Help me to design an LC filter

[david753]

I am researching the LC filter deign now.
Please refer to following link,
**broken link removed**

I got the circuit as case2 when I use ADS wizard to design it.
But, the middle Inductor is too big to design it.
So, someone taught me to change to the case1's model insteasd of case2 model.
The inductor is eliminated, and there are 2 capacitors are added in both sides.
I was confused in the circuit of case1.
I don't know how to design filter that structure as case1.
Meanwhile, in ADS wizard, It seems to produce the circuit as case2 only.

 

[flatulent]

Re: LC FILTER design

Case 2 is a direct transform from the prototype low pass type. Case 1 is a top couples resonator type. It was invented by a famous acoustics person at Bell Labs around 1930 or so. It is somewhat like the two tuned circuits that are inductively coupled in the old IF transformers.

For the design, you select the inductor values on your own choice. The parallel capacitors resonate them very near the passband frequency. The coupling capacitors set the bandwidth and to a small degree the passband frequency. You can use the CAD optimizer to vary all of the capacitor values for the passband you want.

 

[david753]

Re: LC FILTER design

Case 1 is a top couples resonator type. It was invented by a famous acoustics person at Bell Labs around 1930 or so.

Does anyone can tell me where I can find more information about this filter design?

 

[biff44]

Re: LC FILTER design

You do know that these are not the same filters, and are not equivalent. Case 1 is a 2 pole bandpass, and Case 2 is a 3 pole bandpass.

 

[david753]

Re: LC FILTER design

what is the name of case 1 model?
It is different structure comparing than tranditional filter type, such as butterworth, chebyshev, besel...etc.
why?
where can I get more information about it?

Added after 1 minutes:

what is the name of case 1 model?
It is different structure comparing than tranditional filter type, such as butterworth, chebyshev, besel...etc.
why?
where can I get more information about it?