cpw to cps transition
I have recently involved designing an dipole antenna with a feeding transition using Coplanar Wavguide (CPW) to Coplanar strip line (CPS). Anyone here had any experience before on how to assign the ports for it either in HFSS or in ADS Momentum?
p.s. Attached two files are my designs. one (hhyap4.rar) is my modelling in momentum (ads2005A) and the other (switch balun dipole.rar) is modelled in hfss v9.2.
Thank you for your help in advance!
If you are feeding the structure with a CPW, you can find plenty of information in the EM simulation forum in this board about feeding a CPW in HFSS. A simple search will get you the threads with the files attached.
Ananth.
Hi Ananth,
Thank you for you time for my post. My problem is not actually about how to feed CPW, it is about how to assign the port for CPS? do you have any ideas?
Regards.
can anybody here help me out, please?
I guess your CPS is 100 ohm differential line pair. In termianl mode solution, a wave port should be used with two impedance lines drawn from the same reference plane to the lines. Then u can assign them as a differential pair with a reference impedance, say 50 ohm. You can check the actual port impedance by carrying out solve port only firstly and then run the full wave solution. Hope it helps.
Hi kenneth, Thank you for your concern about my problem. what i actally wanted to solve is to measure the balanced magnitude and phase out of the two output ports. like you suggested, the simulator will consider the outputs as one-port output. it does not help me in my question. regards. any comments on that?
I have made some modifications to your file, take a look.
I do not think there is anything wrong with your model it is just
the frequency is off.
Placing ports on CPW/CPS transmission lines can be a trick, particularly if you are using differential lines. You now get into an issue of whether they are tightly or loosely coupled as well.
Read the notes on impedance calculations (Zpi, Zpv, etc.) in the HFSS help sections. Those transmission lines are "mode rich". I would examine the fields and modes at each port to make sure you have the excitation you expect and you are using the appropriate impedance calculation. Be sure to ask for multiple modes when you start the simulation and then back off when (if) you get the mode you want as the first or second mode.
Simon and Wadell have helpful books on the subject and if you can get to an impedance tool like Polar Instruments as a rough check on things I would recommend that too. It is in no way a substitute for HFSS but it may catch a mistake if things go wrong.
I am currently messing with a similar problem using HFSS 11 (beta) and am not convinced that I have it in hand. Apparently there has been significant work in this area and it is easier to manage than in HFSS 10.3. Maybe I will get a little quiet time to work with this soon.