Showing papers on "Spectrum analyzer published in 1998"

Automatic compensation of first order polarization mode dispersion in a 10 Gb/s transmission system

Abstract: We demonstrate a novel, adaptive optical polarization mode dispersion equalizer in a 10-Gb/s transmission experiment. The equalizer comprises a fast electrooptic polarization transformer an adjustable differential polarization delay line, and a simple electric distortion analyzer for automatic feedback control.

System and method for multiresolution scalable audio signal encoding

Abstract: An audio signal analyzer and encoder is based on a model that considers audio signals to be composed of deterministic or sinusoidal components, transient components representing the onset of notes or other events in an audio signal, and stochastic components. Deterministic components are represented as a series of overlapping sinusoidal waveforms. To generate the deterministic components, the input signal is divided into a set of frequency bands by a multi-complementary filter bank. The frequency band signals are oversampled so as to suppress cross-band aliasing energy in each band. Each frequency band is analyzed and encoded as a set of spectral components using a windowing time frame whose length is inversely proportional to the frequency range in that band. Low frequency bands are encoded using longer time frames than higher frequency bands. Transient components are represented by parameters denoting sinusoidal shaped waveforms produced when the transient components are transformed into a real valued frequency domain waveform. Stochastic or noise components are represented as a series of spectral envelopes. The parameters representing the three signal components compose a stream of compressed encoded audio data that can be further compressed so as to meet a specified transmission bandwidth limit by the deleting the least significant bits of quantized parameter values, reducing the update rates of parameters, and/or deleting the parameters used to encode higher frequency bands until the bandwidth of the compressed audio data meets the bandwidth requirement. Signal quality degrades in a graduated manner with successive reductions in the transmitted data rate.

Particle Charge Distribution Measurement for Commonly Generated Laboratory Aerosols

Abstract: An improved particle charge analyzer system has been developed to measure the absolute charge distribution of common generated laboratory aerosols. The charge analyzer system consists of an integral cylindrical mobility analyzer used in conjunction with an optical aerosol spectrometer, with computer assisted operation and data reduction. The charge analyzer collects aerosol particles over an absolute electrical mobility range from 4.2*10−4 to 400 cm2/(stat · Volt second) and flow rates that can vary from 0.3 to 30 liters per minute. The charge analyzer has been used to investigate the nature of spray and contact electrification during aerosol generation by measuring the residual charge distribution on the liquid and solid generated particles. In addition, the neutralization of charged particles by bipolar ions also was studied using conventional neutralizers that use ionizing radiation from alpha and beta sources. Charge distribution measurements were performed on alumina dust (Al), Arizona road ...

High-resolution electron time-of-flight apparatus for the soft x-ray region

Abstract: A gas-phase time-of-flight (TOF) apparatus, capable of supporting as many as six electron-TOF analyzers viewing the same interaction region, has been developed to measure energy- and angle-resolved electrons with kinetic energies up to 5 keV. Each analyzer includes a newly designed lens system that can retard electrons to about 2% of their initial kinetic energy without significant loss of transmission; the analyzers can thus achieve a resolving power (E/ΔE) greater than 104 over a wide kinetic-energy range. Such high resolving power is comparable to the photon energy resolution of state-of-the-art synchrotron–radiation beamlines in the soft x-ray range, opening the TOF technique to numerous high-resolution applications. In addition, the angular placement of the analyzers, by design, permits detailed studies of nondipolar angular distribution effects in gas-phase photoemission.

Nine-crystal multianalyzer stage for high-resolution powder diffraction between 6 keV and 40 keV

