GUIDED WAVES
68.
What are guided waves? Give examples
The electromagnetic waves that are guided along
or over conducting or dielectric surface are called guided waves.
Examples: Parallel wire, transmission lines
69. What
is TE wave or H wave?
Transverse electric (TE) wave is a wave in
which the electric field strength E is entirely transverse. It has a magnetic
field strength Hz in the direction of propagation and no component of electric
field Ez in the same direction
70. What
is TH wave or E wave?
Transverse magnetic (TM) wave is a wave in
which the magnetic field strength H is entirely transverse. It has a electric
field strength Ez in the direction of propagation and no component of magnetic
field Hz in the same direction
71. What
is a TEM wave or principal wave?
TEM wave is a special type of TM wave in which
an electric field E along the direction of propagation is also zero. The TEM
waves are waves in which both electric and magnetic fields are transverse
entirely but have no components of Ez and Hz
.it is also referred to as the principal wave.
72. What
is a dominant mode?
The modes that have the lowest cut off
frequency is called the dominant mode.
73.
Give the dominant mode for TE and TM waves
Dominant mode: TE10 and TM10
74.
What is cut off frequency?
The frequency at which the wave motion ceases
is called cut-off frequency of the waveguide.
75. What
is cut-off wavelength?
It is the wavelength below which there is wave
propagation and above which there is no wave propagation.
76.
Write down the expression for cut off frequency
when the wave is propagated in between two parallel plates.
The cut-off frequency, fc = m/ (2a (µE)1/2)
77.
Mention the characteristics of TEM waves.
a)It is a special type of TM wave
b)It doesn’t have either e or H component
c) Its velocity is independent of frequency
d)Its cut-off frequency is zero.
78.
Define attenuation factor
Attenuation factor = (Power lost/ unit
length)/(2 x power transmitted)
79.
Give the relation between the attenuation
factor for TE waves and TM waves aTE = aTM (fc/f)2
80.
Define wave impedance
Wave impedance is defined as the ratio of
electric to magnetic field strength Zxy= Ex/ Hy in the positive direction
Zxy= -Ex/ Hy in the negative direction
81. What
is a parallel plate wave guide?
Parallel plate wave guide consists of two
conducting sheets separated by a dielectric material.
82.Why
are rectangular wave-guides preferred over circular wave-guides?
Rectangular wave-guides preferred over circular
wave guides because of the following reasons.
a) Rectangular wave guide is smaller in size than
a circular wave guide of the same operating frequency
b)It does not maintain its polarization through
the circular wave guide
c) The frequency difference between the lowest frequency
on dominant mode and the next mode of a rectangular wave-guide is bigger than
in a circular wave guide.
83.Mention
the applications of wave guides
The wave guides are employed for transmission
of energy at very high frequencies where the attenuation caused by wave guide
is smaller. Waveguides are used in microwave transmission.Circular waveguides
are used as attenuators and phase shifters
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