2-Port Shunt-Through Impedance

PDN Measurement for Power Integrity

The 2-Port Shunt-Through impedance measurement is the Gold Standard for PDN testing and Power Integrity assurance. Power Integrity assessment and optimization is an essential element in today’s designs. It is critical that your power supplies, printed circuit boards, and decoupling be properly designed in order to achieve flat impedance goals. Commonly applied “Rules-of-thumb” generally don’t work well in high speed circuits or other sensitive applications. Design assurance, optimization and troubleshooting all require accurate low impedance measurements. Whether you are modeling components, testing power supply output impedance, assessing target impedance, or looking to manage PDN resonances, Picotest has a 2-port testing solution for you. Look below for testing solutions and product information.

2-Port Solution

Vector Network Analyzer

Do you have a vector network analyzer?

Ground Loop Isolator

What ground loop isolator is required?

Connections & Test Standards

What accessories are available?

Power Integrity Book

By Steve Sandler


Test Setup for 2-Port Shunt-Through Measurement

Description: Calibrating the 2-Port Shunt-Through Measurement The 2-port measurement requires a Thru calibration. Setup ALL the cabling to the DUT and use a shorting barrel where the component or circuit connections will be made. Note, DC Blocks may be necessary to connect in-line for some powered circuit tests so the 50ohm VNA ports do not load the measurement. If Blocks are necessary they, and all other cabling, should be included in the calibration. Place the J2102A/J2113A on the Channel 2 side of the measurement. Perform a Thru Calibration. Remove the shorting barrel. You are now ready to connect to the DUT and perform the measurement.


Calibration Sidebar Note:

Q. What impedance should show on the VNA when the shorting barrel is connected?

A. If after you calibrate the Shunt-Through measurement you run the VNA and observe the impedance magnitude you will see a high impedance (> 100k ohms). Why is that given you used a “short” to connect the cables?

Look again closely at the diagram above. The shorting barrel connects the center conductors all together and the grounds all together. It does not connect the signal to ground. Therefore, in the shunt configuration the DUT is essentially open and that is why a high impedance is shown.

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