Showing papers on "Harmonic published in 1976"

A second harmonic analyzer for the detection of non-centrosymmetry

Abstract: The existence of optical second harmonic generation has been shown to be a highly reliable and sensitive physical test for the detection of crystalline non-centrosymmetry. A second harmonic analyzer has been constructed which can resolve space group ambiguities arising from Friedel's Law with a confidence level greater than 99%. The system has been optimized for use with powdered crystalline samples so as to obviate the need for large single crystals and thus facilitates rapid determination of crystalline non-centrosymmetry. The present analyzer can routinely detect second harmonic generation at levels 1/1000 of that generated in a quartz standard, this is about an order of magnitude increase over previously reported systems. Data are reported on several materials including dibenzyldisulfide, and [(C6H5)3P]3CuBF4. The detection of structural phase transitions with the second harmonic analyzer is reported for BaTiO3, colemanite and phenanthrene. Second harmonic generation in the `cubic' phase of BaTiO3 promises to be a powerful tool for determining the dynamics of the ferroelectric phase transition. It is the most direct method for establishing the existence or nonexistence of microscopic polar regions well above the Curie point in a nominally centrosymmetric phase.

Reactive Compensation and Harmonic Suppression for Industrial Power Systems Using Thyristor Converters

Abstract: This paper discusses the problems and solutions of applying reactive compensation, either static or dynamic, to industrial power systems supplying large blocks of dc power from diode or thyristor converters. The resonance between power capacitors and system reactance can produce high harmonic voltages caused by the harmonic currents generated by converters. The interaction between these harmonic voltages and regulating systems can be minimized by the use of suitable filters. The design of these filters should eliminate the interaction between power system and load and reduce harmonic current flow. Different methods of reactive power control are also discussed.

Study of variations in the male and female glottal wave.

Abstract: A reflectionless metal tube which can act as a pseudoinfinite termination of the vocal tract was used to collect glottal volume‐velocity waveforms produced by 10 male and female adult subjects From each subject, glottal volume‐velocity samples were collected of normal, loud, and soft voice; falsetto and creaky voice; monosyllables with rising and falling intonation; and three‐syllable utterances containing primary lexical stress on one of the three syllables Analysis of the data indicates a wide variation of the glottal waveform shape, its rms intensity and fundamental frequency, phase spectrum, and intensity spectrum It is observed that as the fundamental frequency changes over time, the glottal source varies in one of two different ways In one type of change, the harmonic relations in the glottal spectrum become steeper as fundamental frequency rises In a different type of glottal‐wave change, relations between harmonics tend to remain the same despite a change in the fundamental frequency; the source spectrum in this case is simply shifted along the frequency and amplitude axes as a function of fundamental frequency To account for these variations in the glottal source, at least three factors must be known: the sex of the speaker, the voice register in which he phonates, and the linguistic context in which the phonation occurs

Efficient second‐harmonic generation in three‐dimensional LiNbO3 optical waveguide

Abstract: Highly efficient second‐harmonic generation using a titanium in‐diffused LiNbO3 three‐dimensional optical waveguide was performed with the cw Nd : YAG laser at 1.064‐μm wavelength. The phase‐matching condition to convert the TE00 fundamental frequency to the TM00 or TM20 second harmonic was demonstrated by adjusting the crystal temperature. The conversion efficiency is 1.5×10−4 at 2‐mW fundamental input power under the phase‐matching condition. By using a low‐loss LiNbO3 optical waveguide, equipped with highly reflective cavity mirrors on the input and output surfaces, parametric oscillation is expected.

Investigation of nonlinear waves on liquid jets

Abstract: The breakup of a liquid jet subject to a small sinusoidal disturbance is studied using a sensitive, high‐resolution optical probe technique that generates an electrical signal proportional to the local jet diameter. This signal is resolved into its harmonic components which are measured as a function of distance along the jet axis. Measurements of the growth along the axis of the fundamental and first two harmonic components are compared with calculations based on the nonlinear analysis of Yuen. Excellent agreement is found for cases where the harmonic components lie both inside and outside the bandpass of the instability as described by the linearized theory.

Prediction of core losses for high flux densities and distorted flux waveforms

Abstract: This paper considers the problem of estimating the core losses in a thin magnetic steel lamination when the driving flux contains not only the fundamental, but also odd harmonic components. Two numerical methods of predicting the eddy current losses due to an arbitrary flux waveform are briefly described. The important case of 3rd harmonic distortion is specifically considered. The digital simulations are used to develop a very simple model that describes the eddy current and hysteresis losses under the assumed distortion conditions with good accuracy.

