鎖相迴路應用於腦電波之瞬間偵測頻率（二）

Abstract

在這篇論文中，我們主要是在探討經由鎖相迴路（ＰＬＬ）來偵測腦 電波訊號之瞬間頻率的可行性。ＰＬＬ已經成功的應用在弦波訊號上的單 一高頻（在某個瞬間）之時變頻率追蹤。 然而，ＥＥＧ本身是一個低頻 且多頻率成分的訊號，為了順應ＰＬＬ追蹤時變ＥＥＧ頻率之特性，我們 藉由單邊旁頻帶修正（ＳＳＢ）應用在ＥＥＧ的方式將ＥＥＧ頻譜調變至 更高的頻帶。 ＰＬＬ在低頻與高頻情形下的表現，經由電腦模擬與硬體 設計兩種方式去研究與比較，其結果顯示經由ＰＬＬ硬體設計的頻率偵測 ，可以得到與電腦模擬一致的結果。因此，本研究顯示出ＰＬＬ的修正能 夠偵測出ＥＥＧ其隨時間變化的頻率。 In this thesis, we investigate the feasibility of the phase- locked-loop (PLL) circuit in detection of the instantaneous frequency of EEG (electroencephalograph) signals. The PLL has been successfully applied to the high-frequency and signal- component (at a given time instant) sinusoidal signals for the time-varying frequency tracking. However, the EEG is a low- frequency and multi-component signals. To adapt the PLL for tracking the time-varying frequency of EEG, we move the EEG frequency spectrum to a much higher frequency region by applying the single-sideband-modulation (SSB) to EEG. The performance of PLL in the low-frequency and high-frequency cases are studied and compared by the computer simulation and hardware implementation. Results of frequency detection via the hardware implementation of PLL are shown to be in agreement with which of computer simulation. The study shows that a modification of the PLL enables the detection of the time-varying frequency of EEG.