EST Essentials - Ch. 6: Microwave Communications

is the most versatile microwave RF power amplifier and it has an extremely wide bandwidth of operation

The microwave tube, TWT __________.

the shape of the waveguide

The dominant mode of a waveguide depends on __________.

physical size

Which of the following characteristics of a waveguide causes the lower-frequency limitation?

it is designed to operate with a high reverse bias that causes them to avalanche or breakdown

Which of the following describes the IMPATT diode?

the RF signal level impinging on the far end receiver antenna as if it were an isotropic antenna

IRL __________.

reflector

A helical antenna is made up of a coil and a __________.

is placed at a point of maximum electric field intensity

A probe __________.

average inland areas

A climatic factor of 0.25 is used for __________.

they form closed loops

H lines have which of the following distinctive characteristics?

it produces a narrow range of negative resistance when forward biased

Which of the following describes the tunnel diode?

of its circular symmetry

Circular waveguides use TM01 mode because __________.

increasing frequency of the input energy

The group velocity of a wavefront in a waveguide may be increased by which of the following actions?

antenna directivity

The ability of a radar to determine the bearing to a target depends upon the __________.

uses only one cavity resonator and it is gradually replaced by Gunn Diode

The microwave tube, reflex klystron __________.

both B and C:

B. depends on the frequency it carries;

C. depends on the longer dimension of its cross section

The characteristic impedance of a waveguide __________.

over average terrain

A roughness factor of 1 is used __________.

one

With a mode description of TE10, what maximum number of half-wave patterns exist across the "a" dimension of a waveguide?

speed

The Doppler Effect allows which characteristic of a target to be measured?

they are more efficient than their IMPATT counterparts but are noisier

Which of the following describes the TRAPATT diode?

all of the above:

A. with a magnetic field probe;

B. with an electric field probe;

C. through a hole in the waveguide

Power can be coupled into or out of a waveguide __________.

it is simply the level of signal at the receiving end of the transmission

RSL __________.

one

With the mode description, TE11, what maximum number of half-wave patterns exist across the diameter of a circular waveguide?

frequency

The Doppler Effect is a change in what signal characteristic produced by relative motion between the radar set and a target?

is placed at a point of maximum magnetic field intensity

A loop __________.

all of the above:

A. their insertion loss;

B. their coupling specification;

C. their directivity

Directional couplers for waveguides are characterized by __________.

each of the above:

A. slot

B. loop

C. probe

To inject or remove energy from a waveguide, which of the following devices could you use?

a microwave coupling device having a number of terminals so arranged that energy entering one terminal is transmitted to the next adjacent terminal in a particular direction

What is a circulator?

couple components on a circuit board

Striplines and microstrips are used to __________.

at the point of maximum magnetic field

Loop coupling is most efficient when the loop is placed at what point in which of the following fields?

extremely small and has a tiny junction capacitance

Which of the following describes the hot-carrier diode?

tuned circuit

A resonant cavity is a type of __________.

power-handling capability

Increasing the size of the loop wire increases which of the following loop capabilities?

horn and parabolic reflector

Most radar antennas use a __________.

this is a broadband VHF or UHV antenna that is ideally suited for applications for which radiating circular rather than horizontal or vertical polarized electromagnetic waves are required?

Which description below describes a helical antenna?

as a shunt resistance

A waveguide iris that covers part of both the electric and magnetic planes acts as what type of equivalent circuit at the resonant frequency?

used if change in polarization is needed

A waveguide twist __________.

is the rate at which the wave appears to move along the wall of the guide based on the way the phase angle varies along the walls

In waveguides, the phase velocity __________.

the noise sensitivity of the baseband detector

The receiver threshold is dependent on __________.

dummy load

A resistive device with the sole purpose of absorbing all the enegy in a waveguide without causing reflections is a/an __________.

to sample the energy in a waveguide

What is the primary purpose of a directional coupler?

reflected radio signals

Radar is based upon __________.

it does not have a PN junction

Which of the following describes the Gunn diode?

22 GHz

Which of the following is a microwave frequency?

produces an extremely high intensity reverse current pulse

Which of the following describes the step-recovery diode?

the transmitter uses two different frequencies and the receiver is tuned in either of the two frequencies

In frequency diversity, __________.

because electromagnetic fields are completely confined in coaxial lines

Coaxial lines are more efficient than two-wire lines at microwave frequencies for which of the following reasons?

mobile radio

Which of the following is not a common microwave application?

is a flat conductor separated from a large conducting ground plane

A microstrip __________.

ducts

Temperature inversions and/or moisture lapses in the atmosphere may extend or reduce the range of a radar by creating __________.

extend the range of a radio communications system

A "repeater" is used to __________.

large surface area

Copper or I²R losses are reduced by what physical property of waveguides?

high loss

Coaxial cable is not widely used for long microwave transmission lines because of its __________.

the main application is frequency multiplication

Which of the following describes the varactor diode?

duplexer

Which of the following radar components allows the use of one antenna for both transmitting the receiving radar energy?

the microwave beam is bent away from Earth

In k-factor conditions, what is sub-standard condition?

skin effect

In a coaxial line, the current-carrying area of the inner conductor is restricted to a small surface layer because of which of the following properties?

