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Forum: µC & Digital Electronics Data acquisition


Author: jeorges FrenchRivera (Company: xlue) (khal1985)
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Hi everyone,

I have a square signal at the output of a photodetector. The frequency 
of this signal is MHz. It's a noisy signal.
First of all, i want to sample this signal with and ADC (fs=10 MHz, 14 
bit). Then filter the signal converted to recover the original signal 
without noise.

Can someone help me about choosing the best platform to that( FPGA, µC, 
DSP or raspberry ...)please ?

I need also you help concerning the choice of the ADC.
Thanks in advacnce.

Best regards

Author: 6a66 (Guest)
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jeorges F. wrote:
> First of all, i want to sample this signal with and ADC (fs=10 MHz, 14
> bit). Then filter the signal converted to recover the original signal
> without noise.

Hello jeorges,

are you sure you require this performance? The converters for this task 
are not cheap (around 30USD per piece) and so is the input stage for the 
converter. Next is the performance for "filtering" such a data stream in 
reatime.
Can you describe the problem a little more to check whether other 
solutions would be easier?

rgds

Author: Lothar Miller (lkmiller) (Moderator)
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jeorges F. wrote:
> to recover the original signal without noise.
Is the original signal "noiseless"? Where does it come from?
Which part of the signal chain is noisy?
What must be done with the signal afterwards?

Author: jeorges FrenchRivera (Company: xlue) (khal1985)
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thank you for you answers Lothar & 6a66.

This is the description of the problem:

the purpose of the system is to treat a sinusoidal input signal, 
attenuated and noisy so as to output a signal of the same frequency but 
having a high ratio of signal to noise. the output of this system will 
provide a square wave.

The input is a sinusoidal signal e(t) of frequency fr, marred by 
predominantly Gaussian noise and possibly having a DC component.
This signal has the form :
 e (t) = A (t) sin (fr.t) + n (t) (A (t) amplitude of the signal, n (t) 
is the additive Gaussian noise and DC (t) the DC component).
- e(t) is an analog signal supplied by a photodiode and a mounting 
Transimpedance.
The features  of e(t)are :
-5 V <e (t) <+ 5V
A (t)> 20 mV
SNR> 5 dB
Fr = 1 MHz

The goal is to have a square frequency analog output signal, compatible 
logic level (0 V and 3.3 V low state high State)
the phase difference between e(t) and s(t) should remain relatively 
constant with a phase noise less than 0.05 °.

Best regards

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