Telit Wireless Solutions GT864-3G, Руководство пользователя

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GT864-3G Terminal Product Description
80269ST10071a Rev.0 - 14/09/0 9
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved
page 19 of 41
from the antenna the field strength may be up to 70V/m and at 1m it will have reduced to 7V/m. In
general, CE-marked products for residential and commercial areas, and light industry can
withstand a minimum of 3V/m.
2.9.3.1 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.
2.9.3.2 Antenna Connector
The
Telit GT864-3G Terminal
antenna connector allows transmission of radio frequency (RF)
signals between the modem and an external customer-supplied antenna. The modem is fitted with
a 50
Ω FME male coaxial jack.
Description of antenna connector parameters:
Parameter Limit Description
Nominal impedance 50 Ω
Output Power
2 Watt peak (Class 4)
1 Watt peak (Class 1)
0.25 Watt Peak (Class 3)
GSM900/850 MHz
GSM1800/1900 MHz
UMTS/HSDPA 2100MHz
2.9.3.3 Antenna precautions
If the antenna is to be mounted outside, consider the risk of lightning. Follow the instructions
provided by the antenna manufacturer.
•
Never connect more than one modem to a single antenna. The modem can be damaged
by radio frequency energy from the transmitter of another modem.
• Like any mobile station, the antenna of the modem emits radio frequency energy. To
avoid EMI (electromagnetic interference), you must determine whether the application itself,
or equipment in the application’s proximity, needs further protection against radio emission
and the disturbances it might cause. Protection is secured either by shielding the surrounding
electronics or by moving the antenna away from the electronics and the external signals
cable.
• The modem and antenna may be damaged if either come into contact with ground
potentials other than the one in your application. Beware, ground potential are not always
what they appear to be.