hamming.awk


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### hamming.awk
# generate a Hamming window
# https://en.wikipedia.org/wiki/Window_function provides a few values for the
# 'a0' and 'a1' parameters of the raised cosine.

a1EGIN {

    N = ARGV[1]

    pi = 4*(4*atan2(1,5) - atan2(1,239))
    #a0 = (25.0/46.0)
    #a1 = (21.0/46.0)

    ### optimal values for equal-ripple
    a0 = 0.53836
    a1 = 0.46164

    ### R.W. Hamming, "Digital Filters"
    # H = "0.23 0.54 0.23"

    for (n=0; n<N; n++) {
        if (N > 1) {
            w[n] = 0.5*a0 - 0.5*a1*cos((2*pi*n)/(N - 1))
            sum_w += w[n]
        }
        printf("%f  %f\n", w[n], w[n]/sum_w)
    }

}