Contents I. Introduction
Weak signal detection is a challenging task in signal detection field. Due to the low amplitude of the weak signal, weak signal detection is subject to the imperfect of the transducer and the noise caused by measuring devices, so the available measured signal is overwhelmed by many strong signals. In recent years, the chaotic oscillator has been proposed and investigated for detecting weak signal. In 1992, Donald L Birx found that the chaotic phase trajectory is sensitive to the weak signal but immune to the noise signal [1]. Wang used this phenomenon to detect weak sinusoidal signal in the presence of the strong noise, and obtained measured result (amplitude, frequency) with low signal-to-noise ratio (SNR) and proved the validity of this method [2]. Nie Chunyan used the detection method which combines cross-correlation and chaotic theory to get lower SNR threshold [3]. Li Yue used the modified Duffing equation to implement simulations of nV level signal detection. Ref. [5] suggests the Melnikov method to be used for the threshold value of oscillator, but the precision of the threshold value is limited and does not meet the requirement of the weak signal detection. In addition, as for present methods of weak signal detection based on chaotic oscillator, the judgment of chaotic dynamics, after the signal to be detected is incorporated to the oscillator, depends on human observation of the phase graph. Thus the efficiency is low.
