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EM Theory and Wireless Communication
(RFEA301) Assignment 2 2020
MEMO
INSTRUCTIONAL PROGRAMME: BET: Electronic Engineering
INSTRUCTIONAL OFFERING: BET
SUBJECT CODE/S: RFEA
DATE: 24 August 2020 DURATION: 48hrs
TOTAL MARKS: 70
EXAMINER/S: A Pillay MODERATOR: Dr C Mulangu
INSTRUCTIONS:
[1] ANSWER ALL QUESTIONS.
[2] THIS IS AN OPEN-BOOK ASSESSMENT. THE ASSIGNMENT WILL BE AVAILABLE FOR DOWNLOAD,FROM 24 AUGUST 2020, 5AM AND CLOSED AFTER 25 AUGUST 2020, 5AM.
[3] YOU MAY EITHER PRINT SAVE YOUR WORK REGULARLY IN THE EVENT OF A COMPUTER CRASH. DO NOT CHANGE THE DIRECTORY IN WHICH THE PROJECT IS SAVED, OR THE PROJECT NAME.
[3] YOUR ORIGINAL MS WORD QUESTION PAPER WITH ANSWERS INSERTED MUST BE SAVED AS A PDF DOCUMENT IN THIS FORMAT: STUDENTNUMBER.PDF.
[4] UPLOAD THIS PDF DOCUMENT TO MOODLE WITHIN 10 MINUTES AFTER THE ASSESSMENT HAS ENDED.
[4] MANAGE YOUR TIME EFFECTIVELY. ANY WORK SUBMITTED BETWEEN 5AM AND 9AM ON THE 25 AUGUST 2020 WILL BE RESTRICTED TO A MAXIMUM MARK OF 50% FOR THE ASSESSMENT. ANY WORK SUBMITTED AFTER 9AM ON THE 25 AUGUST 2020 WILL NOT BE MARKED AND WILL RESULT IN 0% FOR THE ASSESSMENT.
SURNAME & INITIALS:
STUDENT NUMBER:
- Determine the following with reference to Figure 1.
Figure 1
1.1 Modulation index. (1)
1.2 If the sketch is accurate on the time scale and fc = 55 kHz, find the modulation frequency from the oscilloscope display shown.(1)
1.3 Carrier power in 75Ω. (1)
1.4 Power in one sideband. (1)
1.5 Determine the Total power dissipated in 75 Ω. (1)
1.6 What percentage is the carrier power relative to the Total power?(1)
1.7 Calculate the bandwidth that is required to transmit this AM signal? (1)
1.8 Sketch the time domain waveform, include the voltage and frequency, if only the upper sideband is transmitted (assume no carrier). (2)
- The AM signal of Figure 2 , with carrier frequency of 1 MHz and modulation frequency
3.8 Determine the total information power.(2)
- A linear VCO produces a 2 Vpeak unmodulated 100 MHz carrier and has a modulation sensitivity of k0 = 10 kHz/volt. If the VCO is modulated by a 707.1 mV rms, 5 kHz cosine signal. Determine the following.
4.1 Peak deviation of the carrier frequency.(1)
4.2 Modulation index.(1)
4.3 Relative amplitude of all significant spectral components in the FM signals.^ (m^ f=2).(3)
4.4 Calculate the actual peak voltages of the spectral components.(3)
4.5 Sketch the frequecny spectrum. Include the actual frequencies for each component.(6)
- Calculate the number of bits that are needed to quantize an analog signal into at least 250 levels.(1)
- If 6 bits are used in a PCM system, how many separate input levels are distinguishable?(1)
- Four channels of 5bit PCM are multiplexed at 8k frames/s (with no additional pulses added). Determine the output pulse rate and pulse width.(2)
- What advantage does Delta modulation have over PCM?(1)
- A baseband transmisssion system with an overall 30.1 dB signal-to-noise ratio is to be used for delivering an information rate of 45 Mbps.
9.1 Determine the absolute minimum bandwidth.(2)
9.2 Calculate the number of levels of encoding is required.(1)
9.2 (^) The resulting system has a resolution equivalent to an n -bit PCM system. What is the value of n ?(1)
- Determine the following for a binary FSK signal with a mark frequency of 49 kH, a space frequency of 51 kHz and an input bit rate of 2 kbps.
10.1 The peak frequency deviation.(1) 10.2 The minimum bandwidth.(1) 10.3 The baud rate.(1)
- A PCM signal is modulated on a microwave carrier as 8-PSK.
11.1 Determine what the theoretical C/N (in dB) necessary at the receiver in order for the system to make only one error in 100 000 bits?(2)
11.2 How many more dB of system gain is required for 16-PSK for the same BER?(1)
- An FSK system must maintain less than 10 -3^ BER, Calculate the minimum allowable received E (^) b /N (^) o?(1)
- Identify with a few letters and numbers, the constellations of Figure 4. (4)
- What advantage does Differential-QPSK have over QPSK?(1)
- Sketch the QPSK constellation defined by (00) = 45˚, (01) = +45˚ ,(11) = +135˚ , and (10) = - 135˚.(2)
- For the data sequence, 101001011110, and constellation of Q15, write the corresponding output phase sequence.(3)
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