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 N.

MSc Communication Engineering

Chalmers University ot Technology, Sweden.