Frequency Sweep Range Research Articles

Wireless mobile communication device having a speaker vibration alert and method of using same

A mobile wireless communication device has a speaker that functions as a vibration alert in addition to an audio output device. The speaker is selected from a group of speakers having variation in mechanical vibration resonant frequency. A drive signal sweeps back and forth across a sweep frequency range including the varient speaker mechanical vibration resonant frequencies. The drive signal drives the speaker causing it to vibrate at the mechanical vibration resonant frequency and in turn causing the mobile wireless communication device to vibrate, thereby alerting the user. In this manner, the same drive signal can be used to vibrate each speaker at the speaker's mechanical vibration resonant frequency despite the variation in mechanical vibration resonant frequencies among the group of speakers.

Numerical Simulation of a lightwave synthesized frequency sweeper incorporating an optical SSB Modulator composed of four optical phase Modulators

We describe the numerical analysis of a lightwave synthesized frequency sweeper (LSFS) that uses an optical single-sideband (SSB) modulator composed of four optical phase modulators. The SSB modulator realizes a large frequency shift in the LSFS. This means that we can reduce the number of pulse circulations in the LSFS cavity to cover a given frequency sweep range. We propose a frequency-domain analysis method for the LSFS, in which a general optical modulator is expressed by using a matrix that includes optical phase terms. We employ this method to simulate the LSFS for several different phaseand group-velocity dispersion values in the lightpaths in the LSFS cavity. The results indicate that we can realize a linear frequency sweep by adjusting the phase change of the modulation signal during the cavity round-trip time.

Cross-coupling Properties of Ultrasonic Phased Array Probe

The frequency dependence of cross-coupling is described for a phased array probe developed for sector-scanning endoscopic ultrasonic diagnosis. The sweep frequency range is set from 0.5 MHz to 10.5 MHz for a 48-element phased array transducer with a center frequency of 5 MHz. Cross-coupling measurements were carried out on various piezoelectric elements at different positions in the probe. The relationship between the cross-coupling and the position of piezoelectric elements as determined by the measurements shows good agreement with the results of static-mode finite-element method (FEM) calculations.

Response selectivity for multiple dimensions of frequency sweeps in the pallid bat inferior colliculus

1. While hunting, the pallid bat uses passive sound localization at low frequencies to find terrestrial prey, and echolocation for general orientation. It must therefore process two different types of acoustic input at the same time. The pallid bat's echolocation pulse is a downward frequency-modulated (FM) sweep from 60 to 30 kHz. This study examined the response selectivity of single neurons in the pallid bat's central nucleus of the inferior colliculus (ICC) for FM sweeps, comparing the response properties of the high-frequency population, tuned to the biosonar pulse, with the low-frequency population, tuned below the pulse. The working hypothesis was that the high-frequency population would exhibit a response selectivity for downward FM sweeps that was not present in the low-frequency population. 2. Neurons were tested for their selectivity for FM sweep direction, duration, frequency range and bandwidth, and rate of frequency change. The extent to which they responded exclusively to tones, noise, and FM sweeps was also examined. Significant differences in the response properties of neurons in the two populations were found. In the low-frequency population, all neurons responded to tones, but only 50% responded to FM sweeps. Only 23% were selective for sweep direction. In the high-frequency population, all neurons responded to FM sweeps, but 31% did not respond to tones. Over one-half of this population was selective for sweep direction, and of those that were selective, all preferred the downward sweep direction of the biosonar pulse. A large percentage (31%) responded exclusively to downward sweeps, and not to tones or upward sweeps. None of the cells in either population responded to noise, or did so only at very high relative thresholds. 3. Both populations contained neurons that were selective for short stimulus durations that approximated the duration of the biosonar pulse, although the percentage was greater in the high-frequency population (58% vs. 20%). In the high-frequency population, 31% of the neurons tested for duration responded exclusively to both the sweep direction and duration of the biosonar pulse. 4. Downward FM-selective neurons, with one exception, were generally insensitive to the rate of frequency change of the FM sweep, as well as the frequency range and bandwidth of the sweep. They responded similarly to both the full 60- to 30-kHz sweep and to 5-kHz bandwidth portions of the full sweep.(ABSTRACT TRUNCATED AT 400 WORDS)

Discrete frequency sweeping of a semiconductor laser by temperature change and electrical feedback

AbstractIn a constant interval multifrequency measurement to evaluate optical device characteristics, considering that a constant time is required for the measurement at each frequency, a sweeping method that maintains the frequency during the measurement is desirable. Although this stepwise frequency sweeping can be achieved by changing the injection current of the semiconductor laser, the possible sweep frequency range is much wider for the temperature change than for the current change.In this paper, noting this wideband sweeping range by the temperature change, two frequency sweeping methods are proposed. In these methods, the frequency changes stepwise for the temperature change proportional to the time that is easy to realize, and are verified and compared experimentally. In this method, a part of the laser light is incident on the Fabry‐Perot resonator with the temperature change, and the transmitted light signal or its differential signal is fed back into the injection current. As a result, the feedback signal corresponding to the resonant characteristics controls the shift of the resonance frequency by the temperature change in the neighborhood of the resonance frequency, realizing the frequency sweep that changes stepwise with the spacing equal to the free spectral range of the Fabry‐Perot resonator.