13 GHz

If a certain waveguide was designed to have a cut-off frequency of 17 GHz, which of the following signals will not pass thru the waveguide?

it is defined by the radiated power by an antenna in its favored direction, taking into account as referenced to the isotropic radiator

EIRP __________.

is a low pass filter

The following describes a waveguide, except:

cassegrain feed

Using a small reflector to beam waves to the larger parabolic reflector is known as __________.

accumulation of noise is reduced

An advantage of digital techniques over analog in a microwave system is __________.

A and B:

A. decreased beam width

B. increased gain

Increasing the diameter of a parabolic reflector causes which of the following?

consists of standard frequency diversity path where the two transmitter/receiver pairs at one end of the path are separated from each other and connected to antennas that are vertically separated as in space diversity

The hybrid diversity __________.

Ku

13 GHz is under which band?

troposphere

In a line-of-sight communications system, propagation is affected by which of the following layers of the atmosphere?

high gain, narrow beam width

Horn-driven paraboloid antennas have which of the following characteristics?

period of time from the beginning of one transmitter pulse to the beginning of the next

Pulse-repetition time is described as the __________.

tunnel

Which type of diode does not ordinarily operate with reverse bias?

provides the most reliable transmission

The quad diversity __________.

true north

The relative bearing of a radar echo is measured with respect to which of the following reference points?

FSL & FM

In terrestrial microwave communications, the signal is affected by __________.

oscillator

A two-cavity klystron that has a feedback path from the catcher cavity to the buncher cavity will operate as what type of circuit?

cavity resonators

The operating frequency of klystrons and magnetrons is set by the __________.

is used when it is required to separate or combine two or more signals or for simpler interconnections

A waveguide tee __________.

decreases with increasing repetition rate

The maximum effective range for pulsed radar __________.

low-noise and wide-bandwidth

Which of the following TWT characteristics makes it ideal for use as an RF amplifier?

oscillator

A magnetron is used only as an __________.

all of the above:

A. be enclosed by conducting walls;

B. possess resonant properties;

C. contain oscillating electromagnetic fields

For a device to be considered a resonant cavity, it must fulfill which of the following requirements?

more spectrum space

The main benefit of using microwaves is __________.

size and shape

What factors determine the primary frequency of a resonant cavity?

a microwave device which allows RF energy to pass through in one direction with very little loss but absorbs RF power in the other direction

What is an isolator?

a magnetic field

A YIG (Yttrium Iron Garnet) can be tuned by applying __________.

E-type tee junction

A waveguide junction in which the arm area extends from the main waveguide in the same direction as the electric field is an example of what type of junction?

higher-cost equipment

Which of the following is not a disadvantage of microwaves?

used when changes in direction is required

A waveguide bend __________.

magnetron

The device commonly used in microwave ovens is the __________.

high resistance to current flow

Ferrite devices are useful in electronic and microwave applications because they possess magnetic properties and offer which of the following other properties?

a short segment of waveguide that acts as a high Q parallel resonant circuit

What is a cavity resonator?

TWT

The device commonly used in satellite communications is the __________.

heat

The energy in a ferrite attenuator that is attenuated is dissipated as which of the following energy forms?

buncher cavity

In a klystron amplifier, velocity modulation of the electron beam is produced by the __________.

is also known as rat-race tee

In microwave communications, hybrid plane tee __________.

klystron

The device commonly used in UHF transmitters is the __________.

velocity modulation

The alternate speeding up and slowing down of electrons in a beam that produces electron bunches is known as which of the following modulation terms?

uses cavity resonators to produce velocity modulation of the electron beam and produce amplification

The microwave tube, klystron __________.

slots

A microwave phased array is often made using __________.

increases with increasing pulse duration

The minimum effective range for pulsed radar __________.

to decrease the forward velocity of the input

In a TWT, what is the primary purpose of the helix?

15 GHz

A waveguide has a cutoff frequency of 17 GHz. Which of the signals will not be passed by the waveguide?

is greater than in free space

The wavelength of a wave in a waveguide __________.