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I've found this very simple and old, yet very efficient DOS public domain application many years ago.
Uncompress this file, open a DOS command window and type "RFDESIGN" to start the aplication.
Also included an old version of the PC-ECAP shareware (Yep! Another DOS application!). PC-ECAP is an excellent program to get the frequency/phase response/transient/Return_loss-VSWR of an active/passive filter.
What kind of filter u r going to design -digital or analog ? u can use Matlab and a free software circuit maker for realization ur ckt. and for better understanding it from theoritical point of view u can see the book of flter designing by Ian Hunter or by G.L.Mettahei
You can do two things, either use a simulator and play with it after getting a basic feel for the filter. The better option is to use the equation for the elliptic filter, have you tried searching the web?
I am sure ADS can help you since it has filters in it.
I feel the time has come to make some general statements on filter design.
For example, just to say “I like to design an elliptical filter” is completely insufficient and nobody can give a substantial answer to such a question.
Instead, the design has to follow some steps in the right order:
1.) Frequency and attenuation requirements
2.) Choice of an approximation (out of at least five alternatives)
3.) Filter order (as a consequnence of steps 1 and 2)
4.) Choice: passiv or active
5.) Selection of technology (opamp, OTA, SC, CC)
6.) Choice of synthesis procedure: Cascade design or direct (ladder simulation ,leap frog, FLF, PRB)
7.) Selection of a specific circuit (Sallen-Key, MLF, several Biquads, FDNR,………)
Did I forget something ?
You see, filter design is connected with several design steps. For example, to build a lowpass of only second order you have at least 20 alternatives.
But, how come to a decision and what governs the choice ? Several aspects, like component availability, cost, power and supply voltage requirements, frequency range, tuning capabilities, accuracy requirements, ………
And don´t think, that the problems rise with frequency; to design an active lowpass for a pole frequency of 10…100 mHz is a big problem.
Perhaps this helps somebody a bit.
Regards.
To find one set of component values (out of infinite variations) one can use
- formulas to be found in relevant textbooks, or
- filter design software.
However, one should be aware of the fact that - according to my knowledge - all filter design programs are based only on a very limited number of circuit alternatives.
More than that, as far as filter orders higher than two are concerned, the most powerful circuits (active ladder simulation) are not considered by these programs (with one exception: Filter-Solutions from Nuhertz-Tech.)
Step1. from system requirement , we choice a best filter type. Step2. from filter spec, compute N and（N round up to an integer）.
Step3. compute a.
Step4. compute sinh a, cosh a.
Step5. compute filter’s poles.
Step6. compute pole frequency and pole quality factors of filter.
Step7. compute stop band attenuation when N round up to an integer.
Step8. get LC-Ladder prototype.
Step9. compute filter’s transfer function.
Step10. synthesize parameter of every stage from filter transfer function.
Step11. compute filter amplifier parameters.
Step12. filter amplifier design.
Step13. complete filter design basic .
Step14. filter phase compensation design.
Step15. stability analysis under large signal.
Sdtep16. filter auto calibration design.
Step17. done.
Added after 2 minutes:
you may should do filter phase compensation design, i surgest you using active compensation.
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