[USRP-users] Tune Request for B210

altuğ kaya altugkaya1996 at gmail.com
Mon Jul 3 09:06:51 EDT 2017


Dear Marcus,

Thank you for your answer.

There is a transmitter and I try to receive the transmitted signal with two
antennas of the B210. As the signal is transmitted from the same source, I
would expect same signals at the receiver side. Nevertheless, at the output
(after the DSP part of the FPGA) these two very same signals become
phase-shifted. Thus, I want to by-pass the DDC Chain in order to observe
weather phase-shift is caused by DSP modules or not.

If you have any suggestions, I would keen to hear them.

Best regards,
Altug

On Mon, Jul 3, 2017 at 2:52 PM, Marcus Müller via USRP-users <
usrp-users at lists.ettus.com> wrote:

> You can do this with uhd.tune_request_t in python, if you're writing GNU
> Radio Python code, but otherwise, yes, that should be part of your C++ UHD
> program; see the examples that ship with UHD [1] under host/examples.
>
> Anyway, as I tried to illustrate before, I don't think you're chasing the
> right problem, but I might still be misunderstanding you. Could you maybe
> explain why you think setting the DSP frequency to zero solves your
> problem, and what exactly that problem is, and why it is a problem? Thanks!
>
> Best regards,
>
> Marcus
>
> [1] https://github.com/EttusResearch/uhd
>
> On 07/03/2017 01:01 PM, altuğ kaya via USRP-users wrote:
>
> Hello everyone,
>
> I would like to tune the DDC Chain of my B210. When I search the net and
> ask to this forum, I learned that I have to equate the sampling rate to the
> master clock in order to by-pass the filters and I have to eliminate the
> CORDIC in order to add/subtract 0 Degrees from IQ data. Changing the
> sampling rate is rather easy, as it is done from cmd by entering an
> additional parameter. However, I did not understand how to manipulate
> CORDIC.
>
> In the MailArchive of USRP[1], I found the explanation below:
>
>> A tune request similar to this will disable the CORDIC:
>> uhd::tune_request_t tune_req(target_frequency_in_hz, desired_lo_offset);
>> tune_req.dsp_freq_policy = tune_request_t::POLICY_MANUAL;
>> tune_req.dsp_freq = 0.0;
>>
>> But, I really cannot figure out where to put these. Should I write a C++
> code and include tune_request.hpp?
>
> I am looking forward to your reply,
> Altug
>
> [1]https://www.mail-archive.com/usrp-users@lists.ettus.com/msg01105.html
>
>
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