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WorksheetsGROUP STUDY - MICROWAVES
Total questions: 100
Worksheet time: 50mins
The skin effect causes the current to flow
At the center of the conductor
Through the central core of the conductor
near the surface of the conductor
uniformly through the conductor
The angle between the electric and magnetic fields in a waveguide is
90 degrees
0 degrees
180 degrees
360 degrees
Materials generally preferred for waveguides are
Brass and Aluminum
Non metallic solids including plastic
cast iron and steel
high carbon steel and vanadium steel
A 2.5 cm x 1.5 cm rectangular waveguide is to be used at 9GHz. It's group and phase velocities are
2.23 x 10exp8 m/sec, 4.025 x 10exp8 m/sec
4.025 x 10exp8 m/sec, 2.23 x 10exp8 m/sec
4.025 x 10exp8 m/sec, 2.23 x 10exp8 m/sec
2.01 x 10exp8 m/sec, 4.47 x 10exp8 m/sec
A microwave transmission line constructed of a center conductor suspended between parallel conductive ground planes
Microstrip
coax
stripline
waveguide
A microstrip is analogous to
Balun
waveguide
flattened coaxial line
none of these
Which microwave tube uses buncher and catcher cavities?
Magnetron
Klystron
Reflex Klystron
TWT
An X band radar operates in which frequency band?
1 – 2GHz
2 – 4 GHz
4 – 8 GHz
8 – 12 GHz
To offset fading, two or more receiving antennas are used, separated by several wavelengths, This scheme is ______ diversity
Frequency
space
polarization
angle
What is the method of diversity reception where the signal is transmitted on 2 different frequencies over the same path?
Quadrature
Frequency
Polarization
Space
An elliptical zone between two microwave antennas, where the total path distance nowhere varies by more than half of the operating wavelength.
Skip zone
Fresnel zone
Optimum Zone
Dillinger zone
The k factor under normal atmospheric conditions in a microwave radio data profile calculation is equal to
2/3
0
4/3
1
For a reliability of 99.99%, the recommended fade margin is
28 dB
38 dB
48 dB
58 dB
A microwave system has a downtime of 30 minutes in a year. What is its system reliability?
99.9359%
70.696%
99.9943%
99.9992%
A microwave transmitter has an EIRP of 75 dBm. Its radio equipment provides 1 w of power and it has 5dB transmission losses. What is the radius of the transmitting antenna for 8 GHz signal?
2.55 m
1.275m
4.54m
2.27m
What is the free space loss, in dB, if a microwave system when the frequency is 6GHz at 40 km apart?
140 dB
150 dB
160 dB
170 dB
When the value of k increases, the effective result is _____ of the equivalent curvature.
Downward
flattening
bulging
sharp
Occurs when the microwave is at the point of grazing over an obstacle.
Diffraction
refraction
absorption
reflection
It represents the average period of time the unit will operate without failure, considered over an indefinite long period of time.
MTBF
MTTR
MTBS
MTTS
A rectangular waveguide is 5.1 cm by 2.4 cm. The cut off frequency for the dominant mode is
2.94 GHz
6.25 GHz
664 MHz
57.7 GHz
Determine the gain of a 6ft parabolic dish operating at 1800 MHz.
30 dB
11.2 dB
15.5 dB
28.17 dB
A mode where the magnetic field is perpendicular to the direction of propagation.
TE
TM
TN
TG
This type of transmission permits communication in the frequency range from 30 to 60 MHz and over distances from 1000 to 2000 km.
Troposcatter
ionospheric scatter
ducting
microwave
In order to ensure free space propagation, it is essential that all potential obstructions along a path are removed from the beam centerline at least ____ of F1.
0.2
0.3
0.4
0.6
Radio frequency where waveguide is not used extensively.
150 MHz
2000 MHz
3750 MHz
10.3 GHz
By how much should two antennas be separated for space diversity in the 11 GHz band?
5.5 m
7.5 m
9.5 m
11.5 m
What is the phase velocity of a rectangular waveguide with a wall separation of 3 cm and a desired frequency of operation of 6 GHz?
