FPGA Central

My name is Victor and currently I tried to create a SDM system.
I am using a Low Pass Filter to clean my input signal and I'm using 3400
Hz LPF.
At first, I think that I should use the same LPF for the demodulation
process. Because I get the impression that the input and output signals
form SDM are the same.
But at my surprise, if I use 3400 Hz LPF for demodulation process, I'll
get a static signal and full of noise.
I can clean the noise if I use 1500 Hz LPF for demodulation process.
And I get a different input and output signal from my SDM system.
My question is why can I use the same LPF for the modulation and the
demodulation process?
Do I have to use 1500 Hz LPF for SDM demodulation process? And can you
explain why should I use 1500 Hz LPF for SDM demodulation process?

The next problem I have is the problem with my integrator in the SDM.
I'm currently using an Operational Amplifier for my integrator. I'm using
2.5 Volt power supply for the reference voltage connected to invertin
pin
in the Op-Amp.
My question is can I use 2.5 Volt for reference voltage, or should I use
another reference voltage? Can you explain your answer?


This message was sent using the Comp.DSP web interface o
www.DSPRelated.com