Electrical Phase Shift Research Articles

Operation modes of a liquid-crystal modal wave-front corrector.

Liquid-crystal modal wave-front correctors provide much better wave-front correction than do piston correctors with the same number of actuators; moreover, use of additional degrees of freedom of the driving ac voltage signals may further improve device performance. Some practical aspects of the operation of liquid-crystal modal wave-front correctors are discussed. Special attention is paid to the interference of various contact responses and to the formation of required phase shapes through wider control of signal frequencies and electric phase shifts. The study is based on an analytic approach and numerical investigation; major theoretical conclusions are verified experimentally.

High-frequency response of aD-fiber antenna using finite-element analysis intended for radio-over-fiber applications

An all-fiber antenna using piezoeletric polymer-coated circular core D-fiber has been characterized using finite-element analysis. The response of the D-fiber antenna was determined oiler a wide frequency range from 1 to 600 MHz. The modeling predicts an electric field-included phase shift of 0.00173 rad/V/m at 1 MHz. (C) 2000 John Wiley & Sons, Inc.

Effects of anodized aluminium surface parameters on the long-term adhesion of silicone structural glazing sealants

The quality of silicone sealant adhesion to anodized aluminium varies widely. Key parameters that affect adhesion are the degree of surface sealing, the pigmentation of the anodization layer, the nature of the cleaner, and the time period allowed between cleaning the substrate and sealant application. While the cleaners display different effectiveness in removing organic contamination from the anodized aluminium surface, this effectiveness does not correlate with adhesion quality. It is hypothesized that by absorbing on the anodized aluminium substrate the cleaning solvents ‘condition’ the surface for improved silicone sealant adhesion. This conditioning effect diminishes, as the cleaning solvents desorb over time. For a given cleaning solvent, optimum adhesion is observed for a certain degree of surface sealing. Adhesion to unpigmented anodized aluminium substrates can be predicted by measuring the degree of surface sealing according to the ISO 2143 acid etch method. For pigmented anodized aluminium substrates, electrical phase shift measurements, made in accordance with the ISO 2931 test standard, can be used to predict adhesion quality. A quality control method for anodized aluminium surfaces is proposed that allows successful correlation of the electrical impedance measured at various frequencies with the long-term adhesion of silicone sealants to this surface.

Extended-range pseudo-heterodyne demodulation using electrical phase characteristics of all-pass filters

This paper describes two demodulation methods that have been developed for extracting large optical phase changes from pseudo-heterodyne modulated optical-fiber sensor signals. Both demodulator approaches use frequency-dependent electrical phase shifts in an electrical all-pass filter, and differ only in how the electrical phase is extracted from the all-pass filter. One approach uses a summing amplifier and a peak detector, while the other uses a phase meter. Both proved capable of detecting optical phase changes greater than 100 radians, which is far in excess of previous pseudo-heterodyne techniques, but this is achieved at the expense of DC measurement capability. Additionally, the peak detector demodulator and phase meter demodulators had minimum detectable phases of 5*10-4 radians and 1*10-5 radians, respectively, over a 2.0 kHz bandwidth.

A new approach to compute the resultant pressure of linear array

In this paper, a new calculation scheme is proposed to compute the nearfield and the farfield directivity pattern of such arrays including interactions and without assumptions concerning the displacement field of the transducer radiating surface. For this purpose, using the finite element method (FEM), the farfield directivity pattern of a part of the array (2Q +1 transducers) is computed using dipolar dampers and a previous described extrapolation algorithm [Assaad etal., J. Acoust. Soc. Am. 94, 562–573 (1993)]. This part consists of an active elementary transducer (electrically driven) mounted between 2Q passives (electrically grounded) neighboring transducers. Then, the radiation field of a finite phased and focused array (N elements) can be obtained by summing up the farfield directivity patterns of the 2Q + 1 transducer sets weighted by the classical term used to take account of the geometrical and electrical phase shifts.

Ferroelectric phase shifters and their performance in microwave phased array antennas

Abstract Recent advances in the development of Barium Strontium Titanate ferroelectric composition has made possible reasonable performance of ferroeletric phase shifters to frequencies up to 10 GHz. These material improvements, coupled with phase shifter circuit design changes have resulted in phase shifts greater than 360 degrees with less than 6 dB insertion loss. In particular additives to the BaxSr1-xTiO3 composition have been shown to exhibit a consistent electrical phase shift verses DC potential over parameters of temperature and humidity. These ferroelectric material improvements and circuit design changes, included with the development of multiple ferroelectric phase shifters makes possible the fabrication of a low cost electronic scanning antenna. A single four element phase shifter was used with a one dimensional linear antenna array which was constructed on three layers and used an aperture coupled distribution technique. Individual elements of this multiple four element phase shifter were evaluated with respect to uniformity phase shift and insertion loss. The four element antenna was fed by four ferroelectric phase shifters and the phase shifters are corporately fed by the microwave source. The ferroelectric phase shifters are controlled via a dedicated microcontroller which calibrates out element phase variations and provides a real time scan capability for the antenna assembly.

