RF and Microwave Engineering: Fundamentals of Wireless Communications

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 R_I), which is connected to a load resistor R_A = R_I by an electrically short transmission line. Electrically short means that the transmission length of the line is much shorter than the wavelength λ, that is λ. In vacuum–or approximately air–electromagnetic waves propagate with the speed of light c₀.

1.1

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

1.2

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

1.3

where ε_r is the relative permittivity and μ_r is the ...