Xircom An Intel Company GEM3501 User Manual
Core Engine GSM/GPRS Modem Developer Guide Preliminary Draft: 7/6/2001
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Part Number: 07100026, Revision: 002
Confidential
© 2001 Xircom, Inc., an Intel company All rights reserved.
All trademarks and copyrights are the property of Xircom, Inc., an Intel company
All trademarks and copyrights are the property of Xircom, Inc., an Intel company
8.3.4 Antenna Polarization
Antenna polarization is normally defined as vertical, horizontal, slant left, slant right, or
circular. For portable devices, polarization purity is not required nor desired. Due to the
random positions that a portable device can be used in, and due to the fact that a
significant de-polarization of the predominantly linear polarization of the serving base
station will occur in most user environments, it is important that a portable device have an
antenna that will respond well to all polarizations. This is generally known as “dirty”
polarization and can be described as a polarization ellipse with an axial ratio (ratio of the
maximum to minimum response of the polarization ellipse) of 7 to 9 dB.
circular. For portable devices, polarization purity is not required nor desired. Due to the
random positions that a portable device can be used in, and due to the fact that a
significant de-polarization of the predominantly linear polarization of the serving base
station will occur in most user environments, it is important that a portable device have an
antenna that will respond well to all polarizations. This is generally known as “dirty”
polarization and can be described as a polarization ellipse with an axial ratio (ratio of the
maximum to minimum response of the polarization ellipse) of 7 to 9 dB.
8.4 Antenna Location and Network Communication
The antenna location for modem installation is dependent on the individual site conditions.
As a rule, the antenna should be positioned so that a reliable radio connection can be
made with the GSM network. The following guidelines will assist the installer in making
this determination.
As a rule, the antenna should be positioned so that a reliable radio connection can be
made with the GSM network. The following guidelines will assist the installer in making
this determination.
!
Where the reliability of the signal strength would be in question, one or more base
stations would enhance quality of the signal.
stations would enhance quality of the signal.
!
Where possible, the modem location should be selected so that the antenna has an
unobstructed line of sight to the selected base-station(s)
unobstructed line of sight to the selected base-station(s)
!
The antenna should be located to maximize the signal strength and quality received
from the selected base-station(s).
from the selected base-station(s).
!
It is recommended that the installer obtain GSM Network coverage maps from the
GSM operator indicating that the installation site is in a covered area. It is also
recommended that coverage and signal quality be verified prior to installation, using a
GSM handset.
GSM operator indicating that the installation site is in a covered area. It is also
recommended that coverage and signal quality be verified prior to installation, using a
GSM handset.
!
If possible, the modem and its associated antenna should be deployed inside an
environmentally controlled protected structure (such as an office building).
environmentally controlled protected structure (such as an office building).