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Set A Period and Frequency
1. _______ signal repeats a pattern over and over again.
ans: A periodic
2. _______ signal has no repeating pattern.
ans: An aperiodic
3. The _______ wave is the simplest analog signal.
ans: sine
4. The sine wave is an example of _______ signal.
ans: an analog
5. On a time-domain plot, the _______ of a signal is the vertical value from a point on the curve to the x-axis.
ans: amplitude
6. A simple sine wave completes one cycle in one microsecond. Its frequency is _______.
ans: 1 MHz
7. The period of a signal is usually expressed in _______.
ans: seconds
8. The frequency of a signal is usually expressed in _______.
ans: Hz
9. The _______ of a signal is usually expressed in Hz.
ans: frequency
10. The _______ of a signal is usually expressed in seconds.
ans: period
11. The frequency of a signal is inversely related to its _______.
ans: period
12. The _______ of a signal is its number of cycles per second.
ans: frequency
13. The _______ of a signal is the time it needs to complete one cycle.
ans: period
14. The value of a simple sine wave at time zero is its maximum positive value. The phase shift is therefore _______ degrees.
ans: 90
15. The value of a simple sine wave at time zero is zero. The next value is negative. The phase shift is therefore _______ degrees.
ans: 180
16. The value of a simple sine wave at time zero is zero. The next value is positive. The phase shift is therefore _______ degrees.
ans: 0
17. A nanosecond is _______ as long as a microsecond.
ans: 0.001
18. A picosecond is _______ as long as a nanosecond.
ans: 0.001
19. Ten thousand milliseconds equal _______.
ans: ten seconds
20. One thousand picoseconds equal _______. ans: one nanosecond
21. A signal with a frequency of 10 MHz has more cycles per second than a signal with a frequency of _______.
ans: 10 KHz
22. A signal with a period of 1 microsecond has a higher frequency than a signal with a period of _______.
ans: one millisecond
23. The equivalent of 20 MHz is _______.
ans: 20 x 106 Hz
24. A signal with a frequency of 1 GHz has more cycles per second than a signal with a frequency of _______.
ans: one MHz
25. A sine wave has a frequency of 10 Hz. Its period is _______.
ans: 0.1 second
26. A sine wave completes one cycle in 20 seconds. Its frequency is _______.
ans: 0.05 Hz
27. A signal has a constant value of 10 volts. Its frequency is _______ Hz.
ans: zero
28. A simple sine wave is offset one half cycle at time zero. This is a phase shift of _______ degrees.
ans: 180
29. A simple sine wave completes one cycle in _______ degrees.
ans: 360
30. A phase shift of 180 degrees is the same as a phase shift of _______ of a cycle.
ans: one half
31. In a time-domain plot, signal amplitude is plotted against _______.
ans: time
32. A time-domain plot shows signal _______ with respect to time.
ans: amplitude
33. In a frequency-domain plot, the signal amplitude of a simple sine wave is plotted against _______.
ans: frequency
34. In a frequency-domain plot of a composite signal consisting of twelve sine waves (all of different frequencies and amplitudes), there are _______vertical bars.
ans: 12
35. A signal with constant amplitude of ten volts has a frequency of _______.
ans: 0
36. The _______ of a signal is the collection of all its component frequencies.
ans: frequency spectrum
37. The _______ of a signal is the width of its frequency spectrum.
ans: bandwidth 38. A signal is decomposed into two sine waves, one with a
frequency of 10 Hz, the other with a frequency of 90 Hz. The bandwidth of the signal is _______ Hz.
ans: 80
39. A signal is decomposed into three sine waves with frequencies of 10, 20, and 30 Hz. The bandwidth of the signal is _______ Hz.
ans: 20
40. The bandwidth of a signal is 10 KHz. The frequency of the sine wave with the highest frequency is 11 KHz. The frequency of the sine wave with the lowest frequency is _______ Hz.
ans: 1
41. The _______ is the time required to send one bit.
ans: bit interval
42. The _______ is the number of bits sent in one second.
ans: bit rate
43. A bit interval of 0.1 seconds means a bit rate of _______bps.
ans: 10
44. A digital signal has a bit rate of 200 bps. The bit interval is _______ seconds.
ans: 0.005
45. A bit interval of 10 milliseconds means a bit rate of _______bps.
ans: 100 46. A digital signal has a bit rate of 50 Kbps. The bit interval is
_______ microseconds. ans: 20
Set B. Analog communications problems
1. the transmission of information by electric means
2. the electrical medium that bridges the distance from source to destination
3. waveform perturbation caused by imperfect response of the system to the desired signal itself
4. contamination by extraneous signals from human sources other transmitters, power lines and machinery, switching circuits, and so on
5. random and unpredictable electrical signals produced by natural processes both internal and external to the system
6. the gap between those frequencies for which the resonant effect is 70.7% or more of its maximum value at resonance
7. ratio of its maximum capacitance to its minimum capacitance.