Abstract: For powder diffraction, high resolution can be best achieved using the parallel beam geometry with a monochromator/analyzer combination. However experiments are long and a way to reduce this time without compromising resolution is to use several analyzer/ detector combinations mounted on a single (theta) a/2(theta) a goniometer. We have developed such a solution for the 'Powder Diffraction' BM16-ESRF beam line. This device comprises nine analyzer/detectors, with a fixed prealigned offset of two degrees between adjacent analyzer crystals, and can be used in the whole energy range of the powder diffraction instrument (from 6 to 40 keV). The only required adjustment is the classical (theta) a/2(theta) a rotation of the supporting goniometer when the wavelength is changed. Moreover, the detector array can be used in the Debye Scherrer geometry without dismounting the multi-analyzer stage, only by positioning the goniometer at an ad-hoc (theta) a/2(theta) a angle, and inserting slits in front of the detectors. This multi-analyzer system is mainly dedicated to high resolution experiments and a peak width (FWHM) of 0.006 degrees in 2(Theta) has been achieved with a Si(111) monochromator on the BM16 ESRF beam line. Since the prealigned offset is small (2 degrees), the measuring time can be considerably reduced even for scans of small angular ranges, for high energy experiments or for high resolution in-situ studies. This set-up has also been used for anomalous diffraction studies and experiments on amorphous compounds, where it provides efficient elimination of fluorescence scattering and background from ancillary equipment. This system is in operation on the ESRF powder diffraction BM16 beam line since 1996 and has been extensively used for more than 90% of the beam time.

Self-powered network access point

Abstract: A system for providing operational power to network access points includes a router having an external power supply to transmit network signals to the network access points Each self-powered access point includes power extraction circuitry for extracting power from the network signals and a power storage subsystem for storing the extracted power Signal conversion circuitry is connected to the power storage subsystem for receiving operating power to perform signal conversion of received network signals addressed to a computer and to reconfigure data received from the computer for transmission over the network In a preferred embodiment, the power extraction circuitry includes a full-power extraction mode and a partial power extraction mode A data analyzer monitors received network signals to determine whether the signals are required by the computer for processing If a signal is required for processing, the data analyzer enables the partial power extraction mode in the power extraction circuitry to preserve a minimum signal power required by the computer for signal processing If the signal is not required for processing, the data analyzer enables the full power extraction mode to extract substantially all power from the signal Power level detection circuitry determines whether the power storage subsystem stores a minimum power level If a power level below the minimum is detected, the power level detection circuitry disables the data analyzer and enables the full power extraction mode of the power extraction circuitry until the minimum power is achieved, at which time the data analyzer is re-enabled

Apparatus for waveform disturbance monitoring for an electric power system

Abstract: A monitor/analyzer for an alternating current (AC) electrical system responds to power line disturbances by generating a trigger signal when a change in voltage with respect to time electrical parameter is greater than a programmed threshold. The monitor/analyzer includes a sensor for sensing an AC waveform in the electrical system, an analog-to-digital converter for sampling the AC waveform, and a microcomputer. Firmware of the microcomputer cooperates with the A/D converter and provides a plurality of digital samples of the AC waveform for each of some of its AC cycles. The firmware generates each of plural dV/dt parameters of the AC waveform from a corresponding adjacent pair of the digital samples within one of the waveform's AC cycles. A trigger signal is generated when one of the dV/dt parameters is greater than the programmed threshold. The digital samples of the AC waveform before and after the power line disturbance are captured and output to a display in response to the trigger signal.

Modeling of direct detection Doppler wind lidar. II. The fringe imaging technique

Abstract: A simple analytic model is developed for the shot-noise-limited measurement precision of Doppler wind lidars based on the fringe imaging technique by use of either molecular or aerosol atmospheric backscatter. The model leads to etalon design parameters for an instrument optimized for precision. The ultimate measurement precision possible is two to four times the limit for a perfect, lossless receiver. The corresponding result for the double-edge Doppler analyzer was a ratio of 2.5, showing that the two methods are little different in this respect. For aerosol backscatter instruments, the wind speed dynamic range of the fringe imager is substantially greater than that for the edge detector. The etalon aperture needed to meet system etendue requirements is derived and shown to be approximately half that of each of the two etalons required by the double-edge technique. A comparison with more detailed modeling of fringe imaging Doppler-shift analyzers shows good agreement for the Rayleigh model and fair for the aerosol version, confirming the validity of this simpler technique for analyzer design and performance prediction.

