How to apply reciprocity theorem to h parameters?
Reciprocity theorem says that ratio of excitation to result must remain same if they are interchanged


No, the reciprocity theorem does not say that. That is just the definition of reciprocity (actually, not well stated). The reciprocity theorem states, instead, that a certain specific class of networks, that of networks composed of resistors, inductors, capacitors, and transformers, is reciprocal.

First, let me start with a better definition of reciprocal network [1]:


  A reciprocal network is one in which, for any pair of excitation and response points, here labeled 1 and 2, \$I_1 = I_2\$ if \$V_1 = V_2\$.


Notice that when you set a current excitation you should look at the voltage response and viceversa.

Consider now the hybrid representation of a two-port network,

$$ \begin{pmatrix} V_1 \\ I_2 \end{pmatrix} = \begin{pmatrix} h_{11} &amp; h_{12} \\ h_{21} &amp; h_{22} \end{pmatrix} \begin{pmatrix} I_1 \\ V_2 \end{pmatrix}.$$

Set, e.g, a current excitation at port 1, \$I_1 = I\$, and look at the open circuit voltage response at port 2, that is, find \$V_2\$ when \$I_1 = I\$ and \$I_2 = 0\$. Plugging these conditions into the matrix equation above, yields

$$ \begin{pmatrix} V_1 \\ 0 \end{pmatrix} = \begin{pmatrix} h_{11} &amp; h_{12} \\ h_{21} &amp; h_{22} \end{pmatrix} \begin{pmatrix} I \\ V_2 \end{pmatrix},$$

from which we obtain 

$$V_2 = -\frac{h_{21}}{h_{22}}I.$$

Now exchange the position of the excitation and the response: set \$I_2 = I\$, \$I_1 = 0\$ and find \$V_1\$. From

$$ \begin{pmatrix} V_1 \\ I \end{pmatrix} = \begin{pmatrix} h_{11} &amp; h_{12} \\ h_{21} &amp; h_{22} \end{pmatrix} \begin{pmatrix} 0 \\ V_2 \end{pmatrix}$$

we get

$$V_1 = \frac{h_{12}}{h_{22}}I.$$

The reciprocity condition requires the two responses to be equal, \$V_1 = V_2\$, that is,

$$\frac{h_{12}}{h_{22}}I = -\frac{h_{21}}{h_{22}}I$$

from which \$h_{12} = -h_{21}\$.

[1] N. Balabanian, T. A. Bickart, Electrical network theory, John Wiley &amp; Sons, Inc., 1969.