Matching If a line is terminated in its characteristic impedance (which is complex for an arbitrary lossy line), i.e. if ZL = Z0, then equation 2.60 shows that ZI = Z0 for any l i.e. the input impedance becomes independent of line length. This is an important practical property, and the line is...
Meaning of matching To give meaning to the word matching, we recall from lumped circuit theory the maximum power transfer theorem for a.c. circuits which indicates that a sinusoidal steady state source of fixed internal voltage VS and source impedance ZS will deliver maximum power to a load impe...
More complicated structures Useful tables of results of transmission line parameters for various further transmission line structures are found in Reference 1. In one edition of that book, Table 8.09 opposite page 444 and Table 1.25 opposite page 26 are of interest. ...
Objective Practical electromagnetic theory problems almost always involve material media and/or finite boundaries. To solve such problems we need firstly a knowledge of how material media react to the internal electromagnetic fields within them, and a knowledge of electromagnetic boundary condit...
Permanently polarised ferroelectrics In some dielectric media the atoms possess permanent electric dipole moments which can, once permanently aligned by the application of a strong electric field, remain in that condition unless other strong e...
Propagation vector In the above equation γ is a complex vector which we call the propagation vector. It can be decomposed into real and imaginary component vectors as γ = α + jβ (8.8) α = αxi + αyj + αzk (8.9) β = βxi + βyj + βzk. (8.10) So we see the spatial variation of E is as the product o...
Simpli fi cation of Maxwell s equations When α = 0 and the z axis is chosen to lie along the direction of β, we can assert the equations: ∂/∂x = 0, ∂/∂y = 0, and ∂/∂z = −jβ. With these restrictions Maxwell's equations in the frequency domain become jβEy = −μjωHx −jβEx = −μjωHy (8.12) 0 = −μjωH...
Single Stub Matching We will now show that, using a single shunt stub of variable length, and a section of transmission line of variable length, we can match any load impedance ZL to Z0, which for practical purposes could be the characteristic impedance of a transmission line designed to connect...
Some aspects of fi eld theory Some interesting situations then arise. It may be impossible to find an unambiguous definition for either voltage or for current. We will always have the field vectors E, D,H, and B, but it may be that unambiguous definitions for voltage and current cannot be found....
Some important structures An illustation of some important transmission line stuctures is provided in Figure 2.25. One of them, the screened pair stucture, contains more than two conductors (three in fact) and falls outside the scope of the this course. ...
