y = chirp(t,f0,t1,f1)
generates samples of a linear swept-frequency cosine signal at the time
instances defined in array t. The instantaneous frequency
at time 0 is f0 and the instantaneous frequency at time
t1 is f1.

Generate a chirp with linear instantaneous frequency deviation. The chirp is sampled at 1 kHz for 2 seconds. The instantaneous frequency is 0 at t = 0 and crosses 250 Hz at t = 1 second.

t = 0:1/1e3:2;
y = chirp(t,0,1,250);

Compute and plot the spectrogram of the chirp. Divide the signal into segments such that the time resolution is 0.1 second. Specify 99% of overlap between adjoining segments and a spectral leakage of 0.85.

Generate a chirp with quadratic instantaneous frequency deviation. The chirp is sampled at 1 kHz for 2 seconds. The instantaneous frequency is 100 Hz at t = 0 and crosses 200 Hz at t = 1 second.

t = 0:1/1e3:2;
y = chirp(t,100,1,200,'quadratic');

Compute and plot the spectrogram of the chirp. Divide the signal into segments such that the time resolution is 0.1 second. Specify 99% of overlap between adjoining segments and a spectral leakage of 0.85.

Generate a convex quadratic chirp sampled at 1 kHz for 2 seconds. The instantaneous frequency is 400 Hz at t = 0 and crosses 300 Hz at t = 1 second.

t = 0:1/1e3:2;
fo = 400;
f1 = 300;
y = chirp(t,fo,1,f1,'quadratic',[],'convex');

Compute and plot the spectrogram of the chirp. Divide the signal into segments such that the time resolution is 0.1 second. Specify 99% of overlap between adjoining segments and a spectral leakage of 0.85.

Generate a concave quadratic chirp sampled at 1 kHz for 4 seconds. Specify the time vector so that the instantaneous frequency is symmetric about the halfway point of the sampling interval, with a minimum frequency of 100 Hz and a maximum frequency of 500 Hz.

t = -2:1/1e3:2;
fo = 100;
f1 = 200;
y = chirp(t,fo,1,f1,'quadratic',[],'concave');

Compute and plot the spectrogram of the chirp. Divide the signal into segments such that the time resolution is 0.1 second. Specify 99% of overlap between adjoining segments and a spectral leakage of 0.85.

Generate a logarithmic chirp sampled at 1 kHz for 10 seconds. The instantaneous frequency is 10 Hz initially and 400 Hz at the end.

t = 0:1/1e3:10;
fo = 10;
f1 = 400;
y = chirp(t,fo,10,f1,'logarithmic');

Compute and plot the spectrogram of the chirp. Divide the signal into segments such that the time resolution is 0.2 second. Specify 99% of overlap between adjoining segments and a spectral leakage of 0.85.

Generate a complex linear chirp sampled at 1 kHz for 10 seconds. The instantaneous frequency is –200 Hz initially and 300 Hz at the end. The initial phase is zero.

t = 0:1/1e3:10;
fo = -200;
f1 = 300;
y = chirp(t,fo,t(end),f1,'linear',0,'complex');

Compute and plot the spectrogram of the chirp. Divide the signal into segments such that the time resolution is 0.2 second. Specify 99% of overlap between adjoining segments and a spectral leakage of 0.85.

Sweep method, specified as 'linear',
'quadratic', or 'logarithmic'.

'linear' — Specifies an instantaneous
frequency sweep
f_{i}(t)
given by

$${f}_{i}(t)={f}_{0}+\beta t,$$

where

$$\beta =({f}_{1}-{f}_{0})/{t}_{1}$$

and the default value for
f_{0} is 0. The
coefficient β ensures that the desired
frequency breakpoint
f_{1} at time
t_{1} is
maintained.

'quadratic' — Specifies an instantaneous
frequency sweep
f_{i}(t)
given by

$${f}_{i}(t)={f}_{0}+\beta {t}^{2},$$

where

$$\beta =({f}_{1}-{f}_{0})/{t}_{1}{}^{2}$$

and the default value for
f_{0} is 0. If
f_{0} > f_{1}
(downsweep), the default shape is convex. If
f_{0 }< f_{1}
(upsweep), the default shape is concave.

'logarithmic' — Specifies an instantaneous
frequency sweep
f_{i}(t)
given by

Initial phase, specified as a positive scalar expressed in degrees.

Data Types: single | double

shape — Spectrogram shape of quadratic chirp 'convex' | 'concave'

Spectrogram shape of quadratic chirp, specified as
'convex' or 'concave'.
shape describes the shape of the parabola with
respect to the positive frequency axis. If not specified,
shape is 'convex' for the
downsweep case with f_{0} >
f_{1}, and
'concave' for the upsweep case with
f_{0} <
f_{1}.

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