Homework Set 4 Problem 5

It will be very important to get the complex conjugate symmetry about fsnew/2 correct.   An indication that you didn’t is getting a significant imaginary component when you inverse transform to get the upsampled signal.  If the symmetries in the frequency domain for a real signal in the time domain are correct, the imaginary part should be tiny (due to rounding errors) when compared with the real part, and then you can just set it to the real part.