Dear Hojoon, the B200 can't go that far down in frequency, so 3 MHz is impossible.
But let's say you want to do 300 MHz. You say "phase is 60°", but phase is always *relative* to something. So, your question only makes sense in conjuction with another wave or theoretical source of time. > But, I heard that there is a consistent phase offset after tuning. That isn't true for the B200. Here, the phase after tuning the LOs is random. > 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. What does "the same phase" even mean for two tones of different frequencies? This makes no sense to me! > 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. > You will need to tune your receiver too, since receive and send bandwidths are the same, so without more work (you could implement something like a staggered alternating TX and RX tuning, but that doesn't sound like a feasible solution to any problem I can think of), this is not a solution to a problem you could encounter. > > 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. Aloopback using a single USRP.) > If you add another USRP to the mix, you add, again, phase uncertainty! > > (c) multiply the signal samples by -X to compensate the phase and > transmit! > You mean exp(-jX), right? > 1. Will it be possible?? Yes, I think so, but as explained above, I'm not sure what "compensated phase" even is if you have two different frequencies. And, your receiver would need to be able to phase-coherently sample both your old and your new frequency – but since you had to tune TX, you would also have to tune RX, so, no, I don't think this approach works. > 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? > Oh, ok. Here, tuning is the act of changing the mixing frequency of a receiver or transmitter. Best regards, Marcus On 12.11.2017 17:44, Hojoon Yang via USRP-users wrote: > > 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. Aloopback 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? > > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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