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Communications Reviewer November 2006
TELEVISION
Question:“The keystone effect produces a square
raster”- it is a ___ statement. Answer: false
Question:The width of a vertical sync pulse with its
serrations includes the time of Answer: six half lines or three lines
Question:Sawtooth generator circuits produce the
scanning raster, but the sync pulses areneeded for
Answer: timing
Question:“31,500 Hz for the vertical scanning
frequency” is a ____ assertion. Answer: wrong
COLOR TELEVISION: CIRCUITS AND
SIGNALS
Question:Brightness variations of the picture
information are in the ___ signal. Answer: Y or luminance
Question:The hue 180 degrees out of phase with red
is Answer: cyan
Question:Greater peak to peak amplitude of the 3.58
MHZ chrominance signal indicates more _____. Answer: saturation
Question:The interfering beat frequency of 920 kHz is
between the 3.58 MHz color subcarrier and the Answer: 4.5 MHz intercarrier sounds
ECE Board November 2005Question:
The hue of color sync phase is Answer:
yellow-green
Question:___ signal has color information for 1.3 MHz
bandwidth. Answer: I
Question:“A fully saturated color is mostly white” – it
is a ____ statement. Answer: false
Question:The color with the most luminance is
Answer: yellow
Question:The hue of a color 90 degrees leading sync
burst phase is Answer: cyan
Question:The average voltage value of the 3.58 MHZ
modulated chrominance signal is the Answer: brightness of the color
Question:AC video signal drive is varied by the
Answer: contrast
Question:The input signal for the video amplifier is
supplied by the Answer: video amplifier
Question:The video amplifier bandwidth in a
monochrome receiver is generally Answer:
3.2 MHZ
Question:The dc component of the video signal
determine the Answer: brightness
Question:
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Communications Reviewer November 2006
What method is used to preserve the dccomponent?
Answer: direct coupling
Question:The frequency of the second IF signal when
the receiver is tuned to UHF channel 14 is Answer: 4.5 MHz
Question:The maximum frequency deviation of the
FM associate sound signal is Answer: 25 kHz
Question:The ____ is the main source of the receiver
noise. Answer: mixer
Question:A break in the ____ can cause the symptom
of no picture on a clean raster without snow. Answer: IF section
Question:A break in the ____ can cause the symptom
of no picture but with snow. Answer: antenna circuit
Question:A/an ______ is usually out of sync.
Answer: overload picture
Question:A TV monitor does not have an ____.
Answer: RF tuner
Question:The standard level of composite video
signal for connections between modular units
is Answer: 1 Vp-p
Question:A ___ voltage supply for the picture tube is
included in the TV monitor. Answer: high
RASTER CIRCUITS AND SYNC
Question:All the sync pulses have ____ amplitude
Answer: the same
Question:The ____ pulse has the lowest frequency
Answer: V sync
Question:The sync separator is a
Answer: common emitter amplifier
Question:The _____ includes all the sync pulses.
Answer: separated sync
Question:The input for the V integrator is taken from
the ______. Answer: sync separator
Question:The separated sync is _____ from the pulses
in the composite video signal. Answer: inverted
Question:The output from the RC integrator is the
voltage across ____. Answer: CQuestion:
A typical time constant for the verticalintegrator is ____
Answer:
50 µ s
Question:
A single bright line across the center of thescreen can be caused by
Answer: failure of the oscillator or amplifier or a defect in the coupling circuits or yoke
Question:Too much black space at the bottom of the
screen can be caused by ____ Answer:
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Communications Reviewer November 2006
weak vertical output
Question:The _____ on the vertical amplifier affects
the height and linearity of the raster. Answer: dc bias
Question:The diagonal black bar represents
Answer: H scanning
Question:_____ control makes the picture stop rolling.
Answer: V-hold
Question:HAFC or horizontal AFC is a
Answer: PLL
Question:HAFC is for the
Answer: horizontal sync
Question:Horizontal flyback is for
Answer: high voltage
Question:The output stage operates similar to
Answer: class C amplifier
Question:The ____ system is used in television
cameras and other studio equipment toprovide the V and H drive signals. It providesexcellent interlacing.
Answer: gen-lock
Question:The whole gen-lock circuit can be contained
in _____ dedicated chip. Answer: one
Question:The master oscillator operates at
Answer: 31.5 kHz
Question:
No ___ hold is used. Answer: vertical
Question:For the TV supply, the Tripler is for
Answer: high voltage
Question:For the TV power supply, the voltage
regulator is used for the Answer: line rectifier
Question:___ results in a total loss of the raster since
the flyback high voltage depends on thehorizontal output.
Answer: no horizontal output
COLOR TELEVISION RECEIVER CIRCUITS
Question:The Y signal produces a ____.
Answer: monochrome picture
Question:The drive controls are adjusted for ____.
Answer: white
Question:
Color ___ generally does not have a drivecontrol.
Answer: red
Question:When the blue gun is dead, the
monochrome picture and raster will be Answer: yellow
Question:A monochrome picture can be produced
Answer: without the 3.58 MHZ chroma section
Question:An open in the _____ output-adder stage
results in a magenta picture. Answer: green
Question:
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Communications Reviewer November 2006
The value of the beat frequency betweenthe associated sound carrier and colorsubcarrier is
Answer: 920 kHz
Question:The beat frequency between the associated
sound carrier and the picture carrier is ____. Answer: 4.5 MHZ
Question:The relative gain for 42.17 MHz in the IF
amplifier is Answer: 50 %
Question:The bandpass amplifier is tuned to 3.58
MHz with a typical bandwidth of ____. Answer: +/- 0.05 MHz
Question:The ____ control varies the gain of the
bandpass amplifier. Answer: color
Question:The _____ is on during H flyback time.
Answer:
burst amplifier
Question:A _____ needs two input signals.
Answer: synchronous demodulator
Question:The _____ provides dc color voltage for the
color oscillator. Answer: AFPC circuit
Question:The ____ control adjusts for the phase angle
for the demodulated color video signals. Answer: tint
Question:Circuits that can cause the trouble of no
color are Answer:
bandpass amplifier, color oscillator, and color killer
Question:A fixed phase error in the color oscillator
causes Answer: wrong hues
Question:The R-Y demodulator fails. Colors ___ and
___ will be missing from the picture Answer: red, cyan
Question:The ACC circuit varies the gain of the ____
Answer: first BPA
Question:The manual color control varies the
amplitude of the _____ chroma signal. Answer: 3.58 MHZ
Question:The output from the BPA feed the
Answer: demodulators
Question:The burst amplitude used to determine the
Answer:
ACC bias
Question:The color killer is on the
Answer: BPA
Question:____ is used to produce the dc bias from the
color killer diode detector. Answer: burst
Question:Color snow or confetti is predominantly
____. Answer: magenta
Question:The angle between R-Y and B-Y is
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Communications Reviewer November 2006
Answer: 90 degrees
Question:The bandwidth of the I signal is
Answer: 1.3 MHz
Question:DC coupling used for the ____ output.
Answer: demodulator
Question:The crystal ringer is shock-excited by ___.
Answer: color burst
Question:In an AFPC phase detector, the ____ and ___
cw signals are 90 degrees out of phase. Answer: burst, oscillator
Question:The burst separator is ___ during horizontal
trace line. Answer: off
Question:______ means that colors drift through the
picture. Answer: no color sync
Question:The superband channel number just above
VHF broadcast channel 13 is Answer: 23
Question:VHF broadcast channel does a TV receiver
with a cable converter stay tuned at Answer: 2, 3, or 4
Question:The ___ conductor of coaxial cable serves as
a shield. Answer: outer
Question:Generally ____ cable is used for the drop
line. Answer:
RG-59U
Question:Thinner cable has _____ losses.
Answer: greater
Question:The value of R that was used to terminate
Rg-59U coaxial cable for impedance matchingis
Answer: 75 ohms
Question:A line with more C per unit length has a
lower ____. Answer: Zo
Question:Open ends of transmission line correspond
to a _____ resonant circuit. Answer: parallel
Question:The value of the VSWR when a cable is
terminated in its Zo is Answer: 1.0
Question:Cable losses increases at ____ frequencies.
Answer: higher
Question:Coaxial cables have ____ losses.
Answer: I2R
Question:A ___ loss reduces the signal level by one-
half. Answer: 6 dB
Question:
The _____ of a cable system is the startingpoint of cable signals.
Answer: head-end
Question:A ____ is the main line for cable signals.
