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Coupled Microstrip Lines.

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BLUEeight

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Hi,

Asking about coupled microstrip lines assuming where two conductors are made in the upper layer...

Does these two conductors need to have the same shape?
Will it work if i made the first L-shape and the second L-shape with 45 bend?if so,what are the things i need to take it under account?

thank you.
 

FvM

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Does these two conductors need to have the same shape?
Any two microstrip segments with finite distance can be assumed to expose a certain degree of coupling, in most cases you'll want to place them quite near to achieve a considerable coupling. In other words, it depends on what you want to achieve.

Well defined coupling parameters can be obtained with parallel microstrip segments. Many elementary microstrip elements, e.g. directional couplers, are based on it.
 

BLUEeight

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The coupled microstrip line is following a 2.45Ghz oscillation circuit (Colpitts circuit).
So,the coupled microstrip lines are used to couple a small amount of energy from the oscillator...
Do the previously mentioned shapes related to this purpose?

thank you
 

FvM

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A lot of different geometries can be expected to serve the intended purpose.
 

BLUEeight

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A lot of different geometries can be expected to serve the intended purpose.

Could you suggest some helpful references about this topic?

thank you...
 

V

volker_muehlhaus

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Does these two conductors need to have the same shape?
Will it work if i made the first L-shape and the second L-shape with 45 bend?if so,what are the things i need to take it under account?

What couples are the straight lines segments. You could think of the L-shaped coupled lines as two coupled segments, with a bend between them. Here is the possible problem: The bend and the related extra line length will introduce some phase delay between the coupled lines segments. The "inner" bend path is shorter than the "outer" bend path. If that difference is relevant (relative to wavelength) you should simulate the layout. You can use model circuit based simulation (with coupled line and bend models) or EM simulation (free Sonnet Lite EM simulator or some commercial planar EM simulator).
 

tony_lth

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EM simulator is a little complex to do this topic.
AWR is very easy to do so if you can access AWR software.
Just set the coupled line model from the library, and even the bend has model also.
 

BLUEeight

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But the problem is that the first segment(45 outer bend) has an input but no output but in second segment(90 bend), one is
connected to ground layer (shorted), the other is the output of the whole coupling process.
by the way the operating frequency is 2.45Ghz.
Does this gives any clue about how this coupled microstrip is working?

One other question,Does knowing the first segment dimension gives clue about the second segment dimension?
 

tony_lth

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I don't understand your description, maybe a picture is better.
 

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