Download circular polarization

TOPIC 2: WAVEGUIDE AND COMPONENTS
2.1
MICROWAVE DEVICES (EP603)
Understand the propagation mode of electromagnetic wave.
TIME- VARYING ELECTRIC AND MAGNETIC FIELDS
A changing electric field produces a magnetic field. A changing magnetic field
produces an electric field.
These fields are produced perpendicular to each
other. The magnetic field is a little bit in front of the electric field. Then the
electric field is a little bit in front of the magnetic field. This results in the fields
traveling through space.
At each instant of time,
the distribution of charge would be changing and
reversing direction with a corresponding change in the direction of electric and
magnetic fields due to the driving (alternating) voltage.
The time varying electric field in free space will induce a time-varying magnetic
field in close proximity to the original field and vice versa.
INDUCED ELECTRIC AND MAGNETIC FIELDS
Can expressed mathematically as two vector equations:
Magnetic Filed,
H = ε ( v x E )-------(1)
Electric Field,
E = - μ ( v x H )-------(2)
Where;
H = magnetic field strength, A/m
ε = permittivity, F/m;
E = electric field strength, V/m
μ = permittivity, H/m
The x between the v and E in equation (1), the x between the v and H in
equation (2) indicate that both equations are cross product or
vector product.
Therefore the vectors v, E dan H are always at right angles to each other (Fig.
a ).
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
1
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
y
y
E
90˚
90˚
x
x
90˚
H
H
z
z
Fig. a. Relation of v, E & H
Fig. b.Relation of v, E & H using RHR
y
y
sign reverses
E
(v x H)
x
- (v x H)
-x
x
v
z
. Fig. c. Relation of v, E & H in two dimensions
Fig. d. Vector reversal due to negative sign
From equation (1), the direction of the resulting vector is determined by the RH
vector rule i.e curl the fingers of the right hand from v to E. the thumb points in
the direction of the induced magnetic field.
A vector can also be shown in two dimensions by using the notation of a circle
with either a dot
•
(out) or a cross (in)
x
inside.
Equation (2) has a negative sign in front of the v x H , which indicates that the
direction of the E vector is the reverse of the right-hand rule (Fig. d).
The result of electric and magnetic time-varying waves is a changing electric
field, producing a changing magnetic field and this process continues infinitely.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
2
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Energy is constantly being transferred back and forth between the electric and
magnetic waves. Energy contained in the electric and magnetic field s moves
with the velocity of the speed of light (3 x 108 m/s).
y
E
x v, direction of travels of wave
H
z
Fig. e
Electromagnetic wave travelling in the x direction
PROPAGATION MODES
TYPES OF ELECTROMAGNETIC WAVES
Is determined by the orientation of the electric and magnetic field with respect to
the direction of travel of the wave.
When the electric field, E and the magnetic field, H are oriented transverse to
the direction of propagation of wave, the waves are called transverse
electromagnetic waves (TEM waves) Fig. f.
When the electric field, E is transverse to the direction of propagation of wave
and the magnetic field, H has components transverse and in the direction of the
wave, the electromagnetic wave is called transverse electric waves (TE). Fig g
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
3
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
When the magnetic field, H is transverse to the direction of propagation of wave
and the electric field, E has components transverse and in the direction of the
wave, the electromagnetic wave is called transverse magnetic waves (TM).
Fig h
y
y
y
Ey
Ey
Ey
Direction of
travel
Hx
x
Direction of
travel
Direction of
travel
x
x
Hy
Ex
Hz
Hz
H
z
z
Fig. f TEM waves
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
E
z
Fig. g TE waves
Fig. h TM waves
4
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
POYNTING’S VECTOR
Determines that the power radiation is away from the antenna (the E and H field
are perpendicular to each other) (Fig. e)
Can expressed mathematically as:
H
P = E x H, W/m²
where ;
P = power, W/m²
E
E = electric field, V/m
H = magnetic field, A/m
Poynting’s
V
vector represents the power in watts per square meter of the
electromagnetic wave and the velocity of its wave is equal to the speed of light.
Steps to sketch the direction of electromagetic wave propagation :
1. Determine the direction of propagation.
2. Refer to the electric and magnetic field orientation.
3. Sketch the em wave propagation base on step no. 2.
SPHERICAL WAVE/ WAVEFRONT (MUKA GELOMBANG)

Radiates in all direction uniformly.
Isotropic source
(punca penyerakkan gelombang
e.m radiates
in all direction
PREPARED
BY : ROHANA
BT. IBRAHIM
uniformly)
POLIMAS
DECEMBER 2012 SESSION
Circular curve form
a straight lines.
5
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Is a sphere of constant phase moving away from the antenna with a velocity
equal to the speed of light in a direction determined by Poynting’s vector.
At a given distance from an antenna radiating an electromagnetic wave, the
phase of the electric field at that instant of time would be the same over the
surface of the sphere.
P points outward
H field
E field
•
H
E
Wavefront at a given instant of time
Direction of wavefront
PLANE WAVE (GELOMBANG SATAH)
E
H
Is a small part of the sphere that appears as a flat surface with the electric field,
E and the magnetic field H be at right angles (90˚) to each other and are straight
lines.
POLARIZATION OF A WAVE
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
6
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Refers to the direction of E field.
If a plane wave has the E field in the y or vertical direction, the wave is said to be
vertically polarized (Fig. 1).
If a plane wave has the E field in the x or horizontal l direction, the wave is said to
be horizontally polarized (Fig 2).
y
y
arah per
Hy ambatan
Ey
arah perambatan
z
z
Ex
Hx
x
x
Fig. 1 Vertically Polarized Wave
Fig. 2 Horizontally Polarized Wave
Light in the form of a plane wave in space is said to be linearly polarized. Light is
a transverse electromagnetic wave, but natural light is generally unpolarized, all
planes of propagation being equally probable. If light is composed of two plane
waves of equal amplitude by differing in phase by 90°, then the light is said to be
circularly polarized. If two plane waves of differing amplitude are related in phase
by 90°, or if the relative phase is other than 90° then the light is said to be
elliptically polarized.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
7
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Methods for achieving polarization
Linear Polarization
A plane electromagnetic wave is said to be linearly polarized. The transverse
electric field wave is accompanied by a magnetic field wave as illustrated.
Compare with circular and elliptical polarization
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
8
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
CIRCULAR POLARIZATION
Circularly polarized light consists of two perpendicular electromagnetic plane
waves of equal amplitude and 90° difference in phase. The light illustrated is
right- circularly polarized.
If light is composed of two plane waves of equal amplitude but differing in phase
by 90°, then the light is said to be circularly polarized. The tip of the electric field
vector would appear to be moving in a circle as it approached you. If while
looking at the source, the electric vector of the light coming toward you appears
to be rotating counterclockwise, the light is said to be right-circularly polarized. If
clockwise, then left-circularly polarized light. The electric field vector makes one
complete revolution as the light advances one wavelength toward you. Another
way of saying it is that if the thumb of right hand were pointing in the direction of
propagation of the light, the electric vector would be rotating in the direction of
your fingers.
Circularly polarized light may be produced by passing linearly polarized light
through a quarter-wave plate at an angle of 45° to the optic axis of the plate.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
9
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
ELLIPTICAL POLARIZATION
Elliptically polarized light consists of two perpendicular waves of unequal
amplitude which differ in phase by 90°. The illustration shows right- elliptically
polarized light.
If the thumb of right hand were pointing in the direction of propagation of the light, the
electric vector would be rotating in the direction of your fingers.
In the case of transmission and reception, both the antennas need to have the
same polarization to receive the transmitting signal.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
10
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
BOUNDARY CONDITIONS (SYARAT – SYARAT SEMPADAN)
The two conditions that the E-field and H-field within a waveguide must
meet before energy will travel down the waveguide. The E-field must be
perpendicular to the walls and the H-field must be in closed loops, parallel
to the walls, and perpendicular to the E-field.
The travel of energy down a waveguide is similar, but not identical, to the
travel of electromagnetic waves in free space. The difference is that the
energy in a waveguide is confined to the physical limits of the guide.
Two conditions, known as BOUNDARY CONDITIONS, must be satisfied
for energy to travel through a waveguide. The first boundary condition
(illustrated in fig. 3-27, view A can be stated as follows:
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
11
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
For an electric field to exist at the surface of a conductor, it must be
perpendicular to the conductor. An electric field CANNOT exist parallel
to a perfect conductor.
Figure 3-27.—E field boundary condition.
The second boundary condition, which is illustrated in figure 3-28, can be
stated as follows:
For a varying magnetic field to exist, it must form
closed
loops
in
parallel with the conductors and be perpendicular to the electric field.
Figure 3-28.— H field boundary condition
Since an E field causes a current flow that in turn produces an H field, both
fields always exist at the same time in a waveguide. If a system satisfies
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
12
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
one of these boundary conditions, it must also satisfy the other since neither
field can exist alone.
FREE SPACE BEHAVIOURAL PERLAKUAN RUANG BEBAS
Mengakibatkan berlakunya perubahan pada perambatan sinar gelombang satah.
4 PERLAKUAN RUANG BEBAS IAITU :
refraction – biasan

