數(shù)字濾波器外文翻譯

1、<p><b>　　數(shù)字濾波器</b></p><p>　　數(shù)字濾波器是對數(shù)字信號進行濾波處理以得到期望的響應特性的離散時間系統(tǒng)。作為一種電子濾波器，數(shù)位濾波器與完全工作在模擬信號域的模擬濾波器不同。數(shù)字濾波器工作在數(shù)字信號域，它處理的對象是經(jīng)由采樣器件將模擬信號轉換而得到的數(shù)字信號。</p><p>　　數(shù)字濾波器的工作方式與模擬濾波器也完全不同：后者完全

2、依靠電阻、電容、晶體管等電子元件組成的物理網(wǎng)絡實現(xiàn)濾波功能；而前者是通過數(shù)字運算器件對輸入的數(shù)字信號進行運算和處理，從而實現(xiàn)設計要求的特性。</p><p>　　數(shù)字濾波器理論上可以實現(xiàn)任何可以用數(shù)學算法表示的濾波效果。數(shù)字濾波器的兩個主要限制條件是它們的速度和成本。數(shù)字濾波器不可能比濾波器內(nèi)部的計算機的運算速度更快。但是隨著集成電路成本的不斷降低，數(shù)字濾波器變得越來越常見并且已經(jīng)成為了如收音機、蜂窩電話、立體聲

3、接收機這樣的日常用品的重要組成部分。</p><p>　　數(shù)字濾波器一般由寄存器、延時器、加法器和乘法器等基本數(shù)字電路實現(xiàn)。隨著集成電路技術的發(fā)展，其性能不斷提高而成本卻不斷降低，數(shù)字濾波器的應用領域也因此越來越廣。按照數(shù)字濾波器的特性，它可以被分為線性與非線性、因果與非因果、無限脈沖響應（IIR）與有限脈沖響應（FIR）等等。其中，線性時不變的數(shù)字濾波器是最基本的類型；而由于數(shù)字系統(tǒng)可以對延時器加以利用，因此可

4、以引入一定程度的非因果性，獲得比傳統(tǒng)的因果濾波器更靈活強大的特性；相對于IIR濾波器，F(xiàn)IR濾波器有著易于實現(xiàn)和系統(tǒng)絕對穩(wěn)定的優(yōu)勢，因此得到廣泛的應用；對于時變系統(tǒng)濾波器的研究則導致了以卡爾曼濾波為代表的自適應濾波理論</p><p>　　數(shù)字濾波器具有比模擬濾波器更高的精度，甚至能夠?qū)崿F(xiàn)后者在理論上也無法達到的性能。例如，對于數(shù)字濾波器來說很容易就能夠做到一個 1000Hz 的低通濾波器允許 999Hz 信號通

5、過并且完全阻止 1001Hz 的信號，模擬濾波器無法區(qū)分如此接近的信號。</p><p>　　數(shù)字濾波器相比模擬濾波器有更高的信噪比。這主要是因為數(shù)字濾波器是以數(shù)字器件執(zhí)行運算，從而避免了模擬電路中噪聲（如電阻熱噪聲）的影響。數(shù)字濾波器中主要的噪聲源是在數(shù)字系統(tǒng)之前的模擬電路引入的電路噪聲以及在數(shù)字系統(tǒng)輸入端的模數(shù)轉換過程中產(chǎn)生的量化噪聲。這些噪聲在數(shù)字系統(tǒng)的運算中可能會被放大，因此在設計數(shù)字濾波器時需要采用合適

6、的結構，以降低輸入噪聲對系統(tǒng)性能的影響。</p><p>　　數(shù)字濾波器還具有模擬濾波器不能比擬的可靠性。組成模擬濾波器的電子元件的電路特性會隨著時間、溫度、電壓的變化而漂移，而數(shù)字電路就沒有這種問題。只要在數(shù)字電路的工作環(huán)境下，數(shù)字濾波器就能夠穩(wěn)定可靠的工作。</p><p>　　由于奈奎斯特采樣定理，數(shù)字濾波器的處理能力受到系統(tǒng)采樣頻率的限制。如果輸入信號的頻率分量包含超過濾波器1/2

7、采樣頻率的分量時，數(shù)字濾波器因為數(shù)字系統(tǒng)的“混疊”而不能正常工作。如果超出1/2采樣頻率的頻率分量不占主要地位，通常的解決辦法是在模數(shù)轉換電路之前放置一個低通濾波器（即抗混疊濾波器）將超過的高頻成分濾除。否則就必須用模擬濾波器實現(xiàn)要求的功能。</p><p>　　線性移不變的數(shù)字濾波器包括無限長脈沖響應濾波器（IIR濾波器）和有限長脈沖響應濾波器（FIR濾波器）兩種。這兩種濾波器的系統(tǒng)函數(shù)可以統(tǒng)一以Z變換表示為：

8、</p><p>　　當時，M就是IIR濾波器的階數(shù)，表示系統(tǒng)中反饋環(huán)的個數(shù)。由于反饋的存在，IIR濾波器的脈沖響應為無限長，因此得名。若A(z) = 1，則系統(tǒng)的脈沖響應的長度為N+1，故而被稱作FIR濾波器。</p><p>　　IIR濾波器的優(yōu)點在于，其設計可以直接利用模擬濾波器設計的成果，因為模擬濾波器本身就是無限長沖激響應的。通常IIR濾波器設計的過程如下：首先根據(jù)濾波器參數(shù)要求