Derivative measurements of light-current-voltage characteristics of (AL, GA)as double-heterostructure lasers

Abstract: A modulation and detection scheme for applying derivative techniques to the investigation of stripe geometry (Al, Ga)As double-heterostructure lasers is described. Modulating at constant modulation index allows the quantities I(dV/dI) and I2(d2V /dI2) to be directly obtained in the same apparatus at the first and second harmonic of the modulation frequency, respectively. Particularly strong indications of laser action and other optical interactions in the laser are contained in the second harmonic voltage response. The same apparatus may be used to obtain derivatives of the light-current relation. These are found to sensitively reveal light-current nonlinearities that are believed caused by filaments and other spatial inhomogeneities and instabilities.

Generation of Coherent Radiation at 53.2 nm by Fifth-Harmonic Conversion

Abstract: The generation of coherent radiation of 53.2 nm by fifth-harmonic conversion of laser pulses at 266.1 nm in both Ne and He is reported.

Subharmonic pitches of a pure tone at low S/N ratio

Abstract: 2AFC scores were obtained on 50 untrained subjects who had to respond to a 3% increment or decrement of the fundamental frequency of two successive signals. The first signal in each trial was a reference, containing six harmonics of 200 Hz. Main variables were the number of harmonics of the second signal in a trial (either 3, 2, or 1) and the presence or absence of continuous background noise. Low scores were observed in the absence of the noise (typically 65% for the 3‐ and 2‐component signals, and virtually 50% for the 1‐component signals), whereas in the presence of the noise much higher scores were observed (typically 90% and 80%, respectively). The results indicate that background noise has great impact on the perceptibility of a ’’low pitch’’ related to the fundamental frequency, even more so than the number of components presented (within the range of three, two, or one components): at a low S/N ratio, even a single harmonic may give rise to the perception of a subharmonic low pitch. Subsequent exp...

Voicing system for electronic organ

Abstract: In a voicing system for electronic organs, square wave signals from a tone generator are converted to a waveform of another shape, the harmonic structure of which is useful for producing certain organ voices. This modified waveform is further modified, as by integration or differentiation, to produce signals of yet another wave shape whose harmonic content makes it useful for deriving still other organ voices. In one embodiment, the square wave pulses are initially converted to narrow pulses which are particularly suitable for the production of reed and certain string voices, and these sharp, narrow pulses are integrated to produce, in effect, a separate source of signals having a sawtooth waveform the harmonic structure of which is particularly suitable for production of cello, diapason and flute sounds. In another embodiment, the square wave pulses are first combined to produce a synthesized sawtooth waveform which may be applied to appropriate filters to produce cello, diapason or flute sounds, and the synthesized sawtooth waveform pulses are differentiated to produce a source of sharp, narrow pulses which may be applied to other suitable filter networks to produce other organ voices such as reed or string sounds. In the process of conversion from one pulse shape to the other, whether by integration or differentiation, all harmonics of the starting pulse, regardless of the frequency of the note, are shifted in phase by substantially 90°, thereby enabling the selective combination of the voice signals from the voicing filters in a way such as to minimize deleterious cancellation of certain harmonics when two or more stops of the organ are played simultaneously.

Fifth-harmonic generation in isotropic media

Abstract: This paper presents a theoretical study of fifth-harmonic generation (FHG) in an isotropic media. Two schemes are discussed-cascade generation in which the fifth harmonic results from successive nonlinear interactions in two separate elements, and direct generation where the fifth harmonic is produced in an isotropic media with third-and fifth-order nonlinear susceptibilities. In the plane-wave approximation almost full conversion of the pumping energy into the fifth harmonic is found to be possible. FHG with a focused Gaussian beam is also investigated. To determine the optimum conditions for FHG in the cascade scheme, the theory of four-wave mixing of light beams with arbitrary confocal parameters and waist locations is developed. In media with third- and fifth-order nonlinearity, the fifth harmonic results from step and direct processes. The interference between these two processes is discussed. Numerical calculations are presented for metal vapor-gas mixtures and Nd:glass laser pumping radiation.

Length controlled stabilized mode-lock Nd:YAG laser

Abstract: A method and apparatus for stabilizing the amplitude and repetition rate of mode-locked Nd:YAG laser pulses by controlling the laser length through a feedback loop is described. The end mirror of the laser is mounted on a piezoelectric crystal which is dithered at a low frequency. A portion of fundamental 1.06 micrometer laser radiation is converted into its second harmonic frequency and the average power of the second harmonic frequency is detected by an integrating detector. The amount of the power of the second harmonic frequency depends on the match between the optical length of the laser cavity and the mode-lock frequency. The length is controlled by a feedback loop which phase compares the output of the second harmonic detector to the piezoelectric crystal dither signal.