reflection – pantulan / balikkan

interference – gangguan

diffraction – belauan / serakkan
Introduction to reflection theory:
When a beam of light is incident on a surface,a part of it is returned back into the
same medium.The part of light which is returned back into the same medium is
called the reflected light.Thus,
The return of light into the same medium after striking a surface is called
reflection.
Different surface reflect light to different extents. A highly polished and smooth
surface such as plane mirror, reflects almost the entire light falling on it.
Kinds of Reflection:
There are usually two kinds of reflection:
1)Regular reflection:
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
13
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Regular reflection occurs when a beam of light falls on a smooth surface and
polished surface,such as a plane mirror.A parallel beam of light is incident on a
plane mirror,the reflected beam is also parallel and it is in a fixed direction.This is
called the regular reflection.
2)Irregular reflection:
Irregular reflection occurs when a beam of light falls on a rough surface such as
walls of a room or page of a book etc.The walls of a room or page of a book may
appear smooth ,but if it examined under a microscope,it appears quite uneven
having many small projections. When light rays strike different parts of a rough
surface,the rays are reflected in many different directions and give rise to the
diffused or irregular reflections
Laws of Reflection of Sound:
1.The reflection of the sound follows the law "angle of incidence equals angle of
reflection", sometimes called the law of reflection.
2.The incident , the reflected and the 'normal' wave all lie in the same plane
3.When a longitudinal sounds wave strikes a flat surface, sound is reflected in a
coherent manner provided that the dimension of the reflective surface is large
compared to the wavelength of the sound.
Merupakan perlakuan gelombang cahaya. Oleh kerana gelombang cahaya
merupakan gelombang e.m berfrekuansi tinggi, jadi ciri – ciri boleh dikenakan
pada perambatan gelombang radio.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
14
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
PANTULAN
Pantulan e.m berlaku apabila gelombang tuju yang dipancar mengenai
sempadan 2 media dan menyebabkan sebahagian atau kesemua kuasa tidak
akan diserap ke dalam ke dalam media ke 2 dan ia bergantung kepada bentuk
permukaan dan jenis bahan tersebut. Gelombang yang tidak menembusi media
ke 2 akan dipantul.
Untuk pengalir tulen :Halaju gelombang tuju = halaju gelombang pantulan;
Sudut pantulan, θr
Jika sinar tuju θI
≠
= sudut tuju, θI
sinar pantulan θr ; maka tenaga sinar pantulan akan diserap.
Bagaimanapun keamatan medan voltan pantulan adalah kurang daripada
keamatan medan voltan tuju. Nisbah di antara keamatan voltan pantulan dan
voltan tuju dipanggil sebagai pekali pantulan,Γ (untuk pengalir tulen; Γ -1)
Jika media ke dua 2 bukan pengalir tulen,sebahagian daripada gelombang tuju
akan menembusi masuk dan terserap.Gelombang-gelombang yang terserap ini
akan menghasilkan arus di dalam rintangan bahan dan tenaga akan ditukar
kepada haba.Kuasa yang terserap dalam media ke 2 dipanggil sebagai kuasa
pantulan
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
15
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Untuk pemukaan pantulan yang melengkung (tidak lurus), lengkug gelombang
terpantul adalah berbeza dengan lengkung gelombang tuju.
Untuk permukaan pantulan yang lurus;lengkung mukagelombang terpantul sama
dengan lengkung gelombang tuju.
Pantulan juga berlaku pada permukan yang tidak rata (irregular)
dan kasar
seterusnya akan memusnahkan bentuk mukagelombang yang terhasil.Akibatnya
serakan akan belaku secara rawak dalam banyak arah.
Pantulan specular (mirror-like) merupakan pantulan yang terhasil akibat daripada
permukaan yang licin.
Permukaan separa kasar menyebabkan berlakunya gabungan di antara pantulan
‘specular’ dan ‘diffuse’. Permukaan jenis ini tidak memusnahkan kesemua bentuk
mukagelombang terpantul sebaliknya ia akan mengakibatkan jumlah kuasa
menurun.
PEMBIASAN
Merupakan perubahan arah sinaran apabila ia melalui dua media yang berbeza
ketumpatan, akibatnya halaju perambatan juga berbeza.
halaju perambatan gelombang e.m
1 / ketumpatan media di mana ia
merambat.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
16
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Perubahan dari media kurang tumpat ke media lebih tumpat ; halaju perlahan &
menghampiri garis normal.
Perubahan dari media lebih tumpat ke media kurang tumpat ; halaju bertambah
dan menjauhi garis normal
Banyak pembiasan yang berlaku pada antaramuka bergantung kepada indeks
pembiasan kedua – dua media.
Indeks pembiasan; n boleh ditakrifkan sebagai :nisbah halaju perambatan sinar cahaya; c dalam ruang bebas kepada
halaju perambatan sinar cahaya dalam sesuatu bahan; v. Iaitu;
n=c/v
n juga merupakan rangkap frekuansi ( c = f )
Bagi gelombang e.m yang merambat dalam 2 media yang berlainan indeks
pembiasan , boleh diterangkan dengan menggunakan HUKUM SNELL iaitu :-
di mana ;
= indeks pembiasan bahan 1
= indeks pembiasan bahan 2
= sudut tuju
= sudut pembiasan
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
17
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
GANGGUAN
Gangguan berlaku apabila stesen penerima menerima dua atau lebih isyarat
gelombang e.m yang dihasilkan oleh antena yang sama tetapi bergerak dalam
dua laluan yang berbeza iaitu melalui pantulan pada permukaan bumi, bangunan
tinggi atau kapal terbang.
Tx
Rx
gelombang terus
gelombang pantulan
2 keadaan yang wujud akibat gangguan:
sama fasa – membina

