Parallel RLC circuit conversion

[smuel]

Hi,

I need to convert a high frequency inductor model from a parallel RLC circuit (all three elements in parallel) to a series RL in parallel with a capacitor.

I know the resonant frequency will be the same, so for a given inductance the capacitance will be the same, but i'm guessing the resistance will have to change and i have no idea how to do it...

Please help!

Thanks,

Sam

 

[yjkwon57]

I think you can use the Smith chart to get the answer. Just draw on it.

 

[the_edge]

For given inductance I dont think you will get same capacity...

 

[ender84567]

smith chart can be used. you need to calculate the series Q and match it to the paralell Q. This is explained well in the RF book by charles bowick if you can get your hands on it.

 

[lladnar23]

Also this is well explained in Tom Lee's book on RFICs.
First, find the parallel Q of your L||R as Q=Rp/Xp where Rp is the resistance of the RLC parallel circuit and Xp is w*L, the reactance of the L. Then use Rs=Rp/(1+Q^2) to find the equivalent series R. Use Xs=Xp/(1+1/Q^2) to find the equivalent Xs=w*L
Hope it helps.

 

[smuel]

Thanks for the replies. I think i've got it sorted..

I found the admittance of the parallel circuit, then simply found the related impedance Z=1/Y, then as far as i can tell, the real component of this impedance is my series resistance for the series equivalent. What do you think?

Anyway, we stuck it into the agilent simulator, and it gave pretty damn good results, so i must have done something right!

Thanks again for the help.

Sam