Showing papers on "Harmonic published in 1971"

Electron pitch-angle diffusion driven by oblique whistler-mode turbulence.

Abstract: A general description of cyclotron harmonic resonant pitch-angle scattering is presented. Quasi-linear diffusion coefficients are prescribed in terms of the wave normal distribution of plasma wave energy. Numerical computations are performed for the specific case of relativistic electrons interacting with a band of low frequency whistler-mode turbulence. A parametric treatment of the wave energy distribution permits normalized diffusion coefficients to be presented graphically solely as a function of the electron pitch-angle. The diffusion coefficients generally decrease with increasing cyclotron harmonic number. Higher harmonic diffusion is insignificant at very small electron pitch-angles, but becomes increasingly important as the pitch-angle increases. One thus expected the rate of pitch-angle scattering to decrease with increasing electron energy, since the resonant value of the latter varies proportionately with harmonic number. This indicates that, in mirror-type magnet field geometrics, such as the earth's radiation belts, the diffusion losses of high energy electrons are likely to be appreciably slower than those at low energy.

Enhancement of optical second harmonic generation by utilizing the dispersion of air

Abstract: The dispersion of air, which causes a phase shift of 27.4°/cm between optical waves at 1.06 and 0.53 μ, has been used to compensate for phase shifts between the fundamental and second harmonic in a two‐pass second harmonic generation experiment. Use of this dispersion enables the net phase shift to be adjusted to zero, doubling the effective interaction length of the nonlinear crystal. The extension of this technique to multiple‐pass experiments is discussed, and applications to internal harmonic generation are treated.

Receiver tuning system

Abstract: A harmonic generator produces simulated station signals which are heterodyned in the mixer stage of a receiver. A local oscillator of the receiver is swept through its frequency bandwidth, producing an IF pulse each time the receiver tunes one of the simulated stations. The IF pulses are counted, and upon reaching a number preset on station selection switches, convert the sweep circuit to an AFC amplifier, maintaining the receiver tuned to a desired station frequency.

Method of and apparatus for the detection of stolen articles

Abstract: A system for detecting the unauthorized removal of protected articles from a designated area comprising a harmonic generator circuit made up of a semiconductor diode chip and a pair of antennas adapted to receive a radio frequency signal at a first frequency and transmit a second radio frequency signal at a second, relatively higher frequency. Transmitting and receiving means are positioned adjacent an exit area for actuating the circuit and an alarm when protected articles approach the area, and means are provided for deactivating the circuit when the protected article is legitimately purchased. The generator circuit can be manufactured at very low cost thereby permitting, when a legitimate sale is made, permanent deactivation of the circuit without removing or otherwise handling the tag or label carrying the circuit.

Calculation of Second‐Harmonic Generation in a Piston Beam

Abstract: We discuss the nonlinear generation of a second‐harmonic component in the first‐harmonic beam from a circular plane piston, radiating into a fluid. First‐order perturbation theory is used; higher harmonics, absorption, and depletion of each harmonic are ignored, although a partial correction for the last two effects is applied later. The ratio of piston diameter to first‐harmonic acoustic wavelength is assumed to be about 30 or greater. In particular, the axial behavior of the second harmonic, which has marked structure, is found to agree well with experimental results in water. Also, the average value of the second‐harmonic field is calculated over a circle coaxial with the source, parallel to it, and of the same size. This average differs considerably from the result of an oversimplification that treats the first‐harmonic beam as cylindrically collimated plane waves. When compared with measurements in water, the average agrees well at a source pressure of 3 atm but progressively less well at 5 and at 6 ...

Heaving oscillations of twin cylinders in a free surface

Abstract: This paper presents a solution of the two-dimensional potential problem associated with harmonic oscillations of a twin-hull body in a free surface. The body considered has two identical, rigidly connected, circular cylindrical hulls, semisubmerged, performing small vertical oscillations. Results of the added-mass and damping coefficients are presented as functions of the oscillation frequency. Data presented can be used as a guidance to estimate the hydrodynamic characteristics of catamarans.

Harmonic synchronization of nonlinear oscillators

Abstract: The locking range of a harmonic synchronized oscillator is calculated, and it is shown to be proportional to the relative harmonic amplitude produced by the nonlinearity. For completeness a simple method is given for calculating the harmonic output produced.

Megawatt Tunable Second Harmonic and Sum Frequency Generation at 280 nm from a Dye Laser

Abstract: The second harmonic frequency of a high‐power interferometrically narrowed and tuned rhodamine 6G dye laser has been generated in an ADP crystal with 10% efficiency. Twenty‐millijoule‐megawatt pulses, continuously wavelength tunable from 280 to 290 nm, have been obtained with a bandwidth of 0.2 nm. Ultraviolet sum frequencies have also been generated with similar efficiency.

