3,367 research outputs found
Upgrading and testing program for narrow band high resolution planetary IR imaging spectrometer
An imaging spectrometer, intended primarily for observations of the outer planets, which utilizes an acoustically tuned optical filter (ATOF) and a charge coupled device (CCD) television camera was modified to improve spatial resolution and sensitivity. The upgraded instrument was a spatial resolving power of approximately 1 arc second, as defined by an f/7 beam at the CCD position and it has this resolution over the 50 arc second field of view. Less vignetting occurs and sensitivity is four times greater. The spectral resolution of 15 A over the wavelength interval 6500 A - 11,000 A is unchanged. Mechanical utility has been increased by the use of a honeycomb optical table, mechanically rigid yet adjustable optical component mounts, and a camera focus translation stage. The upgraded instrument was used to observe Venus and Saturn
Study on 3GPP Rural Macrocell Path Loss Models for Millimeter Wave Wireless Communications
Little research has been done to reliably model millimeter wave (mmWave) path
loss in rural macrocell settings, yet, models have been hastily adopted without
substantial empirical evidence. This paper studies past rural macrocell (RMa)
path loss models and exposes concerns with the current 3rd Generation
Partnership Project (3GPP) TR 38.900 (Release 14) RMa path loss models adopted
from the International Telecommunications Union - Radiocommunications (ITU-R)
Sector. This paper shows how the 3GPP RMa large-scale path loss models were
derived for frequencies below 6 GHz, yet they are being asserted for use up to
30 GHz, even though there has not been sufficient work or published data to
support their validity at frequencies above 6 GHz or in the mmWave bands. We
present the background of the 3GPP RMa path loss models and their use of odd
correction factors not suitable for rural scenarios, and show that the
multi-frequency close-in free space reference distance (CI) path loss model is
more accurate and reliable than current 3GPP and ITU-R RMa models. Using field
data and simulations, we introduce a new close-in free space reference distance
with height dependent path loss exponent model (CIH), that predicts rural
macrocell path loss using an effective path loss exponent that is a function of
base station antenna height. This work shows the CI and CIH models can be used
from 500 MHz to 100 GHz for rural mmWave coverage and interference analysis,
without any discontinuity at 6 GHz as exists in today's 3GPP and ITU-R RMa
models.Comment: To be published in 2017 IEEE International Conference on
Communications (ICC), Paris, France, May 201
A Novel Millimeter-Wave Channel Simulator and Applications for 5G Wireless Communications
This paper presents details and applications of a novel channel simulation
software named NYUSIM, which can be used to generate realistic temporal and
spatial channel responses to support realistic physical- and link-layer
simulations and design for fifth-generation (5G) cellular communications.
NYUSIM is built upon the statistical spatial channel model for broadband
millimeter-wave (mmWave) wireless communication systems developed by
researchers at New York University (NYU). The simulator is applicable for a
wide range of carrier frequencies (500 MHz to 100 GHz), radio frequency (RF)
bandwidths (0 to 800 MHz), antenna beamwidths (7 to 360 degrees for azimuth and
7 to 45 degrees for elevation), and operating scenarios (urban microcell, urban
macrocell, and rural macrocell), and also incorporates multiple-input
multiple-output (MIMO) antenna arrays at the transmitter and receiver. This
paper also provides examples to demonstrate how to use NYUSIM for analyzing
MIMO channel conditions and spectral efficiencies, which show that NYUSIM is an
alternative and more realistic channel model compared to the 3rd Generation
Partnership Project (3GPP) and other channel models for mmWave bands.Comment: 7 pages, 8 figures, in 2017 IEEE International Conference on
Communications (ICC), Paris, May 201
Aberration of the Cosmic Microwave Background
The motion of the solar system barycenter with respect to the cosmic
microwave background (CMB) induces a very large apparent dipole component into
the CMB brightness map at the 3 mK level. In this Letter we discuss another
kinematic effect of our motion through the CMB: the small shift in apparent
angular positions due to the aberration of light. The aberration angles are
only of order beta ~0.001, but this leads to a potentially measurable
compression (expansion) of the spatial scale in the hemisphere toward (away
from) our motion through the CMB. In turn, this will shift the peaks in the
acoustic power spectrum of the CMB by a factor of order 1 +/- beta. For current
CMB missions, and even those in the foreseeable future, this effect is small,
but should be taken into account. In principle, if the acoustic peak locations
were not limited by sampling noise (i.e., the cosmic variance), this effect
could be used to determine the cosmic contribution to the dipole term.Comment: 3 pages, 1 figure, comments welcome. Submitted to ApJ Letter
Materials and methods for large-area solar cells Final report, 17 Dec. 1964 - 16 Dec. 1965
Growth and evaluation of gallium arsenide-indium arsenide-aluminum foil structures in construction of thin film large area solar cells for satellite
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