BEKC 2453 COMMUNICATION SYSTEM
TUTORIAL 4: DIGITAL COMMUNICATION
a) With the help of an appropriate block diagram, describe basic function of the Pulse Code
Modulation digital transmission system.
b) An information signal in the form of Vm(t) = 4 cos(4 x 104)V is to be transmitted through a PCM
system using an 4 bits binary number. The sampling frequency used is 21% higher than the
minimum sampling rate. Determine:
i.
The quantization level
ii.
The sampling frequency used
iii.
The transmission bit rate (bps)
iv.
The resolution step
v.
The maximum quantization error
c) Another task is given to the same TN-TOUCH engineer to design a PCM system. The system has
the following specification as shown in Table 1. For the PCM system, determine
i.
Minimum sampling rate
ii.
Minimum number of bits used in PCM code
iii.
Resolution
iv.
Quantization error
Table 1: The specification value for PCM system
No.
Parameter
Value
1
Maximum analog input frequency
3.27 kHz
2
Maximum decoded voltage (at the receiver)
±2.55 V
3
Dynamic range
Faculty of Electrical Engineering
Universiti Teknikal Malaysia Melaka
63 dB
d) Given a binary data of 10101 as an input to the modulator. Sketch appropriately the output carrier
waveform for the following cases.
i.
ASK modulator
ii.
FSK modulator
iii.
PSK modulator
e) You are given a task to design a device that will convert an analog input signal into a digital signal
based on Pulse Code Modulation (PCM) technique. The following design requirement and
specifications are given.
• The maximum and minimum range of the input signal is ± 20 V.
• The maximum frequency contained in the input signal is 15 kHz.
• The transmission rate to be achieved must not less than 96 kbps.
• The quantization error must not more than 5% of the maximum value of the input signal.
Complete you design by determine the value you will use for following parameters.
i.
The minimum sampling frequency.
ii.
The resolution of the quantization process.
iii. The quantization error
iv.
The number of bits per sampling.
v.
The transmission rate after the encoding process
Faculty of Electrical Engineering
Universiti Teknikal Malaysia Melaka