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From: | Samith Abeywickrama |
Subject: | Re: [Discuss-gnuradio] Two USRP B210s with Octoclock-G (Samith Abeywickrama) |
Date: | Wed, 7 Sep 2016 17:39:40 +0800 |
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
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
>> <address@hidden <mailto:address@hiddencom >> 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
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