How to make TDR Probe

Hi everyone,

I hope I post this is the right place. I would like to know any ways to make probe. This probe will use to message impedance on the PCB (many layer). It will be connect to Tektronix 8200 TDR equipment. I used the polar probe, however, the distance between signal and ground is not the same distance as the probe. As a result, I believe I need to make my own probe. I would like to know what is the best way to make this 50 ohm and used with the TDR machine.

By the way, if the distance between two via is too far away, how would you guy suggest to message it impedance. My approach is it makes a probe. Any idea would be appreciate.


Thanks

Here is a TDR paper which might give you the answer:

http://www.ipc.org/4.0_Knowledge/4.1...5_2-5-5-11.pdf

I don't understand the exact problem. Assuming you are performing a single ended measurement, the probe should connect the 50 ohm cable without discontinuities to the test structure. The IPC pad layout has been designed to meet this requirement. A different layout possibly involves more discontinuity, with sufficient length of the test structure, the measuremet should still work, in other words, you can distinguish between probe connection and test structure in the TDR waveform.

You should explain your via problem more clearly.

The problem is not the SMA 50 ohm cable. The problem is the gap on the probe pin. The distance between probe pin that I have is not the same as the distance on the PCB. As a result. I need to make my own 50 ohm probe (single and differential). Please explain more. I don't think making a probe is a good idea for this case but what are the way to make a measurement if the sign and ground are not within distance of the probe pin.

thanks