[USRP-users] LFRX antialiasing
Marcus D. Leech
mleech at ripnet.com
Tue Apr 30 15:37:51 EDT 2013
On 04/30/2013 03:31 PM, mepard wrote:
> In the "Receive FPGA pipeline overflow?" thread, on Apr 30, 2013, at
> 12:12 PM, Marcus D. Leech <mleech at ripnet.com
> <mailto:mleech at ripnet.com>> wrote:
>> Also, if you aren't band-limiting your input to handily-below the
>> Nyquist frequency (50Mhz, in the case of the N210, because the ADC
>> samples at
>> 100Msps), then you'll get aliases folded into the signals after
>> they're sampled.
> So we need external filtering for the LFRX board? I knew this was true
> for the BasicRX (1 - 250 MHz), but I had the impression this wasn't
> necessary for the LFRX (0 - 30 MHz).
There is a 30Mhz low-pass on the output of the LF_RX differential
amplifiers, but I'm not sure that the out-of-band attenuation is all
that terribly deep.
If there's a possibility of strong signals above 30Mhz, I'd put in an
The main "draw" of the LF_RX is that it goes down to DC on the input,
whereas on the BASIC_RX, its response starts to roll off quite a bit
Shirleys Bay Radio Astronomy Consortium
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