Re: [Discuss-gnuradio] replica outband

[Gaetano Mendola]

On Thu, Jul 28, 2011 at 6:02 PM, Matt Ettus <address@hidden> wrote:
> On 07/28/2011 02:58 AM, Gaetano Mendola wrote:
>> Hi all,
>> I'm transmitting my signal with 5Mhz bandwidth with a carrier of 70Mhz,
>> analyzing output spectrum I see some "replicas" outside the bandwidth
>> (see attached image).
>> I'm using a WBX, will the uhd::usrp::multi_usrp::set_tx_bandwidth remove 
>> those
>> replicas? I don't see any filter after the I/Q modulator (ADL5386).
>>
>> Is this intended ?
>
>
> Those are odd harmonics, which are expected.  In any application where
> you are transmitting over the air with significant power, you will need
> to filter out the odd-order harmonics.
>
> The WBX has such wide frequency coverage that it is impractical to have
> enough filters to do this for the whole range.  This is why we have the
> grand-daughterboard -- you can either modify the filter on there
> (minicircuits has a whole range of filters to cover the band), or make a
> custom filter board for your specific needs.

Thank you for the explanation, I did immagine that seeing that there is no
filter after the I/Q modulator I did ask just to be sure.

Regards
Gaetano



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