Page 46 - Antennas for Base Stations in Wireless Communications

Fundamentals of Antennas 19

Figure 1.9 shows the geometry of a narrow-strip monopole with a
horizontal bent portion, and the planer inverted-F antenna (PIFA) is
shown in Figure 1.10.
A PIFA can be considered a kind of linear inverted-F antenna (IFA),
with the wire radiator element replaced by a plate to expand band-
width.

Advantages:

■ Reduced height
■ Reduced backward radiation
■ Moderate to high gain in both vertical and horizontal polarizations

Disadvantages:

■ Narrow bandwidth
The shorting post near the feeding probe of the PIFA antennas is
a good method for reducing the antenna size, but this results in the
narrow impedance bandwidth.

w

h
w
h

(a) (b)
Figure 1.9 Geometry of a (a) narrow-strip monopole
with a horizontal bent portion (b) monopole

l 1 l 2
h w

Figure 1.10 Geometry of the PIFA