Showing papers on "Fundamental frequency published in 1982"

A systematic study of ULF Waves Above FH+ from GEOS 1 and 2 Measurements and Their Relationships with proton ring distributions

Abstract: A detailed analysis of the ULF noise observed on the GEOS magnetic antennas in the frequency range ∼0.2'12 Hz has revealed the properties of structured emissions occurring just above the proton gyrofrequency whose existence was reported by Russell et al. (1970) and Gurnett (1976). These waves are observed in the vicinity of the geomagnetic equator at all L values between ∼4 and ∼8. They propagate in a direction perpendicular to the dc magnetic field. The waves consist of harmonically related monochromatic emissions. The fundamental frequency is generally of the order of the local proton gyrofrequency. Sometimes the fundamental and first harmonics are missing. If there is more than one fundamental frequency present, nonlinear coupling often occurs between the different emissions. The amplitudes of individual events vary from some tens of milligammas to some hundreds. Their duration ranges from some tens of minutes to some hours. Within the range of sensitivity of the detectors (10−2 γ Hz−1/2 at 1 Hz, 10−3 γ Hz−1/2) at 8 Hz the average probability of emission occurrence during a given hour is 12%, this number increases to ∼30% during the afternoon and in the pre-midnight sectors. Simultaneous observations of proton fluxes, as obtained from the two GEOS particle experiments show that these waves are often associated with distribution functions peaking at some energy (5 ≲ E ≲ 30 keV) for 90° pitch angle particles. This ring-like distribution provides the energy source for the excitation of non-resonant (k∥ = 0) instabilities near nFH+ (n = running number). A theoretical model is presented that qualitatively explains the main characteristics of the observed waves.

Fundamental Frequency and Discourse Structure

Abstract: The height of clause-peak fundamental frequency (normalized across speakers) was taken as the physical correlate of an observer's global impression of the relative pitch height of utterances embedd...

Comparison of pitch detection by cepstrum and spectral comb analysis

Abstract: Most reliable methods of detecting pitch in the speech signal are based on the assumed periodicity found in the voiced speech spectrum (cf. the cepstrum method). Due to recent hardware developments, this approach is becoming more attractive since the prerequired harmonic analysis can now be easily performed in real time. The spectral comb correlation, a new method based on spectral analysis, was recently introduced (5). Rather than performing a second spectral analysis on the log power spectrum, this approach relies on the correlation between the power spectrum and a spectral comb with "teeth" of decreasing amplitude and variable teeth intervals. The maximum of this correlation function is obtained when the width of the teeth intervals corresponds to the periodicity of the spectrum. The spectral comb method is compared to the cepstrum on both theoretical and experimental levels. It is shown in particular that the comb method is computationally more efficient, gives a better fundamental frequency resolution, and can use smaller duration windows for the initial spectral analysis.

Single-Gate MESFET Frequency Doublers

Abstract: A simple analytic model of the FET frequency doubler is used to determine the relative contributions of the various nonlinearities to harmonic generation. FET doubler conversion gain and its variation with frequency relative to the fundamental frequency available gain is also estimated. Large-signal computer simulations are used to determine the validity of the analytic model and provide further information on conversion gain and its frequency dependence. The analytic and computer predictions are compared with experimental measurements on a 4- to 8-GHz single-gate FET frequency doubler.

Nonlinearity detection using fault-generated second harmonic

Abstract: The tester and method for nondestructively detecting nonlinearity faults in conductors includes the application of a composite AC and DC drive signal to the device under test in such manner that nonlinearities in the device under test produce fault signals including second harmonics, due to local changes of resistance caused by ohmic heating. Electronic filters are used to select out and amplify the second harmonic only, eliminating the direct current and fundamental frequency components of the initial test pulse, plus third and subsequent harmonics. The filtered second harmonic signals from the device under test are then phase-compared to a phase-shifted second harmonic signal produced by a frequency doubler from the test signal generator oscillator to cancel out the second harmonic signals from the good conductor; the remaining phase anomaly signals control a threshold detector remaining to provide fault indication.