Answer: trunk cable
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Communications Reviewer November 2006
Question:The insertion loss is ____ than the tap loss
for line taps. Answer: lower
Question:A ____ is used to match the 75 ohms coaxial
cable to the 300 ohms receiver input. Answer: balun
Question:The reference level for the dBmV unit is
____. Answer: 1 mV
Question:The signal level of 2 mV in dBmV units is
Answer: 6 dBmV
Question:The signal level of 0.5 mV in dBmV units is
__. Answer: -6 dBmV
Question:Sync and blanking bars from another
channel can be caused by _____. Answer: overload distortion
Question:
Losses increase with higher _____. Answer: temperature
Question:A slope-control circuit increases the
amplifier gain for ___-frequency channels. Answer: higher
Question:In two-way cable systems, the ____ for
downstreams and upstream signals. Answer: same cable
Question:The upstream signal is in the band of _____.
Answer: 5 to 30 MHz
Question:
The polling signal is in the band of Answer: 107 to 119 MHz
Question:The cable converter uses ___ local
oscillators. Answer: two
Question:The video IF carrier in a cable converter is
generally Answer: 612.75 MHz
Question:The local oscillator for the up converter
operates in the ___ range. Answer: UHF
Question:Each cable channel is selected by setting
the frequency of the ___ for the up converter.
Answer: VCO
Question:Wave traps to attenuate premium channels
are usually located ___. Answer: in the feed line to each subscriber
Question:
A scrambled channel usually has a ____ , asevidenced by rolling and diagonal bars.
Answer: picture that is out of sync
Question: A scrambled channel needs _____ pulses to restore the sync.
Answer: decoding
Question:_____ have the cable channels that are
heterodyned down to lower frequencies. Answer: supertrunks
Question:The frequency of 13 GHz is in the ____ band
Answer:
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Communications Reviewer November 2006
microwaveQuestion:
_____ can be used for microwave links fortelevision.
Answer: FM
Question:______ cable has very low losses.
Answer: fiber optics
Question:____ means the bending of light waves.
Answer: refraction
Question:______ cables makes use of internal
reflections of light. Answer: fiber optic
Question:Typical index of refraction for glass
Answer: 1.8
Question:Typical index of refraction for diamond
Answer: 2.4
Question:Typical index of refraction for water
Answer:
water
TELEVISION AND VIDEO SERVICING
Question:An ____ transformer has separate primary
and secondary windings. Answer: isolation
Question:The ______ blade in a polarized AC line plug
connects to the chassis in the receivers with aline operated half-wave rectifier.
Answer: wider
Question:______ has higher resistance as a DC
voltmeter. Answer: DMM
Question:Meter loading ______ the voltage reading.
Answer: decreases
Question:The external multiplier for a high voltage
probe is Answer: 900 megaohms
Question:The TV switch on an oscilloscope can be set
for ______ cycles of video signal, at either theV or the H scanning rate.
Answer: two
Question:A _______ oscilloscope has a CRT with two
electron guns. Answer: dual-beam
Question:A delayed sweep oscillator uses ________
internal time bases. Answer: two
Question:A _______ produces the IF output signal.
Answer: tuner subber
Question:The NTSC ________ produces standard
chroma and luminance values. Answer: color-bar generator
Question:The color bars in a gated rainbow pattern
differ in hue phase by Answer: 30 degrees
Question:
Color bars have the standard amplitude of Answer: 75 IRE units
Question:The range of the tint control when it can
move a color one bar to the left and right is Answer: +/- 30
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Communications Reviewer November 2006
Question:Which color difference signal has the same
phase as the burst? Answer: B-Y
Question:Which color bar has the output from a B-Y
demodulator? Answer: 6th
Question:No horizontal output _____
Answer: can kill the sound
Question:A receiver with current in the ADG coils has
______ Answer: AC power input
Question:Two pairs of horizontal bars are produced
by Answer: 120 Hz ripple in the video signal
INTRODUCTION TO RADAR
FUNDAMENTALS
Question:Radar is an acronym made up of the words
______. Answer:Radio detection and ranging
Question:What term is used to refer to electronicequipment that detects the presence,direction, height, and distance of objects byusing reflected electromagnetic energy?
Answer:Radar
BASIC RADAR CONCEPTS
Question:Radar uses electromagnetic energy pulses.
The radio-frequency (rf) energy is transmittedto and reflects from the reflecting object. Asmall portion of the energy is reflected andreturns to the radar set. This returned energyis called a(n) _____.
Answer:
Echo
Question:Radar surface angular measurements arenormally made in a clockwise direction from
_______ or from the heading line of a ship oraircraft.
Answer: True north
Question:In radar surface angular measurement, thesurface of the earth is represented by animaginary flat plane, tangent (or parallel) tothe earth’s surface at that location. This planeis referred to as the_____.
Answer: Horizontal plane
Question:In radar surface angular measurements, allangles in the up direction are measured in asecond imaginary plane that is perpendicularto the horizontal plane. This second plane iscalled the ______.
Answer:Vertical plane
Question:What name is given to the line made
directly from the radar set to the object? Answer Line of sight (LOS)
Question: The length of LOS is termed _____.
Answer:Range
Question:How is the angle between the horizontal planeand the LOS known?
Answer:Elevation angle
Question: The angle measured clockwise from true northin the horizontal plane is referred to as the
______.
Answer: True bearing or Azimuth angle
Question:What coordinates are used to describe thelocation of an object with respect to the radarantenna?
Answer:Range, bearing, and elevation
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Communications Reviewer November 2006
Question:Radar surface-angular measurements arereferenced to true north and measured in whatplane?
Answer:Horizontal plane
Question: The distance from a radar set to a targetmeasured along the line of sight is identifiedby what term?
Answer:Range
RANGE
Question:Electromagnetic energy travels through air atapproximately the speed of light, which is
Answer:186,000 statute miles per second or 162,000nautical miles or 984 feet per microsecond or328 yards per microsecond
Question:Radar timing is usually expressed in what unitof time?
Answer:Microseconds
Question: This type of radar set transmits a short burst of electromagnetic energy in order to measuretarget range which is determined by
measuring elapsed time while the pulse travelsto and returns from the target.
Answer:Pulsed radar
Question:Because two-way travel is involved, a totaltime of 12.36 (6.18 x 2) microseconds pernautical mile will elapse between the start of the pulse from the antenna and its return tothe antenna from a target. This 12.36microsecond time interval is sometimesreferred to as a _________.
Answer:Radar mile, radar nautical mile or nauticalradar mile
Question:If the elapsed time for an echo is 62microseconds, then the distance is____.
Answer: 5 miles
MINIMUM RANGE
Question: The _____ alternately switches the antennabetween the transmitter and receiver so thatonly one antenna need be used.
Answer:Duplexer
Question: Timing of this switching action is critical to theoperation of the radar system. The minimumrange ability of the radar system is alsoaffected by this timing. Important factors inthis duplexer switching action are _____.
Answer:
Pulse width and recovery time
Question: The _____ edge of the transmitted pulse causesthe duplexer to align the antenna to thetransmitter. This action is essentiallyinstantaneous.
Answer:Leading
Question: The _____ edge of the pulse causes theduplexer to line up the antenna with thereceiver; however, this action is notinstantaneous.
Answer: Trailing
MAXIMUM RANGE
Question: The maximum range of a pulse radar systemdepends upon
Answer:Carrier frequency, peak power of thetransmitted pulse, pulse repetition frequency(PRF), or pulse repetition rate (PRR), andreceiver sensitivity
Question: The primary limiting factor for the maximumrange of a pulse radar system is the
Answer:Pulse repetition frequency (PRF)
Question:What determines the maximum range thepulse can travel to a target and still return ausable echo?
Answer:Peak power of the pulse
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Communications Reviewer November 2006
Question: ______ is the smallest signal detectable by areceiver system that can be processed andpresented on an indicator.
Answer:A usable echo
Question: The frequency of the rf energy in the pulseradiated by a radar is referred to as the _____ of the radar system.
Answer:Carrier frequency
Question: The carrier frequency is often a limiting factorin the maximum range capability of a radarsystem because radio frequency energy above
_____ is rapidly attenuated by the atmosphere. Answer:3 GHz
Question: The number of pulses radiated in one second iscalled the
Answer:Pulse-repetition frequency (PRF) or the pulse-repetition rate (PRR)
Question: The time between the beginning of one pulseand the start of the next pulse is called
Answer:Pulse repetition time (PRT)
AMBIGUOUS RETURNS
Question: The radar timing system must be reset to zeroeach time a pulse is radiated. This is to
Answer:Ensure that the range detected is measuredfrom time zero each time
Question: The prt of the radar becomes important inmaximum range determination because targetreturn times that exceed the prt of the radar
system appear at incorrect locations (ranges)on the radar screen. Returns that appear atthese incorrect ranges are referred to as
Answer:Ambiguous returns or secondary-sweepreturns
Question:What is the speed of electromagnetic energytraveling through air?
