chirp (Signal Processing Toolbox)

Generate a swept-frequency cosine.

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

Example 1

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

Example 2

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
Compute the cosine of vector/matrix elements (see the MATLAB documentation).

diric
Compute the Dirichlet or periodic sinc function.

gauspuls
Generate a Gaussian-modulated sinusoidal pulse.

pulstran
Generate a pulse train.

rectpuls
Generate a sampled aperiodic rectangle.

sawtooth
Generate a sawtooth or triangle wave.

sin
Compute the sine of vector/matrix elements (see the MATLAB documentation).

sinc
Compute the sinc function.

square
Generate a square wave.

tripuls
Generate a sampled aperiodic triangle.

`cos`	Compute the cosine of vector/matrix elements (see the MATLAB documentation).
`diric`	Compute the Dirichlet or periodic sinc function.
`gauspuls`	Generate a Gaussian-modulated sinusoidal pulse.
`pulstran`	Generate a pulse train.
`rectpuls`	Generate a sampled aperiodic rectangle.
`sawtooth`	Generate a sawtooth or triangle wave.
`sin`	Compute the sine of vector/matrix elements (see the MATLAB documentation).
`sinc`	Compute the sinc function.
`square`	Generate a square wave.
`tripuls`	Generate a sampled aperiodic triangle.

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