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Estimate Transmit Power of AD9361

Question asked by rjc03001 on Dec 22, 2015
Latest reply on Dec 23, 2015 by tlili

Hi, I would like to estimate the transmit power output of the AD9361 on AD-FMCOMMS3. I know this has been discussed on here before but I am not getting good results by using the Tx Monitor function in IIO Scope. 


What I did was connect the Tx and Rx together and configured the settings as attached (0dB Tx attenuation and Rx gain, 1MHz tone) and measured the receive power of about -8.08 dBFS in IIO Scope.  I calculated about 0.08 dB loss in my coaxial cable (3") and about 1.39 dB insertion loss at 2.45 GHz for the TCM1-63AX+ balun on the transmit and receive end (total 2.78 dB insertion loss).  Taking these into account, I estimate about -8.08 + 2.78 + .08 = -5.215 dBFS at the AD9361 Tx.  Based on 0 dBFS of 0.625V for the AD9361, I calculated about 3.766 dBm (0.345V) of transmit power.  If I neglect the receive balun and coax cable and just take into account the transmit balun, I get about -6.605 dBFS (~2.9 dBm) at the transmit SMA connector.  Is this a reasonable approach?  Max transmit power says 7.5 dBm on the data sheet.