
Sub-GHz radio (SUBGHZ)
RM0453
154/1454
RM0453 Rev 2
5
Sub-GHz radio (SUBGHZ)
5.1
Sub-GHz radio introduction
The sub-GHz radio is an ultra-low-power sub-GHz radio operating in the 150 - 960 MHz ISM
band. LoRa
®
, (G)FSK/(G)MSK modulation in transmit and receive, and (D)BPSK in transmit
only, allow an optimal trade-off between range, data rate and power consumption. This
sub-GHz radio is compliant with the LoRaWAN
®
specification v1.0 and radio regulations
including ETSI EN 300 220, EN 300 113, EN 301 166, FCC CFR 47 part 15, 24, 90, 101 and
the ARIB STD-T30, T-67, T-108.
Features related to the LoRa modulation are only available on STM32WL55xx devices, that
support LoRa.
The sub-GHz radio consists of:
•
an analog front end transceiver, capable of outp 15 dBm maximum power on its
RFO_LP pin and + 22 dBm maximum power on RFO_HP pin
•
a digital modem bank providing the following modulation schemes:
–
LoRa Rx/Tx with bandwidth (BW) from 7.8 - 500 kHz, spreading factor (SF)
5 - 12, bit rate (BR) from 0.013 to 17.4 Kbit/s (real bitrate)
–
FSK and GFSK Rx/Tx with BR from 0.6 to 300 Kbit/s
–
(G)MSK Tx with BR from 0.1 to 10 Kbit/s
–
BPSK and DBPSK Tx only with bitrate for 100 and 600 bit/s
•
a digital control comprising all data processing and sub-GHz radio configuration control
•
a high-speed clock generation
5.2
Sub-GHz radio main features
The main features of the sub-GHz radio are listed below:
•
Half-duplex 150 - 960 MHz ISM sub-GHz radio transceiver supporting:
–
LoRa modulation
–
(G)FSK modulation
–
(G)MSK modulation
–
(D)BPSK modulation
•
Programmable output power up to + 22 dBm
•
Low-IF architecture, mixing the RF receive signal with a signal tone located in the
negative frequency
f
lo
= -f
rf
+ f
if
where f
lo
is the local RF-PLL oscillator frequency, f
rf
is the wanted receive
signal and f
if
is the intermediate frequency
•
Automatic I/Q calibration to improve image rejection