Environmental Engineering Reference
In-Depth Information
Chapter 6
BMR Characterization of Antennas through the
Combined TD/FD Approach
'Science progresses best when observations force us to alter
our preconceptions.'
Vera Rubin
Abstract.
Antenna characterization measurements are traditionally performed in
the frequency domain (FD) through vector network analyzers (VNAs) in anechoic
chambers. Nevertheless, the expensiveness of these facilities limits the possibility of
using this approach for routine measurements. In this chapter, the strategies for the
accurate evaluation of the reflection scattering parameter (
S
11
(
) of antennas, start-
ing from simple time domain reflectometry (TDR) measurements, are described. As
a matter of fact, not only are instruments operating in time domain (TD) usually less
expensive than VNAs; but they allow performing time windowing, which is the key
for excluding the unwanted spurious reflection from the environment, thus avoiding
the use of anechoic chamber.
f
)
6.1
Introduction
Traditionally, measurements on antennas are carried out in the frequency domain
(FD) through vector network analyzers (VNAs) [6], in dedicated facilities (i.e.,
anechoic chamber). Although this procedure undoubtedly provides highly accurate
results, the high costs involved make such procedure virtually impracticable for rou-
tine measurements. For this reason, there is an abiding interest for assessing alterna-
tive methods (less expensive and yet accurate) for antenna characterization. Starting
from these considerations, this chapter focuses on the possibility of measuring the
reflection scattering parameter,
S
11
(
, of antennas through the TD/FD combined
approach, particularly useful for evaluating the impedance matching performance
and the resonance characteristics [17].
TDR has been largely used for the characterization of electronic devices, espe-
cially for characterization at low frequencies where VNA have some intrinsic limi-
tations [18]; yet the characterization of antenna through a TD-based approach is still
an open issue.
As a matter of fact, some of the advantages of the VNA (e.g., its high dynamic
range, frequency resolution and bandwidth) can be achieved with instruments op-
erating in TD, by appropriately tuning some measurement parameters, such as the
f
)
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