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amplitude compensation in FIR filter

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saurabhmimani

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hi all,
I was designing a FIR filter for pulse shaping for QPSK transmitter that i will implement on FPGA, my prof told me to use a root raised cosine filter with amplitude compensation. I am confused that this amplitude compensation is same as windowing or it is something else.

plz guide me.
Thank you.
 

I think that in this case your prof said about amplitude multiplayer. Your root cosine filter pass not whole power of signal. You need multiplay filter response on 1/norm(h), when h - impuls filter response.
 
I think there is a sinx/x distortion in DAC this amplitude compensation is required for that distortion, but I don't know how to implement this amplitude compensation in RRC filter.

Thanks for your response.
 

Hmm.. you have only passive RRC filter. But for this you need some amplifiers, for example operational amplifier with resistors for point coefficient of multiplayer.
 

saurabhmimani said:
I think there is a sinx/x distortion in DAC this amplitude compensation is required for that distortion, but I don't know how to implement this amplitude compensation in RRC filter.
Click to expand...

You can use adaptive signal processing for the calculation of coefficients in RRC filter +sinc compensation.

Good book for start in this subject:

B. Widrow and S. D. Stearns. Adaptive Signal Processing.
 

thanks for reply.
Can you please more elaborate on sinc compensation, why is it required and how to do it?
 

sinx/x distortion in DAC gives ISI, need compensating filter.
You can calculate it in different ways: analytically, using the FDAtool in Matlab, simulating the distortion and correcting its using the equalizer...
 

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