標題: 週期性濾波器及其在語音攪拌上的應用
Periodic Filters and Their Applications to Speech Scrambling
作者: 金傳文
Chwan-Wen King
林清安
Ching-An Lin
電子研究所
關鍵字: 週期性系統;語音攪拌;週期性實線;periodic system;speech scrambling;periodic realization
公開日期: 1994
摘要: 本論文對週期性系統作一完整系列的探討。首先,逐一介紹週期性系統在 時域及頻率域下的非時變模式,因此許多在週期性系統上的分析設計的問 題,都可依非時變的技巧來解決。在這套理論背景下,我們輕易地找出週 期性濾波器的逆轉濾波器或者其最佳的近似解。利用此模式及其在頻率域 下的特性,我們建立一套分析設計類比語音攪拌器的方法。從模式建立, 系統分析到推演出不需框同步的充分必要條件等均作了一番詳盡的介紹及 探討。另外,我們由此條件,設計出一種圖解設計技巧,可讓吾人輕易而 有相當彈性地設計不需框同步的語音攪拌器。然而這種方式所得到的週期 性系統,仍然是以非時變的型式存在的,在實際運用時仍需回復成週期時 變的形態來實現。因此最後我們解決了非時變型式下的週期性系統最少實 現的問題,讓這套理論得以完整。本論文在學術及實際運用上的貢獻,可 歸納如下:(1)提供了週期性濾波器可逆的充分必要條件及計算逆轉濾 波器的公式,另外若濾波器不可逆,則提供一個最佳近似解的計算方法。 (2)提出一個類比語音攪拌系統的解析模型,及評量語音攪拌系統優劣 的評估法則。(3)推導出攪拌系統不需框同步的充分必要條件。(4) 提出一套不需框同步的攪拌系統的設計通則。(5)發展出一套計算程序 以求得週期性系統的最少狀態變數實現,並可移走系統中多餘的狀態變數 。這套程序可建立在計算機中。 In this dissertation, we give a series of investigations on the periodic systems. First of all, we introduce the time- invariant model of periodic systems both in time and frequency domains. Based on the model asserted here, we easily obtain the inverse or the optimal approximate inverse of a periodic filter. And then we propose a framework, based on transfer matrix and frequency domain descriptions of periodic systems, for analysis and design of speech scrambling filters. Finally, we solve the problem of realizing an N-blocked proper rational transfer matrix as an N-periodic system and hence complete the unified time- invariant model for periodic systems. The main contributions of this dissertation can be summarized as follows: (1) We give conditions for a periodic filter to be invertible and a simple formula to compute its inverse. (2) We give a generic model and evaluation criteria for analyzing speech scrambling systems. (3) We derive conditions for a scrambling system to be insensitive to frame synchronization error. (4) We propose a procedure for the design of scrambling filter that is insensitive to synchroniza- tion error. (5) We propose an algorithm to obtain periodic reali- zations which have a minimal number of states.
URI: http://140.113.39.130/cdrfb3/record/nctu/#NT830430007
http://hdl.handle.net/11536/59189
Appears in Collections:Thesis