Chirps

Chirps are functions of the form , i.e., the frequence f(t) changes with time. There are two demos that try to illuminate the properties of wavelets and wavelet packets by analyzing chirps:

• chrpdemo: (see figure 11) this demo provides several choices for the signal (see help chrpdemo for more details about the signals) and provides two plots: amplitude against time and frequence against time (with amplitude shown with different shades of gray). See also help chrpdemo for more information.
• chrpcomp: (see figure 12) FFT, wavelets, and wavelet packets are used to analyze two signals, a cubic chirp and the superposition of a linear and a cubic chirp from chrpdemo. Wavelet packets can best find the properties of both signals, wavelets work reasonably for the simpler signal, but FFT does not give any reasonable sense out of either one.

  

Figure 11: chrpdemo

  

Figure 12: chrpcomp