For loop and Fast Fourrier Transfrom

Dear colleagues, I have a question related to Fast fourier transfrom. I want to calculate the phase and make FFT to draw power spectral density. However when calculate the phase "theta", there was some errors. So sorry because I am new to Matlab. This is my program code. Please help. Thanks so much !

n = 1:32768;

T = 0.2*10^-9; % Sampling period

Fs = 1/T; % Sampling frequency

Fn = Fs/2; % Nyquist frequency

omega = 2*pi*200*10^6; % Carrier frequency

L = 32768; % % Length of signal

t = (0:L-1)*T; % Time vector

x_signal(n) = cos(omega*T*n + 0.1*randn(size(n))); % Additive phase noise (random)

y_signal(n) = sin(omega*T*n + 0.1*randn(size(n))); % Additive phase noise (random)

theta(n) = atan(y_signal(n)/x_signal(n));

f = (theta(n)-theta(n-1))/(2*pi)

Y = fft(f,t);

PSD = Y.*conj(Y); % Power Spectral Density

%Fv = linspace(0, 1, fix(L/2)+1)*Fn; % Frequency Vector

[Star Strider]

Calculate the phase from the fft using the angle function.

[Xuan Hiep Dinh]

Thanks for help. However, I need to calculate the phase "theta" before doing fft.

[Xuan Hiep Dinh]

And I am stuck when calculating the frequency.