connecting coax to stripline

[nematollahi]

hi every one
I have a question. How should I connect coax line to the strip line with thick substrate .
I mean more longer than the outer radius of the coax.
Thanks a lot

 

[crutschow]

You connect the coax center conductor to the strip line and the coax shield to the ground plane with as short leads as possible. Ideally this should be done with a impedance controlled coax to PCB connector.

What is the highest frequency of interest?

 

[nematollahi]

hi dear friend.
Thanks for your attention.
Dosn't this manner lead to impedance missmatch?
is any transition needed?

 

[FvM]

Any coax to stripline connection already is a transition (e.g. involving an EM wave mode change). The transition can be optimized for minimal reflection up to a designed frequency, much more easily for a small band range. As crutschow mentioned, industry standard coax PCB connectors (either edge mount, surface mount or through connected will achieve this up to a certain extend. For lowest reflections, the transition can be empirically optimized with a TDR measurement setup, or using EM simulation. The optimization usually involves a modification of the stripline end segment.

 

[crutschow]

hi dear friend.
Thanks for your attention.
Dosn't this manner lead to impedance missmatch?
is any transition needed?

It depends upon the maximum frequency. To repeat, what is that?

 

[nematollahi]

The frequency is between 1.2-1.4 GHz
thanks