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filter - RF Cafe Forums

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 you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


lalitha
Post subject: filter Posted: Tue Nov 14, 2006 6:57 am

Lieutenant

Joined: Tue Nov 14, 2006 6:50 am
Posts: 1
Location: HYDERABAD
Sir,
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?
thank you

_________________
LALITHA SARIPAKA
DEFENCE ELECTRONICS RESEARCH LAB


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nubbage
Post subject: Posted: Tue Nov 14, 2006 7:48 am

General


Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
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 frequency.

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.



Posted  11/12/2012
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