Huawei EM820W Hardware Manual page 29

HUAWEI EM820W HSPA+ PC Embedded Module
Hardware Guide
For the antennas on laptops, the recommended envelope correlation coefficient
between the master antenna and the diversity antenna is smaller than 0.5.
Radiation Pattern
The radiation pattern of an antenna reflects the radiation features of the antenna in
the remote field region. The radiation pattern of an antenna describes the power or
field strength of the radiated electromagnetic waves in various directions from the
antenna. The power or field strength varies with the angular coordinates (θ and φ),
but is independent of the radial coordinates.
The radiation pattern of half wave dipole antennas is the best option for wireless
terminals. The radiation pattern of half wave dipole antennas is omnidirectional in the
horizontal plane, and the incident waves of base stations are often in the horizontal
plane. For this reason, the reception is optimal.
To improve the performance of diversity antennas, it is recommended that the
radiation pattern of the slave antenna be complementary with that of the master
antenna.
The following radiation patterns are recommended for the antennas on laptops:
Gain and Directivity
The radiation pattern of an antenna represents the field strength of the radiated
electromagnetic waves in all directions, but not the power density that the antenna
radiates in the specific direction. The directivity of an antenna, however, measures
the power density that the antenna radiates.
Gain, as another important parameter of antennas, correlates closely to the directivity.
The gain of an antenna takes both the directivity and the efficiency of the antenna
into account. The appropriate antenna gain prolongs the service life of relevant
batteries.
The following antenna gain is recommended for antennas on laptops:
Issue 01 (2010-12-09)
Master antenna: omnidirectional
Slave antenna: complementary with the radiation pattern of the master slave
GPS antenna: omnidirectional
Wi-Fi antenna: omnidirectional
Gain of the master antenna ≤ 3 dBi
Gain of the slave antenna ≤ 3 dBi
The antenna on a laptop consists of the antenna body and the relevant RF transmission
cable. Take the RF transmission cable inside the laptop into account when measuring any
of the preceding antenna indicators.
Huawei cooperates with various antenna suppliers who are able to make suggestions on
antenna design, for example, Amphenol, Skycross, Pulse etc.
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RF Specifications
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