Forum: GNU Radio [ Calculating the amplitude of a signal source ]

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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 <rasteashish@gmail.com> 
wrote:

> but they are too small to be considered as amplitudes at different points
>
>
>
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--
Muhammad Nazmul Islam

Graduate Student
Electrical & Computer Engineering
Wireless Information & Networking Laboratory
Rutgers, USA.

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,

> 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.


Forgot to attach the plots (The baseband's center frequency, sampling 
rate
were retained and the gains were changed). Here they are.

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 
<rasteashish@gmail.com>wrote:

> I did notice significant change in the floating point values recorded when
> --
> Ashish
>
>
>
>


--
Muhammad Nazmul Islam

Graduate Student
Electrical & Computer Engineering
Wireless Information & Networking Laboratory
Rutgers, USA.

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,

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