Re: [Discuss-gnuradio] [ Calculating the amplitude of a signal source ]

[Nazmul Islam]

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 <address@hidden> 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.