Question about RF trace width on a PCB

Dear all,

I have question about the RF trace width on the PCB. I hope anyone could give me a help. Thanks first :)

For example, I have calculated the width of the trace based on the equation. I found that the width = 1mm, then the trace is 50ohms impedance. However, there are impossible to make the RF trace as same width as the whole length becaues the trace need to connect some SMD components and the chip pins. As you know this pin are very small in size. So, I need to be narrow the trace to connect it. Then, how could I know the effect of the narrow part? What is the varation from 50ohms?

Does any rule of thumb to route this RF trace width on the PCB? Is I don't need to care the width of the trace when the length of the trace is shorter than (lamda/20)?

I hope anyone could help me.

Thanks

wccheng

So you gonna use that with you murata switch? the step impedence will act as a low pass filter. you can use a CAD tool to see the effect by connecting two diferrent width transmission lines and simulating it.

Dear,

Any simulator could simulate it? ADS or HFSS?

thanks
wccheng

ADS would do the job. There are two ways in ADS: using the empirical model (fast) orf momentun. HFSS is a fullwave simulator. you will get a better result but it will take longer time to simulate.

ads has a particular tool ""to calculate the width and electrical degree about the certain impedance microstrip , use it