Modulation Quiz
Q1. The baseband bandwidth of music for a broadcast FM signal is 15kHz,
the deviation ratio is 5. The RF bandwidth is:
(a) 75kHz
(b) 150kHz
(c) 35kHz
(d) 180kHz
Q2. The information capacity of a channel is given by:
S

(a) C  B log 2 1   bits/sec
N

S
(b) C  log 2 1  B  bits/sec
N
S

(c) C  log 2  B   dB
N

S

(d) C  10 log 10 1   dB
N

Q3. The theoretical maximum spectral efficiency of a simple binary
transmission is:
(a) 1 bit/sec/Hz
(b) 1 bit/Hz
(c) 2 bits/sec/Hz
(d) 1 bit/sec/Hz
Q4. A PAM scheme employs 8 amplitude levels, the spectral efficiency is:
(a) 3 bits/sec
(b) 6 bits/sec/Hz
(c) 6 bits/Hz
(d) 3 bits/sec/Hz
Q5. A PCM scheme for hi fidelity audio with baseband bandwidth 20kHz
employs a 16 bit code for each transmitted sample, the spectral efficiency of
the scheme is
(a) 2 bits/sec/Hz
(b) 20k bits/sec/Hz
(c) 320 kbits/sec
(d) 640 kbits/sec/Hz
Q6. A PCM scheme for hi fidelity audio with baseband bandwidth 20kHz
employs a 16 bit code for each transmitted sample, the minimum transmission
bandwidth required is:
(a) 20kHz
(b) 40kHz
(c) 320kHz
(d) 640kHz
Q7. The data rate for the PCM scheme of Q 6 is:
(a) 640kbits/sec
(b) 320kbits/sec
(c) 640kbits/sec/Hz
(d) 40kbits/sec
Q8. A modulation system has Eb/No = 10dB with a signal to noise ratio of
13dB. The spectral efficiency is:
(a) 2 bits/sec
(b) 2 bits/sec/Hz
(c) 0.5 bits/sec
(d) 0.5 bits/sec/Hz
Q9. Pulse shaping is employed in digital transmission to:
(a) Minimise ISI
(b) Maximise signal speed
(c) Prevent inter-modulation
(d) Remove sharp edges
Q10. The peak frequency deviation for an FM system with a 1 MHz sinusoidal
modulation is 100kHz. The peak phase deviation is:
(a) 0.1 radian
(b) 0.1o
(c) 10 radians
(d) 10o
Q11. An analogue telephone speech signal is to be used to modulate a carrier
for transmission over a channel. The required channel bandwidth for:
(a) AM is 3.4kHz
(b) FM with peak frequency deviation 8.5 kHz is 20.4kHz
(c) 8 bit QPSK is 32kHz
(d) Conversion to 32kbit/sec ADPCM and then MSK is 32kHz.
Q12. A broadcast FM high fidelity audio signal is transmitted at 88.1MHz with
a deviation ratio of 5. The required transmission bandwidth is:
(a) 200kHz
(b) 150kHz
(c) 88.1MHz
(d) 180kHz
Q13. GMSK gives a practical spectral efficiency of:
(a) 1bps/Hz
(b) 2bps
(c) 1.9bps/Hz
(d) 1.9bps
Q14. MSK is:
(a) equivalent to QPSK
(b) binary FSK with the minimum distance between the two transmission
frequencies
(c) FSK with Gaussian pulse shaping
(d) PSK with Gaussian pulse shaping
Q15. AM is
(a) An efficient modulation scheme in power terms.
(b) Very wasteful in power terms but easy to demodulate
(c) Inefficient and difficult to demodulate
(d) Spectrally inefficient but easy to demodulate
Q16. The signal spectrum for a 2Mbits/sec QPSK signal is:
(a)
(b)
(c)
fc+2 MHz
(d)
fc+2MHz
fc+1MHz
fc+1MHz
Q17. The spectral efficiency of n-level PAM is:
(a) n bits/sec
(b) 2n bits/sec/Hz
(c) n bits/sec/Hz
(d) 2n bits/Hz
Q18. A 2kbits/sec digital signal is transmitted using PRK, the spectrum is:
(a)
(b)
(b)
fc+2kHz
fc+1kHz
(d)
fc+1kHz
fc+2kHz
Q19. A 2Mbits/sec binary FSK signal with peak deviation = 10MHz has a
spectrum:
(a)
(b)
fc-8MHz
fc+10MHz
fc+12MHz
(b)
(d)
fc-4MHz
fc+6MHz
fc+5MHz
Q20. A channel has a bandwidth of 1MHz. The signal to noise ratio required
to allow error free communication at an information rate of 2 MBits/sec is:
(a) 2
(b) 3dB
(c) 4.8dB
(d) 2dB
Q21. FM is:
(a) a linear modulation scheme
(b) a non-linear modulation scheme
(c) wasteful of signal power
(d) spectrally efficient
Q22. AM is:
(a) a linear modulation scheme
(b) a non-linear modulation scheme
(c) spectrally inefficient
(d) power efficient
Q23. The peak frequency deviation for an MSK system with data rate
56kbits/sec is:
(a) 56kHz
(b) 28kHz
(c) 224Hz
(d) 14kHz
Q24. The Signal to noise ratio for a certain system is 10dB. The maximum
information rate over the channel for error free communications is found to be
1Mbit/sec. the transmission bandwidth is:
(a) 289kHz
(b) 1MHz
(c) 0.5MHz
(d) 2MHz
Q25. OOK is:
(a) More power efficient than AM
(b) Less power efficient than AM
(c) The same as AM
(d) More spectrally efficient than AM