RE: [Discuss-gnuradio] Spectrum at 1 GHz
Hi Umair I believe the decimation factor you have chosen is beyond the maximum allowed (I think, from memory this is 512, which is well less than 1M = 1 times 10^6). It seems you are trying to sample the passband signal to show a spectrum at 1 GHz, however a digital-down conversion is performed at the receiver, so you should see a signal at baseband. You should not need to use such a high sampling rate - ideally, Nyquist rate (based on the signal bandwidth when downconveted to baseband) will suffice. Regards Ian. -Original Message- From: discuss-gnuradio-bounces+ian.holland=rlmgroup.com...@gnu.org [mailto:discuss-gnuradio-bounces+ian.holland=rlmgroup.com...@gnu.org] On Behalf Of Umair Naeem Sent: Monday, 12 April 2010 4:59 PM To: discuss-gnuradio@gnu.org Subject: [Discuss-gnuradio] Spectrum at 1 GHz 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. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] Spectrum at 1 GHz
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. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
RE: [Discuss-gnuradio] Spectrum at 1 GHz
Hi Umair There is a setting in the USRP2 source block that lets you set the carrier frequency. This should be 1e9 (i.e. 1G). What is the signal you are trying to receive? Ian -Original Message- From: Umair Naeem [mailto:ar...@student.chalmers.se] Sent: Monday, 12 April 2010 8:22 PM To: Ian Holland Subject: RE: [Discuss-gnuradio] Spectrum at 1 GHz So If I need to see in the baseband region then what should be the parameters of USRP2 source for my case (i.e. Decimation and Frequency). Should I give 1 GHz in the frequency parameter or in the baseband region? Thanks for help... Regards, Umair Naeem MSc Communication Engineering Chalmers University ot Technology, Sweden. From: Ian Holland [ian.holl...@rlmgroup.com.au] Sent: Monday, April 12, 2010 9:55 AM To: Umair Naeem; discuss-gnuradio@gnu.org Subject: RE: [Discuss-gnuradio] Spectrum at 1 GHz Hi Umair I believe the decimation factor you have chosen is beyond the maximum allowed (I think, from memory this is 512, which is well less than 1M = 1 times 10^6). It seems you are trying to sample the passband signal to show a spectrum at 1 GHz, however a digital-down conversion is performed at the receiver, so you should see a signal at baseband. You should not need to use such a high sampling rate - ideally, Nyquist rate (based on the signal bandwidth when downconveted to baseband) will suffice. Regards Ian. -Original Message- From: discuss-gnuradio-bounces+ian.holland=rlmgroup.com...@gnu.org [mailto:discuss-gnuradio-bounces+ian.holland=rlmgroup.com...@gnu.org] On Behalf Of Umair Naeem Sent: Monday, 12 April 2010 4:59 PM To: discuss-gnuradio@gnu.org Subject: [Discuss-gnuradio] Spectrum at 1 GHz 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. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
