NEO-D9S - Integration manual
• What is the external active antenna signal power?
• What is the bandwidth and filtering of the external active antenna?
• Does the L-band external antenna meet the recom4 dBic patch element gain for the
1525 MHz - 1559 MHz band?
Are destructive RF power levels expected to reach the RF input? Is interference from wireless
transmitters expected?
• What are the characteristics of these signals (duty cycle, frequency range, power range,
spectral purity)?
• What is the expected L-band performance under interference conditions?
Is there a risk of RF input exposure to excessive ESD stress?
• In the field: Can the user access the antenna connector?
• PCB / system assembly: Is there risk that statically charged parts (e.g. patch antennas) may be
discharged through the RF input?
The following subsections provide several options addressing the various questions above:
In some applications, such as cellular transceivers, interference signals may exceed the
maximum power rating of the RF_IN input. To avoid device destruction use of external input
protection is mandatory.
During assembly of end-user devices which contain passive patch antennas, an ESD
discharge may occur during production when pre-charged antennas are soldered to the L-
band receiver board. In such cases, use of external protection in front of RF_IN is mandatory
to avoid device destruction.
ESD discharge cannot be avoided during assembly and / or field use. Note that SAW filters are
susceptible to ESD damage. To provide additional robustness an ESD protection diode may be
placed at the antenna RF connector to GND.
4.8.3 Antenna/RF input
Check RF input requirements and schematic:
• With the NEO-D9S L-band module, an active antenna meeting our antenna requirements is
mandatory to achieve the performance values as written in the NEO-D9S datasheet and with a
minimum gain of 20 dB being reached at the module RF_IN pin.
• The total maximum noise figure including external LNA (or the LNA in the active antenna)
should be around 3 dB.
• Ensure active antenna gain is ideally between 30 - 40 dB gain.
• Make sure the antenna is not placed close to noisy parts of the circuitry and does not face any
other noisy elements (for example micro-controller, display).
• ESD protection on the RF input is mandatory.
• Bias-t inductor must be L-band frequency selected
• Ensure RF trace is tuned for 50 Ω to ensure L-band band width
4.8.4 Schematic design
For a
minimal design
with the NEO-D9S L-band modules, consider the following functions and pins:
• Connect the power supply to VCC.
• V_USB: If USB is used it is recommended V_USB is to be powered as per USB self-powered mode
specification.
• If USB is not used connect V_USB to ground.
• Ensure an optimal ground connection to all ground pins of the NEO-D9S L-band module.
UBX-19026111 - R07
4 Design
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