Image reconstruction in optical frequency‐domain reflectometry by means of maximum entropy method—fourier transform combination

AbstractIn the optical frequency domain reflectometry (OFDR), if the Fourier transform is used for image reconstruction, degradation such as a spread of width in the image for an isolated reflection point occurs due to the fact that the frequency sweep range is finite and the sampling spacing is disturbed. On the other hand, it is known that the reflection position resolution can be improved in a nonlinear spectral estimation method such as the maximum entropy method, whereas it is difficult to measure the intensity of reflection.In this paper, a new image reconstruction method is proposed in which the position (distance) resolution is improved by the maximum entropy method while the spectral intensity is determined by the Fourier transform. The method is compared with the image reconstruction by the conventional Fourier transform. If “detection and measurement of several isolated reflection points” are the objective, the image degradation can substantially be alleviated and the location of reflection and reflection intensity can be measured accurately. Also, an optical reflectometer is constructed and experiments of reflection measurement are carried out so that the effectiveness of the proposed “combination method” is confirmed.

Novel chromatic dispersion measurement method over continuous Gigahertz tuning range

A method for the measurement of chromatic dispersion in a single-mode optical fiber is proposed and demonstrated. This method adopts the technique of external modulation of the distributed feedback (DFB) laser output and direct optical frequency sweep range monitoring by coherent heterodyne detection. The method is also applicable to the future optical communication system with narrowband optical elements such as optical amplifiers, whereas measurement is impossible given the present state of the art.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Chatter Growth—Tests to Evaluate the Theory

Tests were run on a 30-hp Mazak slant turn lathe machining Inconel 718 with a 883 grade tungsten carbide button insert. The purpose of the tests was to evaluate the regenerative chatter theory of reference 1 and the chatter sensor and adaptive control strategies it predicts. The cutting system’s mechanical response was measured by shaking it at constant force through the swept frequency range of 30 to 1000 Hz. From these tests and static stiffness tests, the system’s effective mass, damping, and stiffness were measured. Cutting force tests were run to measure the machining system’s cutting compliance. The results of the shake and cutting tests were substituted into the regenerative stability model to predict the machine’s chatter behavior. The theory was consistent with test observations.

A Comparison of Minimum Phase ‘Correlation’ and its Role in Seismic Data Misties

Minimum phase conversion is a common and often routine first step in the processing of zero phase correlated Vibroseis data. Over the period of March 1983 to December 1985 the Cooper Basin joint venturers used five different recording contractors and as many as nine different processing contractors. Many misties, due to apparent phase differences, were noted and a study was initiated to determine the cause of these. A data set was sent to seven different processing contractors and the results compared. Major differences appeared during the correlation and minimum phase conversion of the data. The degree of difference depended primarily on the contractor but was also affected by the choice of sweep parameters. The results of the study are presented in this paper. The minimum phase conversion operators are designed from the amplitude spectra of the Vibroseis pilot sweep. These differ from contractor to contractor due to the various levels of additive noise and base levelling of the amplitude spectrum outside the swept frequency range. The degree of phase rotation is dependent on the levels of noise and is not necessarily linear. Sweep non-linearity can also affect the minimum phase conversion procedure and the level of phase distortion caused by this is shown. A standardisation of the minimum phase conversion to avoid phase shifts between the various contractors was introduced by the Cooper Basin operators in 1986 and 1987.

Microwave reflectometry with the extraordinary mode on tokamaks: Determination of the electron density profile of Petula-B

The use of an ordinary mode reflectometer has already proved to be a good means for determining the density profile of a plasma, but the fact that this mode reflects where its frequency equals the local plasma frequency restricts its use to the region of the density gradient. The extraordinary mode reflectometry investigated here permits the observation of the scrape-off layer as well as the near-axis region and in certain conditions also the high magnetic field side of the density profile. It is also shown that this mode requires a range of frequency sweep for measuring a given density profile smaller than the ordinary mode. On the Petula-B tokamak, the density profile has been measured in 200 μs, its evolution when applying the lower hybrid current drive could be also followed. Since the measurement is particularly sensitive near the reflection point of the wave, it could be used to determine precisely the position of magnetic islands and the fluctuation amplitudes. In addition, the access and place occupied in the vacuum chamber being very small, this diagnostic should be compatible with reactor conditions.

