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DC coupled 2.7 GHz Active Probe Project - Now Available!
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JohnG:
FC resistors may be overkill, but they are nice and accurate. If you get them, you should look at the datasheet and consider the difference between the "wrap-around" termination and the "flip-chip" termination, shown in the figure labeled "Internal Impedance." (Good god, I hate this graphic designer trend of eliminating section and figure numbers. I curse them...). It shows a few % increase in impedance at 2 GHz, and a lot more at 6 GHz, for the "wrap-around" versus the "flip-chip".

https://www.vishay.com/docs/60162/fchpseries.pdf

If you use a more cost-effective thin film resistor, you can get the same benefit by mounting the resistor upside-down, i.e. with the resistive element adjacent to the PCB. It can save a few hundred pH. If you are measuring your boards and feel so inclined, you can measure this difference pretty easily at a few GHz.

Hope you find this useful.

John
tszaboo:

--- Quote from: nctnico on August 18, 2023, 12:30:18 am ---
--- Quote from: tszaboo on August 17, 2023, 04:46:52 pm ---
--- Quote from: joeqsmith on August 17, 2023, 01:17:04 pm ---Why have components mounted on the thru, open and short?  For the load, why wouldn't you use a standard?  Are you concerned the length of the load will made a big difference?

--- End quote ---
I don't intend to mount those components, but I placed the ~3mm long transmission line and the component footprint anyway.
I guess I could use an FC0402 50Ohm as the load. Normally the length shouldn't make a difference, but from what I've seen, the closer you can make the calibration look like the real world condition, the better.
Plus, I only have a female cal kit for for SMA (at work).
But you know what, it's an interesting question as well. I'll calibrate it without the components on it and mount some 0402s and see if it makes a difference.

--- End quote ---
With an OSL you will be calibrating at the connector. So whatever is different (like the trace not having a perfect 50 Ohm impedance and FR4 loss factor) for the real measurement will show up. Then again, I'm missing the DUT position for a reflection based measurement so how useful are the OSL parts on your board anyway?

But it does make sense to calibrate the board from an OSL calibration in order to determine whether the error is as expected c.q. up to what frequency your board is useable. But the through measurement will be the most useful anyway because the error is low over a much wider frequency range.

--- End quote ---
I'm planning OSLT, the measurement is not a reflection based it's through.
https://coppermountaintech.com/measurement-of-electronic-component-impedance-using-a-vector-network-analyzer/

According to this article, measuring 100 Ohm and above, I should use the through method, and around 50 Ohm, I can use the reflection
based on a S11 measurement.

--- Quote from: joeqsmith on August 18, 2023, 12:48:12 am ---Board would be taken out and reference plane would be at the end of the transmission line.   I assumed they were making multiple boards and populated the test parts on the second one.   :-//

--- End quote ---
Exactly.
I'm going to open another thread for this, so we don't pollute lasmux's excellent design with off topic stuff.
https://www.eevblog.com/forum/rf-microwave/measuring-passive-parts-with-vna/new/#new
RFKev:

--- Quote from: joeqsmith on August 16, 2023, 05:05:00 am ---S11 & S21 for the blade probe using the PNA.  My homemade PCB waveguides are going to be useless.    Starts out at 500 ohms as and drops off rather quickly reaching 100 ohms at 6 GHz.   Mag isn't very stable  (when holding all the parts in my hands, moving them around...).  Then there is de-embedding the interconnect.   Consider it all just a gross measurement to give us some idea how it behaves.

--- End quote ---
What was the measurement setup and METAS VNA Data Explorer configuration to get the probe impedance with frequency?
joeqsmith:

--- Quote from: RFKev on September 01, 2023, 08:22:54 am ---
--- Quote from: joeqsmith on August 16, 2023, 05:05:00 am ---S11 & S21 for the blade probe using the PNA.  My homemade PCB waveguides are going to be useless.    Starts out at 500 ohms as and drops off rather quickly reaching 100 ohms at 6 GHz.   Mag isn't very stable  (when holding all the parts in my hands, moving them around...).  Then there is de-embedding the interconnect.   Consider it all just a gross measurement to give us some idea how it behaves.

--- End quote ---
What was the measurement setup and METAS VNA Data Explorer configuration to get the probe impedance with frequency?

--- End quote ---
I showed the screen shot of the METAS setup and used S11 to measure the impedance.  Guessing that is not what you are asking.  Maybe consider posting a more detailed question. 
RFKev:

--- Quote from: joeqsmith on September 01, 2023, 02:10:36 pm ---
--- Quote from: RFKev on September 01, 2023, 08:22:54 am ---
--- Quote from: joeqsmith on August 16, 2023, 05:05:00 am ---S11 & S21 for the blade probe using the PNA.  My homemade PCB waveguides are going to be useless.    Starts out at 500 ohms as and drops off rather quickly reaching 100 ohms at 6 GHz.   Mag isn't very stable  (when holding all the parts in my hands, moving them around...).  Then there is de-embedding the interconnect.   Consider it all just a gross measurement to give us some idea how it behaves.

--- End quote ---
What was the measurement setup and METAS VNA Data Explorer configuration to get the probe impedance with frequency?

--- End quote ---
I showed the screen shot of the METAS setup and used S11 to measure the impedance.  Guessing that is not what you are asking.  Maybe consider posting a more detailed question.

--- End quote ---
I can see the settings along the top of the METAS screenshot. Was there anything configured in the "Setup" dropdown?  My main question is how was the probe interfacing with the VNA.  Did you touch the probe on the port 1 connector, or probe a transmission line?  If you probed a line connected to port 1, was it terminated with a 50ohm load?
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