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Pi filter for impedance matching


walid
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Hellow,
I build the following pi filter to match 100 ohm source to 1000 ohm load, I did the calculations based on RF Circuit Design Book
423283768.jpg
As u can see at the center freq fc = 30MHz & Q=15 I had 3.771dB, I was surprised by where this value? this is amplification!!!!

The second question is: If i want to match 1000 ohm source to 100 ohm load, Simply replace the capacitors, one must place the other, when i did so and simulate i had the following:
[img width=680 height=478]
Look!! -9.8dB at the center freq.
can you please comment, how to match big source to small load without that bad attenuation
thanks alot

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This is a "second order" circuit. You took a bode plot over a frequency range. Things are going to change over frequency. Have you solved the differential equation for this circuit to find the poles and zeros? It's also what is called a "passive circuit"... so, unless you hit a resonant frequency (as AG pointed out) in your sweep, this thing can only attenuate.

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