&ccedil;&not;&not;02&ccedil;&laquo;&nbsp; &ccedil;&brvbar;&raquo;&aelig;•&pound;&aelig;—&para;&eacu

# ç¬¬02ç«  ç¦»æ•£æ—¶&eacu

This preview shows pages 1–9. Sign up to view the full content.

2.3 frequency-domain representation of discrete-time signal and system 2.3.1 definition of Fourier transform 2.3.2 frequency response of system 2.3.3 properties of Fourier transform

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Hz f Hz f t t t x 200 , 100 ), 200 2 cos( 5 . 0 ) 100 2 cos( ) ( 2 1 = = + = π 0 0.01 0.02 -1 0 1 2 0 100 200 300 400 500 0 5 10 EXAMPLE 信号的频域表示 的直观意义 时域表示 频域表示

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
EXAMPLE 频域分析应用于对图像信号的带阻去噪
2.3.1 definition of Fourier transform （离散时间傅立叶变换） Many sequences can be represented by a Fourier integral of the form ω π d e e X n x n j j = ) ( 2 1 ] [ inverse Fourier transform () +∞ −∞ = = n n j j e n x e X ] [ where Fourier transform 0 | ] [ = +∞ −∞ = = j n e X n x 0 | ] [ 2 ) ( = = n j n x d e X 证明正变换的结果能通过反变换合成原始信号见课堂笔记

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
) () |() | j jj j X e RI Xe X e jX e e ω ωω =+ = ( ( ) magnitude e X j |, | , j X e phase ( ( ) [ ] phase value principal e X ARG j : π < < ( ) [ ] phase continuous e X j , arg In general, the Fourier transform is a complex-valued function of . ( ) j n j j e X e n x e X +∞ + + = = ) 2 ( ) 2 ( ] [ Periodicity
subplot(2,2,1); fplot ('real(1/(1-0.2*exp(-1*j*w)))',[-2*pi,2*pi]); title(' 实部 ') subplot(2,2,2); fplot('imag(1/(1-0.2*exp(-1*j*w)))',[-2*pi ,2*pi]); title(' 虚部 ') subplot(2,2,3); fplot('abs(1/(1-0.2*exp(-1*j*w)))',[-2*pi,2*pi]); title(' 幅度 ') subplot(2,2,4); fplot('angle(1/(1-0.2*exp(-1*j*w)))',[-2*pi,2*pi]); title(' 相位 ') ω j j n e e X n u n x = = 2 . 0 1 1 ) ( ], [ 2 . 0 ] [ -5 0 5 0.5 1 1.5 实部 -5 0 5 -0.5 0 虚部 -5 0 5 1 幅度 -5 0 5 0 相位 EXAMPLE 从时域理解为什 么有周期性？ MATLAB 画信号频谱

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
< < −∞ = n n n n x c , ) sin( ] [ π ω > = c c j e X | | , 0 | | , 1 ) ( EXAMPLE ( ) n n d e e X IFT c n j j c c ) sin( 2 1 ] [ = = Sufficient condition for existence of Fourier transform absolutely summable （绝对可和） .
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 02/29/2012 for the course EE 325 taught by Professor Lilili during the Fall '11 term at BYU.

### Page1 / 28

ç¬¬02ç«  ç¦»æ•£æ—¶&eacu

This preview shows document pages 1 - 9. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online