Voltage waveform synthesizer and a system that includes the same

Abstract: A voltage waveform synthesizer whereby an ac waveform (which may be varied in frequency) is synthesized from dc or unidirectional voltages in a programmable fashion, the power carried by the waveform being controllable from zero to some maximum value and the harmonic content of the waveform also being controllable. The synthesizer per se is described and it is shown in combination with a rotating electric machine to provide, for example, a variable speed drive mechanism.

Electromagnetic Theory of the Loosely Braided Coaxial Cable: Part I

Abstract: A solution to Maxwell's equations subject to boundary conditions on counterwound helical wires is achieved. The helices are contained in a cylindrical surface that is concentric to a perfectly conducting center conductor of circular cross section. The permittivity of the annular region may be different from that of the external region. The excitation is taken to be symmetrical about the cable which leads to a considerable simplification of the formulation. The key step is to recognize that the assumed form of the current on the thin helical wires is a spatial harmonic expansion that leads to a doubly infinite expansion, in such harmonics, for the resultant fields. The inherent complication of the problem results from the intercoupling between the spatial harmonics of the helix currents. Various generalizations of the theory are also indicated.

Input impedance of a short dipole antenna in a warm anisotropic plasma, 1, Kinetic theory

Abstract: A theory is presented for the input impedance of a short, cylindrical dipole antenna immersed in a warm anisotropic plasma which is described by the kinetic theory (Boltzmann equation). The plasma is assumed to be homogeneous with collisions included. The input impedance is based on the induced EMF technique and a quasistatic approximation. The dipole is assumed to have a triangular current distribution along its axis. For a dipole oriented parallel to the static magnetic field, the input impedance is derived as a one-dimensional integral suitable for numerical integration. Under certain conditions, this integral can be evaluated giving analytical formulas valid near the second and third electron cyclotron harmonics. The results show new contributions to the input impedance due to the excitation of cyclotron harmonic waves which propagate near the harmonics of the electron cyclotron frequency. These harmonic effects are not predicted by either the cold or hydrodynamic theories.

Input current modulation to reduce torque pulsations in controlled current inverter drives

Abstract: A controlled current motor drive system and method for its operation utilizes an open loop technique and simple control circuit additions to modulate the inverter input current at six times motor frequency and reduce sixth harmonic torque pulsations. Conventionally generated current source inverter control signals at six times motor frequency are also used to derive a sixth harmonic ac signal which is fed to the controlled rectifier gating circuit as an additional input.

Digital electronic tuner

Abstract: A digital electronic tuning device is provided in which an arrangement of light-emitting diodes [LED's] or other display elements indicates when two frequencies are equal. If the frequencies are unequal, the device provides an indication of both the magnitude and direction of the inequality. For use as a tuner of musical instruments, one frequency is provided by a preset clock while the second frequency derives from the musical instrument under test. In operation, a circular pattern of lights on the display elements appears stationary when the instrument is in tune and appears to rotate or spin when the instrument is out of tune. Some information about the harmonic content of the frequency of the signal under test may also be read from the device. In one embodiment, the invention may be used in connection with a stepping motor to automatically tune an instrument.

Harmonic mixing and frequency measurement at 2.5 THz using Josephson junctions

Abstract: The frequency of quartz-crystal oscillators, operating near 120 MHz, has been multiplied by a factor of 21060 and mixed with the frequency of a discharge-pumped water vapour laser operating at 2.53 THz (118 mu m wavelength). The final stage of multiplication and harmonic mixing was performed using point-contact Josephson junctions, with harmonic numbers up to 156. The signal-to-noise ratio of the final intermediate frequency signal was limited by phase noise in the quartz-crystal oscillator, but was about 17 dB higher than that obtained when a klystron, phase-locked to the crystal oscillator, was used as a transfer oscillator. The power levels of the intermediate frequency signals from the Josephson mixer are discussed. The frequency of the laser when set to its Lamp dip was found to be 2527952.91+or-0.05 MHz.

Passive navigation system with frequency coding

Abstract: On a vehicle to be navigated, a transmitter for radiating a signal having a plurality of frequencies and a receiver tuned to receive a predetermined harmonic of each of the plurality of frequencies, discriminate between the predetermined harmonics, and determine the range of position markers reradiating each of the predetermined harmonics, with a plurality of passive markers, each having a nonlinear electrical response characteristic and each tuned to reradiate the predetermined harmonic of a different one of the plurality of frequencies when the radiated signal from the transmitter impinges thereon, fixedly mounted at predetermined positions relative to a desired course to be traveled by the vehicle.

