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. ...
Source type fi elds Within a small region, a field is considered to be source-type if there is, as illustrated in a net flux of the field which emerges from that region. The archetypical example of a source-type field is the electrostatic field wh...
Transformation of equations Transforming equations 2.2 and 2.4 to the frequency domain for the sinusoidal steady state gives dV dz = −(R + jωL)I = −ZI dI dz = −(G + jωC)V = −Y V where we have introduced the series impedance and shunt admittance each per unit length Z = R + jX = R + jωL Y =...
Consequences at a boundary The absence of a surface current thus reduces the boundary conditions to Et2 − Et1 = 0 (6.9) Dn2 − Dn1 = ρs (6.10) ˆn × (Ht2 −Ht1) = 0 (6.11) Bn2 − Bn1 = 0. (6.12) These are not much changed from equations 6.1 to 6.4. ...
Point of view The point of view we adopt regards matter as atomic, with internal charges and electric and magnetic dipoles capable of acting as sources of electromagnetic field, and also of being influenced by the total field set up. ...