Sound localization of frequency-modulated sinusoids by Old World monkeys

Directional hearing acuity, as measured by the minimum audible angle (MAA), was determined in four Old World monkeys, Macaca radiata. The acoustic stimuli were linear changes in frequency (sweeps) for different frequency ranges and sweep rates. The sweeps ranged between 0.5 and 1.3 kHz, at two durations, 100 and 200 ms. In upsweeps which began at 0.5 kHz and were 200 ms in duration, MAA decreased as sweep rate and frequency range increased. These thresholds were compared to MAAs of sweeps which traversed the same range of frequencies but at a different rate, to MAAs of sweeps with identical rates but over different frequency ranges, and to the MAAs of downsweeps. These comparisons indicated that range, and not sweep rate, exerts the greatest effect on the MAA. Interaural phase differences derived from the upper limits of the frequency range are discussed as potential FM localization cues.

Search for proton magnetic resonance in ferromagnetic Β-uranium hydride

Proton magnetic resonance (PMR) in a ferromagneticΒ-uranium hydride at 77 K has been searched unsuccessfully between 4 and 420 MHz. The present communication reports this experiment and its objectives, and justifies the swept frequency range on the basis of PMR data obtained in the paramagnetic phase and of a new analysis of the Flotow and Osborne low temperature specific heat data. It is shown that experimental conditions were at least as favourable as those for observing PMR in the paramagnetic phase. Specific heat measurements below 1 K, using the Dempesey et al. method, seem necessary before pushing experimental efforts further.

Discrimination of frequency‐modulated sounds by the frog Kassina senegalensis

Male South African running frogs (Kassina senegalensis) produce a pronounced frequency modulated (FM) mating call during the breeding season which serves to attract conspecific females. The call typically sweeps upward from 750 to 2250 Hz in 140 ms. Behavioral phonotaxis studies were conducted with 73 female frogs. Results from 475 two‐choice playback discrimination trials, using natural and synthetic mating calls, verify that females can readily discriminate among a variety of FM signals based on sweep direction, duration, rate, and frequency range. Concomitant electrophysiological results indicate that these animals afford an opportune model for neurobehavioral studies of encoding of FM sounds in the vertebrate peripheral and central auditory system. [Work supported by N. I. H. Grant NS‐09244, South African Council for Scientific and Industrial Research, and Animal Communication Research Program, University of the Witwatersrand.]

Baseband frequency response measurement system for optical components

Knowledge of the baseband frequency responses of optical components is prerequisite to the design of optical fiber transmission systems. The sweep-frequency method is effective for obtaining frequency responses because of its large SNR. However, the use of GaAs lasers as optical signal sources involves several problems such as resonances below 1 GHz and spectrum broadening. In order to overcome these problems, a single transverse mode GaAs laser called a buried heterostructure GaAs laser was employed as an optical signal source in the sweep-frequency measurement system. This measurement system has a wideband flat sweep-frequency range of 0.5-1300 MHz as well as a wide dynamic range of more than 60 dB at optical levels.

Coding and processing in the auditory systems of FM-signal-producing bats.

For echolocation, many species of bats emit frequency-modulated (FM) sounds. When the central gray matter or reticular formation in the midbrain is electrically stimulated, these bats produce FM sounds similar to FM-orientation signals. The auditory system is excited by these emitted sounds, but the responses of auditory neurons in the midbrain are attenuated by a neural mechanism operating synchronously with vocalization. This neural attenuating mechanism is present between the auditory nerve and the inferior colliculus and may be a part of mechanisms for effective echo-detection. Among the various orientation sounds emitted by bats, FM sounds are the most suited for echo-ranging. In the lateral lemniscus, the majority of neurons show a very short recovery period, as well as frequent facilitation of their responses to a second tone pulse, so that these neurons are specialized for echo-detection and carry information necessary for echolocation. In the inferior colliculus, single neurons exhibit a broad spectrum of recovery cycles, so that these are probably able to scale echoes from different distances for the distance measurement. Neural-network models of a clock for echo-ranging are discussed. In the inferior colliculus and the auditory cortex, there exist neurons specialized for processing FM signals. For the excitation of these FM-specialized neurons, the direction, range, and speed of frequency sweep are important factors. The FM-specialized neurons always have a large inhibitory area and respond to FM sounds sweeping across this area. Although seemingly paradoxical, such properties are easily explained by neural-network models. Orientation sounds of several species of bats consist of constant frequency (CF) and FM components. Neurons specialized for the analysis of CF sounds have inhibitory areas on both sides of a very narrow excitatory area. The responses of the FM-specialized neurons to certain FM sounds in the presence of either FM or CF sounds are discussed in relation to the inhibitory area.

