CHAPTER 1: INTRODUCTION TO COMMUNICATION SYSTEMS
CHAPTER 1: INTRODUCTION TO COMMUNICATION SYSTEMS
1.
1. It moves information from a source to It moves information from a source to a destination through aa destination through a channel.
channel.
Communication System Communication System
2.
2. Elements of a communication systemElements of a communication system Source, Transmitter, Channel,Source, Transmitter, Channel, Receiver, Destination Receiver, Destination 3.
3. Three essential elements of any communication systemThree essential elements of any communication system Transmitter, Receiver, ChannelTransmitter, Receiver, Channel 4.
4. Sources of information signalsSources of information signals Analog and Digital Analog and Digital 5.
5. Sources are often described in terms of the ___________Sources are often described in terms of the ___________ ________ that they occupy
________ that they occupy
Frequency Range Frequency Range
6.
6. The element of a communication system wherein tThe element of a communication system wherein the signalhe signal will be driven out of the source to the channel.
will be driven out of the source to the channel.
Transmitter Transmitter
7.
7. This element of communication system can be a pair ofThis element of communication system can be a pair of conductors or an optical fiber or
conductors or an optical fiber or the free space wherein thethe free space wherein the signal is traveling to the receiver
signal is traveling to the receiver
Channel Channel
8.
8. In a free space channel, ______ signal is required to avoidIn a free space channel, ______ signal is required to avoid interference.
interference.
Carrier Carrier
9.
9. When a carrier is used, the information signal can be alsoWhen a carrier is used, the information signal can be also called as __________ ______.
called as __________ ______.
Modulating Signal Modulating Signal
10.
10. Since the carrier frequency is generally much Since the carrier frequency is generally much higher than thathigher than that of the information signal, the frequency spectrum of
of the information signal, the frequency spectrum of thethe information signal is often referred to as _________. information signal is often referred to as _________.
Baseband Baseband
11.
11. Modulation is done at the _______.Modulation is done at the _______. TransmitterTransmitter 12.
12. This process takes place at the This process takes place at the receiver wherein the signal hasreceiver wherein the signal has to be restored to its original
to be restored to its original baseband signal.baseband signal. DemodulationDemodulation 13.
13. It states that the amount of It states that the amount of information that can beinformation that can be transmitted in a given time is
transmitted in a given time is proportional to bandwidth for aproportional to bandwidth for a given modulating scheme..
given modulating scheme..
Hartley’s Law Hartley’s Law
14.
14. It refers to the combining of two or more information signals.It refers to the combining of two or more information signals. MultiplexingMultiplexing 15.
15. Methods of multiplexing.Methods of multiplexing. Frequency-Division Multiplexing,Frequency-Division Multiplexing, Time-Division Multiplexing Time-Division Multiplexing 16.
16. When the available frequency is divided among the When the available frequency is divided among the signals, thesignals, the process is known as ______________ _________.
process is known as ______________ _________. Frequency-division MultiplexingFrequency-division Multiplexing
17.
17. In this process, the entire bandwidth is used for each signal,In this process, the entire bandwidth is used for each signal, but only for a small part of time.
18.
18. It is the available bandwidth of a It is the available bandwidth of a communication satellitecommunication satellite divided among a number of transmitter-receiver combinations.
divided among a number of transmitter-receiver combinations. TransponderTransponder 19.
19. It is any undesirable change in It is any undesirable change in an information signal.an information signal. DistortionDistortion 20.
20. A representation of a sig A representation of a signal’s power or amplitude as a fnal’s power or amplitude as a functionunction of frequency.
of frequency. Frequency DomainFrequency Domain 21.
21. A way of representing th A way of representing the periodic functions as a series ofe periodic functions as a series of sinusoids.
sinusoids. Fourier SeriesFourier Series 22.
22. Any undesired disturbance that Any undesired disturbance that is superimposed on a signal andis superimposed on a signal and obscures its information content
obscures its information content NoiseNoise 23.
23. Noise which originates within the communication equipment.Noise which originates within the communication equipment. Internal NoiseInternal Noise 24.
24. Noise outside the communication equipment.Noise outside the communication equipment. External NoiseExternal Noise 25.
25. Noise generated by equipment that produces sparks.Noise generated by equipment that produces sparks. Equipment NoiseEquipment Noise 26.
26. Noise that is originated from lightning.Noise that is originated from lightning. Atmospheric Noise Atmospheric Noise 27.
27. Refer to no. 28: another name for this kind of noiseRefer to no. 28: another name for this kind of noise StaticStatic 28.
28. Noise that comes from heavenly bodies that Noise that comes from heavenly bodies that are powerfulare powerful sources of radiation.
sources of radiation. Space NoiseSpace Noise 29.
29. This noise is produced by the random motion of electrons in aThis noise is produced by the random motion of electrons in a conductor due to heat.
conductor due to heat. Thermal NoiseThermal Noise 30.
30. This is due to random variations in current flow in activeThis is due to random variations in current flow in active devices such as tubes, transistors, and semiconductor diodes.
devices such as tubes, transistors, and semiconductor diodes. Shot NoiseShot Noise 31.
31. Noise that occurs in the Noise that occurs in the partition of the Negative and Ppartition of the Negative and Positiveositive elements in a semiconductor such as BJT.
elements in a semiconductor such as BJT. Partition NoisePartition Noise 32.
32. This noise is cause by variations in carrier density.This noise is cause by variations in carrier density. Excess NoiseExcess Noise 33.
33. Refer to no. 34: another name for it.Refer to no. 34: another name for it. Flicker Noise, Pink NoiseFlicker Noise, Pink Noise 34.
34. Noise that many junction devices produce due to cut-offNoise that many junction devices produce due to cut-off frequency reaching.
frequency reaching. Transit-Time NoiseTransit-Time Noise 35.
35. ratio of signal to noise power at a given point in a system.ratio of signal to noise power at a given point in a system. Signal-to-Noise RatioSignal-to-Noise Ratio 36.
36. Device for displaying signals in the frequency domain.Device for displaying signals in the frequency domain. Spectrum AnalyzerSpectrum Analyzer 37.
37. It is a figure to merit, indicating how much a component,It is a figure to merit, indicating how much a component, stage, or series of stages degrades the signal-to-noise
stage, or series of stages degrades the signal-to-noise ratio of aratio of a system.
system.
Noise Figure Noise Figure
38.
38. Refer to no. 39: Another name for that.Refer to no. 39: Another name for that. Noise FactorNoise Factor 39.
39. It is the absolute temperature of a resistor that, It is the absolute temperature of a resistor that, connected toconnected to the input of a noiseless amplifier of the same gain, would the input of a noiseless amplifier of the same gain, would produce the same noise at the output.
produce the same noise at the output.
Equivalent Noise Temperature Equivalent Noise Temperature
40.
18.
18. It is the available bandwidth of a It is the available bandwidth of a communication satellitecommunication satellite divided among a number of transmitter-receiver combinations.
divided among a number of transmitter-receiver combinations. TransponderTransponder 19.
19. It is any undesirable change in It is any undesirable change in an information signal.an information signal. DistortionDistortion 20.
20. A representation of a sig A representation of a signal’s power or amplitude as a fnal’s power or amplitude as a functionunction of frequency.
of frequency. Frequency DomainFrequency Domain 21.