beza fasa – memansuh
Kaedah penghapusan dan penguatan ini bergantung kepada keadaan
permukaan
Rajah di bawah menunjukkan gangguan di antara 2 gelombang e.m di dalam
ruang bebas. Kelihatan pada titik X, kedua-dua gelombang berada pada tempat
yang sama dalam ruang bebas. Bagaimanapun gelombang B memberi laluan
yang berbeza daripada gelombang A, oleh otu sudut fasa relatifnya adalah
berbeza.
Punca
gelombang A
X
gelombang B
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
λ/2
λ/2
λ/2
18
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Jika perbezaan pergerakkan jarak merupakan beberapa bilangan ganjil panjang
gelombang separuh (λ/2), penguatan akan berlaku. Sebaliknya pemansuhan
akan berlaku, jika perbezaan pergerakkan jarak merupakan beberapa bilangan
genap panjang gelombang separuh (λ/2).
DIFFERENT TYPES OF MICROWAVE TRANSMISSION LINE.
WAVEGUIDE DEFINATION
•
Pipe / hollow metal tube or a dielectric transmission line used to guide em
energy from one point to another or through which em waves propagate.
•
the transmission of em energy along waveguide travels at velocity slower
than em energy traveling through free space.
TYPES OF WAVEGUIDES
RECTANGULAR WAVEGUIDE
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
19
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
CIRCULAR WAVEGUIDE
a) Ridged Waveguide
Using Metal Bar
c)
b) Singled Ridged Waveguide
Double Ridged Waveguide
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
20
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
RIDGE WAVEGUIDE
a) Stripline construction
b) E-H field pattern
a) Microstrip construction
b) E-H field pattern
STRIP LINE / MICROSTRIP
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
21
TOPIC 2: WAVEGUIDE AND COMPONENTS
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
MICROWAVE DEVICES (EP603)
22
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
COAXIAL LINE
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
23
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
FLEXIBLE WAVEGUIDE
Describe the structure and the application of microwave transmission line
Terdapat 3 jenis talian penghantaran yang digunakan pada frekuensi gelombag
mikro iaitu :
KABEL SEPAKSI
Menghantar tenaga dengan mod TEM. Tidak sesuai digunakan pada
frekuensi melebihi > Ghz kerana akan berlaku : Kesan kulit (kecenderungan electron untuk bergerak ke permukaan
pengalir) dimana ketumpatan arus akan diagihkan dengan banyak
pada permukaan pengalir luar dan menyebabkan kehilangan kuasa
(kehilangan pengalir) berlaku.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
24
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
 Kehilangan pancaran dimana arus berfrekuensi tinggi yang mengalir
didalam konduktor akan menyebabkan rintangan menjadi amat tinggi,
seterusnya kondukto tersebut akan bertindak sebagai antenna dan
menyebabkan isyarat dipancarkan.
 Kehilangan dielektrik – kesan pemanasan adalah berkadar terus
dengan frekuensi. Jadi pada frekuensi gelombang, kehilangan tenaga
sangat ketara bagi talian penghantaran yang menggunakan dielektrik
pepejal. Sebab itu talian dawai buka dan kabel sepaksi tidak sesuai
pada frekuensi melebihi > Ghz.
Masalah-masalah ini boleh diatasi dengan menggunakan pandugelombang.

PANDUGELOMBANG
 Ia merupakan satu paip ayau bahan logam yang berongga yang
digunakan untuk memandu gelombang e.m dari satu tempat ke
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
25
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
satu atau lebih tempat dengan pelemahan, serta kehilangan
pancaran dan kehilangan haba yang rendah.
 Digunakan untuk menghantar tenaga dalam mod TM atau mod TE
untuk jarak yang jauh dan media yang digunakan untuk merambat
isyarat di dalamnya adalah udara.
 Medan E dan medan H yang wujud di dalam pandugelombang
mestilah memenuhi syarat-syarat sempadan (medan E – serenjang
dan medan H – selari).Ini dapat dilakukan dengan menggunakan
kaedah zig-zag (pantulan)
 pembalikkan yang berlaku pada dinding menjadikan medan E
maksima ditengah-tengah pandugelombang dan sifar pada sisi
dinding. Dalam keadaan ini tiada litar pintas berlaku dan
perambatan tidak terganggu.
 Jadi boleh dikatakan bahawa fungsi dinding hanyalah untuk
menghasilkan pembalikkan dan pengaliran tenaga adalah melalui
dielektrik (udara) yang terdapat didalamnya.
 Pandugelombang boleh didapati dalam bentuk segiempat, bulat,
terbatas dan lain-lain. Dimensi pandugelombang yang digunakan
mestilah dalam susunan (order) yang sama dengan panjang
gelombang
isyarat
yang
digunakan
(frekuensi
,
dimana
pandugelombang )
KELEBIHAN :-
Pemancaran beberapa isyarat dilakukan secara serentak
dengan menggunakan mod perambatan yang berbeza
walaupun isyarat-isyarat ini berfrekuensi sama.
-
(Dalam talian biasa, sesuatu isyarat dipisahkan di antara
satu sama lain dengan menggunakan frekuensi-frekuensi
yang berlainan, Contoh :FDM)
KELEMAHAN :PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
26
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
-
Kehilangan adalah minima.
-
Mengunakan emas kerana kurang penggali.
-
Dihantar dengan frekuensi tinggi.
-
Diperbuat daripada logam.
-
Menggunakan
cover/mar
untuk
mengurangkan
pengembangan terma.
KELEBIHAN PANDUGELOMBANG KEATAS KABEL SEPAKSI.
 Senang dibuat (bina) kerana terdapat pengalir dalam.
 Keupayaan untuk mengendali kuasa adalah lebih kerana kehilangan
pancaran jarang berlaku disebabkan oleh ketiadaan pengalir dalam atau
dielektrik (10x > daripada kabel sepaksi yang sama dimensinya)
 Kehilangan kuasa ( I² R) kurang kerana perambatan adalah secara pantulan
dari dinding berbanding dengan kabel sepaksi (merujuk kepada kesan kulit)
 Kapasiti membawa maklumat adalah lebih berbanding kabel sepaksi ( 10
kabel sepaksi; 1 pandugelombang ) – kehilangan kurang
 Dapat membawa tenaga berfrekuensi tinggi berbanding kabel sepaksi (kabel
sepaksi < 1 Ghz; pandugelombang – 325 Ghz)

