amplitude compensation in FIR filter

[saurabhmimani]

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.

 

[asjohnas]

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.

 

[saurabhmimani]

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.

 

[asjohnas]

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.

 

[ux]

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.

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.

 

[saurabhmimani]

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

 

[ux]

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...