21. A way of representing th A way of representing the periodic functions as a series ofe periodic functions as a series of sinusoids.
sinusoids. Fourier SeriesFourier Series 22.
22. Any undesired disturbance that Any undesired disturbance that is superimposed on a signal andis superimposed on a signal and obscures its information content
obscures its information content NoiseNoise 23.
23. Noise which originates within the communication equipment.Noise which originates within the communication equipment. Internal NoiseInternal Noise 24.
24. Noise outside the communication equipment.Noise outside the communication equipment. External NoiseExternal Noise 25.
25. Noise generated by equipment that produces sparks.Noise generated by equipment that produces sparks. Equipment NoiseEquipment Noise 26.
26. Noise that is originated from lightning.Noise that is originated from lightning. Atmospheric Noise Atmospheric Noise 27.
27. Refer to no. 28: another name for this kind of noiseRefer to no. 28: another name for this kind of noise StaticStatic 28.
28. Noise that comes from heavenly bodies that Noise that comes from heavenly bodies that are powerfulare powerful sources of radiation.
sources of radiation. Space NoiseSpace Noise 29.
29. This noise is produced by the random motion of electrons in aThis noise is produced by the random motion of electrons in a conductor due to heat.
conductor due to heat. Thermal NoiseThermal Noise 30.
30. This is due to random variations in current flow in activeThis is due to random variations in current flow in active devices such as tubes, transistors, and semiconductor diodes.
devices such as tubes, transistors, and semiconductor diodes. Shot NoiseShot Noise 31.
31. Noise that occurs in the Noise that occurs in the partition of the Negative and Ppartition of the Negative and Positiveositive elements in a semiconductor such as BJT.
elements in a semiconductor such as BJT. Partition NoisePartition Noise 32.
32. This noise is cause by variations in carrier density.This noise is cause by variations in carrier density. Excess NoiseExcess Noise 33.
33. Refer to no. 34: another name for it.Refer to no. 34: another name for it. Flicker Noise, Pink NoiseFlicker Noise, Pink Noise 34.
34. Noise that many junction devices produce due to cut-offNoise that many junction devices produce due to cut-off frequency reaching.
frequency reaching. Transit-Time NoiseTransit-Time Noise 35.
35. ratio of signal to noise power at a given point in a system.ratio of signal to noise power at a given point in a system. Signal-to-Noise RatioSignal-to-Noise Ratio 36.
36. Device for displaying signals in the frequency domain.Device for displaying signals in the frequency domain. Spectrum AnalyzerSpectrum Analyzer 37.
37. It is a figure to merit, indicating how much a component,It is a figure to merit, indicating how much a component, stage, or series of stages degrades the signal-to-noise
stage, or series of stages degrades the signal-to-noise ratio of aratio of a system.
system.
Noise Figure Noise Figure
38.
38. Refer to no. 39: Another name for that.Refer to no. 39: Another name for that. Noise FactorNoise Factor 39.
39. It is the absolute temperature of a resistor that, It is the absolute temperature of a resistor that, connected toconnected to the input of a noiseless amplifier of the same gain, would the input of a noiseless amplifier of the same gain, would produce the same noise at the output.
produce the same noise at the output.
Equivalent Noise Temperature Equivalent Noise Temperature
40.
CHAPTER 2: RADIO FREQUENCY CIRCUITS
CHAPTER 2: RADIO FREQUENCY CIRCUITS
1.
1. A mixer in which the input frequenc A mixer in which the input frequencies are cancelled and areies are cancelled and are therefore not present at the output.
therefore not present at the output. Balanced MixerBalanced Mixer 2.
2. Removal of an unwanted signal by providing a Removal of an unwanted signal by providing a low-impedancelow-impedance path to ground.
path to ground. BypassingBypassing 3.
3. The total frequency range over which a The total frequency range over which a PLL can become lockedPLL can become locked to a signal.
to a signal. Capture RangeCapture Range 4.
4. A small stab of quartz w A small stab of quartz with attached electrodes; used as aith attached electrodes; used as a resonant circuit.
resonant circuit. CrystalCrystal
5.
5. It is to prevent the undesired It is to prevent the undesired passage of signals betweenpassage of signals between circuits.
circuits. DecoupleDecouple
6.
6. A frequency multiplier whose outp A frequency multiplier whose output frequency is twice that ofut frequency is twice that of the input signal.
the input signal. DoublerDoubler
7.
7. The frequency at which a VCO operates when its controlThe frequency at which a VCO operates when its control voltage is zero.
voltage is zero. Free-running FrequencyFree-running Frequency 8.
8. A circuit whose output frequency i A circuit whose output frequency is a small integer multiple ofs a small integer multiple of the input signal frequency.
the input signal frequency. Frequency MultiplierFrequency Multiplier 9.
9. A device that can produce a larg A device that can produce a large number of outpute number of output frequencies from a smaller number of fixed-frequency frequencies from a smaller number of fixed-frequency oscillators.
oscillators.
Frequency Synthesizer Frequency Synthesizer
10.
10. Movement of a signal from one frequency to another using aMovement of a signal from one frequency to another using a mixer-oscillator synthesizer.
mixer-oscillator synthesizer. Frequency TranslationFrequency Translation 11.
11. A small length of wire, connected at A small length of wire, connected at only one end as aonly one end as a capacitance to ground.
capacitance to ground. GimmickGimmick 12.
12. An artificial ground, often cons An artificial ground, often consisting of an area foil left on oneisting of an area foil left on one side of a circuit board.
side of a circuit board. Ground PlaneGround Plane 13.
13. Total range of frequencies over which a PLL, once locked, canTotal range of frequencies over which a PLL, once locked, can remain locked.
remain locked. Lock RangeLock Range 14.
14. This effect is in some This effect is in some amplifiers that the internal capacitance ofamplifiers that the internal capacitance of the active device can cause feedback that
the active device can cause feedback that produces the sameproduces the same effect on the circuit as muc
effect on the circuit as much larger capacitance across theh larger capacitance across the amplifier input.
amplifier input.
Miller Effect Miller Effect
15.
15. A nonlinear circuit designed to gener A nonlinear circuit designed to generate sum and differenceate sum and difference frequencies when two or more frequencies are
frequencies when two or more frequencies are present at itspresent at its inputs.
inputs.
Mixer Mixer
16. The number by which a digital divider chain divides.
Modulus 17. A circuit whose output is proportional to the product of the
instantaneous amplitudes of two input signals. Multiplier 18. A means of avoiding instability in amplifiers by using negative
feedback. Neutralization
19. A device whose output voltage is a function of the phase
difference between two input signals. Phase Detector 20. A device that locks the frequency of a VCO exactly to that of an
input signal. Phase-locked Loop (PLL)
21. An effect that occurs in some materials, such as quartz and some ceramics, whereby a voltage is produced across the material when it is deformed.
Piezoelectric Effect
22. A divider that precedes the main programmable divider in a
frequency synthesizer. Prescaler
23. In a frequency synthesizer, it is the smallest amount by which
the output frequency can be changed. Resolution 24. The frequency at which a single component becomes a
resonant circuit, because the presence of stray capacitance or inductance, or both.
Self-Resonant Frequency
25. A frequency multiplier whose output frequency is three times
that of the input signal. Tripler
26. A reverse-biased diode used as a voltage, variable capacitor. Varactor 27. An oscillator whose frequency can be controlled by changing
external control voltage.