PAPAN LITAR TERCETAK GELOMBANG MIKRO ( MPCB – MIKROWAVE
PRINTED CIRCUIT BOARD )
 JALUR MIKRO (MIKRO STRIP)
- Boleh disamakan seperti talian dawai buka.
- Ia merupakan 2 keping pengalir yang dipisahkan oleh dielektrik pada
bahagian tengahnya.
- Sesuai digunakan untuk penghantaran isyarat bagi jarak dekat
kerana pengalir luarnya yang terdedah menyebabkan berlakunya
pancaran dan hangar.
- Kelebihan :- senang untuk dibina dan kosnya murah
Pengalir isyarat
Dielektrik
t
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
b
27
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Dielektrik
Ground plane
 TALIAN JALUR (STRIP LINE)
- Boleh disamakan seperti kabel sepaksi.
Pengalir luar
Medan E
Dielektrik
Ground plane
w
Pengalir dalam
Medan H
 RECTANGULAR WAVEGUIDES
 The wall of the guides are conductors and therefore reflection from them may take place. The
electromagnetic waves travel within the guide must complied to the boundary conditions ( i.e electric
field E must exist within the guide and, at the same time, be zero at the surface of the side walls; the
magnetic field H must also exist within the guide but cannot be perpendicular to any of the walls).
 Electric field E perpendicular to conducting surface – only electric field E exist (i.e max at the centre of
the long dimension, and decreases to zero at the sides).
 Magnetic field H exist tangentially (parallel) to all conducting surfaces (continuouslly around and back
into the the waveguide, forming a complete loop).
E
E field
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
28
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
H
H field
waveguide)
P (wave direction out of
 To fullfill the boundary conditions, the em wave is sent in a zig-zag manner bouncing it off the wall
and setting up a standing wave pattern with its max at the centre and zero at the wall. The em wave
cannot travel in straight line coz the E field will be short circuited by the walls.
 THE CONSEQUENCES OF ZIG-ZAG CONFIGURATION
i)
The velocity of propagation Vg will be less than in free space Vc (Vg - parallel to the wall surface).
ii) The wavelength signal propagated inside the guide ( λp) > λc (free space wavelength). λp refers to the
distance between 2 successive crests in the direction of measurement ( max  max, min  min). It is
also parallel to the wall surface).
iii) There are 2 basic methods of propagation depending on how the wave is set up (i.e TE or TM mode)
and they are no longer in TEM mode.
PLANE WAVES AT CONDUCTING SURFACE
Let the actual propagation velocity = Vc
&
incident angle
= θ
Propagation velocity normal to the wall, Vn = Vc cos
θ
Velocity parallel to the wall ,
θ
Vg = Vc sin
(Group velocity @ propagation inside the
waveguide)
 WAVELENGTH CONCEPT, λ
Wavelength – distance between 2 successive crests in the direction of measurement .
λn = λ / cos θ ,
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
λp = λ / sin θ
29
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
 PHASE VELOCITY CONCEPT, V
p
In free space or in the direction of propagation the velocity of em wave is given by,
Vc = f λ = 3 x 108 m/s
where;
λ = wavelength measured in the direction of propagation
f = frequency of the wavelength
For situation (phase wave at the conducting surface) the velocity with which the surface changes it phase in
the direction parallel to the wall is given by :
Phase Velocity,
Vp
= f λp
= f λ / sin θ
= Vc / sin θ
= 3 x 108 m/s
sin θ
Phase velocity is not the propagation velocity of the wave along the boundary (parallel to the wall). It is only
the velocity at which it changes phase in that direction.
s/cct
I
V
Zin2
Zin1
L1
ZL
Zs/cct
L2
4λ/4 3λ/4 2λ/4 1λ/4 0λ
At L1 and L2, the input impedande is not the same. It varies according to the length. Thus has different
standing wave pattern. If the termination is short circuited (V = 0) at λ/2 ; V  0 V & I  max.
Meaning that the distance of the first wall must be at 1 λ away from the short circuit termination so as to
obtain Vmax at the centre. The position of the wall must be at point where the electric intensity = 0 so as not
to upset the standing wave pattern.
 ADDITION OF SECOND WALL
A
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
30
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
B
C
1
2
3
4
5
6
7
8
The present of the reflecting wall is due to em wave i.e. what a short circuit did to wave on transmission line,
a pattern is set up and will be destroyed unless the second wall is place at a correct position. The situation
is illustrated in the figure above. The second wall is added at which the electric intensity due to first wall is
zero.
a = m λn
2
 
Also;
λn = λ / cos θ ,
λp = λ / sin θ
Therefore;
a =
cos θ =
Where by;
a = distance between wall
mλ
2 cos θ
mλ
2a
 
λn = wavelength in direction normal to both wall
m = no. of. λ / 2 (represents E field bunch exist between wall ‘b’)
λ = free space wavelength
From equation , angle of incident is determined by the free space wavelength of the signal ‘λ’, the
integers ‘m’ and the distance between the wall ‘a’.
Wavelength of travelling wave which propagate down the waveguide,
But,
λp = λ / sin θ
sin θ = √ (1- cos2 θ )
= √ 1- ( m λ / 2a )2
Therefore;
λp =
λ
√ 1- ( m λ / 2a )2
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION

31
TOPIC 2: WAVEGUIDE AND COMPONENTS
When,
MICROWAVE DEVICES (EP603)
λp = 0  no propagation occurs; λ ≠ 0, values of ‘m’ & ‘a’ is fixed
Denominator (Pembawah)  infinity i.e ( λp = λ / infinity = 0 ),
Means that signal is blocked / cannot travel.
If,
√ 1- ( m λ / 2a )2 = 0
1- ( m λ / 2a )2 = 0
Therefore,
If,
Cut off wavelength,
λ 0 = 2a / m

