Lecture 9 : Graphical Approach for Transmission Analysis
Constant Resistance Circles
The constant resistance circles have their centres at ( , 0) and radii (). Figure below shows the
constant resistance circles for different values of ranging between 0 and .
We can note following things about the constant resistance circles.
(a)
The circles always have centres on the real -axis ( -axis).
(b)
All circles pass through the point (1,0) in the complex plane.
(c)
For , the centerof the circle lies at the origin of the plane and it shifts to the right as increases.
(d)
As r increases the radius of the circle goes on reducing and for the radius approaches zero, i.e., the circle
reduces to a point.
(e)
The outermost circle with center (0,0) and radius unity, corresponds to or in other words represents
purely reactive
impedances.
(f)
The right most point on the unity circle, represents as well as .
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