System to independently modify excitation and/Or spectrum of speech waveform without explicit pitch extraction

Abstract: A new speech analysis/synthesis system is described which is capable of independent manipulation of the fundamental frequency and spectral envelope of a speech waveform. The system deconvolves the original speech with the spectral envelope estimate to obtain a model for the excitation. Hence, explicit pitch extraction is not required. As a consequence, the transformed speech is more natural sounding than would be the case if the excitation were modeled as a sequence of pulses during voiced segments or pseudorandom noise during unvoiced segments. The system has applications in the areas of voice modification, baseband-excited vocoders, time-scale modification, and frequency compression as an aid to the partially deaf.

Harmonic mixing in a cosine potential for large damping and arbitrary field strengths

Abstract: A complete numerical treatment is given for the dc harmonic mixing signal of two ac electric fields of frequences ω and 2ω. Mixing occurs due to a charged Brownian particle in a cosine pinning potential. Nonlinear responses to pinning potential strength as well as to ac field strengths are computed using the method of matrix continued fraction expansion within a Smoluchowski treatment. Relevant ranges of all the parameters of the model are considered, i.e. strength of pinning potential, fundamental frequency, the two ac field strengths as well as temperature and the phase relation between the exciting fields. It is found that strong deviations from the predictions of cubic response theory occur at scaling field strengths sufficient to give the charge an energy gain ofkBT when it traverses one potential trough. For even larger field strengths the harmonic mixing signal falls off rapidly. Higher order than cubic responses also show up in a peculiar dependence of the mixing signal on the phase angle between the ac fields.

H-Switch start-up control for AC motor

Abstract: A start-up control technique is disclosed for an AC motor. At least one H-switch connects a motor winding to a pair of AC-supplied power lines and is switched between designated states to yield a fundamental frequency component voltage waveform in the winding phase shifted from the voltage waveform in another winding. A rotating field is provided for start-up, without energy-storage phasing capacitors or inductors.

Generation of higher harmonics in a self-oscillating mixing layer-wedge system

Abstract: The unsteady upstream influence associated with insertion of an impingement wedge in an unstable mixing layer is shown to enhance the coherence at the fundamental frequency of vortex formation, and to produce welldefined higher harmonics in a manner strikingly similar to artificial excitation of the corresponding nonimpinging flow. Each of the higher harmonic components grows at a rate 1.6 times that of the fundamental component, agreeing well with strong nonlinear interaction theory. Furthermore, assuming a state of quasiamplitude equilibrium at each streamwise station, the absolute value of each of the higher harmonic components was obtained from the Stuart perturbation model; the first harmonic amplitudes agree well with predicted values. At amplitude equilibrium, there is also very favorable agreement. Finally, a spectral analysis of the unsteady velocity expression of the Stuart model allowed comparison of measured and predicted velocity spectra; there is good agreement in both amplitude and shape of the spectra away from the center (y0f5) of the shear layer.

Optimal Grillage Layout for Given Natural Frequency

Abstract: The problem of minimizing the volume of structural material of an elastic grillage subject to a prescribed value or the fundamental frequency of free transverse vibrations, is considered. The domain and the boundary conditions are given, and the grillage is equipped with a specified, distributed non-structural mass, which is large in comparison with the structural mass. It is the objective to determine the optimal layout of the grillage, and to optimize the beams, which are of given depth and varying width. It is shown that the optimal grillage layout is the same as that found earlier for three different types of design problems, namely plastic design for given collapse load, elastic design for given permissible stress, and elastic design for given compliance. An an example, a simply supported, square grillage with uniformly distributed mass loading is optimized, and it is shown that the amount of structural material of the optimal grillage is significantly smaller than that to be used for a uniform plate with the same fundamental natural frequency of transverse vibrations.

Synthesized sine-wave static generator

Abstract: An inverter bridge provided with a series-network in its diagonal including an inductor and an output transformer is feedback-controlled to generate a sine wave by reference to a sine wave reference signal and in a self-oscillatory fashion of the "bang-hang" type. The series-network operates during the "hang" phase as an active filter. Transistors are used on the high frequency side of the bridge and thyristors are used on the fundamental frequency side of the bridge. Provision is made for an AC source in parallel with the load, in which case feedback control is in response to the relative shares of the sources in the common load.