9、設計對應的模擬濾波器（如巴特沃斯濾波器、切比雪夫濾波器等等），然后通過映射（如脈沖響應不變法、雙線性映射等等）將模擬濾波器變換為數(shù)字濾波器，從而決定IIR濾波器的參數(shù)。IIR濾波器的重大缺點在于，由于存在反饋其穩(wěn)定性不能得到保證。另外，反饋還使IIR濾波器的數(shù)字運算可能溢出。</p><p>　　FIR濾波器最重要的優(yōu)點就是由于不存在系統(tǒng)極點，F(xiàn)IR濾波器是絕對穩(wěn)定的系統(tǒng)。FIR濾波器還確保了線性相位，這在信號處

10、理中也非常重要。此外，由于不需要反饋，F(xiàn)IR濾波器的實現(xiàn)也比IIR濾波器簡單。FIR濾波器的缺點在于它的性能不如同樣階數(shù)的IIR濾波器，不過由于數(shù)字計算硬件的飛速發(fā)展，這一點已經(jīng)不成為問題。再加上引入計算機輔助設計，F(xiàn)IR濾波器的設計也得到極大的簡化。</p><p>　　Digital Filter</p><p>　　Digital filter is filtered to digi

11、tal signal processing to achieve the desired response characteristics of discrete-time system. As a kind of electronic filters, digital filter and all work in analog signals domain simulation filter is different. Digital

12、 filter work in digital signal domain, it handles objects through sampling device is analog signal conversion for digital signals. </p><p>　　Digital filter way of working and simulation filter also completel

13、y different: the latter depend entirely on the resistor, capacitor, transistor, and other electronic components of physical network realization filter function; While the former is through digital computing devices for t

14、he entry of digital signal calculations and processing, thus realize the requirement of design characteristics.</p><p>　　Digital filter theory can achieve any can use mathematical algorithm the filtering eff

15、ect said. Digital filter's two main constraints is their speed and cost. Digital filter impossible internal computer than filter the faster. But as the integrated circuit costs continue to reduce, digital filter is b

16、ecoming more and more common and has become such as radio, cell phones, stereo receivers such an important part of daily articles. </p><p>　　Digital filter generally by registers, delay device, on time-multi

17、plier adder and basic digital circuit implementation. Along with the development of the integrated circuit technology, its with improving performance and cost is lower, digital filter application fields and therefore mor

18、e and more widely. According to the characteristics of digital filter, it can be divided into linear and nonlinear, causal and the causal, infinite impulse response (IIR) and finite impulse response (FIR), etc. Amo</p

19、><p>　　Digital filters with higher precision than analog filter, even can realize the latter in theory cannot achieve performance. For example, it is very easy for digital filter is able to do a 1000Hz allowed

20、the low-pass filter and completely prevent 999Hz signal through 1001Hz signal, the simulation filter can't distinguish so close to signal. </p><p>　　Digital filters with a higher than analog filter SNR.

21、This is mainly because digital filter based on digital devices perform operation so as to avoid the analog circuits noise (such as resistors thermal noise) influence. Digital filters the main noise source is in digital s

22、ystem introduced before the analog circuit noise and in digital system input to produce analog-to-digital conversion of quantization noise. These noise in digital system in the operations of may be amplified, so in desig

23、n digi</p><p>　　Digital filter also has not reliability simulation filter. Of analog filter circuits characteristic of electronic components with time, temperature, voltage change and drift, and digital circ

24、uit is no such problem. As long as the work environment in a digital circuit, digital filters can stable and reliable work. </p><p>　　Because Nyquist sampling theorem Nyquist sampling theorem (en: the proces

25、sing, digital filters) sampling frequency by system of ability to limit. If the input signal frequency component contains more than filter 1/2 sampling frequency component, digital filters for digital systems "alias

26、ing" and can't work normally. If exceed 1/2 sampling frequency frequency weight not predominant, usually solution is placed in frequency-field circuit before one low-pass filter (namely fight aliasing filter) wi

27、l</p><p>　　At the time, M is the order number IIR filter, said the number of feedback loops in the system. Due to the existence of IIR filter, feedback the impulse response to an infinite long, therefore the

28、 name. If A (z) = 1, it is the length of the impulse response system for N + 1, so called FIR filter. </p><p>　　Linear moving constant digital filter, including an infinite long impulse response filter (IIR

29、filter) and limited long impulse response filter (FIR filter) two kinds. These two kinds of filter system function can be unified with Z transformation expressed as: </p><p>　　The advantages of IIR filter is

30、 that its design can directly using simulation filter design results, because analog filter itself is an infinite long impulse response. Usually IIR filter design process are as follows: first of all, according to the re

31、quirements of the design parameters of the corresponding filters simulated filter (such as bart hepworth filter, chebyshev filters, etc), and then by mapping (such as pulse response don't strain and bilinear map, etc

32、.) will transform into digital fi</p><p>　　FIR filter is the most important advantages, because they do not exist system poles, FIR filters is absolutely stable system. FIR filter also ensures that the linea

33、r phase in signal processing, this also is very important. In addition, because do not need feedback, the realization of FIR filters than IIR filter simple. FIR filter's weakness is its performance as the same order