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Homework Help: Finding h parameters when capacitors and inductors involved with resistors

  1. Jan 7, 2012 #1


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    1. The problem statement, all variables and given/known data

    Find the h parameters of the following systems:-


    L= j5 ohm
    C=-j5 ohm
    R=1 ohm

    2. Relevant equations

    The above questions has to be solved manually as well as simulated (Matlab-simulink).
    If anybody can please give a detailed solution explaining all the steps used I will be very grateful.
    I only need the manual solution then obviously I can simulate the circuit. Also please explain the significance of giving L and C in ohms without specifying the frequency of supply to be used. Is this circuit only for an a.c. source? Can h parameters vary with time?

    Last edited: Jan 7, 2012
  2. jcsd
  3. Jan 7, 2012 #2
    Well, first write the h-parameters equations:

    V1 = h11*I1 + h12*V2
    I2 = h12*I1 + h22*V2

    And to find the parameters follow the formal procedure:

    First, by shorting V2 (that is, making V2 = 0), you can find:
    h11 = V1/I1
    h12 = I2/I1

    Then, by opening the first port (that is, making I1 = 0), you can find:
    h12 = V1/V2
    h22 = I2/V2

    And then after writing the equations, things gonna be clear to you. Of course, I would like to help and solve all the project for you, but this isn't how it supposed to be. You have to work out the rest by yourself :biggrin:
  4. Jan 7, 2012 #3


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    Well I had done the same and when I do it I start getting the same problems all over again.. Firstly please clear my concepts:
    Can h parameters vary with time? Because if we supply voltage V1 ie sinusoidal then currents flowing will not be constant.. thus ratios wouldn't be constant.. Am I correct? Thus will h-parameter be an equation eh?
    But if supply d.c. voltage and wait for circuit to be stable... then capacitor ultimately blocks current and inductor just passes current through.. then definitely h-parameters are constant. It'll just be a resistor circuit finally? Is this evaluation correct?

    Please help..
  5. Jan 11, 2012 #4

    rude man

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    Homework Helper
    Gold Member

    1. Your h parameters are not time-variant. They are defined solely by your component values, which are presumably constant. Almost by definition, 2-ports are restricted to ac signals.

    2. I'm not going to try to solve the h parameter equations as suggested by su3liminal. That's because they may lead to singularities (& I'm too lazy to find out). In which case what you need to do is rewrite the 2-port equations in terms of a different parameter set. Try the z and the y parameters. Then get a table that gives you the h parameters given the z or y parameters.
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