λ = 2a / m, signal will not be received at the receiver.
For any wavelength λ ≥ λ 0 @ ( f 0 ≤ f )  no propagation occurs
λ < λ 0 @ ( f 0 > f )  propagation occurs
From equation ; as free space wavelength is increased, there comes a point which the waves can no
longer propagate in a waveguide with a fixed ‘a’ and ‘m’. The free space wavelength at which this takes
place is called the cut off wavelength (λ 0).
 CUT OFF / CRITICAL WAVELENGTH
Is defined as the largest wavelength that can propagates in the waveguide without any / minimum
attenuation (or the smallest free space wavelength that is just unable to propagate in the
waveguide). Its depend on the size of the waveguide and the mode of propagation.
Put eqn.  into eqn.;
λp =
Example:
λ
√ 1- ( λ / λ 0 )2
1. A wave is propagate in a parallel plane waveguide. The frequency and the distance between the 2 walls
is 6 GHz and 3 cm respectively. Calculate (i) cut off wavelength for dominant mode (m=1) (ii)
wavelength in a guide (iii) the corresponding group and phase velocity (iv) cut off frequency.
SOLUTIONS :
a = 0.03 m , m = 1, f = 6 GHz
i) λ 0 = 2a / m
= 2 x 0.03 /1
= 0.06 m.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
iii) Vg = Vc sin θ
= Vc √ 1- ( λ / λ 0 )2
32
TOPIC 2: WAVEGUIDE AND COMPONENTS
ii) λp =
MICROWAVE DEVICES (EP603)
λ
√ 1- ( λ / λ 0 )2
λ = Vc / f = 3 x
108
= 3 x 108 √ 1- ( 0.05 / 0.06 )2
/6x
= 165.83 x 10 6 m/s.
109
iv) Vp = Vc / sin θ
= 0.05 m.
= Vc / √ 1- ( λ / λ 0 )2
= 3 x 108 / √ 1- ( 0.05 / 0.06 )2
(λ 0 > λ – propagation occurs)
= 592.7 x 10 6 m/s.
λp
=
0.05
√ 1- ( 0.05 / 0.06 )2
v) f0 = Vc / λ 0
= 0.09 m.
= 3 x 108 / 0.06
= 5 GHz.
2. It is necessary to propagate a 10 GHz signal in a waveguide whose wall separation ‘a’ is 6 cm. What is
the greatest no. of half wavelength electric intensity which it will be possible to establish between the 2
walls. (i.e what is the largest value of m). Calculate (a) guide wavelength for thismode of propagation
(b) State its propagation mode.
EXCERCISE : Determine (i) cut off wavelength (ii) wavelength in the guide (iii) group velocity
( iv) phase velocity
(v) cut off frequency for all the propagation mode.
SOLUTIONS :
a = 0.06 m , f = 10 GHz
λ 0 = 2a / m
m = 4;
λ < λ 0 – propagation occurs
λ = Vc / f
= 3 x 108 x 10 x 109 = 0.03 m.
When :
m = 1; λ 01 = 2a / m = 2 x 0.06 / 1 = 0.12 m
(λ < λ 0 propagation occurs)
m = 2;
λp
=
λ 04 = 2a / m = 2 x 0.06 / 4 = 0.03 m
(λ ≥ λ 0 no propagation occurs)
λ
√ 1- ( λ / λ 0 )2
When :
m = 1;
λ p1 =
0.03098 m
0.03
=
√ 1- ( 0.03 / 0.12 )2
λ 02 = 2a / m = 2 x 0.06 / 2 = 0.06 m
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
33
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
(λ < λ 0 propagation occurs)
m = 3;
λ 03 = 2a / m = 2 x 0.06 / 3 = 0.04 m
(λ < λ 0 propagation occurs)
m = 2;
m
λ p2 =
m = 3;
m
λ p3 =
0.03
= 0.0346
√ 1- ( 0.03 / 0.06 )2
0.03
= 0.0454
√ 1- ( 0.03 / 0.04 )2
3. A rectangular waveguide 4 x 2 cm internally with m = 2 has a 10 GHz signal propagated in it.
Calculate : (i) λp
(ii) λo
(iii) Vg
(iv) Vp
(v) f0
SOLUTIONS :
a = 0.04 m , m = 2, f = 10 GHz
λ 0 = 2a / m
= 2 x 0.04 /2
= 0.04 m.
i) λp =
m
λ = Vc / f = 3 x 108 / 10 x 109
ii) Vg = Vc sin θ = 3 x 108 x 0.061 = 1.983 x 108
= 0.03 m.
λ
= 0.03
√ 1- ( λ / λ 0 )2
= 0.0454
0.061
m/s.
(λ 0 > λ – propagation occurs)
sin θ = √ 1- ( λ / λ 0 )2 = √ 1- ( 0.03 / 0.04 )2 =
0.661
iii) Vp = Vc / sin θ = 3 x 108 / 0.061 = 4.54 x 108
m/s.
iv) f0 = Vc / λ 0 = 3 x 108 / 0.04 = 3.75 GHz.
TE/TM are the configuration of E and H fields. The two mode consists of subscript ‘m’ and ‘n’
which will determine the field patterns and it refers to whole / integer number.
 TM mn / TE mn (TRANSVERSE MAGNETIC / TRANSVERSE ELECTRIC)
m
n
 Integer number.
 Denotes the number of half wavelength of
intensity or @ semi sinusoidal wave pattern
(λ / 2) at E or H field intensity.
 Refers to the width or dimension ‘a’ of the
rectangular waveguide.
 Integer number.
 Denotes the number of half wavelength of
intensity or @ semi sinusoidal wave pattern
(λ / 2) at E and H field intensity.
 Refers to the narrow dimension ‘b’ of the
rectangular waveguide.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
34
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
 The propagation mode of TE and TM in the rectangular waveguide depends on critical / cutoff
method used.
 The characteristics used to identify the critical / cutoff method are f c (f0) and λc ( λ 0).
 Different TE and Tm modes all have different cutoff wavelength and therefore encounter
different characteristic wave impedance. Eg. TM11, TM12 etc.
 The dimension of the waveguide and the propagation modes used is affected by the cutoff
wavelength / frequency (f0 and λ 0).
 Only certain frequency / wavelength are being allowed to propagate in the waveguide.
WHY WAVEGUIDE BEHAVES LIKE HIGH PASS FILTER ?
KENAPA PANDUGELOMBANG BERKELAKUAN SEPERTI PENAPIS LALUAN
TINGGI?
Coz it passes all frequencies that is higher than the
cutoff frequency (lowest
frequency) to pass through with least / without attenuation. The value
of the
critical frequncy depends on the types of propagation mode.
(Kerana ia memberi laluan kepada semua frekuansi-frekuansi yang nilainya lebih
tinggi daripada nilai frekuansi potong (frekuansi terendah) tanpa pelemahan yang
tinggi. Nilai frekuansi potong bergantung kepada jenis mod perambatan.)
 When n ≠ 0, the λ
λ0=
0
for TE mn mode is given by ;
2
√ (m/a)2 + ( n / b )2
 CRITICAL / CUTOFF FREQUENCY ( f )
0
Refers to the frequency below which wave propagation will not occur.
Is defined as the lowest frequency that can be propagated along the guide with minimum attenuation
under given condition (i.e depends on the propagation mode and guide size).
 CRITICAL / CUTOFF WAVELENGTH, ( λ
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
0)
35
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Is defined as the longest wavelength that can be propagated along the guide with minimum attenuation
under given condition (i.e depends on the propagation mode and guide size).
 Propagation occurs / takes place along the guide when fc > f0 and λ < λ 0.
 THE PROPAGATION MODES AND THE FIELD PATTERN OF RECTANGULAR WAVEGUIDE
 TE mo – TE 10, TE20, TE30, .....
 TE 10 – refers to dominant or principal mode ( m=1, n=0)
 Has lowest cutoff frequency (f0), longest wavelength (λ 0), simplest & least complicated field pattern
and lowest attenuation compared to others propagation mode.
TOP VIEW

