[TowerTalk] S21 to Rp & Cp - Equivalent Circuit
jimlux at earthlink.net
Fri Jan 12 11:16:58 EST 2018
On 1/12/18 7:57 AM, Steve Hunt wrote:
> Yes!!!! - S11 Magnitude and Phase are quite different from S21 Magnitude
> and Phase.
> If you are interested, here's how I derive the choke's complex impedance
> from S21 Magnitude and Phase:
The conversion of Mag/Phase to complex values is the same, but the
conversion of the measurement to Z is different...
in the 1 port measurement, the unknown is in series with the 50 ohm
impedance of the source, so you're looking at the ratio of the
voltage/current across the Z compared to the voltage/current across the
series combination (with some math to turn it into gamma/S11)
In the 2 port measurement, the unknown is between the ports, so you're
looking at the voltage/current across the port 2 load, compared with the
voltage/current at the port 1 source (with some math to turn it into S21)
Steve's website has the equations.
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