[USRP-users] N210 WBX annoying spurs while switching

Matt Ettus matt at ettus.com
Thu Oct 23 01:25:51 EDT 2014


Yes, but it is even better to ramp up at the beginning and down at the end,
and then pad a little bit with zeros.   If you ramp up and down smoothly
for 1us, you'll confine the emissions to about 1 MHz on either side.  All
bursty communication systems will do this, like Bluetooth, Wifi, even morse
code, and most newer standards even specify the ramping rate.

Matt


On Wed, Oct 22, 2014 at 10:08 PM, bob wole <bnwole at gmail.com> wrote:

> So you are suggesting that I should zero pad samples at start and end of
> my burst to avoid this ?
>
> On Wed, Oct 22, 2014 at 9:16 PM, Matt Ettus <matt at ettus.com> wrote:
>
>>
>> When you start and stop transmission without smoothly ramping the signal
>> to zero at the beginning and end, you will create wideband spurs.  Just
>> think about it as amplitude modulation.  Even if you are transmitting a
>> pure sine wave, if you turn it on and off quickly, it will create out of
>> band spurs.  Hams call this keyclicks.
>>
>> Matt
>>
>>
>> On Wed, Oct 22, 2014 at 1:25 AM, bob wole via USRP-users <
>> usrp-users at lists.ettus.com> wrote:
>>
>>> I noticed that there are a lot of significant spurs generated in the
>>> output of WBX, on different frequencies randomly, when I use tx_time,
>>> tx_sob_tx_eob tags. I do not see these spurs if I transmit continuously.
>>> These spurs appears only when I start and stop transmission using stream
>>> tags.
>>> How can I get rid of these spurs and what is the cause?
>>>
>>> -
>>> Bob
>>>
>>> _______________________________________________
>>> USRP-users mailing list
>>> USRP-users at lists.ettus.com
>>> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>>>
>>>
>>
>
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