How to calibrate semi-rigid cable ?

[chihhao]

semi rigid cable kit

Using network analyzer, how to calibrate the reference plane to the
end of semi-rigid cable ?

How to make the special calibration kit ? or where to buy ?
Thanks a lot.

 

[xxargs]

how to calibrate cable

Using network analyzer, how to calibrate the reference plane to the
end of semi-rigid cable ?

How to make the special calibration kit ? or where to buy ?
Thanks a lot.

hmm..


Easiest way is make self calibration kit on measure length of semi-rigid cable with open end, close end and 50 Ohm loaded end + exact double length of thru cable.

(latest is importent to compensate for semi-ridge cable loss, special if you want measure impedances near few Ohms )

and after this, use same typer of measure semi-ridged cable with exactly same length as above self made calibration kit.

---

if only need lower precision, after calibration with standard calibration kit, connect measure semi-ridge cable, try using 'delay' in polar/smitchart-view to S11/S22-line going to point on real axis infinite Ohm spot in smitchart (open end) or zero Ohm spot (shorted end) and you have referens plane in cable end.


(note: you cannot recieve exactly 0 Ohm or infinite Ohm in smithchart this way depend of uncalibrated and uncalculated loss inside measure semi-ridge cable.
and, if line going outside smitchart (negative impedance), you have shorter line length compare calibration-process or you have amplifier element in your circurit, or worse - wrong calibrate.)

this trick can also use on path inside PCB board (ex. for measure impedance on transistor or port on IC ), ie shorting and adjust delay (with smitchart view) to S11/S22 line going to spot in near zero Ohm and you move referens plane to shorting point. But longer distans move -> lower precision.

(if need higher precisions measure on pcb-board - use three stripped board and make 'open', 'short' and 'load' on intresting point (ex. transistors pad with or without feeding network, if this is invisible on actual frequency...) and use them at calibrate kit.)

---

make good enough (for actual problem) calibration kit, and cables/adapters (and check this compare to controlled calibration kit) is importent know how on measure engineer.

You cannot buy expensive calibration kit to every type of measure problem, - shift connectors or cable length/type and expensive special calibrations kit is useless. You need enough know how to build this it self, depend of type of measure problem.. and check, check, check again....


/xxargs

 

[vfone]

rigid cable

**broken link removed**

 

[chihhao]

how to make semi-rigid cable

If I want to do special calibration kit for semi-rigid cable.
Where can I find example or demonstration photo?
Should I use FR4 board and use microstrip line for short open load ?
Please advise and thanks.