Indoor and outdoor frequency measurements for MM-waves in the range of 60 GHz

Abstract: Using a spectrum analyzer and synthesized signal generator, several measurements for the frequency-domain characterization of the radio channel in the 60 GHz band were performed. In the experiments, a carrier wave (CW) was swept with a constant amplitude across the 100 MHz band, centered around 59.9 GHz. The channel frequency response was measured at the receiver side. The results can be used for the design of an OFDM (orthogonal frequency division multiplex) system. The measurement environments were a corridor and a big college room in a high-rise office building (indoor) and a parking site and a grassfield at the side of that building (outdoor). The spectrum samples were taken in each of the environments. From such samples, it is possible to calculate the Rice parameter k and the path loss coefficients. It was necessary to the develop an appropriate measurement analysis, stemming from the fact that the spectrum analyzer gives no information on the phase, only amplitude. Measurement analysis method and results are explained.

Real time signal analyzer

Abstract: A real time signal analyzer capable of generating time region data and frequency region data at substantially the same time, and resetting a central frequency and a signal analysis range, the analyzer being provided with frequency conversion means (14, 16) for frequency-shifting input time region data and carrying out a thinning-out operation, an FFT processor (18) adapted to FFT-compute output data from the frequency conversion means in real time, a delay means (28) for delaying the output data from the frequency conversion means, a means (32) for storing the frequency region data from the FFT processor, a means (36) for storing the time region delay data read out from the delay means, and means (30, 38) for feeding back the data read out from the time region data storage means, instead of the input time region data, to the frequency conversion means.

Parallel processing in a vibration analyzer

Abstract: A portable data collector and analyzer having multiple paths for performing multiple processing functions on a single sensor signal in parallel. The portable data collector has a sensor which creates a sensor signal that represents a measured property of an operating machine. The sensor signal is simultaneously sent to at least two processor channels that are connected in parallel. Each processor is capable of performing different types of signal analysis with varying signal conditioning and sampling rate requirements on the sensor signal independent of the other processor(s). An operator of the parallel processing data collector and analyzer places the single sensor on the area desired to be tested and instructs the parallel processing data collector to begin taking measurements. The parallel processor channels work independently of each other to obtain results corresponding to a number of different tests in approximately the time normally required to perform a single test.

Method and apparatus for joint timing synchronization and frequency offset estimation

Abstract: A burst analyzer is useful in a digital communication system in which a signal burst has a plurality of reference segments distributed within the signal burst for transmission of a plurality of reference signals. The burst analyzer includes a filter that compares the received signal, for each reference segment thereof, with each reference signal offset by one of a plurality of time offsets to generate correlation data. The burst analyzer then determines, for each reference segment of the signal burst, a maximum correlation value from the correlation data for each time offset. Then the burst analyzer determines the time offset at which a sum of the maximum correlation values, over the plurality of reference segments, is a maximum. The burst analyzer jointly generates a frequency domain representation of the correlation data associated with the time offset at which the maximum correlation sum is a maximum, and then determines a frequency at which the frequency domain representation is a maximum.

A new toroidal electrostatic analyzer and application to surface analysis

Abstract: A new toroidal electrostatic analyzer (ESA) configuration for medium energy ion scattering has been designed and fabricated for structural analysis of surfaces. The present analyzer has a wide interelectrode distance of 16 mm and an energy range of 10% of the pass energy at a constant applied voltage. The analyzer is mounted horizontally on a turntable and accepts ions scattered within a well defined angular range. To get a good energy resolution, we employed a photon-counting image acquisition system (PIAS: Hamamatsu Photonics) with spatial resolution of 40–50 μm, combined with a three-stage microchannel plate. The electric fields of the toroidal ESA including the fringing fields were calculated by a finite element method. Ion trajectories through the analyzer were calculated using a Monte Carlo method. In this way, the optimum conditions of the geometry and size of the entrance and exit slits were determined. Our toroidal analyzer resolved three surface peaks from the Si isotopes (28Si, 29Si, and 30Si) clearly in the aligned spectra from H-terminated Si(001) and Si(111) and the energy resolution (ΔE/E) was estimated to be about 1×10−3. We describe the notable features of the new setup of the toroidal analyzer and show direct detection of H on Si(001) and Si(111) as a typical application.