Voltage-Controlled Oscillator (VCO)
28. This oscillator type can be recognized by its use of a tapped
inductor, part of the resonant circuit, to provide feedback. Hartley Oscillator 29. It’s an oscillator that uses capacitive voltage divider instead of a
tapped inductor to provide feedback. Colpitts Oscillator 30. It is a variation of Colpitts circuit, designed to swamp device
capacitances for greater stability. Clapp Oscillator 31. This is typically tuned by moving a ferrite core into or out of
CHAPTER 3: AMPLITUDE MODULATION
1. A modulation scheme in which the amplitude of a
high-frequency signal is varied in accordance with t he instantaneous amplitude of an information signal.
Amplitude Modulation (AM)
2. The curve produced by joining the tips of the individual RF
cycles of a modulated wave Envelope 3. Measure of the extent of the modulation of a signal. Modulation Index 4. Modulation of a greater depth than allowed. Over modulation 5. The power measured at modulation peaks in an AM or
single-sideband signal. Peak Envelope Power (PEP) 6. Transmission of two separate information signals using two
amplitude-modulated carriers at the same frequency but differing in phase by 90 degrees.
Quadrature AM
7. A signal component in a modulated signal, at a frequency
different from that of a carrier. Side Frequency 8. All of the side frequencies to one side of the carrier frequency. Sideband 9. Any AM scheme in which only one of the two sidebands is
transmitted. Single-sideband
10. An AM signal in which the carrier frequency component is
eliminated and only one or both sidebands are transmitted. Suppressed-carrier Signal 11. It is a colloquial term used to describe additional side
frequencies produced by over modulation or distortion in an AM system.
Splatter
12. A signal consisting of two audio frequencies, not harmonically
related, used to test single-sideband transmitters. Two-tone Test Signal 13. The higher-frequency signal that is combined with an
information signal to produce the modulated waveform is called ________.
CHAPTER 4: ANGLE MODULATION
1. A general term that includes frequency and phase modulation. Angle Modulation 2. It is the ability of an FM receiver to receive the stronger of two
signals, ignoring the weaker. Capture Effect 3. The frequency of a signal before modulation is applied and the
power transmitted at the carrier frequency varies with modulation for an FM signal.
Carrier Frequency
4. It is the use of low-pass filter in a receiver to remove the effect
of pre-emphasis on the frequency response. De-emphasis 5. The amount by which the frequency of an FM signal shifts to
each side of the carrier frequency. Frequency Deviation 6. IN FM and PM, the peak amount in radians by which the phase
of a signal deviates from its resting value. Modulation Index 7. Fm with relatively low modulation index. Narrowband FM (NBFM) 8. It is the use of a high pass filter in an FM transmitter to
improve the signaltonoise ration; always used with de -emphasis at the receiver.
Pre-emphasis
9. It is the frequency of the unmodulated carrier of an FM signal. Rest Frequency 10. Refer to no. 9: Another name for it. Carrier Frequency 11. A secondary carrier that can carry an additional modulating
signal and is itself modulated onto the main carrier. Subcarrier 12. It is the noise-reduction effect that occurs with strong FM
signals. Threshold Effect
13. FM with a relatively large modulation index. Wideband FM (WBFM) 14. This represents normalized voltages for the various frequency
components of an FM or PM signal. Bessel Functions Table
ADDITIONAL NOTES: FM and PM 1. A type of angle modulation wherein the frequency is varied
relative to the modulating frequency. Frequency Modulation 2. It is the amount by which the frequency varies from its
unmodulated value. Frequency Deviation 3. The total Variation in frequency. Carrier Swing 4. It is the ratio of the actual deviation to the maximum
deviation multiplied by 100%. Percentage of Modulation 5. In AM, P total is variable while in FM P total is _____. Constant
6. It is the boosting of the higher modulating frequencies at
improve noise immunity at FM.
7. The cutting of the higher modulating frequencies at the
receiver. De-emphasis
8. Forms of interference in FM.
Image Frequency, Co-channel interference,
Adjacent channel 9. it is an effect of two stations being received simultaneously. Image Frequency 10. It happens usually to mobile receivers when they travel
from one transmitter to the other. Co-channel Interference 11. It is the modulation wherein the phase of the carrier is
made proportional to the instantaneous value of the modulating signal.
Phase Modulation 12. FM and Pm are indistinguishable for a single ______
________. Modulating frequency
13. When modulating frequency is changed, PM m odulation
index ______ _______. Remains constant 14. It is the process by which the modulating signal is
recovered from the modulated carrier, definitely found in receivers.
Demodulation 15. It has the function of selecting the desired signal from all
the other unwanted signals, amplifying and demodulating it, and displaying it in the desired manner.
Receiver
16. Two types of receivers. Tuned Radio Frequency, Superheterodyne Receiver 17. Characteristics of a tuned radio frequency receiver.
Simple logical receiver, Simplicity and high sensitivity, Align at broadcast frequencies
535-1640 kHz 18. It is the ability to amplify weak signals. Sensitivity 19. It is the ability to reject unwanted signals. Selectivity 20. It is the ratio of gain at desired frequency to the gain of
image frequency signal. Image Rejection Ratio
CHAPTER 5: TRANSMITTERS
1. A scheme for keeping a transmitter or receiver tuned to the correct frequency.
Automatic Frequency Control (AFC)
2. A circuit for keeping the amplitude of a signal within
prescribed limits. Automatic-level-control Circuit 3. An amplifier stage used to isolate two other stages from
each other. Buffer
4. Change of carrier amplitude with modulation in an AM
transmitter. Carrier Shift
for higher-level signals. for higher-level signals. 6.
6. Any system that generates FM w Any system that generates FM without using phaseithout using phase modulation.
modulation. Direct FMDirect FM
7.
7. A device that allows a signal mov A device that allows a signal moving along a transmissioning along a transmission line in one direction to be measured.
line in one direction to be measured. Directional CouplerDirectional Coupler 8.
8. An amplifier which supplies the req An amplifier which supplies the required input signal poweruired input signal power for a power amplifier.
for a power amplifier. DriverDriver 9.
9. A noninductive power resistor used A noninductive power resistor used to simulate an antenna.to simulate an antenna. Dummy LoadDummy Load 10.
10. It is a ratio of time on to total time.It is a ratio of time on to total time. Duty CycleDuty Cycle 11.
11. It is the ratio between largest and It is the ratio between largest and smallest signals at asmallest signals at a point in a system.
point in a system. Dynamic RangeDynamic Range 12.
12. The part of the transmitter that operates at The part of the transmitter that operates at low powerlow power levels.
levels. ExciterExciter
13.
13. It is the ability of a transmitter to tune rapidly from oneIt is the ability of a transmitter to tune rapidly from one operation frequency to another.
operation frequency to another. Frequency AgilityFrequency Agility 14.
14. Amplitude modulation of the output el Amplitude modulation of the output element of the outputement of the output stage of a transmitter.
stage of a transmitter. High-level ModulationHigh-level Modulation 15.
15. Any method that generates FM u Any method that generates FM using a phase modulatorsing a phase modulator and an integrator.
and an integrator. Indirect FMIndirect FM 16.
16. Transmitter power amplifier stage immediately before theTransmitter power amplifier stage immediately before the output stage.
output stage. Low-level ModulationLow-level Modulation 17.
