Re: [Discuss-gnuradio] diminishing returns with increasing frequency offset

[Martin Braun]

Tom,

you'll need to tell us more about what you're doing and what you've tried.

Cheers,
Martin

On 03/17/2016 03:36 PM, tom x wrote:
> It's strange but the only sampling rate that works is 4 MHz; Packets are
> not decoded when the sampling rate is set above this rate.
> 
> Thanks,
> Tom
> 
> On Thu, Mar 17, 2016 at 7:33 PM, Martin Braun <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     What's your sampling rate? The further you go towards the edge of your
>     Nyquist zone, the more the anti-aliasing filter might be kicking in.
> 
>     Cheers,
>     Martin
> 
>     On 03/17/2016 10:23 AM, tom x wrote:
>     > Hi,
>     >
>     > My setup is a USRP N210 receiving from a transmitter sending a few
>     > packets a second. (The packets are decoded with Bloessl's 802.15.4 PHY
>     > block if it matters)
>     >
>     > Let's say the transmitter is sending data on frequency f_t.
>     >
>     > I set the USRP to receive on f_t plus an offset f_o.
>     > The next block is a frequency xlating FIR filter centered at -f_o.
>     > This is intended to correct the offset.
>     >
>     > I made a slider block for f_o and allowed it to vary between 0 and
>     3MHz.
>     > I need an offset of a few MHz for my application. However, the
>     number of
>     > packets received seems to drops as I increase f_o. I get almost no
>     > packets after f_o is increased over 0.5MHz.
>     >
>     > The overall purpose of this is to carve two channels out of the
>     received
>     > bandwidth with two frequency xlating FIR filter blocks, with the USRP
>     > tuned between the channels and the filter blocks centered at offsets
>     > that put them on the channel peaks. As explained above, if the
>     offset is
>     > too big, it stops working. Why do you think this is happening?
>     >
>     > Thanks,
>     > Tom
>     >
>     >
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