d xformer 1.73:1 e atten 4dB f device fhx04 g clines 600 4002 90 BOARD Rectangular plot zd 50.000 5.000 10.200 1.270 25.400 19.000 Tab microstrip f GHz Fig. 2.2-1 PUFF 2.1 - blank screen (words in italics have been added for explanation). will then use these terms to show that these properties length of the tunnel because walls on either side act as are also applicable to electrical transmission systems. waveguides. Much of the explanation given in these sections will be Waves emerging directly from the sender are known as based on examples using sinusoids because they are incident waves. As your vocal cords try to propagate in- easier to understand. But this information applies equally cident waves along the tunnel, they encounter an oppo- well to digital waveforms because digital signals are sition or impedance caused by the air mass in the tunnel. composed of sinusoid components combined in a precise The impedance is determined by the physical charac- amplitude and phase manner. Therefore, it is vitally teristics of the tunnel such as its width and height and the important that you do not form the mistaken idea that manner in which it impedes air mass movement within transmission line theory only applies to analog the tunnel. This impedance is therefore called the waveforms. characteristic impedance (Zo) of the tunnel. Bends or rock protrusions along the tunnel walls cause a change in the effective dimensions of the tunnel. These 2.2.2.2 General properties of discontinuities in effective dimensions can cause minor transmission systems reflections in the signal propagation path. They also affect the characteristic impedance of the transmission Transmission systems are used to transfer energy from channel. one point to another. The energy transferred may be You should note that the walls of the tunnel do not sound power or electrical power, or digital/analog/optical take part in the main propagation of sound waves. signals or any combination 1 of the above. However, they do absorb some energy and therefore One e