RFID Antenna complex impedance calculation

John123
Příspěvky: 6
Registrován: čtv 26. říj 2017 16:16:24
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RFID Antenna complex impedance calculation

Příspěvekod John123 » stř 01. lis 2017 14:50:20

Hello,

I am new to antenna and RFID. I recently designed and made a RFID dipole antenna and would like to see the impedance change at certain frequencies.

I have obtained S matrix parameters s2p file using VNA and all four S parameters (including real and imag) can be seen. Since the complex impedance needs to be calculated using the following equation:
Zd=2*Z0*(1-S11^2+S21^2-2S12)/((1-S11)^2-S21^2), where Z0=50 Ohm.
I tried to plot Zd in EXCEL but it couldn`t handle four complex number operations, hence returning errors.
I then tried MATLAB but the results was very odd. I finally asked a friend of mine to plot using Keysight ADS which got the correct results.
From my side, I don`t have Keysight ADS. I would like to plot Zd using either EXCEL or MATLAB.
Anyone knows the correct way or even more convenient way to do the calculation?

Many thanks,





I didn't find the right solution from the internet.
References:
http://www.antenna-theory.com/phpbb2/vi ... php?t=1212

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