Thanks a lot for the information your provided.
Actually, I only have a couple of DUTs to measure. I think it may be very difficult to solder a short section of small semi-rigid coax to the board for measurement, since our DUTs are so miniature that it may not have enough space for soldering. The distance between two adjacent ports is about 36mil=0.9mm on the same side (as indicated in the picture above), and the distance between adjacent port is about 164mil=4.2mm on two adjacent sides, which is the same as the DUT's length.
For the test fixture in your reply, it might be not proper for our measurement for the same reason that our DUT is too miniature. I checked the specifications of this test fixture. It requires that minimum length of DUT is 9mm and minimum width of DUT is 2.5mm.
What do you think of this? Or could you please offer some suggestions? Thank you so much!
If you only have a couple DUTs to measure, then you can probably solder a short section of small semi-rigid coax to the board that has an SMA on the other end. I've had great success with that up into the 6 GHz region (could probably go higher, butI've never needed to).
For measuring a large number of DUTs, a fixture will be necessary. I've never used one myself, but I see that a company called Gigalane has a productio quality fixture for measuring your type of PCB.http://www.gigalane.com/index.html?mode=02_01_01_01&pduid=93