Sony Ericsson GM28, Integrator'S Manual

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GM28 INTEGRATOR’S MANUAL
44
LZT 123 7468 R1A
5.4.2 Antenna Type
Make sure that you choose the right type of antenna for the modem.
Consider the following requirements:
• the antenna must be designed for the dual frequency bands in use:
GSM850/1900;
• the impedance of the antenna and antenna cable must be 50
Ω
;
• the antenna output-power handling must be a minimum of 1W;
• the VSWR value should be less than 3:1 to avoid damage to the
modem.
5.4.3 Antenna Placement
The antenna should be placed away from electronic devices or other
antennas. The recommended minimum distance between adjacent
antennas, operating in a similar radio frequency band, is at least 50cm.
If signal strength is weak, it is useful to face a directional antenna at the
closest radio base station. This can increase the strength of the signal
received by the modem.
The modem’s peak output power can reach 1W. RF field strength varies
with antenna type and distance. At 10cm from the antenna the field
strength may be up to 70V/m and at 1m it will have reduced to 7V/m.
5.4.4 The Antenna Cable
Use 50
Ω
impedance low-loss cable and high-quality 50
Ω
impedance
connectors (frequency range up to 2GHz) to avoid RF losses. Ensure
that the antenna cable is as short as possible.
The Voltage Standing-Wave Ratio (VSWR) may depend on the
effectiveness of the antenna, cable and connectors. In addition, if you
use an adapter between the antenna cable and the antenna connector, it
is crucial that the antenna cable is a high-quality, low-loss cable.
Minimize the use of extension cables, connectors and adapters. Each
additional cable, connector or adapter causes a loss of signal power.
5.4.5 Possible Communication Disturbances
Possible communication disturbances include the following:
•
Noise can be caused by electronic devices and radio transmitters.
• Path-loss occurs as the strength of the received signal steadily
decreases in proportion to the distance from the transmitter.
• Shadowing is a form of environmental attenuation of radio signals
caused by hills, buildings, trees or even vehicles. This can be a