鎖相迴路應用於腦電波瞬間頻率偵測(三)

Abstract

本篇論文，主要探討鎖相迴路對於非單一頻率輸入腦電波訊號的工作效能。鎖相迴路廣泛的用於通訊領域當中，而鎖相迴路的硬體架構也已發展成熟;本研究的目的在於能利用鎖相迴路快速追蹤頻率變化的特性，來達到偵測腦電波訊號瞬間頻率的變化趨勢。但鎖相迴路適用於處理單一高頻訊號的分析上，而腦電波訊號是一個低頻且多頻率組成的訊號，而這個特性的訊號會降低鎖相迴路進行頻率追蹤的效能。因此，本研究的重點在於探討如何提升鎖相迴路的追蹤效能，以及鎖相迴路在多頻率訊號輸入下的特性分析。 在研究的過程中，首先是對各種會降低鎖相迴路工作效能的因素進行分析，然後就其特性去作鎖相迴路上結構上的改良與設計，並以實際的腦電位訊號來作測試。

This thesis aims to investigate the performance of phase-locked-loop (PLL) circuitry on analyzing the signal with multiple frequency components (the electroencephalograph, EEG). PLL is widely used in the communication area. The PLL hardware system has been well developed. The main purpose of this research is to track the trend of variation of the instantaneous frequency in EEG. Note that the PLL works well for the high-frequency signal with a single frequency component at any time instant. The EEG is a low-frequency signal possessing multi-frequency components. This frequency characteristic affects the PLL performance. Accordingly, we investigate the ways to improve the PLL efficacy and the PLL output characteristics given that the input is composed of multiple frequency components. In this research study, we first investigated the factors causing decline of the PLL performance. Then we developed a modified PLL system for solving the problems. Finally, the modified PLL system is applied to the EEG frequency tracking.