PIN diode input impedance

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Antenna (^.^)

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Hi everyone,

I want to make a spst PIN diode rf switch.
This needs AC coupling (DC Blocking) capacitors, bypass capacitors and chokes...
For determining the value of the coupling capacitors, the input impedance is required.
How to find the input impedance?

 

Impedance , of the coupling capacitance, Xc is simply Xc=1/(2πfC) and the voltage loss approaches the load impedance , Zo with the ratio Zo/(Zc+Zo)

Since power is V²/Zo, It is easy to derive the Isolation and insertion loss in dB

With Zo terminated at both ends (2Z0), Insertion loss, IL of the series diode, Rs.... becomes

Insertion =20 log [1+ (Rs/2Zo)] ( Pin bias ON controls Rs )


Isolation = 10 log [ 1+ Xc/(2Zo) ]² ( C controls isolation )

https://www.google.com/url?sa=t&rct...3mlr_9Rtpx3bTNtRQ&sig2=arAi2MvPWvlYLsUpmYFn6Q
 

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