pixel-to-pixel sensitivity variations can be removed from the recorded polarization images. The beam splitter that suppresses atmospheric noise can be located immediately before the detectors instead of being part of the polarization analyzer.

Optical signal processing with magnetostatic waves

Abstract: Magneto-optical devices based on Bragg diffraction of light by magnetostatic waves (MSWs) offer the potential of large time-bandwidth optical signal processing at microwave frequencies of 1 to 20 GHz and higher. A thin-film integrated-optical configuration, with the interacting MSW and guided-optical wave both propagating in a common ferrite layer, is necessary to avoid shape-factor demagnetization effects. The underlying theory of the MSW-optical interaction is outlined, including the development of expressions for optical diffraction efficiency as a function of MSW power and frequency, device geometry, materials properties, and other relevant parameters. Recent experimental observations of anisotropic Bragg diffraction and collinear TE↔TM mode conversion induced by MSWs in yttrium iron garnet (YIG) thin films suggest that high-performance MSW integrated-optical devices are feasible. Diffraction levels as large as 4% (7-mm interaction length) and a modulation dynamic range of ∼30 db have been demonstrated. Potential signal processing applications are mentioned, including: spectrum analyzers, convolvers/correlators, deflectors, non-reciprocal optical isolators, and tunable narrowband optical filters. Advantages of these MSW-based devices over the analogous acousto-optical devices include: much greater operating frequencies, tuning through the MSW dispersion relation by varying either the rf frequency or the applied bias magnetic field, simple MSW transducer structures (e.g., a single stripline), and the potential for very high diffraction efficiencies.

Acousto-optic dispersive light filter

Abstract: (57) The invention is directed to an acousto-optic dispersive tight analyzer (AODLF) which is an electronically adjustable spectroscopic device capable of instantaneously monitoring many wavelengths with a fixed drive frequency. The AODLF has about a one octave range, whose center is selected by changing the RF. The resolution of the AODLF in the infrared is several thousand, and it is electronically adjustable.

Improved estimation of fructosamine, as a measure of glycated serum protein, with the Technicon RA-1000 analyzer.

Abstract: We present an improved fructosamine assay for use with the Technicon RA-1000 analyzer. Features of this assay include: specimen throughput of 100 per hour, within-batch CV of 1.5%, between-batch CV of 2.4%, standard curve linear up to 24.9 mmol of fructosamine per liter, and good correlation (r = 0.82) with hemoglobin A1.

Portable sampling spectrum analyzer

Abstract: A portable spectrum analyzer using frequency synthesis is used in the field to perform voltage amplitude measurements of specified channel segments in a multichannel configured coaxial cable environment The instrument is a microprocessor (28) based system, and includes an RF input (1) and keyboard (36) and function switch inputs and provides both aural and visual outputs by means of a speaker and an LCD display (27) A three stage frequency converter (7) including PLLs (11, 12 and 13) controlled by the microprocessor (28) allows for the automatic monitoring of a plurality of carrier channels or the display of both video and audio levels of a single channel Automatic adjustment of the input signal level is provided by attenuator pads (2 and 3) controlled by the microprocessor (28) Calibration is also automatically controlled by the periodic injection of a signal of predetermined level from a noise source (4) under the control of the microprocessor (28) The microprocessor is programmed to provide several modes of operation including a sweep mode, a zoom mode, and a memory mode In the sweep mode, the instrument continually scans all carrier channels automatically, each channel being presented sequentially and simultaneously in bar graph form on the LCD display (27) In the zoom mode, a single channel is displayed with both video and audio levels side by side In the memory mode, the operator can view data saved from measurements previously made at a selected location in the cable system

Rotating analyzer type ellipsometer

Abstract: A rotating analyzer type ellipsometer comprises a rotating analyzer for receiving light which is impinged on a sample with a predetermined incident angle and reflected by the sample, a rotary phase detecting apparatus provided so as to rotate unitarily with the rotating analyzer for generating a rotary phase signal as the rotary phase detecting apparatus rotates, a rotating mechanism for rotating the rotating analyzer and the rotary phase detecting apparatus, a photodetector for producing an output responsive to light which is passed through the rotating analyzer, and a computer for obtaining a phase difference between the rotating analyzer and the rotary phase detecting apparatus from a phase difference φo with which a difference between an output Ip of the photodetector and a theoretical value Io becomes a minimum or substantially zero by entering into the computer the output Ip of the photodetector and calculating the theoretical value Io while changing the values of the output Ip and an initial value φo of the phase difference.