17. An oscillator whose frequency is con An oscillator whose frequency is controlled by a binarytrolled by a binary number written to an internal register.
number written to an internal register. Numerically-controlled OscillatorNumerically-controlled Oscillator 18.
18. Ratio of the power output of a device to the total powerRatio of the power output of a device to the total power required from its power supply.
required from its power supply. Overall EfficiencyOverall Efficiency 19.
19. It is the absence of spurious signals in the output of aIt is the absence of spurious signals in the output of a transmitter.
transmitter. Spectral PuritySpectral Purity 20.
20. An emission from a transmitter other An emission from a transmitter other than the carrier andthan the carrier and sidebands required by the modulation scheme in use.
sidebands required by the modulation scheme in use. Spurious SignalSpurious Signal 21.
21. Importance of transmitter efficiency.Importance of transmitter efficiency. Maximum energy conversion,Maximum energy conversion, reasonable cost efficiency reasonable cost efficiency
CHAPTER 6: RECEIVERS
CHAPTER 6: RECEIVERS
1.
1. The communications channel immediately above or belowThe communications channel immediately above or below the desired channel in frequency.
the desired channel in frequency. Adjacent Channel Adjacent Channel 2.
2. The next communications channel beyond tThe next communications channel beyond the adjacenthe adjacent channel.
channel. Alternate Channel Alternate Channel 3.
3. A combined mixer and local oscillat A combined mixer and local oscillator that uses oneor that uses one transistor or tube for both.
transistor or tube for both. Autodyne Converter Autodyne Converter 4.
4. A circuit to adjust the gain of a syste A circuit to adjust the gain of a system in accordance withm in accordance with the input signal strength.
the input signal strength. Automatic Gain Control (AGC Automatic Gain Control (AGC)) 5.
5. Reduction of gain for a weak signal due to a strong signalReduction of gain for a weak signal due to a strong signal close to it in frequency.
close to it in frequency. BlockingBlocking 6.
6. A bandpass filter using piezoelec A bandpass filter using piezoelectric ceramic elements.tric ceramic elements. Ceramic FilterCeramic Filter 7.
7. A combination of a mixer and a loc A combination of a mixer and a local oscillator that is usedal oscillator that is used to move a signal from one frequency to another.
to move a signal from one frequency to another. ConverterConverter 8.
8. a bandpass filter that uses piezoelectric quartz element.a bandpass filter that uses piezoelectric quartz element. Crystal FilterCrystal Filter 9.
9. Circuit to recover the baseband signal from a Circuit to recover the baseband signal from a modulatedmodulated signal.
signal. DemodulatorDemodulator
10.
10. It is a specialized microprocessor designed to performIt is a specialized microprocessor designed to perform arithmetic operations on digitized communication signals.
arithmetic operations on digitized communication signals. Digital Signal ProcessorDigital Signal Processor 11.
11. Any detector for FM or Pm sig Any detector for FM or Pm signals.nals. DiscriminatorDiscriminator 12.
12. An AM demodulator that works by r An AM demodulator that works by rectifying the signal andectifying the signal and low-pass filtering the result.
low-pass filtering the result. Envelop DetectorEnvelop Detector 13.
13. The first stage of a receiver.The first stage of a receiver. Front EndFront End 14.
14. It is the application to a mixer of a signal from a localIt is the application to a mixer of a signal from a local oscillator that operates at a frequency above that of oscillator that operates at a frequency above that of thethe incoming signal.
incoming signal.
High-side Injection High-side Injection
15.
15. In a frequency converter, it is a second input frequencyIn a frequency converter, it is a second input frequency that produces the same output frequency.
that produces the same output frequency. Image FrequencyImage Frequency 16.
16. A frequency to which a signal is shif A frequency to which a signal is shifted as an intermediateted as an intermediate step in reception or transmission
step in reception or transmission Intermediate Frequency (IF)Intermediate Frequency (IF) 17.
17. An oscillator used in conjunction with a mixer An oscillator used in conjunction with a mixer to shift ato shift a signal to a different frequency.
signal to a different frequency. Local OscillatorLocal Oscillator 18.
18. Application to a mixer of a signa Application to a mixer of a signal from a local oscillator thatl from a local oscillator that operates at a frequency below that of the incoming signal.
operates at a frequency below that of the incoming signal. Low-side InjectionLow-side Injection 19.
20.
20. Low-level carrier signal transmitted to Low-level carrier signal transmitted to facilitatefacilitate regeneration of the carrier at the receiver.
regeneration of the carrier at the receiver. Pilot CarrierPilot Carrier 21.
21. A detector for suppressed-carrier A detector for suppressed-carrier AM signals that works byAM signals that works by multiplying the signal with a
multiplying the signal with a regenerated carrier.regenerated carrier. Product DetectorProduct Detector 22.
22. The strength of an unmodulated The strength of an unmodulated carrier that reduces thecarrier that reduces the noise output of an AM receiver by a specified amount.
noise output of an AM receiver by a specified amount. Quieting SensitivityQuieting Sensitivity 23.
23. FM detector that is based on a 90-degree phase shiftFM detector that is based on a 90-degree phase shift network.
network. Quadrature DetectorQuadrature Detector 24.
24. FM detector.FM detector. Ratio DetectorRatio Detector 25.
25. It is the ratio of signal-plus-noise and distortion to noise-It is the ratio of signal-plus-noise and distortion to noise-plus-distortion.
plus-distortion. SINADSINAD
26.
26. A meter on a receiver that ind A meter on a receiver that indicates the strength of theicates the strength of the received signal.
received signal. S-meterS-meter
27.
27. The ability of a receiver to The ability of a receiver to reject signals of frequenciesreject signals of frequencies other than the frequency to which the receiver is tuned.
other than the frequency to which the receiver is tuned. SelectivitySelectivity 28.
28. The ability of a receiver to The ability of a receiver to receive weak signals with areceive weak signals with a satisfactory signal-to-noise ratio.
satisfactory signal-to-noise ratio. SensitivitySensitivity 29.
29. For a bandpass filter, it is For a bandpass filter, it is the ratio between the bandwidthsthe ratio between the bandwidths for two specified amounts of attenuation.
for two specified amounts of attenuation. Shape FactorShape Factor 30.
30. It is the reduction in effective cross-sectional area of aIt is the reduction in effective cross-sectional area of a conductor with increasing frequency.
conductor with increasing frequency. Skin EffectSkin Effect 31.
31. It is the reception of signals at frequencies other than thatIt is the reception of signals at frequencies other than that to which the receiver is tuned.
to which the receiver is tuned. Spurious ResponseSpurious Response 32.
32. A system that disables the outp A system that disables the output of a receiver in theut of a receiver in the absence of a suitable signal.
absence of a suitable signal. SquelchSquelch 33.
33. It is a receiver in which the signal is moved, using a mixer,It is a receiver in which the signal is moved, using a mixer, to an intermediate frequency before demodulation.
to an intermediate frequency before demodulation. Superheterodyne ReceiverSuperheterodyne Receiver 34.
34. The filter that uses acoustic waves on the surface of aThe filter that uses acoustic waves on the surface of a substrate to achieve the desired response.
substrate to achieve the desired response. Surface-Acoustic Wave FilterSurface-Acoustic Wave Filter 35.
