Abstract: The apparent initial phase of a point source of Rayleigh waves is shown to depend on the inclination of the source to the vertical. This effect is frequency dependent; the frequency dependence vanishes for a vertical or horizontal source. Corrections must therefore be applied to the phase velocities determined by the single-station method and, less significantly, to group velocities; these corrections depend on a knowledge of the angle of inclination of the source.

Abstract: Rayleigh surface wave phase velocity determination from digitized seismograms from pairs of stations

Abstract: A phase shift network is described which adjusts the phase, from -π to +π, of an incoming signal without change in amplitude with respect to phase.

Abstract: By using a discharge tube filled with pure neon as a nonlinear element, it has been found possible to obtain simultaneous locking of both longitudinal and transverse modes of a 6328 A He–Ne laser Under certain circumstances, each transverse mode has all its longitudinal resonances phase locked to form a narrow pulse, but the pulses corresponding to the various transverse mode orders do not coincide in time Beam scanning has been observed when the frequency spacing between the transverse modes is a simple fraction of the longitudinal mode spacing Under these conditions, a ``spot'' of light traces out a zig‐zag path in the laser cavity

Abstract: In a frequency synthesizer, multiple signals having the same reference frequency, but a different phase, are provided. Each one of the reference signals is used to correct the frequency of the VCO at a different time during the time interval necessary for one cycle of the reference signal to occur, thereby increasing the number of corrections without increasing the reference frequency of correction.

Abstract: Phase fluctuations of a laser beam propagating through a turbulent atmosphere are studied as a function of the distance in a cross section of the beam. An interferometer is described that allows simultaneous measurements of phase fluctuations for pairs of rays that travel in the beam at different distances between each other. Experiments with this method have been performed in an urban center at a distance of 3.5 km and 0.5 km from the source (a helium–neon laser). The results of these measurements are described, and the behavior of the mean square fluctuation of the phase difference is studied. The values of the structure constant Cn are calculated.

Abstract: Testing the response of a system such as a servo to an input signal of a relatively high signal (WH) while using a correlator which operates at relatively low frequencies (e.g. WL). A signal of frequency WH and a signal of frequency (WH+WL) or (WH-WL) are generated and one of these is applied to the system under test. The other signal is multiplied by the output signal from the system, and the thus-formed multiplied signal is compared with two signals of frequency WL which differ in phase. The signal of frequency (WH + OR - WL) can be generated by multiplying each of two signals of frequency WH which differ in phase by a respective one of two signals of frequency WL which differ in phase, and adding (or subtracting) the thus-formed multiplied signals.

Abstract: Tidal heights and currents were measured at a depth of 3903 meters off the coast of northern California for 46 days in 1966. From spectral analysis of the data, the amplitudes of various harmonics of tidal heights and current speeds and their corresponding phase differences were estimated. Good correlation between water current amplitudes and tidal heights was observed. Significant spectral peaks were found for both currents and tides corresponding to the O1, K1, N2, and M2 components. It is concluded that the measured ocean-bottom currents at this location are produced primarily by tides. The maximum spectral amplitude, 2.4 cm/sec, was obtained for the M2 component of current. The M2 component of tidal height was found to lead the M2 component of current by 45.4 degrees. Assuming two opposed traveling waves for ocean tides, theoretical amplitude relations and phase differences between tidal heights and current speeds were derived. The estimated total dissipation of energy for all the components was found to be 7.31 × 10−2 erg cm−2 sec−1.

Abstract: DISTRIBUTIONS of phase variation in light wavefronts can only be made visible by converting them into corresponding distributions of amplitude. This is achieved directly by interference with a “reference” wavefront, which is, of course, the basic principle of all two beam interferometers, and is also the means by which changes in a phase distribution recorded holographically may be made visible1–3. The papers referred to give accounts of (a) the “live” interference fringes, which are seen when a hologram is replaced exactly in its original position in the same apparatus after processing, and changes occur in the object which result in phase variation at the hologram, and (b) the “frozen” fringes, seen when two reconstructed wavefronts from a single hologram plate, corresponding to two successive exposures the plate has received, interfere to reveal the change in the phase distribution in the object field between the exposures.

