dc qbank - Department of ECE Question Bank EC-304(Digital...

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Department of ECE Question Bank- EC-304(Digital Communication) 6th Semester,Electronics&Communication Engineering Chapter 1 Q1:- A band-pass signal has a spectral range that extends from 20 to 82 kHz. Find the acceptable range of the sampling frequency ƒs. Q2:- A band-pass signal has a center frequency ƒo and extends from ƒo-5kHz to ƒo+5kHz.The signal is sampled at a rate ƒs = 25khz.As the center frequency ƒo varies from ƒo = 5khz to ƒo = 50khz.Find the ranges of ƒo for which the sampling rate is adequate. Q3:- The signal v(t) = cos5pt+0.5cos10pt instantaneously sampled. The interval between samples is Ts. Find the maximum allowable value for Ts. Q4:-The band-pass signal v(t)=cos10wt+cos11wt+cos12wt is sampled by a impulse train s(t)= ( t- kTs ). −∞ (a) Find the maximum time between samples, Ts, to ensure reproduction without error. (b) Using the result obtained in (a),obtain an expression for v s(t)=S(t)v(t). Q5:- The TDM system is used to multiplex the four signals m 1 (t)= coswt, m 2 (t)=0.5coswt, m 3 (t)=2cos2wt and m 4 (t)=cos4 w 0 t. If each signal is sampled at the same sampling rate calculate the minimum sampling rate ƒs. Q6:- Three Signals m 1 , m 2 and m 3 are to be multiplexed m 1 and m 2 have 5kHz bandwidth and m 3 has a 10 kHz bandwidth. Design a commutator switching system so that each signal is sampled at its Nyquist rate. Q7:- The signal v(t)= cos8wt is sampled by using natural sampling . Determine the minimum sampling rate ƒs. Q8:- Draw an AMI waveform corresponding to a binary bit stream 100110010101. The polarity of the first pulse in the waveform may be set arbitrarily. Q9:- Write the non-linear difference equation of the delta modulator. Let m(t) = 18x10³sin2pt and let the samples occur every 0.05 sec. starting at t=0.01 sec. The step size is 5mV. Q10:- The input to DM is m(t) = 0.01t. The DM operates at a sampling frequency of 20Hz and has a step size of 2mV. Sketch the data modulator output , m (t) and m˜ (t).
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Q11:- The input to DM is m(t) = Kt. Prove by graphically determining m(t) = Kt.Prove, by graphically determining m˜(t), that slope overload occurs when K exceeds a specified value. What is the value in terms of the step size S and the sampling frequency ƒs? Q12:- Specify the Nyquist rate and the Nyquist interval for each of the following signals: (a) g(t) = sinc(200t) (b) g(t) = sinc²(200t) (c) g(t) = sinc(200t) + sinc²(200t). Q13 Plot the spectrum of PAM wave produced by the modulating signal m(t) =A m cos(2pƒmt) assuming a modulation frequency ƒm = 0.25Hz, sampling period Ts = 1s , and pulse duration T = 0.45s. Q14 Twelve different message signal each with a band-width of 10 kHz, are to be multiplexed and transmitted. Determine the minimum band-width required for each method if the multiplexing/modulation method used is: (a) FDM, SSB. (b) TDM, PAM
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dc qbank - Department of ECE Question Bank EC-304(Digital...

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