8. parallel LC circuit which is sometimes called what?
9. circuit capable of continuously generating a repetitive waveform of the desired frequency
10. oscillators requiring an external input signal are called what?
11. An oscillator circuit whose main element is inductor
12. An oscillator circuit whose main element is capacitor
13. An oscillator circuit whose main element is crystal
14. A three stage amplifier system has a 3dBbandwidth of 500kHz determined by an LC tuned circuit at its input and operates at 24C. The first stage has a power gain of 15dB and a NF of 5dB. The second and third stages are identical, with power gains of 30dB and NF=2dB. The output load is 500 ohms. The input noise is generated by a 10kohm resistor. Calculate
a. The noise voltage and power at the input and output of this system
b. The overall noise figure for this systemc. The actual output noise voltage and power
15. An amplifier operating over a 4MHz bandwidth has a 150-ohm source resistance. It is operating at 28C, has a voltage gain of 20dB and has an input signal of 5uV. Determine rms output signal
16. A transistor amplifier has a measured SNR power of 10dB at its input and 5 at its output. Calculate
a. A. NRb. B. NF
17. What do you call the type of distortion that occurs during 100% modulation using AM?
18. The difference frequency in an AM signal is called what?19. Which part of an AM signal has no intelligence?20. What do you call any unwanted signal received by the IF
stage.21. In an AM, if the local oscillator frequency is 650khz, what
are the frequencies at the output of the mixer?22. Standard IF of an AM?
23. In a DSBFC using m=0.75, what percentage of the transmitted signal is consumed by the sidebands?
24. What part in an AM modulator gives high impedance to the carrier, LSB and USB?
25. A type of modulation wherein intelligence is superimposed on the carrier before amplification.
26. What type of amplifier is normally used to amplify RF signals?
27. What do you call the higher frequency self-oscillations in a RF amplifier?
28. What do you call a type of diode used for modulating carriers with frequencies higher than 100 MHz?
29. What are the three basic blocks of a TRF receiver?30. What part of an AM receiver is also known as the first
detector?31. What do you call the distortion that results from undesired
mixer outputs?32. What are the 3S of a good receiver circuit?33. What is the simplest type of AM demodulator?34. What do you call the baseline representation of the input
noise in a receiver circuit?35. What do you call a type of modulation wherein the
intelligence is injected in the base of a transistor?36. What do you call the condition that results from imperfect
modulation?37. A 1 MHz carrier is amplitude modulated by an audio signal
which contains all frequencies in the range 300 Hz to 5 kHz. What are the frequency bands which are output? What is the output bandwidth? Draw the spectral diagram of these signals.
38. A 1.5 MHz carrier is amplitude modulated by three sinusoidal signals of frequency 500 Hz, 800 Hz and 1,400 Hz. What are the frequencies in the AM spectrum?
39. An AM signal is represented by the equation
v = ( 15 + 3 Sin( 2 * 5 * 103 t) ) * Sin( 2 * 0.5 * 106 t) volts40. A transmitter puts out a total power of 25 Watts of 30% AM
signal. How much power is contained in the carrier and each of the sidebands?
41. A sinusoidally modulated ordinary AM waveform is shown below.
(a) Determine the modulation index. (b) Calculate the transmission efficiency. (c) Determine the amplitude of the carrier which must be added to attain a modulation index of 0.3.
42. The output signal from an AM modulator is:
s(t) = 5cos(1800π t) + 20cos (2000π t) + 5cos (2200π t)
(a) Determine the modulation index.
(b) Determine the ratio of the power in the sidebands to the power in the
carrier.
43. Suppose that on an AM signal, the value read from the graticule on the oscilloscope screen is 5.9 divisions and is 1.2 divisions.
a. What is the modulation index?b. Calculate and m if the vertical scale is 2 V per division. (Hint:
Sketch the signal.)
44. A standard AM broadcast station is allowed to transmit modulating frequencies up to 5 kHz. If the AM station is transmitting on a frequency of 980 kHz, compute the maximum and minimum upper and lower sidebands and the total bandwidth occupied by the AM station.
