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========================================================================
UHD - Calibration Application Notes
========================================================================
.. contents:: Table of Contents
------------------------------------------------------------------------
Self-calibration
------------------------------------------------------------------------
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
* more to come...
********************************************
Calibration Utilities
********************************************
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.
********************************************
Calibration Data
********************************************
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\\
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