Angular Transfer Function Research Articles

Experimental Correction of Radiation Patterns Between Electromagnetic Environments

This paper presents an experimental method to estimate a radiation pattern obtained in a particular echoic environment (for example, from in situ measurements) as if measurements were performed in a given anechoic chamber. The correction is achieved using some reference measurements collected both in echoic and anechoic environments. An angular transfer function is estimated from these two sets of measurements and deconvolved from the measured radiation pattern to be corrected.

THE BOLOCAM GALACTIC PLANE SURVEY. IX. DATA RELEASE 2 AND OUTER GALAXY EXTENSION

We present a re-reduction and expansion of the Bolocam Galactic Plane Survey, first presented by Aguirre et al. (2011) and Rosolowsky et al. (2010). The BGPS is a 1.1 mm survey of dust emission in the Northern galactic plane, covering longitudes -10 < \ell < 90 and latitudes |b| < 0.5 with a typical 1-\sigma RMS sensitivity of 30-100 mJy in a 33" beam. Version 2 of the survey includes an additional 20 square degrees of coverage in the 3rd and 4th quadrants and 2 square degrees in the 1st quadrant. The new data release has improved angular recovery, with complete recovery out to 80" and partial recovery to 300", and reduced negative bowls around bright sources resulting from the atmospheric subtraction process. We resolve the factor of 1.5 flux calibration offset between the v1.0 data release and other data sets and determine that there is no offset between v2.0 and other data sets. The v2.0 pointing accuracy is tested against other surveys and demonstrated to be accurate and an improvement over v1.0. We present simulations and tests of the pipeline and its properties, including measurements of the pipeline's angular transfer function. The Bolocat cataloging tool was used to extract a new catalog, which includes 8594 sources, with 591 in the expanded regions. We have demonstrated that the Bolocat 40" and 80" apertures are accurate even in the presence of strong extended background emission. The number of sources is lower than in v1.0, but the amount of flux and area included in identified sources is larger.

Analytical derivation of the stationarity and the ergodicity of a field scattered by a slightly rough random surface

In the framework of the small perturbation method, we present a new theoretical derivation of the statistical and spatial properties of a field scattered by a one-dimensional slightly rough random surface. The work concerns the intermediate field zone where the scattered field is reduced to the contribution of the progressive plane waves. The surface is assumed to be stationary, ergodic and Gaussian. First, from a statistical point of view, we demonstrate that under oblique incidence the scattered field is not stationary while it is strictly stationary under normal incidence. For an infinite surface, the scattered field modulus obeys to Hoyt law and the phase is not uniform. Second, from a spatial point of view, for a given altitude and under all incidences, we show that the scattered field is ergodic. Under oblique incidence, the phase is spatially uniform and the modulus is given by a Rayleigh law. Under normal incidence, the phase is not uniform and the modulus is given by a Hoyt law. Third, from a practical point of view, we show that the field measured by a directional antenna is ergodic and stationary if the angular transfer function of the antenna does not contain the specular direction.

Effect of the x-ray beam collimation on the resolution of an energy dispersive diffractometer

Although the energy dispersive x-ray diffraction (EDXD) technique has proved to have several merits in comparison with its conventional angular dispersive counterpart, it has the serious drawback that its resolution is intrinsically lower than that of the latter. This makes EDXD unsuitable each time that high-resolution measurements are needed. However, a wide class of samples does not require high resolution since the diffraction peaks they produce are so wide that the further broadening due to the use of EDXD is negligible. Amorphous solids, liquids, semicrystalline materials, and nanocrystalline powders belong to such a category. In this case, it is not worth performing sophisticated simulations to calculate the angular transfer function of the diffractometer because a simplified model is sufficient to describe the effect of the angular divergence of the x-ray beam on peak broadening. The aim of the present work is to obtain an analytic function that can be used for this purpose, allowing the collimation system to be properly set up.

Theory of Errors of a Multigimbal, Elastically Supported, Tuned Gyroscope

An elastically supported, tuned gyroscope is a complex device, but experience has shown that it can be represented by mathematical models by means of which practically all of its characteristic errors can be analyzed and predicted with good accuracy. The gyro angular transfer function, derived in [1], serves as an excellent basis of evaluation of errors due to asymmetries of the gimballing system and effects of rotor angular offsets. The gyro translational transfer function, derived in this paper, may be used in the analysis of errors caused by linear acceleration inputs.

Fiber Optics for Spectroscopic Illumination

Absolute and angular transmission measurements were made on a single sheathed fiber 0.15 mm in diameter and 2.1 m long, and an optical angular transfer function was defined and calculated. The effective transmission of the source brightness was calculated as a function of the f numbers of the entrance and output optics of the fiber, and these results were used to choose a suitable optical system for illumination of a spectrometer.