Page 48 - Antennas for Base Stations in Wireless Communications

Fundamentals of Antennas 21

Figure 1.11 Geometry of the planar
monopole antenna with a trident-shaped
(three-branch) feeding strip

Figure 1.12 A compact wideband
cross-plate monopole antenna
radiation patterns for frequencies across a wide operating bandwidth
of about 10 GHz (1.85–11.93 GHz).

1.3 Basic Measurement Techniques
Performing measurements of the antenna parameters to verify the
simulated design is very important. Measurements are also needed to
verify that the antenna achieves its requirements. The parameters of the
antenna that need to be measured are the input impedance, radiation
pattern, directivity, gain, and efficiency. Here, we will briefly state the
techniques used for these parameters. We are going to avoid some of the
laborious old techniques that were used for lack of modern equipment and
instead concentrate on the techniques that use modern equipment.

1.3.1 Measurement Systems
for Impedance Matching
Antenna impedance can be measured using a vector network analyzer.
+
A vector network analyzer is able to separate the forward wave, V , and
−
the reflected wave, V , from an antenna at a reference plane where cali-
bration is done, and thus the reflection coefficient is provided, which is