Two sets of OFDM transmit data at the same time

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Hi,

    I discussed the problem of sending data simultaneously using usrpb210 in the chat room, but I still have some problems. I established a flow graph USRP_ Test0 (in the attachment) is used to test dual channel USRP transmission and reception. I observed the spectrum and time domain diagram of "out0" and "out1" of "USRP source", and found that the time domain diagram is basically the same, but the amplitude of "out1" is slightly higher than that of "out0", and so is the spectrum. Why? (the reason for the high amplitude of out1) I thought it was caused by carrier shift filtering due to different center frequencies, but it was also the case after I exchanged the center frequencies of RFA and RFB. Is it the cause of hardware failure?

     I know that the RFA of b210 and the TX of RFB share a lo, and so does RX2, but the center frequency I set is different. Why are "out0" and "out1" the same? Shouldn't some signals be filtered out through a low-pass filter? It just can't be completely filtered out, at least it can filter out a large part. I'm very confused.Is it because I failed to correctly configure the "USRP source sink" block?

     General signal sources can determine the frequency, such as cos (100k) and COS (200K). I can separate two signals through a filter (even if they are superimposed together), because I know their spacing, but in OFDM, such as USRP_ test As shown  , they have no definite frequency, and I don't know what its bandwidth is. Even if I multiply a "cos (W)" to distinguish two signals, I really don't know how much it should be multiplied to make their spectrum completely disjoint. Unless the bandwidth of the OFDM signal is equal to the bandwidth (SPS) of the USRP. because there is really no bandwidth for baseband OFDM.

     Any suggestions would be appreciated??

Best Regards,

Linge93

      

usrp_test0.pdf
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USRP_test.pdf
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