Post subject: Mircostrip highpass filter
Wed Jan 12, 2005 7:31 am
Nov 15, 2004 4:08 pm
I am working on a highpass
microstrip filter for stop frequency 40GHz on substrate:
The idea is that, one edge of the microstrip
is shorted to the groundplane which ensures, that DC and TEM, qTEM modes
are disabled in the structure.
Has anyone came across the problem??
Post subject: 40GHz high pass
Wed Jan 12, 2005 11:14 am
0.254mm=10mil, the circuit would nbever
work with 100mil thick substrate. The dominate mode in microstrip transmission
is quasi TEM (qTEM) so definetly do not want to squash that mode. There
are surface modes which need to supressed, especially at the higher
frequencise. If you have a board that you are testing then you will
need to wrap the ground plane around the edge or stitch vias to ground.
If this is part of a larger board then you will want ground plane at
the surface ~3-4 times the transmission line width away from the transmission
line. This will help suprress the surface modes. You do not want the
ground plane to close the transmission line or it willbegin to look
coplanar and the impedance will change.