[USRP-users] WBX Frequency Response

Josh Blum josh at ettus.com
Fri Jun 1 15:52:45 EDT 2012



On 06/01/2012 12:35 PM, Simon HB9DRV wrote:
> Hi All,
> 
>  
> 
> After much keyboard pounding I've managed to get data from my WBX (Windows
> 7, 64-bit, Debug mode). Please look at the screenshot below, the sample rate
> ( using set_rx_rate() ) is 4MB. The response doesn't seem flat when the
> sample rate is anything above 2MB. Is this to be expected? I have set the RF
> Gain to the maximum of 38dB.
> 

MB = megabytes
Msps = megasamples per second

>  
> 
> ftp://ftp.ham-radio.ch/common/Screenshot-2012-06-01-203346.png
> 

Perhaps you are seeing the CIC filter rolloff. decimation =
100Msps/host_sample_rate. So for odd decimations, you get CIC filter and
no halfbands. Try an even decimation, you should see a flatter noise floor.

-josh




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