![]() In low-loss transmission lines, the following condition persists:Ī lossy transmission line consists of an appreciable value of series resistance and shunt conductance where different frequencies travel at different speeds. The lossless transmission line equation and its behavior can be approximated to low-loss transmission lines that physically exist. When the transmission line becomes lossless, the line equations are simplified and it is easier to solve compared to the general equation with all the circuit elements. Since there is no power loss, the transmission line is made of perfect conductors and the dielectric medium is also perfect. No power is lost between the source end and the load end. In lossless transmission lines, the power transmitted from the source and the power delivered at the load are equal. With series resistance and series inductance, the transmission line is lossy. When the circuit elements are R = G = 0 (3), the transmission line becomes lossless. With lumped elements R, L, G, and C, the transmission line voltage V(x) and transmission line current I(x) can be expressed with the Telegrapher’s equation as follows: ![]() The effective shunt capacitance per unit length (C) is between the transmission lines. Imperfections in the medium where transmission lines are present or fabricated generate the effective shunt-conductance per unit length (G). The effective series inductance per unit length (L) is produced by current flowing through the conductor, which is not a perfect conductor. As current through a transmission line increases, the loss associated with resistance also increases. The effective series resistance per unit length (R) is due to the loss nature of the conductor material. Circuit elements in the equivalent circuit, such as resistance, inductance, conductance, and capacitance (R, L, G, C), are referred to as primary line constants and are dependent on the geometry of the transmission line. Lossless and Lossy Transmission LinesĪny transmission line can be represented with its lumped element equivalent circuit. Let’s examine the characteristics of transmission line impedance by taking a closer look at lossless and lossy lines. Lossless transmission lines offer an excellent approximation to low-loss transmission lines and help engineers study the behavior of low-loss transmission lines from lossless transmission line equations. Lossless and lossy transmission lines are defined by different characteristics and are discussed in detail in transmission line theory. All transmission lines are lossy, and the percentage of loss varies with each case. It is physically impossible to attain a perfectly lossless transmission line in any circuit. If the transmission line is lossless, the characteristic impedance is a real number. If the transmission line is lossy, the characteristic impedance is a complex number. Lossless and lossy transmission lines have different characteristics that are dependent upon the impedance in the transmission line. ![]() When circuit elements R = G = 0, the transmission line becomes lossless. Circuit elements such as resistance, inductance, conductance, and capacitance (R, L, G, C) are referred to as primary line constants and are dependent on the geometry of the transmission line.
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