Coding and Processing in the Nervous Systems of FM-Signal-Producing Bats

For echolocation, certain insectivorous bats emit frequency-modulated (FM) sounds in which frequency always sweeps from high to low. Neurons in the cochlear nerve and nucleus respond to various types of sounds, such as pure tones, FM sounds, and noise bursts, and are therefore not specialized for the analysis of the bat's orientation sounds. In the inferior colliculus and auditory cortex, however, there exist neurons which selectively respond to FM sounds. For the excitation of these FM-specialized neurons, the direction, range, and speed of frequency sweep are important factors. The FM-specialized neurons always have a large inhibitory area and respond to FM sounds sweeping across this area. Although seemingly paradoxical, such properties are easily explained by neural network models. Bats emit short FM sounds when certain parts of the brain are stimulated with electric pulses. The temporal pattern of emission differs according to the location of the stimulating electrodes. Many neurons in the lateral lemniscus and inferior colliculus are excited by the bat's own outgoing sounds, in spite of the contraction of the middle ear muscles, synchronized with sound emission. The lateral lemniscal neurons appear to be specialized for echo detection because of the facilitation of their responses to a second tone pulse (artificial echo), while the inferior collicular neurons appear to be specialized for echo ranging because they exhibit various types of recovery cycles, including temporary recovery. [Supported by grant GB-13904 and PIB-2103 from the N.S.F. and grant HSAA 53837 from the P.H.S.]

An Accurate Delay-Time Measuring Equipment in the 50-GHz Region

An accurate delay-time measuring equipment operating in the 50-GHz region has been developed. The equipment can measure wide-band delay-time characteristics of millimeter wave component and waveguide line. Sweep frequency range is variable from 0 to 1.5 GHz at any of the 46 to 52 GHz. The measurement method employs the usual comparison method and a newly developed rapid automatic switching method. The accuracy of the equipment is 0.1 ns at 20-dB insertion loss. Finally, some measured results are described.

Frequency Glides—Their Spectra and Pitch Perception

The spectra of tone bursts with linearly changing frequency as calculated on the LINC computer are shown. The conditions for which different numbers of maxima occur in the spectrum are compared with some results of measurement of perception of pitch of such acoustic bursts. Those spectra that contain only one or two peaks correspond to tone bursts likely to be evaluated as having one quite distinct pitch. When the spectra show many maxima, the corresponding pitch character of the burst becomes less clear and the matched frequencies may be spread over the whole swept frequency range or are equal to the final frequency.

A New Type Spectrometer for Nuclear Magnetic Resonance Dispersion Using Gated Beam Tube

A new type of nuclear magnetic resonance dispersion spectrometer using a gated beam tube is described. The characteristic feature of this spectrometer is its low noise figure of about three at the comparatively high r.f. level of 4 V. This new spectrometer is much easier to be used than an r.f. bridge because there is no delicate balance adjustment and it is free from any balance drifting. An r.f. amplifier and a detector are no longer necessary because of the amplification and detecting properties of the gated beam tube and it is possible to sweep the frequency simply by sweeping the signal generator. The frequency sweep range is about 200 Kc/sec without any adjustment of the spectrometer.

An electroluminescent-piezoelectric flat-panel display device

A flat-panel, line display consisting of electroluminescent ZnSCu phosphors (EL) adjacent to piezoelectric voltage transformer elements (PE) has been fabricated to provide a controlled-movement luminescent light spot. Electroluminescence is excited by the electric fields generated at the surface of a piezoelectric element driven at its resonant frequency. The display is made up of thirty PE-EL units connected electrically in parallel, each unit resonating at a different frequency. Movement of the light spot over the face of the display is produced by frequency modulation of the voltages applied to the piezoelectric array, in the manner of a sweep frequency. Synchronized amplitude modulation permits the light spot to be localized and its movement to be controlled. The display has a sweep frequency range extending from 30 to 60 kc/s. PE-EL units under continuous operation generate 40 ft lamberts at 8·8 V rms, and can generate over 100 ft lamberts by overdriving at 40V rms. In sweep operation at 100 c/s, the light output is 40 ft lamberts at 35 V rms. Power consumption in this mode is less than 10 mW. EL fatigue is analyzed and minimized in this display sweep technique.