通信原理(英文版)1

1、1,principles of communications,2,chapter 1 introduction 1.1 historical review of communication origin of ancient communication two modes of communication development of modern communication,3,1.2 message, information group delay - () = d()/d = k influence of distortion: waveform distortion, inter-sy

2、mbol interference linear distortion including frequency distortion * phase 0 becomes slowly varied phase (t)； * spectrum becomes narrow band spectrum from single frequency,44,frequency selective fading assume: there are only two paths with identical attenuation and different delays, transmitting sig

3、nal is f(t)，received signals are af(t - 0) and af(t - 0 - )；spectrum of transmitting signal is f()。 then f(t) f() af(t - 0) a f() e-j0 af(t - 0 - ) a f() e-j(0 + ) af(t - 0) + af(t - 0 - ) a f() e-j0 (1+e-j) h() = a f() e-j0 (1+e-j)/f() = ae-j0 (1+e-j) |1+e-j| = |1+cos-jsin|=|(1+cos)2+sin21/2| =2|co

4、s(/2)| 3 categories of signal： * deterministic signal * random phase signal * fluctuation signal,45,1.5 noise in channel,classified according to origins： man-made noise：electric sparks, natural noise：lightning, atmosphere noies, thermal noise,. classified according to characteristics: impulse noise narrow band noise fluctuation noise main noise involved in the following discussion on communication systems is: white noise thermal noise is a kind of typical white noise 1.6 brief summary