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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/11252

Title: 多頻帶訊號完整帶通取樣條件之進階研究
Advanced Research on the Complete Bandpass Sampling Requirements for Multiband Signals
Authors: 曾敬翔
Contributors: NTOU:Department of Electrical Engineering
國立臺灣海洋大學:電機工程學系
Keywords: ?頻;帶通取樣;非線性系統;頻譜;軟體無線電;多頻帶訊號
Aliasing;bandpass sampling;nonlinear system;spectrum;software defined radios;multiband signal
Date: 2009-08
Issue Date: 2011-06-28T08:08:48Z
Abstract: 摘要:在這個兩年計畫裏,我們提出了多頻帶訊號完整帶通取樣條件之進階研究。在第一年,我們會將焦點放在由非線性系統產生之特殊多頻帶訊號。由帶通輸入訊號所驅動之非線性系統可能產生佔據多個頻帶之輸出訊號。這使得針對非線性系統的輸出訊號取樣而不導致贋頻成為一個具挑戰性的任務。雖然線性系統之帶通取樣理論已經發展完備,但在非線性系統的帶通取樣理論上卻仍相對不成熟。具體而言,完整之非線系統的帶通取樣條件只發展到上至三階的非線性系統。在本計畫中,我們提出了一個創新的方法來推導任意階非線性系統的完整帶通取樣條件。這個方法所使用的策略是將n階非線性系統的取樣頻率限制建構在(n-1)階非線性系統之取樣頻率限制上。這個程序使提出的推導方法得以輕易延伸至任意階之非線性系統。這個推導方法也讓我們得以洞悉將帶通取樣頻率之限制公式化的途徑。基於在推導過程中得到的一些領悟,我們期望可以推導出任意階非線性系統完整帶通取樣條件之通用公式。這個計畫的成功將使得非線性系統的帶通取樣理論更加鞏固,也將使選擇非線性系統的帶通取樣頻率更為便利。我們也將展示所推導出的通用公式在處理以類比至數位轉換器轉換帶通訊號時所產生之非線性問題上的應用。 在第二年,我們將考慮由多個不同射頻訊號組成之多頻帶訊號的帶通取樣。使用帶通取樣來直接降轉換多個不同射頻訊號在近年來引起了許多的迴響。這個方法所面臨的基本問題就是要選擇適用於這些多組射頻訊號的帶通取樣頻率。目前用來決定適用之帶通取樣頻率範圍的方法若非不完整就是需要大量運算。在本計畫中,我們提出了尋找直接降轉換多個射頻訊號之合宜完整帶通取樣頻率範圍的有效率演算法。所提出的演算法在計算複雜度上優於傳統方法之處將被驗證。此外,我們也將推導多個射頻訊號完整帶通取樣條件之通用公式。所獲得的成果將使軟體無線電多頻帶接收機的設計更為便利。
abstract:In this two-year project, we propose an advanced research on the complete bandpass sampling requirements for multiband signals. In the first year, we will focus on the special kind of multiband signals that are produced by nonlinear systems. A nonlinear system driven by a bandpass input signal may produce an output signal that occupies multiple frequency bands. This makes bandpass sampling the output signal of the nonlinear system without causing aliasing a challenging task. Although the bandpass sampling theory for linear systems is well developed, its counterpart for nonlinear systems is relatively immature in the sense that complete bandpass sampling requirements have only been developed up to third-order nonlinear systems. In this project, a novel method is proposed to derived the complete bandpass sampling requirements for nonlinear systems of an arbitrary order. The strategy used by this method is to build the constraints on the sampling frequency for n-th order nonlinear systems upon those for (n-1)-th order nonlinear systems. This process makes the derivation easily extendable to nonlinear systems of any order. The derivation method also gives an insight into the mechanism for formularizing the constraints on the bandpass sampling frequency. Based on this insight, a universal formula for the complete bandpass sampling requirements for nonlinear systems of any order is expected to be derived. The success of this project will consolidate the bandpass sampling theory for nonlinear systems and facilitate the selection of the bandpass sampling frequency for nonlinear systems driven by bandpass input signals. Application of the derived universal formula to deal with the nonlinearities in converting bandpass signals using an analog-to-digital converter (ADC) will also be demonstrated. In the second year, we will consider bandpass sampling multiband signals obtained from summing up multiple distinct radio frequency (RF) signals. Direct downconversion of multiple distinct RF signals using bandpass sampling has received much attention in recent years. An essential problem in this approach is to select a valid bandpass sampling frequency for the multiple RF signals. Currently available methods for determining the valid bandpass sampling frequency ranges are either incomplete or computationally demanding. In this project, we propose an efficient algorithm to find the complete ranges of valid bandpass sampling frequency for direct downconverting multiple RF signals. The computational advantage of the proposed algorithm over conventional methods will be justified. Furthermore, derivation of a universal formula for the complete bandpass sampling requirements for multiple RF signals will also be considered. The result can facilitate the design of multiband receivers for software defined radios.
Relation: NSC98-2221-E019-015
URI: http://ntour.ntou.edu.tw/ir/handle/987654321/11252
Appears in Collections:[Department of Electrical Engineering] Research Reports

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