Thank you very much Luca. I understood it very well. On Thu, Sep 8, 2016 at 2:16 AM, Luca Pascale <luca.pasc...@log-in.it> wrote:
> Hi Samith, > I suppose as noise source you can use something like > http://www.noisecom.com/products/components/nc520-low- > voltage-surface-mount-noise-source-200-khz-to-5-ghz > or similar. Some cheap solutions exist on ebay depending on the frequency > band you are interested in. > > If you connect the noise generator output to a well balanced power > divider the effect of the cabling is embedded in the estimated differential > phasors. Once calibration is done you can disconnect the power divider and > (using the same cables) connect antennae. The power divider is the critical > component because everything works in this way. > > For DF systems some devices exist to perform this task (DF Antenna band > switch...one of the band you can choose is the noise band for calibration). > Using that device you do not need to disconnect anything by hand ..just > switch the band. Anyway these devices are not cheap and if you are > interested on a single specific frequency they are not needed. > So basically depends on what you are doing. > > Luca > > > > > > 2016-09-07 11:39 GMT+02:00 Samith Abeywickrama <4s7sam...@gmail.com>: > >> Hi Luca, >> >> Thank you very much for your in detail explanation and it was really >> helpful for me. The question now I have is, how can I feed calibration >> signal? Is it a separate transmitter or some kind of wired link to usrp rx >> inputs? Thank you. >> >> Samith >> >> On Sep 7, 2016 5:11 PM, "Luca Pascale" <pascale.luca...@gmail.com> wrote: >> >> Hi Samith, >> >> to calibrate phase offset you can use a "calibration signal". >> Using a (phase) balanced power divider you can feed the 4 rf input with >> this calibration signal and use it to estimate differential phasors >> between the 4 channels taking one of them as reference (i.e. the first). >> You will have 3 significant differential phasors. >> >> You need to do this after each retune of the boards on a given frequency. >> Then you can apply the correction factors to the channels 2,3,4 once you >> acquired the signals you want to use to estimate DOAs. >> >> Calibration Signal: >> - CW tone if you are interested on a single specific frequency (not real >> world condition) >> - wideband noise >> Also depends on your implementation...(are you using a FFT Filter-bank >> and estimate DOAs for each FFT bins or ... are you working "narrowband"). >> To estimate correction factors I suggest to do some averaging. >> >> Moreover if your DF algorithm is (in some measure) sensitive to signals >> amplitude I suggest to perform also amplitude calibration not just phase >> calibration. >> You can estimate it using the differential phasors. >> >> Regards, >> Luca >> >> >> >> >> >Well, that's a bit up to your implementation. Probably, you want to have >> >something that you know the direction of and use it to find the >> >individual phase offsets, and find a complex de-rotating factor. >> >> >> >On 06.09.2016 10:52, Samith Abeywickrama wrote: >> >> Hi Marcus, >> >> >> >> Thank you very much. Btw, how can we calibrate the relative phase >> offsets? >> >> >> >> Samith >> >> >> >> On Tue, Sep 6, 2016 at 4:34 PM, Marcus M?ller >> >> <marcus.muel...@ettus.com <mailto:marcus.muel...@ettus.com>> wrote: >> >> >> >> Yes, you can Offering synchronization using external 10MHz and >> >> PPS signals is the purpose of the Octoclock-G ! >> >> >> >> However, the B210's LOs will have a random phase after every >> >> tuning, so you must calibrate the relative phase offsets every >> >> time you tune >> >> >> >> Best regards, >> >> >> >> Marcus >> >> >> >> >> >> On 06.09.2016 10:21, Samith Abeywickrama wrote: >> >>> Hi all, >> >>> >> >>> I'm going to implement MUSIC(Multiple Signal Classification) >> >>> algorithm to find Angle of Arrival of signal using two USRP >> >>> B210s. Therefore I have 4 antennas. But I need to synchronise my >> >>> two USRP B210s. May I know that can I use Octoclock-G with my >> >>> USRP B210s without any problem? Thank you in advance. >> >>> >> >>> -- >> >>> Best Regards! >> >>> Samith >> >> >> >> >> >> >> >> >> >> -- >> >> Best Regards! >> >> Samith >> >> >> > > > -- > Ing. Luca Pascale > LOG.IN S.r.l > Via Aurelia, 714 > 00165 ROMA - ITALY > Phone: +39-06-66417044 > Fax: +39-06-66411155 > Web: www.log-in.it > -- Best Regards! Samith
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