Ericsson M3090, Руководство интегратора

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16 M3090 Integrator’s Manual
Doc.no: 198 17 - KRD 102 303 Uen, Rev B
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An antenna cable is required to connect an antenna to the M3090 modem’s
antenna connector, that is, a detached antenna is used. A detached antenna
should consist of three parts: the antenna rod, an impedance matching network
and a coaxial cable with a connector. A detached antenna may be more effective
than other types, especially when the radio terminal is used in a vehicle.
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A half-wave dipole antenna should preferably be used. It should be low-weight
and as short as possible, while still complying with the antenna specifications.
Antenna specifications are found in
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.
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A cable with connectors at each end is required to connect a detached antenna
to the radio modem. Use a low-loss cable with high-quality connectors to avoid
loss of signal power between the antenna and the modem. Both the cable and
the connectors must have an impedance equal to that of the antenna connector
of the radio modem, that is, 50
. .The antenna cable should be flexible to
allow easy fitting of the antenna in a vertical position.
Poor contact between, or mismatching of, the connectors may cause a partial
reflection of the signal from the radio modem. The ratio between the modem’s
output power and the power reflected from the antenna is defined as the Voltage
to Standing Wave Ratio (VSWR) and is calculated using the formula shown in
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.
To get an effective communication, a VSWR of 2 or less is recommended for
the antenna, see
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.
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Ω
VSWR
1
ReflectedPower
OutputPower
------------------------------------------ +
1
ReflectedPower
OutputPower
------------------------------------------ –
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=