3.45 x 10^8 m/s
4.35 x 10^8 m/s
4.53 x 10^8 m/s
5.43 x 10^8 m/s
A transmitter and a receiver is 45 km apart. Suppose that there is an obstacle midway between the transmitter and receiver. By how much must the path between the towers clear the obstacle in order to avoid diffraction at a frequency of 11 GHz?
17.52 m
10.51 m
8.76 m
7.52 m
How far from the transmitter could a signal be received if the transmitting and receiving antennas where 40 m and 20 m, respectively, above level terrain?
44.5 km
45.4 km
54.4 km
None of the choices
A signal propagated in a waveguide has a full wave of electric intensity change between two further walls, and no component of the electric field in the direction of propagation. The mode is
TE11
TE10
TM22
TE20
An isolator has a forward loss of 0.7 dB and a return loss of 26 dB. A source provides 1 W to the isolator, and the load is resistive with an SWR of 3. How much power is dissipated in the load?
1 W
851 mW
750 mW
638 mW
An isolator has a forward loss of 0.7 dB and a return loss of 26 dB. A source provides 1 W to the isolator, and the load is resistive with an SWR of 3. How much power returns to the source?
250 mW
350 μW
535 μW
690 μW
It is a microwave device that allows RF energy to pass through in one direction with very little loss, but absorbs RF power in the opposite direction.
multiplexer
circulator
isolator
wave trap
A metal wrapped around the parabolic antenna aperture to eliminate sidelobes interfering nearby stations is called
radome
shield
shroud
bass drum
The wavelength of a wave in a waveguide ________.
is greater than in free space
depends only on the waveguide dimensions and the free space wavelength
is inversely proportional to the phase velocity
is directly proportional to the group velocity
At a frequency of 1 GHz and transmitter-receiver distance of 30 mi, which is the most efficient device for energy transfer?
Transmission lines
Waveguides
Antennas
None of the above
The most efficient means of transmitting a 1-Ghz signal 1500 ft would typically be
Transmission lines
Waveguides
Antennas
None of the above
The dominant mode for waveguide operation is
TE10
TE01
TM10
TM01
The propagation velocity of the signal in a waveguide, when compared to the speed of light is
larger
smaller
the same velocity
either b or c
Ridged waveguides are advantageous over rectangular waveguides in their
cost
attenuation
ability to work at lower frequency
ease of construction
A circular waveguide is used for
Efficiency reasons
Ease of manufacture
Rotating section applications
Greater bandwidth
Variable attenuators are used in waveguides to
Isolate a source from reflections at its load so as to preclude frequency pulling.
Adjust the signal levels.
Measure signal levels.
All the above.
The coupling in dB of a directional coupler that has 85 mW into the main guide and 0.45 mW out the secondary guide is
22.8
18.9
188.9
45.6
The resonant frequency of a cavity may be varied by changing the cavity's
Volume
Inductance
Capacitance
All the above
The guide wavelength is
Greater than free-space wavelength
Equal to free-space wavelength
Less than free-space wavelength
All the above
The process of employing radio waves to detect and locate physical objects is known as
The Doppler effect
Radar
Directional coupling
Cavity tuning
The use of two grounded conductors that sandwich a smaller conductive strip with constant separation by a dielectric material on a printed circuit board for use at frequencies above 500 MHz is known as
Artwork traces
Dielectric waveguide
Microstrip/stripline
MICs or MMICs
Second return echoes are
Echoes produced when the reflected beam makes a second trip
Echoes that arrive after the transmission of the next pulse
Echoes caused by the PRT being too long
All the above
The characteristic wave impedance for waveguides is
377 Ω
Dependent on frequency
Dependent on waveguide shape
b and c
A dielectric waveguide is
Enclosed by a conducting material
A waveguide with just a dielectric
Dependent on the principle that two dissimilar dielectrics can guide waves
b and c
Which is not a type of horn antenna design for microwave frequencies?
