Published by Eric Bogatin on 20 Jan 2013
Characterize a high-density, controlled impedance test interface
My latest feature article posted on the Test and Measurement World web site and the EDN Online web site, offers an example of how to characterize a high density interface.
In this project, I worked with Gordon Vinther at Ardent Concepts. They have a pretty cool interface, the Omniprobe-R, that enables contacting an array of micro coax cables to any footprint, like a BGA.
This can be used to either test an active BGA in a load board test application or when it is attached to a product board.
Their interposer technology can also interface between an array of coax cables and a high density array of pads on a circuit board. This sort of technology is essential when testing motherboards with high speed serial links.
In our paper, we looked at the high speed performance of two cable interfaces connected together with their compliant interposer. The 4-port measurements were done to 20 GHz using a Teledyne LeCroy SPARQ. We walk through these measurements and show how to interpret the results and display them in a way to get immediately useful information.
The punch line is that the Ardent interposer is pretty darn transparent. Check out the feature article for the details.
If you want to learn more about interpreting S-parameter measurements, you’ll want to check out the next S-Parameters for SI 2-day class we have coming up in late Feb 2013. Hope to see you there!



Colin Warwick, Agilent, talking about their new 3D display. In addition to looking like a couple of really cool SI Dudes, we were able to see the results from a full wave EM field solver of current flow in a via field. With the LCD shutter glasses, and interleaved left-right screen being displayed on the monitor, it really did look like the vias were standing out in front of the screen. This 3D capability is embedded in Momentum and EMPro., able to show currents, fields and voltages.
Tightly coupled into the Agilent’s ADS simulation environment are Momentum, which does 2.5 D full wave simulations and EMPro which does 3D full wave simulation. While both of these tools can show 3D perspectives of the static or dynamic, electric or magnetic fields or currents in and around conductors, the simulations seem to come alive when viewed in true 3D.