Re: [Discuss-gnuradio] [ Calculating the amplitude of a signal source ]
** (i) How many *bytes* does each I or Q component take? -- Ashish For complex samples, the file-sink writes native, IEEE-754 single-precision floating-point values into the file, with I and Q interleaved. IEEE-754 single-precision is 32-bits, and is the native binary format used by most CPUs. -- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] [ Calculating the amplitude of a signal source ]
** (i) How many *bytes* does each I or Q component take? -- Ashish ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] [ Calculating the amplitude of a signal source ]
Hi Nazmul, I have always found it difficult to measure the amplitude of each sample > using the floating point strengths. Things like frequency offset will > change the result and affect the individual samples. > I thought I need to do some calibration to correlate the value shown in the y-axis of the Scope sink (some factor X amplitude of the source signal) to the signal strength sent from the generator. > However, calculation of average power based floating point strength works > for me. For example, I have measured the power of a received sinusoid using > FFT. The strength of the floating point outputs of FFT > scale expectantly with the transmitted power. > Thanks for this suggestion. I will do this experiment. Best, -- Ashish Raste ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] [ Calculating the amplitude of a signal source ]
Hi Marcus, What daughter card are you using? What is your tuned frequency? What is > the frequency of the signal source? What is the amplitude of > the signal source? > I'm using the USRP N210 with WBX daughterboard. Am having a vector signal generator which is sending the signal at 400.01M frequency and the USRP source block's frequency is set to 400M. -- Ashish Raste ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] [ Calculating the amplitude of a signal source ]
Hi Ashish, I have always found it difficult to measure the amplitude of each sample using the floating point strengths. Things like frequency offset will change the result and affect the individual samples. However, calculation of average power based floating point strength works for me. For example, I have measured the power of a received sinusoid using FFT. The strength of the floating point outputs of FFT scale expectantly with the transmitted power. Thanks, Nazmul On Mon, Dec 10, 2012 at 11:09 PM, Ashish Raste wrote: > Hi Nazmul, > Thanks for replying. > > > Change the Receiver gain and see if the strength/amplitude of the floating >> points change or not. If they do, then you are doing the right thing. You >> can place a signal calibrator (e.g. some variable attenuator) to calibrate >> the floating point strengths and actual received power. > > > I did notice significant change in the floating point values recorded when > the gain was changed. Have attached the plots of those values for the gain > values of 20 dB and 25 dB. > > I also see that these values do not depict the sine wave (the source being > a sine wave). So can I assume that these floats are not exactly the > amplitudes but they have some relation to the amplitude of the signal? How > can I calculate the amplitude from this recorded data (file_sink)? > > Thanks and Regards, > > -- > Ashish > > > > -- Muhammad Nazmul Islam Graduate Student Electrical & Computer Engineering Wireless Information & Networking Laboratory Rutgers, USA. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] [ Calculating the amplitude of a signal source ]
Hi Nazmul, Thanks for replying. Change the Receiver gain and see if the strength/amplitude of the floating > points change or not. If they do, then you are doing the right thing. You > can place a signal calibrator (e.g. some variable attenuator) to calibrate > the floating point strengths and actual received power. I did notice significant change in the floating point values recorded when the gain was changed. Have attached the plots of those values for the gain values of 20 dB and 25 dB. I also see that these values do not depict the sine wave (the source being a sine wave). So can I assume that these floats are not exactly the amplitudes but they have some relation to the amplitude of the signal? How can I calculate the amplitude from this recorded data (file_sink)? Thanks and Regards, -- Ashish ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
Re: [Discuss-gnuradio] [ Calculating the amplitude of a signal source ]
Change the Receiver gain and see if the strength/amplitude of the floating points change or not. If they do, then you are doing the right thing. You can place a signal calibrator (e.g. some variable attenuator) to calibrate the floating point strengths and actual received power. Thanks, Nazmul On Mon, Dec 10, 2012 at 4:03 AM, Ashish Raste wrote: > Hi all, > > For calculating the amplitude (assume RMS amplitude) of a signal source, I > first tried to record the received samples (I'm using a vector signal > generator) in a file_sink and then thought to use it for my calculation. > The frequency of the signal from the signal generator was set to 400M and > the sampling rate of the USRP source block (in GRC) was set to 2M. Have > attached the block diagram below:[image: Inline image 1] > > I am able to extract the float (the data type I used) values from the file > but they are too small to be considered as amplitudes at different points > in time i.e the maximum value was 1.03e-09 and minimum was -8.4e-13. > > Can anyone please tell me how I can calculate the amplitude of any such > signal in real-time? Is this approach of calculating amplitude the right > one OR is there any other smarter way to do it? > > Thanks and Regards, > -- > Ashish > > > > > ___ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > -- Muhammad Nazmul Islam Graduate Student Electrical & Computer Engineering Wireless Information & Networking Laboratory Rutgers, USA. ___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
[Discuss-gnuradio] [ Calculating the amplitude of a signal source ]
Hi all, For calculating the amplitude (assume RMS amplitude) of a signal source, I first tried to record the received samples (I'm using a vector signal generator) in a file_sink and then thought to use it for my calculation. The frequency of the signal from the signal generator was set to 400M and the sampling rate of the USRP source block (in GRC) was set to 2M. Have attached the block diagram below:[image: Inline image 1] I am able to extract the float (the data type I used) values from the file but they are too small to be considered as amplitudes at different points in time i.e the maximum value was 1.03e-09 and minimum was -8.4e-13. Can anyone please tell me how I can calculate the amplitude of any such signal in real-time? Is this approach of calculating amplitude the right oneOR is there any other smarter way to do it? Thanks and Regards, -- Ashish <>___ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
