HUAWEI EM820W HSPA+ PC Embedded Module
Hardware Guide
RF Specifications
Issue 01 (2010-12-09)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
20
z
Efficiency of the slave antenna > 40% (–4 dB)
z
Efficiency of the GPS antenna > 50% (–3 dB)
z
Efficiency of the Wi-Fi antenna > 40% (–4 dB)
Isolation
For a wireless device with multiple antennas, the power of different antennas is
coupled with each other. Antenna isolation is used to measure the power coupling.
The power radiated by an antenna might be received by an adjacent antenna, which
decreases the antenna radiation efficiency and affects the running of other devices.
To avoid this problem, evaluate the antenna isolation as sufficiently as possible at the
early stage of antenna design.
Antenna isolation depends on the following factors:
z
Distance between antennas
z
Antenna type
z
Antenna direction
The master antenna must be placed as near as possible to the EM820W to minimize
the cable length.
The slave antenna
needs to be installed perpendicularly to the
master antenna. The slave antenna can be placed farther away from the EM820W.
Antenna isolation can be measured with a two-port vector network analyzer.
The following antenna isolation is recommended for the antennas on laptops:
z
Isolation between master and slave antennas < –12 dB
z
Isolation between the master antenna and the GPS antenna < –15 dB
z
Isolation between the slave antenna and the Wi-Fi antenna < –15 dB
If a Wi-Fi module is installed on the laptop, the following measures must be taken to
reduce mutual influence between the data card module and the Wi-Fi module:
z
Adding a bandpass filter to the Wi-Fi channel to filter the WCDMA, GSM850,
GSM900, DCS, and PCS signals
z
Ensuring sufficient isolation between the master antenna of the data card
module and the Wi-Fi antenna
Table 4-4 lists the requirements for the isolation between the master antenna and the
Wi-Fi antenna in different frequency bands according to the interference suppression
supported by the filter in different frequency bands.
Table 4-4
Isolation between the master antenna and the Wi-Fi antenna
Frequency
Band
Transmit
Frequency
Conducted
Transmit
Power (dBm)
Ant
Isolator
(dB)
Wi-Fi Front End
Filter Attenuation
(dB)
UMTS2100 1920–1980
MHz
24
11
34
UMTS1900 1850–1910
MHz
24
11
34
UMTS850 824–849
MHz 24
10
36
UMTS900 880–915
MHz 24
10
36