I have a question regarding Modulation and Demodulation.
In question 5.21 (b) from the "Discrete-time Signal Processing" book by Oppennheim, he asks to find out the type of filter used in the attached figure:
The question is what is the effect of $(-1)^n$ on the original filter and y[n].
I saw the answer to be high-pass filter, but I am not sure why.
Please help
Thanks