Application of an E∥B spectrometer to PLT charge‐exchange diagnostics

Abstract: A TFTR‐type E∥B spectrometer was installed on the PLT to provide a wide energy range, mass resolving, horizontally scanning charge‐exchange diagnostic. In ICRF heating experiments, the new analyzer has provided hydrogen minority high‐energy ion tail measurements simultaneously with bulk deuterium ion temperatures over a range of equatorial viewing angles. Characteristics of the E∥B analyzer will be discussed. Data representative of the PLT operating regimes will be presented to illustrate the analyzer performance.

Digital graphic equalizer

Abstract: A digital graphic equalizer includes a pulse-sequence generator for generating a sequence of pulse signals, a first digital signal processor for filtering the pulse signals to produce a filtered signal, a digital-to-analog converter responsive to the filtered signal for producing a calibrating signal, and a loudspeaker responsive to the calibrating signal for propagating a calibrating sound in a listening environment, the frequency characteristics of the calibrating sound being subject to modification by the listening environment. A detector detects the calibrating sound as propagated in the listening environment and produces a detection signal representative thereof. An analog-to-digital converter is responsive to the detection signal for producing a digital signal corresponding thereto, and a second digital signal processor is responsive to the digital signal for producing a plurality of frequency-divided signals. A spectrum analyzer is responsive to the frequency-divided signals for analyzing the frequency characteristics of the calibrating sound as propagated in the listening environment and producing a compensating signal adapted to compensate for the modification by the listening environment of the frequency characteristics of the calibrating sound.

Measuring assembly for analyzing electromagnetic radiation

Abstract: The measuring assembly for analyzing electromagnetic radiation comprises the following structural groups arranged one behind the other in the beam path: at least one linear polarizer (2); at least one optically active element (3) of known optical activity, i.e. known frequency response of the rotation of the polarization plane; and at least one analyzer (4) the polarization direction of which has a fixedly set orientation with respect to the direction of transmission of the linear polarizer. The beam issuing from the analyzer (4) is passed through a photosensitive sensor (7,8) to a measuring circuit. The total intensity of the radiation under investigation is determined in various ways by forming a reference signal, namely by direct measurement with the optically active element temporarily removed from the beam path, by neutralizing a partial beam, or by a beam splitting analyzer. The measuring assembly permits very rapid analysis (up to real time measurement) of electromagnetic radiation at an extremely high resolution without requiring any mechanically movable parts. Fields of application of the measuring assembly are the determination of the optical center of gravity of the radiation, the determination of the spectral characteristic of the radiation, as well as spectrometric and/or photometric examinations of samples.

Well logging direct memory access system and method

Abstract: A generalized computer-based system and method for acquisition of nuclear well logging data, including downhole generation of energy and time spectral information. A downhole instrument traverses a borehole introducing high energy neutrons into the formation at prescribed depths. Resultant gamma rays are detected and converted into pulses which are amplified and conditioned. A downhole multi-parameter analyzer stores pulse height and arrival time for each detected gamma ray whereby time and energy spectra are formed. Spectra include, alone or in combination, time spectra of the neutron source, inelastic and capture energy spectra. From the source time spectra, peaks are detected and capture and inelastic gates referenced thereto. Also thermal neutron decay between source bursts is derived. From the energy spectra peaks including hydrogen or iron are detected and used for calibration and automatic gain control of the gamma ray detector. High speed buffer means and direct memory access enables access to memory by both the multi-parameter analyzer and CPU so as to avoid inhibiting data acquisition during processing of the acquired spectra by the CPU. Parameters including pulse discrimination level, detector gain, and gate positioning affecting the spectra generated downhole, which may simultaneously include inelastic, capture, and time distribution spectra, are variable in the analyzer by means of CPU control functions.

Frequency shift for removing spurious spectral components from spectrum analyzer output

Abstract: Apparatus for eliminating spurious spectral components from a spectral analyzer output signal An input signal is mixed with two separate local oscillator frequencies separated by a frequency offset value to produce two intermediate-frequency signals, which are processed in spectral analyzers The outputs of the analyzers are then compared to identify and eliminate any components that do not differ in frequency by the offset value

Perpendicular ion energy analyzer for hot-ion plasmas

Abstract: A miniature analyzer probe is described for measuring the component of the ion energy distribution perpendicular to the confining magnetic field in a hot‐ion plasma. The analyzer employs the magnetic field to exclude electrons due to their small gyroradii. Ions are selectively retarded by a positively biased collector. The limits on the operating regime of this analyzer are calculated. The device is used in the MIX 1 mirror machine where we measure an ion temperature of ∼100 eV and plasma density ≳1011 cm−3.

