Phase measurement Research Papers - Academia.edu (original) (raw)

The concept of network-based real-time kinematic positioning has been extensively developed in order to better model the distance-dependent errors of GPS carrier-phase measurements. These errors can be separated into a frequency-dependent... more

The concept of network-based real-time kinematic positioning has been extensively developed in order to better model the distance-dependent errors of GPS carrier-phase measurements. These errors can be separated into a frequency-dependent or dispersive component (e.g. the ionospheric delay) and a non-dispersive component (e.g. the tropospheric delay and orbit biases). In fact, dispersive and non-dispersive errors have different dynamic effects on

The GPS double difference carrier phase measurements are ambiguous by an unknown integer number of cycles. High precision relative GPS positioning based on short observational timespan data, is possible, when reliable estimates of the... more

The GPS double difference carrier phase measurements are ambiguous by an unknown integer number of cycles. High precision relative GPS positioning based on short observational timespan data, is possible, when reliable estimates of the integer double difference ambiguities can be determined in an efficient manner. In this contribution a new method is introduced that enables very fast integer least-squares estimation of the ambiguities. The method makes use of an ambiguity transformation that allows one to reformulate the original ambiguity estimation problem as a new problem that is much easier to solve. The transformation aims at decorrelating the least-squares ambiguities and is based on an integer approximation of the conditional least-squares transformation. This least-squares ambiguity decorrelation approach, flattens the typical discontinuity in the GPS-spectrum of ambiguity conditional variances and returns new ambiguities that show a dramatic improvement in correlation and precision. As a result, the search for the transformed integer least-squares ambiguities can be performed in a highly efficient manner.

... manganese),[22,27–29] other studies have shown that not only the volume fraction but also the stability of retained austenite ... Austenite stability is commonly ascribed to different parame-... The heat-treatment scheme is... more

... manganese),[22,27–29] other studies have shown that not only the volume fraction but also the stability of retained austenite ... Austenite stability is commonly ascribed to different parame-... The heat-treatment scheme is schematically represented ...

A new approach to the absolute measurement of two-dimensional optical path differences is presented in this thesis. The method, which incorporates a white light interferometer and a hyperspectral imaging system, is referred to as... more

A new approach to the absolute measurement of two-dimensional optical path differences is presented in this thesis. The method, which incorporates a white light interferometer and a hyperspectral imaging system, is referred to as Hyperspectral Interferometry. A prototype of the Hyperspectral Interferometry (HSI) system has been designed, constructed and tested for two types of measurement: for surface profilometry and for depth-resolved displacement measurement, both of which have been implemented so as to achieve single shot data acquisition. The prototype has been shown to be capable of performing a single-shot 3-D shape measurement of an optically-flat step-height sample, with less than 5% difference from the result obtained by a standard optical (microscope) based method. The HSI prototype has been demonstrated to be able to perform single-shot measurement with an unambiguous 352 (m depth range and a rms measurement error of around 80 nm. The prototype has also been tested to perform measurements on optically rough surfaces. The rms error of these measurements was found to increase to around 4× that of the smooth surface. For the depth-resolved displacement field measurements, an experimental setup was designed and constructed in which a weakly-scattering sample underwent simple compression with a PZT actuator. Depth-resolved displacement fields were reconstructed from pairs of hyperspectral interferograms. However, the experimental results did not show the expected result of linear phase variation with depth. Analysis of several possible causes has been carried out with the most plausible reasons being excessive scattering particle density inside the sample and the possibility of insignificant deformation of the sample due to insufficient physical contact between the transducer and the sample

A double-periodic array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range. Such behavior results from the plasmon resonance in the pairs of nanorods for both the electric and the magnetic... more

A double-periodic array of pairs of parallel gold nanorods is shown to have a negative refractive index in the optical range. Such behavior results from the plasmon resonance in the pairs of nanorods for both the electric and the magnetic components of light. The refractive index is retrieved from direct phase and amplitude measurements for transmission and reflection, which are all in excellent agreement with simulations. Both experiments and simulations demonstrate that a negative refractive index n' approximately -0.3 is achieved at the optical communication wavelength of 1.5 microm using the array of nanorods. The retrieved refractive index critically depends on the phase of the transmitted wave, which emphasizes the importance of phase measurements in finding n'.

Surface plasmon resonance (SPR) is the excitation of cumulative charge oscillations in the metal-dielectric interface. Of the various surface plasmonbased measurement methods, phase-based measurement methods are the most accurate and... more

Surface plasmon resonance (SPR) is the excitation of cumulative charge oscillations in the metal-dielectric interface. Of the various surface plasmonbased measurement methods, phase-based measurement methods are the most accurate and sensitive. The wave phase can be measured with appropriate accuracy by various interferometry methods. The common path polarization heterodyne interferometry method compared to the conventional heterodyne method has the advantage of stability against changes in the ambient due to vibration and temperature changes. Increasing sensitivity has always been considered as one of the important challenges in designing and manufacturing various types of SPR-based sensors. In this study, after a theoretical investigation of enhancement of the phase sensitivity due to the addition of a quarterwave plate in the common path polarization heterodyne interferometer, the SPR phase change in the standard common path polarization heterodyne interferometer arrangement is measured. Comparing the results with the results of the modified setup proves the phase sensitivity enhancement. Experimental results show a sensitivity enhancement of at least 3.5 times.

