1 files changed, 55 insertions, 9 deletions
diff --git a/help/en_US/bilinear.xml b/help/en_US/bilinear.xml
index 0361759..e6a2e46 100644
--- a/help/en_US/bilinear.xml
+++ b/help/en_US/bilinear.xml
@@ -17,36 +17,82 @@
 
   <refnamediv>
     <refname>bilinear</refname>
-    <refpurpose>Transform a s-plane filter specification into a z-plane specification</refpurpose>
+    <refpurpose>Transforms a s-plane filter (Analog) into a z-plane filter (Digital) using Bilinear transformation</refpurpose>
   </refnamediv>
 
 
 <refsynopsisdiv>
    <title>Calling Sequence</title>
    <synopsis>
-   [ZB, ZA] = bilinear (SB, SA, T)
-   [ZB, ZA] = bilinear (SZ, SP, SG, T)
-   [ZZ, ZP, ZG] = bilinear (...)
+    [Zb, Za] = bilinear(Sb, Sa, T)
+    [Zb, Zb] = bilinear(Sz, Sp, Sg, T)
+    [Zz, Zp, Zg] = bilinear(...)
    </synopsis>
 </refsynopsisdiv>
 
 <refsection>
+   <title>Parameters</title>
+   <variablelist>
+   <varlistentry><term>Sb:</term>
+      <listitem><para> Numerator coefficient vector in s-domain. </para></listitem></varlistentry>
+   <varlistentry><term>Sa:</term>
+      <listitem><para> Denumerator coefficient vector s-domain.</para></listitem></varlistentry>
+   <varlistentry><term>Sz:</term>
+      <listitem><para> zeros in s-plane.</para></listitem></varlistentry>
+   <varlistentry><term>Sp:</term>
+      <listitem><para> poles in s-plane.</para></listitem></varlistentry>
+   <varlistentry><term>Sg:</term>
+      <listitem><para> gain in s-domain.</para></listitem></varlistentry>
+   <varlistentry><term>T:</term>
+      <listitem><para> Sampling period (double).</para></listitem></varlistentry>
+   <varlistentry><term>Zb:</term>
+      <listitem><para> Numerator coefficient vector in z-domain.</para></listitem></varlistentry>
+   <varlistentry><term>Za:</term>
+      <listitem><para> Denumerator coefficient vector z-domain.</para></listitem></varlistentry>
+   <varlistentry><term>Zz:</term>
+      <listitem><para> zeros in z-plane.</para></listitem></varlistentry>
+   <varlistentry><term>Zp:</term>
+      <listitem><para> poles in z-plane.</para></listitem></varlistentry>
+   <varlistentry><term>Zg:</term>
+      <listitem><para> gain in z-domain.</para></listitem></varlistentry>
+   </variablelist>
+</refsection>
+
+<refsection>
    <title>Description</title>
    <para>
-Transform a s-plane filter specification into a z-plane specification.  Filters can be specified in either zero-pole-gain or transfer function form.  The input form does not have to match the output form.  1/T is the sampling frequency represented in the z plane.
+a filter design can be transformed from the s-plane to the z-plane while maintaining the band edges by means of the bilinear transform. This maps the left hand side of the s-plane into the interior of the unit circle in z-plane. The mapping is highly non-linear, so you must design your filter with band edges in the s-plane positioned at 2/T tan(w*T/2) so that they will be positioned at w after the bilinear transform is complete.
    </para>
    <para>
-Note: this differs from the bilinear function in the signal processing toolbox, which uses 1/T rather than T.
+It does following transformation from s-plane to z-plane
    </para>
+
    <para>
-Theory: Given a piecewise flat filter design, you can transform it from the s-plane to the z-plane while maintaining the band edges by means of the bilinear transform. This maps the left hand side of the s-plane into the interior of the unit circle. The mapping is highly non-linear, so you must design your filter with band edges in the s-plane positioned at 2/T tan(w*T/2) so that they will be positioned at w after the bilinear transform is complete.
-</para>
+    <latex>
+      \begin{eqnarray}
+      s --> \frac{2} {T} \frac {z - 1} {z + 1}
+      \end{eqnarray}
+    </latex>
+   </para>
 </refsection>
 
 <refsection>
    <title>Examples</title>
    <programlisting role="example"><![CDATA[
-[ZB,ZA]=bilinear([1],[2,3],3)
+Sz = [1 2 3]
+Sp = [4 5 6]
+Sg = 1;
+T = 1;
+[Zb,Za] = bilinear (Sz, Sp, Sg, T)
+
    ]]></programlisting>
 </refsection>
+
+<refsection>
+<title>Modified by :</title>
+<simplelist type="vert">
+<member>Sonu Sharma, RGIT Mumbai (fellow at FOSSEE, IIT Bombay)</member>
+    </simplelist>
+</refsection>
+
 </refentry>