Re: IE3D sim. confusion
hi could you send me the ie3d sofware to me please i am waiting for your replyat:malladihari@gmail.com[/u][/b]
Hello All,
I would like to comment about the repetitive behaviour of transmission line filters. The repeating passband is an inevitable property of transmission line filters. Let me explain with a simple end coupled microstrip BPF.
Just try to think what waves can be sustained in the strip. For a wave to be sustained it has to satisfy the boundary conditions at the edges. Usually the strips will be (lambda/2) long so that it has zeros at its ends which is needed by the open at both ends of the strip. So this is kind of dominant mode in the microstrip. The same condition (zeros at the ends of the strip) can also be satisified when the length is equal to lambda. So it means the same microstrip will resonate at twice the frquency as well. So if the lowest resonant frequency is fres, the the pass bands will appear at 2fres, 3fres,....n*fres. The second resonant frequency is usually termed the spurious pass band (SPB). This cant be altered by simply adding more elements. This can only be controlled by suitable taking the resonant lengths. Whats usually done is that the lines are usually less than 90degs and are then compensated by reactive elements.
Please see, Matthaei's book (Pg 422). Please ask me if you have any other doubts.
Added after 6 minutes:
The SPB can also be supressed by using resonant stubs as some have already mentioned. These introduce what are known as attenuation poles.
One more thing about FilterSyn. For stripline designs, I dont know whether the modelled output is reliable or not. I had even mailed them asking for benchmark results and also the method they had used but, I failed to get any response from them. It lacks good documentation also.
On the other hand CocaFil uses mode matching method and I had even tried the designs with Fidelity and there was a very good match. So CoCaFil is very good.
Just one word about the use of synthesis softwares (No offenses please). Please avoid using synthesis tools as much as possible. Usually the design methodology is not so complicated and it can be implemented on C or MATLAB. This will definetly help us as we will realize the different caveats during the synthesis procedures.
All the best
Hi, priyankguddu:
FilterSyn is based upon analytical formulas only. Its accuracy can't be guaranteed. However, it can serve as the starting point for further full-wave EM optimization on IE3DLibrary. You are able to get some initial design close to the final result even it may not be perfect, and it still helps to save time and achieve the final goals.
Regards,