filter design help!!
3800-3999MHz -25db min
4000-5000MHz -40db min
5000-14999MHz -60db min
15000-20000MHz -20 min
I used coaxial structure and synthesized and optimized it with senerade.
But -60dB seemed impossible to me.How can I get it?Please help me!
You can use two filters. If you connect their in series.
I think you should use some other technology then coaxial on these frequencies (microstrip, stripline etc...). Try to use eliptical or so-called cross-coupled resonator filter to get to -60dB attenuation. You should use some more sofisticated synthesis tools to do so, it is quite a theory to read.
I had roughly the same filter requirement once. Solved by implementation in a narrow channel stripline, giving sufficient suppression (minor leakage through the filter).
dear flyhigh:
Can you tell me some about cross coupled filter?
Your problem can be parasitic pass band since you must have more of 5 fc free. I suggest 2 filters in series if your IL can take it.
Here is excellent article about cross-coupled resonators, hope it can help.
D.
Microwave boy,
below is a link for an article about cross coupled filters
hxxp://www.shively.com/tb-cross-coupling.pdf
(x=t)
rgds, Al