uhd

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UHD - Calibration Application Notes

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.. contents:: Table of Contents

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Self-calibration

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The 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 changes settings.

Calibration results are specific to an individual RF board.

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...

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Basic tool usage

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UHD installs the calibration utilities into <install-path>/bin.

Run the following from the command line:

::

    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.

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Calibration files

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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.

 * **Unix:** ${HOME}/.uhd/cal 

 * **Windows:** %APPDATA%\.uhd\cal