E field direction
x
E field changes its polarity
 Polarization intensity is the same as the original
polarity.
 Group ------- are group that travels along the guides
at group velocity.
 When E field changes its polarization, H fields also
change its field simultaneously.
 E field intensity for TE10 mode is max at the centre
and drops sinusoidally to zero intensity at the sides
of the wall.
Front / cross-sectional view
 1,0 means only one half wavelength exists across
the waveguide width.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
36
TOPIC 2: WAVEGUIDE AND COMPONENTS
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
MICROWAVE DEVICES (EP603)
37
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
38
TOPIC 2: WAVEGUIDE AND COMPONENTS
 TE
mn
MICROWAVE DEVICES (EP603)
MODES
 Refers to the existance of one half wavelength (λ / 2) across the guide width (m) and narrow
dimension (n).
 Needs modification of wave. They are used in practice as often as the TEmo mode (except TE11 mode
which does have some practical application.
 Eg. TE 11 (1,1 – has one λ / 2 at guide width and narrow dimension ).
 All the equations so far derived applies here except for the equation of the cutoff wavelength λo which
must naturally be difference, since other walls are also used.
λ/2
λ/2
 TE
m0
( H m0 ) MODES
 All equations so far derived for parallel plane waveguide applied to the rectangular waveguide carrying
TE m0
( H m0 ) modes.
 Added to, is the characteristic wave impedance of the waveguide (Z 0TE ) given as :
Z 0TE =
Z
√ 1- ( λ / λ 0 )2
=
377
Ω

√ 1- ( λ / λ 0 )2
Where ; Z = 120 π = 377 Ω i.e characteristic impedance of free space.
(Z 0TE depends on λ 0 ; λ 0 depends on `a’ & `m’ . Hence, Z 0TE also depends on `a’ dan `m’.)
 Different TEm0 modes will have different λ0 & thus encountered different characteristics wave
impedance ( Z0TE).
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
39
TOPIC 2: WAVEGUIDE AND COMPONENTS
 TE
mn
MICROWAVE DEVICES (EP603)
( H mn ) MODES
 Are not used in practice as often as the TE
m0
modes (except TE
11
mode which does have some
practical applications – as a feeder). Besides that TE 11 mode has one λ / 2 at guide width and narrow
dimension. It involves all the wall of the guide).

All the equations so far derived applies here accept for the equation of the cutoff wavelength λ 0 which
must be naturally different, since the other walls are also used.

General equation for the cutoff wavelength is given by :-
λ0
=
2

f0
=
V

√ (m / a)2 + ( n / b)2
( √ µ’ Є ) λ 0
=
Where, µ’ = Є = 1 in free space
 TE
m0
λ0
V √ ( m / a )2 + ( n / b )2
2
( H m0 ) MODES
=
2
√ (m / a)2
=
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
2a
m
40
TOPIC 2: WAVEGUIDE AND COMPONENTS
 TM
mn
MICROWAVE DEVICES (EP603)
MODES
 H field across the propagation direction
 Loop cannot be seen on top view.
 Loop can be seen at front view.
 1 loop = separa gelombang, λ / 2.
TM 11 –half wavelength (λ / 2) exist at guide width & half of E field intensity exist at narrow dimension.
Side view – E field ends at 90°.
TM modes are govern by relations identical to those governing TEmn modes except that the equation for
characteristic wave imedance Z0.
 TM
mn
( E mn ) MODES
 TMmn modes are govern by relations identical to those governing TEmn modes except that the equation
for the characteristics wave impedance Z 0TM given by :-
Z 0TM = Z √ 1- ( λ / λ 0 )2 = 377 √ 1- ( λ / λ 0 )2 Ω

