why type 2 FIR filter cannot be used to design high pass filter?

can anybody explain why type 2 FIR filter cannot be used to design high pass filter?

Answer 1

[Honglei Chen]

This is because for Type II FIR, there is a zero corresponding to Nyqiust rate, i.e., half sampling frequency. However, a high pass filter needs to let that component pass, so it cannot be used for a high pass filter.

[pavan sunder]

how does Z=-1 corresponds to nyqiust frequency?

[Honglei Chen]

You can think of the unit circle as the frequency axis. Starting from (1,0), which corresponds to the 0 frequency. If you travel along the circle and come back to the starting point, it corresponds to Fs. Therefore, half the circle is just Fs/2, which corresponds to z = -1. HTH