Precise Phase Measurements Research Articles

The Analysis and Validation of Two-dimensional Attitude Measurement with GPS

Global Positioning System (GPS) is more and more being used in the attitude measurement, the error accumulates over time and the accuracy of the system can’t be ensured after a long time, the GPS has the performance of effective real-time and stability in accuracy through the application of the GPS measurement of attitude in resolving. After determining the attitude of carriers using measured carrier phase of GPS,solving the carrier phase ambiguitie problem, Real-time attitude determination is derived from extremely precise differential carrier phase measurements among GPS antennas mounted on the vehicle.A simple and efficient way to determine the attitude,use the GPS OEM boards,carrier phase difference method,QR decomposition algorithm.The feasibility and applicability of the design are validated through experiments.The results show that:the method can get the attitude in a short time and is of higher accurate.

New method for single epoch, single frequency land vehicle attitude determination using low-end GPS receiver

Stand-alone, unaided, single frequency, single epoch attitude determination is the most challenging case of GNSS compass processing. For land vehicle applications, the baseline approximately lies in the plane of the local geodetic horizon. This provides an important constraint that can be exploited to directly aid the ambiguity resolution process. We fully integrate the constraint into the observation equations, which are transformed orthogonally. Our method can acquire the high-quality float solution by means of a heading search strategy. The fixed solution is obtained by weighted constrained integer least squares for each possible heading. The correct solution is identified by three consecutive steps: Kolmogorov–Smirnov test, heading verification, and global minimizer of the fixed ambiguity objective function. The analysis focuses on single frequency, single epoch land vehicle attitude determination using low-end GPS receivers with very low precision of carrier phase and code measurements. The error analysis is given for choosing a proper baseline length in practical application. Experimental results demonstrate that this scheme can improve the ambiguity success rate for very short baseline.

A highly phase-stable differential detector amplifier for magnetic induction tomography

Magnetic induction tomography (MIT) has been proposed for the detection of cerebral oedema and haemorrhagic stroke. Achieving the required phase measurement precision for these applications is however a major technical challenge. A critical component within an MIT system is the detector amplifier and for this role an ultra-phase-stable, low noise instrumentation amplifier has been developed. The design of the amplifier is described and (i) the results of simulations and measurements of the amplifiers phase stability versus temperature and (ii) measurements of the phase noise and drift performance of the amplifier within a single-channel magnetic induction spectroscopy system are provided and discussed. For a 10 MHz signal the amplifier, with a gain of 21, displayed an average change in the measured phase of its output of just −0.1 ± 0.6 m° °C–1 as the ambient temperature was varied between 35 and 50 °C, demonstrating a level of phase stability approaching that required for potential biomedical applications such as the detection of cerebral haemorrhage.

High precision phase measurement technique for cell impedance spectroscopy

This paper presents a new approach for high precision phase measurement. The new system is developed for biomedical applications such as complex cell impedance measurement and dielectric tissue analysis. In many of the named applications it is necessary to measure the complex dielectric constant of a sample as a function of frequency. Therefore the developed system is capable of measuring amplitude and especially high precision phase of the measurement signal over a wide frequency range from 10 Hz to 10 MHz. The experimental result of the new method shows a phase resolution of up to 0.01 degree at 1 MHz and 0.1 degree at 10 MHz. The excellent phase measurement resolution is achieved by a time transformation of the signal using a digital sampling circuitry. The functional principle of the digital sampling circuitry is based on Delta – Modulation and is implemented inside a cheap standard FPGA. The new system is successfully used in blood analysis applications and allows for a practical implementation of cost efficient capacitive hematocrit sensors for the first time.

Carrier Phase Relative RAIM Algorithms and Protection Level Derivation

The concept of Relative Receiver Autonomous Integrity Monitoring (RRAIM) using time differential carrier phase measurements is investigated in this paper. The precision of carrier phase measurements allows for mitigation of integrity hazards by implementing RRAIM monitors with tight thresholds without significantly affecting continuity. In order to avoid the need for cycle ambiguity resolution, time differences in carrier phase measurements are used as the basis for detection. In this work, we examine RRAIM within the context of the GNSS Evolutionary Architecture Study (GEAS), which explores potential architectures for aircraft navigation utilizing the satellite signals available in the mid-term future with GPS III. The objectives of the GEAS are focused on system implementations providing worldwide coverage to satisfy LPV-200 operations, and potentially beyond. In this work, we study two different GEAS implementations of RRAIM. General formulas are derived for positioning, fault detection, and protection level generation to meet a given set of integrity and continuity requirements.

