RRC Matched Filter Design

Thanks KAZ for assisting me throughout this project :)

First, I filtered the signal without noise... the output is pretty much the same as the input (in Matlab ) that's why I thought I might need to implement the matched filter in a different way. Later, I realized after many readings that matched filtering is useful in case of a polluted signal with AWGN. I added the noise and I could notice the difference!

No need to swear at those unpractical dsp writers :P Writers whom I read for are practical I believe:

[1] Louis Litwin, "Matched filtering and timing recovery in digital receivers", rfdesign.com, September 2001

[2] Eric Jacobsen, "Pulse Shaping in Single-Carrier Communication Systems"

Now I have a question, when I simulated in ModelSim, the demodulator is arranged as follows:

1) Mixer

2) then signal is passed to CIC decimation filter to remove high component frequency and to relax subsequent signal processings.

3) after that, I pass to RRC.

CIC is clocked at 100 MHz, RRC is clocked at 50 MHz (just like modulator if you remember)

I noticed that RRC's output is decimated by 2! It should produce a 2.8571 MSPS signal, instead it produces a 1.4285 MSPS.

I clocked it at 100 MHz, the output is 2.8571 MSPS again.

Question is, why is that? Although 2.8571 MHz is less than 50 MHz.