Dual frequency radiometer

Abstract: Disclosed is a dual frequency radiometer concept whereby selection of operating frequencies allows the detection and discrimination of metal, water, tarmac, concrete and wet soil from natural terrain backgrounds. Disclosed is one radiometry system designed to detect metal in the presence of background of normal terrain features, including vegetation, ground soil and water. Embodiments of the system are disclosed, employing two radiometer sensing heads operating at different preselected frequencies. The output of each sensing head is mixed with a respective locally generated signal f1 and f2 to produce a common IF frequency and alternately applied to an IF channel. The output of the IF channel is synchronously detected and the difference in level of radiometric energy at the two frequencies is synchronously detected and integrated to produce a difference signal indicative of the presence or absence of metal in the field of view. In one embodiment, the local frequency sources are klystron oscillators and in the second embodiment, solid state Gunn diodes are used. The physical embodiment of one preferred form of sensing head is disclosed. One third embodiment employs a single oscillator and multiplier to produce a second harmonic frequency. The fundamental and the second harmonic are used to serve as reference for the two superhet signal channels. Gain drift, frequency drift and oscillator noise cancellation are all achieved in this embodiment.

A surface-charge induction motor

Abstract: A motor that uses an electric field interaction with surface charges induced on the surface of a lossy dielectric rotor as the force mechanism is described. A theory of force generation and efficiency for a transverse-magnetic wave interaction with a moving conducting medium and a space-harmonic analysis of a practical circuit to carry such a wave are presented. A comparison is made between the results of this analysis and test results on a three-phase 60-Hz motor using a Bakelite or a Plexiglas rotor. Satisfactory agreement between theory and experiment is obtained in most respects. Motor operation was observed in both directions of rotation, as a result of interaction with the first backward space harmonic. Generator operation is also theoretically possible and the theory for a single-harmonic-wave generator is presented. Generator operation was not observed, however, in the device that was tested.

Vehicle tire pressure monitor system

Abstract: The condition monitor provides information as to the state of a monitored dual state device having, for example, possible satisfactory and unsatisfactory conditions. Use is made of a passive transducer element powered by a space-transmitted radio frequency signal of fundamental carrier frequency. In the unsatisfactory condition of the monitored device, the passive transducer emits a signal that is a harmonic of the carrier frequency, which signal is detected for the operation of a suitable alarm or remedial control. In the normal or satisfactory condition of the monitored device, the carrier frequency energy causes the passive transducer to inhibit production of second harmonic energy.

Dc keyed synthesis organ employing an integrated circuit

Abstract: A synthesis-type organ with direct current keying, envelope shaping and individual harmonic scaling particularly adapted to be compatible with frequency divider and MOSFET integrated circuit techniques. A DC voltage is scaled to several appropriate selected levels for the fundamental and individual harmonics and chopped by tone signals for the fundamental and selected harmonics to provide a collection of appropriately scaled square wave signals at the chopping frequencies. These square waves are individually keyed with appropriate envelope control through band pass sine filters adapted to reject all but the fundamentals of the keyed signals. The filtered outputs are mixed to supply output musical signals of appropriate harmonic quality having a desirable attack and decay envelope.

Self-Consistent Treatment of the Frequency Spectrum of a Model Paraelectric

Abstract: The temperature dependence of the frequency spectrum of a model NaCl-structure paraelectric exhibiting soft-mode behavior at the zone center is treated self-consistently. A variational formulation is employed, yielding a set of nonlinear integral equations which are solved iteratively. The difficulties associated with perturbative treatments are avoided by starting from a renormalized phonon basis which represents a stable state of equilibrium for the crystal. In particular, the soft-mode branches, which may be imaginary in the harmonic approximation, are renormalized and treated self-consistently. The model consists of rigid anions and cations of unequal masses interacting via long-range Coulomb forces plus a short-range interaction extending to second neighbors. Anharmonicity is introduced through a parametrized quartic interaction. Calculations are carried out for a wide range of model parameters, including the situation where the phase space subtended by the imaginary harmonic frequencies may constitute a large fraction of the Brillouin zone. The importance of including the effect of the soft-mode branches is discussed in detail. It is pointed out that the self-consistent equations do not admit a zero solution for the soft-zone-center optic mode. An explanation is given of why the Curie-law dependence of the soft-zone-center frequency squared may extend to lower temperatures than one might expect on simple qualitative grounds. Attention is given to the coupling of the soft TO branch to the TA branch of the same symmetry, and the anomalous temperature dependence of the acoustic branch at finite wave vector is displayed. Finally, the temperature dependence of the intersublattice correlation function is calculated, and it is pointed out that the soft-mode branches contribute significantly to the temperature dependence of this function. The implications of the latter for a transition to an ordered phase are discussed.