Fiber-optic circuit for direct phase conversion with two outputs in quadrature

The authors model and demonstrate a fiber-optic circuit configuration that maps optical phase shifts into electrical phase shifts in the fundamental and second harmonics of an imposed modulation frequency. This optical circuit allows simple electronic phase detectors to extract these phase shifts, which are demonstrated to be linear over a full 2 pi radians, opposite in slope, and offset by pi /2 from each other in a phase relation similar to quadrature.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An integrable capacitive angular displacement sensor with improved linearity

Abstract A novel type of high-resolution absolute angular encoder is presented. The operation is based on the capacitive coupling between four driving electrodes on a stator and a rotor electrode. The four driving electrodes are connected to four sinusoidal voltages with equal amplitudes and relative phase differences of 90 degrees. A sinusoidal voltage arises on the rotor electrode, which is due to the capacitive coupling of these voltages and results in a phase shift that depends on the angle of rotation. The voltage on the rotor is capacitively coupled back to the pick-up electrode on the stator to enable a contactless measurement to be made. In this way a dimensionless transduction of the angle of rotation of the rotor with respect to the stator into an electrical phase shift is possible. This transduction can be linearized by means of a special patterning of the driving electrodes. The resolution of the phase measurement is usually the limiting factor, so an improved sensor structure has been designed with a high-resolution incremental encoder part combined with a low-resolution absolute encoder structure. The combined operation results in a high-resolution absolute angular encoder. The rotor should be aligned with respect to the stator for proper operation of the sensor and an alignment technique is implemented, which is based on the same principle as that used in the sensor and gives information on both the magnitude and the direction of the misalignment, thus enabling automatic alignment to be carried out during assembly. The main source of error is buckling of the sensor parts.

Phase-modulated fiber optic gyroscope with wide dynamic range and linear scale factor

An open-loop phase-modulated fiber optic gyroscope with a wide dynamic range and linear scale factor is described. The optical Sagnac phase shift is transposed into an electrical phase shift by introducing two phase sensitive detectors and two electronic amplitude modulators with independent carrier frequency from the optical phase modulation. Preliminary experiments show good linearity over a wide dynamic range up to 1000 degrees /s and verifies the theoretical prediction.

Design of Phase Shifters for a Group Type Unidirectional Transducer

A group type unidirectional transducer (GUT) is useful for a low loss SAW filter. The four-port and two-port network expressions for the GUT are presented, and interaction between the inphase and quadrature ports is revealed analytically. The conditions for perfect unidirectivity are also described. The design procedures of the electrical phase shifters performing perfect unidirectivity are shown both in series and parallel configurations for any geometrical phase shift except π.

Piezoelectric copolymer jacketed single-mode fibers for electric-field sensor application

Characteristics of a piezoelectric copolymer jacketed optical fiber are presented. The jacket consisting of a copolymer of vinylidene fluoride and trifluoroethylene was made piezoactive by corona poling. The performance of the fiber as an optical-phase modulator was demonstrated over a frequency range of 20 Hz–5 kHz. An electric field-induced phase shift of 1.5×10−7 rad/(V/m) per meter of fiber was measured in the low-frequency (axially unconstrained) region. Several resonance peaks in optical phase shift were observed and discussed in conjunction with piezoelectricity in polymer jackets.

Scattering of electromagnetic radiation in terms of functions over the group SU2

Carmeli's group theoretical analysis of Maxwell's Equations, in which the field variables are considered as functions over the group SU 2, is extended to the general formulation of the problem of scattering of electromagnetic waves. The relevant complex functions, defined over the group SU 2, are explicitly given in terms of electric and magnetic phase shifts. They are shown to have a simple physical meaning in the far zone. The general expressions for the differential and total cross sections are defined. The differential cross section is shown to be the sum of two non-interfering spherical waves, which can be considered as the spherical wave analogue of the positive and negative helicities of plane waves.

Time Resolution of Photoluminescent Spectra by Phase Controlled Chopping

In the study of photoluminescence, simple spectra obtained by dc excitation often do not contain sufficient information for complete analysis of the kinetics of the luminescent light emission. This paper describes a system with which the spectral emission can be studied at controlled times after photoexcitation. The system uses separate mechanical chopping of the photoexcitation source and the photoluminescent emission. The two light choppers are hysteresis synchronously driven from a single alternating current source and their relative positions are, therefore, phase locked. Their relative positions and, therefore, the time between termination of photoexcitation and detection of photoluminescent emission is controlled by a 0–360° precision electrical phase shifter placed between the common alternating current source and the power amplifier driving one of the chopper motors. This time controlled system is described. The photoluminescence is wavelength resolved by a spectrometer, detected by a photomultiplier and lock-in amplifier, and automatically recorded as a function of wavelength by an X-Y recorder. X-Y recorded tracings of photoluminescent spectra at various times after termination of photoexcitation are shown to illustrate the capabilities of the system.

Resonant Electrical Control Systems

The electrical phase shift between the current and the applied voltage in a series-resonant circuit as the resonant-circuit tuning is varied is used as the basis of operation for resonant electrical control systems. The author discusses application of such systems to aircraft and industrial problems, and to single and multiphase radio control.

Resonant electrical control systems

The electrical phase shift between the current and the applied voltage in a series-resonant circuit as the resonant-circuit tuning is varied is used as the basis of operation for resonant electrical control systems. The author discusses application of such systems to aircraft and industrial problems, and to single and multiphase radio control.