SM 5 BSZ - Intermodulation in receivers.
(Sept 17 2003)
A function block of a radio receiver which is well characterized by
Y1(t+d1) = k11X1(t)+ k12{X1(t)}2 + k13{X1(t)}3 + ......... (1)

is connected in series with another function block which is well characterized by:
Y2(t+d2) = k21X2(t)+ k22{X2(t)}2 + k23{X2(t)}3 + ......... (2)

Let us find out what Y2 becomes when expressed in powers of X1 by putting:
X2(t)=Y1(t+d1)

Y2(t+d1+d2) = k21* { k11*X1(t)+ k12*{X1(t)}2 + k13*{X1(t)}3 + }
+ k22 { k11*X1(t)+ k12*{X1(t)}2 + k13*{X1(t)}3 + } 2
+ k23 { k11*X1(t)+ k12*{X1(t)}2 + k13*{X1(t)}3 + } 3 + ......... (3)

We pick all terms up to third order:
Y2(t+d1+d2)=k21*k11*X1(t)
+[k21*k12+k22*{k11}2] *{X1(t)}2
+[k21*k13+2*k22*k11*k12 +k23*{k11}3] *{X1(t)}3

It is obvious that two series connected units that are both well described by a polynomial expansion will also be described by a new polynomial expansion.

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