vco
Voltage controlled oscillator
Syntax
y = vco(x,fc,fs)
y = vco(x,[Fmin Fmax],fs)
Description
y = vco(x,fc,fs) creates
a signal that oscillates at a frequency determined by the real input
vector or array x with sampling frequency fs. fc is
the carrier or reference frequency; when x is 0, y is an fc Hz cosine with amplitude 1 sampled at fs Hz. 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.
Output y is the same size as x.
y = vco(x,[Fmin Fmax],fs) scales the frequency modulation range
so that ±1 values of x yield oscillations
of Fmin Hz and Fmax Hz respectively. For best results, Fmin and Fmax should
be in the range 0 to fs/2.
By default, fs is 1 and fc is fs/4.
If x is a matrix, vco produces
a matrix whose columns oscillate according to the columns of x.
Examples
Spectrogram of Sawtooth Signal
Generate two seconds of a signal sampled at 10 kHz whose instantaneous frequency is a triangle function of time.
fs = 10000; t = 0:1/fs:2; x = vco(sawtooth(2*pi*t,0.75),[0.1 0.4]*fs,fs);
Plot the spectrogram of the generated signal.
spectrogram(x,kaiser(256,5),220,512,fs,'yaxis')
Diagnostics
If any values of x lie outside [–1, 1], vco gives the following error message:
X outside of range [-1,1].
Algorithms
vco performs FM modulation using the modulate function.