Answer:Approximately the speed of light (162,000nautical miles per second)
Question:How much time is required for electromagneticenergy to travel 1 nautical mile and return tothe source?
Answer:12.36 microseconds
Question:In addition to recovery time, what determinesthe minimum range of a radar set?
Answer:Pulse width
PULSE-REPETITION FREQUENCY AND
POWER CALCULATIONS
Question: The energy content of the pulse is equal to the ______ of the pulse multiplied by the pulsewidth.
Answer:Peak (maximum) power level
Question:Meters used to measure power in a radarsystem do so over a period of time that islonger than the pulse width. For this reason,pulse-repetition time is included in the powercalculations for transmitters. Power measuredover such a period of time is referred to as
Answer:Average power
Question: The product of pulse width (pw) and pulse-repetition frequency (prf) in the above formulais called the ______ of a radar system.
Answer:Duty cycle
Question:What do we call the ratio of the time on to thetime off of the transmitter?
Answer:Duty cycle
ANTENNA HEIGHT AND SPEED
Question:
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Communications Reviewer November 2006
Assume antenna height to be 64 feet, the radiohorizon for this antenna in nautical miles is
Answer:10 nautical miles (nmi)
Solution:
nmi106425.1)ft(h25.1)nmi(d ===
Question:Atmospheric interference with the travel of
electromagnetic energy increases with what rf energy characteristic?
Answer:Frequency
Question:How is prt related to prf?
Answer:PRT is the reciprocal of PRF.
Question:What type of radar transmitter power ismeasured over a period of time?
Answer:Average power
Question:What term is used to describe the product of pulse width and pulse-repetition frequency?
Answer:Duty cycle
BEARING
Question: The ______ of a radar target is the angle
between true north and a line pointed directlyat the target.
Answer: True bearing (referenced to true north) orazimuth angle
Question: True bearing is measured in the ____ plane andin a _____ direction from true north.
Answer:Horizontal, clockwise
Question:
The bearing angle to the radar target may alsobe measured in a clockwise direction from thecenterline of your own ship or aircraft and isreferred to as the _________.
Answer:Relative bearing
ALTITUDE
Question:
Many radar systems are designed to determineonly the range and bearing of an object. Suchradar systems are refrred to by what term?
Answer: Two-dimensional radars (search radars)
Question: These radar systems function as early-warningdevices searching a fixed volume of space.
Answer:2D radar (search radar)
Question:How do we call a search radar system thatdetects altitude as well as range and bearing?
Answer: Three-dimensional (3D) radar
Question:Altitude- or height-finding search radars use abeam that is
Answer:very narrow in the vertical plane
Question:Height-finding radar systems that alsodetermine bearing must have a beam that is
Answer:very narrow in both the vertical and horizontalplanes
Question: _______ scanning permits automaticcompensation for an unstable radar platform(site), such as a ship at sea. Error signals areproduced by the roll and pitch of the ship and
are used to correct the radar beam to ensurecomplete elevation coverage.
Answer:Electronic
Question:What type of scanning technique do weapons-control and tracking radar systems commonlyuse?
Answer:Mechanical elevation scanning
Question:
Most electronically scanned radar systems areused as _____ radars.
Answer:Air search
Question:What type of target bearing is referenced toyour ship?
Answer:Relative bearing
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Communications Reviewer November 2006
Question:What type of radar detects range, bearing, andheight?
Answer: Three-dimensional
Question:What characteristic(s) of radiated energy is(are) altered to achieve electronic scanning?
Answer:Frequency or phase
TARGET RESOLUTION
Question:It is the ability of a radar to distinguishbetween targets that are very close together ineither range or bearing.
Answer: Target resolution
Question: ____ radar, which requires great precision,should be able to distinguish between targetsthat are only yards apart.
Answer:Weapons-control
RANGE RESOLUTION
Question: ______ is the ability of a radar system todistinguish between two or more targets on
the same bearing but at different ranges. Answer:Range resolution
Question: The degree of range resolution depends on Answer: The width of the transmitted pulse, the typesand sizes of targets, and the efficiency of thereceiver and indicator
Question:Which is the primary factor in range
resolution? Answer:Pulse width
Question:A well-designed radar system, with all otherfactors at maximum efficiency, should be ableto distinguish targets separated by
Answer:One-half the pulse width time
Question:If a radar system has a pulse width of 5microseconds, determine the range resolution.
Answer:820 yardsSolution:
( ) ( )
yards820164x5
164xsPWyardsresolutionranges
yards
==
µ=µ
BEARING RESOLUTION
Question:How is the ability of a radar system to separateobjects at the same range but at differentbearings known?
Answer:Bearing (azimuth) resolution
Question: The degree of bearing resolution depends on Answer:Radar beam width and the range of the targetsQuestion:Because the radar beam spreads out as rangeincreases, _____ becomes a factor in bearingresolution.
Answer:Range
Question:A radar beam is defined in width in terms of
______. Answer:Half power points
Question:All the points off the centerline of the beamthat are at one-half the power level at thecenter are plotted to define _____.
Answer:Beam width
Question:When the half-power points are connected tothe antenna by a curve the resulting angularwidth of the curve is called the _____.
Answer:Antenna beamwidth
Question:
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Communications Reviewer November 2006
What determines the beamwidth of a radarantenna?
Answer: The physical size and shape of the antenna
Question:Radar antenna beamwidth can vary from
Answer:About 1 degree up to 60 degrees
Question: Two targets at the same range must beseparated by ______ to be distinguished as twoobjects.
Answer:At least one beam width
RADAR ACCURACY
Question:It is a measure of the ability of a radar systemto determine the correct range, bearing, and,in some cases, height of an object.
Answer:Radar accuracy
Question: The degree of accuracy is primarily determinedby the ____ of the radar system.
Answer:Resolution
PULSE SHAPE
Question:What is the ideal pulse shape?
Answer:A square wave having vertical leading andtrailing edges
Question:A ______ extends the width of the transmitterpulse, although it may add very little to thetotal power generated.
Answer:Sloping trailing edge
Question:A _____ affects minimum range as well asrange accuracy since it provides no definitepoint from which to measure elapsed time onthe indicator time base.
Answer:Sloping leading edge
Question:
Using a starting point at the lower edge of thepulse’s leading edge would increase ______.
Answer:Minimum range
ATMOSPHERIC CONDITIONS
Question:Electromagnetic wavefronts travel throughempty space in straight lines at the speed of light, but the _____ of the atmosphere affectsboth the travel path and the speed of theelectromagnetic wavefront.
Answer:Refractive index
Question:In the atmosphere, the speed of theelectromagnetic wave is affected by
Answer: Temperature, atmospheric pressure, and theamount of water vapor presentQuestion:It is the bending of electromagnetic wavescaused by a change in the density of themedium through which the waves are passing.
Answer:Refraction
Question:It indicates the degree of refraction, or bendingof electromagnetic waves caused by differentsubstances in the atmosphere.
Answer:Index of Refraction
Summary on MicrowaveCommunications
Question:What is the frequency range of microwaves?
Answer: 300 MHz to 300 GHz
Question:Which of the common frequency bands (HF,VHF, UHF, SHF, etc.) are in the microwaverange?
Answer: UHF, SHF, EHF
Question:What types of communication systems liebelow the microwave band?
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Communications Reviewer November 2006
Answer: AM broadcast radio; shortwave radio; FMbroadcast radio; VHF TV; mobile radio
Question:What is the wavelength at the low frequencyend of the microwave band?
Answer: 1 m
Question:What is the wavelength at the middle of themicrowave band?
Answer: 3 cm
Question:What is the wavelength at the high end of themicrowave band?
Answer: 1 mm
Question: Types of microwave communication systems atwhich it operates
Answer: UHF TV 600 MHz Microwave relay 3.9 GHz Satellite communication 6 GHz (up)
4 GHz (down)Troposcatter communication 2 GHz Mobile radio 900 MHz Telemetry 2 GHz
Question:What two problems prevent conventionalelectronic equipment from working atmicrowave frequencies?
Answer: Lead Reactance and Transmit Time
Question:What are the three types of microwavetransmission lines?
Answer: Coaxial cable; stripline; waveguide
Question:What is the maximum power that can beobtained from a microwave semiconductor at10 GHz?
Answer: 10 W
Question:
What is the maximum power that can beobtained from a microwave tube at 10 GHz?
