chirp (Signal Processing Toolbox)

Swept-frequency cosine generator.

Syntax

y = chirp(t,f0,t1,f1)
y = chirp(t,f0,t1,f1,'method')
y = chirp(t,f0,t1,f1,'method',phi)

Description

y = chirp(t,f0,t1,f1)

generates samples of a linear swept-frequency cosine signal at the time instances defined in array t, where f0 is the instantaneous frequency at time 0, and f1 is the instantaneous frequency at time t1. f0 and f1 are both in Hertz. If unspecified, f0 is 0, t1 is 1, and f1 is 100.

y = chirp(t,f0,t1,f1,'method')

specifies alternative sweep method options, where method can be

linear, which specifies an instantaneous frequency sweep f_i(t) given by
where
ensures that the desired frequency breakpoint f₁ at time t₁ is maintained.
quadratic, which specifies an instantaneous frequency sweep f_i(t) given by
where
logarithmic specifies an instantaneous frequency sweep f_i(t) given by
where

For a log-sweep, f1 must be greater than f0.

y = chirp(t,f0,t1,f1,'method',phi)

allows an initial phase phi to be specified in degrees. If unspecified, phi is 0. Default values are substituted for empty or omitted trailing input arguments.

Examples

Compute the spectrogram of a chirp with linear instantaneous frequency deviation:

t = 0:0.001:2;              % 2 secs @ 1kHz sample rate
y = chirp(t,0,1,150);       % Start @ DC, cross 150Hz at t=1 sec
specgram(y,256,1e3,256,250) % Display the spectrogram

Compute the spectrogram of a chirp with quadratic instantaneous frequency deviation:

t = -2:0.001:2;                     % ±2 secs @ 1kHz sample rate
y = chirp(t,100,1,200,'quadratic'); % Start @ 100Hz, cross 200Hz
                                    % at t=1 sec
specgram(y,128,1e3,128,120)         % Display the spectrogram

See Also


`cos`	Cosine of vector/matrix elements (see the online MATLAB Function Reference).
`diric`	Dirichlet or periodic sinc function.
`gauspuls`	Gaussian-modulated sinusoidal pulse generator.
`pulstran`	Pulse train generator.
`rectpuls`	Sampled aperiodic rectangle generator.
`sawtooth`	Sawtooth or triangle wave generator.
`sin`	Sine of vector/matrix elements (see the online MATLAB Function Reference).
`sinc`	Sinc function.
`square`	Square wave generator.
`tripuls`	Sampled aperiodic triangle generator.

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