[USRP-users] DOA with N310 or X310+TwinRX

Robert.Poehlmann at dlr.de Robert.Poehlmann at dlr.de
Mon Jan 27 09:56:54 EST 2020

With external LO its 300 MHz – 4 GHz, check footnote [3] from https://www.ettus.com/all-products/usrp-n310/. LO has to be supplied at twice the carrier freq.

Currently we use 4 channels. You can find an example how to do the calibration here: https://github.com/EttusResearch/gr-doa
gr-doa was written for TwinRX, but can be adapted.

Phase noise behavior of N310 and N320/1 could be different, as N310 uses an RFIC and N32/1 use discrete components. This could be important if you want to operate in the small sample regime.

From: USRP-users [mailto:usrp-users-bounces at lists.ettus.com] On Behalf Of Sammy Welschen via USRP-users
Sent: Monday, January 27, 2020 3:40 PM
To: usrp-users at lists.ettus.com
Subject: Re: [USRP-users] DOA with N310 or X310+TwinRX

Thank you for the information Robert! Isn't it 6 GHz? However, 4 GHz would also be sufficient for me.

How many channels does your system have?  I suppose you use some algorithm for phase calibration after power cycling? I plan to do the same, so the 180 deg ambiguity should be manageable.

I looked at the N32x, however, they cost twice as much and I dont't plan on using 200 MHz of bandwidth. If I have an external LO signal I can feed it to the N310, so the only difference between N310 and N32x in this regard would be that I need to generate the LO externally when using the N310, right?

<Robert.Poehlmann at dlr.de<mailto:Robert.Poehlmann at dlr.de>> schrieb am Mo., 27. Jan. 2020, 14:42:
We use the N310 for DoA estimation, however:

-          you are limited to 4 GHz

-          after power-cycling you get a 180° ambiguity between the two radios (I do not know if this could also happen when you just change the LO frequency)

If you want to have >4 channels, have a look at the new N320/N321. No experience with those, but apparently they can do LO distribution.

Also take into account if maybe later in the project you want to be able to transmit, which you cannot do with TwinRX.


From: USRP-users [mailto:usrp-users-bounces at lists.ettus.com<mailto:usrp-users-bounces at lists.ettus.com>] On Behalf Of Sammy Welschen via USRP-users
Sent: Monday, January 27, 2020 2:19 PM
To: usrp-users at lists.ettus.com<mailto:usrp-users at lists.ettus.com>
Subject: Re: [USRP-users] DOA with N310 or X310+TwinRX

Thank you Marcus! So the N310 would be the way to go? I was unsure since the TwinRX is recommended for phase coherent applications.

Marcus D. Leech via USRP-users <usrp-users at lists.ettus.com<mailto:usrp-users at lists.ettus.com>> schrieb am So., 26. Jan. 2020, 18:57:
On 01/25/2020 11:43 AM, Sammy Welschen via USRP-users wrote:
> Dear all,
> I am planning a system with 5-10 channels that is capable of DOA
> estimation.
> Concerning the calibration of the resulting array, would there be a
> difference between a system made up of N310 and one made up of X310
> with TwinRX boards? Would there be other important differences that
> influence estimation performance?
> As I understand it, the TwinRX allows LO sharing between the boards in
> a single X310, but this would not help me if I have two or three X310.
> On the other hand, the N310s could be connected to a shared LO.
> Are the following thoughts correct?
> Suppose I turn on my system. Then I have to calibrate phase offsets
> between channels in any case. Now I change the center frequency. If I
> have N310s without shared LO, I have to recalibrate. Same for the
> X310s, since LOs are shared only internally. If I have N310s with a
> shared LO, I do not have to recalibrate.
> If I restart the system, I have to recalibrate in any case.
> The devices would by synchronized with PPS in any case and with the 10
> MHz reference if no external LO is used.
> What is the better choice for DOA estimation (N310 or X310 with TwinRX
> or something different)?
> Thank you very much
> Sammy

Your characterization of the two scenarios is correct.

There may be some folks on this list who have implemented DOA schemes,
but likely few-to-none who have done it on both X310 and N310
   and can comment on the differences they encountered.

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