Re: [Discuss-gnuradio] Spectrum at 1 GHz

[Josh Blum]

your samples rates do not match:

usrp2 rate is 100e6/1e6

fft sink rate: 2e3

-Josh

On 04/12/2010 12:29 AM, Umair Naeem wrote:
> I have a query regarding flow graph in GRC.
> I am trying to get spectrum from DBS_RX daughter board using GRC. I have used 
> three blocks as
>
> USRP2 Source -->  FFT Filter -->  FFT Sink
>
> They have following parameters,
>
> USRP2 Source:
> Decimation 1M
> Frequency 1G
> Gain (dB) 0
>
> FFT Filter:
> Decimation 1
> Taps firdes.complex_band_pass(1.0, 3000, -0.05e3, 0.05e3, 5, 
> firdes.WIN_HAMMING, 0)
>
> FFT Sink:
> Sample Rate 2K
> Baseband Frequency 1K
> FFT Size 512
> Refresh Rate 30
>
>
> I need to display shows frequency spectrum centered at 1 GHz. Since I am using 
> decimation of 1M, the frequency is lowered down to 1K. I filter it using FFT 
> bandpass filter with 100 Hz bandwidth. The fft sink shows spectrum at around 1 
> KHz. The problem is if I do not use decimation, the GRC seems to be very slow 
> (may be processing 1 GHz at  GHz sample rate is too much). I need to make a FFT 
> plot showing spectrum at 1 GHz. How Can I accomplish this?
>
>
> Regards,
> Umair Naeem
> MSc Communication Engineering
> Chalmers University ot Technology, Sweden.
>
>
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