unsual results when I increase the length of CPW in IE3D

Hi ,

please can anyone help me out with this,
i was trying to design directional coupler with CPW and microstrip in ie3D, i got good results but when i try to increase the length of the CPW the magnitude of S parameters should not change only phase should change , but my problem is everything has changed.

i am using the infinite ground plane.

thanks,
swapna

Hi, swapna2009:

If the CPW line is not close to 50-ohms, the magntitude will change with length because the s-parameters are normalized to 50-ohms instead of the port impedance. Regards,

hi jian,
first of all thanks a lot for your reply, I was verified so many times but Cpw line is 50 ohms impedance only. i am using the differential ports for CPW, and one more thing is before increasing the length of CPW S parameters are going above 0 dB at lower frequencies, after increasing the length of CPW those type behavior is not appeared that means s parameters are below 0 dB at all frequencies,

can u please suggest me what may be the mistake?

thanks,
swapna

hi there,
I'm seraching for a method to have best W, G and L parameters in CPW Line when I would change microstrip/Cpw.

I used to work with LineCalc in ADS, but, I get some unusal resluts comparing with the same microstrip design!

I think that I need help, may be I'll get solution
thx in advance

Hi, swapna2009:

You can send me the related files and I can have them checked.

hello jian,

sorry for the delay, i sent those files to your jian(at)zeland.com e-mail.

please check them once.
thanku so much

swapna

hi swapna ,iam solving an IEEE paper..design of an antenna for UWB(3.1-10.6 Ghz) using CPW feeding.How to define ports for this CPW feeding ,can you help me out ?
I am attaching my .geo file...Can u please put the ports and upload me...it is very urgent to me, i have to submit the results in 1 week..tnx in advance

hello naresh,

i have updated that file with CPW ports, just run it once , and let me know whether u get desired results or not.

good luck

bye.

i to used same type of port definitions..but it didnt cover uwb range..is there any other option to get the results ..

i guess problem is not with port definition, r u sure about impedance matching? i mean correct dimensions of cpw?

Hello swapna,
dimensions are correct as per the ieee paper..if u want just check it out ,iam uploading paper..and tnx for the reply

Hi there!

I have exactly the same problem with AWR!
Did you guy find the smoking gun ?
Thanks in advance