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Waveguides

GUIDE TYPE TE11MODE
CUTOFF
[GHz]
MAXIMUM
FREQ. RANGE
[GHz]
ATTENUATION
[dB/100mt]
MAX POWER
[W]
VELOCITY FACTOR
 
EW 127 A 7.67 10.0 - 13.25 11.83 1.24 0.78
EW 132 9.22 11.0 - 15.35 15.84 0.85 0.78


WAVEGUIDE
A few basic facts about waveguide:
  • The "WR" designation stands for "waveguide, rectangular"
  • The wide inside dimension in inches is the "xxx" part of WRxxx; ie, WR650 is 6.50 inches, WR90 is 0.90 inches.
  • The TE10 mode of propagation is the lowest mode that is supported.
  • The waveguide width determines the lower cutoff frequency and is equal (ideally) to ½ wavelength of the lower cutoff frequency.
  • The TE20, occurs when the width equals one wavelength of the lower cutoff frequency, and so on for higher modes.
  • The TE01 mode occurs when the height equals ½ wavelength of the cutoff frequency, and so on to higher modes.
H-Bend E-Bend
An H-Bend is bent in the Hard direction (along the long side). This is the direction of the H-field in the TE10 mode. An E-Bend is bent in the Easy direction (along the short side). This is the direction of the E-field in the TE10 mode.


RECTANGULAR WAVEGUIDE
Cutoff frequency
The lower cutoff frequency (or wavelength) for a particular mode in rectangular waveguide is determined by the following equations:
(Hz)
(m)
where

a=
b=
m=
n=
e=
m=

Inside width
Inside height
Number of ½-wavelength variations of fields in the "a" direction
Number of ½-wavelength variations of fields in the "b" direction
Permittivity
Permeability
     
TE (Transverse Electric) Mode
The TE10 mode is the dominant mode of a rectangular waveguide with a>b, since it has the lowest attenuation of all modes.
Either m or n can be zero, but not both.


End View (TE10)

 
Side View (TE10)


Top View (TE10)

____ Electric field lines
_ _ _ Magnetic field lines

TM (Transverse Magnetic) Mode
For TM modes, m=0 and n=0 are not possible, thus, TM11 is the lowest possible TM mode.


End View (TM11)

 
Side View (TM11)

____ Electric field lines
_ _ _ Magnetic field lines



CIRCULAR WAVEGUIDES  
TE (Transverse Electric) Mode  
The lower cutoff frequency (or wavelength) for a particular TE mode in circular waveguide is determined by the following equation:
(m),

where p'mn is

m p'm1 p'm2 p'm3
0 3.832 7.016 10.174
1 1.841 5.331 8.536
2 3.054 6.706 9.970
TM (Transverse Magnetic) Mode
The lower cutoff frequency (or wavelength) for a particular TM mode in circular waveguide is determined by the following equation:

(m),

where pmn is

m pm1 pm2 pm3
0 2.405 5.520 8.654
1 3.832 7.016 10.174
2 5.135 8.417 11.620
 
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