This presentation is about waveguides and covers the following topics: -Waveguides -Types of waveguides -Rectangular waveguides -Circular waveguides

1. Waveguides
Author: Irfan Sultan
Instructor (Telecom.)
Govt. College of Technology

2. Contents
 Understand the term “Waveguides”
 Discuss Rectangular Waveguides
 Discuss Rectangular Waveguide Modes
 Define Circular Waveguides

3. Introduction to Waveguides
 In electromagnetics and communications engineering, the term waveguide may
refer to any linear structure that conveys electromagnetic waves between its
endpoints. However, the original and most common meaning is a hollow metal
pipe used to carry radio waves.
 A waveguide is a type of transmission line which is used to convey an EM-wave (or
Sound-wave) from one place to another.
 A waveguide is normally looks like a hollow metal pipe. Hence there are three
types of waveguides w.r.t. their shape:
 Rectangular
 Circular
 Elliptical

4. Waveguide Types
Rectangular
Circular
Elliptical

5. Waveguides: Principal of Operation
(Optional)
 Depending on the frequency, waveguides can be constructed from either
conductive or dielectric materials. Generally, the lower the frequency to be passed
the larger the waveguide is.

6. Rectangular Waveguides
 A rectangular waveguide basically consists of four metallic surfaces:
 2 Side Walls
 1 Upper Surface
 1 Lower Surface
 When an EM-Wave is inserted at a specific angle in the waveguide it reflects
towards its lower surface after striking the upper surface. It then strikes the lower
surface after travelling some distance. This procedure continues and the EM-Wave
reaches the other end of the waveguide and leaves the waveguide.
 Note: The incident and reflection angles are equal.

7. Rectangular Waveguides
 Waveguide can also be designed from a two wire line. To achieve this purpose a
stub is attached to one side of a two wire transmission line and stubs of the similar
size are also attached to the other side of the line. If this process is repeated with
infinite stubs, as shown in the figure, then we get a structure that looks like a
rectangular pipe and can be used as a rectangular waveguide.

8. Rectangular Waveguide Transmission
Modes
 Energy that travels in transmission lines consists of electric and magnetic fields. There
are many ways to transmit this energy.
 The methods by which EM waves travel are called transmission modes.
 Basic three of them are given below:
 Transverse Electric (TE) Mode
 Transverse Magnetic (TM) Mode
 Transverse Electric and Magnetic Field(TEM) Mode (Note supported in Rectangular
Waveguides)
Note: TEM mode is not supported in hollow conductors (i.e. Waveguides), it is supported in
two wire transmission lines used at lower frequencies such as coaxial cable, parallel wire
line and strip-line.

9. TE Mode
 TE Mode: In this mode, Electric field is perpendicular to the direction of propagation.
 TM Mode: In this mode, Magnetic field is perpendicular to the direction of propagation.

10. Circular Waveguide
 This type of waveguide is a transmission line which carries EM waves from one
place to another and is circular in shape.
 Circular waveguides basically consist of only one surface which is circularly wound
so that it forms the shape of a pipe.
 These are normally used at places where EM waves are to be conveyed to an
antenna which is rotating.
 If they are used to carry EM waves from one place to another, just like rectangular
waveguides, then the polarization of EM wave may change. Hence they are not
used to carry EM waves to long distances.