OGi Modem - Hardware Guide
© ORBCOMM Proprietary 31 T401, Version .15
affect the highly sensitive satellite or GPS receiver performance if the antenna is placed
too close to the circuitry.
The following guidelines are provided when building a microcontroller using the modem.
Microcontroller and circuitry should be fully shielded.
Digital interfaces such as serial ports, USBs and I
2
C along with their tracks
should be shielded.
Avoid running any digital interface connector and cable close to the antenna. Do
not route any metal or cable above the ground plane of the antenna card or above
the antenna.
4.3.4 Decoupling
The following are recommendations for the power supply and digital lines to reduce
emissions that could be picked up by the modem.
RF decoupling/bypass capacitors (22pF 0403 or 33pF 0603 typical) be added as
close as possible to the modem's power pin on the power supply rail of the
processor and high speed digital circuitry.
RF decoupling/bypass capacitors added on the interface power rails.
4.4 Maximum Current
It is recommended that the power supply be designed with a margin to supply the
maximum current required by the modem. Refer to sections 3.4.1 and 3.4.2 for maximum
current and inrush current requirements when designing a power supply.
4.5 Enclosure Design
The modem is not designed for outdoor environments. Consequently, the enclosure
typically requires a robust environmentally sealed enclosure that can house the modem.
The following guidelines are recommended for the enclosure design.
An IP67 rating
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or better for outdoor use.
Use enclosure materials that are transparent to L-Band (1-2 GHz) radio signals.
Lexan Resin EXL 9330 is a common recommended enclosure material, but there are
many other suitable materials.
The unpackaged standard antenna is supplied with a dielectric cap, a piece of plastic
over the ceramic patch antenna that helps to negate the effects of different enclosure
materials on the performance of the antenna. With the dielectric cap, the standard
unpackaged antenna can be placed as close as desired to the adjacent enclosure
material.
The unpackaged low elevation antenna is less sensitive to enclosure material
selection and does not require a dielectric cap.
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IEC 60529