45. An AM transmitter has a carrier power of 30 W. The percentage of modulation is 85 percent. Calculate (a) the total power and (b) the power in one sideband.
46. An antenna has an impedance of An unmodulated AM signal produces a current of 4.8 A. The modulation is 90 percent. Calculate (a) the carrier power, (b) the total power, and (c) the sideband power.
47. Draw the block diagram of an AM receiver circuit, label all the parts.
48. Instead of transmitting DSBFC, DSB is used with m=0.75. what is the percentage power saving of the system? If the carrier power is 10KW, what is radiated power of the system?
49. A 100KHz carrier is modulated by a 3KHz modulating signal and goes to the mixer with a local oscillator frequency of 1045KHz. What are the signals present at the output of the IF stage?
50. An AM receiver has an input signal of 5microvolts (rms). The antenna resistance is 50ohms, mixer power gain is 100, IF stage gain is 35dB, detector loss of 20dB, audio amplifier gain
of 30dB. How much power in dBm and in watts, enters the speaker?
51. Give the AM equation using the following parameters, Fc = 100KHz, fm = 3Khz, m=0.75 and Vc=10Vrms.
52. The frequency deviation of PM is dependent of what information signal’s parameter?
53. What is the simplest type of FM generator?54. How much guard band is used by FM broadcast system?55. How do you classify FM broadcast with a deviation ratio of
at least 1?56. In a FM receiver, what part of the system removes the noise?57. What parameter of a FM system is affected by the noise in
the signal?58. What is the process done in FM that boosts the high
frequency component of the signal?59. What system uses direct FM modulation with AFC to control
the carrier drift of the system?60. In a FM receiver, the recovery of the information signal is
done in what stage?61. A PLL is considered _________ during its capture state.62. What is the output frequency of a PLL when there is no input
signal at the input?63. What is the output parameter of a phase detector?64. What type of FM detector minimizes the used of limiters in
removing the noise?65. What FM parameter determines the number of sidebands
present in the system?66. This is a form of distortion resulting in a overdriven mixer
stage.
67. Draw the block diagram of a FM receiver. Label all the
blocks properly. 68. A FM system has a carrier voltage of 100Vrms, modulating
frequency of 10kHz and a deviation of 20KHz, what is the total transmitted power of the system if the antenna resistance is 10 ohms?
69. A FM system has a carrier frequency of 100MHz, operating at 80% modulation and contains 2 sideband pairs, if the carrier voltage is 120Vmax, give the FM equation of the system. A FM system has a carrier swing of 150KHz and a modulating frequency of 25KHz, draw the FM frequency spectrum.
70. In a FM system, the initial deviation is 10KHz, and the noise in the system is 25% of the signal’s intelligence voltage, what is the new SNR of the system?
Set C. Digital Encoding
1. In _______ encoding one amplitude represents a 1 bit and zero amplitude represents a 0 bit (or vice versa).
ans: unipolar
2. In _______ encoding positive and negative amplitudes represent the bits.
ans: polar
3. In _______ encoding positive, negative, and zero amplitudes represent the bits.
ans: bipolar
4. A digital signal has its 0 bits represented by 0 volts and its 1 bit represented by 5 volts. This is _______ encoding.
ans: unipolar
5. A digital signal has its 0 bits represented by 0 volts and its 1 bit represented by -5 volts or 5 volts. This is _______ encoding.
ans: bipolar
6. A digital signal has its 0 bits represented by -5 volts and its 1 bit represented by 5. This is _______ encoding.
ans: polar
7. The DC component is a serious problem for _______ encoding.
ans: unipolar
8. Unipolar encoding has a DC component because the average _______ of the signal is nonzero.
ans: amplitude
9. NRZ-L is a _______ encoding method.
ans: polar
10. NRZ-I is a _______ encoding method.
ans: polar
11. RZ is a _______ encoding method.
ans: polar
12. Manchester encoding is a _______ encoding method.
ans: polar
13. Differential Manchester encoding is a _______ encoding method.
ans: polar
14. AMI is a _______ encoding method.
ans: bipolar
15. _______ encoding is superior to _______ encoding because the problem of the DC component is alleviated.