Abstract: A method of stabilizing the operating frequency of a laser which includes comparing by means of interference the relative phase of two beams of radiant energy from the laser, one of which is a reference while the other passes through the active lasing material The optical path traversed by the reference beam is adjusted to produce a selected condition at the point of interference when the laser is oscillating at a frequency which corresponds exactly to an anomaly in the dispersion of the lasing material Thereafter, the laser frequency is stabilized by adjusting its operating frequency to maintain this condition Preferably, the comparison is made by varying the reference phase about the selected value Apparatus for performing this method includes means defining two substantially equal optical paths for radiation emitted by the laser, one of which extends through the active material of the laser The two paths are terminated at the same point so that interference occurs and the apparatus includes means for detecting the output from the point of interference Finally, means are provided for controlling the laser frequency to maintain a predetermined interference condition

Abstract: An equivalent network representation of a feedthrough lens array, which takes into account mutual coupling between the array elements, is presented. The model is employed to predict performance characteristics, which include element mismatch, peak voltage loading of the phase shifters, element currents, and transmitted power. Both analog and digital phase shifters are treated in the analysis. It is shown that, irrespective of the type of phase shifter, the mismatch from element to element at a fixed scan angle is not identical. This variation is explained in terms of the multiple reflections that take place between the two surfaces of the lens. Further, as a function of scan angle, the element mismatch for a digitally phased array lens does not vary in a smooth manner but exhibits a decided ripple.

Abstract: A multimode antenna for simultaneously providing at least one frequency-scanned mode and a phase-scanned mode. The isolated ports of the directionally coupled radiating apertures of a cross-fed frequency-scanned array, are adapted to be fed from a fixed frequency source by a phased array of voltage-controlled phase shifters or by mechanically scanned means for adjusting the phase gradient (or by a combination of the two). The fixed frequency corresponds to a direction-frequency (of the frequencyscanned array) outside the range of directions to be covered by the phased array, thereby providing mutual isolation between the phased-array energy and the frequency-scanned energy.

Abstract: An interferometer is described. It is designed for measurements of submicroscopic displacement amplitudes of small biological structures in living animals. Its output is frequency independent. The instrument may be used for measuring: (1) absolute displacement amplitudes as low as 3 × 10−10 cm between 20 and 20 000 Hz; (2) phase angles of the displacements with respect to that of the applied sound signals; (3) transient responses of the vibrating structure. Theory of operation is discussed. Fabrication of microscopic mirrors and construction details of the interferometer are given. Experiments performed with the aid of an earphone as a vibrating object are included to show the characteristics of the interferometer. Calibration is precise (within 1 dB) and repeatability is excellent, both with respect to amplitude (within 1 dB) and phase (within 5°). Experiments on living animals and cadavers, giving amplitude and phase data, will be included in a separate paper.

Abstract: Experiments exploring the possibility of applying scatter plates to three-dimensional holography of distributions which may be transilluminated are reported. Good depth discrimination of arrays of particles and of three-dimensional phase distributions made visible by interference are demonstrated. The versatility of the scatter plate is further demonstrated by examples of holograms made with white light and by Q-switched ruby lasers. The scatter screens required may be fabricated in the same apparatus used for holographic recording, and practical details are given.

Abstract: A STEREOPHONIC LOUDSPEAKER SYSTEM IS PROVIDED COMPRISING TWO PAIRS OF LOUDSPEAKERS. EACH PAIR IS ORIENTED WITH THEIR AXES AT RIGHT ANGLES TO EACH OTHER AND SUBSTANTIALLY EQUIDISTANT FROM THE POINT OF INTERSECTION OF THE AXES. THE SPEAKERS ARE SO ARRANGED THAT ONE SPEAKER OF EACH PAIR FACES THE LISTENER AND THE OTHER SPEAKER HAS ITS AXIS SUBSTANTIALLY PERPENDICULAR TO THE LISTENER. MEANS ARE PROVIDED FOR MATRIXING THE SIGNALS PRODUCED BY A RIGHT AND LEFT AMPLIFIER SYSTEM TO PROVIDE A SUM SIGNAL AND A DIFFERENCE SIGNAL. SUM SIGNALS ARE APPLIED IN PHASE TO THE SPEAKERS WHOSE AXES ARE DIRECTED TOWARD THE LISTENER, AND DIFFERENCE SIGNALS ARE APPLIED TO THE SPEAKERS WHOSE AXES ARE POSITIONED AT RIGHT ANGLES WITH RESPECT TO THE DIRECTION OF THE LISTENER, THE DIFFERENCE SIGNALS TO THE TWO PERPENDICULAR SPEAKERS BEING APPLIED 180* OUT OF PHASE WITH EACH OTHER. AS A RESULT, A STEREOPHONIC SOUND EFFECT IS PRODUCED BY THE SYSTEM.

Abstract: This paper reviews the operating principles of four types of reciprocal latching ferrite phase shifters and compares them with respect to normalized phase shift and RF insertion loss. The effects of frequency and temperature on the phase shift are also discussed. Consideration is given to size and weight, as well as RF power handling, important factors in an array intended for field-environment conditions. Partially switched configurations using quasi-circularly polarized normal modes are shown to have the most desirable performance characteristics of the phase shifters studied. Such structures can have a simple geometry that is compatible with low-cost mass production, and can also be adapted to computer-controlled compensation of changes in operating temperature and frequency.

