Page 42 - Antennas for Base Stations in Wireless Communications

Fundamentals of Antennas 15

1.2 Important Antennas in This Book
Here we introduce several antennas that are recently developed and
could be considered as relatively new. These antennas are conventional
microstrip antennas as narrow band planar printed antennas, sus-
pended planar antennas as wideband antennas, and planar monopole
as an ultra-wideband antenna (UWB).

1.2.1 Patch Antennas
The microstrip patch antenna is a popular printed resonant antenna for
narrow-band microwave wireless links that require semihemispherical
coverage. Due to its planar configuration and ease of integration with
microstrip technology, the microstrip patch antenna has been studied
heavily and is often used as an element for an array.
Common microstrip antenna shapes are square, rectangular, cir-
cular, ring, equilateral triangular, and elliptical, but any continuous
9
shape is possible. Figure 1.7 shows the parameters of circular and
rectangular patches. Some patch antennas eschew a dielectric sub-
strate and suspend a metal patch in air above a ground plane using
dielectric spacers; the resulting structure is less robust but provides
better bandwidth.

y y y

Microstrip L
Microstrip antenna
antenna R p
W x z
x
Feed point Feed point
Ground plane
Ground plane
Dielectric
substrate
Ground plane
(a) (b) (c)
*Ground plane covered by dielectric
Figure 1.7 (a) Circular patch, (b) rectangular patch, and (c) side view