NAL A3LA-XM, Общее описание устройства

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NAL Research Corporation (TN2009-25-V1.0)
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2. Keep the antenna‘s VSWR low—the higher the antenna VSWR the higher the current consumed by
the A3LA-XM.
3. Keep the antenna cables‘ loss to less than 2dB—the higher the antenna cable loss the higher the
current consumed by the A3LA-XM.
4. Keep the power cable between the A3LA-XM and the power source as short as possible—the longer
the cable the higher voltage drop.
5.0 GPS FEED THROUGH (OPTIONAL)
As an option, a pass thru SMA connector can be added to the A3LA-XM to allow an external GPS receiver
to share the same A3LA-XM‘s Iridium antenna. The RF interface of the GPS pass through is summarized in
the table below.
The GPS pass through signal is isolated from the Iridium RF board by a directional coupler after the
A3LA-XM Rx low-noise amplifier (LNA). The loss of the directional coupler cancels out the gain of the LNA
resulting in the GPS signal gain/loss at the GPS connector of 0dB. The GPS pass through connector must be
terminated with a 50 load when not in use. A suitable load is the Huber+Suhner 65_SMA-50-0-1/111_NE.
Either a passive or an active GPS receiver can be connected to the pass through GPS connector. Users
must select a wideband Iridium antenna with appropriate sensitivity in both the Iridium frequency and the
GPS frequency. GPS signal is available and is passed through to the GPS receiver when the A3LA-XM is
powered but not transmitting. GPS signal will be de-graded during an Iridium call. During Iridium transmit
cycle there will be energy at the Iridium frequency which may adversely affect some GPS receivers.
6.0 SIM CARD INTERFACE
The A3LA-XM modem contains an integrated SIM reader. The modem uses and requires an Iridium SIM
chip for operation. The SIM chip is detached from the full-size Iridium SIM card. The SIM chip is inserted
into the opening located on top of the modem. A plastic locking mechanism (same as with GSM wireless
PARAMETER VALUE
Frequency Range 1575 MHz
Output Impedance 50
Insertion Loss 2 dB
Noise Figure
7 dB
Figure 6. GPS Pass Through Connector Added on the A3LA-XM Housing.