Table of Contents
UHD comes with several self-calibration utilities for minimizing IQ imbalance and DC offset. These utilities perform calibration sweeps using transmit leakage into the receive path (special equipment is not required). The results from a calibration are written to a CSV file in the user's home directory. UHD will automatically apply corrections at runtime when the user re-tunes the daughterboard LO. Calibration results are specific to an individual RF board.
Note: When a calibration table is present, and the user wishes to override the calibration settings through the API: the user should re-apply the desired setting every time the LO is re-tuned.
UHD comes with the following calibration utilities:
- uhd_cal_rx_iq_balance: - mimimizes RX IQ imbalance vs. LO frequency
- uhd_cal_tx_dc_offset: - mimimizes TX DC offset vs. LO frequency
- uhd_cal_tx_iq_balance: - mimimizes TX IQ imbalance vs. LO frequency
The following RF frontends are supported by the self-calibration utilities:
- WBX transceiver board
- SBX transceiver board
- RFX transceiver board
UHD installs the calibration utilities into <install-path>/bin. Disconnect any extrernal hardware from the RF antenna ports, and run the following from the command line. Each utility will take several minutes to complete.
uhd_cal_rx_iq_balance --verbose --args=<optional device args> uhd_cal_tx_iq_balance --verbose --args=<optional device args> uhd_cal_tx_dc_offset --verbose --args=<optional device args>
See the output given by --help for more advanced options, such as: manually choosing the frequency range and step size for the sweeps.
Note: Your daughterboard needs a serial number to run a calibration utility. Some older daughterboards may not have a serial number. If this is the case, run the following command to burn a serial number into the daughterboard's EEPROM:
<install dir>/share/uhd/utils/usrp_burn_db_eeprom --ser=<desired serial> --args=<optional device args>
Calibration files are stored in the user's home/application directory. They can easily be moved from machine to another by copying the "cal" directory. Re-running a calibration utility will replace the existing calibration file. The old calibration file will be renamed so it may be recovered by the user.
- Linux: ${HOME}/.uhd/cal/
- Windows: %APPDATA%\.uhd\cal\