Harmonic Interaction Between HVDC Converters and ac Power Systems

Abstract: A technique is presented for calculating the harmonic interactive behaviour between HVdc and ac systems. The ac system is represented by discrete impedances at harmonic frequencies, and the calculations involve the repeated iteration of a large computer program representative of the interaction of generated ac harmonic currents with the ac system impedances and filters. Examples of computed harmonic conditions are presented, and the degree to which the harmonic behavior is dependent on the ac system impedances and filters is discussed for both normal and abnormal harmonics.

Fourier Analysis of Alternating Current Polarography: Amplitude and Phase of Fundamental and Second Harmonic AC Polarographic Waves

Abstract: The Fourier analysis of the instantaneous AC polarographic current was performed with a computer on-lined to a potentiostat. From the Fourier spectra, the amplitudes and phase angles of both the fundamental and the second harmonic AC polarographic waves were obtained. In the Cd(II) system, the current amplitude DC potential curves and phase angle-DC potential curves for the fundamental and the second harmonic AC polarographic waves were compared with the theoretical curves. The method is applicable to the accurate analysis of electrode reaction kinetics.

Frequency synthesizer apparatus

Abstract: Harmonic generator type of frequency synthesizer employing a reference frequency signal equal to the spacing between adjacent channels and a displaced reference frequency signal which differs from the reference frequency by a few hertz. The reference frequency signal is applied to a first harmonic generator which generates a spectrum of harmonics of the reference frequency. The spectrum is applied to a phase-locked loop which produces an output frequency signal equal to a particular one of the harmonics of the reference frequency. The displaced reference frequency signal is applied to a second harmonic generator which generates a spectrum of harmonics of the displaced reference frequency. The spectrum of harmonics of the displaced reference frequency is combined with the output signal of the phase-locked loop in a mixer and the output of the mixer is applied to a lowpass filter. The frequency of the only output signal from the filter is equal to the same particular harmonic to which the phase-locked loop is locked times the difference in frequency between the reference frequency and the displaced reference frequency. Since the difference between the frequencies is a known, fixed value, the signal from the filter is thus a precise measure of the particular harmonic of the reference frequency being produced by the phase-locked loop. The output frequency of the filter may be counted and compared with a preset count representing the value of a predetermined harmonic of the reference frequency to which it is desired to tune the phase-locked loop. The difference between the counts is employed to generate a voltage signal which is coupled to the phase-locked loop to change the tuning of the phase-locked loop to another harmonic of the reference frequency.

Simultaneous optical parametric oscillation, second harmonic generation, and difference‐frequency generation

Abstract: We report the observation of simultaneous phase matching of three separate nonlinear optical processes The second harmonic of the signal wavelength of a parametric oscillator was generated and then mixed with the idler wavelength of the oscillator to produce a difference frequency, all in the same nonlinear crystal We have observed 34% average power conversion from the signal to its second harmonic, which is at a shorter wavelength than the pump

Frequency synthesizer apparatus having automatic fine tuning

Abstract: Harmonic generator type of frequency synthesizer employing a reference frequency signal equal to the spacing between adjacent channels, a displaced reference frequency signal which differs from the reference frequency by a few hertz, and a differential frequency signal equal to the difference between the reference frequency and the displaced reference frequency. The reference frequency signal is applied to a first harmonic generator which generates a spectrum of harmonics of the reference frequency. The spectrum is applied to a phase-locked loop which produces an output frequency signal equal to a particular one of the harmonics of the reference frequency. The displaced reference frequency signal is applied to a second harmonic generator which generates a spectrum of harmonics of the displaced reference frequency. This spectrum is combined with the output signal of the phase-locked loop in a mixer and the output of the mixer is applied to a low-pass filter. The frequency of the only output signal from the filter is equal to the same particular harmonic to which the phase-locked loop is locked times the difference in frequency between the reference frequency and the displaced reference frequency.

Enhanced optical third-harmonic generation by coupled nonlinear absorption

Abstract: Combined nonlinear absorption and third-harmonic generation has resulted in enhanced harmonic output in a liquid-dye medium phase matched by anomalous dispersion. The measured absorption is employed in calculating the third-harmonic power.

