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transmission lines and waveguides by bakshi pdf free download

Transmission Lines and Waveguides
Given a particular conductor geometry for a transmission line or waveguide, only certain patterns of electric and magnetic fields (modes) can exist for propagating waves. These modes must be solutions to the governing ifferential equation (wave equation) while satisfying the appropriate boundary conditions for the fields.

Transmission lines and waveguides may be defined as devices used to guide energy from one point to another (from a source to a load). Transmission lines can consist of a set of conductors, dielectrics or combination thereof. As we have shown using Maxwell’s equations, we can transmit energy in the form of an unguided wave (plane wave) through space. In a similar manner, Maxwell’s equations show that we can transmit energy in the form of a guided wave on a transmission line.

Transmission Line Definitions
Almost all transmission lines have a cross-sectional geometry which is constant in the direction of wave propagation along the line. This type of transmission line is called a uniform transmission line. Uniform transmission line - conductors and dielectrics maintain the same cross-sectional geometry along the transmission line in the direction of wave propagation.
Given a particular conductor geometry for a transmission line, only certain patterns of electric and magnetic fields (modes) can exist for propagating waves. These modes must be solutions to the governing differential equation (wave equation) while satisfying the appropriate boundary conditions for the fields. Transmission line mode - a distinct pattern of electric and magnetic field induced on a transmission line under source excitation. The propagating modes along the transmission line or waveguide may be classified according to which field components are present or not present in the wave. The field components in the direction of wave propagation are defined as longitudinal components while those perpendicular to the
direction of propagation are defined as transverse components. Transmission Line Mode Classifications Assuming the transmission line is oriented with its axis along the zaxis (direction of wave propagation), the modes may be classified as
1. Transverse electromagnetic (TEM) modes - the electric and magnetic fields are transverse to the direction of wave
propagation with no longitudinal components [Ez = Hz = 0]. TEM modes cannot exist on single conductor guiding structures. TEM modes are sometimes called transmission line modes since they are the dominant modes on transmission
lines. Plane waves can also be classified as TEM modes.