Tele3113 tut5


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Tele3113 tut5

  1. 1. 1 TELE3113 Analogue and Digital Communications Tutorial 5 I. P ROBLEM 1 1) Draw diagrams showing a Delta Modulator (DM). 2) Explain how DM works. Illustrate your answer with diagrams showing a typical waveform for the analogue signal and the delta modulated signal. 3) Explain slope overload in relation to DM. 4) Describe Adaptive Delta Modulation (ADM) and how the ADM reduce the effects of slope overload. II. P ROBLEM 2 1) Draw diagrams showing a Differential Pulse Code Modulation (DPCM). 2) Explain how DPCM differs from PCM. III. P ROBLEM 3 Consider the following binary sequence, 101011. 1) Draw a Binary Phase Shift Keying (BPSK) waveform for this sequence. 2) Draw diagrams of Differential Phase Shift Keying (DPSK) generator and demodulator. 3) Differentially encode the sequence. Assume an initial reference bit is 1. 4) Show how DPSK removes the 180◦ phase ambiguity. 5) If 4-ary Amplitude Shift Keying (ASK) is used for the modulation, sketch the modulated wave corresponding to the sequence. Assume the amplitude levels to be ±1 V and ±3 V. IV. P ROBLEM 4 Two analogue signals, of bandwidth 3 KHz and 6 KHz, are to be time division multiplexed (TDM) with threedigital sources of data rates of 6000 bps. The analogue signals are to be transmitted as 4-bit PCM signals. 1) Choose appropriate sampling frequencies for the analogue signals. What will be their corresponding data rates? 2) Design a TDM system to multiplex these five signals. Sketch a diagram illustrating the multiplexer and demultiplexer. 3) What is the data rate of the TDM signal?