EE3550 – Practice Final Exam Questions
(Note – The actual final exam will probably be different in length.)
Part 1: Open-book, Open-notes (Covers through Digital Data/Analog
Signals chapters 3-5)
1. You are assigned the task of digitizing a waveform. The waveform has an average
voltage of 3V, and the noise has an average voltage of 1mV. The maximum frequency
present in the waveform is 5MHz.
a. What is the minimum sampling rate needed?
b. What is the minimum number of bits you need to represent each sample digitally so
that the quantization noise is less than the noise already present?
2. Compute the signal-to-noise power ratio (in dB) for the following measurements:
a. On an oscilloscope, the signal has an average value of 5V peak-to-peak, and the
noise has an average value of 0.25V peak-to-peak.
b. A power meter reads 3W power for the signal, and 25mW power for the noise.
c. A spectrum analyzer displays the signal power at -15dBm, while the noise is at
-70dBm.
3. You are setting up a 1km data link using coaxial cable with the following
characteristics:
You are sending a signal that occupies frequencies between 0Hz and 100MHz.
At the source, the signal power is 10mW and the noise is negligible.
The temperature at the receiver is 30 degrees C.
The coaxial cable has attenuation of 6dB/100m at 100MHz.
Compute the following:
a. Signal power at the receiver.
b. Thermal noise at the receiver.
c. Signal-to-Noise ratio (in dB) at the receiver.
d. Maximum capacity (in bps) for this data line.
e. The number of signal levels needed to support this maximum capacity.
2. Represent the transmission of the following bits using the specified digital signaling
schemes: 001011101011
a. NRZ
b. AMI (first ‘1’ should be at high level)
c. Manchester
