Hello Ismael, With the B200 it is not possible to get the same phase offset at all frequencies, in fact that is not possible to obtain with any USRP. Some, such as the UBX and TwinRX, provide the ability to have the same phase offset every time you tune to a specific frequency. That allows the USRP to be calibrated once so you can remove the phase offset. With the B200 it is necessary to do a calibration every time it is tuned as there is no synchronization of the LO output phase with regards to the reference frequency. The B200 does not support the use of an external local oscillator for driving the mixers. You may be able to do the calibration without additional hardware by using the TX to RX leakage and timed commands to receive a test tone, but it will require appreciable work to calibrate out the various sources of time offsets and phase shifts.
This application note discusses the different USRPs and different levels of synchronization. https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices Regards, Derek On Tue, May 22, 2018 at 9:58 AM, Ismael Peruga via USRP-users < usrp-users@lists.ettus.com> wrote: > Hello everyone, > > I am developing a radar application with the USRP B200. For that purpose, > it is necessary that the phase difference between the TX and the RX local > oscillator remains constant in different frequencies (that is, I send a > pulse in a frequency, and after that, I change the frequency and send > another pulse, and so on...). The problem is that this phase difference is > not constant (even if I send the same frequency after I launch the program > two times). > > I've tried to find information, and it seems that it is a hardware > limitation. However I still think that this should be possible (maybe is it > possible to use an external oscillator for both TX and RX?) > > Thanks in advance, > > Best regards, > > Ismael. > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > >
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