Questions:
1.
An analog signal carries 4 bits in each signal unit. If 1000 signal units are
sent per second, find the baud rate and the bit rate
2.
The bit rate of a signal is 3000. If each signal unit carries 6 bits, what is
the baud rate?
3. Find the minimum bandwidth for an
ASK signal transmitting at 2000 bps. The transmission mode is half-duplex.
4. Given a
bandwidth of 5000 Hz for an ASK signal, what are the baud rate and bit rate?
5. Given a
bandwidth of 5000 Hz for an 8-PSK signal, what are the baud rate and bit rate?
6. A
constellation diagram consists of eight equally spaced points on a circle. If
the bit rate is 4800 bps, what is the baud rate?
7. We have
an audio signal with a bandwidth of 4 KHz. What is the bandwidth needed if we
modulate the signal using AM?
Solution:
1. Baud rate
= 1000 bauds per second (baud/s)
Bit rate = 1000 x 4 = 4000 bps
2.
Baud
rate = 3000 / 6 = 500 baud/s
3. In ASK the baud rate and bit rate are the same. The
baud rate is therefore 2000. An ASK signal requires a minimum bandwidth equal
to its baud rate. Therefore, the minimum bandwidth is 2000 Hz.
4. In ASK the baud rate is the same as the bandwidth,
which means the baud rate is 5000. But because the baud rate and the bit rate
are also the same for ASK, the bit rate is 5000 bps
5. For PSK the baud rate is the same as the bandwidth,
which means the baud rate is 5000. But in 8-PSK the bit rate is 3 times the
baud rate, so the bit rate is 15,000 bps.
6. The
constellation indicates 8-PSK with the points 45 degrees apart. Since 23= 8, 3
bits are transmitted with each signal unit. Therefore, the baud rate is
4800 / 3 = 1600 baud
7. An AM signal requires twice the bandwidth of the
original signal:
BW = 2 x 4 KHz = 8
KHz
