Use Of Phase Measurements Research Articles

High-Precision Vehicle Navigation in Urban Environments Using an MEM's IMU and Single-Frequency GPS Receiver

Many applications demand high-precision navigation in urban environments. Two frequency real-time kinematic (RTK) Global Positioning System (GPS) receivers are too expensive for low-cost or consumer-grade projects. As single-frequency GPS receivers are getting less expensive and more capable, more people are utilizing single-frequency RTK GPS techniques to achieve high accuracy in such applications. However, compared with dual-frequency receivers, it is much more difficult to resolve the integer ambiguity vector using single-frequency phase measurements and therefore more difficult to achieve reliable high-precision navigation. This paper presents a real-time sliding-window estimator that tightly integrates differential GPS and an inertial measurement unit to achieve reliable high-precision navigation performance in GPS-challenged urban environments using low-cost single-frequency GPS receivers. Moreover, this paper proposes a novel method to utilize the phase measurements, without resolving the integer ambiguity vector. Experimental results demonstrate real-time position estimation performance at the decimeter level. Furthermore, the novel use of phase measurements improves the robustness of the estimator to pseudorange multipath error.

Design of a full-dynamic-range balanced detection heterodyne gyroscope with common-path configuration

In this article, we propose an optical heterodyne common-path gyroscope which has common-path configuration and full-dynamic range. Different from traditional non-common-path optical heterodyne technique such as Mach-Zehnder or Michelson interferometers, we use a two-frequency laser light source (TFLS) which can generate two orthogonally polarized light with a beat frequency has a common-path configuration. By use of phase measurement, this optical heterodyne gyroscope not only has the capability to overcome the drawback of the traditional interferometric fiber optic gyro: lack for full-dynamic range, but also eliminate the total polarization rotation caused by SMFs. Moreover, we also demonstrate the potential of miniaturizing this gyroscope as a chip device. Theoretically, if we assume that the wavelength of the laser light is 1550nm, the SMFs are 250m in length, and the radius of the fiber ring is 3.5cm, the bias stability is 0.872 deg/hr.

Bat-inspired distance measurement using phase information.

This paper shows the use of phase measurement to estimate the distance to a target. Inspiration for this work comes from the observation that bats have been shown to have exceptional resolution with regard to target detection when searching during flight. Au and Simmons [“Echolocation in dolphins and bats,” Phys. Today 45(7), 40–45 (2007)] concluded bats with a center frequency of about 80 kHz (i.e., 4-mm wavelength), and 40-kHz bandwidth can have a resolution of distance in air approaching 20 μm. For this frequency, we see that the resolution achieved by the bat is about 200 times better than λ/2 (i.e., 2 mm at this frequency), which is usually used as a guide for resolution for analog systems. Moreover, Au and Simmons show, using time-frequency analysis, that there are essentially two frequencies present at any particular time within a single bat pulse. Considering this use of two frequencies we may infer a distance. A new bat-inspired algorithm is presented. This is based on phase measurement and, when applied to underwater acoustics, shows that a resolution of 1/50 of the wavelength can be achieved in practice.

A quantitative method for dual‐pass electrostatic force microscopy phase measurements

AbstractElectrostatic force microscopy (EFM) has become a powerful tool for investigating charges on surfaces. The use of phase measurement in EFM is a direct and fast way to detect electrostatic force gradients, but only qualitatively. With the dual‐pass scheme, the phase signal at lifted height is often assumed to exclude any influences from the topography, but it does not. We report the collection of both topography and phase data by EFM on charged, micron‐sized metal wires. In order to quantify the electrostatic force, a cone model and finite element analysis are provided to integrate the force gradient from the phase signal. Copyright © 2007 John Wiley & Sons, Ltd.

Use of phase measurement in ionospheric sounding by FMCW signal

Ionosphere sounding by FMCW signal with additional amplitude modulation is suggested. It is shown that measurement of the phase delay of the envelope allows one to define the virtual heights more precisely.

The theoretical basis for the determination of optical pathlengths in tissue: temporal and frequency analysis

A concise theoretical treatment is developed for the calculation of mean time, differential pathlength, phase shift, modulation depth and integrated intensity of measurements of light intensity as a function of time on the surface of tissue, resulting from either the input of picosecond light pulses, or radio frequency-modulated light. The treatment uses the Green's function of the diffusion approximation to the radiative transfer equation, and develops this and its Fourier transform in a variety of geometries. Detailed comparisons are made of several of these parameters in several geometries, and their relation to experimentally measured clinical data. The limitations of the use of phase measurements is discussed.

Use of time waveform characteristics and phase measurements for vibration signal analysis

Comparisons are made betwen amplitude versus frequency and amplitude versus time analyses for typical machinery generated vibrations such as unbalance, misalignment, oil whirl, and aerodynamic/hydraulic pulsations. The information provided in each case shows the extent to which the amplitude versus time supplements the amplitude versus frequency analysis. Transient and non-steady-state vibrations are shown to be particularly well suited to amplitude versus time analysis; providing considerably more information than amplitude versus frequency. In particular, examples include machine criticals, beat frequencies, and electrical unbalance. Various combinations of basic vibration waveforms are used to suggest standardized techniques which can aid in simplifying interpretation of actual vibration data. The use of phase measurements, as obtained from time wave forms and as a direct measurement, is described for balancing and detection of machine defects.

Use of phase measurements for arrival-time extraction of overlapping sinusoidal signals in shallow water

The use of phase measurement for sinusoidal signal arrival-time extraction of overlapping signals subjected to multipath conditions in shallow water is considered. The phase-measurement method is applied to signal data from a research cruise. The method does not give convincing results. For distances greater than 10 000 m the results are negative. The results obtained are strongly dependent on the sound velocity profile. The signal pulse length was a very important parameter in the results. The optimal pulse length was shown to be greater than 10 msec and less than 100 msec regardless of the hydrophone depth for the two depths investigated. Subject Classification: [43]30.20; [43]60.30.