A New Four-Port Automatic Network Analyzer: Part I-- Description and Performance

Abstract: A four-port automatic network analyzer based upon a new concept has been tested in the 8-12-GHz range. An essential feature of this analyzer, compared with the six-port systems, is that only one detector is used, and one electronically adjustable reference load is added. In this paper, an electronically adjustable short circuit is used as the reference load. Hence, the analyzer is comparatively simple and compact since only a few components are required. Moreover, the quality of the components can be moderate. A small desk-top computer (HP 85) is satisfactory for handling measurement data, adjusting the short circuit, and presenting the result. A simplified theory required for the calibration and measurement procedure for the determination of the magnitude and the phase of an unknown load is included in this report, and experiments illustrate how the accuracy is improved when the calibration is gradially refined. The expected accuracy of the network analyzer is discussed in some detail. The simple design and the moderate demands on the component quality means that it should be ideal for millimeter-wave frequencies.

Velocity Profile Reconstruction Using Ultrafast Spectral Analysis of Doppler Ultrasound

Abstract: Abstmct-An ultrasound pulse Doppler system is discussed, capable of performing real time spectral analysis of data originating from a number of sample volumes. The use of a surface-acoustic-wave-based ultrafast spectrum analyzer allows for a large amount of Doppler data to be processed in a time equal to a few tens of microseconds for each equivalent channel. Sonograms comparable to those obtained in single gate-fast Fourier transform-based-Doppler systems can thus be simultaneously presented, showing the velocity distribution in different sample volumes as a function of time. Alternately, the instantaneous velocity profile can be mapped as a function of depth, thus allowing for the possibility of bidimensional imaging. A prototype flowmeter capable of processing Doppler data from 32 range cells in real time is described and preliminary results obtained in virro under simulated flow conditions are presented.

A Nanosecond Photon-Counting Fluorimetric System Using a Modified Multichannel Vernier Chronotron

Abstract: A new time-resolved photon-counting instrument with high data-gathering efficiency is described. The principle of operation is based on the measurement of the nanosecond temporal distribution of the emitted photon burst during the short duration of transient emission. The instrument is characterized by the unique capabilities of a modified vernier chronotron with plural coincidence circuits and serial-timing data memories, which serve as an efficient multichannel event-time analyzer of 1.5-ns time resolution. The data-gathering efficiency is improved by a factor of 20 or more in comparison with that of the conventional single-photon counting method. In regular operation, the time history of transient emission for the period of 144 ns is obtained; and for phenomena with longer duration, the time-scale expansion mode of operation is provided. To demonstrate the whole system performance, a fluorescence decay curve of 1-ppm quinine sulfate in 0.1-N H2SO4 is presented.

Automated acousto-optic infra-red analyzer system for monitoring stack emissions

Abstract: An improved automated acousto-optic analyzer system includes an acousto-optic tunable filter which is coupled with a source of radiation to produce pulsed light at predetermined wavelengths. This light is transmitted through a gas stack containing gases to be analyzed, to a distant detector. The configuration of the acousto-optic tunable filter, radiation source on one side of an environment of interest and a detector on the opposite side of an environment of interest produces spatial separation of the tuned, diffracted light from the undiffracted broad spectrum of the light source at the detector. This configuration eliminates the need for polarizers in the system. It also combines the tuning function of the AOTF with a chopping function, allowing extraneous radiation to be discriminated against. Thus the improved configuration of the disclosed invention permits effective operation of the gas analysis system in a gas stack characterized by extremely high ambient temperatures.

E∥B end‐loss‐ion analyzer for Tandem‐Mirror Experiment‐Upgrade

Abstract: We are constructing and testing a diagnostic instrument to investigate, in detail, ions emanating along magnetic field lines from the plasma region of the TMX‐U tandem‐mirror experiment. This analyzer (of Tokamak Fusion Test Reactor design) contains parallel electric and magnetic fields, which yield ion mass and energy spatial separation, respectively. A two‐dimensional array of 128 copper collector plates detects the particles. The entering ion flux is first well collimated and then focused onto the detector plane during the 180° bending in the magnetic field. This instrument is designed to measure higher particle energies than the present gridded end‐loss analyzers as well as determine the energy spectra more accurately. Tandem‐mirror plasma parameters to be investigated with this analyzer include end‐plug potential, average central‐cell‐ion energy, and plasma potential in the thermal barrier and nearby regions. We plan a time resolution of up to 2 kHz for each detector.