35. It is the adjustment of two or more tuned circuits so thatIt is the adjustment of two or more tuned circuits so that they can be tuned simultaneously with one adjustment.
they can be tuned simultaneously with one adjustment. TrackingTracking 36.
36. It is a receiver in which the signal is amplified at its originalIt is a receiver in which the signal is amplified at its original frequency before demodulation.
frequency before demodulation.
Tuned-radio-frequency (TRF) Tuned-radio-frequency (TRF)
Receiver Receiver 37.
37. The Fm signal strength with The Fm signal strength with defined deviation, required todefined deviation, required to produce a specified SINAD in the receiver.
CHAPTER 7: DIGITAL COMMUNICATIONS
1. Distortion created by using too low a sampling rate when
coding an analog signal for digital transmission. Aliasing 2. A data code that uses both polarities of voltage and
current. Bipolar Code
3. Device that converts sampled analog signal to and from its
PCM or delta modulation equivalent. Coder-decoder (codec) 4. Conversion of sampled analog signal into a PCM or delta
modulation bitstream. Coding
5. Combination of compression at the transmitter and
expansion at the receiver of communication system. Companding 6. Amplification of a signal in such a way that there is less
gain for higher-level input signals than for lower-level input signals.
Compression
7. Conversion of a PCM or delta modulation bitsream to
analog samples. Decoding
8. A coding scheme that records the change in signal level
since the previous sample. Delta Modulation
9. It is filtering of signals by converting them to digital form. Digital Signal Processing (DSP) 10. Sampling of an analog signal using a sample-and-hold
circuit. Flat-topped Sampling
11. Another name for aliasing. Foldover Distortion 12. These are bits added to a digital signal to help the receiver
detect the beginning and end of data frames. Framing Bits 13. A system for translating logic ones and zeros into voltage
or current levels for transmission. Line Code 14. Sampling of an analog signal to know if it follows the
original signal for the duration of the sample. Natural Sampling 15. A logic system in which a low level represents logic one and
a high level represents logic zero. Negative Logic 16. A data line code in which the voltage or current does not
necessarily return to zero between bits. Non-return-to-zero Code (NRZ) 17. A logic system in which a high level represents logic one
18. A series of pulses in which the amplitude of each pulse represents the amplitude of the information signal at a given time.
Pulse-amplitude Modulation (PAM)
19. A series of pulses in which the amplitude of the information
signal at a given time is coded as a binary number. Pulse-code Modulation (PCM) 20. A series of pulses in which the duration of each pulse
represents the amplitude of the information signal at a given time.
Pulse-duration Modulation (PDM)
21. A series of pulses in which the timing of each pulse represents the amplitude of the information signal at a given time.
Pulse-position Modulation (PPM)
22. Another name for pulse-duration modulation. Pulse-width Modulation (PWM) 23. Representation of a continuously varying quantity as one of
a number of discrete values. Quantizing 24. Inaccuracies caused by the representation of continuously
varying quantity as one of a number of discrete values. Quantizing Errors 25. Refer to no. 24: Another name for it. Quantizing Noise 26. A device that decodes and recodes a digital signal as well
as amplifying it. Regenerative Repeater 27. Method of data compression by encoding the length of a
string of ones and zeroes. Run-length Encoding 28. A line code in which the voltage or current returns to zero
at the end of each bit period. Return-to-zero Code (RZ) 29. A device that detects the amplitude of an input signal at a
particular time. Sample-and-hold Circuit 30. It is an error condition that occurs when the analog signal
to be digitized varies too quickly for the system to follow. Slope Overload 31. A line code in which the polarity of the voltage remains the
same at all times. Unipolar Code
32. It is a circuit for digitizing voice at a low data rate. Vocoder 33. Modern communication systems are often a mixture of
_______ and _________ sources and transmission techniques.
Analog, Digital 34. _________ _________ ______ have better performance
and use less bandwidth than equivalent analog systems. Modern Digital Systems 35. It requires that the amplitude of each sample of a signal be PCM
converted to a binary number.
36. It transmits only one bit per sample. Delta Modulation 37. The S/N ratio for either PCM or delta modulation signals
can often be improved by using __________. Companding 38. It eliminates redundant data bits. Lossless Compression 39. It compromises signal quality in order to reduce the bit
rate. Lossy Compression
40. It is a combination of modulation and demodulation. Modem 41. He showed mathematically that it is impossible to
reconstruct a band-limited analog signal from periodic samples.
Harry Nyquist
42. It provides strong timing information regardless of the
pattern of ones and zeros. Manchester Code 43. Manchester code is also a type of _________ _________. Biphase Code
44. In RZ coding, the system used in telephony is _________. Alternate Mark Inversion (AMI) 45. It states that the amount of information transmitted is
proportional to both bandwidth and time. Hartley’s Law 46. It is used mainly for digital communication. TDM
CHAPTER 8: THE TELEPHONE SYSTEM
1. An area consisting of several central offices and handled by a local carrier.
Local Access and Transport Area (LATA)
2. The link from the central office to an individual
subscriber’s premises. Local Loop 3. It is the method of providing high-speed data
transmission on twisted-pair telephone loops by using high-frequency carriers.
Asymmetrical Digital Subscriber Line (ADSL)
4. In ISDN, these are channels that carry subscriber
communication. Bearer Channels
5. Described as the used of bits that normally carry payload information for other purposes such as controlling the communication system.
Bit Robbing
6. It is addition of bits to a bitstream to compensate for
7. It is the failure to connect a telephone call because of
lack of system capacity. Call Blocking 8. Switch in the telephone system that connects to local
subscriber lines. Central Office
9. It is a communication system in which a dedicated channel is to set up between parties for the duration of the communication.
Common-channel Signaling
10. A control system for telephone switching that sets up one call and then goes on to set up another call without being tied up for the duration of the first call.
Common Control
11. A switching system that uses a matrix arrangement of
incoming and outgoing lines. Crosspoint Switch 12. Interference between two signals multiplexed into the
same channel. Crosstalk
13. In ISDN, it is the communication channel used for
setting up calls and not for user communication. Data Channel 14. It is a signaling using combinations of two audio tones
transmitted on the voice channel.
Dual-tone Multifrequency Dialing (DTMF)
15. Another name for central office. End Office 16. It is the use of optical fiber for telephone connections
tom individual customers. Fiber-in-the-loop (FITF) 17. It is a switching network that relies on a computer to
find the most direct route between two points. Flat Network 18. A type of communication system that allows
communication in both directions simultaneously. Full Duplex 19. A frequency-division multiplexing scheme that allows
twelve voice signals to be transmitted in one channel. Group 20. It is a specialized transformer that allows telephone
voice signals to travel in both directions simultaneously on a single twisted-pair loop.
Hybrid Coil
21. Telephone system using digital local loops for both voice and data, with the codec in the telephone equipment.
Integrated Services Digital Network (ISDN)
22. A frequency-division multiplexed signal consisting of
six mastergroups or 3600 voiceband channels. Jumbogroup 23. Another name for bit stuffing. Justification
24. Colloquial term for subscriber line interface card. Line Card 25. Inductance added to a twisted-pair telephone line to
reduce its losses for voice frequencies. Loading Coil 26. Small data network covering one or several buildings. Local Area Network 27. A frequency-division multiplexed signal carrying 10
supergroups or 600 voice channels. Mastergroup 28. A system for setting up long-distance calls using pairs
of tones sent along voice channels. Multifrequency Signaling (MF) 29. A term used to describe a telephone instrument that is
ready for use, handset is lifted from its cradle. Off Hook 30. A term used to describe a telephone instrument is
ready to receive a ring signal. On Hook 31. A control or supervisory signal that is transmitted on a
voice channel, but at dc or at such a frequency that it will not be heard.
