FINALS ECE 3109

A complex low-pass signal has a bandwidth  of 200 kHz. What is the minimum sampling rate for this signal?

• 200 000 Hz

• 300 000 samples/sec

• 400 000 samples/sec

• 200 000 samples/sec

A certain telemetry signal with a duration of 20 seconds is known to have spectral components from near dc to about 1 kHz but has negligible spectral content above that frequency. The signal is to be recorded, converted in digital format, and stored in memory for subsequent processing. To ease in reconstruction of the signal, the sampling rate is to be selected 25% greater than the theoretical minimum. What is the minimum number of samples of the signal that must be taken?

• 40 000 samples

• 2 000 samples

• 50 000 samples

• 2 500 samples

A telephone subscriber line must have  above 40. What is the minimum number of bits per sample? 

• 6 bits

• 5 bits

• 7 bits

• 8 bits

Assume that a signal has been sampled and the sample amplitudes are between -20 and +20V. It was  decided to have eight levels (L = 8). What is the SQNR_dB?

• 24.08 dB

• 49.92 dB

• 19.82 dB

• 30.0 dB

Telephone companies digitize voice by assuming a maximum frequency of 4000 Hz. What should be the sampling rate?

• 4 000 Hz

• 5 000 Hz

• 8 000 Hz

• 6 000 Hz

A pulse modulation technique the process of which is equivalent to the process of converting analog signal to digital data.

• PWM

• Delta modulation

• PCM

• PAM

A pulse modulation process that produces a 1-bit code which indicates an increase or decrease in the message signal’s amplitude.

• PAM

• Delta modulation

• PWM

• PCM

The process of representing the sampled values of the amplitude by a finite set of levels.

• sampling

• decoding

• quantization

• encoding

In the receiver, a _________ filter is used to reconstruct (demodulate) PAM, PWM and PPM signals into a recovered message signal

• Band stop filter

• Band pass filter

• LPF

• HPF

Consider the analog signal 

x(t) = 3cos50πt  + 10sin300πt – cos100πt

The folding frequency is

• 300 Hz

• 50 Hz

• 110 Hz

• 150 Hz