Parabolic horn
Circular horn
Pyramidal horn
Sectoral horn
Cassegrain feed to a paraboloid antenna involves a
Dipole antenna
Point-source antenna
Secondary reflector
Any of the above
Calculate the beamwidth of a microwave dish antenna with a 6-m mouth diameter when used at 5 Ghz
0.49°
4.9°
7°
0.7°
Zoning refers to
A method of producing a radome
Changing a spherical wavefront into a plane wave
Creating a polar radiation pattern
Fading into nonreality
Which microwave oscillator has high gain, low-noise characteristics, and wide bandwidth?
Traveling wave tube oscillator
Gunn Oscillator
Klystron oscillator
Magnetron oscillator
Which is not an advantage of the Gunn gallium arsenide oscillator?
Ease of removing heat from the chip
Small size
Ruggedness
Lack of filaments
The I in P-I-N diode refers to
Indium
Impact
Integrated
Intrinsic
Which is not a typical application of a ferrite in a microwave system?
attenuator
amplifier
isolator
circulator
A low noise microwave amplifier that provides amplification via the variation of a reactance is known as a
Maser
Laser
Yig
Parametric amplifier
The major difference between a laser and a maser is the
Frequency of the signal being amplified
Amplitude of the signal being amplified
Bandwidth of the signal being amplified
Phase of the signal being amplified
Lasers are useful in
Industrial welding
Surgical procedures
Distance measuring
All the above
The following semiconductor is not used as a microwave device:
PIN diode
Baritt diode
Zener diode
Tunnel diode
Which of the following represent typical failure mode(s) for a TWT amplifier?
Low gain
Spurious modulation
Poor frequency response
All the above
Which of the following is not used as a microwave antenna?
Patch antenna
Marconi antenna
Lens antenna
Horn antenna
Compared to linear power supplies, switching power supplies are
Less efficient
More efficient
Simpler
Heavier
When an electromagnetic waves are propagated in a waveguide
they travel along a broader walls of the guide
they are reflected from the walls but do not travel along them
they travel through the dielectric without touching the walls
they travel along all four walls of the waveguide
Waveguides are used mainly for microwave signals because
they depend on straight-line propagation which applies to microwaves only
losses would be too heavy at lower frequencies
there are no generators powerful enough to excite them at lower frequencies
they would be too bulky at lower frequencies
The wavelength of a wave in a waveguide
is greater than of free space
depends only on the waveguide dimensions and the free-space wavelength
is inversely proportional to the phase velocity
is directly proportional to the group velocity
The main difference between the operation of transmission lines and waveguides is that
the latter are not distributed, like transmission lines
the former can use stubs and quarter-wave transformers, unlike the latter
transmission lines use the principal mode of propagation, and therefore do not suffer from low-frequency cut-off
terms such as impedance matching and standing-wave ratio cannot be applied to waveguides
Compared with equivalent transmission lines, 3-GHz waveguides (indicate false statement)
are less lossy
can carry higher powers
are less bulky
have lower attenuation
When a particular mode is excited in a waveguide, three appears an extra electric component, in the direction of propagation. The resulting mode is
transverse-electric
transverse-magnetic
longitudinal
transverse-electromagnetic
When electromagnetic waves are reflected at an angle from a wall, their wavelength along the wall is
the same as in free space
the same as the wavelength perpendicular to the wall
shortened because of Doppler effect
greater than in the actual direction of propagation
As a result of reflections from a plane conducting wall, electromagnetic waves acquire an apparent velocity greater than the velocity of light in space. This is called the
velocity of propagation
normal velocity
group velocity
phase velocity
Indicate the false statement. When the free space wavelength of a signal equals the cut-off wavelength of the guide
the group velocity of the signal becomes zero
the phase velocity of the signal becomes infinite
the characteristic impedance of the guide becomes infinite
the wavelength within the waveguide becomes infinite
The dominant mode of propagation is preferred with rectangular waveguides because (indicate false statement)
it leads to the smallest waveguide dimensions
the resulting impedance can be matched directly to coaxial lines
it is easier than the other modes
propagation of it without any spurious generation can be ensured
A choke flange may be used to couple two waveguides
to help in the alignment of the waveguides
because it is simpler than any other join
to compensate for discontinuities at the join
to increase the bandwidth of the system
In order to couple two generators to a waveguide system without coupling them to each other, one could not use a
Rat race
E-plane T
hybrid ring
magic T
Which of the following waveguides tuning components is not easily adjustable?
