Hello all!
Assume we have TE10 waveguide with slots.
I have some confusion, which comes from here:

it is written that (slot A) will radiate,
and (slot B) will NOT radiate

2) http://www.antenna-theory.com/antenn...dWaveguide.php

Figure 2. Waveguide with a thin slot centered about its width.
it is written that slot similar to (slot A case 1) will NOT radiate (opposite statement to case 1)

Figure 3. Horizontal slot in a waveguide.
it is written that slot similar to (slot B case 1) will radiate (opposite statement to case 1)

3) http://www.qsl.net/n1bwt/ch7_part1.pdf
explains things a little on page 4:
Therefore, a slot in the exact
center of the broad wall of the waveguide will not radiate at all, since the electric field is symmetrical
around the center of the guide and thus is identical at both edges of the slot. As the slot is positioned
away from the centerline, the difference in field intensity between the edges of the slot is larger, so
that more current is interrupted and more energy is coupled to the slot, increasing radiated power.
it seems that radartutorial.eu website waveguide image current distributions are somehow wrongly placed (wide wall current distribution is shown on narrow wall)?

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2. ## What is the purpose of "U" shaped slots in this slot antenna?

I found an image of slot antenna here: http://cn.comsol.com/model/substrate...-antenna-16021
What is the purpose of small short 90 degree angled slot extensions at both ends of each slot? What is the idea behind this? I did not found such slot configuration in slotted waveguide papers.

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as far as the 90 degree ends of the slots in the Comsol example. I would guess the total length of the slot, including the two tabs at the end, is approximately half wavelength, so that it resonates. Then the two 90 degree tabs are coupling energy from the waveguide (near those top edges of the waveguide are maximum current flow points).

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It think that you are right about total slot length (including 90 degree parts) and excitation frequency.

Still not sure about current distribution here (te10 waveguide):

and here:

(at the bottom of page http://nptel.ac.in/courses/117101057/Slides-6/7.4.html)

The second image seems to be correct.

I have a new question about SIW (substrate integrated waveguide) to microstrip line taper transition.
There are different formulas to calculate such taper. One approach is to calculate waveguide impedance.
I was given few formulas:
ZTE=Sqrt(MU/E0)*LG/LAMBDA
ZPI=ZTE*Pi^2*B/(8*AS)
where AS is SIW dielectric filled waveguide (DFW) width
(AS formula from http://www.microwaves101.com/encyclo...ated-waveguide)
As i understand, waveguide impedance ZPI then can be used to calculate microstrip line width (connected to SIW). Is it correct?

To clarify:
50 ohm microstrip - > quarterwave transformet to ZPI -> ZPI of SIW waveguide
50 ohm microstrip - > taper from 50 Ohm to ZPI -> ZPI of SIW waveguide
or ZPI can't be used in such way?

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