Calibration and verification of the pure-mode vector network analyzer

Abstract: In this paper, the calibration of a pure-mode vector network analyzer (PMVNA) is presented in detail. The analyzer is intended for the measurement of mixed-mode scattering parameters (s-parameters) of differential circuits, but is also suitable for measurement of general microwave networks with up to four ports. The theory of calibration of the analyzer is developed in terms of a general n-port analyzer, including the correction of port-to-port crosstalk. The type of the standards used in calibration is examined, and the minimum number of standards are summarized for various levels of crosstalk correction. A new standard for all multiport network analyzer calibrations is introduced. A calibration is performed from 0.25 to 25.25 GHz based on standards with coaxial connectors, and verification standards are measured. The measured data is compared with National Institute of Standards and Technology (NIST) traceable measurements, and errors are found to be generally less than /spl plusmn/1 dB in transmission. In many cases, the error is less than the uncertainty of the NIST traceable measurements.

Motor stator condition analyzer

Abstract: A motor performance analyzer senses currents and voltages applied to the motor, converts the sensed signals to digital data signals, and stores the digital data signals. The analyzer includes a processor for evaluating the digital data and a display for alerting a user or technician to potential winding faults. Advanced signal processing techniques are used to further evaluate stored data and to provide trending information.

Two port handheld vector network analyzer with frequency monitor mode

Abstract: A two port handheld VNA enabling both reflection and transmission measurements to be made over a range of 25 MHz to 3.3 GHz frequency range. The handheld VNA includes a tracking synthesizer (420) which generates an LO signal without a direct connection to a reference oscillator (440), enabling resolution of the LO signal to be independent of a generated RF test signal. Synchronous detectors (501-505, 574, 575) are further included to provide incident, reflected, and transmitted IF signals to an A/D converter (548). To enable operation in the presence of external signals, a feedback dither line is provided from one of the synchronous detector (533) outputs to sweep the frequency of the reference oscillator (440). The handheld VNA also is configured to optionally operate as a frequency monitor to determine the frequency range and power level of incoming signals without upconverting and downconverting to eliminate images as typically done in a spectrum analyzer. The frequency monitoring circuit operates by dividing the frequency range to be monitored into bins. The LO signal is then stepped for each bin until RF signals within the bin frequency range can generate an IF signal. The maximum IF signal power level detected during measurements for the bin is then stored as a power level for signals in each bin.

Single channel apparatus for on-line monitoring of three-phase AC motor stator electrical faults

Abstract: An on-line monitor for electrical faults in the stator of an ac motor has a single di/dt current transformer or three separate di/dt current transformers coupled to the three phase conductors of the ac supply. The windings of the transformer, or transformers, are selected to generate a single sensed signal containing a linear combination of components of current in the three phase conductors weighted relatively so that algebraic differences between components from any two phase conductors is non-zero, such as preferably 2A+B-C or 3A+2B+C. The single sensed current signal is bandpass filtered to generate a pulse signal which is applied to an analyzer. The analyzer, preferably implemented by a microcontroller, generates an output based upon a combination of the amplitude and frequency of occurrence of the current pulse signal including a time attenuated accumulation of the pulses. A similar pulse signal is generated from a single sensed voltage signal and compared to the pulse signal generated from the current sensor to verify that the detected events originate in the motor and not from upstream in the ac supply. The monitor is coupled to the phase conductors between the local disconnect switch and the motor, and preferably, is mounted in the disconnect housing.

A new method to characterize EMI filters

Abstract: The proposed filter characterization method makes it useful to predict EMI filter performance when the filter is used in a practical power supply. High frequency parasitic effects can also be predicted using this method. An impedance/gain-phase analyzer is needed for this approach.

Quadropole mass analyzer with linear ion trap

Abstract: The present invention describes a quadrupole mass analyzer with linear ion trap. The quadrupole mass analyzer functions in a dual-mode. A conventional transmission mode operates with external ionizer supplying ions to the quadrupole analyzer. In an ion trap mode, DC endcap electrodes are attached to the rf quadrupole cylinder to form a trapping chamber where ions are confined. The preferred mode is based on a segmented cylinder electrode geometry which produces a substantially quadrupolar field distribution as used in a conventional four-rod quadrupole mass analyzer. Electrodes are generated from a cylinder that has been segmented along its length into some number of electrically isolated electrodes.

