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VNA measurement

VNA measurement

VNA measurement

Hi everyone,

I need your help in something,
I am designing an RFID system using NXP chip MFRC522, in order to get the antenna series equivalent circuit,
I have to make some measurement using a vector network analyzer.
the VNA i have access to now is R&S 10Mhz to 67Ghz,

the operating frequency of the RFID is 13.56Mhz,
the needed measurements according to the NXP measurement application note AN11535 see attachments, is:
1- S11 - Smith Z - Start frequency: 1Mhz - Stop frequency: 5Mhz ( to get real and imaginary part of Zant)
2- S11 - Start frequency: 1Mhz - Stop frequency : 100Mhz (to get self resonance frequency & and real part of Z ant at Self resonant frequency)

Will it be ok if i measure 1 at 13.56 Mhz,
Please your advise,

Thanks in advance,

RE: VNA measurement

"Mhz" "Ghz" - the 'H' in Hz should always be a capital H, like MHz and GHz.

Setting the frequency range takes mere seconds. So it's common (for your example) to start with 1-100 MHz for a look-see, then zoon in to a narrow range around 13.56 MHz to see if there's anything interesting, then double check what frequency range data being requested and capture those exact frequency ranges. All this should take maybe 10 minutes.

It's not clear why one would be interested in the response 1-5 MHz if the operating frequency range is 13.56 MHz. The final system should not be emitting significant energy between 1-5 MHz, so nobody should care about 1-5 MHz. If the data sheet has an explanation, I've not read it to that level of detail.

If you're inexperienced making these measurements, there's plenty that can go wrong. So if the data doesn't make sense, then suspect you measurement (connection) techniques early in the troubleshooting process. The frequency range (HF) isn't that tricky, but still...

RE: VNA measurement

The extra frequency range is probably related to interference calculations towards other systems 1 MHz his a.m. radio and the spec might want to show it roll off below band

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