On 06/05/2019 07:34 PM, Dario Fertonani via USRP-users wrote:
Sorry, I wrote "coherent" meaning that the problems show up only with
signal analyses that go beyond power spectrum.
For example, the output LTE signal gives CQI=15 (max quality) with
dsp_freq=0 and variable CQI (never 15) with dsp_freq = 11.52e6 (in all
cases sampling rate is set to 23.04e6 and master clock rate is twice
the sampling rate). I do know that LTE is robust to DC offset but this
is a more general question on UHD/B210.
You're using only a single channel on the B210? Because for
dual-channel the master_clock_rate is limited to 32MHz--that's a
limitation of the
way the data clocking works out of the AD9361 RF chip.
On Wed, Jun 5, 2019 at 4:23 PM Marcus D. Leech
<patchvonbr...@gmail.com <mailto:patchvonbr...@gmail.com>> wrote:
On 06/05/2019 07:12 PM, Dario Fertonani wrote:
Thank you Marcus. I should have mentioned that I tried removing
that line, with no success. With non-zero dsp_freq, the power
spectrum looks OK but the (coherent) signal quality is terrible.
OK, that's a different level of problem.
You're trying to maintain coherence across more than one B210?
On Wed, Jun 5, 2019 at 2:25 PM Marcus D. Leech via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>
wrote:
On 06/05/2019 05:20 PM, Dario Fertonani via USRP-users wrote:
I'm trying to move the "DC offset" out of the main spectrum
by using the dsp_freq field in uhd::tune_request_t. This
doesn't seem to work on B210, meaning that the following
code functions properly with DcOffset_Hz=0 but not, for
example, with DcOffset_Hz=10e6. In all these tests the
master clock rate is large enough to fit DcOffset_Hz and the
spectrum of interest easily. Anything obviously wrong?
Thanks,
Dario
uhd::tune_request_t uhdTuneRequest( const double
&CarrierFreq_Hz , const double &DcOffset_Hz )
{
uhd::tune_request_t tuneRequest( CarrierFreq_Hz -
DcOffset_Hz );
tuneRequest.args = uhd::device_addr_t( "mode_n=integer" );
tuneRequest.dsp_freq_policy =
uhd::tune_request_t::POLICY_MANUAL;
tuneRequest.dsp_freq = DcOffset_Hz;
return tuneRequest;
}
You shouldn't need to use POLICY_MANUAL at all, since the
tune_request_t supports offset-tuning directly:
https://files.ettus.com/manual/structuhd_1_1tune__request__t.html
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