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Hi,
I have some problems in understanding how to calculate the input (is it input?) impedance of a small circuit. (I have attached the equiv. circuit with values )
The circuit is a small loop antenna that resonates at 13.56 MHz and is tuned to 50 ohm.
From the source point of view: a capacitor in series (Cmatch = 11.74 pF) and then 3 elements in paralell; a capacitor (Cres = 96.76 pF), resistance (Rp = 20050 ohm) and an inductance (L=1.27 microhenry)
The impedance seen from the source is 50 ohm, however I don´t understand how to reach that answer,as calculating with complex impedances should be straight forward:
[tex]Z = \frac{1}{\frac{1}{Rp}+\frac{1}{j\omega L}+j\omega Cr} +\frac{1}{j\omega Cm}[/tex]
Solving this equation with matlab takes me faaaar away from 50 ohm ....
Am I doing something fundamentally wrong???
(The circuit and values are from a Texas Instruments Paper, should give impedance = 50 ohm.....???)
any help is appreciated
eirik
I have some problems in understanding how to calculate the input (is it input?) impedance of a small circuit. (I have attached the equiv. circuit with values )
The circuit is a small loop antenna that resonates at 13.56 MHz and is tuned to 50 ohm.
From the source point of view: a capacitor in series (Cmatch = 11.74 pF) and then 3 elements in paralell; a capacitor (Cres = 96.76 pF), resistance (Rp = 20050 ohm) and an inductance (L=1.27 microhenry)
The impedance seen from the source is 50 ohm, however I don´t understand how to reach that answer,as calculating with complex impedances should be straight forward:
[tex]Z = \frac{1}{\frac{1}{Rp}+\frac{1}{j\omega L}+j\omega Cr} +\frac{1}{j\omega Cm}[/tex]
Solving this equation with matlab takes me faaaar away from 50 ohm ....
Am I doing something fundamentally wrong???
(The circuit and values are from a Texas Instruments Paper, should give impedance = 50 ohm.....???)
any help is appreciated
eirik
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