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VNA calibration and measure Help

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TerryADS

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Hi friends,
I want to measure the impedence of antenna. I did the VNA calibration of semi-rigid cable(30KHz~6GHz),and then directly measure the impedence of antenna,i get 128+j*60(VNA calibration port external still set:eek:n),but when i set the center frequncy (1.921GHz)and span(1GHz),i find i get another impedance,as 23+j*60.
My question is when i finish semi-rigid cable calibration,whether i can set the port external set off,and whether i can re-set the center frequecy and span?Anyone share me your experience what is wrong procedure after calibration and before measure?
Thanks
 

Newer VNAs such as Agilent PNA have interpolation so you can set a narrower sweep which is a subset of your calibration sweep. If you have an older VNA then maybe that's the problem. You must calibrate and measure with same sweep settings. Once you change the sweep you loose the correction. If you have an HP/Agilent analyzer there will be a "*C" to the left of the graticule to tell you when correction is enabled. Even with the PNA you may have to tell it to use interpolation.
 

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    TerryADS

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Thanks,madengr.i use 8753ES VNA.Whether the calibration always set on during i measure ?Another hand,how to use interpolation to tell VNA?
Thanks a lot,
 

It looks like the 8753ES does have interpolated correction. You'll have to figure out how to turn it on though.

**broken link removed**
 

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    TerryADS

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