Waveguide Designations, Paul Goble (ND2X/5

Waveguide is the mysterious "pipe in the sky". It has its own terminology set, such as WR-90, flex guide and the like. In this case, Paul has compiled a nice table of names used to define waveguid.


Introduction:

Waveguide was invented in 1932 at Bell Telephone Laboratories.  It is a very low-loss means to convey a microwave signal between antenna and the transmitter-receiver systems.  (It has a small fraction of the loss per foot of almost any coax.)  The pipe-like waveguide used to adorn the corners of the boxy ATT microwave relay towers scattered every 100 miles or so across the countyside... before optical fiber.

Waveguide may be rectangular or round.  (Yes, you really can use 3/4" copper water pipe at 10 GHz... if you're careful!)  Rectangular often found easier to work with from the standpoint of propagation mode stability, the standing waves set up within the pipe.  Waveguide is sized for the wavelength of operation, so higher frequencies use smaller waveguide.

There is an lower limit ("lower cutoff frequency") at which a signal won't propagate down a waveguide.  The lower cutoff is determined by F(Ghz) = c/(2*a), where a is the width of the broad wall (in cm). ;nbsp;For example, WR-90 has a cutoff of 6.56 GHz. To explore this further, consult Microwaves 101 for a practical treatment of the matter.

Various agencies have created their "standard" name for the various waveguide types. Some people find EIA'a WR- nomenclature easier to remember because the type number is the width of the waveguide in hundreths of an inch. For example, the above WR-90 is 0.90" wide (I.D.).

That said, the non-standard standards for waveguide are given in the table below. Even though the table itself has a lower cutoff frequency of 1.12 GHz, waveguide has been used to transport high power UHF signals at 420 MHz. (At that frequency, though, you can no longer stuff a length of it into your pocket; you do the math!)

Here's the table:

Frequency
Range
(GHz)
Waveguide Designations I.D.
(inches)
IEC
(R-  )
EIA
(WR-  )
British
(WG-  )
JAN
(RG-  )
    1.12 - 1.70 14 650 6 69,  103 6.50X3.25
    1.45 - 2.20 18 510 7 - -
    1.70 - 2.60 22 430 8 104,  105 4.30X2.15
    2.20 - 3.30 26 340 9A 112,  113 3.40X1.70
    2.60 - 3.95 32 284 10 48,  75 2.84X1.34
    3.30 - 4.90 40 229 11A -  - 2.29X1.145
    3.95 - 5.85 48 187 12 49,  95 1.872X.872
    4.90 - 7.05 58 159 13 -  - 1.590X.795
    5.85 - 8.20 70 137 14 50,  106 1.372X.622
    7.05 - 10.00 84 112 15 51,  68 1.122X.497
    7.00 - 11.00 - 102 - -  - -
    8.20 - 12.40 100 90 16 52,  67 .900X.400
    10.00 - 15.00 120 75 17 -  - .750X.375
    12.40 - 18.00 140 62 18 91  -  107 .622X.311
    15.00 - 22.00 180 51 19 -  - .510X.255
    18.00 - 26.50 220 42 20 53,  121,  66 .420X.170
    22.00 - 33.00 260 34 21 -  -  - -
    26.50 - 40.00 320 28 22 -  -  96 .280X.140
    33.00 - 50.00 400 22 23 -  97 .224X.112
    40.00 - 60.00 500 19 24 -  - .188X.094
    50.00 - 75.00 620 15 25 -  98 -
    60.00 - 90.00 740 12 26 -  99 .122X.061
    75.00 - 110.00 900 10 27 -  - .100X.050

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