Modelling of ionospheric high-order errors for new generation GNSS

In dual frequency Global Positioning System receivers, the ionospheric propagation delays are commonly estimated and corrected using the “ionosphere free” combinations of pseudo-range observables. With this method, the ionospheric delay is estimated at the first-order proportional to the inverse of the frequency square. However, higher-order terms exist that may be taken into account when precise corrections are required. The second-order term results from the influence of the geomagnetic field on the ionospheric propagation of the signals. The third-order term includes the refractive effects due to the bending of the ray. Contributions of the second- and third-order terms typically amount to values in the centimetre and millimetre ranges, respectively. In a near future, triple-frequency Global Navigation Satellite Systems transmitting high-resolution codes will become available. These systems are expected to provide a noticeable improvement in accuracy. This paper focuses on the Galileo signals as Galileo In-Orbit Validation Element (GIOVE) signals are now available for acquisition. A solution relying on the triple-frequency characteristics of a signal-in-space is investigated with results based on first measurements of GIOVE-A signals. Eventually, a method is described that relies on precise dual-frequency phase measurements to evaluate the second-order ionospheric contribution for Galileo data.

Fringe extrapolation technique based on Fourier transform for interferogram analysis

A new fringe extrapolation method for extracting phase from fringe patterns is presented. The proposed method can be used to reduce the errors at the border of the pattern. The simulation was carried out considering the random noise. The result of the simulation shows that this method is effective for precision phase measurement. The experimental result for the fringe extrapolation method is compared with the result of the Fourier transform method without using the extrapolated interferogram patterns.

Closure phase studies toward direct detection of light from hot Jupiters

AbstractPrecision closure phase measurements obtained with ground-based long baseline optical interferometers is a promising way to directly detect light from nearby hot Jupiters. Here we present our closure phase simulations for the CHARA array for several bright hot Jupiters, υ And b, 51 Peg b, and τ Boo b. The maximum possible closure phase signals from these hot Jupiters are very small, for example, only ∼0.17 degrees for υ And b, requiring very high precision and stable closure phase measurements. We present preliminary results of a closure phase study on test object β Tau and hot Jupiter system υ And, both obtained with the MIRC instrument at the CHARA array. We demonstrate that directly detecting the light from hot Jupiters is feasible using high precision closure phase measurements obtained by CHARA-MIRC along with its sub-milli-arcsecond resolution, although challenges remain.

Loss-induced limits to phase measurement precision with maximally entangled states

The presence of loss limits the precision of an approach to phase measurement using maximally entangled states, also referred to as NOON states. A calculation using a simple beam-splitter model of loss shows that, for all nonzero values L of the loss, phase measurement precision degrades with increasing number N of entangled photons for N sufficiently large. For L above a critical value of approximately 0.785, phase measurement precision degrades with increasing N for all values of N. For L near zero, phase measurement precision improves with increasing N down to a limiting precision of approximately 1.018 L radians, attained at N approximately equal to 2.218/L, and degrades as N increases beyond this value. Phase measurement precision with multiple measurements and a fixed total number of photons N_T is also examined. For L above a critical value of approximately 0.586, the ratio of phase measurement precision attainable with NOON states to that attainable by conventional methods using unentangled coherent states degrades with increasing N, the number of entangled photons employed in a single measurement, for all values of N. For L near zero this ratio is optimized by using approximately N=1.279/L entangled photons in each measurement, yielding a precision of approximately 1.340 sqrt(L/N_T) radians.

Single epoch ambiguity resolution for Galileo with the CAR and LAMBDA methods

This paper investigates single epoch ambiguity resolution performance using Galileo four frequency data. Two commonly used ambiguity resolution methods are used in the tests, including the Cascade Ambiguity Resolution (CAR) and the Least-Squares Ambiguity Decorrelation Adjustment (LAMBDA) methods. For CAR method, four optimal combinations are carefully selected according to their wavelength to noise ratios and success rate for ambiguity fixing. The test results show, in general, the LAMBDA method performs better than the CAR method. The speed of ambiguity resolution is closely related to the carrier phase measurement precision. With carrier phase measurement precision of 3 mm, single epoch ambiguity resolution can be achieved at every epoch with simulated 1-s interval 24-h Galileo data (total epochs 86,400). With the increase of carrier phase noise, ambiguity resolution performances become worse. When the noise level is increased to 12 mm, single epoch ambiguity resolution can only be achieved about 50% of epochs.

Adiabatic Mach-Zehnder Interferometry on a Quantized Bose-Josephson Junction

We propose a scheme to achieve Mach-Zehnder interferometry using a quantized Bose-Josephson junction with a negative charging energy. The quantum adiabatic evolution through a dynamical bifurcation is used to accomplish the beam splitting and recombination. The negative charging energy ensures the existence of a path-entangled state which enhances the phase measurement precision to the Heisenberg limit. A feasible detection procedure is also presented. The scheme should be realizable with current technology.

