Huawei ME909u-521 Hardware Manual page 52

HUAWEI ME909u-521 LTE LGA Module
Hardware Guide
The following antenna efficiency (free space) is recommended for ME909u-521
module to ensure high radio performance of the module:
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In addition, the efficiency should be tested with the transmission line
S11 (VSWR) and S21
S11 indicates the degree to which the input impedance of an antenna matches the
reference impedance (50 Ω). S11 shows the resonance feature and impedance
bandwidth of an antenna. Voltage standing wave ratio (VSWR) is another expression
of S11. S11 relates to the antenna efficiency. S11 can be measured with a vector
analyzer.
The following S11 values are recommended for the antenna of ME909u-521 module:
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In addition, S11 is less important than the efficiency, and S11 has not strong
correlation to wireless performance.
S21 indicates the isolation between two antennas.
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:
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The primary antenna must be placed as near as possible to the ME909u-521 module
to minimize the line length. The secondary antenna needs to be installed
perpendicularly to the primary antenna. The secondary antenna can be placed farther
away from the ME909u-521 module. Antenna isolation can be measured with a
two-port vector network analyzer.
The following S21 values are recommended for the antenna:
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Issue 05 (2017-12-15)
Efficiency of the primary antenna: ≥ 40% (below 960 MHz); ≥ 50% (over 1420
MHz)
Efficiency of the secondary antenna: ≥ half of the efficiency of the primary
antenna in receiving band;
Efficiency of the GPS antenna: ≥ 50%
S11 of the primary antenna ≤ –6 dB
S11 of the secondary antenna ≤ –6 dB
S11 of the GPS antenna ≤ –10 dB
Distance between antennas
Antenna type
Antenna direction
Isolation between the primary and secondary antennas ≤ –12 dB
Isolation between the primary antenna and the GPS antenna ≤ –15 dB
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RF Specifications
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