Network functions

Discussion in 'Homework Help' started by smock, Jan 29, 2011.

  1. smock

    Thread Starter New Member

    Jan 29, 2011

    While practicing problems in preparation for my midterm next week, I came across the following question.

    The network shown below (please see attachment) has poles at -1.5+((√111)/2) and -1.5-((√111)/2), and a zero at -3.

    In addition, it is known that the impedance at zero frequency (s=0 or direct current) is 1 ohm, that is Z(0) = 1. Determine the values of R, L, C in the network.

    I was easily able to determine the value of R by just getting Zeq and setting s = 0 to 1.
    However, I don't know how to find the values of L and C. any help that can be rendered is much appreciated.

  2. Georacer


    Nov 25, 2009
    I don't have much experience with RLC networks, but the theory is this:

    You construct the transfer function of the circuit and you convert it to its Laplace transformation. I suggest viewing the R,L and C components as "blocks" that are to be merged serially or parallely. This TF is a function of R, L and C.

    You substitute R with the value you found. Afterwards, you calculate the poles and zeroes from the TF and you equate them with the ones given to get a system of 2 equations with 2 unknowns.
    Last edited: Jan 29, 2011