Answer: 500 kW
Question:What are the five types of microwave tubes?
Answer: Klystron; coupled-cavity TWT; helix TWT;Gridded tube; CFA
Question:How much microwave power is received by a3-m2 antenna of the electric field at theantenna is 10-5 V/m and the magnetic field is2.6 x 10-8 A/m?
Answer:0.78 pW Solution::
5 8
2
13
Power Electric Field x Magnetic Field
x Antenna Area
10 V / m x 2.6 x 10 A / m
x 3 m
7.8 x 10
0.78 pW
− −
−
=
=
==
Question:A perfect termination for a transmission line
Answer:Termination (load)
Question:A component that samples the microwavesignal traveling in one direction down a
transmission line Answer:Directional Coupler
Question:A component that combines microwave signalsfrom separate transmission lines into onecommon transmission line and allows nocoupling between the separate lines
Answer:Combiner
Question:
A component containing ferrite material thatallows microwave signals to pass in onedirection through the component, but absorbsmicrowave signals passing in the otherdirection.
Answer:Isolator
Question:
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Given a transmission line of cross section 2 cmby 1 cm (approximately the size of awaveguide operating at 10 GHz), E = 50 V/mand H = 1 A/m. Find the impedance, powerdensity and the total power.
Answer:
Impedance = 50 Ω ; Power density = 2 50W / m ;
Power = 10 mW Solution::
E 50 V / mZ 50 ΩH 1 A / m
= = =
2
2
Power Density E x H
50 W /m x 1 A/ m
50W / m
Power Power Density x Cross sec tional area
50 W / m x 0.02 m x 0.01 m
10 mW
=
=
=
= −
=
=
Question: The receiving antenna of a microwave relay
system has an area of 2m2, E = 377 µV / m,
and H = 1 µA / m. Find the impedance, powerdensity, and total power received by theantenna.
Answer:Impedance = 377 Ω ; Power density =
−10 2 3.77 x 10 W / m ; Power = 754 pW
Solution::
E 377μV / mZ 377Ω
H 1 A / m
= = =
10 2
10 2 2
12
Power Density E x H
377μV /m x 1 A / m
3.77 x 10 W / m
Power 3.77 x 10 W / m x 2 m
7541 x 10 W
754 pW
−
−
−
==
=
=
==
Question:
If two equal microwave signals are added,what is the total signal if (a) the signals are in
phase (phase difference of 0°), (b) 180° out of phase, (c) 270 ° out of phase, and (d) with a
phase difference of 360°? Answer:(a) 2 ; (b) 0 ; (c) 1.416 ; (d) 2Solution::
(a) the signals are in phase so their totalstrength is simply the sum of theirindividual strengths: 1 + 1 = 2.
(b) for a 180° phase difference, one signalreaches its maximum when the otherreaches its minimum. Hence, the signalscancel; 1 – 1 = 0.
(c) for a 270° phase difference, the vectorsum of the signals is taken + = =1 1 2 1.416
(d) when the phase shift is 360°, the signalsare again in phase, 1 + 1 = 2.
Question:A 1-GHz microwave signals moves from point 1to point 2, distance of 3 cm. What is the phasedifference between the points?
Answer:
36°
Solution:: The phase difference is the time required forthe signal to travel between points divided its
period. Thus,
( ) ( )10
9
10
9
Travel timePhase difference x 360
Period
Distance / Velocityx 360
1/ frequency
3 cm 3 x 10 cm / sx 360
1/ 10 s
10x 360
10
36
−
−
= °
= °
= °
= °
= °
Therefore, in traveling 3 cm (slightly more than1 in.), an electromagnetic wave with afrequency of 1 GHz undergoes a 36° phaseshift.
Question: The frequency of the ac power lines in theUnited States is 60 Hz. The typical distancebetween a household and the power plant is10 km (6 mi).What is the phase shift betweenthe household and the plant?
Answer:
0.7°
Solution::21
Period at 60 Hz 1.6 x 10 s60
−= =
3
8
5
10 x 10 mTimefor signalto travelbetweenpoints
3 x 10 m / sec
3.3 x 10 s−
=
=
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5
2
3.3 x 10Phase Shift x 360
1.6 x 10
0.7
−
−= °
= °
The 0.7° phase shift is insignificant and can beignored.
Question:If 10% of the microwave power is reflected atthe mismatch, find the return loss, reflectioncoefficient, and SWR.
Answer:Return loss = 10 dB ; reflection coefficient =0.32 ; SWR = 1.92
Solution::
Re flected power Re turn loss 10log
Incident power
10log0.10 10 dB
=
= =
Re flected power Re flection coefficient
Incident power
0.10 0.32
1 0.33SWR 1.92
1 0.33
=
= =
+= =
−
Question:If the return loss is 20 dB, find the percentreflected power, reflection coefficient, andSWR.
Answer:Reflected power = 1% ; Reflected coefficient =0.1 ; SWR = 1.2
Solution::Re turn loss
%Re flected power Inverse log10
Inverse log2
0.01 1%
Re flected power Re flected coefficient
Incident power
0.01 0.1
1 0.1 1.1SWR 1.2
1 0.1 0.9
= −
== =
=
= =
+= = =−
Question:Design a 50-Ω stripline using 0.03-in.-thick
Teflon fiberglass (ε = 2.55). Determine theguide wavelength at 3 GHz.
Answer:6.26 cmSolution::
( ) ( )
0
0g
Zε 50 2 .55 79.8 Ω
w0.75
b
w 0.75 2 x 0.03 0.045 in.
Then,
λλ
ε
10 cm
2.55
6.26 cm
= =
=
= =
=
=
=
Question:A satellite downlink has a frequency of 4 GHz,a bandwidth of 40 GHz, and uses a cryogenicparamp receiver. Find the power of thereceived signal to maintain a SNR of 20 dB.
Answer:1.8 pW Solution::
Antenna Noise Noise Power Density x Bandwidth
0.00015 pW /MHz x 40 MHz0.006 pW
=
=
=
Reciever Noise Noise Power Density x Bandwidth
0.0003 pW / MHz x 40 MHz
0.012 pW
=
=
=
Then,Total Noise Antenna Noise Reciever Noise
0.006 0.012
0.018 pW
= +
= +
=
Since the signal-to-noise ratio must be 20 dBfor satisfactory operation of the satellitesystem, the received signal must be 100 timesgreater than the noise:
RXP 100 x 0.018 pW
1.8 pW
=
=
Question:Calculate the noise power for (a) a terminationtemperature of 290° K and a bandwidth of 1
MHz and (b) a temperature of 145°K and a 10
MHz bandwidth. Answer:(a) -114 dBm ; (b) -107 dBm
Solution::(a)
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( ) ( ) ( )14
12
N kTB
1 .38 x 10 m W / K MHz 290 K 1 M Hz
4 x 10 mW
114 dBm
−
−
=
= ° ⋅ °
=
= −
(b)
( ) ( ) ( )14
12
N kTB
1.38 x 10 mW / K MHz 145 K 10 MHz
20 x 10 mW
107 dBm
−
−
=
= ° ⋅ °
=
= −
Question:A satellite downlink is operating at 10 GHz witha 40-MHz bandwidth. It has a cryogenicparamp receiver. What received power isneeded to achieve a signal-to-noise of 20 dB?
Answer:-88 dBmSolution::
antenna
paramp
T 10 K
T 20 K
= °
= °
Therefore,
totalT 10 K 20 K 30 K= ° + ° = °
So the noise power is
( ) ( ) ( )14
N kTB
1.38 x 10 mW / K MHz 30 K 40 MHz
108 dBm
−
=
= ° ⋅ °
≈ −
Therefore,Recieved Power 108 dBm 20 dB 88 dBm≈ − + ≈ −
Question:An amplifier has a gain of 40 dB and a noise-figure of 3 dB. The input signal (S in) is -80 dBm,and the bandwidth is 10 MHz. Find SNRin andthe SNRout.
Answer:SNRin = 24 dB ; SNRout = 21 dBSolution::
The noise generated by the input signal
source depends on its temperature, whichfor most applications is 290 °K(roomtemperature). In a 1-MHz band, the noisepower is -114 dBm. In a 10-MHz bandwidth,noise power is 10 dB greater, so here N =-104 dBm. Hence
( )inSNR 180dBm 104 dBm 24 dB= − − − =
Now,
out inS S Gain
80 dBm 40dB
40 dBm
= +
= − += −
and
out inN N NF Gain
104 dBm 3 dB 40 dB
61 dBm
= + +
= − + += −
Hence, ( )outSNR 40 dBm 61 dBm 21 dB= − − − =
Question:In a two-stage amplifier, amplifier1 has a noisefigure of 3 dB and a gain of 20 dB. The secondamplifier has a noise figure of 6 dB. Find thetotal noise figure.