ans: Polar; unipolar
16. Ethernet LANs use _______ encoding.
ans: Manchester
17. Token Ring LANs use _______ encoding.
ans: differential Manchester
18. In _______ encoding the transition between a positive and a negative voltage represents a 1 bit.
ans: NRZ-I
19. In _______ encoding halfway through each bit interval, the signal returns to zero.
ans: RZ
20. RZ encoding requires _______ signal change(s) to encode one bit.
ans: two
21. Manchester and differential Manchester encoding are both types of _______ encoding.
ans: biphase
22. In _______ conversion we are representing analog information as a series of 0s and 1s.
ans: analog-to-digital
23. In _______, an analog signal is sampled at equal intervals, with the resulting pulses still analog in value.
ans: PAM
24. In _______, the first step after PAM is quantization of the analog pulses.
ans: PCM
25. The _______ sampling rate is based on the Nyquist theorem.
ans: PAM
26. A sampling rate of _______ million samples per second is needed for a signal with components ranging from 10MHz to 100 MHz.
ans: 200 27. The process of changing one of the characteristics of a carrier
analog signal based on the information in a digital signal is called _______ conversion.
ans: digital-to-analog
28. In _______ the frequency of the carrier signal is varied based on the information in a digital signal.
ans: FSK
29. In _______ the amplitude of the carrier signal is varied based on the information in a digital signal.
ans: ASK
30. In _______ the phase of the carrier signal is varied based on the information in a digital signal.
ans: PSK
31. In _______ the phase and amplitude of the carrier signal is varied based on the information in a digital signal.
ans: QAM
32. Most modern modems use _______ for digital to analog modulation.
ans: QAM
33. _______ rate is the number of bits per second; _______ rate is the number of signal units per second.
ans: Bit; baud
34. _______ rate is always less than or equal to _______ rate.
ans: Baud; bit
35. If the bit rate is 1200 bps and there are 4 bits for each signal element, then the baud rate is _______.
ans: 300
36. If the baud rate is 1200 and there are 4 bits for each signal element, then the bit rate is _______.
ans: 4800
37. An ASK modulated signal has a bit rate of 2000 bps; the baud rate is _______.
ans: 2000
38. A 2-PSK modulated signal has a bit rate of 2000 bps; the baud rate is _______.
ans: 2000
39. A 4-PSK modulated signal has a bit rate of 2000 bps; the baud rate is _______.
ans: 1000
40. An 8-PSK modulated signal has a baud rate of 2000; the bit rate is _______ bps.
ans: 6000
41. An 8-QAM modulated signal has a baud rate of 2000; the bit rate is _______ bps.
ans: 6000
42. A 32-QAM modulated signal has a baud rate of 2000; the bit rate is _______ bps.
ans: 10000
43. A 128-QAM modulated signal has a baud rate of 2000; there are _______ bits per baud.
ans: 7 44. A 256-QAM modulated signal has a bit rate of 8000; there
are _______ bits per baud. ans: 8
45. OOK is a type of _______ modulation.
ans: ASK
46. The modulation technique most affected by noise is _______.
ans: ASK
47. For _______, the minimum bandwidth required for transmission is equal to the baud rate.
ans: a and b
48. The minimum bandwidth for an ASK modulated signal with a baud rate of 5000 is _______ Hz.
ans: 5000
49. On a 16-QAM-constellation diagram, each constellation point represents a _______.
ans: quadbit
50. In FM the _______ of the information signal modulates the frequency of the carrier signal.
ans: amplitude
51. In AM the _______ of the information signal modulates the amplitude of the carrier signal.
ans: amplitude
52. In PM the _______ of the information signal modulates the phase of the carrier signal.
ans: amplitude
53. In which type of modulation can the bit rate be four times the baud rate?
ans: PSK
54. In _______ modulation, the bit rate is 8 times the baud rate.
ans: 256-QAM
55. In a dibit modulation, the number of points in the constellation is _______.
ans: 4
56. In a tribit modulation, the number of points in the constellation is _______.
ans: 8
57. A 4-PSK constellation is a _________ modulation.
ans: dibit
58. An 8-QAM constellation is a _________ modulation.
ans: tribit
59. The number of points in the constellation of an 8-PSK modulation is _______ the number of points for an 8-QAM.
ans: equal to
60. If the baud rate for modulation scheme A is two times the baud rate for modulation scheme B, the required bandwidth for scheme A is ___________ the one for scheme B.
