thanks a lot for these explanations. matis
Le 27/03/2018 à 11:52, Derek Kozel a écrit : > Hi Matis, > > The USRPs are generally designed following the rule of thumb that the > passband is 80% of > sampling rate. That allows for filters, both analog and digital, to be > reasonable to > construct. The TwinRX is tuning its analog center frequency to 50 MHz. With > the 100 MS/s > complex sample rate frequencies from DC to 100 MHz are visible, but the > filters, > amplifiers, and other elements of the receiver will degrade the receive > performance > below 10 MHz. As you've found though, the degradation is very acceptable for > some > applications. > > Marcus actually authored an app note looking at the same question with the UBX > daughterboard. > https://kb.ettus.com/Experiments_with_the_UBX_Daughterboard_in_the_HF_Band > > Regards, > Derek > > On Sat, Mar 24, 2018 at 6:15 AM, Matis Alun via USRP-users > <usrp-users@lists.ettus.com > <mailto:usrp-users@lists.ettus.com>> wrote: > > yes, its seems that we loose several dBs but which can be widely > compensated by the > extremely large TwinRx gain range. > > > Le 24/03/2018 à 06:38, Marcus D. Leech via USRP-users a écrit : > > On 03/24/2018 12:41 AM, Matis Alun via USRP-users wrote: > >> Hi, > >> > >> The TwinRx frequency specifications is from 10MHz to 6GHz. > >> > >> However, some tests shows that I can select the center frequency > around 10 MHz with a > >> sampling frequency of 25MHz > >> which allows to make some acquisitions in the HF band (3-30 MHz) with > a very good > quality. > >> > >> My question is: why the specs limits to 10 MHz ? Is the RF part have > degraded > performances > >> under this frequency ? > >> > >> Below this question is: we have to deliver a big HF (3-30 MHz) system > to a > customer. The > >> acquisition part is actually built with > >> 2 x N210 with LFRX daughter boards. Due to the lack of chain gain of > this > configuration, > >> we add some RF pre-amplifiers > >> in order to have good RF levels at the LFRX input. > >> Maybe that this configuration can be replaced by 1x X300 + TwinRx (we > didn't make > this > >> choice because of the TwinRx specs) ? > >> > >> Regards, > >> > >> matis > >> > >> > > My guess is that signals below 10MHz can be received, but the RF > amplifiers in the > > low-band portion of the TwinRx likely fall off in gain quite a bit > > below 10MHz. > > > > > > > > _______________________________________________ > > USRP-users mailing list > > USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> > > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com <mailto:USRP-users@lists.ettus.com> > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> > >
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