THE CHINESE UNIVERSITY OF HONK KONG

[attachment=16786]
Introduction
In the mobile communication, in the past decade, the industry has grown
significantly. In the past, the mobile unit has only for voice communication, it
has changed and more band and applications are need in a mobile phone
which may lead the mobile phone has multiple antenna.
In the mean time, the most of the mobile phone has been in internal antenna
elements instead of external whip and helix antennas used previously.[1] Also,
the space is very limited for antennas inside the casing of a mobile unit,
antennas with as small size as possible are needed. One great challenge in
the antenna development is to obtain compact antenna elements with
sufficient bandwidth and high efficiency.


Thesis Outline
In this chapter, there is a brief introduction on mobile phone issue is stated on
discussed.
In chapter 2, there is a review on the mobile phone antenna, discussion on
different type antenna on mobile phone.


Small mobile phone antenna
In recent years, the mobile cells market has been growing rapidly all over the
world. One of the trends in mobile phone in the past few years has been to
reduce the size and weight of the mobile phone. This remarkable reduction in
the unit’s size has sparked a rapid evolution of the antennas used for mobile
phone.


Miniaturization
To decrease the size of an antenna, the resonant frequency remains the same
even though the antenna size is reduced. Some of the parameters that may
suffer are:
1 Reduced efficiency (or gain)
2 Shorter range
3 Smaller useful bandwidth
4 Increased sensitivity to external factors


Reviews of Mobile Phone Antennas
For the mobile communication systems in 1980s (the earliest mobile
communication), the typical mobile phone was nearly 600cc in volume and
approximately 850g in weight. The antenna used for the first phone was a half
wavelength monopole antenna.



Inverted-L Antenna (ILA)
The inverted-L antenna is an end-fed short monopole with a horizontal wire
element placed on top that acts as a capacitive load. Figure 2.4 shows the
structure of the inverted-L antenna.