Communications Systems 2 Examination for B.Eng. in Electronic Engineering Program, Exams of Data Communication Systems and Computer Networks

Download Communications Systems 2 Examination for B.Eng. in Electronic Engineering Program and more Exams Data Communication Systems and Computer Networks in PDF only on Docsity! Page 1 of 4 CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Semester 2 Examinations 2010/11 Module Title: Communications Systems 2 Module Code: ELTR7008 School: Electrical and Electronic Engineering Programme Title: B.Eng. in Electronic Engineering Programme Code: EELXE_7_Y3 External Examiner(s): Mr. A. Donnellan Mr. I. Kennedy Internal Examiner(s): Dr. O. Gough Instructions: Answer four Questions Duration: 2 Hours Sitting: Autumn 2011 Requirements for this examination: Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator. Page 2 of 4 Q1. (a) A signal tVtVm 00 cos)(  is sampled by a pulse train represented by the following series,     0 cos)( n sn tnatS  (i) Show that the modulated signal consists of multiple side-frequency pairs. [6 marks] (ii) Explain how the choice of sampling frequency and low pass filter make signal recovery possible. [7 marks] (b) The amplitude spectrum of a bandlimited signal is shown in Fig. Q1 and is sampled at fS. Sketch the frequency spectrum of the sampled signal for (i) fS =2.5fm, (ii) fS =2fm, and (iii) fS =1.5fm. In each case decide if signal recovery is possible and explain how this is achieved in practice. [3x4 marks] Q2. (a) Draw the block schematic of a simple linear PCM modulator and discuss its operation. Explain the quantization mechanism employed with appropriate sketches and its effect on recovered signal quality. [10 marks] (b) Show that the quantization noise power for a linear PCM system is given by 12 2 qN [10 marks] (c) A PCM system is required for an audio application. If the audio signal is to be band limited to 12 kHz and the dynamic range must exceed 56 dB determine the resulting data rate for a linear converter. [5 marks] Amplitude Spectrum Frequency fm Fig. Q1