Use fwind2 to design an approximately circularly symmetric two-dimensional bandpass filter with passband between 0.1 and 0.5 (normalized frequency, where 1.0 corresponds to half the sampling frequency, or π radians):

Create a matrix Hd that contains the desired bandpass response. Use freqspace to create the frequency range vectors f1 and f2.

[f1,f2] = freqspace(21,'meshgrid');

Hd = ones(21); (on what basis & how is this hd calculated)

r = sqrt(f1.^2 + f2.^2);

Hd((r0.5)) = 0;(what is the role of hd)