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
8.3.2 Antenna Pattern and Gain
The antenna pattern shape should be consistent for all frequencies of operation. The
radiation pattern shape and maximum gain should be consistent with the radio link
performance objectives and the anticipated deployment configurations. This combination
of factors will determine if a directional or omni-directional antenna pattern shape is
desired. In general, for a portable device the antenna pattern shape should be omni-
directional with a peak gain that is less than 2dBi and an average total field gain (vertical
and horizontal polarization combined response) that is -4dBi or greater.
radiation pattern shape and maximum gain should be consistent with the radio link
performance objectives and the anticipated deployment configurations. This combination
of factors will determine if a directional or omni-directional antenna pattern shape is
desired. In general, for a portable device the antenna pattern shape should be omni-
directional with a peak gain that is less than 2dBi and an average total field gain (vertical
and horizontal polarization combined response) that is -4dBi or greater.
Directional antennas can be used for wall mount applications. These antennas should
have a directional radiation pattern with a peak gain broadside to the antenna. For most
applications, these antennas should have a 10 dB front-to-back ratio as a minimum. The
peak gain will be a function of the system performance requirements and regulatory
allowances.
have a directional radiation pattern with a peak gain broadside to the antenna. For most
applications, these antennas should have a 10 dB front-to-back ratio as a minimum. The
peak gain will be a function of the system performance requirements and regulatory
allowances.
FCC requirements limit the amount of antenna gain permissible. The combination of
antenna and cable loss (if any) must be selected to maximize path gain within the FCC
requirements (maximum of 3dBi for mobile and 7dBi for fixed applications).
antenna and cable loss (if any) must be selected to maximize path gain within the FCC
requirements (maximum of 3dBi for mobile and 7dBi for fixed applications).
8.3.3 Antenna Beam Width
For mobile applications, the installer should select an omni-directional antenna with good
elevation beam width. With an omni-directional antenna, you trade some gain (azimuth)
for an increased elevation beam width (elevation). Good omni-directional antennas with
2-3dBi gain, and a good elevation beam width are readily available.
elevation beam width. With an omni-directional antenna, you trade some gain (azimuth)
for an increased elevation beam width (elevation). Good omni-directional antennas with
2-3dBi gain, and a good elevation beam width are readily available.
Fixed applications could use any type of antenna because there is more flexibility in gain,
but unless the installation site is on the outer fringes, or in a deep fade area, (major
obstructions) gain is the most important thing. Again, you trade gain for beam width
(azimuth and elevation).
but unless the installation site is on the outer fringes, or in a deep fade area, (major
obstructions) gain is the most important thing. Again, you trade gain for beam width
(azimuth and elevation).
The Installer should keep in mind that networks and site environments change. For
example, new cell sites are added to expand existing coverage and/or capacity. With this
growth, new obstructions are added as well, which could change the signal quality for
fixed applications (e.g. a newly constructed building).
example, new cell sites are added to expand existing coverage and/or capacity. With this
growth, new obstructions are added as well, which could change the signal quality for
fixed applications (e.g. a newly constructed building).
Therefore, it is recommended that the installer not install highly directional antennas
attempting to pinpoint the link to a serving base station. Due to the FCC restrictions, the
installer should be able to find a good performing antenna, which provides decent gain,
and good beam width performance.
attempting to pinpoint the link to a serving base station. Due to the FCC restrictions, the
installer should be able to find a good performing antenna, which provides decent gain,
and good beam width performance.
In order to accomplish “seeing” as much of the network as possible, the installer is
advised to use as broad of a beam width as possible (and reasonable given any particular
installation).
advised to use as broad of a beam width as possible (and reasonable given any particular
installation).
Installation using these guideline, avoid potential problems such as:
!
New base station sites, installed closer to site but which cannot be "seen" by
the network.
the network.
!
Serving cell taken out of service temporarily, but the network lacks the ability
to jump to other cell sites
to jump to other cell sites
!
Newly constructed obstructions, resulting in a change to the RF
environmental characteristics.
environmental characteristics.