Optical spectrum analyzer having tunable interference filter

Abstract: An optical spectrum analyzer includes a polarization modifier that eliminates polarization-dependent wavelength spreading, enabling the analyzer to have high signal selectivity and high measurement sensitivity. The polarization modifier spatially separates orthogonal polarization components of the applied optical signal into separate optical beams and rotates the relative polarization components of the beams so that the beams are incident on a tunable interference filter in a multipass configuration at a single polarization state. The optical beams are directed through regions of the interference filter which lie on a contour of substantially equal center wavelength so that each of the multiple passes through the interference filter provides for corresponding narrowing of the filter bandwidth. Narrow bandwidth and low insertion loss are maintained over a wide tuning range by tilting the interference filter about a tilt axis intercepting the regions of the interference filter that lie on a contour of substantially equal optical thickness.

Method of and apparatus for predicting vehicle interior noise

Abstract: A jig is successively mounted on each of the four wheels of a vehicle. The jig is struck in three orthogonal directions independently, and at the same time, a microphone inside the vehicle measures the sound pressure of noise generated due to the exciting force. An FFT analyzer operates a frequency response function from the exciting force to the sound pressure. In a drum testing machine, a tire to be subject to noise prediction is mounted on a shaft, the tire is rotated, and the axial force in the three orthogonal directions is measured. The axial force signal is input to the FFT analyzer and the auto power spectrum in the three orthogonal directions and the cross power spectrum between two different axial directions are operated. The frequency response functions are synthesized with the auto power and cross power spectrums, and the power spectrum of the road noise is operated.

Method and apparatus for improved spatial light modulation

Abstract: A method and apparatus for modulating a light beam in an optical processing system is described. Preferably, an electrically-controlled polarizer unit and/or an analyzer unit are utilized in combination with a spatial light modulator and a controller. Preferably, the spatial light modulator comprises a pixelated birefringent medium such as a liquid crystal video display. The combination of the electrically controlled polarizer unit and analyzer unit make it simple and fast to reconfigure the modulation described by the Jones matrix of the spatial light modulator. A particular optical processing objective is provided to the controller. The controller performs calculations and supplies control signals to the polarizer unit, the analyzer unit, and the spatial light modulator in order to obtain the optical processing objective.

An intelligent FFT-analyzer

Abstract: An intelligent FFT analyzer capable of adapting its operating parameters on the basis of the signal spectrum was set up and characterized. The realized instrument is based on a parameter optimization procedure which provides the instrument with auto-configuration capability. It was implemented on a multiple processor DSP architecture in order to achieve real-time behavior. The experimental tests carried out on a large number of signals highlight the instrument capability of correctly detecting tones with a good frequency resolution whatever the signal spectrum type.

Display of spatial coherence.

Abstract: The mutual-intensity function plays a major role in characterizing quasi-monochromatic, partially coherent optical signals. We demonstrate an optical system for displaying the mutual intensity of a one-dimensional input beam. The experimental system is based on the fact that the mutual intensity of a signal can be expressed as the ensemble averaging of a cross-correlation operation between two related optical signals. The setup consists of a Sagnac interferometer followed by an optoelectronic joint transform correlator. Experimental results demonstrate the capabilities of the mutual-intensity analyzer.

16-channel (1- to 16-GHz) microwave spectrum analyzer device based on a phased array of GaAs/AlGaAs electro-optic waveguide delay lines

Abstract: We demonstrate a sixteen channel, GaAs/AlGaAs staring spectrum analyzer device based on a phased-array of sixteen electro-optic waveguide delay lines. The device is effectively a high resolution version of the widely reported optical wavelength division multiplexer phased-array devices, using electro-optic waveguides to adjust the optical phases across the array. The device comprises: a 1- to-16 way multimode interference coupler; 16 electro-optic phase controllers; 16 folded waveguide delay lines, from 0 to 1 nanosecond in equal steps; and a waveguide phased array output. By making use of novel waveguide and corner designs we demonstrate the device as a spectrum analyzer, the RF signal to be analyzed was superimposed on an optical carrier using a GaAs/AlGaAs electro-optic waveguide push-pull Mach Zehnder interferometer, and the intensity modulated light was then passed through the phased-array chip. The spectrum of the RF input signal was displayed in the far field of the phased-array as diffraction lines on either side of the main diffraction lines. By biasing the modulator to extinction, the CW carrier could be removed from the far field diffraction pattern so that only the RF spectrum was displayed. In this presentation we describe the device design, fabrication and testing including measurements of the dynamic range and resolution.