Subharmonic generation and the trapped-plasma mode in avalanching silicon p + -n-n + junctions

Abstract: Experimental evidence is presented which distinguishes two mechanisms whereby an avalanche diode can efficiently generate microwaves at transit angles below those of classical transit-time oscillations. Measurements of external current waveforms and subsequent calculations of terminal voltage waveforms demonstrated that efficient generation (η ∼10 percent) of microwaves was possible at sub-harmonics of transit-time excitations. This subharmonic generation occurred when various harmonic components interacted such that the peak total voltage was delayed with respect to the fundamental. In such cases of multiharmonic synergetic excitations, the peak displacement currents were less than 0.25 of that required for avalanche shock-front initiation. The distinguishing features of high-efficiency operation (η ∼50 percent) were found to be completely consistent with a trapped-plasma mode interpretation. Experimental external current and dV/dt waveforms have substantiated Evans' circuit analysis [28]. dV/dt waveforms indicated peak displacement currents at breakdown which were on the order of 1.5 times that required for shock-front initiation. Approximate conduction current waveforms exhibited larger currents during the shock-front transit than during the extraction period. General features were consistent with calculations made by Cottam [29]. Circuit characteristics for both subharmonic generation and the trapped-plasma mode were similar. Circuit analysis also indicated the critical importance of each separate harmonic of a trapped-plasma mode fundamental. Harmonic generation utilizing the trapped-plasma mode enabled an extension of the upper bound of the frequency of efficient generation.

Generation of microwave frequency combs with narrow line spacing

Abstract: A harmonic generator such as a step recovery diode device is driven by two or more input signals of different frequencies to produce a comb spectrum consisting of lines at multiples of the input signal frequencies interspersed with lines at the frequencies of the intermodulation products.

Phase-Matched Critical Total Reflection and the Goos-Haenchen Shift in Second-Harmonic Generation

Abstract: : It is well established that a totally reflected light beam of finite diameter undergoes a lateral displacement, known as the Goos-Haenchen shift. The theory for the corresponding effect in nonlinear optics is presented. The special phase-matched case, in which both the fundamental and second harmonic are at critical total reflection, is shown to have a characteristic radiation pattern. Since the finite beam diameter is taken into account, divergencies of earlier theories are eliminated. (Author)

Phase-locking millimetre-wave klystrons for the measurement of submillimetre laser frequencies

Abstract: A single-loop method of phase locking up to 100 GHz is described. Spectral broadening observed in harmonic mixing with an HCN laser at 891 GHz (with resolution 1 in 108) is attributed to phase noise and modulation on the base-reference quartz-crystal oscillator. Zero beats at 99 GHz between klystrons phase-locked to a common reference give frequency resolution of the order of 1 in 1013.

Self resonant drive for deep well pump

Abstract: Resonant column pumping devices drive a liquid column in coincidence with the resonant oscillations of the column both in frequency and phase for maximum operating efficiency. A piston at the top of the column is driven at a speed corresponding to the half wave frequency, or an odd harmonic thereof, of the liquid column by using the resonant column frequency to control the frequency of application of the driving force impulses transmitted to the liquid column. Means comprising inertial means are coupled to the piston and include actuating means, such as a slideable plunger, inertially responsive to the position of the piston for actuating a position adjustable switch means. The switch means in turn controls the time of the occurrence of the application of the motion to the piston at the resonant frequency of the liquid column, and at the proper phase with relationship to the motion of the liquid column.

Analog harmonic rejecting phase detector

Abstract: An analog harmonic rejecting phase detector with even harmonic rejection achieved through a fundamental frequency, fr, phase detector section and rejection of the stronger odd harmonic signal content passed from the input signal through the fundamental frequency section. It includes a plurality of odd harmonic frequency phase detector sections such as 3fr, 5fr and possibly other odd harmonic sections up to and including a (2n 1)fr odd harmonic section. The reference signals 3fr, 5fr, etc., are square waves so phase related relative to fr as to achieve mutual cancelling with like harmonic content in the signal being passed through an invert-noninvert amplifier of the fundamental frequency section and passed to a summing amplifier. This requires an attenuator circuit after an invert-noninvert amplifier in each odd harmonic section to properly balance signal strength to the strengths of their respective counterparts passed through the fundamental frequency section. The resulting output of the summing amplifier is so integrated through a low pass filter as to present a plus or minus output voltage indicative of the input signal, fin, phase lead or lag and the magnitude of phase displacement relative to the square wave reference signal fr.

Harmonic extraction from high-efficiency avalanche diodes

Abstract: A novel harmonic-extraction method for operation of high-efficiency avalanche diodes has been demonstrated. It has been shown that high-efficiency power output can be obtained not only at the trapped-plasma frequency, but also at harmonic frequencies with respect to the trapped-plasma frequency. Second-harmonic powers of 110 W at 2.67 GHz with 22-percent efficiency from L-band diodes, and 64 W at 4.85 GHz with 15-percent efficiency from S-band diodes have been obtained. Third-harmonic extraction has extended the power output into the lower X-band frequency. Microstrip circuits for harmonic-extraction have been developed and analyzed. The circuit impedance requirements at the diode terminals have been computed. The circuit has been discussed in terms of a multiple-reflection triggering process. Useful information for circuit design has been deduced from a series of harmonic-extraction experiments. The voltage waveforms have been measured and have shown evidence of harmonic extraction and its association with the trapped plasma mode.