1. Lecture 2: Radio Wave Propagation
Anders Västberg

2. Maxwell's Equations

3. Maxwell's Equations
Electrical field lines may either start and end on charges, or are continuous
Magnetic field lines are continuous
An electric field is produced by a time-varying magnetic field
A magnetic field is produced by a time-varying electric field or by a current

4. Radiation Uniform motion Reversing direction Direction change
Osscillating periodic motion
Only accelerating charges produce radiation
[Saunders, 1999]

5. Propagation Mechanisms
The higher frequency
The more radio waves resamble the properties of light
At lower frequencies
Electrical properties of obstacles are important (but we tend to express these in terms of optical properties)
If the wave length is of the same order of magnitude (or larger), diffraction or surface effects dominate

6. Propagation mechanisms
When the dimension of the object is:
Very Large compared to the wavelength
Reflection
Larger compared to the wavelength
Diffraction
Small compared to the wavelength
Scattering
Very small compared to the wavelength
Unaffected

7. Diffraction
[Saunders, 1999]

8. Propagation between two antennas (not to scale)
No Ground Wave for Frequencies > ~2 MHz
No Ionospheric Wave for Frequencies > ~30 Mhz

9. Free Space Propagation

10. Knife edge loss

11. Effective Earth Radius
Re=8500 km=4/3R0
[Slimane]

12. Fresnel Zones