Constant Phase Shift Research Articles

Phase relationships of cortical potentials in rabbits during motor reactions.

1. The phase relationships involved in biopotential oscillations between the sensorimotor and visual regions during background activity in rabbit cerebral cortex are characterized by the presence of a significant spread (from 26 to 45°). 2. Light stimulation increases the number of synpasic biopotential oscillations at closely positioned sites in the cortex and decreases the spread in values of the phase shift between oscillations in the sensorimotor and visual regions of the cortex, i.e., makes the phase shifts more stable. 3. EEG of the sensorimotor and visual regions of the cortex recorded during motor reactions of rabbits in response to light stimulation exhibit theta-rhythm waves with a maximally constant phase shift.

A simple modification of Broom's transformation for linear-phase FIR filters

A modification in the low-pass to bandpass transformation formulated by Broom [1] has been proposed; this is shown to transform a linear-phase low-pass FIR filter to a bandpass filter with approximately linear-phase characteristic and with a constant phase shift θ, where θ can be chosen as desired. When θ is chosen to be zero or π/2, the transformed bandpass filter becomes strictly linear phase.

Circadian Sleep and Temperature Rhythms in the Domestic Cat under Constant Light and Phase Shift Conditions

Circadian Sleep and Temperature Rhythms in the Domestic Cat under Constant Light and Phase Shift Conditions

FIR interferometer/polarimeter system on ISX-B tokamak

Recent results of simultaneous measurements of electron density and Faraday rotation on all five channels of the FIR interferometer/polarimeter system on ISX-B are presented. The time resolution of the interferometer is typically 1 μs. The standard deviation of the output of the interferometer of a constant phase shift is less than 5×10−2 fringe, corresponding to a line electron density of 5×1011 cm−3. The polarimeter shows a sensitivity of the order of 1 mrad and a time resolution of approximately 1 ms. Data are reported on ohmic as well as neutral-beam-heated plasmas including solid hydrogen pellet injections. It is believed that this is the first successful measurement of Faraday rotation in pellet-injected discharges. Data analysis codes have been developed and the results are being compared with other measurements.

Lateralization of low‐frequency tones and narrow bands of noise

It is well known and universally accepted that people's ability to use ongoing interaural temporal disparities conveyed via pure tones is limited to frequencies below 1600 Hz. We wished to determine if this limitation is the result of the constant amplitude and periodic axis crossings which characterize pure tones. To this end, we employed an acoustic pointing task in which listeners varied the interaural intensitive difference of a 500‐Hz narrow‐band noise (the pointer) so that it matched the intracranial position of a second, experimenter‐controlled, stimulus (the target). Targets were either pure tones or narrow bands of noise (50 or 100 Hz wide). The narrow bands of noise were delayed interaurally in two distinct manners. We delayed either the entire waveform or only the carrier. In the latter case, the envelopes and phase functions were identical. This resulted in a noise which resembles the pure tone case in that the interaural delay is manifested as a constant phase shift and resembles the ordinary noise in that the envelope and phase are random functions of time. Surprisingly, it appears that all three targets were lateralized virtually identically regardless of frequency or bandwidth. Apparently, the dynamically changing envelopes and phases did not effect the listeners' use of interaural temporal disparities in any discernable fashion.

The least squares estimation of time delay between two signals with unknown relative phase shift

This correspondence addresses the problem of time delay estimation between two signals with an unknown constant relative phase shift. The method of time delay estimation for the pure delay case of Chan et al. [1] is applied here to derive the least squares estimator (LSE). An explicit expression for the LSE of the delay is obtained which is computationally less complex than the maximum likelihood estimator (MLE) [2]. It is shown that the LSE is unbiased, and that the mean-square error or the LSE is asymptotically equivalent to that of the pertinent MLE.

