LENA-R8 series - System integration manual
UBX-22015376 - R02
Design-in
Page 64 of 116
C1-Public
bands (see
for possible suitable examples). Note that the addition of an external filter along
the cellular RF line has to be carefully evaluated, as the additional insertion loss of such filter may
affect the cellular TRP and/or TIS RF figures.
lists examples of GNSS band-stop SAW filters that may be considered for the cellular RF
input/output in case enough isolation between the cellular and the GNSS RF systems cannot be
provided by proper selection and placement of the antennas beside other proper RF design solutions.
Manufacturer
Part number
Description
Qualcomm
B8636
GPS / SBAS / QZSS / GLONASS / Galileo / BeiDou RF band-stop SAW
filter with low attenuation in Cellular frequency ranges
Qualcomm
B8666
GPS / SBAS / QZSS / GLONASS / Galileo / BeiDou RF band-stop SAW
filter with low attenuation in Cellular frequency ranges
Table 30: Examples of GNSS band-stop SAW filters
Additional considerations
As far as the RF Tx power is involved in the cellular / GNSS RF coexistence, it has to be noted that
high-power transmission occurs very infrequently: typical values are in the range of -3 to 0 dBm (see
the Tx Power distribution in the GSMA TS.09
Therefore, depending on the application, careful
PCB layout, antenna selection and placement should be sufficient to ensure accurate GNSS reception.
For an example of vehicle tracking application in a small form factor featuring cellular and short-range
connectivity alongside a multi-constellation GNSS receiver, with successful RF coexistence between
the systems, refer to the u-blox B36 vehicle tracking blueprint
. The distance between the cellular
and GNSS antennas for the u-blox B36 blueprint is annotated in
GNSS
antenna
5.5 cm
Cellular
antenna
SARA
module
Figure 42: PCB top rendering for the u-blox B36 blueprint with annotated distance between cellular and GNSS antennas
2.4.5
Cellular antenna detection interface (ANT_DET)
2.4.5.1
Guidelines for ANT_DET circuit design
describe the recommended schematic / components for the antennas detection
circuit that must be implemented on the application board and for the diagnostic circuit that must be
included
on the antennas’ assembly to achieve
cellular antennas detection functionality.