Out-of-band Signal
32. A communication system that works using data divided
into relatively short transmissions called packets. Packet-switched Network 33. Place where one telephone network connects to the
other. Point of Presence (POP)
34. Dialing that works by interrupting the dc loop current. Pulse Dialing 35. The earpiece of the telephone. Receiver 36. The red wire in a telephone circuit that normally has
negative polarity. Ring
37. Signal sent by the network to the calling telephone to
indicate that the called telephone is ringing. Ringback Signal 38. A low-level voice signal sent to a telephone receiver
from the transmitter in the same telephone. Sidetone 39. System used in telephony which transmits all call
setup information on a packet-data network that is separate from the voice channels used for telephone conversations.
Signaling System Seven (SS7)
40. A switch that connects only to other switches and not
to individual customers. Tandem Office 41. The green wire in a telephone loop that normally has
positive polarity. Tip
43. The layout of a system such as a telephone network. Topology 44. AT&T trademark for DTMF dialing. Touch-tone Dialing 45. The microphone in a telephone. Transmitter 46. A connection between telephone offices. Trunk Line 47. The signal loss in decibels between the transmitting
and receiving ends of telephone connection. Via Net Loss (VNL) 48. The central office supply is the _______. Battery
49. The circuit board that connects a local loop to the
central office. Subscriber Line Interface Card (SLIC) 50. A frequency-division multiplexed signal consisting of
three jumbogroups or 10,800 voiceband channels. Superjumbogroup 51. A switch that connects central offices together. Tandem Office 52. The first automatic telephone switch is invented by Almon B. Strowger 53. The crossbar system used relays for _______. Memory
54. The on-hook voltage. 48 V dc
55. The off-hook voltage at phone. 5 to 10 V dc 56. The off-hook current. 23 to 80 mA 57. The dial tone frequencies. 350 and 440 Hz 58. The ringing voltage at office. 100 V ac 59. The ringing voltage at phone. 80 V ac 60. The ringback voltage frequencies. 440 and 480 Hz 61. The busy signal frequencies. 480 and 660 Hz 62. The function of the line card can be remembered by
CHAPTER 9: DATA TRANSMISSION
1. An error control system based on the repetition of data blocks that contain errors.
Automatic Request for Transmission (ARQ)
2. Bits that do not carry the message. Bit Overhead 3. Addition of extra bits to a data block to avoid the
accidental generation of a flag pattern. Bit Stuffing 4. A set of rules that translates alphanumeric characters
into binary numbers. Character Code 5. Refer to no. 4: Another name for it. Character Set,
Data Code 6. An error-detecting method in which the binary number
corresponding to the group of bits to be checked is divided by a predetermined binary number.
Cyclic Redundancy Checking (CRC)
7. A telephone connection via the public switched
telephone network. Dial-up Line
8. An error correcting system in which errors are
corrected at the receiver using redundant transmitting data without using retransmission requests.
Forward Error Correction (FEC)
9. A group of bits sent between framing signals in a
bit-oriented synchronous communication system. Frame 10. A data-compression scheme that uses fewer bits to
represent more frequently occurring characters or bits patterns.
Huffman Coding
11. A line condition corresponding to a binary one. Mark 12. Simultaneous transmission of multiple data bits using
several channels. Parallel Transmission 13. A data-compression scheme that replaces repeated
characters or bit patterns with a code indicating the character and the number of repetitions.
Run-length Encoding
14. A data transmission using only one channel. Serial Transmission 15. A line condition corresponding to a binary zero. Space
16. This bit alerts the receiver to the beginning of a transmitted character by changing the line from the mark to the space condition.
Start Bit
18. A device, generally an IC that converts from parallel to serial format.
Universal Asynchronous Receiver- Transmitter (UART)
19. Data that consists of alphanumeric characters must
first be encoded using a ____________ ___________. Character Code 20. It actually involves synchronizing the transmitting the
receiver clocks at the start of each character. Asynchronous Communication 21. It must be converted from parallel to serial form
before being transmitted and back to parallel form at the receiver.
Computer Data
22. Since noise is present in all communication systems,
______ will occur. Errors
23. Errors can be detected and corrected by adding
_________ __________. Redundant Information 24. ____ data is important to ensure its privacy. Encryption
25. It is originally used with electromechanical teletype
machines. Baudot Code
26. Refer to no. 25: It has been designated as ____________ by CCITT.
International Telegraph Alphabet Number 2 (ITA2)
27. The most common code for communication between microcomputers.
American Standard Code for Information Interchange (ASCII) 28. Sometimes ASCII codes are expressed in ________ or
________ notation.
Decimal, Hexadecimal 29. The transmitter and receiver are synchronized to the
same clock frequency. Synchronous Communication 30. it involves the addition of one extra bit to the bits that
encode a character. Parity
31. It is a data-transfer protocol for microcomputers that
in its original and most basic form, uses this method. XMODEM 32. They allow single errors in a block of data to be
CHAPTER 10:LOCAL AREA NETWORKS
1. The information signal on LAN. Baseband 2. A system in which the baseband signal is used to
modulate a higher-frequency carrier signal. Broadband System
3. A system for controlling network traffic. Carrier Sense Multiple Access with Collision Detection (CSMA/CD) 4. a network in which a physical connection from one end
to the other of a data path is maintained for the duration of a period of communication.
Circuit-switched Network
5. The loss of data that occurs when two stations
transmit at the same time on a network. Collision 6. An Ethernet cable that has the transmit and receive
connections reversed at one end. Crossover Cable 7. A type of LAN that has a logical bus structure using
CSMA/CD. Ethernet
8. A network with one or more specialized nodes that
contain files and operating software for the network. Client-server Network 9. Refer to no. 8: another name for it. File Server
10. Two-way communication in both directions at the same
time. Full Duplex
11. The central connecting point of a star network to which
all other nodes connect. Hub
12. A type of LAN that is a physical star and logical
token-ring. IBM Token-ring System
13. A small data network that typically operates within one
building or a localized group of buildings. Local-area Network (LAN) 14. The hub of an IBM token ring network. Multistation Access Unit (MAU) 15. A term used to describe a computer operating system
that allows multiple programs to run simultaneously without interfering with each other.
Multitasking
16. A plug-in circuit board for a computer that contains the necessary hardware and firmware to connect the
computer to the local area network.
Network Interface Card
17. One station that is attached to a network. Node 18. The smallest block of data transmitted over a network. Packet
19. The network in which all nodes can contribute network
resources and also run local programs. Peer-to-peer Network 20. A network node dedicated to interfacing between the
network and one or more printers. Print Server 21. A modem that modulates data onto a very high
frequency carrier. Radio-frequency Modem (RF) 22. A network topology in which data circulates from one
computer to the next in sequence. Ring 23. A device that links two or more networks. Router 24. A network topology in which all nodes are connected
individually to a central point. Star 25. In an Ethernet network, it is the device that can send
incoming packets to one of several destinations. Switch 26. A method of network control that involves a short
packet that circulates around the network. Token Passing 27. Refers to the messages to be transferred over a
network. Traffic
28. The ratio between the velocity of propagation of electromagnetic energy through a medium or along a transmission line and the speed of light in vacuum.
