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@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 <i...@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@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@lists.ettus.com >> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >> > > _______________________________________________ > USRP-users mailing > listUSRP-users@lists.ettus.comhttp://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >
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