# Spektrá

## Spektrá

``` % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %
%                                                             %
% Takto sa kresli spektrum signalu typu Sinus s f 440 Hz.     %
%                                                             %
% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %

f_sample = 8000;               % [Hz] - pre telefony OK
duration =    1;               % [s]  - jedna sekunda
freq =  440;               % [Hz] - komorne A4 = 440 Hz
A =  0.9;               % [V]  - amplituda signalu z <-1,1>

time = 0 : (1/f_sample) : duration;
SinusSignal = A * sin( 2*pi*freq*time + 0 );

T_sample = 1/f_sample;
N = length(SinusSignal);

maxtime = (N-1) * T_sample;      % Doba trvania signalu

time = (0:N-1) * T_sample;       % Casova osa
freq = (0:N-1) / maxtime;        % Kmitoctova osa

% Fourierova analyza:

S = fft(SinusSignal);             % Vypocet komplexneho spektra
Mod = 2/N * abs(S);               % Spravne amplitudove spektrum
Pha = 180/pi * angle(S);          % Fazove spektrum v stupnoch

N1 = round(N/2);                  % Kreslime len relevantu cast po f_sample/2

subplot(2,1,1);
plot(freq(1:N1),Mod(1:N1));       % Aplitudova frekvencna charakteristika

subplot(2,1,2);
plot(freq(1:N1),Pha(1:N1));       % Fazova frekvencna charakteristika
```