[USRP-users] Daughterboard difference between 120/160MHz and 40MHz version

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[USRP-users] Daughterboard difference between 120/160MHz and 40MHz version

Martin Braun via USRP-users
Hi,

I'd like to know the exact difference between the same daughterboard type which comes with two bandwidth versions.

For applcations only needing relatively narrower bandwidth (<20MHz), will the 40MHz version provide better anti-aliasing against the interference from adjacent band?

Br, Hanwen

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Re: [USRP-users] Daughterboard difference between 120/160MHz and 40MHz version

Martin Braun via USRP-users
On 10/01/2016 04:14 PM, hanwen via USRP-users wrote:

> Hi,
>
> I'd like to know the exact difference between the same daughterboard
> type which comes with two bandwidth versions.
>
> For applcations only needing relatively narrower bandwidth (<20MHz),
> will the 40MHz version provide better anti-aliasing against the
> interference from adjacent band?
>
> Br, Hanwen
>
>
The 40Mhz version is intended for base platforms that sample at lower
rates---USRP1, N210.  Put one on an X3xx, for example, likely won't
   improve anti-alias response very much, since a lot of the filtering
is done digitally.   The filter roll-offs are designed to be roughly 60-80%
   of the appropriate Nyquist frequency for the preferred platform.    
The low-pass filters on these devices (WBX, SBX, CBX) are
   7-order elliptic filters (as I recall), and have excellent roll-off
characteristics.




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Re: [USRP-users] Daughterboard difference between 120/160MHz and 40MHz version

Martin Braun via USRP-users
Thanks, Markus.

Then it seems that I need a RF bandpass filter to reject the strong interference from neighbouring band. If you have further suggestion on this, please share with me.

Is the offset tuning affecting the anti-aliasing? Say, if I have a strong neighbour at the right side of my signal. Then is it better to make the Rx offset tuning a minus value, since in this way the actual carrier frequency is more far away from the neighbour interference.

I can experiment this next week, but better to know earlier.

BR, Hanwen



2016-10-01 22:24 GMT+02:00 Marcus D. Leech via USRP-users <[hidden email]>:
On 10/01/2016 04:14 PM, hanwen via USRP-users wrote:
Hi,

I'd like to know the exact difference between the same daughterboard type which comes with two bandwidth versions.

For applcations only needing relatively narrower bandwidth (<20MHz), will the 40MHz version provide better anti-aliasing against the interference from adjacent band?

Br, Hanwen


The 40Mhz version is intended for base platforms that sample at lower rates---USRP1, N210.  Put one on an X3xx, for example, likely won't
  improve anti-alias response very much, since a lot of the filtering is done digitally.   The filter roll-offs are designed to be roughly 60-80%
  of the appropriate Nyquist frequency for the preferred platform.    The low-pass filters on these devices (WBX, SBX, CBX) are
  7-order elliptic filters (as I recall), and have excellent roll-off characteristics.




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Re: [USRP-users] Daughterboard difference between 120/160MHz and 40MHz version

Martin Braun via USRP-users
On 10/01/2016 04:47 PM, hanwen wrote:

> Thanks, Markus.
>
> Then it seems that I need a RF bandpass filter to reject the strong
> interference from neighbouring band. If you have further suggestion on
> this, please share with me.
>
> Is the offset tuning affecting the anti-aliasing? Say, if I have a
> strong neighbour at the right side of my signal. Then is it better to
> make the Rx offset tuning a minus value, since in this way the actual
> carrier frequency is more far away from the neighbour interference.
>
> I can experiment this next week, but better to know earlier.
>
> BR, Hanwen
>
I'd experiment.  It depends on how closely-spaced the interferer is to
your passband.  But you can tweak the offset tuning a bit to keep
   the inteferer outside of your analog passband.   This works provided
that the signal isn't so strong that it is driving the first gain stages
   and mixer into non-linear operation--in which case, pretty much
nothing you do after that point will help much.



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