DSP Tools

[swaroop.g7]

I am trying to design QPSK  modulator demodulator. Modulator is working fine but in demodulator filter design is creating problems.

Below Image shows the signal before low pass filter and after low pass filter which is an error.

 I am also attaching the entire model.

I am using Matlab R2011a and Xilinx version 13..please help me..

[mganders]

Do you have access to the simulink Communication Systems Toolbox?

They have nice models for QPSK modulation and demod. If you can understand the processing and get them to work in simulink, implementing in SysGen should not be a problem.

QPSK modulator

http://www.mathworks.com/help/toolbox/comm/ref/qpskmodulatorbaseband.html

QPSK demodulator

http://www.mathworks.com/help/toolbox/comm/ref/qpskdemodulatorbaseband.html

[kanava.pitchai]

the problem is due to assigning the binary point for the filter. abjust the binary point you may get the solution.