• Air University, Islamabad

• ELECTRICAL 1023

Old Paper 4th Semester

IAL INSTRUCTIONS: )

This question paper contains 04 questions spanned over 02 pages. The tables of properties of CTFS, DTFS, CTFT and DTFI' are

also attached.

Calculators are NOT allowed. Try to be neat and organized. Vague or badly motivated answers are considered wrong.

1. 2. 3. Attempt all sub-parts of a question together. Failure to do so may result in no credit for the parts attempted separately.

4.

5,

Draw properly labeled/formatted relevant graphs/circuit &block diagrams where necessary.

In case of any confusion, make an assumption and continue. Clearly state your assumption, if any.

Question #01.CLO01 = PLO 017> C 02

a. Express the given signalx[n] in terms of unit step functions

" T, = [TTHE

b. Sketch the following signal

xfn] = 8[n] +3 1 8[n - 11+ (5) 132 st-21+ (E) 1,3 8[n —3]

c. The impulse response h(t) of a system is given below. Check whether this system is memory less, causal and stable.

Justify your answers by appropriate reasoning.

h(t) = e 2u(t)

Qiiestion #021610/021(PLOI02:¥/C 0315 : A Marksi L0 ¥i0%

a. Impulse response h(t) of a continuous time system is shown in the figure below. The input to this system is an

impulse train denoted by x(t) such that

(-]

x(t) = Z 8(t — kT)

k=—oco 1

Sketch x(t) assuming T = 3/2 sketch y(t) = x(t) * h(t)