te lines can be made to behave like In mathematical terms, we have infinitely long lines if they are terminated with the characteristic impedance of the line. reflected power incident power 2.2.10.2 Matched and unmatched lines This simple equation is very useful for the following reasons. Its value is independent of incident power because if A transmission line which is terminated by its own you double incident power, reflected power will also characteristic impedance, Zo, is said to be matched or double. 13 If you like, you can say that I is normalised properly terminated. A line which is terminated in any to its incident power. impedance other than Z is said to be unmatched or It gives you a measure of the hardness (impedance) improperly terminated. To prevent reflections it is usual of the wall to incident power. For example if the for a transmission line to be properly terminated and SO it wall is made of stone, it is likely that very little This argument is similar to the case mentioned in Section 2.2.2.2 where it was shown that if our finite tunnel was terminated with material with the same properties as an infinitely long tunnel which absorbed all the incident energy then it would also behave like an infinitely long tunnel. You see this reflection effect as multiple images on your television screen when the TV input signal is not properly terminated by the TV system. TV engineers call this effect 'ghosting'. 13 This of course assumes that the hardness of your wall is independent of the incident power impinging on it. Transmission lines CHAPTER 2.2 incident power will be absorbed and most of the Incident wave incident power will be returned to you as reflected power. You will get a high reflection coefficient (T 1). If the wall is made of wood, it is likely that the wood would bend a bit (less resistance), absorb more incident energy and return a weaker Transmission line (Zo) bounce. You will get a lower reflection coefficient (T < 1). Similarly if the wall was made of straw, it is more than likely that mos