Phase-shift gradients of dominant cortical potentials in rabbits

Phase shifts of cortical potentials were studied in rabbits before and during photic stimulation and their importance for irradiation of excitation from the visual to the motor area was examined. Both before and during stimulation variations in phase relationships of various kinds were observed. In most cases, however, with an increase in distance between the electrodes, the phase shift of the theta-waves gradually increased. Most motor responses of the rabbits took place in the presence of a marked phase shift gradient. It is suggested that the state of the brain in which a spatial phase shift gradient of the theta-waves is recorded in the EEG is the optimal condition for realization of the motor response. Photic stimulation increases the number of in-phase waves in the EEG recorded from closely situated points and it reduces scatter of the phase shift values between components of the sensomotor and visual cortical EEG, i.e., it leads to an increase in coherence. Motor responses of the rabbits to stimulation take place in the presence of theta-waves with the most constant phase shift in the EEG of the sensomotor and visual cortex.

The Role of AM-to-PM Conversion in Memoryless Nonlinear Systems

A generalized proof is presented that AM-to-PM conversion can only degrade, never improve, the intermodulation-noise performance of memoryless nonlinear systems with random input signals having even probability density functions, and a measure of degradation is defined. It is also shown for such signals that AM-to-PM conversion causes a deterministic constant phase shift to be added to the argument of the signal component at the output but has no other effect on its phase. This class of inputs includes one or the sum of several PSK signals, as well as large ensembles that can be modeled as Gaussian noise. The latter are dealt with by using Bussgang's theorem on input-output cross correlation. In the proof, Bussgang's theorem is extended to the complex case, to include phase as well as amplitude nonlinearities, yielding a complex version of the theorem. For Gaussian inputs it is shown that the undistorted signal and the intermodulation noise at the output of such systems are uncorrelated.

Bulk acoustic wave integrated optical deflector and monolithic A/D converter using such deflector

Method and apparatus is described for interacting bulk acoustic waves with an optical waveguide on a common substrate to switch, modulate or deflect guided light at a very high speed. A direct application lies in a monolithic optical analog-to-digital converter. To this effect, a plurality of transducer elements regularly spaced in an array across the optical waveguide are controlled with constant or variable phase shift along a slope, thus causing deflection of the guided light in a fashion analog to phased-array radar technique. A fully integrated monolithic device is constructed combining the bulk acoustic wave generating and optical waveguide functions.

Synthesis of wideband lumped planar directional couplers

A synthesis procedure of wideband lumped directional couplers is presented. The four-port network is separated, using even- and odd-mode excitations, into two pairs of two-port networks with constant phase shift between them. It is shown that to attain wideband matching as well as constant in-band coupling, the two modal two-port networks should not only be matched, but have a constant phase shift between them as well. These restrictions are best met with two ideal linear-phase bandpass filters that are mutually frequency shifted. The lack of detailed lowpass prototype (LPPT) tables for such filters led, in the paper, to an alternative synthesis procedure, which includes recursive optimisation. A design example is given.

Calculation of the adjoint masses for an annular blade assembly

It is necessary to know the adjoint-mass coefficients in order to solve various problems in turbine aeroelasticity such as the calculation of the natural frequencies and forms of blade vibrations. These coefficients are known only for the planar set of plates, so interest attaches to estimating the effects of the three-dimensional flow on their magnitudes. Here the authors consider the adjoint masses for a three-dimensional ring set of thin blades performing small harmonic oscillations with a constant phase shift in an incompressible fluid.

Unity-gain frequency-independent precision phase-shifter

The letter describes an operational amplifier circuit which gives a constant (±0.1°) phase shift and a constant (±0.1%) unity gain to a sinusoidal signal, over a frequency band of range ±2%. The circuit incorporates two standard phase-shifters with different characteristics, deployed so that their phase errors mutually cancel as the frequency deviates from its central value. The device has been used as a phase-shifter in a precise negative phase sequence current measurement circuit in a power system.

Unity-gain frequency-independent quadrature phase shifter

An active circuit which simultaneously provides unity gain and a Constant phase shift of 90° for sinusoidal inputs of varying frequency is described. It employs the voltage derived from a quadrature detector to modify the resistance of a voltage-controlled resistor incorporated in an active allpass phase shifter circuit.

