write pll in matlab

main.m
% Specify PLL parameters
N = 1000; % number of samples
t = (0:N-1); % time vector
f0 = 1; % input signal frequency
fs = 10*f0; % sampling frequency
A = 1; % input signal amplitude
phi_err = pi/4; % phase error

% Generate input signal
x = A * cos(2*pi*f0/fs*t);

% Add phase error
x_err = A * cos(2*pi*(f0/fs + phi_err/2)*t);

% Phase detector
y = x_err .* x;

% Loop filter
Kp = 1; % Proportional gain
Ki = 0.1; % Integral gain
E = zeros(1,N);
for n = 2:N
    E(n) = E(n-1) + Kp*y(n) + Ki*sum(y(1:n));
end

% VCO
f_vco = f0 + E;
theta = cumsum(2*pi*f_vco/fs);

% Output signal
y = A * cos(theta);

% Plot input and output signals
figure;
plot(t,x,'b',t,y,'r');
xlabel('Time');
ylabel('Amplitude');
legend('Input Signal', 'Output Signal');
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