1. What type of transmissions represented the first type of digital communications? A. Digital signal processing B. Amplitude-shift keying C. Morse code D. On-off keying

1. What type of transmissions represented the first type of digital communications?
A. Digital signal processing
B. Amplitude-shift keying
C. Morse code
D. On-off keying
2. Each form of digital modulation has implications in terms of spectral efficiency, power
distribution, and _________.
A. amplitude
B. bandwidth
C. performance
D. distortion
3. Which of the following is a key characteristic of orthogonal frequency-division
multiplexing?
A. Amplitude modulation
B. Noise performance
C. Digital modulation
D. Spectral efficiency
4. When a carrier is conveying intelligence by simply turning it on or off according to a
prearranged code, this type of transmission is called ____________.
A. continuous wave
B. sine wave
C. square wave
D. cosine wave
5. Why must modulated signals be demodulated?
A. To recover the original intelligence
B. To improve the spectral efficiency of digital transmissions
C. To enable implementation of advanced features
D. To produce one or more significant sideband pairs

6. What is one advantage provided by a phase-shift keying (PSK) system?2
A. Improved noise performance
B. Better ionospheric fading characteristics
C. Low probability of error
D. Transmitter frequency is constantly changing
7. The advantage of a differential phase-shift keying (DPSK) system is that_____________
is (are) not required.
A. carrier synchronizer
B. voltage-controlled oscillators
C. upper and lower sidebands
D. carrier recovery circuitry
8. Where is minimum-shift keying (MSK) widely used?
A. Radios
B. Cordless phones
C. Military applications
D. Garage-door openers
9. The term “M-ary” in M-ary modulation derives from the word ___________.
A. binary
B. baud
C. bit
D. bandwidth
10. Which of the following achieves high spectral efficiencies because the spacing of each
carrier is as close as theoretically possible?
A. Direct-sequence spread spectrum (DSSS)
B. Quadrature amplitude modulation (QAM)
C. Orthogonal frequency-division multiplexing (OFDM)
D. Code-division multiple access (CDMA)
11. The two forms of spread spectrum are frequency hopping and ______________.
A. direct sequence
B. continuous wave
C. spectral regrowth
D. voltage controlled
12. What type of coding is used to minimize data errors in the data transmission process?
A. On-channel
B. Channel

C. In band
D. Multiple access
13. Which of the following is the basis for cellular systems employing the code-division
multiple access (CDMA) standard?
A. COFDM
B. QPSK
C. OFDM
D. DSSS
14. What type of receiver detects the phase shift in the received signal?
A. Binary phase-shift keying
B. Quadrature phase-shift keying
C. Differential phase-shift keying
D. Frequency-shift keying
15. Excessive _______ means that a receiver cannot differentiate one symbol from another.
A. noise
B. ISI
C. modulation
D. frequencies
16. The ________ demodulator reverses the process of modulation, thereby recovering the
original binary data signal.
A. QAM
B. ISM
C. FSK
D. BER
17. What requirements for a data stream depend on the encoding method used to transmit the
data?
A. Frequency
B. Noise
C. Bandwidth
D. Baud rate
18. Why are signals that are in quadrature said to be orthogonal?
A. They do not interfere with each other.
B. They split into two paths.
C. They can shift to one of two predetermined phase states.4
D. The amount of data that can be transmitted over time.
19. The _____________ gives a visual indication of system linearity and noise performance.
A. spread spectrum
B. pseudonoise
C. spectral regrowth
D. constellation pattern
20. Which of the following filters has the important property that its impulse response rings
at the symbol rate, which means that it is capable of minimizing ISI?
A. Bandpass
B. Low-pass
C. Raised-cosine
D. Gaussian
21. Impedance is an AC quantity is composed of both resistance and ______________.
A. complexity
B. reactance
C. magnitude
D. expression
22. A sine or cosine wave can be thought of as consisting of both positive and negative
______________.
A. frequencies
B. signals
C. ranges
D. carriers
23. What law allows us to predict the minimum bandwidth required for information transfer
in a given time interval?
A. Ohm’s
B. Gaussian’s
C. Fourier’s
D. Hartley’s
24. The power of DSSS systems is largely in the spreading and dispreading of the received
signal because it gives rise to a phenomenon known as ______________.
A. channel coding
B. spectral regrowth
C. processing gain5
D. frequency-hopping
25. OFDM modulation is essentially the converse of ____________.
A. demodulation
B. efficiency
C. high data rates

D. interference