A multi-detector system for a triple-axis spectrometer

Abstract: Until now there have been only a few attempts to use many scattering angles simultaneously in triple-axis spectrometry with neutrons. We present a novel Multi-Analyzer Detector (MAD) unit for a Triple-Axis Spectrometer (TAS) set up at the Forschungsreaktor Munchen (FRM). The layout is based on the principle of monochromatic defocusing. Up to 61 analyzers are mounted around the sample in the constant final energy mode. This arrangement supplies the flexibility of a TAS with a multi-channel analyzer capacity similar to a Time-of-Flight Spectrometer. The gain in measurement time can be more than an order of magnitude.

Infrared, multiple gas analyzer and methods for gas analysis

Abstract: A portable, infrared, multiple gas analyzer for measuring the concentration of a plurality of infrared absorbent gases with a simple optical arrangement for transmitting an infrared beam along an optical path along with gas mixtures to be analyzed. Light transmitting tubes arranged in a U-like configuration transmit infrared energy and the gases applied thereto over a small path to an infrared detector from an infrared source and provide electrical analog output signals representative of the detected gases. The detector output signals are processed by D.C. processing circuits including an analog to digital converter and microprocessing circuits for providing digital, binary coded, output signals representative of the detected gas concentration of the infrared absorbent gases. The analyzer can be readily calibrated by applying a non-infrared absorbent gas to the gas analyzer to provide a maximum output signal level with the infrared beam on and the background level or dark level signal with the beam off. The gas mixture having the infrared absorbent gases to be measured are applied to the analyzer for measurement and the resulting analog signals are amplified under control of a microprocessor for determining whether or not a preselected signal level stored in the microprocessor memory is exceeded or not. If not, the gain of the amplifier is increased to compensate for the aging of the analyzer. An offset voltage is applied to the analog to digital converter under control of the microprocessor to the amplified gas signals for increasing the resolution of the converter output signals only during the time intervals the absorbent gases are being measured. The microprocessor is programmed to execute a program for calculating the detected concentration of the gases undergoing analysis based on the previously acquired and stored “zero” gas level, dark level and known gas factors to provide the desired digital, binary coded, gas concentration signal from the analyzer.

RF output spectrum measurement analyzer and method

Abstract: The present invention provides an RF spectrum measurement analyzer and method and more particularly to a GSM output RF spectrum measurement analyzer and corresponding method. One preferred embodiment of the present invention is applicable to GSM applications. However, other embodiments could be applicable to the general class of Time Division Multiple Access (TDMA) signals of which GSM, PDC (Pacific Digital Cellular), NADC and the like are a part. According to one preferred embodiment of the present invention, the method includes the steps of acquiring an RF carrier signal; converting the acquired RF carrier signal to an IF signal; converting the IF signal to a digital signal of relatively wide bandwidth; FFT filtering the digital signal to measure multiple offset frequencies within the IF bandwidth; and mathematically applying a resolution bandwidth filter at each offset. A further embodiment includes the steps of inverse FFT filtering the output of the resolution bandwidth filter and measuring the power in the time domain.

A PC-based vibration analyzer for condition monitoring of process machinery

Abstract: A fast-response PC-based vibration analyzer has been developed for fault detection and preventive maintenance of process machinery. The analyzer acquires multiple vibration signals with high resolution, and computes frequency spectra, root mean square amplitude, and other peak parameters of interest. Fast execution speed has been achieved by performing data acquisition and frequency spectrum computation using C-language. Vibration signals up to 10 kHz can be analyzed by the spectrum analyzer. Special algorithms, such as window smoothing, digital filtering, data archiving and graphic display have also been incorporated. With these features the vibration analyzer can perform most of the functions available in complex, stand-alone machines. The software for the analyzer is menu driven and user-friendly. The personal computer used is a 66 MHz PC-486 compatible machine. The use of a general purpose PC and standard programming language makes the vibration analyzer simple, economical, and adaptable to a variety of problems. The applications of the system in malfunction detection in rotating machinery are also described.