Thanks for the guidance niki.......Get the following book from the library and read chapter 8.
Microstrip Filters
for RF/Microwave
Applications
JIA-SHENG HONG
M. J. LANCASTER
....
8. Coupled Resonator Circuits
8.1 General Coupling Matrix for Coupled-Resonator Filters
8.1.1 Loop Equation Formulation
8.1.2 Node Equation Formulation
8.1.3 General Coupling Matrix
8.2 General Theory of Couplings
....
Without cross-coupling, the synthesis is still easy. With cross-coupled resonators it becomes demanding.
If it helps, i can generate the polynomials for you. But i need a specification (passband(s), stopband(s), ripple, transmission zeros, etc.)
Thanks for the guidance niki.......
I have gone through the relevent content of the book, but its totally about the coupling technique, although its required but as a startup for this tech., I need polynomials for the synthesis of which I've faced several problems. The required specs are passband (5.5 to 5.85 GHz) i.e. 2 Tx zeros at these frequency points.The resonant frequency of the filter, fo=5.8GHz with 190MHz bandwith. while return loss/equiripple loss is 20-22 dB.
These para. are wrt the S parameter graph you can find in the attachment.Please check/correct the specifications:
passband from 5.5 to 5.85 gives a bandwidth of 350 MHz
center frequency f0=5.8GHz with 190 MHz leads to a passband from 5.705 to 5.895 GHz
Are the transmission zeros correct with 5.5 Ghz and 5.85 GHz ?
Possibly a typo somewhere...
These para. are wrt the S parameter graph you can find in the attachment.
Moreover, I also need a systematic explanation to implement filter synthesis by this technique. Till now, I have inferred that,
1) first we need polynomials S11 and S21 etc containing filter requirements (Tx zeros, ripples etc).
2). Make a coupling matrix using these polynomials.
3). now, Convert the coupling matrix coefficients into physical values of the elements (C or L) whic will be used in a physical structure of filter.
4). Thus design of a filter, completed.
Kindly make it confirm to me, is this understanding of mine is true or not?
For filter approximation, it is better to work with the so-called characteristic function K.
There you can directly tune the reflection and transmission zeros (see attachement).
To understand this, you need to completely solve a "simple example" by hand.
Afterwards you can use a good software tool for it. This topic is a bit tricky and takes some time to get started.
I will prepare an example, but I need some time.
Important: The theory is not easy to understand, it took me almost a year to study the relevant literature.
Regards
Peter
I will prepare an example, but I need some time.
Important: The theory is not easy to understand, it took me almost a year to study the relevant literature.
Regards
Peter
Current method for the synthesis is as follows:
1. Direct synthesis of the coupling matrix.
2. Transformation of the coupling matrix to get different topologies.
3. Extract physical dimensions.
For step 1 and 2 read the IEEE-papers
"General coupling matrix synthesis methods for Chebyshev filtering functions"
Richard J. Cameron.
"An analytical technique for the synthesis of cascaded N-tuplets cross-coupled resonators microwave filters using matrix rotations"
S. Tamiazzo; G. Macchiarella
In the appendix I have given a few examples. But I need more informations about the specs of the stopband(s).
For step 3 you need a software tool.
Some people have written algorithms and programs that replace handwork. But this requires deep understanding and a lot of effort.
You are a lucky guy if someone provides you with such a tool for free.
Questions:
Do you know the meaning of the polynomials F, P and E?
Have you already determined a transfer function yourself (using the characteristic function K=F/P)?
If not, then take a simple example in a book and trying to understand the example.
Without this knowledge, it is difficult to discuss the synthesis of a coupling matrix.
I can only help if I know what you know.
I can give you a simple example of a classic LC network, where you can see the use of the polynomials P, F and E.
What kind of info do you need?
Some people have written algorithms and programs that replace handwork. But this requires deep understanding and a lot of effort.
You are a lucky guy if someone provides you with such a tool for free.
Questions:
Do you know the meaning of the polynomials F, P and E?
Have you already determined a transfer function yourself (using the characteristic function K=F/P)?
If not, then take a simple example in a book and trying to understand the example.
Without this knowledge, it is difficult to discuss the synthesis of a coupling matrix.
I can only help if I know what you know.
I can give you a simple example of a classic LC network, where you can see the use of the polynomials P, F and E.
What kind of info do you need?
Answers:I don't think you have time to understand everything. You need a tool for the synthesis of the coupling matrix. I can deliver certain data, but I can't explain everything (it takes too much time).
Questions:
Which simulation software do you use?
Can you analyze a coupling matrix (frequency response)?
Do you understand the difference between a normalized and an unnormalized coupling matrix?
What concrete data should I provide to help you?
(frequencies, coupling factors, LC-values...)
Answers:
I have no tool at this time, for CM synthesis.
For simulation, I use HFSS.
No I cant analyze its spectrum
No, I cant understand the difference very well.
if have foundout this tool @Dedale@ https://www-sop.inria.fr/apics/Dedale/
it can be used to findout coupling matrix from order, polynomials etc info. Any suggestions from your side.
I have'nt try this, but , want to confirm whether this coupling matrix can be later on translated to some physical structre RLC
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