Answer:3.1 dB
Solution:First, express NF and gain as ratios
NF1 = 2
NF2 = 4Gain1 = 100
2total 1
1
total
NF 1NF NF
Gain
4 1NF 2
100
2.03
3.1 dB
−= +
−= +
==
Note that the noise figure of the
combination is hardly affected by thesecond amplifier.
Question:For the system previously discussed, NF1 = 1dB, NF2 = 6 dB, and G1 = 6 dB. What is thetotal noise figure?
Answer:3 dB
Solution::NF1 = 1.26, NF2 = 4.0, Gain = 4, so
2total 1
1
NF 1NF NFGain
4 11.26
4
2
3 dB
−= +
−= +
==
Because the gain of amplifier 1 is so low,the effect of the amplifier 2 is significant.
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Question:A parabolic dish antenna has a diameter of 1m. It operates at 10 GHz, where the free-spacewavelength is 0.03 m. Find the antenna’s gain,beamwidth and aperture.
Answer:
Gain = 38 dB ; Beamwidth = 1.8° ; Aperture =
0.5 m
2
Solution:
( )
( )
2 2
2
2 2
2
D 1Gain 6 6
λ 0.03
6670 38 dB
DBeamwidth 60 60 0.03
λ
1.8
πD π Aperture 0.6 0.6 1
4 4
0.5 m
= =
= =
= ° = °
= °
= =
=
Question:A parabolic dish antenna has a diameter of 3m, and operates at 4 GHz, where thewavelength is 0.075 m. Calculate the antennagain, beamwidth, and aperture.
Answer:
Gain = 40 dB ; Beamwidth = 1.5° ; Aperture =4.2 m2
Solution:2 2
2
2
D 3Gain 6 6λ 0.075
9600 40 dB
D 0.075Beamwidth 60 60
λ 3
1.5
π 9π Aperture 0.6 D 0.6
4 4
4.2 m
= =
= =
= ° = °
= °
= =
=
Question:Calculate the free-space path loss for anantenna operating at 6 GHz that is 25 mi fromthe transmitting antenna.
Answer:10-14
Solution:
( )
14
FSPL 97 20 log R 20 log F
97 20log(25 mi) 20log 6 GHz
140 dB
10−
= − − −
= − − −
= −
=
Question: The difference between incident (input) powerand transmitted power. It can be measured
and includes losses due to reflection andabsorption inside component.
Answer:Insertion loss
Question:Power lost inside component. It is equal toattenuation only if component is perfectlymatched.
Answer: Attenuation
Question:
An input signal is divided in a hybrid into twoequal outputs. What will be the phasedifference between the output signals of thefollowing hybrids are used?(a) 3-dB quadrature
hybrid, (b) 3-dB 180° hybrid, (c) Wilkinsoncombiner.
Answer:
(a) 90° ; (b)180° ; (c)0°
Question:A signal with an amplitude P1 is applied to oneof the input arms of a 3-dB quadrature hybrid.
A signal P2, which is 90° out of phase with P1, is
applied to the other input arm. What is thesignal on each of the output arms of the 3-dBquadrature hybrid?
Answer:P1 + P2 P1 – P2
Question:A circulator has an insertion loss of 1 dB and adirectivity of 21 dB. If a 0-dBm signal is putinto the input port and port 2 is shorted, howmuch power leaks back into the input port?
Answer:-22 dBm
Question:What type of filter can be electronically tuned?
Answer:YIG
Question: Three fixed attenuators with an insertion lossof 3, 6, and 10 dB are connected. What is thetotal insertion loss of the combination?
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Answer:19 dB
Question:What is the power level of the smallest signalthat can be detected above the noise by theSchottky diode?
Answer:-60 dB
Question:What is the power level of the largest signalthat will still be in the square-law range of aSchottky diode?
Answer:-20 dBm
Question:What is the purpose if an oscillator?
Answer:The purpose of an oscillator is to generate amicrowave signal.
Question: The variation in oscillator frequency caused bypower supply voltage or current changes
Answer:Frequency pushing
Question: The variation in oscillator frequency withchanges in load SWR
Answer:Frequency pulling
Question: The time it takes an electronically tunedoscillator to come within a specifiedpercentage of its final frequency after theelectronic control voltage has been changed.
Answer:Settling time
Question: The SNR at a receiver input is 30 dB. If thereceiver has a 5-dB noise figure, what is theSNR at the output?
Answer:
25 dB
Question:Name the three parts of a mixer
Answer:Local oscillator; combiner; Schottky diodes Question:
A mixer has a signal frequency of 10 GHz andan IF frequency of 10 MHz. What is the localoscillator frequency?
Answer:10.01 GHz or 9.99 GHz
Question:What is the advantage of a chip capacitorcompared with microstrip capacitor?
Answer: A chip capacitor provides much higher capacitance values
Question:What is the advantage of dielectric resonatorcompared with a microstrip resonator?
Answer: A dielectric resonator provides a much higher Q
Question:A very small (0.0007 in or 20 µ) wire used forconnecting components in a hybrid microwaveintegrated circuit.
Answer:Bond wire
Question:Provides greater capacitance than canobtained with microstrip capacitors
Answer:Overlay capacitor
Question:Connects from the top of the substrate to theground plane on the bottom
Answer:Via holeQuestion:What advantage do microwave tubes haveover microwave semiconductor devices?
Answer:Tubes can provide much greater power (over 10,000 times more power) than microwavesemiconductor devices.
Question:What is the major disadvantage of microwave
tubes? Answer:Their limited lifetime
Question:What is the advantage of using a low powersemiconductor oscillator driving a high powertube amplifier, instead of a high power tubeoscillator?
Answer:
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Frequency is much easier to control in thelower power semiconductor oscillator
Question:What is the major advantage of a griddedtube?
Answer:Low cost
Question:What is the major advantage of klystron?
Answer:High Power
Question:What is the major advantage of a helix TWT?
Answer:Wide bandwidth
Question:What is the major advantage of a coupled-cavity TWT?
Answer:Good bandwidth and high power achievedtogether
Question:What is the major advantage of a crossed-fieldamplifier?
Answer:High Efficiency
Question:What is the major disadvantage of a griddedtube?
Answer:
Gridded tubes work only at low frequency endof the microwave band
Question:What is the major disadvantage of a klystron?
Answer:Narrow bandwidthQuestion:What is the major disadvantage of TWTs?
Answer:Low efficiency
Question:
What are two disadvantage of a CFA? Answer:Low gain and high noise
Question:What limits the frequency capability of griddedtubes?
Answer:Transmit time of the electrons
Question:How do klystrons, TWTs, and CFAs avoid thetransmit time problem?
Answer:They use velocity modulation
Question:Forms the electron beam
Answer:Electron gun
Question:Focuses the electron beam through theklystron cavities
Answer:Focusing magnet
Question:Collects the electron beam after microwavepower has been extracted from it
Answer:Beam collector
Question:Modulates the microwave signal onto theelectron beam
Answer:Input Cavity
Question:Enhances the velocity modulation
Answer:Intermediate cavity
Question:Extracts microwave power from the bunched
electron beam Answer:Output cavity
Question:Collects the electron beam after microwavepower has been extracted from it
Answer:Beam collector
Question:Provides interaction between the microwavesignal and the electron beam in order to
generate microwave power Answer:Microwave interaction structure
Question:What type of magnetic focusing is mostcommonly used in a TWT?
Answer:Periodic permanent magnet (PPM) focusing
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Question:What is the advantage of a helix interactionstructure over a coupled cavity interactionstructure?
Answer:Wide Bandwidth
Question:What is the advantage of a coupled-cavityinteraction structure over a helix interactionstructure?
Answer:High Power
Question:What is the purpose of a depressed collector ina TWT?
Answer:To increase efficiency Question:What is the difference in function of themagnetic field in a TWT and in a CFA?
Answer:The magnetic field in a TWT is used only tofocus the electrons through the tube.The magnetic field in a CFA is part of thecrossed-field interaction process that allowshigh efficiency to be obtained.
Question:A separate electron gun is not used in anemitting-sole CFA, but the sole electrode whichprovides the crossed electric field, alsoprovides the electron beam.
Answer:
Emitting-sole CFA
Question:A magnetron is a high power oscillator tube.
