signal (version 0.5)

chirp: A chirp signal

Description

Generate a chirp signal. A chirp signal is a frequency swept cosine wave.

Usage

chirp(t, f0 = 0, t1 = 1, f1 = 100, form = c("linear", "quadratic", "logarithmic"), phase = 0)

Arguments

t

array of times at which to evaluate the chirp signal.

f0

frequency at time t=0.

t1

time, s.

f1

frequency at time t=t1.

form

shape of frequency sweep, one of "linear", "quadratic", or "logarithmic".

phase

phase shift at t=0.

Value

• Chirp signal, an array the same length as t.

Details

'linear' is: $$f(t) = (f1-f0)*(t/t1) + f0$$ 'quadratic' is: $$f(t) = (f1-f0)*{t/t1}^2 + f0$$ 'logarithmic' is: $$f(t) = (f1-f0)^{t/t1} + f0$$

References

Octave Forge http://octave.sf.net

See Also

specgram

Examples

ch = chirp(seq(0, .6, len=5000))
plot(ch, type = "l")

# Shows a quadratic chirp of 400 Hz at t=0 and 100 Hz at t=10
# Time goes from -2 to 15 seconds.
specgram(chirp(seq(-2, 15, by=.001), 400, 10, 100, "quadratic"))

# Shows a logarithmic chirp of 200 Hz at t=0 and 500 Hz at t=2
# Time goes from 0 to 5 seconds at 8000 Hz.
specgram(chirp(seq(0, 5, by=1/8000), 200, 2, 500, "logarithmic"))