What are the insertion points in a waveguide?

[evoplus]

Question on waveguide

Hi everyone,

I came across a book that says that a dielectric material can cause reflections at the insertion points in the waveguide. So what are this insertion points in the 1st place? Where are the locations of them in the waveguide?

Thanks

 

[truebs]

Re: Question on waveguide

First point to understand is that waveguides are not like oprdinary wire conductors where we just join source to wire to get it connected.
When a source is connected to microwave, it is neccessary that the source and the waveguide match in impedance, otherwise reflections take place.

You might be aware that whenever any EM wave travels ,it is reflected unless it is propagating through an infinite line (in this case all reflected power = 0 ).
However conditions similars to infinte length can be achieved if the source and destination have same impedance.

when a source is connected to waveguide the discontinuities act as reflection points.
If the impedance of wavguide is same as source, the source finds it as an infinite line and hence no reflections take place.
In case of even slightly different impedacne would cause reflections.

About insertion points ...
Well whenever you insert some probe in waveguide...if it has a different impedance.,it would cause reflection.
However if macthed it won't.
Hence at any point in waveguide where a impedance mismatch can occur, becomes insertion point and leads to reflection.

Please refer to any book on " Communication netwroks" or " Wave propagation " for more details.