Spectral analyzer and direction indicator

Abstract: A spectral analyzer and direction indicator (10, 20) and includes reflection gratings (13, 15, 25, 27, 37, 39), associated optical systems (17, 19, 29, 33, 41, 45) and associated detectors (21, 23, 31, 35, 43, 47, 30). The reflection gratings (13, 15, 25, 27, 37, 39) are arranged to provide angles of diffraction which are utilized to determine spectral content and incidence direction of collimated or essentially collimated incident radiation.

Calibrating mechanism of an infrared analyzer

Abstract: An amplifying circuit for amplifying an output from a measurement wavelength detector consists of a preamplifier and a measurement signal amplifier provided at an output of said preamplifier. The measurement signal amplifier is provided with an input-resistance and a feed-back resistance, a variable resistance connected in series to a normally open switch, the series combination being connected in parallel to the feed-back resistance so that the gain of the measurement signal amplifier may be variable.

A wide-band, high-resolution spectrum analyzer

Abstract: A two-million-channel, 40 MHz bandwidth, digital spectrum analyzer under development at the Jet Propulsion Laboratory is described. The analyzer system will serve as a prototype processor for the sky survey portion of NASA's Search for Extraterrestrial Intelligence program and for other applications in the Deep Space Network. The analyzer digitizes an analog input, performs a 2 (sup 21) point Discrete Fourier Transform, accumulates the output power, normalizes the output to remove frequency-dependent gain, and automates simple signal detection algorithms. Due to its built-in frequency-domain processing functions and configuration flexibility, the analyzer is a very powerful tool for real-time signal analysis.

Measuring range and/or radial velocity of a moving target

Abstract: A continuous-wave FM radar system comprises a voltage-controlled RF oscillator (1) the output frequency of which is swept repeatedly in both senses by means of a voltage waveform generator (19), whose waveform cycle comprises two upward sweeps followed by two downward sweeps. The oscillator output signal is fed to an aerial (3) and a portion of the transmitted signal is mixed with the return signal in a mixer (7). The ranges and/or velocities of reflecting moving targets are determined by means of a computer (100) which is fed with the output of a spectrum analyser (15) for the resulting beat-frequency signals, range-velocity ambiguities due to Doppler shifts being resolved by determining each range and/or velocity from a pair of spectral frequencies which arise from sweeps of the oscillator frequency in one sense and in the other sense respectively. In order to make the task of the computer easier in deciding which frequencies constitute related pairs a signal storage and differencing circuit (11) subtracts the mixer output signals which arise from successive sweeps of the oscillator frequency in the same sense one from the other and feeds only the result to the spectrum analyser, thereby ensuring that the spectral frequencies outputted by the spectrum analyser correspond only to moving targets.

The use of a small, low-cost FT-IR spectrometer as a mobile analyzer for fluid streams

Abstract: Infrared analysis is well established as a prime method for identification of unknown samples. However, the instruments needed for recording a complete infrared spectrum have not lent themselves to mobile applications because of their inherent mechanical fragility. The design of a commercial low-cost FT-IR instrument described herein makes it particularly useful as a mobile analyzer since it is optically rugged and has sufficient on-board computer power to record high-quality spectra after being moved between locations. At the same time, it is physically small enough to be mounted on a standard lab cart along with the necessary accessories. We illustrate the use of this mobile, low-cost FT-IR for analyzing the evolved gases from Thermal Gravimetric Analysis, small pilot reactors, and the liquid eluant from Gel Permeation Chromatography.

Sample positioner and deflection energy analyzer for measurements of photofield emission

Abstract: A sample positioner and an electron energy analyzer for studies of photofield emission have been designed and constructed. The sample positioner allows photofield emission from every facet of a field emitter to be measured under illumination at arbitrary angles of light incidence and polarization. The electrons emitted from a selected facet are decelerated to a kinetic energy E0 by a series of cylindrical lenses and introduced into either one of two energy analyzers. The deflection energy analyzer, formed from two identical 127° cylindrical analyzers, is used when high‐energy resolution is required. The full width at half‐maximum height of the resolution function of this analyzer is proportional to E0 down to a minimum kinetic energy which is less than 0.5 eV, and is given by ΔEFWHM=(0.0390±0.0006)E0. The throughput depends on E0 due to a combination of resolution and aperturing effects, and varies as E3/20. The signal‐to‐noise ratio of the analyzer is limited to 2×104 by inelastic scattering of electrons...

Enhanced frequency determination for spectrum analyzers or the like

Abstract: An arrangement is provided for enhancing the accuracy of frequency determination in a spectrum analyzer or the like having a local oscillator heterodyned with and locked to a frequency comb, by providing a determination of whether the local oscillator frequency is above or below the comb frequency to which it is locked, thereby avoiding ambiguity in the determination of the local oscillator frequency.