One of the routes to chaos is by period doubling, which continues until there are no further stable state available. When driven at switching frequency, circuit exhibits periodic behavior. As the system parameter (input voltage) gets changed,
periodic state becomes unstable. The state divides into two frequencies, switching frequency remains as such but a second frequency appears at half the driving frequency. This is called the period doubling route to chaos. Further increase in
input voltage results in splitting of two periods, giving quadrupling, octupling and finally chaos. Power spectrum provides an easy way to identify a chaotic
system. The spectral analysis shows the power vs frequency for a given system. In periodic system, only one harmonic peak occurs, associated with driving frequency. As the system progressed towards chaos, more peaks will occur, associated
with harmonics and sub harmonics of the system. For a truly chaotic system, there should be a spectrum of frequencies rather than specific peaks. Similarly spectrum, one of the time frequency representation of the signal helps in studying
the frequency patterns such as sub harmonics of chaotic dynamics at particular instant of time.