[USRP-users] The problem with setting the frequency of USRP B 210.

Ivan Zahartchuk adray0001 at gmail.com
Tue Mar 12 10:26:59 EDT 2019


Sorry, but I do not fully understand how to work with frequency offset. For
example, I have an instantaneous bandwidth of 25 MHz. Then I set the
frequency offset to 13 MHz? Because my amplitude decreases, but the peak
still remains with a large amplitude.

вт, 12 мар. 2019 г. в 15:13, Marcus D. Leech via USRP-users <
usrp-users at lists.ettus.com>:

> On 03/12/2019 05:13 AM, Ivan Zahartchuk via USRP-users wrote:
>
> Thanks for the information. But do not tell me why then in N 210 with sbx
> there is no such problem? Just in the N 210 I am not satisfied with the
> large central frequency. As I understand this is a surge in direct current. But
> I can't get rid of him. And sometimes there are problems with the mirror
> channel. If you have any advice on this, I will be extremely grateful.
>
> Because the SBX is a different piece of hardware, with different
> architecture.  It happens to tune a lot faster.
>
> The DC offset can be dealt with using offset tuning:
>
> https://files.ettus.com/manual/page_general.html
>
> If you are seeing image frequencies, then use the
>
> uhd_cal_rx_iq_balance
>
> Utility on your N210 to caclulate and record calibration parameters that
> will help to reduce I/Q imbalance.  DC offset and I/Q imbalance are
>   inherent in a direct-conversion receiver design.  These imbalances need
> to be calibrated out.  In the N210/SBX, host-side software does
>   "static' measurement of these (using the above mentioned tooling) and
> records a calibrations file.  Those calibrations are then applied
>   at run-time to compensate.
>
> In the B210, the AD9361 chip does I/Q correction (and other corrections)
> dynamically, which can cause it to be slower in tuning--because it
>   does the measurements whenever you re-tune.
>
> See:
>
>
> https://wiki.analog.com/resources/eval/user-guides/ad-fmcomms1-ebz/iq_correction
>
> For a discussion
>
>
> пн, 11 мар. 2019 г. в 17:17, Ian Buckley <ianb at ionconcepts.com>:
>
>> Ivan,
>> When the AD9361 is retuned, recalibration of various RF circuits may
>> (need to) reoccur. The device driver looks how far you have retuned from a
>> previous frequency, and if it exceeds a certain distance rerun’s this
>> calibration, which takes time.
>> Since Analog devices envisaged that this chip might need to be used in
>> applications where fast hopping is required, it does have the ability to
>> store multiple calibration settings locally in the radio and switch between
>> them quickly, but this is not functionality that is used in basic operation
>> under UHD. We may well have put API hook’s in there so you can manually
>> call this functionality under UHD, but I can’t recall. Take a look at ADI’s
>> documentation for more info.
>>
>> -Ian
>>
>> > On Mar 11, 2019, at 7:49 AM, Ivan Zahartchuk via USRP-users <
>> usrp-users at lists.ettus.com> wrote:
>> >
>> > Hello. I have a problem with the usrp b200 board. I need a fast
>> frequency tuning for spectrum analysis. But when I increase the band over
>> 200 MHz, that is, more than 8 frequency adjustments, I have problems with
>> time. It increases dramatically.
>> > Here is the code section where I measure the execution time of the
>> frequency setting function:
>> > for i, freqq in enumerate (freq):
>> >
>> >             recv_samps = 0
>> >             self.usrp.set_rx_rate (bandwich [i])
>> >             start = time.time ()
>> >             self.usrp.set_rx_freq (lib.types.tune_request (freqq))
>> >
>> >             print (time.time () - start)
>> > And I get the following results:
>> > 0.154153108597
>> > 0.00300002098083
>> > 0.0029628276825
>> > 0.00299215316772
>> > 0.00298380851746
>> > 0.153974056244
>> > 0.153841018677
>> > 0.00304222106934
>> > 0.00305104255676
>> > 0.0030951499939
>> > 0.0030038356781
>> > 0.153944015503
>> > 0.153861045837
>> > 0.00292587280273
>> > 0.00306510925293
>> > 0.00301003456116
>> > 0.0029399394989
>> > With USRP N 210 there is no such problem. Tell me why this problem
>> occurs and how can it be solved?
>> > Thanks in advance. Ivan
>> > _______________________________________________
>> > USRP-users mailing list
>> > USRP-users at lists.ettus.com
>> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>
>>
>
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