[USRP-users] Phase compensate issue

Hojoon Yang omnibusor at kaist.ac.kr
Sun Nov 12 11:44:11 EST 2017


Hi guys!please let me know whether following operation is possible!we have USRP B200.All I want to do is to transmit a specific signal without distorting phase.Say, I want to transmit the cosine wave, which have center frequency fc = 3Mhz and phase is 60 degree(i.e. y = cos(2*pi*3e6*t + pi/3) ) through the Tx/Rx channel in USRP B200.But, I heard that there is a consistent phase offset after tuning. Thus, when we transmit the cosine signal as it is, it will have phase offset. I dont care the amplitude, but only care the exact phase.In order to compensate the phase offset, we are going to receive the signal which is transmitted from the Tx/Rx channel since we don't know the phase offset before it transmits. If we receive the signal, then we can know the phase offset 'theta'. since we know the phase offset theta, to compensate the phase offset, We multiply that signal by -theta.In summary,(a) USRP B210 transmit the signal through the Tx/Rx channel, which will have phase offset, say X.(b) the usrp receive the (a) signal to know the phase offset X through RX2 channel(i.e. A loopback using a single USRP.)(c) multiply the signal samples by -X  to compensate the phase and transmit!1. Will it be possible??2. Marcus said that The SBX has a special architecture based on a LO synthesizer that allows to have a deterministic phase after "tuning"What is the exact meaning of tuning? it means frequency lock?
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