Waveguides

University of Engineering & Technology Peshawar
Department of Telecommunication Engineering ,Mardan Campus1 |
04-10-2012 First FYP Presentation,Batch-08

Wave Guides
Syed Muhammad Umar Muhammad Fawad khan
Reg.# 11MDTLC0510 Reg.#11MDTLC0483

 The first waveguide was proposed by J. J. Thomson in 1893
and experimentally verified by Oliver Lodge
 In 1894 the mathematical analysis of the propagating modes
within a hollow metal cylinder was first performed by Lord
Rayleigh in 1897. (McLachan, 1947)
History

 Dow-Key, ANRITSU Company are the manufacturer
of Waveguides as well as are the pioneers of making
waveguides and their components in the world.
Companies:

 A hollow conductive metal pipe used to carry high frequency radio
waves, particularly microwave”(A type of a transmission line)[1]
 Form of RF feeder used for microwave applications[2]
 A waveguide is a device that confines electromagnetic energy and
channels it from one point to another[3]
 System of material that is designed to confine electromagnetic waves in
a direction defined by its physical boundaries[4]
What is a Waveguide?

 Only carry or propagate signals above a certain frequency, known
as the cut-off frequency.
Waveguides

Waveguide
TYPES

 Parallel Plate wave guide
 Rectangular waveguide
 Circular waveguide
 Dielectric waveguide
a). Optical waveguide
b). Slab waveguide
Types

 Parallel metallic plates
 Dielectric permittivity
 Width in y-direction
 Height in x-direcion
 Length in z-direction
Parallel plate waveguide

 This is the most commonly used form of waveguide and has a
rectangular cross section.
Rectangular waveguide

 Circular waveguide is less common than rectangular waveguide.
They have many similarities in their basic approach, although
signals often use a different mode of propagation.
Circular waveguide

 This form of waveguide is used on printed circuit boards as a
transmission line for microwave signals. It typically consists of
a line of a given thickness above an earth plane. Its thickness
defines the impedance.
Circuit board stripline

Shapes

• Optical wave guide
• Optical frequencies
• Core dielectric
• Refractive index “n-one” (r<a)
• Cladding dielectric constant
• Refractive index “n-two” (a<r<b)
Dielectric Waveguide

• Slab wave guide.
• Optical frequencies
• Symmetric
• Slab region (n-one)
• Refractive index n-one & n-2
• n-2<n-one
Dielectric wave guide Conti…

• Maxwell’s equations can be solved with suitable boundary
conditions at wall of wave guide. In order to determine
electromagnetic field configuration in wave guide.
• After simplification we achieve field configurations of different
number.
• Each configuration is called mode.
• Wave guide have different types of modes.
Electromagnetic Field configuration

• E (Electric field )
• H(Magnetic feild)
• Ex Hx (x-axis)
• Ey Hy (y-axis)
• Ez Hz (z-axis)
Components Of EM wave
O
X
Y
Z
Ex,
Hx
Ez, Hz
Ey,Hy

 1. Transverse Electro Magnetic (TEM) wave:
Electric and magnetic field components are transverse, or
perpendicular, to the direction of propagation. Here both electric and
magnetic fields are directed components. (i.e.) E z = 0 and Hz = 0.
 2. Transverse Electric (TE) wave:
Here only the electric field is purely transverse to the direction of
propagation and the magnetic field is not purely transverse. (i.e.)
E z = 0, Hz ≠ 0
Possible modes of wave Guide

 3.Transverse Magnetic (TM) wave:
Here only magnetic field is transverse to the direction of propagation
and the electric field is not purely transverse. (i.e.) E z ≠ 0, Hz = 0.
Modes of waveguide Conti…

 . Hybrid (HE) wave:
Here neither electric nor magnetic fields are purely transverse to the
direction of propagation. (i.e.) E z ≠ 0, Hz ≠ 0.
Modes of waveguide Conti…

• TEM mode of operation
• Parallel plate waveguide
• Creation of Electric field at certain voltage
• Electric field vertical to plates
• Current flow in z-direction
• Magnetic field in y-direction
• The interior fields comprise a plane
 Electromagnetic wave which propagate in z-direction.
• Both field are in transverse plane
Basic Operation

 Meaning both the electric and magnetic field components were
transverse, or perpendicular, to the direction of propagation.
TEM Mode Conti…

TE & TM Operation

Dimensions of the waveguide which
determines the operating frequency range:

1. The size of the waveguide determines its operating frequency range.
2. The frequency of operation is determined by the dimension ‘a’.
3. This dimension is usually made equal to one – half the wavelength at the
lowest frequency of operation, this frequency is known as the waveguide
cutoff frequency.
4. At the cutoff frequency and below, the waveguide will not transmit
energy. At frequencies above the cutoff frequency, the waveguide will
propagate energy.
Dimensions of the waveguide which
determines the operating frequency range:

• High frequency
• Medium Frequency
• Low Frequency
• Cut off Frequency
Wave paths in a waveguide at various
frequencies
Angle of incidence(A) Angle of reflection(B)
(A= B)

• When a probe launches energy into the waveguide, the electromagnetic
fields bounce off the side walls of the waveguide as shown in the above
diagram.
• The angles of incidence and reflection depend upon the operating
frequency. At high frequencies, the angles are large and therefore, the
path between the opposite walls is relatively long as shown in fig.
Wave propagation