Screw
Stub
Iris
Plunger
A piston attenuator is a
vane attenuator
waveguide below cutoff
mode filter
flap attenuator
Cylindrical cavity resonators are not used with klystrons because they have
a. a Q that is too low
b. a shape whose resonant frequency is too difficult to calculate
c. harmonically related resonant frequencies
d. too heavy losses
A directional coupler with three or more holes is sometimes used in preference to the two-hole coupler
because it is more efficient
to increase coupling of the signal
to reduce spurious mode generation
to increase the bandwidth of the system
A ferrite is
a. a nonconductive with magnetic properties
b. an intermetallic compound with particularly good conductivity
c. an insulator which heavily attenuates magnetic fields
d. a microwave semiconductor invented by Faraday
Manganese ferrite may be used as a (indicate false answer)
circulator
isolator
garnet
phase shifter
The maximum power that may be handled by a ferrite component is limited by the
Curie temperature
Saturation magnetization
line width
gyromagnetic resonance
A PIN diode is
a. a metal semiconductor point-contact diode
b. a microwave mixer diode
c. often used as a microwave detector
d. suitable for use as a microwave switch
A duplexer is used
to couple two different antennas to a transmitter without mutual interference
to allow the one antenna to be used for reception or retransmission without mutual interference
to prevent interference between two antennas when they are connected to a receiver
to increase the speed of the pulses in pulses in pulsed radar
For some applications, circular waveguides may be preferred to rectangular ones because of
the smaller cross section needed at any frequency
lower attenuation
freedom from spurious modes
rotation of polarization
Indicate which of the following cannot be followed by the word "waveguide":
Elliptical
Flexible
Coaxial
Ridged
In order to reduce cross-sectional dimensions, the waveguide to use is
circular
ridged
rectangular
flexible
For low attenuation, the best transmission medium is
flexible waveguide
ridged waveguide
rectangular waveguide
coaxial line
A microwave tube amplifier uses an axial magnetic field and a radial electric field. This is the
reflex klystron
coaxial magnetron
traveling-wave magnetron
CFA
One of the following is unlikely to be used as a pulsed device.
multicavity klystron
BWO
CFA
TWT
One of the reasons why vacuum tubes eventually fail at microwave frequencies is that their
noise figure increases
transit time becomes too short
shunt capacitive reactances become too large
series inductive reactances become too small
Indicate the false statement. Transit time in microwave tubes will be reduced if
the electrodes are brought closer together
a higher anode current is used
multiple or coaxial leads are used
the anode voltage is made larger
The multicavity klystron
is not a good low-level amplifier because of noise
has a higher repeller voltage to ensure a rapid transit time
is not suitable for pulsed operation
needs a long transit time through the buncher cavity to ensure current modulation
Indicate the false statement. Klystron amplifiers may use intermediate cavities to
prevent the oscillations that occur in two-cavity klystrons
increase the bandwidth of the device
improve the power gain
increase the efficiency of the klystron
The TWT is sometimes preferred to the multicavity klystron amplifier, because it
is more efficient
has a greater bandwidth
has a higher number of modes
produces a higher output power
The transit time in the repeller space of a reflex klystron must be n + ¾ cycles to ensure that
electrons are accelerated by the gap voltage on their return
returning electrons give energy to the gap oscillations
it is equal to the period of the cavity oscillations
the repeller is not damaged by striking electrons
The cavity magnetron uses strapping to
prevent mode jumping
prevent cathode back-heating
ensure bunching
improve the phase-focusing effect
A magnetic field is used in the cavity magnetron to
prevent anode current in the absence of oscillation
ensure that the oscillations are pulsed
help in focusing the electron beam, thus preventing spreading
ensure that the electrons will orbit around the cathode
