Along with linear convolution, circular shift and circular convolution are fundamental to many digital signal processing algorithms. The circular shift by delay no for a sequence of length N is denoted as:
x[(n - no)N], where (m)N = m modulo N.
Note: (m)N ∈ {0,1,...,N - 1} for any m.
Circular convolution is defined as
N-1
x[n] *N h[n] => Cx[k]h[(n-k)N], k=0
where the N in *N denotes the length of the sequence.
Consider a signal and impulse response for a sequence of length N = 4
x[n] = -28[n] + 8[n-1] + 38[n-2]; h[n] = 8[n] + 38[n-1].
a) Write down the sequence x[n] after a circular shift by 1 delay.
b) Compute the linear convolution x[n] * h[n]
c) Compute the circular convolution x[n] *N h[n]
d) Describe the relationship between circular convolution and the Discrete Fourier Transform (DFT)