NEO-D9C - Integration manual
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
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-D9C module, an active antenna meeting our antenna requirements is
mandatory to achieve the performance values as written in the NEO-D9C datasheet and with a
minimum gain of 20 dB being reached at the module RF_IN pin.
• Implementing your own antenna design with a suitable antenna element (stacked patch or
helix) and the required RF components is complex and should not be carried out unless under
the strict guidance of the antenna supplier to meet our requirements. The risk in not meeting
the required RTK performance is a factor.
• An OEM active antenna module that meets our requirements should be used if there is a need
to integrate the antenna.
• The noise figure should be around 2 dB for the antenna assembly itself.
• Ensure active antenna gain is ideally between 30 - 40 dB gain and that an LNA gain of 20 dB
reaches the module RF_IN pin.
• 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).
• If a combined L1/L2/L6 antenna is used, for RTK operation good signals levels above 40 C/
N0 average are required. There is a requirement on the minimum number and type of GNSS/
QZSS satellites being received in a typical environment to achieve fixed RTK performance:
Signals above 35 C/N0 (minimum) for a minimum of 6 GPS satellites. The same is true for any
single system that is enabled (BeiDou, GLONASS). The same is true if a multi constellation
configuration is used. A single system being received must have 6 satellites at the minimum
signal level and quality to achieve RTK fixed status. L2/L6 signals for the NEO-D9C must have
similar C/N0 levels.
• If a patch type antenna is used, an antenna ground plane with minimum 100 - 150 mm
diameter is required.
• Ensure the combined antenna is L1 and L2/L6 band specified.
• Ensure the combined antenna element gain is between 2 - 3 dBic typical for L1 and L2/L6
bands.
• If a combined L1 + L2/L6 antenna is used, ensure the group delay variation including active
antenna is 10 ns max at each GNSS system bandwidth. Note: Inter-signal requirement 50 ns
max.
• ESD protection on the RF input is mandatory.
• Bias-t inductor must be L1 and L2/L6 band frequency selected.
UBX-21031631 - R02
4 Design
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