LMH3401EVM: How to properly test the LMH3401EVM for the best performance as in the datasheet？

user4913378

Part Number: LMH3401EVM
Other Parts Discussed in Thread: THS4541, LMH3401

https://e2e.ti.com/support/amplifiers/f/14/p/873171/3245435#3245435

As the question shown above, I test the amplifier with the shorter cable above 150mm, but the ripples still appear.

I connect the keysight for technical support to make sure there no problem in the VNA and calibration kit. The technical support think the small ripples in S21 is because of the poor matching between LMH3401EVM and VNA(S11 close to 0dB). There may be a test fixture between VNA and LMH3401EVM for good matching in the test of datasheet. The test equipment may be a test fixture in the picture.

Can anyone describe the correct test method in detail? Which model of VNA is used for testing?

over 5 years ago

0 Hasan Babiker31 over 5 years ago

TI__Genius 15605 points

Hello,

As shown in the figure you've attached, the load is meant to be matched with two 50-ohm single-ended inputs or one 100-ohm differential load.

Best,

Hasan Babiker

0 user4913378 over 5 years ago in reply to Hasan Babiker31

Prodigy 70 points

Hello,

I want to know if getting test data from datasheet use a test fixture between VNA and LMH3401EVM for better VSWR in the test of LMH3401EVM, because my S11 is larger than data from datasheet.

It may also be that my network analyzer is not good enough. Do you know what kind of network analyzer and calibration kit the uses for testing in datasheet？

Thank you,

Jiang

0 Hasan Babiker31 over 5 years ago in reply to user4913378

TI__Genius 15605 points

Hello Jiang,

This data was measured using a ZVA-24 VNA. The low frequency data was extrapolated by also correlating with a E5071B network analyzer.

Best,

Hasan Babiker

0 kai klaas69 over 5 years ago in reply to user4913378

Guru 140200 points

Hi Jiang,

why not just trusting the datasheet? The guys from TI know very well what they are doing :-)

Kai

0 Michael Steffes over 5 years ago in reply to Hasan Babiker31

Guru 48395 points

I am not sure what that box is Hasan,

I believe these characteristic curves were taken with a 4port network analyzer with an automated calibration box. That calibration (for the cabling up to the EVM board) is critical to good results. Not sure the part number but probably an Agilent (or Keysight - or whatever these days) or Rhode and Shwarz box.

0 Michael Steffes over 5 years ago in reply to Michael Steffes

Guru 48395 points

For a bit slower FDA's, there is some discussion in the THS4541 datasheet for I/O interfaces we used to use a 2 port network analyzer - basically baluns.

0 user4913378 over 5 years ago in reply to kai klaas69

Prodigy 70 points

Hi Kai,

I want to know what is wrong with my test method, causing my LMH3401 to peform pooly.

Thank you,

Jiang

0 user4913378 over 5 years ago in reply to Michael Steffes

Prodigy 70 points

Hi Michael,

My VNA is 2 port with mechanical calibration kits. Maybe I should get a 4 port VNA to test it.

Thank you,

Jiang

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LMH3401EVM: How to properly test the LMH3401EVM for the best performance as in the datasheet？