Velocity Factor
29. A large network extending over an area greater than
that of a city. Wide-area Network (WAN)
30. Possible data network arrangements in a small LAN.
Star, Ring, Bus
31. The largest WAN. Internet
32. Ethernet was originated by _______. Xerox 33. The year that IEEE began to draft standards for LANs. 1980 34. It is used for the slowest 10 Mb/s version of Ethernet. Coaxial Cable 35. This is used by most 10 Mb/s and 100 Mb/s Ethernet
installations. Unshielded Twisted Pair (UTP) Cable 36. It is a special cable that consists of two parallel wires
with a grounded shield around them. Twinax Cable 37. The effect of a switch is to greatly reduce ________. Contention
CHAPTER 11: WIDE AREA NETWORKS AND THE INTERNET
1. Any computer network that extends for more than a short distance such as a building or related groups of buildings.
Wide-area Network
2. A system that allows users to access documents from
widely separated sources on the Internet. World Wide Web (WWW) 3. A versatile data-transmission system using 53-byte
packets and designed o enable various kinds of data. Asynchronous Transfer Mode (ATM) 4. A network-to-network connection that passes only data
addressed to a node in the other network. Bridge 5. A method of organizing a network in which a physical
path is dedicated to communication between two node for the duration of communication.
Circuit Switching
6. The second layer of the OSI model. Data Link Layer 7. A data-communications protocol created by Digital
Equipment Company for its minicomputer products. DEC Network Architecture (DNA) 8. A method whereby messages can be left for individual
network users. Electronic Mail (e-mail) 9. A program in TCP/IP protocol that allows for the
transfer of both binary and text files between computers with otherwise incompatible operating systems.
File-transfer Protocol (FTP)
10. A software to prevent unauthorized access to computers on a network by computers outside the network.
Firewall
11. A bit or sequence of bits that indicates the beginning
or end of a packet. Flag
12. A packet-transport protocol, similar to X.25 but with
less error connection Frame Relay 13. A computer system that provides modern access to the
public at no charge. Freenet
14. A device used to connect computers or networks
running incompatible operating systems. Gateway 15. A sequence of bits at the beginning of a packet,
routing.
16. A data-transfer that allows quick transitions by simply
clicking on a highlighted word or picture with a mouse. Hypertext Transport Protocol (HTTP) 17. A worldwide public network of networks that connects
a very wide variety of computers, applications, and users.
Internet
18. A suite of protocols that allows a wide variety of computers to share the same network.
Transmission Control
Protocol/Internet Protocol (TCP/IP) 19. A network that encompasses a city and its environs. Metropolitan-area Network (MAN) 20. A private network that uses the same TCP/IP protocol
suite as the Internet. Intranet
21. The third layer of the OSI protocol model. Network Layer 22. Electronic bulletin boards devoted to a wide variety of
subjects, accessible via the internet. Newsgroups 23. A system for organizing data-transmission protocols
developed by the ISO.
Open Systems Interconnection (OSI) Model
24. A way of organizing a network so that small blocks of
data are routed individually from source to destination. Packet Switching 25. The lowest level of the OSI protocol model. Physical 26. A formal set of conventions governing the format and
the timing of messages. Protocol 27. A device used to extend a network or other digital
communication system by regenerating bits and restoring voltage levels and timings to their original values.
Repeaters
28. A device used to interconnect networks. Router 29. The part of the TCP/IP suite that allows for email over
the Internet and similar networks by specifying the control messages used in mail transfer.
Simple Mail Transfer Protocol (SMTP)
30. A network in which nodes receive a packet of data from the source or a node closer to the source and then transmit it to the destination or a node closer to the destination.
Store-and-forward Network
31. An IBM system for transferring data between IBM mainframes and between IBM mainframes and other computers.
32. A system to allow users to log on to a distant host by
emulating a dumb terminal. Telnet 33. A link between computers in which each recognizes a
software connection to the other. Virtual Circuit 34. A very popular system for defining and switching data
packets on computer networks. X.25 Protocol 35. It is responsible for detecting and correcting errors
within frames of data and providing the flags that indicate the beginning and end of frames.
Data Link
36. It sets up the path to transmit data between terminals
and arranges data into packets. Network 37. It deals with the matters such as voltage and current
levels. Physical
38. ______ ______ are available with data rates from 56
kb/s up. Leased Lines
39. It was created by the United States military for providing alternate route in their network in case of trouble.
ARPANET
40. Meaning of ARPANET. Advanced Research Projects Agency Network
CHAPTER 12: DIGITAL MODULATION AND MODEMS
1. Data transmission by varying the amplitude of the
transmitted signal. Amplitude Shift Keying (ASK) 2. The telephone local loop that combines analog telephone
service with data communications. Asynchronous Digital Subscriber Line 3. Use of an audio tone of two or more different frequencies
to modulate a conventional analog transmitter for data transmission.
Audio Frequency-shift Keying (AFSK)
4. Speed at which symbols are transmitted in a digital
communication system. Baud Rate
5. Speed at which data is transmitted in a digital
communication system. Bit Rate
wiring.
7. Variant of QAM used with ADSL data communication systems
Carrierless Amplitude Phase (CAP) Modulation
8. In digital communication, it is a pattern showing all the
possible combinations of amplitude and phase for a signal. Constellation Diagram
9. A modem is also known as ____________. Data Communications Equipment (DCE)
10. A terminal or computer than communicates via a modem. Data Terminal Equipment (DTE) 11. Digital modulation scheme that represents a bit pattern by
a change in phase from the previous state. Delta Phase-Shift Keying (DPSK) 12. Any digital modulation scheme that codes two bits of
information per transmitted symbol. Dibit System
13. It uses many carriers at different frequencies. Discrete Multi-tone (DMT) Modulation
14. A transmission speed that is less than the maximum of
which a modem is capable. Fallback 15. A device for the transmission and reception of facsimile
documents. Fax Modem
16. A means of ensuring that a transmitter sends data only
when the associated receiver is ready to receive it. Flow Control 17. digital modulation scheme using two or more different
output frequencies. Frequency Shift Keying (FSK) 18. Variant of FSK which uses the minimum possible frequency
shift for a given bit rate.
Gaussian Minimum-shift Keying (GMSK)
19. A series of commands transmitted to the modem
whenever a communications software program is loaded. Initialization String
20. A logic one. Mark
21. acronym for modulation-demodulation. Modem 22. A cable used to make a direct connection between two
devices using their serial ports. Null Modem 23. A means of transmitting data by shifting the phase angle
of the transmitted signal. Phase-shift Keying (PSK) 24. PSK that employs four different phases and allows two bits
of information to be transmitted simultaneously.
Quadrature Phase-shift Keying (QPSK)
25. A means of transmitting data by shifting both the amplitude and the phase of the transmitted signal.
Quadrature Amplitude Modulation (QAM)
26. Binary zero. Space 27. A transmitted signal that can have two or more possible
states. Symbol
28. A series of tones transmitted by a modem to allow the
automatic adjustment of line equalization. Training Sequence 29. Just as in analog transmission, digital transmission use s
the following variations.
