I am trying to transmit OFDM signal in pass-band based on RRC filter, but what I noticed that the signal before the RRC filter is completely different compared with signal after the RRC filter (It means the signal is destroyed when using RRc filter). I tried to follow the signal without using any channel, I noticed the issue starts when using the RRC filter. For example, I used only the system as follows:
signal --> ifft --> upsampling --> RRC filter --> RRC filter --> downsampling --> fft --> received signal
What is expected is the
received signal equals to
signal, but I get very different results.
what I get is a different signal. Why ? should that be equal? I think I must be the same. Finally , when I delete the filter, Everything is OK.