Abstract: : A system was designed, constructed and tested which provides dynamic adaptive phase compensation for atmospheric distortions. This demonstrates that arrays can be built larger than previously thought possible because of atmospheric effects. Without adaptive controls, the atmosphere limits the signal-to-noise ratio improvement and the beamwidth reduction which can be obtained using a larger transmit-receive aperture. We accomplished phase compensation for the transmitted beams and the received signals of a two-element 10.6 micron array. By providing adaptive phase control to assure that the two transmitted beams arrived at the target in phase, the power on target was increased by at least 75 percent over the nonadapted case. In addition, the amplitude fluctuations of the received signals were drastically reduced because the adaptive transmitting system eliminated the frequent destructive interference normally seen when two beams are transmitted. Adaptive control of the relative phase of the two received signals before adding also resulted in comparable increases in signal power. The locking of two lasers with a 4.5 MHz difference frequency provided the local oscillator for heterodyne detection. A near target 500 feet and a far target 3 miles from the transmitter were used. (Author)

Abstract: The reflection of a finite‐amplitude ultrasonic wave from an interface was described by assuming that the Fourier Components in the wave are shifted in phase as though they were independent waves (Part I). In Part II, the behavior of the distorted wave after reflections that produce nonzero component phase shifts is predicted using a computer model. The progress of these “unstable” waves toward the “stable” waveform is described. Experimental results obtained using a pulse technique are in good agreement with the computer results.

Abstract: This disclosure describes a signal generator for producing a family of signals of common frequency and of uniformly stepped phase progression with the rate of progression or phase slope adjustable. Signal sets of this character find application for control of beam direction in electronically steered array radiators of radar, sonar and communications systems, and in frequency selective filters of the kind tunable to scan through a band of frequencies. The signal generator as described comprises a reference harmonic spectrum generator and a steering harmonic generator provided with basic frequency inputs of common frequency value but with a phase difference made adjustable as by coupling one such input through an adjustable phase shifter. Each harmonic of the spectrum produced by one generator is mixed with a harmonic of different order from the other generator to provide a group of signals all of common frequency, corresponding to the difference in order of the two harmonics from which each is derived, and with each of the signals phase-displaced from the next by a phase difference equal to the phase shift introduced through the input phase shifter and adjustable thereby. These signals then are again mixed with steering signals and output sidebands selected to yield the desired set of output signals all of common frequency and of phase slope dependent upon the setting the adjustable phase shifter.

Abstract: An array of similar images may be synthesized by holographic reconstruction techniques. To produce a large array of similar images, a hologram is constructed that contains the spatial frequency spectrum of the desired array. This frequency spectrum may be generated by usual holographic procedures wherein an object wave and a reference wave are made to interfere on an energy sensitive surface. Since the information contained on the hologram represents an array of points which synthesizes the spatial frequency spectrum, the hologram must be produced by sequentially exposing the energy sensitive surface to a series of interference patterns. To control the amplitude and phase distribution of each point representing the spatial frequency spectrum, both the exposure time and phase displacement between the interfering beams are uniquely determined from a mathematical model of the spatial frequency spectrum.

Abstract: Techniques for reducing propagation-induced phase fluctuations in frequency distribution systems are discussed and compared. Examples of both microwave and optical methods are presented. Stabilization to a few parts in 10^{8} over a 15-km path seems to be feasible.

Abstract: The equations of motion of electrons subject to different combinations of electrostatic waves were integrated numerically. Magnetic fields were ignored throughout. For particular choices of wave amplitude, wavenumber, frequency, and phase, and for given initial velocities, there is calculated the mean‐square velocity spreading of a collection of particles subject to three different kinds of wave spectra: (a) a single monochromatic wave; (b) several (up to 10) monochromatic waves with differing phase velocities; and (c) a single wave with a random phase change at regular intervals. Heating occurs due to two basic effects: the “trapping” of particles, operative in all three spectra, and the spreading of the spectral density due to the random phase interruptions in (c). For the parameters chosen, numerical results are that the most efficient heating occurs in case (c).

Abstract: IN A SATELLITE COMMUNICATIONS SYSTEM OPERATING IN A TIME DIVISION MULTIPLE ACCESS MODE THE BURST TRANSMIT TIME AT EACH STATION IS VARIED IN ACCORDANCE WITH A PREDICTED PHASE ERROR. THE PREDICTED PHASE ERROR IS BASED ON PAST PHASE ERRORS, WHICH, OVER A SHORT PERIOD OF TIME INDICATE THE SUBSTANTIALLY LINEAR MOVEMENT OF THE SATELLITE AND THE SUBSTANTIALLY LINEAR VARIATION OF THE PHASE ERROR.