CPW taper design (linear and exponential)

[muhammad.usman]

Hello,

I am trying to design a CPW taper. How can I make sure that my tapered CPW is 50 ohm?
Any one has suggestions or guidelines which one can follow?

I am also interested in exponential tapering. But couldnt figure out exactly how to taper in HFSS?

Youe help will be appreciated.

Thanks,

Usman

 

[johnjoe]

do you want a transition from microstrip to cpw or a cpw - cpw transition?

 

[muhammad.usman]

Actually I need a CPW-CPW transition. I am attaching an image file which shows the transition. It starts with CPW which is tapered to CPW again. The GSG tapper is sitting on to substrate directly then the middle section metal is sitting on layer of semiconductors. Then the output CPW is again another tapper.

Could you suggest what scehemes I can follow and any reference would be very very helpful,

Thanks,

 

[johnjoe]

Sorry, but you failed to attach the picture.

 

[muhammad.usman]

https://obrazki.elektroda.pl/2594780400_1380473142.jpg

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Johnjoe this is the top and side view of device I am designing. Now my question is the middle section impedance should be close to 50 0hm. I am not sure that how can I design tapered CPW bond pads close to 50 ohm so that there are no mismatch reflections.
looking forward to your reply

 

[johnjoe]

Hi muhammad,

sorry for the late reply. Assuming that both connected cpws have 50 Ohm, just keep the taper as short as possible because it is quite hard to analyse the taper analytically. For which frequency?

 

[muhammad.usman]

Hi John thanks for the answer but my confusion is still there . I am again attaching the picture it explains what I am asking


<a title="help CPW.JPG" href="http://obrazki.elektroda.pl/4733060900_1382436448.jpg"><img src="http://obrazki.elektroda.pl/4733060900_1382436448_thumb.jpg" alt="help CPW.JPG" /></a>

 

[johnjoe]

Ok, you use your taper for impedance transformation 50Ohm->40Ohm? Simply simulate just the taper with port impedance 50 Ohm on one side and 40 Ohm at the other side.There is no analytic form.

 

[aniakhan]

hi,
john and mohammad,
can you please help me i understanding this exponential tapering?i was trying for microstrip line to stipline transition as balun 2:1 but it is not working properly for band from20 -40 ghz now i thought of tapering ground plane og m/s line but how to tapper?is thers any rule for exponential tapepirng?that is any formula for tapering sot hat it transform impednace to 50 tio 100??? how to select value of "a" in fromaula w*exp(-a*t)?

 

[muhammad.usman]

Aniakhan look at the kolpfstein taper for microstrip