Rf-Pll; Intermediate Frequencies; Table 28. Fsk Mode Intermediate Frequencies - ST STM32WL55JC Reference Manual

Sub-GHz radio (SUBGHZ)
The sub-GHz radio, depending on the transmit output power (max + 22 dBm), can heat up
the device. The heating depends on the used transmit output power and the device
package. Careful PCB design using thermal heat dissipation techniques must be applied to
avoid heat transfer to the HSE32 reference clock source. For the HSE32 frequency drift
requirements related to the sub-GHz radio, see
5.5 Sub-GHz radio modems
The following modems are provided enabling the respective modulation and associated
framing.
• LoRa with the LoRa framing
•
FSK and MSK with a generic framing
• BPSK with a BPSK framing
The modems and frame types are set by Set_PacketType()command. The current used
modem and frame type can be obtained by Get_PacketType()command.
Once the modem and frame to be used are selected, modulation and packet parameters
can be defined by Set_ModulationParams() and Set_PacketParams() commands.
The LoRa and (G)FSK
The (G)MSK and BPSK modems only supports transmission.
The framing determines how the bit stream is translated in packets and how data is stored in
the data buffers. It performs operations such as whitening and CRC handling. The framing is
configured using Set_PacketParams()command.
5.5.1 LoRa modem
The LoRa modem uses spread spectrum modulation and forward error correction
techniques to increase the range and reliability of sub-GHz radio communication. The LoRa
modem provides improved co-channel rejection.
The LoRa modulation can be optimized for a given application by
Set_ModulationParams()command, allowing a trade off between link budget,
interference immunity, spectral occupation and nominal data rate.
The following parameters can be optimized:
•
spreading factor (SF)
•
modulation bandwidth (BW)
• error coding rate (CR)
•
low data rate optimization (LDRO)
The LoRa symbol rate (Rs) is defined as Rs = BW / 2
The transmitted signal is a constant envelope signal. Equivalently, one chip is sent per
second per Hz of bandwidth.
a. The (G)FSK modem can be used for (G)MSK modulation when setting the frequency deviation to a quarter
of the bit rate.
160/1454
(a)
modems support both transmission and reception.
RM0453 Rev 2
Section 5.5.1: LoRa modem.
SF
RM0453