Manual

ANSI C63.17-2006
Methods of Measurement of the Electromagnetic and Operational Compatibility of UPCS Devices
B.4
B.4.1
B.4.2
General guidelines on measurement conditions and procedures
Conducted measurements
When the transmit and monitoring system power can be measured at the EUT antenna terminals, these
characteristics are tested with conducted measurements, and the procedures described in Clause 7 can be
applied directly. Only the transmit antenna gain and the transmit and monitoring system equivalent
reception tests must be performed using radiated measurements.
The EUT transmit antenna gain is determined as recommended in IEEE Std 149-1979. For WB TEMs, the
test procedure is similar with the EUT being rotated within the cell. However, the measured quantity is not
field strength but rather radiated power.
Radiated measurements
Since the measurement parameters and variables can be expressed in several different, albeit equivalent,
ways, a number of test procedures can be used to evaluate the EUT with nondetachable antennas. As an
example, some of the methods presented in the standard test procedures are based on radiated propagation
(see Figure 2 and 4.8). Corresponding test procedures can also be based on facilities that measure radiated
power (wideband TEM, etc.), where instead of using the reference antenna, the necessary power levels are
generated and/or measured by the test facility itself.
The preferred test environment for radiated measurements is “free space.” For purposes of the tests
specified in this standard, the free-space environment can be realized in a wideband TEM, an anechoic
chamber, or simulated at an open-area test site (OATS) or semi-anechoic chamber by maintaining at least
10 dB loss of the signal reflected from the ground plane to the line-of-sight signal. A simulated free-space
environment can be achieved, for example, by lining the OATS or semi-anechoic chamber ground plane
with an RF absorber, by using the elevated test sites where both the EUT and the test antennas are placed at
a sufficient distance (height) over the ground plane and other reflective objects, and by utilizing directive
reference antennas, which reject the reflected wave to a sufficient degree.
In a simulated free-space environment, there are no specific requirements for the ground plane of the
facility. The free space and simulated free-space environment site validation documentation must be
provided, which demonstrates the required ratio of direct and reflected signal during the test.
To measure the EUT gain at facilities that make field strength measurements, install the EUT at a
nonconducting table or a turntable at the test site. Attach the EUT transmit antenna(s). Install a linearly
polarized calibrated reference at a distance r
t
> 2D
2
/λ from the EUT, where D is the largest dimension of
the EUT and λ is the wavelength of the signal. Align the reference antenna for its major lobe facing the
EUT. Configure the reference antenna as a receive antenna. Find the EUT direction of maximum radiation
by measuring the EUT emissions at sufficient number of equally spaced points on the surface of a sphere
with radius r and the EUT transmit antenna at its center. This can be achieved, for example, by measuring
the E-field intensity with horizontally and vertically polarized reference antenna, while moving the EUT
within 0° to 360° azimuth and 0° to 180° elevation plane angle variations. After the direction of the EUT
maximum radiation is found, the EUT gain G
A
can be determined using standard procedures for antennas.
For facilities that measure radiated power, such as WB TEMs, install the EUT in the center of the test
volume using nonconductive material to position the unit. Find the EUT direction of maximum radiation by
measuring the EUT emissions at sufficient number of equally spaced points on the surface of a sphere
surrounding the EUT. After the direction of the EUT maximum radiation is found, the EUT gain G
A
can be
determined using standard test procedures for antennas.
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