3rd lecture block
Main focus in the previous lectures was on propagation effects. We will first repeat the main conclusions from last lecture on electromagnetic signals, and then introduce the capacity of a system based on Shannon's theorem.
New literature:
,
where P is average power
[source: Wikipedia]
with W as system bandwidth, and in case of interference free environment, otherwise , where with as Boltzmann constant and as temperature in Kelvin.
[bits/s]
Exercises
[source: Wikipedia, Telektronikk 2002]
Source free environment and free space:
where div is a scalar function
and curl is a vector function
[Source: Wikipedia]
Taking the curl of Maxwell's equation
yields the wave equation:
with m/s
[Source: Wikipedia]
A single frequency electro (E)-magnetic (B) wave is described by
,
,
[Source: Wikipedia]
where
with the group velocity (free space = speed of light) and
the refraction index
Power received in an area in a distance R from transmitter:
thus
Develop the propagation equation, see (http://www.antenna-theory.com/basics/friis.php)
How much is 0 dB_m and 10 dB_m?
So you get:
Free space attenuation