measure the CBCPW using CPW probe

In order to measure the CBCPW circuit using CPW probe, should the transition from CPW to CBCPW (conductor-backed CPW) be needed?

As you know, the field distribution of CBCPW is different from that of CPW, especially when the thickness of the substrate is very small. In this case, the impedance of CPW is different from that of CBCPW.

Help is on the way.
http://acronyms.thefreedictionary.com/CPW

Hi FvM,

I cna not find the answer from this website. I donot know why you give me this website.

You can ground the chuck, can't you?

wlcsp

yes, I can ground the side ground plane to the back ground plane by via hole. But I want to know if CPW probe can be used to directly measure CBCPW, without any modifications or transition.

That's not what I meant. You don't need to connect the backside ground plane to the side grounds through via. Make sure your probe's ground reference is the same as the chuck (where you place your wafer) ground reference. Even then, it won't be perfect. Since the side ground planes are connected to ground through small contact area of your probes, while the backside ground plane is completely connected to the grounded chuck.

wlcsp

You mean I can directly measure CBCPW circuits using CPW probes because the backed ground and the side ground of CBCPW are connected by the ground of probe and chuck.

From the viewpoint of circuit, it is right because all the grounds has the same voltage. But from the viewpoint of field distribution, the field of CPW probe is mainly distributed in the two slots of CPW probes, while the field of CBCPW is in the two slots of CBCPW ,and between the center strip and backed-ground for the thin substrate. In this case, the impedance of CBCPW is different from that of CPW.

Do you think I am right?