Waveguides

Electromagnetic waves are carried from one point to

the other by many means such as coaxial cable, two
wire line, optical fiber, microstrip lines, waveguide
etc.
The waveguide is the hollow metallic conductor
carrying usually high frequency or microwave
frequency.
Operating range (approx.): 300 MHz to 300 GHz.
High Pass Filter
passive microwave device.
cut off frequency: If the operating frequency lies below the waveguide
cutoff frequency, propagation does not take place and wave is said as
evanescent.
Power loss occurs in the walls of waveguide due to induced current, in
order to reduce this loss walls are designed with as much low resistance as
possible.
Waveguides are made from copper, aluminum or brass. These metals are
extruded into long rectangular or circular pipes.
High power handling, low loss.
Bulky and Expensive
In order to determine the EM field configuration within the waveguide,
Maxwell’s equations should be solved subject to appropriate boundary
conditions at the walls of the guide.
Such solutions give rise to a number of field configurations. Each
configuration is known as a mode.
GENERAL SOLUTIONS FOR TEM, TE, AND TM WAVES (Ref. David
M. Pozar)
TEM
TE
TM
Modes of Propagation
Rectangular Waveguide • Available Frequency
Range: 320 MHz to 333
GHz.
• WR-2300 at 320 MHz
(58.42 in by 29.1 in)
• WR-90 for X-Band (0.9
in by 0.4 in), (2.286 cm
x 1.016 cm)
• WR-3 at 333 GHz (0.034
in by 0.017 in)
Rectangular waveguide Waveguide to coaxial adopter

Waveguide bends E-tee

• Electric and magnetic
fields are confined to
the space within the
guide
• No power loss due to
radiation
• Dielectric loss negligible
• Some power loss as
heat in the wall, the
loss is very small.
 H

C
Wave propagation
Cutoff frequency
Attenuation:
• Losses in the guide walls
• Losses in the Dielectric
 Ref: Cheng

Ref: Robert E. Collin