Answer:Magnetron
Question:A microwave relay system that starts with thebaseband signal in the transmitter andmodulates this signal onto the microwavecarrier, receives the modulated microwavecarrier, and, after amplification, demodulates
the carrier to obtain the baseband signal at thereceiver.
Answer:Baseband microwave radio
Question:A technique for combining severaltransmitters, each operating in a differentfrequency channel, into a commontransmission line so that all the transmitters
can be connected to the same antenna. RFmultiplexing can be used in the same way toconnect several receivers to the samereceiving antenna?
Answer:RF multiplexingQuestion:A microwave relay repeater that receives themodulated microwave carrier and obtains thebaseband signal from it, and then remodulatesthe baseband signal onto another carrier andretransmits the new carrier with the basebandmodulated onto it.
Answer:Baseband repeater
Question:A microwave relay repeater that receives themodulated microwave carrier, amplifies it atthe IF frequency without removing thebaseband information and then up-convertsthe IF frequency to a new microwavefrequency for retransmission.
Answer:Heterodyne repeater
Question:A microwave relay repeater that amplifies thereceived microwave signal at the microwavefrequency and retransmits it withoutconverting the received signal to IF orbaseband frequencies.
Answer:RF amplifier
Question:
A repeater for digital signals that receives thenoisy digital bit stream and reconstructs it sothat a perfectly timed series of perfectlyshaped digital pulses is retransmitted
Answer:Regenerative repeater
Question: The ratio of the area of a one squarewavelength antenna to the area over which thetransmitted power has been spread (which is asphere with a radius equal to the transmitterreceiver separation)
Answer:Free-space path loss
Question: The reduction of the received signal in amicrowave relay due to the signal from amultipath being out-of-phase and canceling thedirect transmitted signal.
Answer:Multipath fading
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Question:A technique for reducing multipath fading bytransmitting the same information in twofrequency channels. This technique is based onthe fact that if a fade occurs at one frequencyit will not occur at the same instant of time ata different frequency.
Answer:Frequency diversity
Question:A technique for reducing multipath fading inwhich two receivers spaced approximately 100wavelengths apart, are used. This technique isbased on the fact that if a signal fades at oneantenna it will not fade at the same instant of time at the other antenna, since the pathlengths are different.
Answer:Space diversity
Question:A microwave relay system that achievestransmission distances beyond the curvatureof the earth by diffracting the microwavesignal off of hills and other obstacles in themicrowave path
Answer:Diffraction microwave relay system
Question:A microwave relay system that achievestransmission distances beyond the curvatureof the earth up to several hundred miles, byreceiving the microwave signal scattered fromair masses and clouds in the troposphere.
Answer:Troposcatter microwave relay system
Question:A transmission system used to send telephone,video, and data between buildings located a
few hundred feet to a few miles apart. Answer:Local area network
Question: Those microwave relay frequencies allocatedto long distance telephone companies for thetransmission of telephone, video and data forany customer.
Answer:
Common carrier frequency band
Question:A microwave relay that sends radio andtelevision program material from a distantlocation to the studio and from the studio tothe transmitter
Answer:Studio transmitter link
Question: The dividing of the common carrier or othermicrowave relay bands into channels. Separatetransmitters and receivers are used for eachchannel. The channel typically 20 MHz widecan handle 1000 telephone calls or onetelevision program.
Answer:Channelization of bandwidth
Question:A technique for transmitting differentinformation at the same frequency and in thesame direction from a microwave relaytransmitter to a receiver by using twopolarizations of the transmitted microwavefields.
Answer:Dual polarizationQuestion:Why is microwave relay often called aterrestrial microwave relay?
Answer:Because it is located on the surface of theearth.
Question:Why is microwave relay often called a line-of-sight relay?
Answer:Because the microwave signal travels inapproximately a straight line from thetransmitter to the receiver.
Question:What are the frequency ranges of the threemost commonly used common carrierfrequency bands?
Answer:
3.7 – 4.2 GHz; 5.925 – 6.425 GHz; 10.7 – 11.7GHz
Question:What is the frequency range of the mostcommon industrial relay band?
Answer:6.575 – 6.875 GHz
Question:
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What two frequency bands are most oftenused for local area microwave networks?
Answer:18.58 – 19.16 GHz; 21.2 – 23.6 GHz
Question:What are the typical transmitter-receiverspacings for microwave relay?
Answer:10 – 50 mi
Question:What limits the transmitter-receiver spacingfor a microwave relay?
Answer:The curvature of the earth
Question:An antenna covering that the transmitted orreceived microwave power can pass throughused to protect the antenna and the antennafeed from weather.
Answer:Radome
Question:A microwave relay antenna consisting of ahorn that radiates onto a reflector. It is madeas a single unit and has lower sidelobes than aparabolic dish antenna.
Answer:Horn-reflector antenna
Question:What carrier-to-noise ratio is required formicrowave relay systems?
Answer:10-20 dB
Summary on Antenna
Question: The amount by which an antenna concentratesits radiation in a given direction relative towhat would have been obtained if the antennahad not been used
Answer:Gain
Question: The effective area of the antenna for receivingmicrowave power
Answer:
Receiving area
Question: The angular width of the antenna beambetween the points on either side of the axiswhere the transmitted power has beenreduced by one-half
Answer:Beamwidth
Question: The direction of the electric field in theelectromagnetic wave radiated from anantenna. May be horizontal, vertical or circular
Answer:Polarization
Question: The frequency range over which an antennahas the required gain, area, or othercharacteristics.
Answer:Bandwidth
Question:Radiation from an antenna at other anglesthan the desired direction
Answer:Sidelobes
Question:A measure of the microwave power radiatesfrom an antenna as a function of angulardirection from the antenna axis
Answer: Antenna pattern
Question:A hypothetical antenna radiating or receivingequally well in all directions
Answer:Isotropic antenna
Question:What is the gain of an isotropic antenna?
Answer:0 dB
Question:What is the purpose of a phased array radar?
Answer:To move the antenna beam without movingthe antenna
Question:How far apart must the antenna elements of aphased array radar be placed?
Answer:
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½ wavelength
Question: The total transmitted power is radiated from afeed horn onto the array surface. The phase isshifted at each element of the array andreflected to form the beam
Answer:Reflected array
Question: The total transmitted power is radiated from afeed horn onto the array surface. The phase isshifted at each element of the array andtransmitted out the other side.
Answer:Lens array
Summary on Principles onCommunications
Question: The electrical signal to be transmitted. Thiselectrical signal may represent audio, video ordigital data
Answer:Baseband
Question: The electrical signal used to carry thebaseband information from one location toanother.
Answer:
Carrier
Question:Variation of the carrier amplitude, frequency,or phase by the baseband signal, so that thebaseband signal can be transmitted via thecarrier.
Answer:Modulation
Question:Removal of the baseband information from thecarrier at the receiving end, so that the
baseband signal can be used. Answer:Demodulation
Question:Modulation of the baseband onto the carrier byvarying the frequency
Answer:
Frequency Modulation (FM)
Question:Modulation of the baseband signal onto thecarrier by varying the amplitude
Answer: Amplitude Modulation (AM)
Question:Frequencies present in the amplitudemodulated or frequency modulated carrier dueto the modulation process.
Answer:Sidebands
Question: The frequency range over which themodulation sidebands exist.
Answer:Bandwidth
Question:An amplitude modulation process where thecarrier and one set of modulation sidebandsare removed to reduce bandwidthrequirements
Answer:Single-Sideband (SSB)
Question:A method of combining several signals, all of which occupy the same frequency range, into abaseband so that they do not interfere eachother.
Answer:Multiplexing
Question:A multiplexing technique where each signal tobe multiplexed is shifted from its originalfrequency and then combined.
Answer:Frequency-division Multiplexing (FDM)
Question: The baseband signal is sampled in time, andeach sample is represented by a digital code.
Answer:Pulse Code Modulation (PCM)
Question:A multiplexing method where several signalsare combined by forming PCM codes of eachand then interleaving the PCM pulses.
Answer:Time-division multiplexing (TDM)
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Question: The ratio of the received microwave carrier tothe microwave noise in the receiver
Answer:Carrier-to-noise ratio (C/N)
Question: The ratio of the received signal to noise afterthe signal has been demodulated to get outthe baseband information.
Answer:Signal-to-noise ratio (S / N)
Question: The frequency range of a single telephonesignal is from _____ Hz to ____ Hz.
Answer:300 – 3400 Hz
Question:A single telephone signal is fitted into afrequency band from ___ Hz to ____ Hz.
Answer:0 – 4000 Hz
Question:How many telephone signals are frequency-division-multiplexed together to form an FDMgroup?