Sine-fitting algorithms are very accurate methods to estimate the parameters (amplitude, phase, frequency and DC component) of a digitized sinusoidal signal. In this paper, the standardized algorithms are improved, producing a new... more

Sine-fitting algorithms are very accurate methods to estimate the parameters (amplitude, phase, frequency and DC component) of a digitized sinusoidal signal. In this paper, the standardized algorithms are improved, producing a new algorithm to estimate the sinewave parameters of two acquired sine signals sharing a common frequency. This new algorithm can be used for example in impedance measurements or in

Three-dimensional imaging provides profile information not available with conventional two- dimensional imaging. Many three-dimensional objects of interest are opaque to the illuminating radiation, meaning that the object exhibits... more

Three-dimensional imaging provides profile information not available with conventional two- dimensional imaging. Many three-dimensional objects of interest are opaque to the illuminating radiation, meaning that the object exhibits surface, as opposed to volume, scattering. We inves- tigate the use of an opacity constraint to perform three-dimensional phase retrieval. The use of an opacity constraint in conjunction with frequency-diverse pupil-plane

In comparing the similarity between time, frequency, and phase measurements as used in the induced polarization method of geophysical prospecting, parameters must first be defined and the basis for comparison established. The conditions... more

In comparing the similarity between time, frequency, and phase measurements as used in the induced polarization method of geophysical prospecting, parameters must first be defined and the basis for comparison established. The conditions for mathematical equivalence then follow in a natural sequence. Laboratory measurements are made on a variety of rock samples to indicate the type of comparison and correlation expected from field measurements.Results indicate that frequency domain and phase measurements are equivalent, but two frequency domain measurements are needed to produce the same amount of polarization information as a single phase measurement. Frequency and time domain measurements will be similar but never equivalent due to the basic differences in their respective parameter definitions.

This paper introduces a new method for measuring cortical excitability using an electrical probing stimulus via intracranial electroencephalography (iEEG). Stimuli consisted of 100 single bi-phasic pulses, delivered every 10 minutes.... more

This paper introduces a new method for measuring cortical excitability using an electrical probing stimulus via intracranial electroencephalography (iEEG). Stimuli consisted of 100 single bi-phasic pulses, delivered every 10 minutes. Neural excitability is estimated by extracting a feature from the iEEG responses to the stimuli, which we dub the mean phase variance (PV). We show that the mean PV increases with the rate of inter-ictal discharges in one patient. In another patient, we show that the mean PV changes with sleep and an epileptic seizure. The results demonstrate a proof-of-principal for the method to be applied in a seizure anticipation framework.

In-line digital holographic microscopy as a phase measurement tool for the inspection of micro-components is presented. Light diffracted by the micro-components interferes with the directly propagating beams to give the in-line digital... more

In-line digital holographic microscopy as a phase measurement tool for the inspection of micro-components is presented. Light diffracted by the micro-components interferes with the directly propagating beams to give the in-line digital hologram recorded by the CCD camera. The convolution method is used to calculate the diffractive propagation of the light in order to reconstruct the wavefront of the test specimen. A reference hologram without the test specimen is recorded for the phase reconstruction. Finally, the method is applied on a phase grating to test its refractive index of the coating material.

The concept of network-based positioning has been extensively developed in order to better model the distance-dependent errors of GPS carrier-phase measurements. These errors can be separated into a frequency-dependent or dispersive... more

The concept of network-based positioning has been extensively developed in order to better model the distance-dependent errors of GPS carrier-phase measurements. These errors can be separated into a frequency-dependent or dispersive component (e.g. the ionospheric delay) and a non-dispersive component (e.g. the tropospheric delay and orbit biases). In fact, dispersive and non-dispersive errors have different dynamic effects on the GPS

Gas and volatile organic compounds (VOCs) release in soil is known to be linked to microbial activity and can differently affect the life of organisms in soil. Electronic noses (E-noses) are sensing devices composed of sensor arrays able... more

Gas and volatile organic compounds (VOCs) release in soil is known to be linked to microbial activity and can differently affect the life of organisms in soil. Electronic noses (E-noses) are sensing devices composed of sensor arrays able to measure and monitor ...

A comparative study of the use of X- and S-band polarimetric radars for rainfall parameter retrievals is presented. The main advantage of X-band polarimetric measurements is the availability of reliable specific differential phase shift... more

A comparative study of the use of X- and S-band polarimetric radars for rainfall parameter retrievals is presented. The main advantage of X-band polarimetric measurements is the availability of reliable specific differential phase shift estimates, KDP, for lighter rainfalls when phase measurements at the S band are too noisy to produce usable KDP. Theoretical modeling with experimental raindrop size distributions indicates that due to some non-Rayleigh resonant effects, KDP values at a 3.2-cm wavelength (X band) are on average a factor of 3.7 greater than at 11 cm (S band), which is a somewhat larger difference than simple frequency scaling predicts. The non-Rayleigh effects also cause X-band horizontal polarization reflectivity, Zeh, and differential reflectivity, ZDR, to be larger than those at the S band. The differences between X- and S-band reflectivities can exceed measurement uncertainties for Zeh starting approximately at Zeh > 40 dBZ, and for ZDR when the mass-weighted d...