Electronic musical instrument having transient musical effects

Abstract: An electronic musical instrument of a type wherein a plurality of systems are provided each system comprising memories storing respective harmonic component waveshapes which are read at the same reading rate and the read out harmonic waveshapes are suitably mixed to obtain a desired musical tone. Each system also comprises a circuit for controlling the envelope of the waveshapes read from the memories. In the first system, the envelope control is made in such a manner that the envelope will rise upon depression of a key, thereafter maintain a constant level as long as the key is kept depressed and decay upon release of the depressed key. In the second system, the envelope is controlled so that the envelope will rise in a short time and immediately decay thereafter. The respective harmonic waveshapes thus controlled in envelope in the respective systems are then suitably selected and mixed together. As an example of the envelope control in the second system is shown a structure for producing a so-called "chiff" effect by providing the fractional period during which the envelope rises and subsequently falls at the attack portion of the musical tone. Desired waveshape or waveshapes are selected from among the harmonic waveshapes controlled in the envelope in the second system for mixing with the harmonic waveshapes read from the first system. By this arrangement, amplitudes of the frequency components of the selected harmonic waveshapes are emphasized during the fractional period.

Compensation of phase-matching dispersion in generation of nonmonochromatic radiation harmonics. I. Doubling of neodymium-glass radiation frequency under free-oscillation conditions

Abstract: An efficiency of ~3% was obtained in generation of the second harmonic of nonmonochromatic neodymium laser radiation in an LiIO3 crystal. The laser was operated under free-oscillation conditions and the dispersion of phase matching was compensated by a diffraction grating. An investigation was made of the angular and spectral characteristics of the harmonic radiation. It was found that compensation of the phase-matching dispersion widened the harmonic spectrum from 0.2–0.3 nm to half the width of the laser spectrum.

Nonlinear theory of rf heating at cyclotron harmonics

Abstract: The nonlinear interaction of a single particle with an electromagnetic wave at a cyclotron harmonic is studied. Emphasis is on the large wavelength limit (fast wave). The cases of a coherent wave particle interaction and of an incoherent interaction are treated. In both cases explicit expressions for the temporal evolution of the particle perpendicular energy distribution function are presented. The heating is efficient at the first two harmonics. The formation of a suprathermic tail is predicted at the second and higher harmonics.

Effects of beam on the hydrodynamic characteristics of ship hulls

Abstract: Forced oscillation experiments were carried out with a systematic ship model family of which the length-beam ratio ranged from 4 to 20. The experiments also included a thin plate to simulate the case of an infinite length-beam ratio. Vertical and horizontal harmonic motions in calm water were considered and the corresponding hydrodynamic coefficients were determined. Moreover the vertical motions and added resistance in waves were measured. The results are presented in graphical form and are compared with some existing calculation methods.

Inverter circuit for producing synthesized sinusoidal waveforms

Abstract: An inverter circuit which provides a synthesized sinusoidal output waveform having a low harmonic content. The inverter is light in weight, highly efficient and driven by a fundamental rectangular component having a frequency equal to the desired synthesized sinusoidal output frequency. Single-phase or three-phase output is provided.

Measurement of logarithmic decrements through the measurement of time

Abstract: The paper describes an arrangement which can be used to measure the period and logarithmic decrement of a damped harmonic torsional oscillation without the need to perform any length measurements. By means of suitably arranged electronic circuits, all measurements are reduced to those of time intervals. These consist of a measurement of the period and of two time intervals which a travelling laser beam requires to sweep past two stationary photoresistances. A suitable procedure for the location of a zero base line is indicated, and it is shown that the residual uncertainty of this operation is the source of the dominant error.

Microwave diode coaxial circuit oscillator improvement

Abstract: An improvement in a prior art microwave diode coaxial oscillator circuit comprising an unloaded fundamental frequency cavity for prevention of energy loss in the matching termination at the resonant frequency of the circuit and a second harmonic resonant cavity for controlling second harmonic loading of the diode and for reducing noise in the output signal.

Electronics musical instrument

Abstract: In this electronic musical instrument, two separate tone generators of different type each produce a tone corresponding to an actuated key switch. Advantageously, one of the tone generators is of the Fourier synthesis type. In the other tone generator, a source waveshape having abundant harmonic components is processed by a tone color and volume control system which modifies the frequency spectrum and amplitude of the source waveshape in a time variant manner. The two generated tones are combined to produce the desired musical note. Actuation of each key switch produces, in an assigned time slot, frequency information corresponding to the selected note, and designating the phase angle between successive sample points to be read from a waveshape memory. In the Fourier synthesis type generator, plural waveshape memories store harmonically related sinusoids, all of which are accessed simultaneously and weighted by harmonic coefficients to produce the first tone. In the other tone generator, a waveshape having abundant harmonics is read from a waveshape memory and is processed by that one of a plurality of tone color and volume control systems which is assigned to the corresponding time slot.