Answer:12
Question:What is the frequency range of an FDM basicgroup?
Answer:60 - 108 kHz
Question: The frequency range of a single TV signal from ____ to ___ MHz Answer:0 – 4 Mhz
Question:How many digital bits are required for a singleletter in an asynchronous ASCII code withparity?
Answer:10
Question:What signal-to-noise ratio is required forsatisfactory telephone service?
Answer:50 dB
Question:
What signal-to-noise ratio is required forsatisfactory telephone reception?
Answer:40 dB
Question:Coding of an analog signal into a series of digital pulses is called _____.
Answer:Pulse code modulation (PCM)
Question: The combining of many telephone signalstogether by first coding each into a series of digital pulses and then interleaving the pulsesseries of each signal is called ______.
Answer:Time-division multiplexing (TDM)
Question:What must be the PCM sampling rate on a 4-kHz analog signal?
Answer:8 kHz
Question:What is the quantization signal-to-noise ratio if an eight-digit PCM code is used?
Answer:50 dB
Question:What is the digital bit rate for a standard PCMtelephone channel?
Answer:64 kb/s
Question: The changing of digital signals from acomputer into frequency tones fortransmission down a conventional voice gradetelephone circuit is done in a _____.
Answer:Modem
Question:What is the advantage of FM compared withAM?
Answer:
Signal-to-noise improvement
Question:What is the advantage of FM compared withFM?
Answer:Less transmission bandwidth required
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Summary on SatelliteCommunications
Question:A satellite communication system designed forcommunication from one continent to another.
Answer:
International satellite
Question:A satellite communication system designed forcommunicating within a given continent orgeographical area, such as the United States.
Answer:Domestic satellite
Question:A satellite system designed for ship-to-shorecommunication.
Answer:MARISAT
Question:A satellite communication system designed tobroadcast television directly from the satelliteat a home TV receiver.
Answer:Direct broadcast satellite
Question: The orbit of satellites around the earth’sequator in which the satellite takes 24 h to
completely orbit the earth, so that the satelliteappears in a stationary location relative to therotating earth.
Answer:Synchronous orbit
Question:It is the effective radiated power of thesatellite transmitter. It is equal to the productof the transmitter power times the transmitterantenna gain, and this single quantitycompletely characterizes the satellitetransmitter.
Answer:ERP
Question:Completely characterizes the earth stationreceiver of a satellite communication system,and is equal to the ratio of the receiverantenna gain to the total noise temperature of the receiver (including the antenna noise
temperature plus the receiver amplifier noisetemperature).
Answer:G/T
Question:A satellite that maintains its orientation inspace relative to the earth by spinning aboutits axis at a rate of about 50 revolutions perminute
Answer:Spin-stabilized satellite
Question:A satellite that maintains a fixed orientation inspace relative to the earth by continuallycorrecting its orientation by firing small jets
Answer:Three-axis stabilized satellite
Question:A single channel of the communication systemEach transponder in a satellite has its ownseparate transmitter. It is typically 40 MHzwide
Answer:Transponder
Question:Received power contours from satellite on theearth’s surface. The satellite antenna isdesigned, often with multiple feed horns, to
direct its power onto particular geographicareas, and this pattern of received power onthe earth’s surface is the antenna footprint.
Answer: Antenna footprint
Question:An antenna beam from the satellite that coversthe entire one third of the earth’s surface thatcan be seen from the satellite
Answer:Global beam
Question: The antenna beam from the satellite thatcovers a limited geographic region, such aspart of a country, an entire country, acontinent, or a hemisphere. Some satelliteshave a variety of spot beams, each covering alarger or smaller geographic area.
Answer:Spot beam
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Question:What is the synchronous orbit for acommunication satellite in miles?
Answer:22,300 mi
Summary on RADAR
Communications
Question:A radar that measures the distance betweenthe radar and a target by determining the timerequired for a microwave signal to travel fromthe radar to the target and back.
Answer:Range-measuring radar
Question:A radar that measures the velocity of a target
by determining the change in the frequency of the reflected microwave signal due to thetarget’s velocity. This change in frequency iscalled the Doppler’s shift, and so this type of radar is often called a Doppler radar.
Answer:Velocity-measuring radar
Question:A radar that measures both the distance to a
target and its velocity by measuring both thechange in frequency of the reflected signal andtime required for the microwave signal totravel from the transmitter to the target andback to the radar.
Answer:Pulse Doppler radar
Question:A radar that measures the range to the targetand distinguishes between moving andstationary targets.
Answer:
Moving-target-indicator (MTI) radar
Question:A radar that obtains high range resolution byvarying the frequency of the transmittedmicrowave signal and then compresses thepulse in the receiver.
Answer:Pulse-compression radar
Question:A radar that scans its beam over a givenvolume of space to determine if targets arepresent.
Answer:Search radar
Question:A radar that directs its beam into a given areaof space to determine accurately the angularlocation of a target.
Answer:Tracking radar
Question:A tracking radar that determines the angularlocation of a target with a single pulse.
Answer:Monopulse radar
Question:A radar that moves its beam through space bychanging the phase of a multiplicity of transmitting elements that make up theantenna rather than mechanically moving theentire antenna.
Answer:Phased array radar
Question:A radar using a single antenna element, whichobtains extremely high angular resolution bymoving this single element over a longdistance, storing the information obtained fromthe antenna at each position, and thenrecombining the received information.
Answer:Synthetic Aperture radar
Question:What three things can a radar measure?
Answer:Range; velocity; angle (azimuth and elevation)
Question:Which of the following can radar measure withthe best accuracy?
Answer:Velocity
Question:Which of the above are the most difficult for aradar to measure accurately?
Answer: Angle
Summary on RADAR Warfare
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Question:A radar has a transmitter power of 10 kW, anarea of 10 m2, a gain of 40 dB, and the rangebetween the radar and the target is 100 km.
The target cross section is 100 m2, the totalatmospheric and system losses are 4 dB,(2.5times) the receiver noise figure is 2 dB, andthe bandwidth is 1 MHz.
Answer:26 dBSolution:
( )
( ) ( ) ( ) ( )
( ) ( ) ( )
R 2 4
4 4 2 2 2
42 5
R
PGσAP
4π R L
10 W 10 10 m 10 m
4π 10 m 2.5
2.5 pW
86 dBm
N 114 2 2.5 112
P 26 dBN
=
=
=
= −
= − + + = −
∴ =
Question: The techniques, equipment, and tactics usedto render electronic target location andelectronic weapons control ineffective.
Answer:Electronic Warfare (EW)
Question: The techniques and equipment used to render
electronic target location and weapon controlineffective. It include tactics such as flightplans to avoid detection, electronicsurveillance, spying techniques to determinehow enemy weapon systems work and theirdeployment, and the jamming of infrared,optical, and radar target location and controlsystems.
Answer:Electronic Welfare
Question: The electronic techniques and equipment usedto render electronic target location andelectronic weapons control ineffective.
Answer:Electronic Countermeasures (ECM)
Question:
It is sometimes used interchangeably with theterm electronic warfare. In the strict sense,electronic countermeasures applies only totechniques and equipment used to renderelectronic target location and weapon controlsystems ineffective.
Answer:Electronic countermeasure
Question: These are the techniques an equipment usedby the radar to reduce the effectiveness of theenemy’s jamming against it.
Answer:Electronic counter-countermeasures (ECCM)
Question: Techniques and equipment used by the radarto render ECM ineffective.
Answer:Electronic Counter-Countermeasures (ECCM)
Question:Are the equipment used to determine theelectronic characteristics of the enemy targetlocation and weapon control systems, and todetermine what should be jammed by theelectronic countermeasures.
Answer:Electronic support measures (ESM)
Question: The equipment used to determine thecharacteristics of the enemy’s electronic targetlocation and electronic weapons controlsystem.
Answer:Electronic Support Measures (ESM)
Question:Aircraft are specially designed to reduce theamount of microwave power they reflect sothat they cannot be seen by radar.
Answer:Stealth
Question:It is an electronic countermeasure technique inwhich the aircraft is completely redesigned to
greatly reduce its radar cross section. Answer:Stealth
Question:A missile is launched by the target to home onthe microwave signal transmitted by the radar
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This forces the radar to shut down or bedestroyed.
Answer: Anti-radiation missile
Question:An anti-radiation missile uses the radartransmissions as a beacon and homes on theradar to destroy it.
Answer: Anti-radiation missile (ARM)
Question:A metal foil dropped from an aircraft orlaunched from a ship or land vehicle thatreflects a microwave signal back to the radarto create false targets.