( Z 0TM < 377 Ω )
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
41
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
The equation above yield impedance values which are always < 377 Ω & this is the main reason why TM
modes are sometimes used especially TM11 – it is sometimes advantage to feed a waveguide directly from
coaxial transmission line in which case the waveguide input impedance must be a good deal lower than 377
Ω.
Example :
4. A rectangular waveguide 1.78 x 0.993 cm externally with wall thickness, t - 0.102 cm, TE
10
mode.
Calculate :- (i) cutoff frequency (ii) cutoff wavelength (iii) cutoff frequency for TE21. TE21 mode.
SOLUTIONS :
In free space , µ’ = Є = 1; TE10 - m=1, n=0
Waveguide width,
λ0
=
a = external width – 2 t
= 1.78 – 2 (0.102)
= 1.58 cm
= 0.0158 m.
2a =
m
2 x 0.0158 = 0.0316 m.
1
For TE21 Mode;
f0
= Vc √ ( m / a )2 + ( n / b )2
2
= 3 x 108 √ ( 2 / 0.0158 )2 + ( 1/ 0.789)2
2
= 26.9 GHz.
λ0
=
Narrow dimension, ‘b’ = ext narrow dimension – 2t
= 0.993 - 2 (0.102)
= 0.789 cm
= 0.00789 m.
f0 = Vc √ ( m / a )2 + ( n / b )2
2
= Vc √ ( m / a )2
2
= 3 x 108 √ ( 1/ 0.0158 )2
2
= 9.49 GHz.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
Vc / f0
= 3 x 108 / 26.9 x 109
= 0.0111m.
= 1.11 cm.
42
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
5. Base on Q 4, calculate characteristic wave impedance for TE10 mode for the propagation frequency of
18 GHz.
SOLUTIONS :
Wavelength for 18 GHz;
λ
=
Vc / f
Z0TE
=
= 3 x 108 / 18 x 109
= 0.0167m.
377
Ω
√ 1- ( λ / λ 0 )2
=
= 1.67 cm.
377
√ 1- ( 0.0167 / λ0.0316 )2
= 444 Ω.
Excercise : Aslo calculate (i) Vg (ii) Vp
 PRACTICAL ASPECTS OF RECTANGULAR WAVEGUIDE
 Useful in the frequency range from 3 GHz - > 100 GHz where the width of the guide ranges in size
from mm to about 10 cm in dimensions.
 More efficeint than coaxial lines since there are no centre conductor losses ( I2R ) & skin effect.
 Power handling capacity of of a guide is dependent on the physical size of the guide. The larger the
guide, the > the P handling capacity).
 The principal / dominant mode will use the samllest guide for a given frequency to prevent the formation
fo higher modes.
 Higher modes used larger guides, thus allow greater P for the same frequency than is possible with the
principal / dominant mode is a smaller guide.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
43
TOPIC 2: WAVEGUIDE AND COMPONENTS
 CIRCULAR
MICROWAVE DEVICES (EP603)
WAVEGUIDE / SUBmm
 Applies for TE mn and TM mn modes.
 `m’ indicates the number of full wavelengths ( λ) around the circumference of the inner dimension of
the guide.
 `n’ indicates the number of one half wavelength ( λ/2) across the inner diameter of the guide.
CIRCULAR WAVEGUIDE MODES
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
44
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Counting wavelengths in a
circular waveguide.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
45
TOPIC 2: WAVEGUIDE AND COMPONENTS
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
MICROWAVE DEVICES (EP603)
46
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
EXAMPLES : TYPICAL E & H FIELDS PATTERNS FOR TE mn and TM mn MODES
 CUTOFF WAVELENGTH (Λ0) FOR CIRCULAR WAVEGUIDES
The lowest frequency (longest wavelength) that can be transmitted through the guide is TE
11
mode
(dominant /principal mode, refer to the lowest Bessel function’s value). Cutoff wavelength depends on
the transmission mode and the roots of Bessel equation.
 CUTOFF WAVELENGTH (Λ0) MODE FOR:
TE mn
where ;
Λ0 =
2 π
µ’ mn
TM mn
Λ0 =
2 π
µ mn
λ0
= longest wavelength possible in the guide for the given mode; cm
r
= inside radius of circular guide.
µ ` mn = roots of Bessel equation (Table 1a).
µ
mn
= roots of Bessel equation (Table 1b).
BESSEL ROOTS
TE mn MODE
(Table 1a)
TM mn MODE
( Table 1b)
µ ’ 01
3.821
µ 01
2.405
µ ’ 11
1.841
µ 11
3.832
µ ’ 21
3.054
µ 22
5.136
µ ’ 31
4.201
µ 02
5.520
µ ’ 02
7.016
µ 12
7.016
µ ’ 12
5.332
µ 03
8.654
µ ’ 22
6.706
µ ’ 32
8.031
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
47
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
EXAMPLE :
6. (i) Calculate the internal diameter required for TE11 mode with cutoff fequency of 12 GHz for a circular
guide .
(ii) Also calculate the internal diameter, if Λ 0 = 2.5 cm TM 11 mode.
SOLUTIONS :
Wavelength at 12 GHz;
Λ0
m = diameter , 2 r
= Vc / f 0
= 3x
108
/ 12 x
= 2 x 7.33 x 10-3
109
= 0.0147 m.
= 0.025 m.
Λ0 =
2πr
µ ’ mn
r = Λ 0 µ ’ mn
2π
= 0.025 x 1.841
2 x 3.14
= 7.33 mm .
TM 11 MOD MODE
(ii)
r = Λ 0 µ mn = 0.025 x 3.832
2π
2 x 3.14
= 0.0153 m.
Diameter,
2r = 2 x 0.0153
= 0.0306 m.
EXCERCISE
1. Given : circular guide, mode - TE11; propagation frequency – 10 GHz, internal diameter – 4 cm.
Calculate :(i) Λ 0 (ii) Λ p (iii) Z 0TE
(iv) Vg
(vi) Vp
2. Given a circular guide with internal diameter; 5 cm. Calculate f0 for modes : TE 11, TM 01 and TE01. Λ
and
characterics wave impedance for the modes stated.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
p
48
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
 THE DIFFERENCES BETWEEN THE RECTANGULAR & CIRCULAR WAVEGUIDES
 Refers to Bessel Roots 1(a) dan 1(b), the mode with the longest cutoff wavelength which has the
smallest value of µ ’ mn is TE11 mode ( µ ’ 11 = 1.841).
 Integer `m’ indicates the number of full wave intensity ( Λ ) variation around the circumference.

Integer `n’ indicates the number of one-half wavelength intensity ( Λ / 2 ) changes radially out from the
centre of the wall (across the diameter of the guide).
 DISADVANTAGES
 Its cross section needs bigger area to carry the same signal as in rectangulat guide.
 ADVANTAGES
 Easier to manufacture and easier to joint together.
 Rotation of polarization may be overcome by the use of TE01 and TM 01, both of which are rotationally
symmetrical.
 Capable of handling more power.
 Less attenuation at cutoff frequency.
 Use from to overcome reflection.
 BASIC APPLICATION
 For rotational joint as used in conjuction with rotable radar antennas, under such condition use of
rectangular waveguide is not nearly practicable. The main waveguide run in a radar system is likely to
be rectangular with a circular piece at end which is connected to the antenna by a rotating joint, TM 01
mode is most likely to be used for this application since it is rotationally symmetrical. Besides requires
smaller diameter than TE01 mode.
 TM 01 mode is used due to its rotationally symmetrical thus will not affect its field patterns. Besides it
requires smaller diameter than TE01 mode ( impossible in rectangular waveguide).
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
49
TOPIC 2: WAVEGUIDE AND COMPONENTS
2.5
MICROWAVE DEVICES (EP603)
Understand the discontinuities in waveguide components.
2.5.1 Identify waveguide components:
a. Connectors/Joint
b. Attenuators
c. Coupler
d. Basic accessories (bends, corner, tapered, twist)
e. Junction-T and Hybrid-T
Waveguide junctions are used when power in a waveguide needs to be split or some
extracted. There are a number of different types of waveguide junction that can be use,
each type having different properties - the different types of waveguide junction affect
the energy contained within the waveguide in different ways.
When selecting a waveguide junction balances between performance and cost need to be
made and therefore an understanding of the different types of waveguide junction is
usedful.
Waveguide junction types
There are a number of different types of waveguide junction. The major types are listed
below:




