Trango Broadband Access5830 - Manual (Page 70)

Management
Trango Broadband Wireless — Access5830 User Manual Rev. F page 66
Appendix D RF Primer
This section explains and simplifies many of the concepts relating to antennas and RF (Radio Frequency) technology. It is not
intended as a substitute for all the academic background that can be useful in deploying any wireless system.
General Concepts
A radio system modulates, or encodes, information to the transmitter. This modulated signal is transmitted through an antenna,
which converts the RF signal into an electromagnetic wave. The transmission medium for the electromagnetic wave is free
space (air). 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 the one originally generated by the transmitter. The signal is then demodulated back to its original
form.
Figure 9-1: Typical Radio System
RF Power Level
The dB convention is an abbreviation for decibels. It shows the relationship between two values. For example dBm is the
relation between power levels expressed in Watts. RF power levels at either the transmitter output or the receiver input is
expressed in dBm. It can also be expressed in Watts. For link budget calculations, the dBm convention is more convenient
than the Watts convention. The relation between dBm and Watts can be expressed as follows:
P
dBm
= 10 x Log (PmW/1mW)
For example:
1 Watt = 1000 mW;
P
dBm
= 10 x Log (1000mW/1mW) = 30dBm
Attenuation
Attenuation (fading) of an RF signal is defined as follows: