Rectangular waveguides are the most commonly used form and carry signals above a certain cutoff frequency. They propagate electromagnetic waves in different modes depending on whether the electric or magnetic vector is perpendicular to the propagation direction. For rectangular waveguides, the width determines the lower cutoff frequency and the TE10 mode is the lowest supported. Circular waveguides are less common but used when a rotating element is attached; they support all TEmn and TMmn modes with the dominant mode being TE11.

1. WAVEGUIDES
CALDERON
DE GUZMAN
QUITEVIS

2. RF Waveguides
• Form of RF feeder used for microwave
applications
• Used in a variety of applications to
carry radio frequency energy from one
point to another
• System of material that is designed
to confine electromagnetic waves in
a direction defined by its physical
boundaries

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

4. RF Waveguide
TYPES

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

6. Circular 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.

7. Circuit board stripline
• 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.

10. Waveguides
Theory of Propagation

11. • According to waveguide theory there
are a number of different types of
electromagnetic wave that can
propagate within the waveguide.
These different types of waves
correspond to the different elements
within an electromagnetic wave.

12. TE Waves
• Transverse electric waves, also
sometimes called H waves, are
characterised by the fact that the
electric vector (E) is always
perpendicular to the direction of
propagation.

13. TM Waves
• Transverse magnetic waves, also
called E waves are characterised by
the fact that the magnetic vector (H
vector) is always perpendicular to
the direction of propagation.

14. TEM waves
• Cannot be propagated within a
waveguide, but is included for
completeness. It is the mode that is
commonly used within coaxial and
open wire feeders. The TEM wave is
characterised by the fact that both
the electric vector (E vector) and the
magnetic vector (H vector) are
perpendicular to the direction of
propagation.

16. Waveguide Theory
Rules of Thumb

17. • For rectangular waveguides, the
TE10 mode of propagation is the
lowest mode that is supported.
• For rectangular waveguides, the
waveguide width, i.e. the widest
internal dimension of the cross
section, determines the lower cut-off
frequency and is equal to 1/2
wavelength of the lower cut-off
frequency.

18. • For rectangular waveguides, the
TE01 mode occurs when the height
equals 1/2 wavelength of the cut-off
frequency.
• For rectangular waveguides, the
TE20, occurs when the width equals
one wavelength of the lower cut-off
frequency.

19. Waveguide Impedance
• Where Zo = 120(pi) or 377Ω for air
filled waveguide

20. Circular/Cylindrical Waveguides
• Waveguide having a circular cross-
section, used whenever a rotating
element (radar antenna) should be
attached to the transmitter/receiver.

21. • Differences versus rectangular
waveguides:
• Where
– R = waveguide radius
– Bmn = Bessel function solution for a particular
m,n mode being propagated
• =1.84 for the dominant mode of operation
All TEmn and TMmn modes are supported
since m and n subscripts are defined
directly.
Dominant mode is TE11.

22. Advantages Disadvantages
• High power- • Polarization
handling capacity may rotate
• Lower
attenuation for a
given cutoff
wavelength