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

1. Jan 7, 2012

### sns

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

Find the h parameters of the following systems:-

---L---------C--
:
:
R
:
:
----------------​

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?

Thanks.

Last edited: Jan 7, 2012
2. Jan 7, 2012

### Su3liminal

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

3. Jan 7, 2012

### sns

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?

4. Jan 11, 2012

### rude man

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.