Page 21 - Antennas for Base Stations in Wireless Communications

xx Introduction

TABLE 1 Features of Antennas in Personal Mobile Terminals and Base Stations
Antennas in Mobile Antennas/Arrays
Terminals in Base Stations
Size Very small Compact
Operating bands Multiple bands (up to six) for Multiple bands (up to four)
cell phones and laptops for cell phones, WiFi, and
Bluetooth
Ultra-wideband Universal UHF bands for
RFID
Ultra-wideband
Diversity Available in laptop and Available if needed
UWB wireless USB dongles
Polarization Circularly polarized in Dual polarization for cell
RFID handheld readers phones, WiFi, and bluetooth
Circular polarization in
RFID readers and location
beacons
Adaptive beamforming Not available Available if needed
MIMO Will be available Available if needed

mobile terminal antennas where critical size and cost constraints are
imposed. For base stations, the requirements for high-performance
antennas or arrays have pushed antenna engineers to implement more
complicated RF, electrical, and/or mechanical designs to control antenna
and array performance, in particular for the radiation patterns of base
station antennas or arrays. Therefore, the antenna or array is designed
as a subsystem rather than only an RF component.
Furthermore, the antenna or array will be intelligent (smart or adap-
tive) if powerful signal processing functions are applied to controlling
antenna performance or digitally processing signals from antennas to
form a closed feedback loop. The concept of antenna design is, therefore,
expanded to cover not only RF radiators, controlling circuits, or subsys-
tems but also signal processing algorithms, as shown in Figure 2. Such
a concept has been used substantially in the development of antennas
for base stations in wireless communications, the details of which will
be found in this book.

In This Book

Antennas have become one of the most important technologies in
modern mobile wireless communications. Many excellent books discuss
the fundamental concepts or typical designs for general applications.
Most of them are textbooks for students, 2–5 whereas the practical issues
in antenna engineering are usually included in engineering handbooks