y = vco(x,fc,fs)
creates a signal that oscillates at a frequency determined by the real input vector or
matrix x with sampling frequency fs. If
x is a matrix, vco produces a matrix whose columns
oscillate according to the columns of x.

Generate two seconds of a signal composed of a voltage-controlled oscillator (vco) and four Gaussian atoms. The instantaneous frequency is modulated by a chirp function. The sample rate is 14 kHz.

fs = 14000;
t = (0:1/fs:2)';
gaussFun = @(A,x,mu,f) exp(-(x-mu).^2/(2*0.01^2)).*sin(2*pi*f.*x)*A';
s = gaussFun([1 1 1 1],t,[0.2 0.5 1 1.75],[10 60 25 5]*100)/10;
x = vco(chirp(t+.1,0,t(end),3).*exp(-2*(t-1).^2),0.2*fs,fs);
s = s/10+x;

Plot the spectrogram of the generated signal. Specify 90% overlap and moderate spectral leakage.

Input data, specified as a real vector or real matrix. x ranges
from –1 to 1, where x =
–1 corresponds to 0 frequency output, x =
0 corresponds to fc, and
x = 1 corresponds to
2*fc.

fc — Carrier frequency fs/4 (default) | real positive scalar

Carrier or reference frequency used to modulate the input signal, specified as a
real positive scalar.

Fmin, Fmax — Frequency modulation range limits real vector

Frequency modulation range limits, specified as a real vector. For best results,
Fmin and Fmax should be in the range 0 to
fs/2.

Note

vco performs FM modulation using the modulate function.

fs — Sample rate positive scalar

Sample rate, specified as a positive scalar. The sample rate
is the number of samples per unit time. If the unit of time is seconds,
then the sample rate has units of Hz.

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