how to simulate a lambda/4 SIR bandpass filter in cpw stru?
I am implemanting the paper(IEEE MTT-S Digest) "λ/4 stepped impedance resonator bandpass filters fabricated on coplanar waveguide." I meet with a trouble in simulation one resonator section of a bandpass filter in cpw structure,which is shown in the figure.
I want to konw how to set the two ports in the structrue as shown in the figure and in the paper when simulating the λ/4 stepped-impedance resonator with IE3D or Ansoft Designer.
In addition I wonder how the two lengths of different impedances( lL and lH in the figure and paper) can obtain from scattering parameters calculated by simulations for the structrue shown in figure.(cited in the paper)
I attach the figure and the paper respectively.
Hi, flywke:
From what I see, you just create the series of resonators and define two CPW ports on both ends. You have 3 conductors for each end, you can define the center conductor as +1 port and the two side conductors as -1 and -1 ports.
Best regards,
Jian, thank you for your suggestion.
I want to obtain the structural parameters in the figure attached as a unit of the series resonators by simulations. So I need to set the input and output ports for simulation in IE3D or Ansoft Designer.
What I want most is How to define the two ports in the structure in the figure attached.
By the way, what's mean for the -1 port? I am not sure the ports can be set on the groud conductor plane but not the strip conductor in the cpw structure.
Hi, flywke:
Each section is quite short. If you want to divide it, I would suggest you to divide it at the center of the l_L and/or l_H segments. When you divide it, you will have 3 conductors. On IE3D, you can define the center conductor as port 1. Then, you select Port->Define Negative Port and define one of the side conductor as -1 port. Repeat it for the other side conductor for a (-1, 1, -1) port. If you break the structure in this way, you are able to simulate portion of the structure. You can use circuit simulator to connect the s-parameters to find the final s-parameters. You certainly can try to optimize each segment for the performance you want. This might be the only way you can simulate it as sub-structures. It does not seem to me you can define the whole CPW lamba/4 SIR as a sub-circuit because you can find a place to define a port. Regards.
Jian,Thank you very much for your patient analysis.
Would you please offer me some examples or tutorials in IE3D or Ansoft Designer? It seem to me that I am not familiar with the design of the bandpass filters. Would you please introduce some information to me. Thanks a lot.
flywke
My email : flywke@hotmail.com
Hi, Flywke:
This is not just on filter design. It is also the stratey in modeling of large circuit and antenna structures. Give you a large circuit, how can you simulate it? We need to divide it into sub-circuits and find the s-parameter of the complete circuit by cascading the s-parameters of the sub-circuits. When we divide a large circuit into a number of sub-circuits, we may or may not get accurate results on the large circuit depending upon how we divide it into sub-circuits. The cascading of the sub-circuits is based upon microwave network theory. Microwave network theory assumes a circuit consists of a number of discontinutiies connected by single moded transmission lines (TLNs). In order to be able to use microwave network theory to obtain accurate results on the large circuit, we will need to make sure the sub-circuits are separated with uniform sngle moded TLNs.
If you look at the CPW filers. The power transferring between sections of lambda/4 is thru coupling between the discontinuities. It is not from a TLN connecting between them. Therefore, you can't separate a section of lambda/4 as a sub-circuit. You have to divide it where you have uniform single mode TLNs. That is the key point.
Best regards,
Thank you for your suggestion, Jian
Sorry for my late words because of my trip.
I will try immediately.