Читать книгу Introduction To Modern Planar Transmission Lines - Anand K. Verma - Страница 127

In a communication network, several kinds of electrical signals propagate on a transmission line. The signal could be a modulated or unmodulated carrier wave, the baseband analog signal, or the digital pulses. The TEM mode transmission lines, and also various kinds of non‐TEM waveguide structures support wave propagation. The parameters defining these transmitting media could be either frequency‐independent or frequency‐dependent. The property of the medium has a significant impact on the nature of wave propagation through a medium. The wave velocity has no simple or unique meaning, like the meaning of the velocity of a particle. There are several kinds of wave velocities – phase velocity, group velocity, energy velocity, signal velocity, etc., applied to wave propagation. The significance of several types of wave velocities is inherent both in the complexity of a signal and also in the complexity of the wave supporting medium. This section focuses attention on the meaning of the phase and group velocities only. Section (3.4) demonstrates these two wave velocities as applied to several kinds of the artificial linear dispersive transmission lines.