# LC bandstop theory

Discussion in 'Radio and Communications' started by turkeybuzzard, Mar 23, 2011.

1. ### turkeybuzzard Thread Starter New Member

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Hi -- I'm a novice and am trying to work out a theoretical problem. I put this question here because I figure you guys are the LC filter experts:

1. If I have a ideal AC source (at frequency f) connected to a series consisting of R,F,R,F,R (where Rs are equal resistance and Fs are LC parallel band stop filters tuned to frequency f) then what's the current across the resistors and what's the oscillating current inside each F. Is there no voltage drop across the Rs at the resonant frequency? Are the resonance currents inside the two Fs equal?

Here's the circuit:

http://dl.dropbox.com/u/7372632/Circuit.pdf

Thanks for your thoughts,
Dave

2. ### t_n_k AAC Fanatic!

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If these are all ideal elements one would expect zero source current at resonance. Each parallel stop filter would see half the source voltage with two such branches. If there were three branches each would support 1/3 of the source voltage. So each parallel branch element would have a current proportional to the source voltage. The currents in the L&C components would be of equal magnitude but exactly out of phase at resonance.

3. ### turkeybuzzard Thread Starter New Member

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T_N_K thanks for the clear response ... that makes sense.

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