I have a digital signal from EEG recording. I need to filter 50 Hz frequencies and 0.5 to 120 Hz, so I've tried this: 1. I designed a notch filter with Matlab. 2. I used fft to transform the signal to frecuency domain. 3. I applied the notch filter. 4. I used ifft to get back to time domain. The problem is that when I use ifft, I understand I'd get a real vector, but I get a complex one. I've also tried to modify something (just a digit) from the complex vector that I get with fft and when I use ifft, I don't get the original, but a complex one. Can anybody tell me what's wrong? Thank you very much.