[USRP-users] Ettus UBX-160 vs SBX-120

Kyeong Su Shin ksshin at uw.edu
Mon Jul 3 04:52:19 EDT 2017


To whom it may concern:

You don't need 160MHz, but that is the filter bandwidth of the
daughterboard. It WILL give you 160MHz of signal (=120MHz + 40MHz worth of
aliasing), even if though all you want is 120MHz of bandwidth.

I don't use X3x0 series, so I am not sure what configurable true sampling
rates are out there, but if you set your sampling rate to 160MHz or higher
and decimate the data to lower rates using hardware decimators in your
x310, this problem does not happen (the digital decimator will apply low
pass filters). That is why you can do 100MS/s (sample at 200MS/s ->
decimate to 100MS/s).

Regards,
Kyeong Su Shin

On Mon, Jul 3, 2017 at 1:35 AM, Simon Olvhammar via USRP-users <
usrp-users at lists.ettus.com> wrote:

> Hi,
>
> I am not sure if I understand correctly.
> How are the ADC to slow if I use a master clock rate of 120 MHz and
> sampling rate of 120 MHz on a UBX-160? I don't need 160 MHz bandwidth only
> 120 MHz.
>
> Regards
> Simon
>
> On 06/28/2017 04:12 PM, Sylvain Munaut wrote:
>
>> Hi,
>>
>>
>> We currently running a system with a Ettus x310 and a SBX-120.
>>> We also a have UBX-160 daughter board.
>>>
>>> For several reasons, mainly due to computer performance limitations, we
>>> can
>>> only run with a complex sampling rate of 120 MHz.
>>> My question is if I will see any improvement in performance, e.g. filter
>>> characteristics, if I instead use the UBX-160 and run it at 120 MHz
>>> compared
>>> to SBX-120 at 120 MHz or are they similar?
>>>
>> You can't do that.
>>
>> If you have the master clock-rate at 120 MHz and use a 160 MHz wide
>> daugtherboard, you will get aliasing because the ADC are too slow.
>> You'd have to go to a 100 MHz samplerate for it to work. (200 MHz
>> sampled by the ADC then HW decimated by 2 to 100 Msps).
>>
>> Cheers,
>>
>>     Sylvain
>>
>
>
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