Sub-GHz radio (SUBGHZ) RM0453
154/1461 RM0453 Rev 1
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 outputting + 14 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
– MSK and GMSK RX/TX with BR from 1.2 to 300 Kbit/s and TX only with BR from
0.1 to 1.2 Kbit/s
– BPSK and DBPSK TX only with bit rate 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
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