Observation of the four-photon de Broglie wavelength by state-projection measurement

A measurement process is constructed to project an arbitrary two-mode $N$-photon state to a maximally entangled $N$-photon state (the {\it NOON}-state). The result of this projection measurement shows a typical interference fringe with an $N$-photon de Broglie wavelength. For an experimental demonstration, this measurement process is applied to a four-photon superposition state from two perpendicularly oriented type-I parametric down-conversion processes. Generalization to arbitrary $N$-photon states projection measurement can be easily made and may have wide applications in quantum information. As an example, we formulate it for precision phase measurement.

Spinor dynamics-driven formation of a dual-beam atom laser

We demonstrate a novel dual-beam atom laser formed by outcoupling oppositely polarized components of an all-optical F = 1 spinor Bose-Einstein condensate whose Zeeman sublevel populations have been coherently evolved through spin dynamics. The condensate is formed through all-optical means using a single-beam running-wave dipole trap. We create a condensate in the magnetic field-insensitive m(F) = 0 state, and drive coherent spin-mixing evolution through adiabatic compression of the initially weak trap. Such dual beams, number-correlated through the angular momentum-conserving reaction 2m(0) ?m(+1) +m(-1), have been proposed as tools to explore entanglement and squeezing in Bose-Einstein condensates, and have potential use in precision phase measurements.

Sub-shot-noise phase sensitivity with a Bose-Einstein condensate Mach-Zehnder interferometer

Bose Einstein Condensates, with their coherence properties, have attracted wide interest for their possible application to ultra precise interferometry and ultra weak force sensors. Since condensates, unlike photons, are interacting, they may permit the realization of specific quantum states needed as input of an interferometer to approach the Heisenberg limit, the supposed lower bound to precision phase measurements. To this end, we study the sensitivity to external weak perturbations of a representative matter-wave Mach-Zehnder interferometer whose input are two Bose-Einstein condensates created by splitting a single condensate in two parts. The interferometric phase sensitivity depends on the specific quantum state created with the two condensates, and, therefore, on the time scale of the splitting process. We identify three different regimes, characterized by a phase sensitivity $\Delta \theta$ scaling with the total number of condensate particles $N$ as i) the standard quantum limit $\Delta \theta \sim 1/N^{1/2}$, ii) the sub shot-noise $\Delta \theta \sim 1/N^{3/4}$ and the iii) the Heisenberg limit $\Delta \theta \sim 1/N$. However, in a realistic dynamical BEC splitting, the 1/N limit requires a long adiabaticity time scale, which is hardly reachable experimentally. On the other hand, the sub shot-noise sensitivity $\Delta \theta \sim 1/N^{3/4}$ can be reached in a realistic experimental setting. We also show that the $1/N^{3/4}$ scaling is a rigorous upper bound in the limit $N \to \infty$, while keeping constant all different parameters of the bosonic Mach-Zehnder interferometer.

GPS를 이용한 저궤도 위성 자세 결정의 미지정수 결정 성공확률 향상

GPS 반송파 측정값을 이용하게 되면 수 cm 이하의 정밀도로 위치 결정을 수행 할 수 있으며, 두 개 이상의 안테나를 움직이는 물체에 장착할 경우 정밀한 자세 결정을 수행할 수 있다. GPS 반송파 측정값을 사용하는 경우 항상 미지정수 결정의 어려움이 발생하게 되며, 미지정수 결정 과정에서 올바른 결정을 할 수 있는 척도로 성공확률을 확인할 필요가 있다. 본 논문에서 저궤도 위성의 자세 결정을 위하여 이중차분된 측정값을 사용하게 되며, 이때 만들어진 측정행렬과 측정값의 공분산을 이용하여 성공확률을 계산하게 된다. 성공확률을 향상시키기 위하여 저궤도 위성의 위치벡터와 자세벡터가 수직이라는 제한 조건을 사용하여 측정값을 증가시키는 방법을 제안하였다. 적용된 저궤도 위성의 궤도는 우리별 3호의 궤도 정보를 이용하여 만들었으며 시뮬레이션을 통하여 그 결과를 확인 하였다. To determine precise position GPS carrier phase measurements are used. In addition, the multi-antenna system consisting of 2 or more GPS antennas can make attitude determination effectively. When GPS carrier phase measurements are used the integer ambiguity must be fixed. The success rate is used to validate the integer ambiguity. For LEO satellite attitude determination the double difference carrier phase measurements are used, the success rate is calculated using the covariance matrix and the measurement matrix. The constraint that LEO satellite position vector and attitude vector is orthogonal is suggested for improving the success rate. The LEO satellite orbit model is KITSAT3. The results of the simulation are shown and analyzed.

