Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
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Below are all of the forum threads, including all
the responses to the original posts.
Post subject: filter Posted: Tue Nov 14, 2006 6:57 am
Joined: Tue Nov
14, 2006 6:50 am
I'm facing a problem in High pass filter design
realised using suspended substrate stripline. the filter cutoff frequency is 16 GHz. Return loss near cutoff is
very poor (-6 dB) and rejection is not monotonically decreasing. it falls down very sharply upto -40 dB
(typically) and then increases by 2 or 3 dB and remains constant at that level. I have tried various combinations
of substrate parameters, number of elements etc.. Can u please help me out?
DEFENCE ELECTRONICS RESEARCH LAB
Post subject: Posted: Tue
Nov 14, 2006 7:48 am
Joined: Fri Feb 17, 2006 12:07 pm
We would need to know a little more about the filter design type: is it Butterworth, Chebychev or
Elliptic Function? Also how many poles?
The last 2 types have strange behaviour near the -3dB cut off
If the cutoff roll-off rate in the stop band is very high it suggests an Elliptic Function or
Chebychev filter, and the behaviour may be quite normal for that type.
They are used when you know the max
frequency can be set somewhat below the max design frequency, but you have several products or external carriers
not far removed from the wanted carrier, and you need max attenuation of these. The subsequent sidelobes of the
filter then can remain the same level once they have been eliminated.
So, tell us more.