• At lower frequency, the angles decrease and the path
between the sides shortens.
• When the operating frequency reaches the cutoff frequency
of the waveguide, the signal simply bounces back and forth
directly between the side walls of the waveguide and has no
forward motion.
• At cut off frequency and below, no energy will propagate.
Wave propagation Conti…

• The exact size of the wave guide is selected based on the
desired operating frequency.
• The size of the waveguide is chosen so that its rectangular
width is greater than one – half the wavelength but less than
the one wavelength at the operating frequency.
• This gives a cutoff frequency that is below the operating
frequency, thereby ensuring that the signal will be propagated
down the line.
CUTT OFF Frequency

• The general symbol of representation will be TE m, n or TM m, n
where the subscript m indicates the number of half wave variations
of the electric field intensity along the b ( wide) dimension of the
waveguide.
• The second subscript n indicates the number of half wave
variations of the electric field in the a (narrow) dimension of the
guide.
• The TE 1, 0 mode has the longest operating wavelength and is
designated as the dominant mode. It is the mode for the lowest
frequency that can be propagated in a waveguide.
Representation of modes

Expression for cut off wavelength
22
2













b
n
a
m
c
For a standard rectangular waveguide, the cutoff wavelength is given
by,
Where a and b are measured in centimeters

 A Hollow metallic tube of uniform circular cross section for
transmitting electromagnetic waves by successive reflections from
the inner walls of the tube is called Circular waveguide.
Circular waveguide

• The circular waveguide is used in many special applications in
microwave techniques.
• It has the advantage of greater power – handling capacity and
lower attenuation for a given cutoff wavelength. However, the
disadvantage of somewhat greater size and weight.
• The polarization of the transmitted wave can be altered due to the
minor irregularities of the wall surface of the circular guide,
whereas the rectangular wave guide the polarization is fixed
Circular Waveguide Conti…

• H-type T Junction: The junction acts as a power divider, the signal entering into the
1st port is equally divided among the two ports with the same phase.
• E-Type T Junction: It also acts as a power divider, the signal entering into the 1st port
is equally distributed between the two ports with opposite phase.
Waveguide junction types

Waveguide Tees
Waveguide E-type junction Waveguide H-type junction

 The device magic Tee is a-combination of the E and H plane Tee. Arm 3, the H-arm
forms an H plane Tee and arm 4, the E-arm forms an E plane Tee in combination with
arm 1 and 2 a side or collinear arms. If power is fed into arm 3 (H-arm) the electric field
divides equally between arm 1 and 2 in the same phase, and no electrical field exists in
arm 4. If power is fed in arm 4 (E-arm), it divides equally into arm 1 and 2 but out of
phase with no power to arm 3. Further, if the power is fed from arm 1 and 2, it is added
in arm 3 (H-arm), and it is subtracted in E-arm, i.e. arm 4.
Magic Tee
3
4
1
2

 Magic T waveguide junction
 Magic T waveguide Junction
signal directions
Magic T waveguide junction

• Waveguide E bend
• Waveguide H bend
• Waveguide sharp E bend
• Waveguide sharp H bend
Waveguide bends

• Waveguide E bend
This form of waveguide bend is called an E bend because it distorts
or changes the electric field to enable the waveguide to be bent in
the required direction.
Waveguide E bend
To prevent reflections this waveguide bend must have a radius
greater than two wavelengths
E-bend
Radius greater than 2
wavelengths

• Waveguide H bend
This form of waveguide bend is very similar to the E bend, except that it
distorts the H or magnetic field. It creates the bend around the thinner side
of the waveguide.
wave guide H bend
As with the E bend, this form of waveguide bend must also have a radius
greater than 2 wavelengths to prevent undue reflections and disturbance of
the field.
H-bend
Radius greater
than 2
wavelengths

 In some circumstances a much shorter or sharper bend may be
required. This can be accomplished in a slightly different manner.
The techniques is to use a 45° bend in the waveguide. Effectively
the signal is reflected, and using a 45° surface the reflections
occur in such a way that the fields are left undisturbed, although
the phase is inverted and in some applications this may need
accounting for or correcting.
 Waveguide sharp E bend
Waveguide sharp E bend

 Waveguide sharp H bend
 This form of waveguide bend is the same as the sharp E bend,
except that the waveguide bend affects the H field rather than the
E field.
Sharp H bend

 Waveguide is an indispensable technology for all industries
that make use of transmitting systems.
 Waveguides are used to transfer electromagnetic power
efficiently from one point in space to another.
 High power-handling capacity
 Lower attenuation for a given cut-off wavelength
 The magic-T can be used as a power combiner or divider.
Applications & Uses

 Rotating joints in radars to connect the horn antenna feeding
a parabolic reflector (which must rotate for tracking)
 TE01 mode suitable for long distance waveguide
transmission above 10 GHz.
 Short and medium distance broad band communication
(could replace / share coaxial and microwave links)
Applications of circular waveguide

 [1,2,4]Waveguides CALDERON, DE GUZMAN,QUITEVIS source slide share.
• [3] Prof. David R. Jackson Dept. of ECE Waveguides Part 1: General Theory
References:

Waveguides

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Was ist angesagt?

Was ist angesagt? (20)

Ähnlich wie Waveguides

Ähnlich wie Waveguides (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

Waveguides