First Results with the IOTA3 Imaging Interferometer: The Spectroscopic Binaries Virginis and WR 140

We report the first spatially resolved observations of the spectroscopic binaries λ Vir and WR 140, including the debut of aperture-synthesis imaging with the upgraded three-telescope IOTA interferometer. Using IONIC-3, a new integrated optics beam combiner capable of a precise closure phase measurement, short observations were sufficient to extract the angular separation and orientation of each binary system and the component brightness ratio. Most notably, the underlying binary in the prototypical colliding-wind source WR 140 (WC7 + O4/O5) was found to have a separation of ~13 mas with a position angle of 152°, consistent with previous interpretations of the 2001 dust shell ejection only if the Wolf-Rayet star is fainter than the O star at 1.65 μm. We also highlight λ Vir, whose peculiar stellar properties of the Am star components will permit direct testing of current theories of tidal evolution when the full orbit is determined.

Evaluation of high‐precision phase‐shifting electron holography by using hologram simulation

AbstractIn phase‐shifting electron holography, Fresnel diffraction at an electron biprism introduces distortions to the amplitude and phase of the electron waves, which cause phase errors in the reconstructed phase images. To reduce the phase errors, two correction methods have been proposed, termed Fresnel corrections. In order to evaluate the phase‐shifting electron holography with Fresnel corrections, we faithfully simulated holograms by considering the influence of Fresnel diffraction, the quantum noise and the electron wave coherency, and then compared the phase images reconstructed from corrected and uncorrected holograms. We found that the phase error due to Fresnel diffraction was reduced to 1/20 by using Fresnel corrections, and that the phase measurement precision reached 2π/410 rad. We are able to observe the weak electric field due to positive charges corresponding to five electrons. Copyright © 2003 John Wiley & Sons, Ltd.

Utilização do Software GPSeq na Solução Rápida das Ambigüidades GPS no Posicionamento Relativo Cinemático de Bases Curtas

Centimeter level GPS positioning is based on the very precise carrier beat phase measurements. However, this observable is ambiguous by a number of whole cycles between the satellite and receiver antenna at the first epoch of data collecting, which is called the ambiguity. GPS ambiguities are introduced as parameters to be estimated in the observation equations. However, since they are integer numbers there is no standard techniques for solve them. One of the ways is to apply sequential conditional least-squares estimation together with integer search techniques. The ambiguity resolution can be divided in two steps: estimation and validation. The estimation is concerned with the computation of the ambiguities values. The validation step is used to infer if the estimated value can be accepted or not. From the last decade until nowadays ambiguity resolution has been one of the most important research topic in geodetic positioning and a several methods have been proposed. Special attention has been made about the fast ambiguity resolution. The aim of this paper is to investigate the ambiguity resolution in the context of relative kinematic positioning and its implementation in the GPSeq software, which is a GPS data processing software developed in academic environment. In this paper some experiments about kinematic processing are presented, whose results shown that the GPSeq solution is compatible on the centimeter level with Reliance software. The results also shown an inefficiency of the ratio and the difference between the quadratic form of the residuals of the second best and best solution tests in validating the ambiguity resolution in time limits of solution of the baselines processed.

Noise immune unwrapping based on phase statistics and self-calibration

Unwrapping is an important step for precise phase measurement in an interferometric technique. Due to the effects of noises and speckles, an accurate unwrapping has been quite difficult. To address this issue, a new phase unwrapping method is proposed. The new method uses the wrapped phase statistics together with the limited smoothness characteristics of the interference phase. In this method, statistical parameters of the wrapped phase are firstly obtained. The step is then followed by a self-calibration process to identify and correct corrupted data points to obtain preliminary unwrapped phases. Finally, a phase revision step is taken to remove the effects of the residual errors. A computational testing was carried out to demonstrate the performance of the proposed method at six different levels of noise injection. An experimental test was also carried out using a lateral shearing interferometer. The success and the precision achieved using the proposed algorithm show that the method is quite effective and accurate for phase recovery under the condition of noise contaminations.

Increase in accuracy of phase difference measurement in an acousto-optic processor due to cross-talk correction

The acousto-optic (AO) processor used for the simultaneous measurement of radio signal phase difference and frequency is a new and powerful AO device that can be used to detect and recognize radio sources. The main parameter decisive in its application is the precision of phase and frequency measurement. This paper describes the construction and principle of operation of this processor, a theoretical model of the cross-talk phenomenon, experimental results, and the accuracy of measurements with a correction function.