H-type T Junction: This type of waveguide junction gains its name because top
of the "T" in the T junction is parallel to the plane of the magnetic field, H lines in
the waveguide.
E-Type T Junction: This form of waveguide junction gains its name as an Etype T junction because the tope of the "T" extends from the main waveguide in
the same plane as the electric field in the waveguide.
Magic T waveguide junction: The magic T waveguide junction is effectively a
combination of the E-type and H-type waveguide junctions.
Hybrid Ring Waveguide Junction: This form of waveguide junction is another
form of waveguide junction that is more complicated than either the basic E-type
or H-type waveguide junction.
E-type waveguide junction
It is called an E-type T junction because the junction arm, i.e. the top of the "T" extends
from the main waveguide in the same direction as the E field. It is characterized by the
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
50
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
fact that the outputs of this form of waveguide junction are 180° out of phase with each
other.
Waveguide E-type junction
The basic construction of the waveguide junction shows the three port waveguide device.
Although it may be assumed that the input is the single port and the two outputs are those
on the top section of the "T", actually any port can be used as the input, the other two
being outputs.
To see how the waveguide junction operates, and how the 180° phase shift occurs, it is
necessary to look at the electric field. The magnetic field is omitted from the diagram for
simplicity.
Waveguide E-type junction E fields
It can be seen from the electric field that when it approaches the T junction itself, the
electric field lines become distorted and bend. They split so that the "positive" end of the
line remains with the top side of the right hand section in the diagram, but the "negative"
end of the field lines remain with the top side of the left hand section. In this way the
signals appearing at either section of the "T" are out of phase.
These phase relationships are preserved if signals enter from either of the other ports.
H-type waveguide junction
This type of waveguide junction is called an H-type T junction because the long axis of
the main top of the "T" arm is parallel to the plane of the magnetic lines of force in the
waveguide. It is characterized by the fact that the two outputs from the top of the "T"
section in the waveguide are in phase with each other.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
51
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Waveguide H-type junction
To see how the waveguide junction operates, the diagram below shows the electric field
lines. Like the previous diagram, only the electric field lines are shown. The electric field
lines are shown using the traditional notation - a cross indicates a line coming out of the
screen, whereas a dot indicates an electric field line going into the screen.
Waveguide H-type junction electric fields
It can be seen from the diagram that the signals at all ports are in phase. Although it is
easiest to consider signals entering from the lower section of the "T", any port can
actually be used - the phase relationships are preserved whatever entry port is ised.
Magic T hybrid waveguide junction
The magic-T is a combination of the H-type and E-type T junctions. The most common
application of this type of junction is as the mixer section for microwave radar receivers.
Magic T waveguide junction
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
52
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
The diagram above depicts a simplified version of the Magic T waveguide junction with
its four ports.
To look at the operation of the Magic T waveguide junction, take the example of whan a
signal is applied into the "E plane" arm. It will divide into two out of phase components
as it passes into the leg consisting of the "a" and "b" arms. However no signal will enter
the "E plane" arm as a result of the fact that a zero potential exists there - this occurs
because of the conditions needed to create the signals in the "a" and "b" arms. In this
way, when a signal is applied to the H plane arm, no signal appears at the "E plane" arm
and the two signals appearing at the "a" and "b" arms are 180° out of phase with each
other.
Magic T waveguide junction signal directions
When a signal enters the "a" or "b" arm of the magic t waveguide junction, then a signal
appears at the E and H plane ports but not at the other "b" or "a" arm as shown.
One of the disadvantages of the Magic-T waveguide junction are that reflections arise
from the impedance mismatches that naturally occur within it. These reflections not only
give rise to power loss, but at the voltage peak points they can give rise to arcing when
sued with high power transmitters. The reflections can be reduced by using matching
techniques. Normally posts or screws are used within the E-plane and H-plane ports.
While these solutions improve the impedance matches and hence the reflections, they still
reduce the power handling capacity.
Hybrid ring waveguide junction
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
53
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
This form of waveguide junction overcomes the power limitation of the magic-T
waveguide junction.
A hybrid ring waveguide junction is a further development of the magic T. It is
constructed from a circular ring of rectangular waveguide - a bit like an annulus. The
ports are then joined to the annulus at the required points. Again, if signal enters one port,
it does not appear at allt he others.
The hybrid ring is used primarily in high-power radar and communications systems
where it acts as a duplexer - allowing the same antenna to be used for transmit and
receive functions.
During the transmit period, the hybrid ring waveguide junction couples microwave
energy from the transmitter to the antenna while blocking energy from the receiver input.
Then as the receive cycle starts, the hybrid ring waveguide junction couples energy from
the antenna to the receiver. During this period it prevents energy from reaching the
transmitter.
Summary
Waveguide junctions are an essential element within waveguide technology. Enabling
signals to be combined and split, they find applications in many areas as discussed in the
text. The waveguide T junctions are the simplest, and possibly the most widely used,
although the magic-T and hybrid ring versions of the waveguide junction are used in
particular applications where their attributes are required.
Coupling Power to Guides
• 3 common methods
– Probe: at an E-field maximum
– Loop: at an H-field maximum
– Hole: at an E-field maximum
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
54
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Attenuators and Loads
•
•
•
Attenuator works by putting carbon vane or flap into the waveguide
Currents induced in the carbon cause loss
Load is similar but at end of guide
Directional Coupler
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
55
TOPIC 2: WAVEGUIDE AND COMPONENTS
•
•
•
MICROWAVE DEVICES (EP603)
Launches or receives power in only 1 direction
Used to split some of power into a second guide
Can use probes or holes
BASIC ACCESSORIES (Passive Components)
•
•
Bends
– Called E-plane or H-Plane bends depending on the direction of
bending
Tees
– Also have E and H-plane varieties
– Hybrid or magic tee combines both and can be used for isolation
–
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
56
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
WAVEGUIDE BENDS
WAVEGUIDE TEES
TAPERED
TWIST
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
57
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
2.5.1 Explain the application of waveguide components:
Slotted section
Circulator and Isolator
•
•
Both use the unique properties of ferrites in a magnetic field
Isolator passes signals in one direction, attenuates in the other
Circulator passes input from each port to the next around the circle, not to
any other port
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
58
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Circulator Top View
PRECESSION
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
59
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
FERRITE ISOLATOR
MIXERS
What is a mixer?
The mixer takes two signals and combines them creating new signals. It can be
used to translate microwave signals into much lower frequencies that an
inexpensive radio receiver can tune. It can even reverse the effect taking low
frequencies and translating them back into the microwave range.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
60
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Is a two input signal device that performs the task of frequency conversion, by
multiplying two signals. Convert two input signals to sum-and-difference
frequencies Mixers are needed in most microwave systems because the RF
signal is way too high to process its information (for example, looking for a
Doppler shift in an X-band radar application, you won't find many A/D converters
than can handle 10 GHz!)
Schematic symbol for a mixer
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
61
TOPIC 2: WAVEGUIDE AND COMPONENTS
MICROWAVE DEVICES (EP603)
Mixer ports
There are three ports on a mixer,the radio frequency (RF) port, the local oscillator
port (LO), and the intermediate frequency port (IF).
The RF port is where the high frequency signal is applied that you want to
downconvert it, or where the high-frequency signal is output in an upconverter.
The local oscillator (LO) port is where the "power" for the mixer is injected. In this
case, the power that is applied is RF, not DC like it would be in an amplifier. The
LO signal is the strongest signal, and is used to turn the diodes on and off in a
switching mixer (which is nine out of ten mixers). The switching action effectively
reverses the path of the RF to the IF.
The IF port is where the RF signal that was modified by the LO signal is passed,
and its waveform is filtered to become the IF signal
2.6
Understand the attenuation in waveguide components.
2.6.1 List the sources of attenuation.
2.6.2 Apply formula to calculate the attenuation.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
62