Hey, the attached flowgraph simply generates a sine which is transmitted and received by the same USRP in a loop (30dB attenuation + coax cable between tx and rx port). I used the following USRPs:
- B210 - X300 (1G Eth) - X310 (1G Eth) On the Rx side I just added a time sink to view the complex sine. Here is my observation: If no multiplication operations are used on Tx side, one can observe a "time constant" snippet (or segment) of the sine displayed by the time sink on Rx side - which is, imho, the expected behavior. As soon as one multiplication is part of the Tx side (just enable the "multiply const" block in the attached graph) one can observe that the sine wave is "wandering" or drifting on Rx side. I assume that the drifting effect is caused by lost or added samples on the Tx side. This behavior is only present for the X300 and X310 devices and not for the B210. Are my assumptions about the expected behavior correct? Is there any chance stop this drift with X3x0 devices? Background: The issue attractes attention because I'm working on a kind of channel estimation, where I noticed that my correlation sequence delivers some unexpected results as I changed from B210 to X300. Thanks! Kai
drift.grc
Description: application/gnuradio-grc
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