[USRP-users] IQ balance calibration problem

Christophe ALEXANDRE christophe.alexandre at cnam.fr
Mon Feb 20 11:30:09 EST 2012


Hi list,

i'm trying to use the calibration utilities with

N210, WBX, UHD 3.4.0, Ubuntu 11.04

i have troubles using :

    uhd_cal_rx_iq_balance
    uhd_cal_tx_iq_balance
    uhd_cal_tx_dc_offset

1) if i use it with default options, i often get some errors
    while running : 

    Error : RunTimeError : no control response

    or

    OError : Unexpected error code 0x8

    or

    OError: did not get all the samples requested

    then the program stops.

    i have made some tests with 3 different PCs and 3
    differents N210.

    the only way to create successfully a calibration file
    is to reduce the number of samples from 10000 (default value)
    to 2000 or less.

2) my second problem is the efficiency of this calibration.
    i've created a QPSK test signal in order to visualize the correction
    with a scatterplot. The result of my tests is that the costellation is from far better
    without calibration than with it.



 regards.


 Christophe ALEXANDRE     
 Conservatoire National des Arts et Métiers (CNAM)        
 Laboratoire CEDRIC-LAETITIA 
 Département EASY
 Accès 17-1-32, Case 2D2P10  
 292 rue Saint Martin 
 75141 PARIS CEDEX 03 
 FRANCE     
 email : christophe.alexandre at cnam.fr               
 tel. 0140272699 
 mob. 0651087311
 fax. 0140272994    
 
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