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CHAPTER13: TRANSMISSION LINES

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Tham khảo tài liệu 'chapter13: transmission lines', tài liệu phổ thông, vật lý phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 13 TRANSMISSION LINES Transmission lines are used to transmit electric energy and signals from one point to another specifically from a source to a load. This may include the connection between a transmitter and an antenna connections between computers in a network or between a hydroelectric generating plant and a substation several hundred miles away. Other familiar examples include the interconnects between components of a stereo system and the connection between a cable service provider and your television set. Examples that are less familiar include the connections between devices on a circuit board that are designed to operate at high frequencies. What all of the above examples have in common is that the devices to be connected are separated by distances on the order of a wavelength or much larger whereas in basic circuit analysis methods connections between elements are of negligible length. The latter condition enabled US for example to take for granted that the voltage across a resistor on one side of a circuit was exactly in phase with the voltage source on the other side or more generally that the time measured at the source location is precisely the same time as measured at all other points in the circuit. When distances are sufficiently large between source and receiver time delay effects become appreciable leading to the delay-induced phase differences mentioned above. In short we deal with wave phenomena on transmission lines just as we did with point-to-point energy propagation in free space or in dielectrics. The basic elements in a circuit such as resistors capacitors inductors and the connections between them are considered lumped elements if the time delay 435 I e-Text Main Menu Textbook Table of Contents 436 ENGINEERING ELECTROMAGNETICS in traversing the elements is negligible. On the other hand if the elements or interconnections are large enough it may be necessary to consider them as distributed elements. This means that their .