d=6.75;
D=48.5;
a=0;
n=16;
N=0:15;
fr = N/60;
f =0.5*n*(1+d*cos(a)/D)*fr; % Frequency to find
t = 0:0.001:10; % Create time vector
x = sin(2*pi*f*t); % create a signal
nfft = 64; % Window should be less than 256.
Fs = 1/dt; % Sampling frequency
window = hanning(nfft); % Use hanning as window
[Pxx, F] = calc_psd(x, nfft, Fs, window);
plot(F,Pxx); xlabel('Frequency [Hz]'); ylabel('Amplitude');