tailieunhanh - Lecture Digital communication systems - Lecture 13

This chapter includes contents: Deciding what is news, news reporting in the digital age, categories of news and reporting, the news flow, the wire services, media differences in news coverage, readership and viewership. | INTRODUCTION TO EECS II DIGITAL COMMUNICATION SUSTEMS Fall 2012 Lecture 13 Frequency response Filters Spectral content Fall 2012 Lecture 13 Slide 1 Sinusoidal Inputs and LTI Systems A very important property of LTI systems or channels If the input x n is a sinusoid of a given amplitude frequency and phase the response will be a sinusoid at the same frequency although the amplitude and phase may be altered. The change in amplitude and phase will in general depend on the frequency of the input. Fall 2012 Lecture 13 Slide 2 Complex Exponentials as Eigenfunctions of LTI System x n ejQn h . y n H Q ejQn Eigenfunction Undergoes only scaling -- by the frequency response H Q in this case H Q 2 h m e Qm m V h m cos Qm - j Vh m sin Qm mm This is an infinite sum in general but is well behaved if h . is absolutely summable . if the system is stable. We also call H Q the discrete-time Fourier transform DTFT of the time-domain function h . --- more on the DTFT later. Fall 2012 Lecture 13 Slide