【摘要】：微弱信號是指幅值比較小的有用信號,通常這類信號容易被強噪聲所淹沒。傳統(tǒng)的微弱信號檢測方法主要是基于濾除和抑制噪聲,比如窄帶濾波、小波分析、取樣積分、相關(guān)檢測等,這些方法檢測信噪比門限都比較高且會在一定程度上對有用信號造成損害。因此本論文利用Duffing振子系統(tǒng)對微弱周期信號敏感和對任意零均值噪聲免疫的特性,實現(xiàn)低信噪比下對微弱周期信號的有效檢測。本論文首先分析了 Duffing振子系統(tǒng)的動力學(xué)特性以及噪聲對其系統(tǒng)狀態(tài)的影響,其次分析了系統(tǒng)閾值的判別方法,基于時域及相軌跡方法確定系統(tǒng)閾值并根據(jù)Lyapunov指數(shù)計算出系統(tǒng)的精確閾值。然后針對目前檢測方法所存在的不足進行改進,基于變步長Duffing振子檢測系統(tǒng),通過設(shè)定一組能夠覆蓋待測信號所在頻段的仿真步長序列,實現(xiàn)了對低信噪比微弱信號頻率的搜索檢測;通過相軌跡觀察法,實現(xiàn)了對待測信號幅值的檢測;通過研究系統(tǒng)在大尺度周期狀態(tài)時最大Lyapunov指數(shù)與待測信號總的策動力幅值的關(guān)系,再結(jié)合策動力幅值與相位之間的關(guān)系,完成了對待測信號初始相位的有效檢測。最終完成了對待測信號頻率、幅值、相位的參數(shù)估計,并利用matlab分別對上述方法進行了仿真實驗,驗證了方法的有效性及準(zhǔn)確性。
[Abstract]:Weak signal is a useful signal with small amplitude, which is usually easily submerged by strong noise. Traditional weak signal detection methods are mainly based on filtering and suppressing noise, such as narrowband filtering, wavelet analysis, sampling integration, correlation detection, etc. These methods have high signal-to-noise ratio (SNR) detection threshold and damage useful signals to some extent. Therefore, the Duffing oscillator system is sensitive to the weak periodic signal and immune to any zero mean noise, so that the weak periodic signal can be detected effectively at low signal-to-noise ratio (SNR). In this paper, firstly, the dynamic characteristics of Duffing oscillator system and the influence of noise on the system state are analyzed. Secondly, the method of judging the threshold value of the system is analyzed. The system threshold is determined based on time domain and phase locus method, and the precise threshold is calculated according to Lyapunov exponent. Based on the variable step size Duffing oscillator detection system, a set of simulation step sequences which can cover the frequency band of the signal to be tested are set. The low signal-to-noise ratio (SNR) weak signal frequency search and detection is realized. The amplitude of the measured signal is detected by the method of phase trajectory observation. By studying the relationship between the maximum Lyapunov exponent of the system and the amplitude of the total driving force of the signal to be measured, and combining the relationship between the amplitude of the excitation force and the phase, the effective detection of the initial phase of the measured signal is accomplished. Finally, the parameter estimation of the frequency, amplitude and phase of the measured signal is completed, and the simulation experiments are carried out using matlab to verify the validity and accuracy of the method.
【學(xué)位授予單位】：山東科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN911.23

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