Detection of Weak Simple Harmonic Signal in Strong Noise Based by Use of Chaotic Oscillator

Duffing oscillator's response to external simple harmonic excitation was studied by using numerical analysis method. With the increasing of amplitude of the simple harmonic excitation, the behavior of the system changed qualitatively in some critical values of the amplitude, such as from periodic oscillation to chaos. When the excitation was polluted by noises or other harmonic signals whose frequencies were higher or lower enough than the excitation's frequency, the critical values changed little. The oscillator could be applied to detect weak simple harmonic signal in the strong noise based on this character. Since primary phase of the simple harmonic component to be detected in the sampled signal was unknown, the method which ignored primary phase didn't work any longer when primary phase was concerned. Phase delay method was introduced to solve the problem. Numerical simulation indicated that simple harmonic signal with Gauss noise could be detected when SNR was bigger than -90dB.