Frequency, Phase, Amplitude 30. the maximum data rate for a channel is a function of the
following.
Bandwidth, Modulation Scheme, Signal-to-noise Ratio 31. The modem that places the call. Originate Modem 32. The modem that receives the call. Answer Modem 33. When the flow control is accomplished by changing levels
on the RS-232 lines it is called _____________. Hardware Flow Control
CHAPTER 13: MULTIPLEXING AND MULTIPLE-ACCESS TECHNIQUES
1. Extra bits used to spread the signal in a direct
sequence spread spectrum system. Chips 2. System to allow multiple users to use the same
frequency with separate PN codes and a spread-spectrum modulation scheme.
Code-division Multiple Access (CDMA)
3. Form of frequency spectrum communication in which the RF carrier continually moves from one frequency to another according to a prearranged pseudo-random pattern.
Frequency Hopping
4. Sharing of a communication channel among multiple users by assigning each a different carrier frequency.
Frequency-division Multiple Access (FDMA)
5. Combining of several signals into one communication channel by assigning each a different carrier
frequency.
Frequency-division Multiplexing (FDM)
6. Use of a single channel by more than one transmitter. Multiple Access 7. Use of a single channel by more than one transmitter. Multiplexing 8. Improvement in interference rejection due to Processing Gain
spreading in a spread-spectrum system.
9. A transmitted series of ones and zeros that repeats after a set time, and which appears random if the sequence is not known to the receiver.
Pseudo-random Noise Sequence (PN)
10. Variation of received signal strength due to multipath
fading. Rayleigh fading
11. A method of switching that provides a separate
physical path for each symbol. Space Switching 12. Improvement in interference rejection due to
spreading in a spread-spectrum system. Spreading Gain 13. system to allow several transmission to use channel by
assigning time slots to each. Time-division Multiple Access (TDMA) 14. System to combine several data streams onto a single
channel by assigning time slots to each. Time-division multiplexing (TDM) 15. A method of switching that moves a signal from one
time slot to another on the same physical path. Time Switching 16. It is used extensively in telephony. TDM
CHAPTER 14: TRANSMISSION LINES
1. Any pair of conductors used to conduct electrical energy. Transmission Line 2. A device for coupling balanced and unbalanced lines. Balun
3. It is the ratio between voltage and current on an infinitely
long transmission line. Characteristic Impedance 4. A transmission line containing concentric conductors. Coaxial Line
5. A transmission line containing parallel conductors separated
by spacers. Open-line Wire
6. It is the speed at which signals travel down a transmission
line. Propagation Velocity
7. A section of transmission line, electrically a quarter-wavelength in length, that is used to change impedances on a transmission line.
Quarter-wave Transformer
8. It is the ratio of reflected to incident voltage on a
transmission line. Reflection Coefficient 9. It is the graphical transmission line calculator. Smith Chart
10. It is the ratio of maximum to minimum voltage on a
transmission line. Standing-wave Ratio 11. A short section of line, usually short-circuited at one end,
used for impedance matching. Stub
12. Another name for characteristic impedance. Surge Impedance 13. It is the ratio of speed of propagation on a line to that of
light in free space. Velocity Factor
14. Two types of transmission line. Balanced and Unbalanced Lines 15. A coaxial cable is the best example for this kind of
transmission line because it lacks symmetry with respect to ground.
Unbalanced Line
16. Parallel lines are usually operated as _________
_________ that is; the impedance to ground from each of the two wires is equal.
Balanced Line.
17. This happens when frequency increases, the region of high current density becomes thinner, reducing the
cross-sectional area and increasing the resistance of the conductor.
Skin Effect
18. What are present in the electrical model of a transmission line?
Resistance, Conductance,
Capacitance, Inductance 19. Such a line is called _______ since the inductive and
capacitive reactances store energy but do not dissipate it. Lossless 20. A transmission line that is terminated in its characteristic
impedance is called __________ ________. Matched Line 21. For a lossless line, resistance and conductance values
would be ______. Zero
22. A line that is terminated by an impedance other than
characteristic impedance is said to be ______. Mismatched 23. It is the expected signal that would simply move down the
line and disappear into the load because it is a matched line.
Traveling Wave
24. The length of line that causes a delay of one period is
known as ________. Wavelength
the incident and reflected waves that causes what appears to the stationary pattern of waves on the line.
26. two kinds of traveling waves. Incident waves, Reflected waves 27. These are traveling waves that are coming from the
transmitter. Incident waves
28. These are traveling waves that are brought back to the
transmitter due to unmatched line. Reflected waves 29. Most desirable amount of SWR. 1 (one) 30. Most desirable amount of reflection coefficient. 0 (zero)
31. Transmission line losses in mechanisms.
Conductor Loss, Dielectric Loss, Radiation Loss, 32. Transmission line losses are usually given in _________ per
100 meters or 100 feet. Decibels
33. The radius of the circle in the Smith Chart represents
_______. SWR
34. It is a specialized test equipment for transmission line measurements in both the time and the frequency domains.
Time-domain Reflectometry
35. It is a short section of air-dielectric coaxial line, with a slot
in the outer conductor through which a probe is inserted. Slotted Line 36. The length of a slotted line must be at least ___________. One-half wavelength 37. This device allows the measurement of power moving
along the line in each direction, that is, it is possible to measure incident and reflected power separately.
Directional Coupler
CHAPTER 15: RADIO-WAVE PROPAGATION
1. The process by which the waves travel through a medium. Propagation 2. It is the reduction in signal strength due to spreading of the
waves at a distance from the transmitter. Attenuation of Free Space 3. The magnitude of the electric field required to cause
4. It is a means of propagation in which the waves are confined within a refractive region of the troposphere or between such a region and the ground.
Ducting
5. A device that allows a transmitter and a receiver, operating at different frequencies, to be connected to the same antenna and operate simultaneously.
Duplex
6. The area from which a receiving antenna can be considered
to extract all the energy I an electromagnetic wave. Effective Area 7. It is the ratio of the electric force on a charge to the
charge, at a given point. Electric Field Strength 8. Refer to no. 7: another name for it. Electric Field Intensity 9. A vacuum that allows radio waves to propagate without
any obstruction. Vacuum
10. A vertically-polarized electromagnetic wave that propagates
along the surface of the earth. Ground Wave 11. It is the ratio of the phase velocity of a wave in free space
to that in the medium under consideration. Index of Refraction 12. The ionized region of the earth’s atmosphere. Ionosphere 13. A hypothetical antenna having zero physical size and no
loss and radiating equally in all directions. Isotropic Radiator 14. It is the highest frequency that will be returned by the
ionosphere at a given point.
Maximum Usable Frequency (MUF)
15. These are changes to the baseband signal caused by
multipath reception. Multipath Distortion 16. It is a situation in which a signal arrives at a receiving
antenna via two or more paths Multipath Reception 17. A line drawn perpendicular to the interface between two
media. Normal
18. It is the ratio between the signal appearing at the transmitting antenna terminals and that the receiving antenna terminals.
Path Loss
19. It is the quantum of electromagnetic radiation. Photon 20. It is the direction of the electric field vector of an
electromagnetic wave. Polarization 21. The power flowing through a unit cross-sectional area
