[ Calculating the amplitude of a signal source ]

GNU Radio
1

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2

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 R. [email protected]
wrote:

but they are too small to be considered as amplitudes at different points

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–
Muhammad Nazmul I.

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

3

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,

4

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.

5

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,

6

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7

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 R.
[email protected]wrote:

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

Ashish

–
Muhammad Nazmul I.

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