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Department of Electrical Engineering
Faculty of Engineering & Applied Sciences
Riphah International University
Mid Term Online Examinations, Spring 2021 Semester
B.Sc. Electrical Engineering
Course Name:
Communication
Systems______
Date of Examination:
22-04-2021_______
Course Code:
EE-344________
Total Marks:
30_______________
Semester:
VI___________
Exam Duration:
03hours____________
Section:
Electronics_____
Teacher Name:
Zohaib Ahmad Khan
_____________________________________________________________________________________
Instructions: Please read the below instruction before attempting the exam questions.
1- The exam is an open book. Students can get help from books and lecture notes.
2- Please write your full name, SAP ID, page number, and signature on top of each answer sheet.
3- Please use good quality paper.
4- Attempt all questions; marks and CLOs of each question are duly mentioned.
5- For student’s queries, the course teacher will be available from 10:00 am to 11:00 am on zoom
session. The link of zoom session will be shared at 9:50 am to the class whatsapp group. Please
ask the relevant logical question.
6- After completing the exam, please scan or take a good quality photograph of each answer
sheet and convert it to PDF file in the correct ascending order. Save the PDF file using your
name and SAP-ID. e.g., (Muhammad Ali 122121). Please make sure the converted PDF must be
readable.
7- If necessary, use online software to reduce the PDF file size. (https://smallpdf.com/compress-
pdf)
8- Upload PDF file on Moellim before the end time. For students having low internet speed,
please start uploading well before the end time.
9- The hardcopy of answer sheets must be retained by students until the announcement of
results.
10- Faculty have formed a zero-tolerance policy about cheating in examinations. Therefore,
based on your exam answers sheets, if the teacher found any student involved in copying from
peers will have an online viva session with the course teacher or get zero marks.
Q 1: [2+3+2 +3 marks]
Consider the baseband signal, which is the product of two sinusoidal signals. The frequency in one
sinusoidal signal is your respective SAP id. (CLO-1)
m(t)= SAP/4 *sin (2π SAP t) sin (2π 600t)
a) Sketch the spectrum of m(t).
b) Find and sketch the spectrum of DSB-SC signal m(t) cos (2π3*SAPt).
c) Identify the upper sideband (USB) and lower sideband (LSB) spectra.
d) Is it possible to demodulate the modulated signal? if yes which type of demodulator is required
and sketch the spectrum of demodulated signal.