Push-pull microwave oscillator with fundamental and second harmonic outputs

Abstract: A push-pull microwave oscillator circuit, including two transistors, for producing the second harmonic of a fundamental frequency at a symmetry point of the circuit which is connected to the bases of the transistors through identical arrangements of circuit elements. The circuit includes tuning means coupled to at least one of the transistors, an output and an input. The output, which is utilized to provide to a phase comparison means an output signal at the fundamental of the second harmonic frequency, is coupled to the base of at least one of the transistors by a capacitive impedance. The input, which is utilized to receive a tuning signal produced by the phase comparison means in response to the output signal, is coupled to the tuning means.

Signal processing apparatus for frequency domain geophysical electromagnetic surveying system

Abstract: A frequency domain geophysical electromagnetic surveying system is provided in which intermittent primary fields having sharp terminations are generated in a cycle having a fundamental frequency by a transmitter, and a receiver includes a gate passing only secondary signals received during interruptions of the primary field, the gated signal being applied to filters tuned to harmonics of the predetermined frequency. The filter outputs are synchronously demodulated to provide signals corresponding to at least the in-phase component of the secondary signal at the fundamental frequency, and preferably in-phase and quadrature components at at least two harmonics. The system can provide improved resolution particularly of the characteristics of in-phase secondary signals received from terrain being surveyed.

Comparative performance of pitch detection algorithms on dysphonic voices

Abstract: Current pitch detection algorithms run into difficulties when used on dysphonic voices. Two major sources of difficulty are the presence in the phonatory output of frictional, non-harmonic energy (in whispery voices), and microperturbatory fundamental frequency jitter and amplitude shimmer (in harsh and creaky voices). For adequate performance on dysphonic voices, pitch detection algorithms should have the following characteristics: 1. work on acoustic recordings from men, women and children 2. be noise resistant 3. work on continuous speech. Measures of pitch perturbation are defined. Three pitch detection algorithms were applied to the speech of dysphonic speakers as well as a control group of speakers. Two detectors work in the time domain (simplified inverse filter tracking (1) and a parallel processing method (2)), and one in the frequency domain (cepstral pitch detection (3)), Their comparative performance on perceptually rated clinical material is discussed.

Method and apparatus measuring absolute rotation

Abstract: Method for measuring absolute rotation with the aid of a light conductive fiber ring interferometer including a light source, a beam dividing arrangement, a light path formed by a light conductive fiber coil, an optical phase modulator which is disposed in the light path and which modulates the light circulating in the light path with a periodic, optical phase modulation at a fundamental frequency f 0 , and a photodetector for providing an electrical output signal. The light circulating in the light path or an electrical output signal from the photodetector is modulated with at least one mixing frequency f 2 in a manner such that an electrical evaluation signal results which has an evaluation frequency f 1 which is smaller than that of the fundamental frequency f 0 and which is evaluated to determine the absolute rotation of interest.

High power resonance filters

Abstract: There is provided by this invention a novel high power resonance filter utilizing a resistive element between two resonant branches disposed to dampen resonant harmonic currents or voltages while maintaining minimal losses at the fundamental frequency.

Bridge-type frequency multiplier

Abstract: An AC frequency conversion technique is disclosed using an H-switch toggled at irregular times to yield a chopped sinusoid output waveform of a given fundamental frequency. The irregular switching pattern is a departure from the classical cycloconverter frequency conversion approach. The H-switch is connected between a pair of power lines L1 and L1 and alternately switched between one and another ON state at any point in the AC cycle to yield any up-converted or down-converted output frequency of the chopped sinusoid output waveform. The output waveform has a positive half cycle during which the H-switch is in one ON state when L1 is positive with respect to L2 and is in the other ON state when L2 is positive with respect to L1. The output waveform has a negative half cycle during which the H-switch is in the one ON state when L1 is negative with respect to L2 and is in the other ON state when L2 is negative with respect to L1.

