microstrip vs cpw
To vfone,
I agree with importance of high volume production and this is why I told about importance of having precise, fast and easy to use tool to design CPW. For example, when I was a member of cell phone design team in one of Motorola design centers about 10 years ago, we try to use CPW. For these times we had only one tool and this tool was bulky and not accurate, so we drop CPW. Then in another company I met the same problem with CPW. After this I spent significant amount of time to study the problem and design the worksheet. Now we do CPW design quickly and easy and have no manufacturing problems. I use it not only for UWB due to consulting other companies. By the way, UWB products may reach several millions volume before the end of the year. We have a products and market needs them.
To madengr,
I use both of them. The choice depends on particular application and even on the same board may be different situation. May major point is to play with design variables and get result which provides stable manufacturing and required RF performance. I can easily do isolation up to 90 dB. Higher numbers are possible, but may be not stable and will require additional measures. If you have 6 dB isolation with CPW something is definitely wrong. I am going to publish technical paper about isolation optimization for PCB layout and there will be detailed recommendations on CPW too.