SL876Q5-A
Product User Guide
1VV0301333 Rev. 2
Page 40 of 68
2017-06-27
RF Interface
Built-in chip antenna
The SL876Q5-A module includes an internal chip antenna and LNA which is used when the
Internal / nExternal_Ant_Enable signal is high. See
Section 8.5.4 Internal / nExternal
. For important information regarding the required ground plane, see
Section
External RF Input
When the
Internal / nExternal_Ant_Enable
signal is low, the RF input (External Antenna
RF_In) pin accepts GNSS signals in the range of 1561 MHz to 1606 MHz at a level between
-125 dBm and -151 dBm into 50
Ω
impedance. See
Section 8.5.4 Internal / nExternal
The LNA_Enable output signal may be used to control power to the External Antenna LNA
(when it is selected).
A maximum of 16 V DC can be applied to the RF input.
The RF-IN pin is ESD sensitive.
An active antenna (that is, an antenna with a built in low noise amplifier) with a noise figure of
less than 1.0 dB should be used for optimum results. The SL876Q5-A contains an internal pre-
select SAW filter which is in both the External and Internal antenna input paths.
The chipset is in the Low Gain configuration by default This is the correct choice for the internal
chip antenna and an external active antenna. Using an external passive antenna (which is not
recommended) would require changing the gain to High via an OSP command.
Ground Plane
Due to the very small size of the built-in chip antenna, a proper ground plane is critical to
achieving good performance. Please refer to
Figure 12-1 SL876Q5-A Footprint and Ground
for ground plane requirements.
The recommended minimum size is 40 mm x 80 mm. Using a smaller size ground plane will
result in significant performance degradation. Please note that the guideline values in the table
below are only a very rough approximation since there are many variables that affect the
results.
Ground Plane Performance Reduction (approximate)
Size
Signal Strength (relative) dB
40 mm x 80 mm
-0
40 mm x 60 mm
-5
40 mm x 40 mm
-7
40 mm x 20 mm
-10
Table 8-7 Ground Plane Size
Содержание SL876Q5-A
Страница 1: ...SL876Q5 A Product User Guide 1VV0301333 Rev 2 2017 06 27...
Страница 68: ......