Surface acoustic wave (saw) devices having series-connected inter-digital transducers

Abstract: To enable increased power coupling into a SAW device for which voltage breakdown is a limiting factor in determining the maximum power which can be coupled, each transducer of the SAW device is replaced by a plurality of series-connected inter-digital transducers (IDTs). For operation in an Nth harmonic mode, there may be N series-connected IDTs which are offset from one another by 1/N wavelengths of the fundamental frequency for which the individual IDTs are designed; for high frequency SAW devices, this further increases the power which can be coupled into the device. The SAW device is particularly useful in a delay-line oscillator to constitute a microwave source for a local oscillator in a radio repeater.

Comparing Fundamental Frequency and Differential Equation Representation of AC/DC

Abstract: HVDC terminals are modeled in load flow and stability programs using certain relationships for real and reactive power derived fran a set of assumptions for fundamental frequency voltages and currents.

Frequency multiplier circuit for producing isolated odd and even harmonics

Abstract: A 180° hybrid receptive of a fundamental frequency signal which may be adjusted over a range of frequencies produces the fundamental frequency signal at two output ports phased 180° apart. Each of the output ports is coupled to a non-linear active device which produces the fundamental frequency and odd and even harmonics thereof. A 180° and 0° hybrid is coupled to receive at respective input ports the signal from the active devices and to produce at one output port all the odd harmonics and to produce at the other output port all of the even harmonics of the fundamental frequency. The even and odd harmonics of the fundamental frequency appearing at the two output ports of the 0° and 180° hybrid are isolated from one another.

High Q, Single Mode S-Band SBAW Oscillators

Abstract: We report the successful development and construction of narrowband Shallow Bulk A coustic I!ave (SEN) delay lines and high-Q oscillators at S-band frequencies. At these frequencies, propagation loss becomes of great interest as a design consideration. The SBAW delay lines are unusual for this frequency because the transducer fingers are not embedded, and still achieve low insertion loss, high Q, and excellent temperature stability. Fundamental frequency SRAW delay lines on AT quartz and fifth-harmonic devices on BT quartz were fabricated. Electron-beam lithography was used to achieve the 0.4 pm linewidth for the fundamental frequency 3.1 GHz devices on AT quartz, and the 2.2 GHz ET-cut devices used photol i thography.

On the Variabilty in F₀ Patterning and the Function of F₀ Timing in Languages where Pitch Cues Stress

Abstract: The basic property of pitch as a cue to linguistic stress is fundamental frequency (F₀) change . That leaves room for a lot of variation: in the direction of the change, the am

Periodic Rayleigh waves of finite amplitude on an isotropic solid

Abstract: Existence of a periodic progressive wave solution to the nonlinear boundary value problem for Rayleigh surface waves of finite amplitude is demonstrated using an extension of the method of strained coordinates. The solution, obtained as a second-order perturbation of the linearized monochromatic Rayleigh wave solution, contains harmonics of all orders of the fundamental frequency. It is shown that the higher harmonic content of the wave increases with amplitude, but the slope of the waveform remains finite so long as the amplitude is less than a critical value.

Coupled-mode theory for the nonlinear interaction of surface plasmons/polaritons

Abstract: A coupled-mode theory for the nonlinear interaction among surface plasmon and polariton (SP) waves is presented, in which pump depletion effects are explicitly taken into account. It is shown that a substantial power transfer from the SP at fundamental frequency to the SP at the second harmonic is not beyond any experimental possibility, provided a phase-matched configuration is employed. Compensation effects, arising when the SP waves propagate at the interface between two nonlinear media, are also considered.

Harmonic Power Combining Of Microwave Solid-State Active Devices

Abstract: A method for combining the power in a selected harmonic of the fundamental frequency for a symmetrical array of oscillating solid-state devices is described and demonstrated. These combiners convert fundamental power to harmonic power with filtering accomplished by symmetry. This technique appears useful for improving the performance of microwave and millimeter-wave power sources by effectively enhancing the frequency-power limitations of existing solid-state devices. An example of the method is provided by a simple three-phase frequency-tripling varactor-tuned transistor oscillator.