Calibrations; Table 2-2: Calibimage Command; Table 2-3: Ism Band Values - Semtech LR1121 User Manual

2.1.3 Calibrations

During the startup sequence, the device firmware calibrates the low and high frequency RC oscillators, the PLL, the ADC,
and the image rejection of the mixer at 915MHz. After the calibration procedure the device is set in Standby RC mode.
If operating at another frequency, the image calibration procedure must be restarted using command CalibImage(...).
An image calibration is advised after large temperature variations and optimal image rejection using command
CalibImage(...).
Image calibration is necessary if there is a frequency change > 10MHz, or a temperature change > 10°C.
2.1.3.1 CalibImage
The CalibImage(...) command launches an image calibration for the given range of frequencies Freq1 and Freq2 on the
RFI_N/P_LF sub-GHz path.

Table 2-2: CalibImage Command

Byte
Data from Host
Data to Host
By default, the image calibration is made in the band 902 - 928MHz. Nevertheless, it is possible to request the device to
perform a new image calibration at other frequencies. The frequencies are given in 4MHz steps (Ex: 900MHz -> 0xE1).
The calibration is valid for all frequencies between the two parameters. Typically, the user selects the parameters Freq1 and
Freq2 from Table 2-3: ISM Band
calibration for the Freq1 / Freq2 value.

Table 2-3: ISM Band Values

Frequency Band [MHz]
430-440
470-510
779-787
863-870
902-928
The command operates in any mode. At the end of the calibration procedure, the device returns to Standby RC.
For other frequency bands, Freq1 and Freq2 values can be obtained using the following formula:
• Freq1 = floor( (fmin_mhz - 1)/4)
• Freq2 = ceil( (fmax_mhz + 1)/4)
In the case of POR, or when the device is recovering from power-down or sleep mode without retention, the image
calibration is performed as part of the initial calibration process and for optimal image rejection in the band 902 - 928MHz.
If a TCXO is fitted, the calibration fails.
LR1121
User Manual Rev 1.1
UM.LR1121.W.APP Mar 2023
0
0x01
Stat1
Values. The same frequency may be provided as Freq1 and Freq2 to perform a single
Freq1
0x6B
0x75
0xC1
0xD7
0xE1 (default)
www.semtech.com
1
0x11 Freq1
Stat2 IrqStatus (31:24)
Freq2
0x6E
0x81
0xC5
0xDB
OxE9 (default)
2 3
Freq2
IrqStatus (23:16)
Proprietary & Confidential
15 of 130
Semtech