1.3 Physical Phenomena in the High Frequency Domain

We will now take a deeper look at RF engineering through two examples that introduce wave propagation on transmission lines and electromagnetic radiation from antennas.

1.3.1 Electrically Short Transmission Line

As a first example we consider a simple circuit (Figure 1.3a) with a sinusoidal (monofrequent) voltage source (internal resistance RI), which is connected to a load resistor RA = RI by an electrically short transmission line. Electrically short means that the transmission length ell of the line is much shorter than the wavelength λ, that is ell ll λ. In vacuum–or approximately air–electromagnetic waves propagate with the speed of light c0.

1.1 1.1

Therefore, the free space wavelength λ0 for a frequency f yields:

1.2 1.2

In media other than vacuum the speed of light c is lower and given by

1.3 1.3

where εr is the relative permittivity and μr is the ...

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