Electronics > RF, Microwave, Ham Radio

Shunt capacitance of 1206 SMD resistors; Jeroen Belleman - December 2010

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Some time ago I had come across an paper written by Jeroen Belleman where he was studying the parasitic shunt capacitance of some 1206 resistors.  The original paper may be found here:


He notes:
--- Quote ---At the low-frequency end, it also curves up, for reasons I do not currently understand. If I insert a few dB of attenuation at both ends of my test jig, the effect goes away.
--- End quote ---

I had been wanting to repeat this test to see if I could replicate that curve up.  Shown are my 1206 test resistors plus an added 50 ohm part.   Sadly my PNA can't run below 300kHz.   What I have done is used my HP3589A to collect the data below 300kHz and then stitched the two files together.   Their setup starts to curve up below 100kHz so I thought I would collect data down to 3kHz. 

The source was set to 0dB and the RBW to 1.2kHz (thought about lowering it and using the log sweeps).   I have no additional attenuators inserted and see no signs of this upwards curve.   

Change scale of my graph to allow easier viewing.

I never realized when the HP3589A starts a sweep, it causes a small disturbance in the data.
Operator error..  ::)   

Shown with nothing inserted in the test jig (open) to look at the floor with a RBW of 150Hz.  I would like to see about 10dB of headroom but it should be fine. 

It will be interesting to see if the METAS software can hand this much data and with it being stitched together.   

Note that I had started out with a cable that was loaded up with Ferrite where it it shown without.   As expected, I saw no difference and plan to run it as shown (without the Ferrites).

Shown is the combined data, sweeping from 900Hz to 6GHz with roughly 27,000 data points segmented quasi log sweep.    A fairly decent test for both programs.   

All the Ferrite was removed when collecting this data.  Once again, there are no signs that odd amplitude change at the < 100kHz.

I converted the original data to Touchstone format and overlaid it with the data I collected.   

Beats me; does seem like an instrument error or something.  Have you contacted Jeroen?  He's... well at CERN still AFAIK, and also I think checks sci.electronics.design sometimes.



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