Answer:Chaff
Question:Is a metal foil launched from a target to createfalse radar target
Answer:Chaff
Question:Is another name for barrage jamming, andstresses that the barrage jamming sourcemust be out of the range of enemy missiles sothat they cannot home on the jamming.
Answer:Stand-off jamming
Question:Is the repeating back of an amplified version of
the radar signal with its characteristicschanged to give false information to the radar.
Answer:Deceptive jamming
Question: The jammer repeats an amplified version of the radar signal, but with false information.
The radar determines the range, velocity, andangular location of the target with this falseinformation.
Answer:Deceptive Jamming
Question:Are small missiles with amplifiers in them.
They receive and amplify the radar signal andtransmit it back to the radar, so that they looklike targets.
Answer:Decoys
Question:
Is a small unarmed missile launched fromaircraft, or a buoy launched from ships, tocreate false radar targets
Answer:Decoy
Question:Noise-modulated microwave signals aretransmitted to raise the noise level in the radarreceiver so that the radar cannot accuratelydetermine the range, velocity, or angularlocation of the target. The technique isdangerous because the enemy can launchmissiles that home on the jamming signal.
Answer:Noise Jamming
Question:A deceptive jamming technique where thereceived radar signal is amplified and sentback to the radar delayed in time from theactual reflected radar signal so that the radarthinks the target is further away that is reallyis.
Answer:Range-gate pull-off (RGPO)
Question:A deceptive jamming technique where the
jamming pulse is sent to the radar before theactual echo from the target so that the radarthinks that the target is closer to the radar thatit really is.
Answer:Range-gate pull-in (RGPI)
Question:A deceptive jamming technique where the
jamming signal is given a false Doppler shift sothat the radar thinks the target velocity isdifferent than it really is.
Answer:Velocity-gate pull-off (VGPO)
Question:A deceptive jamming technique where theradar is transmitted with an amplitudevariation that is out of phase with the conical
scan information so that the radar thinks thatthe target is a different angular location.
Answer:Inverse conical-scan jamming
Question:Is the transmission of noise-modulated highpower microwave power microwave signals toraise the noise level in the enemy radar
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receiver so that range and velocity informationcannot be obtained.
Answer:Barrage jamming
Question:A ECCM technique where the radar launches amissile to home on the barrage jamming ordeceptive jamming signal. The jammer thenserves as a beacon to guide the attackingmissile to it.
Answer:Home-on jammer
Question:An ESM receiver consisting of many mixer-localoscillator-IF amplifiers in parallel toinstantaneously determine the frequency of the radar signals.
Answer:Channelized receiver
Question:An ESM receiver using optoacoustical effects toinstantly determine the time of arrival and thefrequency of the radar signals
Answer:Bragg Cell
Summary on Microwave
CommunicationsQuestion:What is the microwave transmission frequencyof GPS satellites?
Answer:1.575 GHz
Question:What is the frequency range of cellulartelephones?
Answer:806 – 949 MHz
Question:What is the frequency of microwave ovens?
Answer:2.450 GHz
Question:Operating frequency for UHF TV
Answer: 600 MHz
Question:Operating frequency for microwave relay
Answer: 3.9 GHz
Question:Operating frequency for satellitecommunication
Answer: 6 GHz (up)4 GHz (down)
Question:Operating frequency for troposcattercommunication
Answer: 2 GHz
Question:Operating frequency for mobile radio
Answer: 900 MHz
Question:Operating frequency for telemetry
Answer: 2 GHz
Question:What two problems prevent conventionalelectronic equipment from working atmicrowave frequencies?
Answer: Lead Reactance and Transmit Time
Question:What are the three types of microwavetransmission lines?
Answer: Coaxial cable; stripline; waveguide
Question:Determine the guide wavelength at 3 GHz for a50-Ω stripline using 0.03-in.-thick Teflon
fiberglass (ε = 2.55). Answer:6.26 cm
Solution::
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( ) ( )
0
0g
Zε 50 2 .55 79 .8 Ω
w0.75
b
w 0.75 2 x 0.03 0.045 in.
Then,
λλ
ε
10 cm
2.556.26 cm
= =
=
= =
=
=
=
Summary on Latest ECE Laws
Question:An executive order which gave NTC a vestedpower to promulgate rules and regulations, aspublic safety interest may require, toencourage as larger and more effective use of communications, radio and televisionbroadcasting facilities, and to maintain
effective competition. Answer:E.O. 546
Question: The maximum frequency separationrequirement for FM broadcast stations.
Answer:800 kHz
Question: The maximum number of low power FM radiobroadcast stations be allowed for any
geographical region. Answer:30
Question: The maximum number of low power FM radiobroadcast stations may be operated/allowed tobe established nationwide.
Answer:200
Question:All classes of FM stations shall be protected up
to protected up to _____ or _____. Answer:1 mV/m or 60 dBu contour
Question:NTC memorandum circular on the guidelinesfor the grant and authorization of 500 watts FMbroadcast stations.
Answer:M.C. 02-06-2006
Question:Consider as low power FM Broadcast Station.
Answer:500 W. FM Broadcast stations
Question:Authorized transmitted power output for classB-1 FM station.
Answer:500 W
Question:Class B-1 FM station
Answer:ERP: not lower 1 kW and not exceeding 5 kW
Antenna height: limited to 200 feet aboveaverage terrain
Question:Class B Station
Answer: Authorized power transmitter power of not exceeding 10 kW ERP: not exceeding 30 kW
Antenna Height: limited to 500 feet aboveaverage terrainMinimum TXR Power: 1 kW
Question:National Telecommunication CommissionMemorandum Circular which pertains toprogram standards for radio and TV Broadcastand Cable TV stations.
Answer:M.C. 1-3-2006
Question:A Memorandum Circular issued by NTC inrelation to the “use and operation of radiofrequency identification (RFID)”.
Answer:M.C. 03-08-2006
Question: The RFID frequency range Answer:13.553 – 13.567 MHz 918 – 920 MHz 2446 – 2454 MHz
Question: These are intended to carry data in suitabletransponders, generally known as tags, and to
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retrieve data, by hand-or-machine-readablemeans, at a suitable time and place to satisfyparticular application needs.
Answer:Radio Frequency Identification System
Question:It employs time chips and wireless antennasthat can be embedded into products and usedfor unique identification purposes.
Answer:RFID
Question:A device which transmits aninterrogating/querying signal to an RFID tagand receives unique information from the tag
Answer:Proximity readers
Question:Classification of proximity reader with erp notexceeding 500 mW.
Answer:Low power
Question:Class of Proximity with erp not exceeding 2watts (or 4 watts eirp)
Answer:High power
Question:A microchip attached to an antenna that picksup signals from and sends signals to a reader
Answer:
RFID tag
Question:Class of RFID used for long distance purposessuch as in toll highways, parking areas, andgas stations.
Answer: Active tag
Question:Class of RFID used for near and in closeproximity to a reader and does not use anyinternal battery.
Answer:Passive tags
Question: The Electronics Engineering Law of 2004 Answer: R.A. 9292
Question:Date signed into Law by President GloriaArroyo.
Answer: April 17, 2004
Question:Date the R.A. 9292 published at Manila Times
Answer: May 12, 2004
Question:Date the Electronics Engineering Law of 2004takes effective
Answer: May 27, 2004
Question:Penalty for operating Radio FrequencyIdentification (RFID) proximity reader withoutvalid registration
Answer: P5,000 per reader
Question:Penalty for selling unregistered RFID proximityreader
Answer:P5,000 per unit or with forfeiture of equipment
Question:Penalty for selling of RFID proximity readers bynon-NTC accredited radiodealers/manufacturers
Answer:P5,000 per reader, P1,000 per 1000 tags
Question:Registration fee for low power readers
Answer:P100
Question:Registration fee for high power readers
Answer:P300
Question:A low power RFID readers has an ERP of _____.
Answer:Not exceeding 500 mW
Question: A high power RFID readers has an ERP of ____. Answer:Not exceeding 2 watts (or 4 watts EIRP)
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Question:FM Broadcast Stations which are allowed tooperate in Established Service Areas
Answer:Class A or Class B FM Broadcast Stations
Question:FM Broadcast Stations which are allowed tooperate in areas outside of the EstablishmentService Area
Answer:Class B-1
Question:Broadcast/Push messaging services shall notbe sent between _____ except on paidsubscription services based on NTCrecommendation.
Answer:9:00 pm – 7:00 am
Question:Penalty for violating rules and regulations onBroadcast Messaging Services set by NTC
Answer:P200 fine per violation