On three-dimensional acoustic-gravity waves in model non-isothermal atmospheres

The propagation of acoustic-gravity waves is studied in a family of model non-isothermal atmospheres, including temperature profiles with any initial and asymptotic temperature and adjustable maximum temperature gradient. The equation for the vertical velocity of linear acoustic-gravity waves is solved exactly in terms of hypergeometric functions, the wave field being described to all orders in the scattering parameter kL, at all frequencies and distances, including wavelengths comparable to the scale of temperature change and atmospheric layers with a large temperature gradient. It is found that since the temperature is bounded, in the asymptotic regime waves grow in amplitude exponentially and phase increases linearly with altitude. The growth in amplitude is larger than exponential and the phase increases faster than linearly for atmospheres whose temperature increases with altitude, the effect being more marked for high frequency waves in regions of large temperature gradients. The accumulation of these effects leads to a wave field which is equivalent to the isothermal case at asymptotic temperature modified by a constant amplitude factor and phase shift which account for the history of propagation of the wave through the temperature gradients.

Common amplification of one large signal and small signals in a memoryless non-linear band-pass amplifier

Common amplification of one largo signal and small signals in a bandpass non-linear amplifier with amplitude non-linearity and AM/PM conversion is analysed using a simple, general approach. Despite the amplifier non-linearities and the strong interfering signal, the weak signal emerges undistorted, suffering only a constant phase shift. The analysis yields also the output intermodulation products of any order.

Sound radiation by a plate reinforced by a set of projecting stiffener ribs subjected to a periodic system of forces

There is considered sound radiation by a plate reinforced by a periodic set of projecting stiffener ribs of small wave dimensions. The source of the field is a set of lumped harmonic forces applied to the plate periodically in each transit, where the forces are taken identical in amplitude but with a constant phase shift between adjacent sources. The problem reduces to a quasiregular infinite system of linear algebraic equations, in terms of whose solution the energy fluxes leaving the plate into the fluid are expressed.

Circadian phase response curves for dark pulses in the hamster

Hamsters maintained under constant illumination were exposed to 2- or 6-h pulses of darkness at various phases of their circadian activity rhythms. When presented around the time of activity onset, the pulses resulted in phase advances, and when presented toward the end of daily activity, they resulted in phase delays. Since others have shown that light pulses presented at the same phases in constant darkness cause phase shifts in the opposite directions, these results indicate that phase response curves for light and dark pulses are mirror images.

Echo phase perception in bat sonar?

The bat Eptesicus fuscus is apparently sensitive to the fine structure of the autocorrelation function of its transmitted pulse. This sensitivity has been interpreted as evidence for phase perception in bats at ultrasonic frequencies. An alternative interpretation of the data, however, does not depend upon phase perception. The observed sensitivity to autocorrelation fine structure can be explained by a process that involves cross correlation of filtered spectrograms. Spectrogram representations are insensitive to a constant phase shift.

The Effect of a Large Signal Upon a Small Signal in a Memoryless Nonlinear Bandpass Amplifier

Despite the presence of AM-to-AM conversion, AM-to-PM conversion, and a strong interfering signal, a weak signal emerges undistorted from a memoryless nonlinear bandpass amplifier, suffering only a constant phase shift. A recent result of Chang and Shimbo concerning this situation is here clarified with the aid of a simpler, more direct derivation, which also yields the third-order intermodulation.

Evolution of shock waves in a one-dimensional lattice

A normal impact problem for a lattice is considered. A solution is formulated for an arbitrary interaction potential between particles at the two impact ends and simple linear force interaction between particles within each lattice. Asymptotic response of a lattice to impact with truncated interaction and to different end accelerations applied to achieve a shock velocity are considered and related to the response to a step jump in velocity. The essential difference in the asymptotic head of the pulse response for different shock excitations is a constant phase shift in the arrival time of the dispersive oscillations relative to the step jump response. Then, weakly nonlinear interactions of quadratic form are considered within a lattice. A modification is made for the far-field evolution equation previously obtained [J. Appl. Phys. 44, 4569 (1973)] for the asymptotic first-order frequency dispersion and nonlinear response to a step jump in velocity. Comparison is made with numerical solutions of the lattice equations of motion and the differences are discussed. For different end accelerations applied to achieve a shock velocity, the asymptotic nonlinear dispersive oscillations are determined by a phase shift in response relative to the nonlinear response to a step jump in velocity. The amount of the phase shift is the same as in the case of linear interaction.