NIST Construction Automation Program Report No. 3: Electromagnetic Signal Attenuation in Construction Materials.
NIST Construction Automation Program Report No. 3:
Electromagnetic Signal Attenuation in Construction
Materials.
(4437 K)
Stone, W. C.
NISTIR 6055; 199 p. October 1997.
Available from:
National Technical Information Service
Order number: PB98-126873
Keywords:
construction automation; electromagnetic wave
propagation; metrology; non-line-of-sight metrology;
signal attenuation; spread spectrum radar; surveying;
wireless communicaitons
Abstract:
Laboratory studies of electromagnetic (EM) signal
propagation through construction materials were carried
out as part of the NIST initiative in Non-Line-of-Sight
surveying technology. From these data it is possible to
determine several important material-specific
characteristics needed for the design of engineering
systems which make use of EM signal propagation through
matter: 1) the power attenuation as a function of the
material thickness and 2) the values of the electrical
permittivity and dielectric constants for a particular
material as a function of frequency. The latter can be
used to calculate the propagation delay time associated
with an EM pulse penetrating through a specified
thickness of a given material. This information is
essential for error compensation for time-of-flight
metrology instrumentation systems. In this report, only
the power attenuation aspects are discussed; dielectric
and permittivity constants will be discussed in a future
volume. The materials investigated included brick,
masonry block, eight different concrete mixes, glass,
plywood, lumber (spruce-pine-fir), drywall, reinforced
concrete, steel reinforcing bar grids, variations of the
plywood and lumber tests in which the specimens were
soaked with water, and composite specimens involving
brick-faced masonry block and brick-faced concrete. For
each material, varying thickness specimens were
fabricated in order to measure attenuation as a function
of penetration distance. Each specimen was placed in a
special test range consisting of spread spectrum
transmission and reception horns spaced 2 meters apart
with a metal RF isolation barrier located midway between
the antennas to eliminate multiphath signals. The
isolation barrier contained a window at its center
against which the specimens were fit. Measurements of
power loss were taken at 2 MHz intervals from 0.5 to 2
GHz and from 3 to 8 GHz. Frequency power spectra were
discretely generated for each material as a function of
thickness and fit with closed-form predictor equations.
Coefficients for the predictor equations are provided.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899