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Radio Signal Propagation
C-1
Appendix C
This section explains and simplifies many of the terms relating to antennas and RF
(Radio Frequency) systems.
The following diagram depicts a typical radio system:
Figure C-1: A Typical Radio System
A radio system transmits information to the transmitter. The information is
transmitted through an antenna that converts the RF signal into an
electromagnetic wave. The transmission medium for electromagnetic wave
propagation is free space.
The electromagnetic wave is intercepted by the receiving antenna, which converts it
back to an RF signal. Ideally, this RF signal is the same as that originally
generated by the transmitter. The original information is then demodulated back to
its original form.
RF Terms and Definitions
dB
The dB convention is an abbreviation for decibels. It shows the logarithmic
relationship (10 x Log (a/b) between two values.
RF Power Level
RF power level at either the transmitter output or the receiver input is expressed in
Watts. It can also be expressed in dBm. The relation between dBm and Watts can
be expressed as follows: