. pacitance is mainly dependent on the dielectric type, We will return to PUFF when we have explained the its effective permittivity, the effective cross-sectional basic terms for using it. area between conductors, the distance between the Expressions also exist for calculating the characteristic conductors and the length of the transmission line. impedance of other lines such as the strip line, coplanar When a voltage is applied, there is also a leakage cur- waveguide, slot line, etc. These are equally complicated but rent between the two conductors caused by the non- details of how to calculate them have been compiled by infinite resistance of the insulation between the two Gupta, Garg and Chadha. 6 There is also a software pro- conductors. This non-infinite resistance is usually called AppCAD which calculates these impedances. expressed in terms of a shunt resistance or parallel conductance. Therefore, transmission lines possess inherent re- sistance, inductance, capacitance and conductance. It is In the previous sections, I have produced equations which are peculiar to types of different transmission very important to realise that these properties are dis- tributed along the length of the line and that they are not lines. From now on, and unless stated otherwise, all the equations in the sections that follow apply to all types of physically lumped together. The lumped approach is only transmission lines. applicable when extremely short lengths of line are considered and as a practical line is made up of many 2.2.5 Characteristic impedance (Zo) short lengths of these lines, the lumped circuit equivalent of a transmission line would look more like that shown in from primary electrical parameters Figure 2.2-8. This is an approximation but nevertheless it is an extremely useful one because it allows engineers to A typical twin conductor type transmission line is construct and simulate the properties of transmission shown in Figure 2.2-8. Each wire conductor has lines. 6 Gupta, K.C., Garg, R. and Chadha, R., Compu