NINA-B2 series - System integration manual
UBX-18011096 - R05
System description
Page 9 of 35
C1- Public
The following SPI signals are available:
•
Chip select as input (
SPI_CS
)
•
Data lines (
SPI_MOSI
as input, and
SPI_MISO
as output)
•
Clock (
SPI_SCLK
as input)
•
Optional hardware flow control lines (
SPI_NORX
and
SPI_DRDY
as output)
For details on SPI operation, see the Communicating with a u-blox module over SPI bus, application
note [7].
1.8
Antenna interfaces
The antenna interface is different for each module variant in the NINA-B2 series.
Antenna pin – NINA-B221
NINA-B221 modules are equipped with an RF pin. The RF pin has a nominal characteristic impedance
of 50
Ω
and must be connected to the antenna through a 50
Ω
transmission line to allow reception of
radio frequency (RF) signals in the 2.4 GHz frequency band.
Choose an antenna with optimal radiating characteristics for the best electrical performance and
overall module functionality. An internal antenna, integrated on the application board or an external
antenna that is connected to the application board through a proper 50
Ω
connector can be used.
While using an external antenna, the PCB-to-RF-cable transition must be implemented using either a
suitable 50
Ω
connector, or an RF-signal solder pad (including GND) that is optimized for 50
Ω
characteristic impedance.
1.8.1.1
Antenna matching
The antenna return loss should be as good as possible across the entire band when the system is
operational to provide optimal performance. The enclosure, shields, other components, and
surrounding environment will impact the return loss seen at the antenna port. Matching components
are often required to retune the antenna to bring the return loss within an acceptable range.
It is difficult to predict the actual matching values for the antenna in the final form factor. Therefore,
it is a good practice to have a placeholder in the circuit that includes a ”pi” network, with two shunt
components and a series component in the middle. This provides maximum flexibility while the tuning
is matched to the antenna feed.
1.8.1.2
Approved antenna designs
NINA-B2 modules come with a pre-certified design that can be used to save costs and time during the
certification process. To take advantage of this service, you have to implement the antenna layout
according to the u-blox reference designs. The reference design is available on request from u-blox.
The designer integrating a u-blox reference design into an end-product is solely responsible for the
unintentional emission levels produced by the end product.
The module may be integrated with other antennas. In this case, the OEM installer must certify his
design with respective regulatory agencies.
Integrated antenna – NINA-B222
NINA-B222 modules are equipped with an integrated antenna on the module for simpler integration.
1.9
Reserved pins (RSVD)
RSVD pins should be left unconnected.