ans: more than
Set D. analog and digital communications1. ASK, PSK, FSK, and QAM are examples of ________conversion.A) digital-to-digitalB) digital-to-analogC) analog-to-analogD) analog-to-digital
2. AM and FM are examples of ________ conversion.A) digital-to-digitalB) digital-to-analogC) analog-to-analogD) analog-to-digital
3. In QAM, both ________ of a carrier frequency are varied.A) frequency and amplitudeB) phase and frequencyC) amplitude and phaseD) none of the above
4. If the baud rate is 400 for a QPSK signal, the bit rate is ________ bps.A) 100B) 400C) 800D) 1600
5. If the bit rate for an ASK signal is 1200 bps, the baud rate is ________.A) 300
B) 400C) 600D) 1200
6. If the bit rate for an FSK signal is 1200 bps, the baud rate is ________.A) 300B) 400C) 600D) 1200
7. If the bit rate for a 16-QAM signal is 4000 bps, what is the baud rate?A) 300B) 400C) 1000D) 1200
8. If the baud rate for a 64-QAM signal is 2000, what is the bit rate?A) 300B) 400C) 1000D) 12000
9. Given an AM radio signal with a bandwidth of 10 KHz and the highest-frequency component at 705 KHz, what is the frequency of the carrier signal?A) 700 KHzB) 705 KHzC) 710 KHzD) Cannot be determined from given information
10. _______ conversion is the process of changing one of the characteristics of an analog signal based on the information in the digital data.A) Digital-to-analogB) Analog-to-analogC) Analog-to-digitalD) Digital-to-digital
11. Which of the following is not a digital-to-analog conversion?A) ASKB) PSKC) FSKD) AM
12. In ________, the amplitude of the carrier signal is varied to create signal elements. Both frequency and phase remain constant.A) ASKB) PSKC) FSKD) QAM
13. In _________, the frequency of the carrier signal is varied to represent data. Both peak amplitude and phase remain constant.A) ASKB) PSKC) FSKD) QAM
14. In ________, the phase of the carrier is varied to represent two or more different signal elements. Both peak amplitude and frequency remain constant.A) ASKB) PSKC) FSKD) QAM
15. A constellation diagram shows us the __________ of a signal element, particularly when we are using two carriers (one in-phase and one quadrature).A) amplitude and phaseB) amplitude and frequencyC) frequency and phaseD) none of the above
16. Quadrature amplitude modulation (QAM) is a combination of ___________.A) ASK and FSKB) ASK and PSKC) PSK and FSKD) none of the above
17. ________ uses two carriers, one in-phase and the other quadrature.A) ASKB) PSKC) FSKD) QAM
18. _________ conversion is the representation of analog information by an analog signal.A) Digital-to-analogB) Analog-to-analogC) Analog-to-digitalD) Digital-to-digital
19. Analog-to-analog conversion is needed if the available bandwidth is _______.A) low-passB) band-passC) either (a) or (b)D) neither (a) nor (b)
20. Which of the following is not an analog-to-analog conversion?A) AMB) PMC) FMD) QAM
21. In _____ transmission, the carrier signal is modulated so that its amplitude varies with the changing amplitudes of the modulating signal.A) AMB) PMC) FMD) none of the above
22. In _____ transmission, the frequency of the carrier signal is modulated to follow the changing voltage level (amplitude) of the modulating signal. The peak amplitude and phase of the carrier signal remain constant, but as the amplitude of the information signal changes, the frequency of the carrier changes correspondingly.A) AMB) PMC) FMD) none of the above
23. In _____ transmission, the phase of the carrier signal is modulated to follow the changing voltage level (amplitude) of the modulating signal.A) AMB) PMC) FMD) none of the above
24. In _______, the peak amplitude of one signal level is 0; the other is the same as the amplitude of the carrier frequency.A) PSKB) OOKC) FSK
D) none of the above
25. How many carrier frequencies are used in BASK?A) 2B) 1C) 0D) none of the above
26. How many carrier frequencies are used in BFSK?A) 2B) 1C) 0D) none of the above
27. How many carrier frequencies are used in BPSK?A) 2B) 1C) 0D) none of the above
28. How many carrier frequencies are used in QPSK?A) 2B) 1C) 0D) none of the above
29. The constellation diagram of BASK has ______ dots.A) 2B) 1
C) 0D) none of the above
30. The constellation diagram of BPSK has ______ dots.A) 2B) 1C) 0D) none of the above
31. The constellation diagram of QPSK has ______ dots.A) 2B) 1C) 4D) none of the above
32. The constellation diagram of 16-QAM has ______ dots.A) 4B) 16C) 8D) none of the above
33. The Federal Communications Commission (FCC) allows ______kHz for each AM station.A) 5B) 10C) 20D) none of the above
34. The Federal Communications Commission (FCC) allows ______ kHz for each FM station.A) 20B) 100C) 200D) none of the above
