N=3;
Damp=0.99;

y=zeros(1,1000);
y(1)=0.01;

a=ones(1,N);
a(2)=-1.8; % "частота"
b=N;

a=a.*(Damp.^[0:(N-1)]); % сдвиг полюсов


for (i=3:length(y)+1)
    y(i)=-a(2)*y(i-1)-a(3)*y(i-2);
    if(y(i)*y(i-1)<0)
        y(i)=y(i)+0.01*sign(y(i));
    end
end

figure (1)
plot (y)
grid on

clear all;

S=1;        % количество сигналов

N=2*S+1;

Per_1=[20 30];   % период сигнала в отсчётах (дробный допустим)

Damp=0.99;  % затухание
Push=(1-Damp);

y=zeros(1,10000);
y(1)=Push;

a1=ones(1,N);
a1(2)=-2*cos(2*pi/Per_1(1)); %

a=a1;

%------------

a=a.*(Damp.^[0:(N-1)]); % сдвиг полюсов

for (i=3:length(y)+1)
    y(i)=sum(-a(2:N).*y(i-(1:N-1)));
    if(y(i)*y(i-1)<0)
        y(i)=y(i)+Push*sign(y(i)); % "подкачка"
    end
end

figure (1)
plot (y(1:1000))
grid on

yw = blackmanharris(2048).*y(7001:9048)';
Y = fft(yw);
Ya= abs(Y(1:1024));
Ya=Ya/max(Ya);

figure(2)
semilogy(0:1023, Ya)
xlim ([0,1023])
ylim ([1e-4, 1])
grid on

clear all;

%%  TSerg  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

N = 2048;    % Длина последовательности
T = 4;        % Количество периодов в последовательности

% rate r = 0..1
% r = 0.005;
r = T / N * 2;

p = zeros(1, N);
for (i = 2 : N)
  p(i) = p(i - 1) + r;
  if (p(i) > 1)
    p(i) = p(i) - 2;
  end
  g = 4 .* p .* (1 - abs(p));    % амплитуда равна 4 * 0.25
end

figure(1)
plot(1 : N, g)
xlim([0, N])
grid on

wg = blackmanharris(N) .* g(1 : N)';
sp = fft(wg);
sp = abs(sp(1 : N));
sp = sp / max(sp);

figure(2)
semilogy(1 : N, sp)
xlim([0, N / 2])
ylim([1e-6, 1])
grid on

clear all;